Electrical Impedance of Human Urine;

THE ELECTRICAL IMPEDANCE OF HUMAN URINE

by Deanne Roberts

A thesis submitted to the faculty of The University of Utah in partial fulfillment of the requirements for the degree of

Master of Science

SUPERVISORY COMMITTEE APPROVAL

of a thesis submitted by

Deanne Roberts

I have read this thesis and have found it to b degree

Jun Ph.D. Chairman. Supervisory C,)mmirrec

I have read this thesis and have found it to I:le of satisfactory quality for a master's degree.

Dale Beryl, Peters, R.N., Ph.D. �kmber. SuperVisorv Cummillce

1 have read this thesis and have found it to be of satisfactory quality for a master's degree.

/ _.(:<'). !J--(�j , I- Dale s �1:Jss, MA. E. E. Member, SI,J .rvisory Cumrnillce TH E L!:\lYE RSITY OF UTAH G RADC ATE SCHOOL

FINAL READING APPROVAL

To tht: Graduatt: Council of Tht: University of Ctah:

Deanne Roberts I have read the thesis l)f In US final form and ha\e found that (I) its format. citations. and bibliographic style are consistent and acceptable: (2) its illustrative materials including figures. tables. and charts are in place: and (3) the final manuscript is satisfactory to the Supervisory Commirtee and is ready for submission to the Graduate School.

Approved for the \Iajor Department

� �� Annette Schram Ezell, Ed. D. Chairman Dt:an

Approved for the Graduate Council ABSTRACT

Electrical impedance measurements were taken on 269 samples of human urine to compare the mean impedance of abnormal urine to the mean impedance of normal urine. Samples obtained from the popu lation of specimens sent to The University of Utah Clinical Chemistry Lab were assigned to seven different categories based on their urinalysis results. The methodology controlled for the following variables: (1) solution volume; (2) type, size and distance between electrodes; (3) frequency and amperage of the input current; and, (4) temperature of the solution. Impedance measurements were ken using a High Resolution Impedance Convertor (Transmed Scientific Model 2991), which provided 50 uA constant current at 50 kHz. The results of this study indicate that: (1) There is no significant difference in mean impedance between normal urine and urine containing higher than normal amounts of either red blood cells, white blood cells, protein, glucose, bacteria, or Pyridium; and, (2) there is a significant difference between the mean impedance of normal urine and urine that is either concentrated (specific gravity> 1.025) or dilute (specific qravity < 1.003), It was also found that impedance readings varied considerably within each cate gory. These findings suggest that factors other than those identi fied for this study may significantly inf1,uence the electrical impe dance of human urine. TABLE OF CONTENTS

Page ABSTRACT ... iv LIST OF TABLES vii LIST OF FIGURES viii

ACKNOWLEDGEMENTS ix CHAPTER I . I NTRODUCT I ON

II. REVIEW OF LITERATURE 3 Introduction ...... 3 Defining and Measuring Electrical Impedance . . 4 The Clinical Application of Electrical Impedance.. 9 The Use of Electrical Impedance to Measure Bladder Fullness ...... 10 Selected Changes in Human Urine and Their Affect on Electrical Impedance...... 11 Application of Electrical Impedance Measurement of Bladder Fullness with the Obstetric Patient 13 III. CONCEPTUAL FRAMEWORK 16

Hypotheses . . . . 1 7 Definitions 18 IV. RESEARCH DESIGN AND METHODOLOGY 21 Assumptions ...... 21 Sampl e ...... 21 Data Analysis ...... 23 Protection of Human Subjects 24 Methodology ...... 24 V. RESULTS AND DISCUSSION 28

Descriptive Data .. 28 Statistical Inference 42 CHAPTER Page Discussion ...... 58 Limitations ...... 62

VI. SUMMARY AND RECOMMENDATIONS 64

Summary ...... , . 64 Suggestions for Further Study 65 Implications for Nursing .... 67 APPENDICES A. ROUTINE URINALYSIS. 69

B. URINE IMPEDANCE BOX 71 C. ELECTRODE COATING WITH POLY HEMA, POLY (2-HYDROXYETHYL METHACRYLATE) (HYDRO-MED SC I ENCES, INC.) ...... 74 D. HIGH RESOLUTION IMPEDANCE CONVERTER 2991 . . . 76 E. HEATHKIT DECADE RESISTANCE BOX MODEL EU-30A 80 F. HEATHKIT MODEL IM-28 VACUUM TUBE VOLTMETER. 82 G. UNITED SYSTEMS CORPORATION DIGITEC HT SERIES MODEL 5810. 84 H. BACHARACH HUMIDITY--TEMPERATURE INDICATOR MODEL 22-7056. 86 I. CALIBRATION OF THE HIGH RESOLUTION IMPEDANCE CONVERTER.. 88 J. DETAILED METHODOLOGY FOR THE MEASUREMENT OF ELECTRICAL IMPEDANCE ...... 91

K. SAMPLE DATA COLLECTION SHEET . 96 BIBLIOGRAPHY . 98 VITA . . . . 103

vi LIST OF TABLES

Table Page

1. Sample Distribution of Age and Sex by Category .. 29 2. Category Comparison of Sample, Room, and Container Temperatures ...... 30 3. Specific Gravity by Category. 32

4. Impedance Readings by Category . 33 5. Pearson Product Moment Correlation Coefficients 44 6. Correlation of Dependent Variable to Category of Urine Using Eta Correlation .... 46 7. Natural Log Transformation of Original Data 51 8. Kruskal-Wallis Test 52

9. Homogeneous Subsets from Scheffe's Test 53 10. test for Comparison of Means by Category. 56 11. Comparison of Mean Impedance, Sample Temperature, and Specific Gravity by Category ...... 59 LIST OF FIGURES

Fi gure Page 1 , Dot Diagram of Impedance Readings Category A . 35 2. Dot Diagram of Impedance Readings Category B . 36 3. Dot Diagram of Impedance Readings Category C . 37 4. Dot Diagram of Impedance Readings Category o . 38 5. Dot Diagram of Impedance Readings Category E . 39

6. Dot Diagram of Impedance Readings Category F . 40 7. Dot Diagram of Impedance Readings Category G . 41 ACKNOWLEDGEr1ENTS

The author gratefully acknowledges the following individuals who contributed their own special talents toward the completion of this study. I am especially indebted to my Supervisory Committee members: June C. Abbey, Beryl M. Peters, and Stanley D. Moss. I would also like to sincerely thank Liz Close, Patty Young, Mike Lingwall, and Collette Rush for their knowledgeable consultation and perseverance in collecting data; Paul Brown and John Miller (University of Utah Clinical Chemistry Lab); the staff at The Maternal and Infant Care Project (Salt Lake City) for their advice and assis tance in obtaining urine specimens; Jim Triplett for his advice, editing skill and unending support in the final preparation of the manuscript and Lia Roberts, my daughter, for her ability to endure. CHAPTER I

INTRODUCTION

The relationship between selected abnormal changes in human urine and the electrical impedance of the urine was examined in this study. The research was conducted in conjunction with that of Dr. June C. Abbey, whose DHEW Division of Nursing Grant, No. 1 ROl NU 00651 entitled, IIImpedance Measurement of Urinary Bladder Fullness," had the general goal of determining II ••• if electrical impedance can be used as a noninvasive monitoring tool to assess urinary bladder fullness in patients who have a malfunction that interferes with the sensation of fullness and, consequently, the act of voiding" (Abbey,

1978, p. 20). The development of such a device would impact a variety of nursing care situations. The sensation of bladder fullness normally associated with the urge to void can be lost following traumatic nerve damage, gen eral or regional anesthesia, or trauma to the genito-urinary tract. Similarly, enuretic children do not seem to be consciously aware of these sensations. In each situation, the patient is subjected either to the embarrassment of loss of control or possibly to an unnecessary catheterization and the resulting potential for concomitant urinary tract infection. Concrete, reliable parameters for determining bladder fullness are not readily available, thus the nurse is often 2 called upon to make an unaided decision as to whether catheteriza tion is necessary_ To measure bladder fullness using electrical impedance re quires a reliable instrument that is easy to use, safe, preferably compact, and that takes into account all significant variables. However, no matter what instrument is selected, one variable that cannot be controlled for is the constitution of human urine. If, for example, changes in specific gravity or an increase in the con centration of white blood cells alter impedance readings, then these changes must be taken into account when determining bladder fullness with such a device. This study was directed toward identifying what specific changes in human urine composition may significantly effect its electrical impedance. CHAPTER II

REVIEW OF LITERATURE

Introduction The use of impedance plethysmography to measure fluid volume and flow changes has received considerable attention since the early 1940 1 s, when J. Nyboer and his associates (Nyboer, Bagro, Barrett & Halsey, 1940) first applied the technique to biological systems. Due to the diverse and extensive literature available and the personal interests of this researcher. this review was limited to the follow ing topics: (1) defining and measuring impedance, (2) clinical ap plication of electrical impedance measurements, (3) impedance studies that have direct application to measuring urinary bladder fullness, (4) a conceptual guide to anticipated changes in impedance relating to specific constituents of urine, and (5) the potential use of an impedance device to measure bladder fullness with the obstetric pa tient. While reliable, widely accepted means exist for mechanically measuring volume, the same is not true for volume measurements utiliz ing electrical techniques. However, it is the measurement using electrical means which offers the best potential for quantifying volumes not readily accessible to physical measurement. Electrical impedance is one means for accomplishing this. 4 Defining and Measuring Electrical Impedance A review of some fundamental concepts in electricity may facilitate the understanding of impedance and how it can be used in measuring biological volumes. Conductors are those materials that pass electric current be cause they contain a relatively large number of free electrons. Insulators, or nonconductors, have relatively few free electrons and, consequently, do not easily pass electric current. Voltage is de fined as lithe difference in charge or potential energy existing be tween two points due to an unbalanced electron population at these two points" (Karse1is, 1973, p. 5), The unit of measure of voltage is the volt. Current flow refers to the rate of movement of free electrons through a conductor and is measured in amperes. Resistance is opposition to current flow and is inversely proportional to the number of free electrons. The more free electrons available to carry the current, the less the resistance. The unit of measure for resistance is the ohm. Between voltage, current, and resistance, there exists a relationship first discovered by George Ohm, a German physicist, who published his findings in 1827. He stated what is now known as Ohm's Law: liThe current in an electrical conductor is directly propor tional to the voltage between the ends of the conductor and in versely proportional to the resistance ll (Karselis, 1973, p. 12). Two basic types of current flow, alternating and direct, are differentiated by polarity (the direction of flow), Direct current (DC) is such that polarity remains fixed with relation to time 5 (Karselis, 1973, p. 8). Alternating sinusodial current (AC) reverses polarity (positive + negative) periodicially and constantly changes in magnitude (Karselis, 1973, p. 8). Most alternating cur rent waveforms are repeated over and over again. The number of cycles per second of a particular waveform is called its frequency and is measured in hertz. Direct current has a magnetic field around the conductor, which is stationary, when the magnitude is constant, and this field does not vary in size or intensity. As a result, resistance provides the only opposition to current flow. In an alternating current (AC) circuit resistance is additionally offered by the reactive components, inductors and capacitors, of the circuit which vary with the frequency of the applied current. Inductors and capacitors do not dissipate electrical energy in the fonn of heat but alternately store energy and then deliver it back to the circuit (Karselis, 1973, p. 12). The total opposition to current flow in an AC circuit is thus a func tion of the complex relationship between inductive reactance, capaci tive reactance, and resistance. This is collectively termed impedance and given the symbol t:. Impedance can be defined in terms of voltage and current where ~ = E/I (l = impedance, E = voltage, and I = current). Sub stituting impedance for resistance in Ohm's Law, which states V = IR

