sign in sign up
<<
Home , Dead space (physiology), Diffusing capacity

AARC GUIDELINE: CARBON MONOXIDE , 1999 UPDATE (replaces update published in January, 1999)

AARC Clinical Practice Guideline

Single-Breath Carbon Monoxide Diffusing Capacity, 1999 Update

DLCO 1.0 PROCEDURE DLCOsb is measured is also commonly report- Single-breath diffusing capacity for carbon monox- ed; the units for the VA are liters at body tem- ide (DLCOsb), sometimes referred to as the transfer perature and , saturated with water factor for carbon monoxide (TCO). vapor (BTPS). 2.3 The ratio of DLCO to VA is also commonly DLCO 2.0 DESCRIPTION/DEFINITION reported as the DL/VA or simply D/VA. The first American Association for Respiratory Care (AARC) single-breath diffusing capacity (DL- DLCO 3.0 SETTINGS: COsb) Clinical Practice Guideline (CPG) was pub- 3.1 Pulmonary function laboratories lished in 1993, and was based largely on the Ameri- 3.2 Cardiopulmonary laboratories can Thoracic Society (ATS) 1987 recommenda- 3.3 Clinics tions.1 Since that time, the ATS has published new 3.4 Physicians’ offices recommendations.2 This updated AARC CPG re- flects the 1995 ATS recommendations. Various DLCO 4.0 INDICATIONS: methods are commercially available to perform Tests of diffusing capacity may be indicated for DLCOsb. This Guideline can be applied in many (Specific conditions and direction of change in (perhaps most) cases and is based on experience DLCO are shown in the Appendix.): and research with the traditional method (10-sec- 4.1 evaluation and follow-up of parenchymal ond breathhold with alveolar sample collection). diseases including: idiopathic pulmonary For non-traditional or newer methods, it is the man- fibrosis (IPF, also known as usual interstitial ufacturer’s and the scientific community’s responsi- pneumonitis, or UIP) and bronchiolitis obliter- bility to define the comparability of the newer ans organizing pneumonia (BOOP, or crypto- methods with the old. genic organizing pneumonia, COP), diseases associated with dusts such as asbestos, or drug Diffusing capacity is a measurement of carbon reactions (eg,from amiodarone) or related to monoxide (CO) transfer from inspired gas to pul- ;1-3 and for quantification of disabili- monary blood. During the test, the subject ty associated with interstitial lung disease; 4 inspires a gas containing CO and oneRETIRED or more tracer 4.2 evaluation and follow-up of emphysema gases to allow determination of the gas exchanging and cystic fibrosis;5,6 and differentiating among capability of the . Although several different chronic bronchitis, emphysema, and in methods of measuring DLCO have been described, patients with obstructive patterns; and for quan- the most commonly used technique is the single- tification of impairment and disability. breath maneuver, or DLCOsb. For purposes of this 4.3 evaluation of cardiovascular diseases (eg, guideline, recommendations associated with the primary , acute or re- 2 DLCOsb are referenced. Many of these standards thromboembolism, or pulmonary apply indirectly to other methods of measuring dif- edema);7,8 fusing capacity. 4.4 evaluation of pulmonary involvement in 2.1 DLCO is usually expressed in mL CO min-1 systemic diseases (eg, rheumatoid arthritis, sys- . torr-1 at standard and pressure dry temic lupus erythematosus);9-11 (STPD). 4.5 evaluation of the effects of chemotherapy 2.2 The alveolar volume (VA) at which the agents or other drugs (eg, amiodarone,

