ATS Pulmonary Function Laboratory Manual

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

Test Procedure for SVC

Step Action 1. Immediately after the FRC measurement and without coming off the mouthpiece, instruct the patient to slowly expire as much as possible (ERV maneuver). 2. Instruct the patient to inhale completely (an Inspired Vital Capacity). 3. For patients with severe obstructive dysfunction or severe dyspnea who are unable to follow the FRC measurements with a “linked” ERV maneuver, instruct the patient to take a deep breath (IC maneuver). 4. The patient may come off the mouthpiece between successive “linked” FRC and IC determinations and also between the separate VC maneuvers needed to calculate RV. Review of Test Results 1. Final review of data on report should be checked for accuracy and completeness by the individual perform- ing the testing, and/or by the laboratory manager or supervisor. 2. The accuracy of the final report in the hospital information system should be checked periodically. Reporting of Test Results 1. Static lung volumes are expressed in liters (L) and reported at body temperature and pressure saturated with water vapor (BTPS). 2. The average FRC value should always be reported (ideally including the variability) with the method used to derive the value (e.g., FRC pleth , FRC He , and FRC N2 ). 3. The largest VC should be reported. 4. The mean values are reported for IC and ERV. 4.1. The technologist’s quality statements should clarify which method was used for reporting IC or ERV and the reason for selecting the method (e.g., “Patient had difficulty providing consistent ERV values, but IC was repeatable”). 5. The reported value for RV is the reported value for FRC minus the mean of technically acceptable ERV measurements linked to technically acceptable FRC determinations. 6. The reported value for TLC is the reported value for RV plus the largest of technically acceptable IVCs. Procedure Notes 1. Various miscellaneous factors may affect the measurement of lung volumes. 1.1. Perforated eardrums can cause a leak in the dilution/washout lung volume measurement system. The patient can wear earplugs to remedy this problem. 1.2. Diurnal variations in lung function may cause differences, so if serial measurements are to be per- formed, the time of day when those measurements are made should be held constant. 1.3. The best sequence of lung volumes and spirometry is controversial. 2. Adjustment for altitude is not necessary from sea level up to 1,800 meters (11–13).

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