(V = voltage, I = current, and R = resistance), and holding I (cur rent) constant, the voltage measurement is then directly related to the impedance of the part being measured. Impedance is measured in ohms. 6 The measurement of electrical impedance in the human body is possible because biological tissues are moderately good conductors of alternating current, and these tissues show a measurable resis tance to the passage of such a current. Biological tissues are con ductors of alternating current because: (1) tissue cells consist of ions and are surrounded by ions dissolved in water, (2) ions carry small electrical charges, and (3) ions will migrate or move when exposed to an electrical charge (Cooley & Lehr, 1972). A relatively simple, noninvasive technique to measure impe dance in humans involves the external attachment of two or four elec trodes and the passage of constant current from the generator e1ec trode(s) to the sensor electrode(s). In many designs the same two electrodes are used both as generators and sensors. For reasons of stability and insensitivity to motion and to decrease interface prob lems at the electrode-skin junction, four separate electrodes are considered preferable when doing measurements on humans or ani mals (Geddes & Hoff, 1964; Nyboer, 1970). Two electrode configura tions are called bipolar and four electrode configurations tetrapo1ar. Since this study focused on impedance readings of an ionic solution, urine, outside of the human body, the bipolar system of electrodes was selected. Electrodes placed in an ionic solution do not have the interface problems associated with electrodes to be placed on the skin; therefore, tetrapolar configurations do not have a significant advantage over bipolar systems as suggested in measure ments made on the human body. The placement of a metallic electrode in an aqueous solution 7 creates a situation where metal ions tend to enter into solution and ions in the solution tend to combine with the electrode result ing in a charge distribution at the electrode-electrolyte interface. This electrode polarization has all the characteristics of a capaci tor and thus can alter impedance measurements (Geddes, 1972). The silver-silver chloride electrode has been shown to be the most stable of the easily constructed, relatively inexpensive electrodes, thus the use of uniformly sized and shaped Ag-Ag/Cl electrodes helps to minimize the effects of polarization on impedance measurement (Ged des, 1972). In addition, there are other factors which affect impedance readings. Nyboer (1970) has demonstrated that increasing the dis tance between electrodes in the bipolar system increases the resis tance, thus the accuracy of impedance readings will be enhanced by a system that provides control over the distance between electrodes. Impedance is also temperature dependent (Geddes & Sadler, 1973; Ur & Brown, 1975). An increase in temperature increases the movement of the ions in solution and decreases the impedance. Ur and Brown (1975) maintain that temperature variation affects the impedance by about 2% per degree centigrade. However, the studies relating to impedance measurements of cardiac output (Kubicek, Patterson & Witsoe, 1968), intrathoracic fluid changes (Pomerantz, Delgado & Eisman, 1970), and deep vein thrombosis (Mu11ick, Wheeler & Songster, 1970) make no mention of attempts to control or quantify the effects of temperature on the measurements obtained. Obviously, it is not possible to control the temperature of human subjects, but 8 the work of Geddes and Sadler (1973) on blood and that of Ur and Brown (1975) on bacteriuria validate the need to control this vari able. This is especially important when measuring ionic solutions in which temperature can be controlled. Three other important factors that will influence measure ment of electrical impedance are the frequency of the input current, the volume of the ionic solution being measured, and the amperes of current flowing through the electrodes (Geddes, 1972; Karse1is, 1973; Nyboer, 1970; Schanne & Ruiz-Cerretti, 1978). If impedance measurements are going to be performed on human subjects, frequency and amperes of current are important from a safety standpoint. Geddes et a1. (1968) conducted experiments on humans and dogs to determine what level of alternating current has measure able physiological effects. They focused on subject sensation, vagal stimulation, and ventricular fibrillation. The results of their study indicate that when frequency is increased (1) the threshold for sensation is increased, (2) the incidence of vagal slowing of the heart is decreased, and (3) the current required to produce ventricular fibrillation is increased. They recommend that current higher than 5 kHz in frequency be used when doing impedance studies on human subjects (Geddes et al., 1968, p. 295). These results establish that the lower the amperage of current desired to be used in the study, the higher the frequency should be in order to ensure that the subject does not experience sensation. In addition, high frequency and low current protect against vagal stimulation and ventricular fibrillation. 9 Nyboer (1970) has shown that the reactive components of an alternating circuit are minimized between 75 kHz and 100 kHz and, therefore, the readings obtained are the closest to the pure resis tance of the circuit. Because of this and safety concerns, most impedance measurements taken on humans utilize equipment operating in the 50 kHz to 250 kHz range (Nyboer, 1970, p. 415). The equip ment designed for the impedance measurements on human subjects was designed to deliver 50 ~A constant current at 50 kHz.

The Clinical Application of Electrical Impedance While use of impedance to measure physiologic variables and more specifically IIbiovo1umes" is well-documented (Nyboer, 1970), there has been no widespread acceptance of impedance techniques (Hill, Jansen & Fling, 1967). The major accomplishments in the clinical application of impedance have been in measuring cardiac output (stroke volume) (Kubicek et al., 1968), and intrathoracic fluid changes (Pomerantz et a1., 1970), in diagnosing deep vein thrombosis (Mul1ick et a 1., 1970), and in the detecti on of bacteri uri a (Cady, 1975; Ur & Brown, 1975). Inability to replicate results and the frequent oc currences of false negative results are major blocks to the acceptance of some of these findings (Steer, 1973). This led one author to state that too much "artistryll is required in attempts to establish the value of impedance (Cooley & Lehr, 1972). Others maintain that no consistent explanation for impedance changes exists (Brown, Pryse & Baunber, 1975). Brown et a1. (1975) present two hypotheses to explain impedance changes of blood: 10 a) Moving blood has a different impedance than static blood because the blood cells are not spherically symme trical and can align themselves in the direction of flow; b) The volume of blood in a given segment of limb will fluctuate with blood flow and so give rise to impedance changes. (p. 675) Their work supports the second hypothesis and most researchers have proceeded under this assumption. The work of Ur and Brown (1975), and Cady (1975), on monitoring bacterial activity using impedance measurements under controlled laboratory conditions, has been validated by other researchers (Throm et a1., 1977; Zafari & Martin, 1977). The BACTOMETER 32 micro- bia1 monitoring system (Bactomatic, Inc., Palo Alto, California) was developed from these studies and has been shown to be 95.8% accurate when compared to conventional microbiological procedures to measure the presence of bacteria in urine (Cady et al., 1978, p. 275). This particular instrument utilizes a bridge circuit containing two measuring cells matched in physical dimensions. Comparative measurements are taken simultaneously in order to cancel out the noise and drift effects caused by evaporation of water, temperature variations, and electrochemical reactions.

The Use of Electrical Impedance to Measure Bladder Fullness Relatively few studies have been published regarding the use of instruments to measure bladder fullness. In 1971, Waltz, Timm, and Bradley measured bladder volume by using electrodes that were surgically implanted on dogs. While they were able to correlate bladder volume with resistance measurements, the invasive nature of 11 the technique does not lend itself to experimentation on human sub j ects. Denniston and Baker (1975) demonstrated a linear relationship between electrical impedance and the volume of urine present during the infusion or withdrawal of urine into the bladders of anesthetized dogs. In other research, Doyle and Hill (1975) found that impedance measurement was unsatisfactory for determining residual urine in conscious man. Unfortunately, their methodology called for the attachment of a perineal electrode which was subject to excess moisture and easy detachment. The exploratory, and as yet, unpub lished work of Abbey demonstrated that impedance decreased with an increase in bladder volume when urine, lactated ringers and sodium chloride were instilled into the bladder of anesthetized, paraplegic dogs. The difference in impedance readings from one solution to an other suggests that the constitution of the fluid may indeed alter its electrical impedance.

Selected Changes in Human Urine and Their Effect on Electrical Impedance No published research material was identified that was di rected to the specific problem of how changes in human urine influence its impedance readings. Nyboer (1970) recognized that mean resisti vity varies from tissue to tissue, and he demonstrated that "urine" has low resistivity compared to tissues such as blood, fat, gray matter. Geddes and Sadler (1973) investigated a similar problem by measuring the resistivity of blood from a variety of species in 12 relation to hematocrit. All tests were conducted at 37° centigrade and 25 kHz. In all cases, they found that resistivity increased with increasing hematocrit. Urine can be characterized as a biological tissue and, there fore, as a conductor of electricity. Reasonable probability exists that resistance to the passage of an electrical current decreases as the volume (and thus ion content) of urine increases, and instrumenta tion capable of measuring small changes in the electrical resistance of urine will allow indirect assessment of changes in urine volume. Since urine reflects body metabolism, its composition is not static. The question then arises, can changes in electrical impedance be cor related with changes in urine composition? In a compilation not considered complete, Free and Free (1975) listed 200 constituents of urine. While many of these constituents can be identified and measured, such tests are not readily available. At the same time, the use and significance of routine urinalysis for measuring the major constituents of urine relating to the diagnosis of disease conditions has been well established. Routine urinalysis measures eight constituents macroscopically and four constituents microscopically, and it is toward these groupings that this research was conducted. Red blood cells, white blood cells, and bacteria are pri marily proteins and while proteins have some ionic qualities, these qualities are relatively minute. Glucose is basically inert and has little potential for conduction of current. It was theorized then that abnormal amounts of red blood cells, white blood cells, bacteria, 13 protein and glucose would not significantly alter electrical imped ance. Concentration, as measured by specific gravity, is a reflec tion of ion content. An increased specific gravity reflects increased ion content and a decreased specific gravity reflects decreased ion content. It was postulated that changes in concentration would significantly alter electrical impedance. The design of this study considers one other abnormal consti tuent of urine, Pyridium (phenazopyridine Hel). This medication exerts analgesic or local anesthetic action on the urinary tract mucosa and is frequently used to decrease the discomfort of urinary tract infection. Pyridium is rapidly excreted by the kidneys with as much as 65% of an oral dose being excreted in the urine (American Society of Hospital Pharmacists, 1978, sec. 84:04). Since the concen tration of Pyridium in urine is so high, its effects on impedance could be significant.

Application of Electrical Impedance Measurement of Bladder Fullness with the Obstetric Patient The urinary tract in pregnant women undergoes several ana tomica.l changes that predispose these women to urinary retention and urinary tract infections. Early in pregnancy the capacity of the bladder is reduced due to space occupied by the enlarging uterus. Once the uterus rises out of the pelvic cavity the process is re versed, only to recur toward the end of pregnancy when the fetal parts descend into the pelvic cavity (Goggin, 1973; Hytten & Leitch, 14 1971). During the latter phase of the first stage of labor, women frequently are unable to distinguish the urge to void from other sensations or perineal pressure. At the same time, a full bladder can impede the descent of the fetus through the birth canal. The nurse is frequently expected to determine bladder ful1- ness--a determination based on intravenous and oral intake and urinary output with consideration of the increased sensible loss of fluids that accompanies the work of labor. While no literature has been identified that documents the incidence of unnecessary catheteriza tions on pregnant women, this is an area of concern for nursing. Other factors that contribute to the increased incidence of urinary tract infections are compression of the ureters by the en larging uterus, decreased peristalsis, and increased dilatation of the ureters in response to the hormonal changes in pregnancy (Goggin, 1973; Hytten & Leitch, 1971), and the high nutrient content of urine in pregnancy (Danforth, 1977; Goggin, 1973; Hytten & Leitch, 1971). It has been shown repeatedly that during the reproductive period women have a 3-7% greater chance of developing urinary tract infections. Of these, 25% will develop acute pyelitis (Goggin, 1973, p. 23). Acute pyelitis is associated with an increased risk of fetal prematurity, neonatal mortality, and stillbirth, along with maternal hypertension, toxemia, and anemia (Danforth, 1977). The physiology of urinary retention in the postpartum period is also well documented. It is known that following delivery the urinary tract does not immediately return to its nonpregnant state; rather, its functional ability is directly controlled by several 15 factors. Due to decreased intra-abdominal pressure and relaxed, stretched abdominal muscles~ the bladder capacity is increased (Be1- hea, 1973; Reeder, Fitzpatrick & Eastman, 1976). Normal voiding in the postpartum period amounts to 500-1000 m1, which is two to three times the normal for a nonpregnant patient (Reeder et a1., 1976). A marked increase in the daily output of urine (diuresis) also occurs due to hormonal changes (Sims & Krantz, 1958). At the same time, normal voiding may be difficult due to: (1) reflex spasm of the urethra secondary to perineal pain, (2) desensitization secondary to regional anesthesia (Pritchard & Macdonald, 1976), or (3) trauma to the bladder and/or urethra during delivery. Bladder distention in the postpartum period may lead to complications because a bladder that is distended takes longer to regain its tone and is easily in fected. According to Be1hea (1973), a distended bladder is one of the causes of postpartum hemorrhage. The recognition and management of bladder distention in the postpartum patient is not without controversy since the caretaker is expected to weigh the possibility of complications from urinary dis tention against the increased risk of introducing infection via catheterization (Brumfitt, Davies & Rossor, 1961; Castle, 1974; Gari baldie, Buke, Dickman & Smith, 1974; Malinowski, 1978). An external, noninvasive device to measure bladder fullness would provide im portant information as well as generate the need for developing new parameters to establish when catheterization is indicated in ante partum and postpartum patients. CHAPTER I I I