RESPIRATORY CARE ¥ MAY 1999 VOL 44 NO 5 539 AARC GUIDELINE: CARBON MONOXIDE DIFFUSING CAPACITY, 1999 UPDATE

bleomycin) known to induce pulmonary dys- DLCO 7.0 LIMITATIONS OF METHODOLO- function;12-14 GY/VALIDATION OF RESULTS: 4.6 evaluation of pulmonary hemorrhage;15 7.1 Limitations of the common methods used 4.7 as an early indication of certain pulmonary for DLCO include: infections (eg, pneumocystis pneumonia);16 7.1.1 DLCO should be corrected for 4.8 prediction of arterial desaturation during (Hb) level according to the exercise in some patients with lung disease.17,18 method described by Cotes and co-work- ers.20 DLCO 5.0 CONTRAINDICATIONS 7.1.1.1 For adolescent boys(≥ 15 years 5.1 Absolute contraindications to performing a of age) and adult men, the Hb is adjust- diffusing capacity test are ed to a value of 14.6 g/dL: 5.1.1 the presence of carbon monoxide Hb-adjusted DLCO = observed DLCO (10.22 + toxicity Hb)/1.7 Hb. 5.1.2 dangerous levels of oxyhemoglobin 7.1.1.2 For children < 15 years of age desaturation without supplemental . and women the Hb is adjusted to a 5.2 Relative contraindications to performing a value of 13.4 g/dL: diffusing capacity test are Hb-adjusted DLCO = observed DLCO (9.38 + 5.2.1 mental confusion or muscular in- Hb)/1.7 Hb. coordination preventing the subject from 7.1.2 For purposes of interpretation, adequately performing the maneuver or DLCO should be corrected for the effects inability to obtain or maintain an ade- of COHb present in the subject’s blood.1 quate lip seal on the instrument mouth- COHb-adjusted DLCO = measured piece; DLCO (1+ [%COHb/100]). 5.2.2 a large meal or vigorous exercise 7.1.3 DLCO increases with increasing al- immediately before the test;1 titude and appropriate correction for the 5.2.3 within 24 hours of test ad- alveolar or inspired oxygen are ministration (smoking may have a direct recommended.1 effect on DLCO independent of the effect Altitude-adjusted DLCO = measured 19 of COHb ); DLCO (1.0 + 0.0035(PAO2 - 120]) 5.2.4 decreased that would or not yield valid test results; Altitude-adjusted DLCO = measured 5.2.5 devices that are improperly calibrat- DLCO (1.0 + 0.0031(PIO2 - 150]) ed or maintained or the unavailability of a (where estimated PIO2 = 0.21 [PB - 47 qualified operator. torr].) 7.1.4 A 4-minute minimum interval DLCO 6.0 /COMPLICATIONS: should elapse between subsequent ma- 6.1 DLCO requires breathholdingRETIRED at total lung neuvers to allow test gas to be eliminated sb capacity (TLC); some patients may perform ei- from the lungs.1 ther a Valsalva (higher than normal intratho- 7.1.5 DLCO varies with body position; racic pressure) or Müller (lower than normal in- the upright seated position is recommend- trathoracic pressure) maneuver. Either of these ed. can result in alteration of venous return to the 7.1.6 Abnormal breathholding maneuvers heart and pulmonary capillary blood volume. (Valsalva or Müller) alter DLCO.21 6.2 Interruption of supplemental oxygen may 7.1.7 Other factors that may alter measure- result in oxyhemoglobin desaturation. ment of DLCO include recent alcohol con- 6.3 Transmission of infection is possible via sumption,22 vigorous exercise, smoking, improperly cleaned mouthpieces or as a conse- diurnal variation, and .23 quence of the inadvertent spread of droplet nu- 7.1.8 Pregnancy (first trimester only) has clei or body fluids (patient-to-patient or patient- been reported to be associated with an in- to-technologist). crease in DLCO.24 Menstruation may also

