ATS Pulmonary Function Laboratory Manual

ATS Pulmonary Function Laboratory Management & Procedure Manual | 3rd Edition

Test Procedure

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Step Action 9.

Perform at least two acceptable maneuvers that agree within 2 ml/min/mm Hg (0.67 mmol/min/kPa) of each other. 10. At least 4 minutes should be allowed between each test maneuver for classical systems. For rapid gas analyzer systems, washout may be complete when the end-expiratory tracer gas concentration is <2% of the tracer gas concentration in the test gas, which may take less than 4 minutes.

Review of Test Results 1.

Individual test maneuvers are considered acceptable if: 1.1.

Properly quality controlled instrumentation was used.

1.2. Inspired volume of test gas (Vi) was at least 90% of largest VC measured in the same pulmonary function test session, and 85% of the Vi was inspired within 4 seconds. 1.3. A stable calculated breath-hold time of 10 ±2 seconds (8 to 12 seconds). 1.4. No evidence of leaks or Valsalva or Mueller maneuvers during the breath hold. 1.5. The appropriate clearance of dead space during the exhalation after the breathhold. Note: tests outside the limits set in 1.3–1.5 may still have clinical utility, but deviations from the standard acceptability criteria should be noted and possible impact considered. 2. Assure that anatomical and mechanical dead space are cleared before the alveolar sample is collected. With classi- cal systems, dead space washout volume should be 0.75 to 1.0 L (7). If a patient’s VC is less than 2.0 L, the washout volume may need to be reduced to 0.5 L. Sample volume is 50–100 ml (or less than 50 ml if VC is less than 2.0 L). Using a rapid gas analyzer with visual display, these washout and sample volumes can be manually adjusted using the phase 2 to phase 3 transition of the tracer gas concentration to assure an appropriate sample for analysis. 3. Assure that there were at least 4 minutes between maneuvers for classical systems, or for rapid gas analyzer systems washout may be complete in less than 4 minutes and the end-expiratory tracer gas concentration should be <2% of the tracer gas concentration in the test gas. 4. Assure that at least two acceptable maneuvers have been performed. 5. Assure that the Jones-Mead method (11) of calculating breath hold time was used. See Figure 10.1. 6. Assure between maneuver repeatability criteria has been met. The repeatability criteria is at least two accept- able maneuvers agree within 2 ml/min/mm Hg (0.67 mmol/min/kPa) of each other. 7. Adjustments for Hb, COHb, and inspired Po 2 should be made prior to interpretation. Hb correction should use the equations of Cotes ( see Appendix 1) (12). Reporting of Test Results 1. The average of at least two acceptable maneuvers that meet the repeatability requirement should be reported (i.e., outliers need to be excluded) (7). 2. The report should always include (7): 2.1. Measured uncorrected Dl CO and Kco (the use of the term Dl CO /VA is discouraged) 2.2. Measured Dl CO adjusted for barometric pressure 2.3. Predicted Dl CO and Kco with the lower limit of normal and z-score 2.4. Percent predicted Dl CO and Kco

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