CONCEPTUAL FRAMEWORK

When patients lose their normal ability to sense bladder full ness they cannot detenline when to void and often must be catheter ized. While a full bladder must be emptied to avoid stagnation of urine and reflux into the kidneys, catheterization itself carries the risk of introducing infectious organisms into the genito-urinary sys tem and, therefore, should not be done more often than is absolutely necessary. Many patients who have permanently lost the sensations of bladder fullness are often socially and emotionally isolated due to their lack of ability to determine when the bladder needs to be emptied. One possible solution to these problems would be to use elec trical impedance as a noninvasive method to monitor bladder fullness. Reliable instrumentation is available to measure electrical impedance on humans under laboratory conditions. The use of impedence in the clinical setting on human subjects is complicated by the introduction of variables that are sometimes difficult to control such as: skin electrode interface, a variety of tissue types and body temperature changes. However, most of the critical variables in impedance measurement can be controlled or their effects minimized by proper design of the impedance measuring instrument. One variable that will not be within the control of an 17 impedance device is the composition of human urine. Urine is a com plex ionic solution and its composition changes rather rapidly. If changes in the composition of human urine significantly alter its electrical impedance, then these changes must be accounted for when using electrical impedance to determine bladder fullness. For this study, seven broad categories of human urine as de fined and measured by routine urinalysis were considered. Each category was analyzed to determine if its mean impedance was signifi cantly different than the mean impedance of normal urine. Urine that contained abnormal amounts of red blood cells, white blood cells, bacteria, protein, glucose, and Pyridium, or was abnormally dilute or concentrated, was compared to normal urine. With the impedance of a solution related to its ion content, it was theorized that only the extremes in specific gravity would significantly alter the impedance of urine. While red blood cells, white blood cells, glucose, protein, and bacteria have the potential for some ionic activity, especially when exposed to electrical cur rent, it was predicted that these ionic characteristics would not be significant enough to alter electrical impedance measurements.

Hypotheses In order to set up consistent null hypotheses to compare the means of each category, all research hypotheses predicted a signifi cant relationship between the variables. All hypotheses were tested at the £ 2 0.05 level of significance. 18 10 The electrical impedance of urine containing an abnormally high count of red blood cells, and/or white blood cells and/or bacteria will be signi ficantly different from that of normal urine. 2. The electrical impedance of concentrated urine will be significantly different from that of normal urine. 3. The electrical impedance of dilute urine will be significantly different from that of normal urine. 4. The electrical impedance of glycosuric urine will be significantly different from that of normal urine. 5. The electrical impedance of urine containing Pyri dium (phenazopyridine Hel) will be significantly different from that of normal urine. 6. The electrical impedance of urine containing ab normally high amounts of protein will be signifi cantly different from that of normal urine.

Definitions The formation of urine takes place in the kidney_ Two major kidney functions are the excretion of most of the end products of bodily metabolism and the control of the concentration of most of the constituents of the body fluids (Guyton, 1976). Voided urine specimens can, therefore, be a reflection of body metabolism, kidney function/dysfunction, and the condition of the ureters, bladder, and urethra. Many substances can be found in urine which are indicators of potential health problems. For instance, the presence of red blood cells, white blood cells, or bacteria in the urine is not a frequent finding but is indicative of some genlto-urinary disorder that should be thoroughly investigated (Kark, Lawrence, Pollack, Pirani, Muehrcke 19 & Silva, 1963). A primary indicator of diabetes mellitus is gly cosuria. This is urine containing a higher than normal content of glucose. Glycosuria occurs when blood concentrations of glucose exceed the renal threshold for glucose and the excess spills into the urine (Kark et al., 1963). These are not the only possible variations found in human urine. Excessive protein in urine as well as extreme variations in urine concentration can be indicative of systemic or renal disease and can be identified by routine urinalysis. The following are category definitions as established for this study: Normal human urine: For the purposes of this study, normal human urine was defined as that urine whose analysis fell within the range of normal as determined by The University of Utah Clinical Chemistry Laboratory (see Appendix A). Abnormal red blood cell count: Red blood cell count equal to or greater than five per average of ten high-power fields as de termined by The University of Utah Clinical Chemistry Laboratory. Abnormal white blood cell count: White blood cell count equal to or greater than five per average of ten high-power fields as determined by The University of Utah Clinical Chemistry Laboratory, Bacteriuria: The presence of any bacteria as determined microscopically by The University of Utah Clinical Chemistry Laboratory. Concentration urine: Urine with a specific gravity equal to or greater than 1.025 as determined by The University of Utah Clini cal Chemistry Laboratory_ 20 Dilute urine: Urine with a specific gravity equal to or less than 1.003 as determined by The University of Utah Clinical Chemis try Laboratory. Glycosuria: Urine containing glucose equal to or greater than 1+ as determined by The University of Utah Clinical Chemistry Laboratory. Urine containing Pyridium: Urine specimens obtained from people known to have taken Pyridium within the past 24 hours. Urine containing protein equal to or greater than 1+ as determined by The University of Utah Clinical Chemistry Laboratory. CHAPTER IV

RESEARCH DESIGN AND METHODOLOGY

The aim of this study was to identify the relationship be tween selected categories of human urine and the electrical impedance of that urine. At the time this study was conducted no published work was identified that had explored any categories of urine other than normal.

Assumptions The following assumptions were inherent in this research design: 1. The routine urinalysis, as determined by the Clini cal Chemistry Laboratory at The University of Utah Medical Center was of consistent qual ity and reliability. 2. Urine that is refrigerated at 4-5 0 centigrade for

up to 24 hours would not significantly change its ionic composition (Free & Free, 1975). 3. Electrical impedance is a reflection of presence of ions. Changes in electrical impedance are a result of changes in ion composition and concentration.

Sample Two hundred sixty-nine urine specimens were obtained from the population of urine specimens sent to The University of Utah 22 Clinical Chemistry Laboratory. All urine specimens sent to the lab for routine urinalysis were acceptable for use in this study except for the following: 1. Urine with specific gravity greater than 1.040. 2. Urine that was obtained greater than 24 hours prior to testing in the College of Nursing Bioinstrumentation Lab. 3. Urine not refrigerated upon completion of urina1y- sis. 4. Urine specimens not properly labeled for identifi cation purposes and as to date and time of refrigeration. 5. Urine specimens with less than 20cc volume.

The rationale for these exclusions was based upon the follow ing factors: (a) The kidney is not capable of concentrating urine greater than 1.040, thus specimens with this specific gravity are obtained only from patients who have ingested X-ray contrast dyes (example: Hypak); (b) urine that has stood for greater than two hours at room temperature or 24 hours at 4-5 0 centigrade will be significantly altered in composition; (c) the matching of urinaly sis results with the specimen from which it was taken was imperative; and (d) to insure control of volume all impedance readings were taken on 20cc of urine. The urine specimens were assigned to categories according to urinalysis results. The method of urinalysis as performed by The Uni versity of Utah Clinical Chemistry Laboratory and normal values are 23 found in Appendix A. Urine specimens were obtained for each of the following categories: Category A: All urinalysis results within normal limits. Category B: Red blood cells and/or white blood cells and/or bacteria equal to or greater than five per average of ten high-power fields with or without elevated protein with all other values within normal limits. Category C: Concentrated urine, i.e., urine with speci fic gravity equal to or greater than 1.025 with all other values within normal limits. Category D: Dilute urine, i.e., urine with specific gravity equal to or less than 1.003 with all other values within normal limits. Category E: G1ycosuria, i.e., urine glucose equal to or greater than 1+ with all other values within normal limits. Category F: Urine from humans known to have taken Pyridium within the past 24 hours. Category G: Proteinuria, i.e., urine protein equal to or greater than 1+ with all other values within normal limits.

No attempt was made to control the number of samples obtained from male vs. female subjects.

Data Analysis Analysis of the urine impedance readings was carried out to 24 determine if a statistically significant (£ ~ 0.05) difference ex isted between the mean impedance readings of Category A, normal urine, and the mean impedance of each of the other categories of urine. The analysis also explored the correlation between sample temperature, specific gravity, and mean impedance readings. Further tests were conducted to determine if the categories of urine were distinguished by their impedance readings and to determine if any potential category subsets existed.

Protection of Human Subjects Since direct participation of human subjects was not required and all specimens were identified by number only, The University of Utah Review Committee for Research with Human Subjects approved this study as having no risk for human subjects.

Methodology Urine Specimens Urine specimens with their corresponding urinalysis results that met the criteria for inclusion in the study were obtained from The University of Utah Clinical Chemistry Laboratory. To decrease the chance of any alteration in the composition of the urine, these specimens were: (1) tested either within two hours after being kept at room temperature, or (2) with 24 hours after being stored at 4-5 0 centigrade. Preliminary testing revealed that specimens not stabil ized within ~2° centigrade of room temperature were subject to fluctu ations in temperature resulting from convective and conductive heat gain or loss. Specimens undergoing temperature fluctuations did not 25 give consistent impedance readings over the required six to eight minute period. To control for heat loss or gain by conduction, all speci mens were tested after they reached a temperature of ~2° centigrade of room temperature. Refrigerated specimens were brought to the proper temperature through use of a circulating water bath at 24 0 centigrade. To minimize air flow around the urine impedance box, and thus control for heat loss or gain through convection, the urine impedance box was surrounded by styrofoam chips prior to and during testing.

Urine Impedance Box The urine impedance box and electrodes, as designed by Michael G. Lingwall, were constructed entirely of untinted plexiglass (see Appendix B). The box was assembled using waterproof glues and resins that did not react with the acidic and basic conditions that are normally associated with urine. The electrode plates were specifi cally designed and treated to minimize the effects of polarization and to maintain a known distance between electrodes. Monitrode M Ag-Ag/Cl electrodes (size lcm.) were permanently attached to the pair of plexiglass electrode plates. These plates were coated one time per week with Poly Hema (see Appendix C). Initially, several plates were used but this did not provide the needed distance precision between electrodes, thus the study was completed using only one set of electrode plates. 26 Instruments A High Resolution Impedance Convertor (Transmed Scientific Model 2991) (see Appendix D) provided a transducer capable of measur ing a source impedance. The circuit is a basic Wheatstone Bridge utilizing two identical amplifier systems to supply a constant cur rent at 50 kHz frequency and 50 ~Amps. The urine impedance box was attached to one of the blocks referred to as the "subject chain" and a decade box (see Appendix E) was attached to the other block referred to as the II reference chain. II A resistance reading that balanced the Heathkit voltmeter at eight ohms and the 50 kHz oscil lator fine tune at 40 ohms was dialed into the decade box. The addi tion of the Heathkit Vacuum Tube Voltmeter (see Appendix F) increased the precision of the readings to 0.1 ohms. Specimen and container temperatures were monitored using a United Systems Corporation Digitec Thermometer (Model 5810) (see Ap pendix G) which is accurate to ~ 0.3 0 centigrade and has a response time of 41 seconds. In order to monitor the specimen temperature within l-2mm of the electrodes without touching the sides of the container nor passing between the electrodes, a Yellow Springs Instrument Temperature Probe, #702, was suspended in the urine from a ringstand. Probe #709A was taped to the outside of the urine bottle to monitor container temperature. Room temperature was determined by use of a Bacharach Humidity-Temperature Indicator (Model 22-7056) (see Appendix H). These temperatures were measured in degrees Fahrenheit, then were converted to degrees centigrade using standard tables from The 27 Handbook of Chemistry and Physics (Weast, 1968).