540 RESPIRATORY CARE ¥ MAY 1999 VOL 44 NO 5 AARC GUIDELINE: CARBON MONOXIDE DIFFUSING CAPACITY, 1999 UPDATE

influence DLCO.25 valve and circuit (if a compressed gas 7.1.9 Breathhold time should be calculat- source is used). 2 ed using the method of Jones-Meade. 7.4.7 Chemical absorbers (for CO2 and Other methods may produce significantly H2O) or selectively permeably tubing different results. should be replaced at the frequency rec- 7.2 Large interlaboratory differences in mea- ommended by the manufacturer, when sured DLCO and in percent-of-predicted saturated (as indicated by color change) or DLCO have been observed 26,27 and are attribut- sooner. In addition, the chemical ab- ed to variations in testing techniques and com- sorbers should be placed in the proper putational algorithms and errors in gas analysis. order (ie, CO2 absorber should precede The choice of equipment may also influence H2O absorber), should be replaced when the measured DLCO.27,28 exhausted, and should be arranged ac- 7.3 Choice of reference equations may affect the cording to how alveolar gas is analyzed. final interpretation of measured DLCO values.29 7.4.8 Normal standard subjects (biologic 7.4 Validation of the testing technique and controls) may be used to establish intra- equipment may include but is not limited to subject coefficient of variation and to 7.4.1 Volume accuracy of spirometer serve as a quality control population.2 should be < ± 3% over an 8-L volume (ie, meets or exceeds all ATS recommenda- DLCO 8.0 ASSESSMENT OF NEED (see Sec- tions2) and must be checked each day that tion 4.0 Indications) the test is performed, using a 3.00 L (min- imum) syringe. Spirometer must maintain DLCO 9.0 ASSESSMENT OF TEST QUALITY: accuracy with varying gas . Individual test maneuvers and results should be 7.4.2 Gas analyzers should be subjected to evaluated according to the ATS recommendations.2 a 2-point calibration before each test. 9.1 Use of proper quality-controlled equipment. Manufacturers should be encouraged to 9.2 Provision of test instructions before testing provide software and techniques by which commences and determination that the subject analyzer linearity may be easily checked is able to follow commands. (eg, dilution technique). Gas analyzer lin- 9.3 Inspiratory volume exceeding 90% of the earity should be largest previously measured 7.4.2.1 within ± 1%, from zero to (FVC or VC), attained in < 2.5 s in healthy sub- full span, of maximal value over the jects and within 4 s in patients with moderate to duration of the test, severe airway obstruction. 7.4.2.2 formally checked at least 9.4 Breathhold times of 9-11 seconds, with no quarterly.30 evidence of leaks or Valsalva or Müller maneu- 7.4.3 Timing device should be checked vers. every 3 months30 and be accurateRETIRED within ± 9.5 After the breathhold, there should be appro- 1% over a 10-second period. priate clearance of (anatomic plus 7.4.4 The entire circuit resistance should system) and proper collection and analysis of be < 1.5 cm H2O/L/s at a flow of 6 L/s. alveolar gas. The addition of in-line filters may cause 9.5.1 The washout volume (ie, dead the circuit resistance to exceed recom- space) should be 0.75-1.00 L or 0.50 L if mendations. the subject’s VC is less than 2.0 L. If a 7.4.5 The apparatus dead space should be washout volume other than 0.75-1.00 L < 0.1 L. In-line filters need to be account- must be used, it should be noted. ed for when determining entire system 9.5.2 If an in-line filter is used, when de- dead space as well as discard volume (be- termining discard volume, the filter dead fore alveolar collection). space must be accounted for. 7.4.6 Demand valve sensitivity of < 10 cm 9.5.3 For alveolar-gas sample-bag sys- H2O is required for 6 L/s flow through a tems, the volume of the alveolar gas sam-

