Blood Pressure Measurement PhDr. Mária Sováriová Soósová, PhD. Training for Students 1. – 15. September 2019 UPJŠ, Košice, Slovakia Blood Pressure Blood pressure may be defined as the force of blood inside the blood vessels against the vessel walls. (Marieb and Hoehn, 2010 according to Dougherty, L., Lister, S., 2015) Blood pressure Systolic BP – is the peek pressure of the left ventricule contracting and blood entering the aorta, causing it to strech and there for in parts reflects the function of the left ventricule. Diastolic BP – is when the aortic valve closes, blod flows from the aorta into the smaller vessels and the aorta recoils back. This is when the aortic pressure is at its lowest and tends to reflect the resistance of the blood vessels. (Marieb and Hoehn, 2010 according to Dougherty, L., Lister, S., 2015) Factors influencing BP Age Gender Race Anxiety, fear, pain, emotional stress Medications Hemorrhage Increased intracranial pressure Hormones Diural rhythm Obesity Eating habits Exercise Smoking .......... Aerage and upper limits of blood pressure according to age in mmHg Age Average normal BP Upper limits of normal BP mm Hg mm Hg 1 year 95/65 undetermined 6 – 9 yrs. 100(105)/65 119/79 10 – 13 yrs. 110/65 124/84 14 – 17 yrs. 120/ (75)80 134/83 18 + yrs. 120/80 139/89 Classification of Hypertension ESC/ESH classification of office blood pressurea and definitions of hypertension gradeb (Williams, Mancia, Spiering, et al. 2018, p. 3030) Category Systolic (mmHg) Diastolic (mmHg) Optimal <120 and <80 Normal 120–129 and/or 80–84 High normal - prehypertension 130–139 and/or 85–89 Grade 1 hypertension 140–159 and/or 90–99 Grade 2 hypertension 160–179 and/or 100–109 Grade 3 hypertension ≥180 and/or ≥110 Isolated systolic hypertensionb ≥140 and <90 Methods of BP measuring Invasive - direct: direct in an artery continuous monitoring Noninvasive – indirect: Auscultation – Korotkoff sounds. Palpation – systolic BP Automatic BP by auscultation Equipment Sphygmomanometer – aneroid, mercury or alcohol column Pressure cuff appropriate in size Stethoscope Alcohol swab Pen, sheet or electronic health record Factors influencing BP measurement outcomes Environment (noise, talking, temperature, light) Patient´s position Siting on exam. table, crossed legs, unsupported arm, forearm under or above heart, constrictive clothing, Patient´s condition hard physical activity, exercise (2 – 3 h. rest before meas.), smoking, caffeine (30 min), alcohol, distended urinary bladder, stress, disease, ... Cuff size, cuff applied too loosely or too tight, midline of bladder not on brachial a., cuff wrapped over clothing, slow or inconsistent cuff inflation, fast cuff deflation, integrity of cuff, ... Stethoscope bell placed under cuff or near tubing, stethoscope applied too firmly Device accuracy, maintaining and calibrating equipment Factors Affecting Accuracy of Blood Pressure Measurements Factor Magnitutde of systolic/diastolic blood pressure discrepancy SBP/DBP (mmHg) Talking or active listening 10/10 Distended bladder 15/10 Cuff over clothing 5-50/unknown Smoking within 30 minutes of measurement 6-20/unknown Back unsupported 6-10/unknown Arm unsupported, sitting 1-7/5-11 Arm unsupported, standing 6-8/unknown Cuff size Arm Circumference (cm) Cuff Size (cm) 7 Up to 10 4 × 8 newborn 7 >10 to 1 5 6 × 12 infant 7 15 to 22 9 × 18 child 4 22 to 26 12 × 22 small adult 4 27 to 34 16 × 30 adult (standard) 4 35 to 44 16 × 36 large adult 4 45 to 52 16 × 42 adult thigh Contraindactions Peripherally Inserted Central Catheters in upper arm Dialysis shunt or fistula Lymphedema Injury Inflammation ... Blood Pressure Measurement Procedure Patient Preparation 1. Ask if the patient avoided caffeinated beverages and smoking for at least 30 minutes before the examination. 2. Have the patient sit calmly for five minutes with back supported and feet flat on the floor. 3. Patient’s upper arm should be bare. Avoid a tourniquet effect if rolling up sleeve. 4. Support the patient’s arm on a firm surface at heart level, slightly flexed at the elbow. 5. Both you and the patient should refrain from talking while BP is measured. Blood Pressure Measurement Procedure Positioning Recommended “Ideal” Cuff Sizes for Newborns, Sphygmomanometer and Infants, Children, and Adults4,7 Cuff Use appropriate cuff size. Arm Cuff Size (cm) Circumference The inflatable part should (cm) be long enough to encircle 7 at least 80% of the arm and Up to 10 4 × 8 newborn 7 wide enough to encircle >10 to 1 5 6 × 12 infant 40% of the arm at 7 midpoint. 15 to 22 9 × 18 child 4 When in doubt, select the 22 to 26 12 × 22 small adult 4 larger size. 27 to 34 16 × 30 adult (standard) 4 35 to 44 16 × 36 large adult 4 45 to 52 16 × 42 adult thigh 2. Wrap the cuff snugly around bare upper arm. The lower edge should be centered two finger widths above the bend of the elbow, and the midline of the bladder should be over the brachial artery pulsation. 