Impedance Measurements With the instruments calibrated and the specimens at the proper temperature, 20 cubic-centimeters of urine was placed in the urine impedance box. After allowing five minutes to elapse ensuring a stable urine temperature, three impedance readings were taken. A difference of more than 0.1 ohms between readings required that the entire procedure be repeated to rule out operator error. Between the testing of urine specimens, the urine impedance box and electrode plates were rinsed with de-ionized, filtered water and thoroughly dried. The Impedance Convertor was calibrated before and after each trial (see Appendix I). The Digitec Thermometer was also zeroed before and after each trial and was calibrated one time per week. For the exact protocol for collection of data see Appendix J. CHAPTER V

RESULTS AND DISCUSSION

Descriptive Data A total of 269 samples of urine was collected for the seven categories established by the study. The number of samples in each category ranged from 27 to 53. The data included specimens from 111 males, 144 females, and 14 individuals with no sex information report ed. The age of the donors ranged from 1 year to 86 years with the mean age of 42.8 years. For a complete breakdown of age and sex by category, see Table 1. The table reveals that women contributed fewer specimens in the normal Category (A) and more specimens in the other six categories than men. Also, no men were identified as having taken Pyridium (Category F). To date, no evidence exists that age or sex have any effect on impedance, thus these variables were not controlled for when obtaining specimens. However, through random selection, both of these variables were evenly distributed in the sample. Table 2 summarizes the descriptive statistics of each cate gory relating to room temperature, sample temperature, and container temperature. While it is well established that impedance is tempera ture dependent (Geddes & Sadler, 1974; Ur & Brown, 1975), laboratory conditions did not allow for strict controls over room, container, and specimen temperature. The research methodology required that specimen temperature be within + 2° centigrade of room temperature Table 1

e U1S ion of Age and Sex by Category

of of No Average a Sex Category Female Listed e Size Age (Years)

A 18 28 5 51 43.5 8 84

B 32 19 2 53 47.0 18 - 86

C 6 21 3 30 34.8 5 - 58

D 25 11 2 38 44.0 - 86

E 15 2 37 58.4 18 - 84

F 27 o o .5 - 37

G 16 17 o 33 .3 18 -

Note. Total sample size 269.

aCategories of urine: A = normal; B = elevated RBC1s, WBC1s, and/or bacteria; C concentrated; D = dilute; E = glycosuric; F dium; G proteinuric. Table 2

Category Comparison of Sample, Room, and Container Temperatures

a Cateqory Sample Size Sample Temperature (OC) Room Teillperature (OC) Container Temperature (OC) .-.-~---~.------"-.------""---- ._-_._------~_~_J:1i!)illlulII __ l1ax imulIl X SO Minimum MaxilllUIIl X SO Minimum Maxilllum

A 51 24.6 1.620 22.9 27.9 25.5 1. BO 23.9 28.9 24.4 1.653 22.6 28.3

B 53 24.0 0.956 22.8 27 .2 24.8 0.97 23.9 2B.9 23.8 1.003 22.2 26.9

C 30 24.1 1.202 22.4 28.2 25. 1 1. 33 23.9 28.9 24.1 1. 317 22.7 28.5

D 38 23.8 0.686 22.9 25.8 24.6 0.54 23.9 26. 1 23.7 0.815 22,1 25.4

E 37 24.0 0.958 22. 1 26.3 24.8 0.69 23.3 26.7 23.8 0.913 21.8 25.7

F 27 24.4 0.997 22.0 26. 1 24.9 0.56 23.9 26.1 23.9 0.679 22.8 25. 1

G 33 24.1 1. 165 21. 1 27 .1 25. 1 0.99 23.9 27.2 24.1 1.867 21.5 27.3

aCategories of urine: A = normal, B = elevated RBC's, WBC,and/or bacteria; C :;::concentrated; 0:;:: dilute; E = glycosuric; F :: Pyridium; G = proteinuric

w o 31 prior to testing. A comparison of mean room temperatures and mean specimen temperatures show that these controls were maintained within

~ 1° centigrade and that no extreme variations exist. A comparison of mean room temperatures and mean container temperatures also re vealed that in all categories this variable did not fluctuate by more than! 1° centigrade and that no extreme temperatures were present. Table 3 summarizes the specific gravity readings by category. As described in the methodology, no specific gravity readings were taken on specimens in Category F (patients taking Pyridium). Specific gravity readings for Categories A, B, E, and G ranged from 1.003 to 1.025. Specific gravity for Category C, concentrated urine, ranged from 1.025 - 1.037, and for Category 0, dilute urine, specific gravity ranged from 1.001 - 1.003. These ranges were expected as they were controlled for in the study. Looking at the range and standard deviation of specific gravity in each category, it appears that within each category there was a broad range of specific gravities for the urine samples taken. The only exception to this was Category 0, dilute urine, which had a range of 1.001 - 1.003. Even though the chemical condition of the urine, as defined by category, has an effect on its specific gravity many other physiological variables also affect the specific gravity of urine. It could, therefore, be expected that the samples in each category would show a broad range of specific gravity. Table 4 summarizes the impedance readings by category. Mean impedance readings by category were as follows: 32

Table 3 Specific Gravity by Category

Sample Standard Categorya Size Mean Deviation Minimum Maximum

A 51 1 .014 0.0006 1 .004 1 .024 B 53 1 .016 0.007 1 .004 1 .025 C 30 1 .028 0.003 1 .025 1 .037

0 38 1 .002 0.001 1 .001 1 .003 E 37 l .019 0.009 1 .005 1 .025 Fb 27 G 33 1 .016 0.009 1 .003 1 .024

Note. Total sample size = 269. aCategories of urine: A = normal; B = elevated RBC's, WBC's, and/or bacteria; C = concentrated; 0 = dilute; D = glycosuric; F = Pyridium; G = proteinuric. bSpecific gravity was not obtained on specimens in Category F (urine from patients known to have taken Pyridium). 33

Table 4 Impedance Readings a by Category

Sample Standard Category b Size Mean Deviation Minimum r~ax imum

A 51 24.8 16. 1 10.3 30.7 B 53 24.5 12.4 9.0 65.1 C 30 13.9 5.4 7.7 30.8

0 38 54.5 31 .0 17.9 143.0

E 37 27.0 14.3 13. 1 91 .8

F 27 19.6 10.9 7.4 55.2

G 33 25.3 12.6 10.0 66. 1

Note. Total sample size = 269.

aUnit of measurement = ohm. bCategories of urine: A = normal; B = elevated RBC's, WBC's, and/or bacteria; C = concentrated; D = dilute; E = glycosuric; F = Pyridium; G = proteinuric. 34

Category Type of Urine ~1ean Impedance ; n Ohms A Normal 24.8 B Elevated RBC1s, WBC's, and/or bacteria 24.5 C Concentrated 13.9 0 Dilute 54.5 E G1ycosuric 27.0 F pyridium 19.6 G Proteinuric 25.3 Categories A, B, and G had mean impedance readings that vary by less than or equal to 0.8 ohms. It is theorized that electrical impedance is a reflection of ion concentration and since impedance is inversely related to ion contact it is significant to note that Category C, concentrated urine, had the lowest mean impedance readings and Cate- gory 0, dilute urine, had the highest mean impedance readings. Re- viewing the minimum and maximum impedance readings and the standard deviations in each category suggests that impedance readings in each category vary considerably. As a result of outliers, which were not mathematically identified and removed from the data, some of the standard deviations may be larger than expected. Analysis of the dot diagrams will further clarify this. A dot diagram was prepared for each category of urine (see Figures - 7). The dot diagrams graphically illustra how the data is spread about the mean and identify those observations that differ rather markedly from the rest of the observations, possible outliers. Visual inspection of the dot diagrams shows which categories had samples that cluster closest about the mean and which categories had samples that are widely spread about the mean. 35

110

100

80 0 0

---til 70 E -=:. 0 0 60 OJ u c: 50 r'O -0 CJ 40 0.. - 30 ...... 20 ~ ...... - .-. - ...... - ~ .., , ...... -- .-. ..:.. -- ..... - ~ ..... ~ ..-. 7" ------;- ....

.. . " . 10

5 10 15 20 25 30 35 40 45 50 Sam p 1 e N u m b e r

Figure 1. Dot diagram of impedance readings Category A (normal urine).

- ~1ean impedance = 24.7 ohms. ---Mean impedance corrected for visually observed out- 1 i ers = 21. 5 ohms. o Visually observed outlier. 36

110

100

.--. (/) E 80 ..s:::: 0 70 Q) 0 u <:: 60 1'0 V • Q) 50

Q. E 40 • •

.. • -.. .., - ..-. ... -:- 20 . . .. • 10 •

5 10 15 20 25 30 35 40 45 50 Sam p 1 e N u m b e r

Figure 2. Dot diagram of impedance readings Category B (elevated RBC1s, WBC's, and/or bacteria).

- Mean impedance = 24.5 ohms. --- Mean impedance corrected for vi sua 11 y observed outlier = 24.2 ohms. o Visually observed outlier. 37

120

110

100

...-... U'l 80 E

~ 0 70

(J) u 60 c to \:::l 50

(J) 0- E

20 . . 10 .. . . • •

5 10 -\ 5 20 25 30 35 40 45 50 SarTl~ll e N u m b e r

Figure 3. Dot diagram of impedance readings Category C (concen trated) .

---. Mean impedance = 13.9 ohms ~ 38

120 • 110

100

..--.. VI 90 E .. .s= 0 80

5 10 15 20 25 30 35 40 45 50 Sam p 1 e N u m b e r

Figure 4. Dot diagram of impedance readings Category 0 (dilute). ---Mean impedance = 54.5 ohms. 39

....-. 80 V) E ..s:::: 70 0

Q) 60 u o ~ ro 50 "'0

Q) 0.. 40 E

1--1 30 . . - - - ".------_...... , ... - -...... -.------. ~ - ~ .... - .... .- ... 20 . .

5 10 15 20 25 30 35 40 45 50 S 3 m p 1 e N u m b e r

Figure 5. Dot diagram of impedance readings Category E (glycosuric),

- Mean impedance :::: 27.0 ohms. ---Mean impedance corrected for visually observed outlier:::: 24.3 ohms. o Visually observed outlier. 40

110

100

.---. 80 l.Il E .s:::; 70 0

OJ u 60 c: ro 0 ""0 OJ Cl.. 0 E ...... 0

...... -.---..-.~.----=-..-...-.-----..-.----. .... ------~---- ......

Sam

Figure 6. Dot diagram of impedance readings Category F (Pyridium).

- Mean impedance = 19.6 ohms. ---Mean impedance corrected for vi sually observed outliers = 16.4 ohms. o Visually observed outlier. 41

120

110-

...- VI

== ...c 0

OJ 0 U C

"'0 OJ a.. - 4

5 10 15 20 25 35 40 45 S a In p 1 e N U In b e r

Figure 7. Dot diagram of impedance readings Category G (proteinuric). - Mean impedance :: 25.3 ohms. ---Mean impedance corrected for vi sua lly observed outliers :: 24 ohms. o Visually observed outlier.

rIk 42 Category 0, dilute urine (see Figure 4), had the most widely spread readings, and there seemed to be no particular grouping or linear pattern. It is worth noting that the specific gravity of Category 0 had a very narrow range, 1 .001 - 1 .003, yet the impedance readings had a widely spread distribution. In contrast, Category C, concentrated urine (see Figure 3), had a wider range of specific gravity, 1.025 - 1.037, while at the same time it had a very narrow distribution of data about the mean. As stated previously, Categories A, B, and G have relatively close means and the distribution of the data appears similar (see Figures 1,2, and 7). Therefore, with the statistical information available, no discernible differences between the mean impedance readings and the data distribution can be detected by observation. Outliers were not mathematically or visually corrected for when statistical analysis was performed because it was felt that these effects would be minimal. However, the dot diagrams show a second mean which has been corrected for outliers which were visually identified. This corrected mean is represented on the dot diagrams by a broken line. The purpose of this was for comparison only and it appears on observation that the relationship of the means to each other remains reasonably the same as before.