RESPIRATORY CARE ¥ MAY 1999 VOL 44 NO 5 541 AARC GUIDELINE: CARBON MONOXIDE DIFFUSING CAPACITY, 1999 UPDATE

ple should be 0.5-1.0 L obtained in < 4 II individual or a physician. seconds. 10.2.2 Level II: Personnel supervising 9.6 Two or more acceptable tests should be av- DLCO testing should have formal educa- eraged; the DLCO values should be repro- tion and training (as a part of a program in ducible to within 10% or 3 mL CO . min -1 . torr -1, respiratory therapy or pulmonary function whichever is greater. We recommend empirically technology or 2 years of college in biolog- that no more than 4-6 maneuvers be performed. ical sciences and mathematics) and 2 or 9.7 The subject should have refrained from more years performing , lung smoking for 24 hours prior to the test; however, volumes, and diffusing capacity tests.31 because subjects do not always comply, the One or more of the following credentials time of the last smoking event should be is recommended: RPFT, CPFT, RRT, recorded. CRT. 9.8 Corrections for Hb, COHb should be in- cluded as noted above (Sections 7.1.1 and DLCO 11.0 MONITORING: (Also see Section 7.1.2); correction for tests performed at altitude 9.0 Assessment of Test Quality) is recommended. If Hb correction is made, both The following should be evaluated during the per- the corrected and uncorrected DLCO values formance of the DLCO measurement to assess the should be reported. validity of the results: 11.1 Acceptability of the maneuvers and repro- DLCO 10.0 RESOURCES ducibility of DLCOsb: 10.1 Equipment: 11.1.1 patient positioning: subjects should 10.1.1 Volume-measuring device must be seated for at least 5 minutes prior to meet or exceed ATS recommendations. testing and should remain seated through- 10.1.2 Appropriate gas analyzers depen- out the DLCO testing session, dent on the methodology employed; certi- 11.1.2 interval between tests: at least 4 fied calibration gases for use before each minutes between sequential tests to allow series of measurements. elimination of tracer gas, 10.1.3 COoximeter for analysis of total 11.1.3 reproducibility, with at least 2 ac- Hb and COHb is strongly recommended. ceptable tests that are within ± 10% or 3 10.2 Personnel: Diffusing capacity tests should mL CO(STPD)/min/mm Hg of the aver- be performed under the direction of a physician age DLCO. trained in pulmonary function testing. The 11.2 Level of understanding (of test instruc- value of diffusing capacity results can be com- tions), effort and cooperation by the subject. promised by poor patient instruction secondary 11.3 Equipment function or malfunction (eg, to inadequate technologist training. Thus, tech- calibration), with equipment quality control nologists should have documented training, performed as recommended, any time accuracy with continued competency assessmentsRETIRED in dif- is suspect or if the equipment is moved to a dif- fusing capacity administration and recognition ferent location. of errors encountered in the testing process as 11.3.1 Volume calibration and leak testing well as a sound understanding of pulmonary performed on a daily basis, pathophysiology. Diffusing capacity testing 11.3.2 Gas analyzer linearity checked may be performed by persons who meet criteria quarterly, for either Level I or Level II. 11.3.3 Timer tested quarterly 10.2.1 Level I: The technologist perform- 11.3.4 Tests on standard subjects (biologic ing DLCO should be a high school gradu- controls, or bio-QC)should be performed ate or equivalent with a demonstrated abil- at least on a quarterly basis and any time ity to perform basic pulmonary function accuracy is suspect.2 studies such as spirometry (and DLCOsb). 11.3.4.1 Standard subjects should be Level I personnel should perform DLCO tested more frequently initially to estab- tests only under the supervision of a Level lish statistical variation for comparison.