3. The aneroid dial or mercury column should be clearly visible and facing you. 4. Using light pressure, position stethoscope with bell side down over brachial artery and not touching the cuff. Estimate systolic pressure Palpate radial artery. Inflate the cuff slowly to the point where the pulse disappears. This is the systolic pressure. Rapidly inflate the cuff to 30 mmHg above the estimated systolic pressure. Deflate cuff at a steady rate of 2 to 3 mmHg/sec. Blood Pressure Reading Note the systolic pressure — the first of 2 or more consecutive faint tapping beats (Korotkoff sound phase 1). Note diastolic pressure—the last muffled, rhythmic sound (Korotkoff sound phase 5). The absence of a tapping sound after the initial sound is known as an auscultatory gap. If this occurs, elevate subject’s arm overhead for 30 seconds then bring arm to usual supported position to re-measure. Listen for another 10 to 20 mmHg beyond the last sound heard, then quickly deflate cuff to zero. Recheck and Record If record system allows, record this BP, rounding up to the nearest 2 mmHg. Wait 1 minute and recheck BP. If record system allows, record this BP. Average the BP readings and record the average; however, if the first two readings differ by more than 5 mmHg, then take a third measurement and average the three. Record blood pressure classification and recommendations for follow-up of patients at various stages of hypertension. Communicate to patient verbally and in writing the BP goal for their treatment, their specific BP numbers, and when they should be monitored next. Do not dismiss or minimize to the patient the significance of a borderline reading. If appropriate, discuss medical treatment and lifestyle approaches to preventing and treating high BP. For First Examination Obtain 2 readings in each arm, waiting at least 1 minute between readings. If the readings consistently differ, the arm with the higher pressure should be used for this and subsequent examinations. For Subsequent Examinations Refer to the patient’s chart to determine which arm had the higher reading on the first examination. Obtain 2-nd BP readings in that arm, waiting at least 1 minute between readings. If the readings differ by less than or equal to 5 mmHg, then the readings should be averaged and recorded. If the readings differ by more than 5 mmHg, then at least one additional reading should be taken and all the readings should be averaged and recorded. For All Measurements Round up to the nearest 2 mm Hg. Record the average as soon as practical. If the charts or electronic health records allow, record the individual measurements and the averages. Also record patient’s cuff size, and the position (e.g., standing, seated, supine) and which arm was used. Most Common Sources of Error in Blood Pressure Measurement Technique Cuff size and application Arm position Differences in arm size Rest period prior to measurement Inflation/deflation method Concentration of the measurer Lack of repeated measures Time between repeated measures Lack of calibration/maintenance of measurement devices Body position Muscle tension Quality of stethoscope Level of training of measurer Forearm measurement of blood pressure – circumstance of forearm > 50 cm, auscultation of Korotkoff sounds over the radial artery or using a Doppler also can be done. Cardiac dysrhythmias – to take the average of more than one measurement, Pregnancy – Blood pressure tends to decrease early in gestation and frequently is 10 mm Hg below pre-pregnancy levels. The mean blood pressure in the second trimester is 105/60 mm Hg. The decline in blood pressure is due to peripheral vasodilatation the causes of which are not clearly understood For patients with sounds not audible per auscultation (e.g., those with weak Korotkoff sounds), a Doppler probe can be used over the brachial artery to determine the patient's systolic pressure. Assessing BP in both arms For the initial assessment, measure BP on both arms, especially if the patient has heart cardiac disease or if the reading in the first arm is abnormal. Normally, a difference of 5 to 10 mm Hg exists between the arms. In subsequent assessments, the BP should measured in the arm with the higher BP. Pressure differences higher than 10 mm Hg indicate conditions such as aortic stenosis or an arterial occlusion in the arm with the lower pressure. Alternative sites/methods BP in the lower extremities prone position is the best when it is not possible – supine position with slightly elevated knee membrane of statoscope place on posterior popliteal artery Systolic BP in the lower extremities is usually higher by 10 to 40 mm Hg than in the brachial artery, Diastolic BP is essentially the same.