Statistical Inference In order to establish statistical inference between or within the categories of urine sampled, the following statistical tests were performed: (1) a correlation between sample temperature, specific gravity and impedance readings on all 269 samples disregarding 43 category divisions; (2) a correlation of the category of urine to sample temperature, specific gravity, and impedance readings; (3) an analysis of variance, both parametric and nonparametric, between the seven categories of urine to test for equality of mean impedance read ings; (4) two tests for homogeneity of variance with a variance sta bilizing transformation; (5) a general test to establish potential group and subset relationships that may exist between the mean impe dance readings and the seven categories of urine; and (6) a !-test to compare the mean of normal urine against the means of the other categories of urine to test for equality of means.

Correlations The continuous variables of sample temperature, specific gravity, and impedance readings were used to calculate Pearson product moment correlation coefficients. The Pearson product moment correla tion method is a measurement of the linear relationship between the continuous variables in the study. Basically, the entire sample was considered as a whole, disregarding categorization. Comparisons were made between sample temperature and specific gravity, between sample temperature and impedance readings, and between specific gravity and impedance readings. Table 5 shows the numerical results of this test. As shown by the correlation coefficients, there was no signifi cant co-relation established between sample temperature and specific gravity or between sample temperature and impedance readings; there fore, it can be concluded that the methods implemented to control sample temperature were sufficient. 44

Table 5 Pearson Product Moment Correlation Coefficients Ce. .::. 0.05 )

Correlation Variables r Sample Size Sample temperature to specific gravity 0.0999 0.122 Sample temperature to im pedance readings -0.979 0.109 269 Specific gravity to im pedance readings -0.6150 0.0001

Note. Total sample size = 269. aSpecific gravity was not obtained on specimens in Category F (urine from patients known to have taken Pyridium). 45 When looking at the relationship between mean specific gravity and mean impedance, a correlation coefficient r = -0.6150 with a significance level of £ = .0001 suggests that there is a high probability that a correlation exists between specific gravity and impedance, and that as specific gravity rises impedance falls. This was as suggested in the review of the literature. However, analysis of the dot diagrams has shown that while the mean impe dance of dilute urine (low specific gravity) is high, the sample values ranged from 17.9 - 143.0 ohms. This raises the question of what other factors that were not measured in this study have an affect on impedance. This question will be further explored in the discussion. Eta Correlation Coefficients An eta correlation was used to assess the potential relation- ,ship between the categories of urine and sample temperature, specific gravity, and impedance. The eta correlation coefficients do not re quire a linear relationship, but measure any shape of relationship, linear or curvilinear. As can be seen in Table 6, the probability of a correlation existing between sample temperature and category of urine is so extremely small that no correlation can be identified. Again, this could be expected from the well defined controls placed by the methodology on temperature. Specific gravity showed a significant correlation to the cate gories of urine (see Table 6). However, it is somewhat difficult to analyze the true significance of this correlation. Five of the seven categories of urine had no controls for specific gravity other than what was defined as the normal range (1.003 - 1.025). The inclusion 46

Tab 1e 6 Correlation of Dependent Variable to Category of Urine Using Eta Correlation

(£.~ 0.05)

Dependent Variable Eta £. Sample Size

Samp1e temperature 0.2304 0.0256 269 a Specific gravity 0.7557 < 0.00001 24l Mean impedance reading 0.5750 < 0.00001 269

Note. Total sample size = 269. aSpecific gravity was not obtained on specimens in Category F (urine from patients known to have taken Pyridium). 47 of two categories of urine that are distinguished only by specific gravity, when doing a correlation of specific gravity to impedance readings, yields a correlation that has bias. Removing these two categories (C and D) from the sample could potentially reduce the strength of the correlation between mean specific gravity and the category of urine. Mean impedance readings also showed a significant correla tion to the category of urine (see Table 6), but were not as highly correlated to the category of urine as that of specific gravity. Since Categories C and 0 were controlled to provide specimens with the extremes of specific gravity and it is known that specific gravity influences impedance readings, this correlation is also potentially biased. The removal of Categories C and 0 from the data would prob ably reduce the level of correlation between mean impedance readings and category of urine. Since it is not possible to do this at this time, the influence of these two categories cannot be evaluated.

Analysis of Variance An analysis of variance is generally used to test the hypo thesis that the samples are drawn from populations with the same mean. In other words, the hypothesis to be tested is that there is no dif ference in means among the categories of urine. Analysis of variance will only identify significant variations among the means in to.tal, it will not identify differences based on comparisons of the individ ual means of the categories. 48 F Statistic An analysis of variance can be conducted with the [ statistic to test for significance. The E statistic is the ratio of variance between groups to the variance within groups. Variance between groups is a measare of how the group means vary about a grand mean, that is a mean of all the samples of the groups put together. The variability of the individual samples observed within each group is called 'with-

in group variance. I This value is estimated from the sample. If between group variance and within group variance are equal, then there is no difference between the groups. Referring to the [ statistic,

Variance Between Groups F = Variance Within Groups

it can be seen that the larger the numerical value of [, the greater the probability that the groups represent different populations. The major requirement to perform the [ test is that the ob servations be taken from a normally distributed population with a homogeneous variance. This is an important assumption because groups can show significance as a result of differing means or differing variance, but for this study, the test is to determine differences in means only. In addition to the above stated conditions, there are other criteria that are necessary for an analysis of variance to be conducted. These are: (1) Samples must be taken which are independent of each other; (2) all samples must be drawn randomly; and, (3) there is a linear relationship among variables. 49 In this study, the samples taken do not necessarily reflect that they are taken from a normally distributed population; however, relying on the Central Limit Theorem (Williams, 1968), it can be as sumed that this criteria is met. The question of independence be tween samples was ensured by the methodology established in the study. The second requirement, that the sample be randomly selected, is nearly impossible to completely achieve under real world conditions, but for purposes of general statistical analysis, the methods used to

collect the samples do not seriously violate the princi~les of random selection. Finally, the linear relationship of the data was estab lished by the fact that the Pearson product moment correlation yielded acceptable results and identified the linear relationship of the variables. The only point left to be established is the homogeneity of variance. In order to do this, two tests for equality of variance were conducted, Bartlett's test, and Cochran's test. Each of these (see Table 7) indicated that heterogeneity of variance existed. There fore, a variance stabilizing transformation based on the natural log function was used to correct for this. This type of transformation usually also brings the data closer to having a normal distribution. After the transformation, the data showed homogeneity of variance (see Table 7). An F value was calculated using the transformed data and significance level computed for that [value. The F value found for the transformed data was [= 23.407, £ = 0.00005. Since the study

des i gn spec i f i ed ale vel 0 f s i gn i f i can ceo f £ 2. 0 . 05 , the cal c u1 ate d F 50 statistic was accepted and indicates that the mean impedance reading ;s not the same for the seven categories of urine (see Table 7).

Nonparametric Test (Kruskal-Wallis) To satisfy any objections that may be raised as to the va lidity of log transformations on statistical data when utilizing parametric tests, a nonparametric analysis of variance was performed without a transformation. A Kruskal-Wallis one-way analysis of variance was used on the

independent samples. Since the ~ statistic is significantly larger than the Chi-square with K-l degrees of freedom (see Table 8), the re sults of this analysis agree with the F test that the null hypothesis

~123 = ~ = ~ cannot be accepted.

Scheffe's Test The final parametric test performed on the data was a posteriori contrast test, Scheffe's test. An a posteriori contrast test is a systematic procedure for comparing all possible pairs of group means. It divides the groups into homogeneous subsets, where the difference in the means of any two groups in a given subset is not significant. The significance is preselected at a prescribed level. Scheffe's test is exact, even for groups of unequal size. For this study, this test was performed on the transformed data. The results of the test (see Table 9) established that Categories A, C, and F belong to one subset and taken as a set all have the same population mean impedance readings. A second subset containing Categories A, B, E, F, and G suggests that these categories have the same population Table 7

Natural Log Transformation of Original Data

(£. ~ 0.05)

Original Data Ln x Transformed Data Sample Standard Sample Standard Categorya Size X Deviation Category a Size X Deviation

A 51 24.8 16. 1 A 51 3.06 0.5189

B 53 24.5 12.4 B 53 3.09 0.4617

C 30 13.9 5.4 C 30 2.57 0.3491

D 38 54.5 31.0 D 38 3.86 0.5292

E 37 27.0 14.3 E 37 3.20 0.4125

F 27 19.6 10.9 F 27 2.86 0.4740

G 33 25.3 12.6 G 33 3.12 0.4733

Bart1ett ' s Test Bart1ett ' s Test aCategories of urine: A = normal; B = ele vated RBC·s, WBC·s, and/or bacteria; F = 17.414 F = 1.251 C = concentrated; 0 = dilute; E = glycosuric; Q ~ 0.001 Q~0.276 F = Pyridium; G = proteinuric. Cochran's Test Cochran's Test C = 0.5106 C = 0.1863 U1

£. ~ 0.0001 Q ~ 0.598 52

Table 8 Kruska1-Wa1lis Test (2. ::.. O. 05) a Category Sample Size Mean Ranks

A 51 124.37 B 53 132.47 C 30 54.97

0 38 222.99 E 37 150. 15

F 27 98.63

G 33 139.70

Note. Total sample size = 269. H statistic = 88.786 Chi-square 12.6 df = 6 Significance = 0.0001 aCategories of urine: A= normal; B = elevated RBC's, and/or bacteria; C = concentrated; 0 = dilute; E = glycosuric; F = pyri dium; G = proteinuric. 53

Table 9 HOl11ogeneous Subsets a from Scheffe's Test

Subset I Subset I I Subset III b b Category XC Category XC Category b XC

A 3.06 A 3.06 0 3.86 C 2.57 B 3.09 F 2.86 E 3.20 F 2.86 G 3.12

aA subset of categories whose highest and lowest means do not differ by more than the shortest significant range for a subset of that size. bCategories of urine: A = normal; B = elevated RBC's, WBC's and/or bacteria; C = concentrated; 0 = dilute; E = glycosuric; F = Pyridium; G = proteinuric. cTransformed score means. 54 mean impedance readings. While it may appear that these two previous conclusions contradict each other, in reality, they do not because removing Category C would have established the second subset of A, B, E, F, and G, but, when C is included, the relationship becomes one of A, C, and F. This is the basic manner in which Scheffe's test works. Finally, the test denoted Category D as a one-element subset having a higher population mean impedance than the other categories. It should be noted that Scheffe's test is a conservative test detecting only large differences between means as it must allow for multiple comparisons at the desired £ level.

Hypothesis Testing Based on the research hypotheses that the means of the six categories of urine, other than normal urine, would be significantly different than that of normal urine, the null hypothesis that the means would be equal was created. To test the null hypothesis a two 2 tailed t-test for ~l = ~2 with 0 unknown was used. The t-test is a ratio between the sample mean difference and the standard error of that difference. Many different methods can be used to estimate the standard error of the mean difference, which gives the t-test great flexibility in as much as population variances ll1ay or may not be known and may have to be estimated from the samples, as in this case. Six null hypotheses were created to compare the mean impedance of normal urine to the mean impedance of the other six categories. The t-statistic was calculated using the sampling statistics from Table 4, and the results are shown in Table 10. The level of significance for the tests again was £ ~ O. As can be seen from the 55

table, all the null hypothesis that ~ = U2 were accepted except for Categories C, concentrated, and D, dilute urine. To facilitate the discussion and analysis of the hypotheses being studied in this research project, each of the hypotheses will be reviewed individually. Hypothesis I: The electrical impedance of urine con taining an abnormally high count of red blood cells, and/or white blood cells, and/or bacteria will be significantly different from that of normal urine.