542 RESPIRATORY CARE ¥ MAY 1999 VOL 44 NO 5 AARC GUIDELINE: CARBON MONOXIDE DIFFUSING CAPACITY, 1999 UPDATE

11.3.4.2 It is advantageous to perform cautions empirically for airborne, droplet, and con- Bio-QC at weekly or semi-monthly in- tact agents pending confirmation of diagnosis in pa- tervals.32 tients suspected of having serious infections.33 11.4 Reference equations: each laboratory 13.2 Proper use of barrier devices (eg, protec- should select reference equations appropriate tive gloves) may be useful to prevent spread of for the methods and the population tested. contagion via direct contact. Hand washing 11.5 Inspired oxygen : test gas must always be performed between patients, concentration should be 20.93% and at sea and protective gloves must be worn if there are level pressure. Subjects should remain off sup- open cuts, or sores, on the technologist’s plemental oxygen for at least 5 minutes prior to hands.2 performing the first test. Technologists should 13.3 Due to the nature of the DLCO maneuvers document (in the final report)a patient’s inabili- and the likelihood of coughing when the test is ty to remain off supplemental oxygen for the al- performed by subjects with known or suspected lotted time. active infection with Mycobacterium tubercu- 11.6 The final report should contain a statement losis or other airborne organisms, recommend- about test quality. ed precautions are:34 11.7 The final report should contain the DLCO, 13.3.1 The room in which the DLCO test the corrected DLCO (Hb, COHb, altitude), and is performed should meet or exceed the the Hb value used for correction. The alveolar recommendations of U.S. Public Health volume (VA) and DL/VA (ie, the ratio of diffus- Service33,35 for air changes and ventilation. ing capacity to the lung volume at which the The ideal situation is to establish an area measurement was made) may be included in in the testing department specially venti- the report. These values are helpful for purpos- lated for isolation patients. We strongly es of interpretation. The final report should in- recommend that, if this is not possible, the dicate which method was used to correct the patient be returned to the isolation room raw DLCO value and for what the DLCO value as soon as possible, and the testing room is being corrected [eg, corr DLCO (Hb), corr be closed for a minimum of 1 to 2 hours. DLCO (CO)]. 13.3.2 Pulmonary function technologists 11.8 DLCOsb results should be subject to ongo- performing procedures on patients with ing review by a supervisor, with feedback to the potentially infectious airborne diseases technologist. Quality assurance (QA) and/or should wear a personal respirator that quality improvement (QI) programs should be meets OSHA recommendations, especial- designed to monitor the technologist both ini- ly if the testing itself induces coughing.35 tially and on an ongoing basis. 13.4 The mouthpiece, tubing, and any parts of the system that come into contact with the sub- DLCO 12.0 FREQUENCY: ject should be disposable or sterilized between The frequency at which DLCO RETIREDmeasurements patients. If sterilization is not feasible, then should be repeated depends on the clinical ques- high-level disinfection should be performed. It tion(s) to be answered. is unnecessary to routinely clean the interior surface of the spirometer. DLCO 13.0 INFECTION CONTROL: 13.4.1 Visible condensation, from expi- Diffusing capacity tests are relatively safe proce- rate, warrants cleaning of the system be- dures, but the possibility of cross-contamination ex- fore testing another patient. ists, either from the patient-patient or patient-tech- 13.4.2 Bacterial filters that allow re- nologist interface.33 may be used in circuit, although 13.1 Technologists should exercise Standard Pre- their efficacy is not well documented. cautions for all patients, follow recommendations However, such filters may impose added of the Centers for Disease Control and Prevention resistance during inspiration or expiration for control of exposure to tuberculosis and droplet and affect the timing of the DLCO ma- nuclei, and, in addition, institute appropriate pre- neuver. If a filter is used, the filter dead-