The results of the t-test show that the null hypothesis ua = U can be accepted; therefore, the research hypothesis that U U b a f b can be rejected. Further support for this can be taken from an analy sis of the dot diagrams (see Figures 1 and 2) which show that both categories have approximately equal data distribution about their means and equal means. Scheffe's test also suggested that categories A and B are elements of the subset A, B, E, F, and G. Based on this, it seems reasonable to state that there is no significant difference between the mean impedance readings of normal urine and urine with abnormally high counts of RBC's, WBC's, and/or bacteria. Hypothesis II: The electrical impedance of concentrated urine will be significantly different from that of nor mal urine.

Reviewing the !-test on the null hypothesis that ua = Uc re veals that the null hypothesis should be rejected (see Table 10). The dot diagrams (see Figures 1 and 3) support this conclusion and also show a tendency for the data in Category C to be much more closely grouped about the mean than that of Category A, normal urine. Scheffe's test has indicated that A and C are both elements of the Table 10

T-test for Comparison of Means by Category

1 Degrees of Table Value Calculated Mean Comparisons Hypothesis Decision Freedom T1 - 1/2 £ T

Mean A :: Mean B I Accept 102 1 .975 0.106

Mean A ;::;Mean C I I Reject 79 1 .995 3.589

Mean A ;::;Mean D I I I Reject 87 1 .990 5.88

Mean A :::;i~ean E IV Accept 86 1 .990 0072 r~eanA :: Mean F V Accept 76 1 .994 1 .50

Mean A :::;Mean G VI Accept 82 1.993 0.15

Note. Categories of urine: A = norlllal; f3 elevated RBC's, WBC's, and/or bacterla; C concentrated; D dilute; E glycosuric; F Pyridiunl; G = proteinuric.

(5l m 57 subset A, C, and F, however, Scheffe's test only measures large differences between means and the t-test is a more discriminating test. It can be concluded that the electrical impedance of concen trated urine is significantly different than that of normal urine. Hypothesis III: The electrical impedance of dilute urine will be significantly different from that of normal urine.

The t-test on the null hypothesis ~a = ~d suggests rejection of the null hypothesis (see Table 10). Therefore, the research hypo

thesis that lla f ~d is acceptable. Scheffe's test indicated that Category 0 comprised a single element subset. With this being a test that only identifies large differences, the acceptance of this research hypothesis is highly supported by the test. The dot diagrams (see Figures 1 and 4) also support this. Hypothesis IV: The electrical impedance of glycosuric urine will be significantly different from that of norma 1 uri ne. The results of the !-test suggest acceptance of the null hypo

thesis ~a =]Je (see Table 10). Therefore, the research hypothesis:Ja

11 can be rejected. This conclusion is supported by a review of r e the dot diagrams (see Figures 1 and 5) which show Categories A and E have data points that are distributed similarly about the mean. Scheffe's test also placed Categories A and E in the same subset. Thus, it appears that the electrical impedance of glycosuric urine is not significantly different than that of normal urine. Hypothesis V: The electrical impedance of urine con taining Pyridium (phenazopyridine HC1) will be signi ficantly different from that of normal urine. 58

The !-test on the null hypothesis a = Wf also suggests that this hypothesis be accepted and thus, the research hypothesis Wa f W is rejected. While the mean impedance readings for these cate f gories appear to be numerically distinct, statistical analysis and a review of the dot diagrams (see Figures 1 and 6) show that the mean impedance readings of Category F are not significantly different than those of Category A. Again, Scheffe's test placed Category A and Category F in subset A, B, E, F, and G. Hypothesis VI: The electrical impedance of urine con taining abnormally high amounts of protein will be significantly different from that of normal urine. In this case, the test on the null hypothesis wa = Wg again suggests acceptance (see Table 10). Thus, the research hyoothesis Wa f Wg is rejected. Since the mean impedance readings from Category A and Category G are very close, the dot diagrams show similar data distribution patterns about the mean (see Figures and 7), and Scheffe's test placed A and G in subset A, B, E, F, and G, the rejection of this hypothesis has been supported by the statistical analysis of the data. Table 11 summarizes the mean impedance, mean sample temperature and mean specific gravity by category_

Discussion Before this research was undertaken, a review of literature had established that dilute and concentrated urine probably would have significantly different mean impedances than that of normal human urine. The literature and basic chemical principles suggested 59

Table 11 Comparison of Mean Impedance, Sample Temperature, and Specific Gravity by Category

Mean Mean Mean Sample Impedance Sample Specific Categorya Size (ohms) Temperature (OC) Gravity

A 51 24.8 24.6 1 .014 B 53 24.5 24.0 1 .016 C 30 13.9 24.1 1 .028

0 38 54.5 23.8 1.002

E 37 27.0 24.0 1 .019 Fb 27 19.6 24.4

G 33 25.3 24.1 1 .016

Note. Total sample size = 269. aCategories of urine: A = normal; B = elevated RBC's, WBC's, andl or bacteria; C = concentrated; D = dilute; E = glycosuric; F = Pyri dium; G = proteinuric. bspecific gravity was not obtained on specimens in Category F (urine from patients known to have taken pyridium). 60 that the other categories of urine might not be significantly differ ent than normal. These expectations were confirmed by the results of this study. The literature review, however, had not predicted the phe nomena noted in the dilute urine category. In this case, there was an unusually wide distribution of impedance readings (17 - 78 ohms with four readings above 110 ohms) in a category that had the narrowest specific gravity range (1.001 - 1.003). On the opposite end of the scale, concentrated urine with a specific gravity ranging from 1.025 - 1.037 only had impedance readings that ranged from 7 - 30 ohms. Since this variable was equally well controlled in the concentrated urine category as in the dilute urine category, it is doubtful that specific gravity alone could account for these wide variances in impedance readings in dilute urine. The question is then what other factors could account for the variety of impedance readings encountered in the dilute samples of urine? Since urine is composed of many chemical compounds, the ion content can vary considerably. In theory, it should be possible to calculate ionic content and ionic mobility on a single element chemi cal solution of known concentration. In a solution comprised of many chemicals it may well be possible to determine the ionic con tent, but it is rarely possible to determine ionic mobility (Clark, 1952) . The Oebye-Hucke1 theory explains the interactions of ions in solution and the resulting ionic atmospheres (Clark, 1952; Chang, 1977). They have shown that the ionic atmosphere and its rate of 61 movement is determined by the positive and negative charges on the ions and the type of ;ons in solution. As the number of ions in solution decreases, these factors playa more important role on the conductance of electricity. It seems likely then that impedance, which is inversely pro portional to specific gravity (ionic content), must be related to ionic mobility. While it cannot be stated conclusively that this is the reason for finding readings in dilute urine with such large variances, it does seem likely that the chemical composition does change greatly from person to person and from voiding to voiding. Since this may be the case, the ionic composition of dilute urine at any given time may vary greatly even though the number of ions in solution is small. Taking into consideration the above-mentioned principles, it is suggested that in dilute ur;ne the variances in ion types and the resulting ionic mobility would have a significant effect on the impedance readings of dilute urine. This may not explain completely the phenomena seen in dilute urine, but it does illustrate the difficulty in making a specific statement about the impedance of a solution as chemically complex as urine. Basically, this study has determined that the only categories of urine having a mean impedance significantly different from that of normal urine are concentrated and dilute. The sample sizes col lected and the statistical analysis was constructed to identify large differences in the mean impedance readings or very distinct correlations between the variables. No absolute conclusions can be reached, it does appear however that the number of variables 62 affecting electrical impedance readings taken on urine goes consider ably beyond those identified by urinalysis results, sample tempera ture, and specific gravity. This study was not designed to try and determine any of these factors, but it is speculated that some factors might be (1) the pH of urine (Adamson, 1973), (2) the amount and type of medication taken by patients prior to voiding, (3) the physiological changes precipitated by illness, or (4) the length of time after voiding that the impedance readings were taken.

Limitations The primary limitations of this study are in the areas of sample size, temperature control, and categorization of urine speci mens. While the sample size was adequate to detect large differences in mean impedance reading"s, the methodology and time constraints did not allow for collection of sufficient samples to distinguish medium to small differences in the mean impedance between categories. Sta tistical estimates indicate that in order to distinguish small dif ferences between groups, at least 390 specimens would be needed for each category. Since temperature has a significant effect on electrical impedance and even though the statistical analysis demonstrated that in this study temperature was sufficiently controlled to eliminate significant changes in impedance, the methodology for temperature control was tedious and time consuming. One possible alternative for controlling the effects of temperature on impedance measurements would be to establish a temperature correction factor for each cate gory of urine. This could be done by slowly raising the temperature 63 of a number of samples in a particular category and noting how the impedance changes in relation to the temperature changes. Impedance readings could then be taken on the urine samples, the temperature recorded, and the impedance measurement adjusted to a specified base temperature. Bu doing this, temperature effects would be accounted for and samples could be processed in less time than was required in this study. The last notable limitations relates to the assignment of urine specimens to categories. While the review of literature demonstrated that the chemical composition of urine is quite complex (Free & Free, 1975), the assignment to category was made using a rather crude system of analysis. Urinalysis results do not precisely quantify the abnormal constituents of urine, and there are innumer able constituents that are not accounted for in this method. Thus, any conclusion regarding the effects of abnormal changes in urine, as determined by routine urinalysis, on the electrical impedance of human urine must be tentative. CHAPTER VI

SUMMARY AND RECOMMENDATIONS

Summary Up to the time this study was conducted, no published work could be found that thoroughly investigated the electrical impedance of human urine. This experimental research was based on the need to understand how impedance varies in urine of different composition. Such information is pertinent to the development of a noninvasive device to monitor bladder fullness. In total, 269 urine samples were randomly collected from the population of urine specimens sent to The University of Utah Clini cal Chemistry Laboratory. Each sample was assigned to one of seven categories based on its urinalysis results. Electrical impedance measurements were taken, under controlled laboratory conditions, on all samples. The results of this study indicate that urine with a higher than normal content of either red blood cells, white blood cells, protein, glucose, bacteria, or urine containing Pyridium does not have a significantly different mean impedance than that of normal urine. Urine that is either dilute (specific gravity equal to or less than 1.003) or concentrated (specific gravity equal to or greater than 1.025), does have a mean impedance significantly 65 different than that of normal urine. The findings on dilute and concentrated urine are in agreement with the review of literature which indicated that impedance is inversely proportional to ion con centration. The mean impedance of concentrated urine was 13.9 ohms while the mean impedance of dilute urine was 54.5. The analysis of the category of dilute urine suggests that there are factors in the composition of urine, other than those identified in this study, that significantly influence the impedance of human urine. The specimens obtained for this category had a very narrow range of specific gravity (1.001 - 1.003) with all other values within normal limits, but at the same time, the impedance readings covered the largest range of any category (17.9 - 143.0 ohms). Even though the statistical analysis of the data identified no large differences between the mean impedance readings of the categories except for dilute and concentrated, the data analysis did confirm that impedance measurement of urine must be studied under well-controlled and well-defined conditions in an effort to identify more specific factors which contribute to impedance and the degree to which they contribute.

Sugqestions for Further Study Impedance studies on human urine have just begun and the opportunity for further study in the field is broad. The data in this study showed a wide range of impedance read ings in each category. As a result, future studies might be done to determine if one individua1·s urine, at a given specific gravity and 66 temperature, has a constant impedance. Also, it has yet to be deter mined if the mean impedance of normal urine is equivalent from individual to individual. Specific gravity has been shown to significantly influence the electrical impedance of human ruine. Future studies could explore the predictability of that relationship. In other words, at a given speci fic gravity and temperature, is impedance the same in samples from different individuals. Urine is chemically complex and the actions of its ions in fluence its impedance; therefore, it is possible that the impedance of urine may change over time as a result of its changing chemical compos ition. Further studies are needed to determine if more rigid con trols are indicated over the time interval between voiding and the measurement of impedance. In order to help identify more specific factors that alter electrical impedance, other studies might be directed at more rigidly defined categories or at breaking down one category into more distinct divisions. Impedance research on fluids taken out of the human body is relatively new. As research in this area continues and the methodo logy is perfected, it is anticipated that many body fluids and organs can be studied using electrical impedance. Studies on body fluid might include rapid detection of abnormal constituents (for example, amniotic fluid), and investigative work on human organs. Impedance studies done directly on the human body might in clude identifying the abnormal accumulation of fluids, i.e., blood 67 or detecting changes in organ size and density. An important advan tage to these impedance methods is that they can be carried out with a minimum of discomfort for the patient.

Implications for Nursing Most research in nursing today investigates problems that occur in the clinical setting. While this study has only indirect clinical application to the development of a noninvasive device to monitor bladder fullness, it has direct application to continuing nursing research on human urine and other body fluids. A device to monitor bladder fullness would have the potential for reducing the number of catheterizations a particular patient undergoes in order to maintain correct bladder emptying and for mak ing it easier for patients with impaired function, such as paraple gics, to lead more active and normal lives. This study has indirect application to some of the peripheral problems that such a device would have to deal with. As stated, the findings of this study are directly applicable to further research utilizing impedance measurements on human urine and other body fluids. The analysis of the data suggests there are many aspects of human urine that have not yet been thoroughly investigated. One such area in which this line of research could be contin ued involves investigating the wide range of impedance readings noted in dilute urine. Electrical impedance measurements on other body fluids could also contribute to the perfection of impedance technology as well as 68 aid in the evaluation and care of patients. Nurse researchers have studied the incorporation of bio instrumentation equipment into patient care from the viewpoint of minimizing inconvenience and trauma to the patient. In the future, nurse researchers can make significant contributions to the develop ment and design of bio-instrumentation equipment, as well as to its incorporation into care of the patient. APPENDIX A

ROUTINE URINALYSIS 70 The University of Utah Clinical Chemistry Laboratory

Test Method Normal Results pH Dipstick* 5-8 Specific Gravity Refractometer 1.003 - 1.030 Protein Dipstick* Negative Ketone Dipstick* Negative Hemoglobin Dipstick* Negative Glucose Dipstick* Negative Bilirubin Dipstick* Negative Urobilinogen Dipstick* 1-4 Ehri 1i ch Units White Blood Cells Microscope Few = less than five/aver age of 10 high power fields Red Blood Cells Microscope Few = less than five/aver age of 10 high power fields. Bacteri a Microscope Negative Epithelial Cells Microscope Squamous Male - rare Female - 1+ Transitional Few

*Using 8io-Dynamics Chemstrip or Ames Multistick. APPENDIX B

URINE IMPEDANCE BOX 72 ]3

H~tJiR6ED ViE).J c:: Cor:~JEf\

8.fCTR,uiJE STRIP 2.381 (fl'L FRoM \!IE\J t'~ _---C-f~,i :/ 0.317 5'~AYl

E~D Vlc,vJ APPENDIX C

ELECTRODE COATING WITH POLY HEMA, POLY(2-HYDROXYETHYL METHACRYLATE) (HYDRO-MED SCIENCES, INC.) 75 1. 2.45 grams Poly Hema powder added to 100ml Methanol = 3% Poly Hema solution. 2. Mixed for 45 minutes using an ultrasonic cleaner bath. 3. Electrode plates dipped in Methanol to remove previous coating of Poly Hema. 4. Electrodes plates dipped into the solution until the electrodes completely covered with solution. 5. Electrode plates allowed to dry at room temperature for 30 min utes prior to use. APPENDIX D

HIGH RESOLUTION IMPEDANCE CONVERTER 2991 77 Description The Transmed Scientific Model 299l/Impedance Converter con sists of the following basic circuit blocks: 1. 50 kHz Ultra Stable Oscillator with an output of 50V (PK-PK) into the required loads. 2. A resistive network which holds the current passing through the subject to a constant 50 wA over a range of a to over 100 OHMS. 3. Two identical amplifier/rectifier/filter blocks referred to as the IIsubject chain" and the "reference chain.1I 4. A 0-50 pA meter used to balance and cal ibrate the entire instrument. 5. Associated Battery Power Supplied and Regulation circuitry.

Note. Reprinted by permission of H. M. Hanish, Chief Engineer~I, Morro Bay, California, January 29, 1980. 78 Explanation The circuit may be viewed as a simple AC wheatstone bridge:

M 10 Turn Subject Su bj ect Reference Chain Chain Digital Poten tiometer

50-0-50 DVM#l

When the digital potentiometer is adjusted so that the meter (M) reads zero, then the potentiometer will be equal to the subject impedance--providing all circuits are properly calibrated. The two digital meters assist in accurate calibration as well as providing a high resolution readout. Since excitation to the sub ject and the reference chains is provided by the same oscillator, the effects of drift are minimized. The constant current network is configured so that tetrapolar or bi-polar electrode systems may be used. The 100 OHM resistor in series with the patient is used to accurately adjust the subject chain first. The subject is connected, and the reading on DVM#l noted. The switch bypassing the 100 OHM resistor is opened and the reading again noted. The subject chain is then adjusted until the difference 79 in the two readings is exactly 100 OHMS. When the switch is closed, DVM#l will now read the magnitude of the subject's impedance to an accuracy of better than 1%.

Using the 50-0-50 ~A meter, the reference chain is then ad justed as follows:

le Set the digital dial to the impedance indicated on

DVM#l~

2. Adjust IICalib. Adj." until 50-0-50 ~A meter reads

"0. 11

Stability is further enhanced by using integrated circuits with dual circuits on the same substrate. For example, both AC amplifiers (subject and reference) are on the same chip. The recti fier circuitry for both chains also follows this design criteria. APPENDIX E

HEATHKIT DECADE RESISTANCE BOX MODEL EU-30A 81 The Heathkit Decade Resistance Box, with range of ohm to 9,999,999 ohms in 1 ohm increments, was utilized. It has watt

precision with ~ 0.1% accuracy. The readout is supplied on numbered discs on switch shafts, visible through windows above each decade. The decade resistance box can take current in 2 voltage ranges 105- 125 or 210-250 volts or 50/60 Hz at 10 watts of power (Decade Resis tance Box, 1969). APPENDIX F

HEATHKIT MODEL IM-28 VACUUM TUBE VOLTMETER 83

The Heathkit Vacuum Tube Voltmeter contains a DC voltmeter, an AC voltmeter and an electronic ohmmeter. The e1ectronic ohmmeter was utilized by this study. It has seven ranges going from xl ohm to xl meg in 101 increments. It utilizes an internal battery, 1 1/2 volt C cell, to supply the current to make the measurements. The readings are made on a 6" 200 milliamp movement, multiple scale meter (Vacuum Tube Voltmeter, 1968). APPENDIX G

UNITED SYSTEMS CORPORATION DIGITEC HT SERIES MODEL 5810 85 A United Systems Corporation Digitec electronic Centigrade thermometer with Yellow Springs Instruments thermistor probes #702 and #709A was used. The instrument has three channels with ranges from 0 to 100.0° Centigrade or -30 to +50° Centigrade either scale having an accuracy of + 0.02% full scale (probes may be individ ually calibrated to O.lOC). The Oigitec has + LED indicators 0.3 11 high. Response time is 41 sec. under normal conditions (Thermometer Oigitec, 1978). APPENDIX H

BACHARACH HUMIDITY --TEf~PERATURE INDICATOR MODEL 22-7056 87 The Bacharach Humidity-Temperature indicator provides a

temperature range of O-139°F with a time lag constant of less than 4.0 seconds. APPENDIX I

CALIBRATION OF THE HIGH RESOLUTION IMPEDANCE CONVERTER by Michael Lingwall, Laboratory Technician 89 Step Number One Place a known value precession resistor (1%) across the in put. (The input referred to, is the subject input. It is going to be used in a bi-polar configuration, so the wire straps which short the two available subject inputs, remain shorting the two inputs to gether~ )

Step Number Two Insuring that the 500 OHM calibrating switch is in the up position, adjust the s trimpot so that the digital readout meter (drom) indicates the value of the precession resistor.

Step Number Three Adjust Reference knobs (which read left to right x 100, x 10, xl) to the value of the precession resistor, which should also be the same as the readout of the meter (drom). (Example: If using 511 OHM resistor, knobs should read 511, 5 x 100, 1 x 10, 1 xl.)

Step Number Four Take note of "sens" switch. This is the sensitivity of the meter. Down position is low sensitivity and the meter will read + 5 OHMs full scale deflection. With the switch in the up position the meter is in high sensitivity and has + 2,5 OHM full scale de flection. For calibrating purposes it should be in the downward position to start. Adjust r trimpot so that the meter needle is over the 0 (zero) on the OHM x .1 d'Arsonval movement scale meter. Move the "sensu switch to the upward position and adjust -; trimpot 90 to a ~ (zero) reading on the scale meter. The High Stability Im- pedance Converter is now calibrated for subject impedance measurements. (Note: Be sure to remove precession resistor from input as final step of calibration.)

Note. A one-hour or better warm-up time of the converter should be done before any attempt be made to calibrate the impedance converter. APPENDIX J

DETAILED METHODOLOGY FOR THE MEASUREMENT OF ELECTRICAL IMPEDANCE 92 General Guidelines 1. Both lab doors should be closed during data collection 2. A clipboard is provided for holding the data collection sheets while taking measurements--it is important to record measurements immediately p they are determined. 3. When reading the gauges be sure eyes are in a straight line with the need1es. 4. The Ag-Ag-Cl electrode plates are coated with P01y hema once a week.

Instruments 1. Impedance Converter with Impedance Switchbox Attachment: 2. Decade Box 3. Vacuum Tube Voltmeter (VTVM)

Battery Check of Impedance Converto~ 1. To be done at the beginning and end of each period of measurement 2. Disconnect switchbox 3. Turn knob to battery check 4. The dial should read between 30-50 OHMS 5. If the reading is less than this, the battery must be replaced before proceeding

Calibrating the Equipment To be done before and after each measurement (3 TRIALS = MEASUR EMENT) : 1 . Pl ug in VTVM 2. Attach a known precision resistor to the alligator clamps 3. Impedance Convertor a. Set on DC b. Set on 40 OHMS using balance switch c. Switch box on "patient II d. Align dots on gain knob 4. VTVM

a. Set at 8 OHMs using the II zero adjust II b. Set at DC+ c. Read OHMs on black AC/DC scale 93 5. Decade Box at 000000.0

6. Switch the impedance switch box to "POT." (With this change the Impedance Convertor will no longer read 40 and the VTVM will no longer read 8.)

7~ Using the Decade Box, the object is to simultaneously return the VTVM dial to 8 and the Impedance Convertor to 40. Step 1. Determine the whole number that is closest to balance without going over 40 or under 8. Step 2. Beginning with. 1, adjust the tenth knob until the two dials have reached their ori ginal positions. 8. The Decade Box readout should now match the known pre cision resistor within one-tenth of an OHM.