RESPIRATORY CARE ¥ MAY 1999 VOL 44 NO 5 543 AARC GUIDELINE: CARBON MONOXIDE DIFFUSING CAPACITY, 1999 UPDATE

space volume should be considered in the with bleomycin-containing combination chemotherapy. Cancer Chemother & Pharmacol 1993;32:407-409. calculation of DLCO and VA. 15. Crapo RO, Forster RE 2nd. Carbon monoxide diffusing ca- pacity. Clin Chest Med 1989;10(2):187-198. Capacity Working Group 16. Mitchell DM, Fleming J, Pniching AJ, Harris JR, Moss FM, Veale D, Shaw RJ. Pulmonary function in human Carl Mottram RRT RPFT, Chairman, Rochester MN immunodeficiency virus infection; a prospective 18- month study of serial lung function in 474 patients. Am Susan Blonshine BS RRT RPFT, Mason MI Rev Respir Dis 1992;146:745-751. Robert A Brown BS RRT RPFT, Waunakee WI 17. Owens GR, Rogers RM, Pennock BE, Levin D. The diffus- Gregg L Ruppel MEd RRT RPFT, St Louis MO ing capacity as a predictor of arterial oxygen desatura- Jack Wanger MBA RRT RPFT, Lenexa KS tion during exercise in patients with chronic obstructive pulmonary disease. N Engl J Med 1984;310:1218-1221. REFERENCES 18. Nordenfelt I, Svensson G. The transfer factor (diffusing ca- pacity) as a predictor of hypoxaemia during exercise in 1. American Thoracic Society. Single breath carbon monoxide restrictive and chronic obstructive pulmonary disease. diffusing capacity (transfer factor): recommendations Clin Physiol 1987;7:423-430. for a standard technique. Am Rev Respir Dis 19. Sansores RH, Pare PD, Abboud RT. Acute effect of 1987;136:1299-1307. cigarette smoking on the carbon monoxide diffusing ca- 2. American Thoracic Society. Single breath carbon monoxide pacity of the lung. Am Rev Respir Dis 1992;146(4):951- diffusing capacity (transfer factor): recommendations 958. for a standard technique—1995 update. Am J Respir 20. Cotes JE. Lung function: assessment and application in Crit Care Med 1995;152;2185-2198. medicine, 4th ed. Oxford: Blackwell Scientific Publica- 3. Weinberger SE, Johnson TS, Weiss ST. Clinical signifi- tions, 1979:203,329. cance of pulmonary function tests: use and interpretation 21. Smith TC, Rankin J. Pulmonary diffusing capacity and the of the single-breath diffusing capacity. Chest capillary bed during Valsalva and Müller maneuvers. J 1980;78:483-488 Appl Physiol 1969;27:826-833. 4. Epler GR, Saber FA, Gaensler EA. Determination of severe 22. Peavy HH, Summer WR, Gurtner G. The effects of acute impairment (disability) in interstitial lung disease. Am ethanol ingestion on pulmonary diffusing capacity. Rev Respir Dis 1980;121:647-659. Chest 1977;4:488-492. 5. Ogilvie C. The single-breath carbon monoxide transfer test 23. Lawson WH. Effect of drugs, , and ventilatory ma- 25 years on: a reappraisal. 2. Clinical considerations (ed- neuvers on lung diffusion for CO in man. J Appl Physiol itorial). Thorax 1983;38:5-9. 1972;32:788-794. 6. Morris AH, Kanner RE, Crapo RO, Gardner RM. Clinical 24. Milne JA, Mills RJ, Coutts JRT, MacNaughton MC, Moran pulmonary function testing: a manual of uniform labora- F, Pack AI. The effect of human pregnancy on the pul- tory procedures, 2nd ed. Salt Lake City: Intermountain monary transfer factor for carbon monoxide as measured Thoracic Society, 1984. by the single breath method. Clin Sci Mol Med 7. Knudson RJ, Kaltenborn W, Burrows B. Single breath car- 1977;53:271-276. bon monoxide transfer factor in different forms of 25. Sansores R, Gibson N, Abboud R. Variation of pulmonary chronic airflow obstruction in a general population sam- CO diffusing capacity (DLCO) during the menstrual ple. Thorax 1990;45:514-519. cycle (abstract). Am Rev Respir Dis 1991;143(4, Part 8. Light RW, George RB. Serial pulmonary function in pa- 2):A759. tients with acute . Arch Intern Med 26. Clausen J, Crapo R, Gardner RM. Interlaboratory compar- 1983;143:429-43. RETIREDisons of pulmonary function testing (abstract). Am Rev 9. Gibson GJ, Edmunds JP, Hughes GRV. Diaphragm function Respir Dis 1984;129(4, Part 2):A37. and lung involvement in systemic lupus erythematosus. 27. Wanger J, Irvin C. Comparability of pulmonary results Am J Med 1977;63:926-932. from 13 laboratories in a metropolitan area. Respir Care 10. Gross M, Esterly JR, Earle RH. Pulmonary alterations in 1991;36:1375-1382. systemic lupus erythematosus. Am Rev Respir Dis 28. Hathaway EH, Tashkin DP, Simmons MS. Intra-individual 1972;105:572-577. variability in serial measurements of DLCO and alveolar 11. Frank ST, Weg JG, Harkeroad LE, Fitch RF. Pulmonary volume over one year in eight healthy subjects using dysfunction in rheumatoid disease. Chest 1973;63:27-34. three independent systems. Am Rev Respir Dis 12. Comis RL. Bleomycin pulmonary toxicity: current status and 1989;140:1818-1822. future directions. Sem Oncol, 1992;19(Suppl 5):64-70. 29. Crapo RO, Gardner RM. DLCO reference equations: a per- 13. Abratt RP, Wilcox PA. The effect of irradiation on lung spective (editorial). Am Rev Respir Dis 1986;134:856. function and in patients with lung cancer. In- 30. American Thoracic Society. Quality assurance in pul- ternat J Radiol Oncol Biol Phys 1995;31:915-919. monary function laboratories. (position paper). Am Rev 14. Ngan HY, Liang RH, Lam WK, Chan TK. Pulmonary toxi- Respir Dis 1986;134:625-627. city in patients with non-Hodgkins lymphoma treated 31. American Thoracic Society. Pulmonary function laboratory