Determining Specimen and Container Temperature Using the Digitec Thermometer 1. After warm-up, check zero by rotating the function switch to zero position and turning the front panel zero control as necessary. 2. Probes--each probe cord is numbered and is to be used as follows: #1--#702 YSI probe is hung from the rings and into the urine bottle within 1 mm of the Ag-Ag-Cl electrode. -is to be plugged into its corresponding numbered slot on the thermometer. #2--#709 YSI probe is attached to the outside of the urine bottle. -is to be plugged into its corresponding numbered slot on the thermometer. #3--#702 YSI probe is unattached and is to be used to determine the temperature of the urine speci mens until they record ~20 degrees C. and are transferred to the urine bottle. 3. Probe Range-- Always use 0° - 100 0 C. 4. The function switch will take readings from probe slots 1,2 and 3 with a simple turn of the switch- thus, to obtain: 94

a. Specimen temperatures prior to test;ng~-select #3 on the function switch. b. Urine temperature in urine bottle, select #1 on the function switch. c. Container temperature--select #2 on the function switch. NOTE: The hundredth of a degree number will not stabilize, thus, you need to record any of the numbers you see flashing for this slot. 5. At the completion of each sample measurement, please check zero again--if the machine does not read zero when the function is set at zero, please note this in the comments and do not proceed with the data collec tion until the machine ;s checked. 6. The Digitec Thermister Thermometer will be calibrated every Monday-

Preparation of the Urine Impedance Box (UB) 1. The UB should be clean and dry. 2. One YSI #709 probe is taped securely to the outside of the UB. 3. Place the electrode plates into the UB. 4. Place the UB in the plastic jug. 5. The YSI #702 probe ;s anchored on the ring stand and is suspended in the urine bottle at the level of the Ag Ag-Cl electrodes. - should not be between the probes and should not be touching the sides of the US. 6. Surround the US with the styrofoam chips to the top of the UB. 7. Attach the electrode wires to the switch box. 8. Place the urine in the UB. 9. Wait five minutes prior to taking measurements and complete the measurements within a maximum time of six to eight minutes. 95

Measuring the Impedance of Human Urine 1. Once the urine specimen has reached room tempera ture, gently rotate the specimen container. Then, using a syringe, draw up 20 cc of urine. 2. Place urine into the prepared UB. 3. The actual measurement of impedance now proceeds as outlined in the calibration directions. 4. Three trials are taken simultaneously on each speci men. Each trial: a. Begins with switch box on patient; Decade Box on 000000.0; VTVM on 8; Impedance Convertor on 40. b. Ends with switch box on POT; VTVM on 8; Imped ance Convertor on 40; Decade Box giving reading. 5. If the measurements obtained in the three trials do not vary more than 0.1 OHM, remove the electrode plates, empty the urine, rinse the electrode plates and urine bottle with deionized water. 6. Calibrate the instrument again. (If you are measur ing another specimen, go back to #3.) 7. Place the photocopy of the lab results in the divider behind the data collection sheets.

Note. If any two of the three trials vary by more than 0.1 OHMs, operator error must be ruled out by: a. In the comments column of the data collection sheet, write repeat. b. On the next line, repeat all of the steps in data collec tion. c. If the complete repeat yields similar unstable results, do not continue until you have obtained assistance. APPENDIX K

SAMPLE DATA COLLECTION SHEET C I"C cc 0' 1 t..r> .. W N! - I Samp 1 f Number Identification Number I I II Sex Age i I I I ! I I I I I I I Date and Time I I I i j I ! I I i Oate and Time Co1lected

II ! I . 1\1 : I II , \ \ t, I, " Instrumen: Calibratec rlectrodes Calibrated

Abornmal U~ Results E!.-:- ri < ,..,.p, §' Meets Criteria? v: Room Temoerature OF

% "&.,::0 Hum; d ity Percent I I I i I Sample Temperatur € °C %-<% I I I o ~ c I I I i ;; Container Tempera ture "c i'j; I i "'l t't r, I C I I I "'I I Co I t'tc.. Trial #1 I

I: "T';:::t:l> i I Trial #2 :::: ;~:;: I ,.,-0 ~ ~;. - P, I~ I'!i "<- v. I~, !"<"1

I 1-'0 Ii Trilll #.3 :.::.

i I I Average I i I I I Corrments

i I I ! Used in Study I I I I I I I I j

L6 BIBLIOGRAPHY 99 Abbey, J. C. Impedance measurement of urinary bladder fullness. Salt Lake City, Utah: University of Utah, College of Nursing, 1978. (Unpublished Grant Application) American Society of Hospital Pharmacists. American hospital formu-, lary service. Washington, D.C.: American Society of Hospital Pharmacists, 1978. Belhea, D. C. Introductory maternity nursing. Philadelphia: J. B. Li pp i ncot t, Co., 1973.

Brown, B. H.; Pryce, W. I. J.; Baunber, D.; & Clark, R. G. Impedance plethysmography: Can it measure changes in limb blood flow. Medical and Biological Engineering, September 1975, 1l(5) , 674-682.

Brumfitt, W.; Davies, B. 1.; & Rosser, E. I. Urethral catheter as a cause of urinary tract infection in pregnancy and puerperium. Lancet, 1961, £, 1059. Cady, P. Rapid automated bacterial identification by impedance measurement. In C-G. Heden & I. Tibor (Eds.), New approaches for the identification of microorganisms. New York: John Wiley & Sons, 1975.

Cady, P.; Dufour, S. W.; Lawless, P., Nurke, B.; & Kraeger, S. J. Impedance screening for bacteriuria. Journal of Clinical MicrObiology, March 1978, 273-278. Castle, M. Urinary tract catheterization and associated infection Nursing Research, 1974, Q, 170-174. Chang, R. Physical chemistry with application to biological systems. New York: Macmillan Publishing Company, 1977. Clark, W. M. Topics in physical chemistry. Baltimore: The Williams and Wilkens Company, 1952. Cooley, W. L. & Lehr, J. L. Electrical impedance fluctuation as an indicator of fluid volume changes in a living organism. Bio medical Engineering, August 1972, I, 313-315. Danforth, D. N. (Ed.). Obstetrics and gynecology (3rd ed.). New York: Harper and Row, 1977. Decade Resistance Box, Model EU-30A, operator's manual. Benton Harbor, Michigan: Heath Company, 1969. Digitec Equipment Brochure. Dayton, Ohio: United Systems Corpora tion, 1978. 100 Denniston, J. C. & Baker, L. E. Technical note: Measurement of urinary bladder emptying using electrical impedance. Medical and Biological Engineering, March 1975, 12, 305-306. Doyle, P. T. & Hill, D. W. Technical note: The measurement of residual urine volume by electrical impedance in man. Medical and Biological Engineering, March 1975, 11, 307-308. Free, A. H. & Free, H. M. Urinalysis in clinical laboratory practice. Ohio: CRC Press, 1975. Garibaldi, R. A.; Burke, J. P., Dickman, M. L.; & Smith, C. B. Factors predisposing to bacteriuria during indwelling ure thral catheterization. New England Journal of Clinical In vestigation, 1974, 291, 215.

Geddes, L, A.; Baker, L. E.; Moore, A. G.; & Coulter, T. W. Hazards in the use of low frequencies for the measurement of physio logical events by impedance. Medical and Biological Engineer ~, 1968, 289-295. Geddes, L. A. & Baker, L. E. Principles of applied biomedical instru mentation (2nd ed.). New York: John ~'Ji1ey & Sons, 1975. Geddes, L. A. & Hoff, H. E. The measurement of physiological events by electrical impedance. American Journal of Medical Elec tronics, 1964, ~, 16-24. Geddes, L. A. & Sadler, C. The specific resistance of blood at body temperature. Medical and Biological Engineering, May 1973, ll, 336-339. Geddes, L. A. Electrodes and the measurement of bioelectric events. New York: Wi1ey-Interscience, 1972. Goggin, M. J. Urinary tract and renal consequences of pregnancy. Nursing r~irror, September 22, 1973, 145, 22-24. Guyton, A. C. Textbook of medical physiology (5th ed.). Philadel phia: W. B. Saunders Company, 1976.

Hill, R. V.; Jansen, J. C.; & Fling, J. L. Electrical impedance plethysmography: A critical analysis. Journal of Applied Physiology, January 1967, ~, 161-168. Hytten, F. & Leitch, I. The physiology of human pregnancy (2nd Ed.). London: Blackwell Scientific Publications, 1971.

Kark, R. ~~.; Lawrence, J. R.; Pollack, V. E.; Pirani, C. L.; Muehrcke, R. C.; & Silva, H. A primer of urinalysis (2nd ed.). New York: Harper & Row, 1963. 101 Karse1is, T. Descriptive medical electronics and instrumentation. New Jersey: Charles B. Slack, Inc., 1973. Kubicek, W. G.; Patterson, R. P.; & Witsoe, D. A. The impedance cardiograph as a noninvasive means to monitor cardiac func tions. NASA Report, No. NAS 9-4500, 1968. Malinowski, J. Bladder assessment in the post-partum patient. Journal of Obstetric and Gynecological Nursing, July-August 1978, ~, 16.

Mu11ick, S. C.; Wheeler, H. B.; & Songster, G. P. Diagnosis of deep vein thrombosis by measurement of electrical impedance. Ameri can Journal of Surgery, 1970, ~, 417-422. Nyboer, J. Electrical impedance plethysmography (2nd ed.). I 11 i no is: Ch a r 1esC . Thomas, 19 70 .

Nyboer, J.; Bagro, S.; Barrett, A.; & Halsey, R. H. Radiocardio gisms: Electrical impedance in relation to electrocardiograms and heart sounds. Journal of Clinical Investigation, September 1940, ~(5), 773. Nyboer, J. Electrorheometric properties of tissues and fluids. Annals of the New York Academy of Science, 1970, 170, 410. Pomerantz, M.; Delgado, F.; & Eisman, B. Clinical evaluation of transthoracic electrical impedance as a guide to intrathoracic fluid volumes. Annals of Surgery, May 1970, ill, 686-694. Pritchard, J. A. & MacDonald, P. C. Williams obstetrics. New York: App1eton-Century-Crofts, 1976. Reeder, S. R.; Fitzpatrick, E.; & Eastman, N. J. Maternity nursing. Philadelphia: J. B. Lippincott Co., 1976. Schanne, 0. T. & Ruiz-Ceretti, E. Impedance measurements in biological cells. New York: Wiley-Interscience, 1978. Sims, E. A. H. & Krantz, K. E. Serial studies of renal function during pregnancy and the puerperium in normal women. Journal of Clinical Investigation, 1978, [L, 1772.

Steer, M. L.; Spotnitz, A. J.; Coher, S. T.; Paulin, S.; & Salzman, E. W. Limitations of impedance phlebography for diagnosis of venous thrombosis. Archives of Surgery, January 1973, 06 44-48. Throm, R.; Spector, S.; Strauss, R.; & Griedman, H. Detection of bacteriuria by automated electrical impedance monitoring in a clinical microbiology lab. Journal of Clinical Microbiology, September 1977, 271-273. 102 Ur, A. & Brown, D. J. Monitoring of bacterial activity by impedance measurements. In C-G. Heden & I. Tibor (Eds.), New approaches to the identification of microorganisms. New York: John Wiley & Sons, 1975. Vacuum Tube Voltmeter, Model IM-28, assembly manual. Benton Harbor, Michigan: Heath Company, 1968.

Waltz, F. M.; Timm, G. W.; & Bradley, W. E. Bladder volume sensing by resistance measurement. ICEE Transactions on Bio-Medical Engineering, January 1971, ~(l). Weast, R. C. Handbook of chemistry and physics. Ohio: The Chemical Rubber Company, 1968. Williams, F. Reasoning with statistics. New York: Holt, Rinehart and Winston, Inc., 1968. Zafari, Y. & Martin, W. J. Comparison of BACTOMETER microbial moni toring system with conventional methods for detection of micro organisms in urine specimens. Journal of Clinical Microbio logy, May 1977, 545-547. VITA

Name Deanne Davis Roberts

Birthdate October 14, 1947 Birthplace Santa Fe, New Mexico High School Santa Fe High Santa Fe, New Mexico University University of New Mexico 1965-1969 Albuquerque, New Mexico 1972-1973 University of Northern Colorado Greeley, Colorado

Degree B. S., Nu rs i ng University of New Mexico Albuquerque, New Mexico Professional Organizations American Nurses Association Sigma Theta Tau Professional Positions Staff Nurse, Conejos County Hospital, La Jara, Colorado Staff Nurse, Boulder Community Hospital, Boulder, Colorado Instructor, Boulder Valley Public Schools, L.P.N. Program, Boulder, Colorado Instructor, College of Santa Fe, Department of Nursing, Santa Fe, New Mexico Staff Nurse, University of Utah Medical Center, Salt Lake City, Utah