544 RESPIRATORY CARE ¥ MAY 1999 VOL 44 NO 5 AARC GUIDELINE: CARBON MONOXIDE DIFFUSING CAPACITY, 1999 UPDATE

personnel qualifications. Am Rev Respir Dis Committee, Centers for Disease Control and Prevention. 1986;134(3):623-624. Guidelines for Isolation Precautions in Hospitals. At- 32. American Thoracic Society. Pulmonary function laboratory lanta GA: Centers for Disease Control and Prevention, management. Wanger J, Crapo RO, Irvin CG, editors. 1-01-1996. www.cdc.gov American Thoracic Society 1998. 35. Centers for Disease Control & Prevention. Guidelines for 33. Tablan OC, Williams WW, Martone WJ. Infection control preventing the transmission of Mycobacterium tubercu- in pulmonary function laboratories. Infect Control losis in health-care facilities. Washington DC: Federal 1985;6:442-444. Register 1994;59(208), Friday Oct 28, 1994: 54242- 34. Garner JS, Hospital Infection Control Practices Advisory 54303. www.cdc.gov

Appendix Follows

RETIRED

RESPIRATORY CARE ¥ MAY 1999 VOL 44 NO 5 545 AARC GUIDELINE: CARBON MONOXIDE DIFFUSING CAPACITY, 1999 UPDATE

APPENDIX

Factors that Result in a Decrease in DLCO

Factor Condition Giving Rise to Factor

Deficiency in red blood cells Loss of pulmonary capillary bed with relatively Multiple pulmonary emboli, early collagen-vascu- normal lung volume lar disease, early sarcoidosis, miliary tuberculosis

Loss of functioning alveolar-capillary (A-C) bed Emphysema with increased lung volume

Loss of functioning A-C bed with decreased lung Parenchymal restrictive processes including pul- volume monary resection, idiopathic interstitial fibrosis, as- bestosis, scleroderma lung disease, histiocytosis-X, sarcoidosis, pneumonia

Failure of inspired air to reach alveoli, or poor dis- Seen occasionally with severe obstruction during tribution of ventilation with low, normal or in- asthmatic or bronchitic attack; seen frequently with creased lung volume emphysema and poor effort

Factors that Result in an Increase in DLCO

Factor Condition Giving Rise to Factor

Increase in pulmonary capillary blood volume Left heart failure, left-to-right shunt (atrial septal de- fect, anomalous pulmonary venous return), exercise

Increase in red blood cells Early

Specific Abnormalities Leading to an Increase in DLCO*

Abnormality Precipitation Condition Lung compression RETIREDScoliosis, , pectus excavatum Increased Asthma, cystic fibrosis, central airway lesions

Pulmonary vascular congestion Congestive heart failure, regurgitative valvular disease Intrapulmonic hemorrhage Pulmonary hemosiderosis, Goodpasture’s syndrome, hemothorax ‘Physiologic’ leaks

*The clinician should be suspicious if a patient with any of the abnormalities and/or precipitating condition listed proves to have a normal diffusing capacity.

Interested persons may photocopy these Guidelines for noncommercial purposes of scientific or educational advancement. Please credit AARC and RESPIRATORY CARE Journal.

546 RESPIRATORY CARE ¥ MAY 1999 VOL 44 NO 5