ATS Pulmonary Function Laboratory Manual

chapter  11

Maximal Expiratory Pressure

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Step Action 7. A goal for repeatability should be that the two highest values agree within 10%. If the final effort is the high- est value, obtain an additional effort (6–8). 8. Allow the patient to rest for 30 to 60 seconds between efforts (3, 6, 8).

Review of Test Results 1. Final review of data on the report should be checked for accuracy and completeness by the individual per- forming the testing, and/or by the laboratory manager or supervisor.

Reporting of Test Results 1.

Pimax should be a negative value, reported in cm H 2 Pemax should be a positive value, reported in cm H 2

O. Report the most negative value. O. Report the most positive value.

2.

3. Report the number of efforts, degree of repeatability, percent of predicted, and lower limit of normal. 4. To adjust for differences in body size and varied levels of lung capacity, caused by disease states, pressures can be presented as percent of predicted TLC at which they were measured. This is not possible with handheld devices. 5. To facilitate the above corrections, it is preferable to perform lung volume testing at the same time as the maxi- mal respiratory pressures, using a body plethysmograph to obtain functional residual capacity (FRC pleth ). This allows correlation of respiratory muscles forces with the degree of hyperinflation at which they were generated, which can be especially important with patients with obstructive lung disease (1). However, the body plethysmograph makes coaching more difficult and the flanged mouthpiece may not be optimal for measuring at the same visit with the respiratory pressures measured outside the body plethysmograph. 6. Maximum respiratory pressures can usually be incorporated into the pulmonary function test report. If using a separate report, include demographic information. Procedure Notes 1. Handheld devices have been developed for quick and easy use at many clinical settings. 2. If handheld devices without recorders are used, values cannot be corrected for lung volumes. 3. It may be difficult to distinguish between poor patient effort and neuromuscular disease. More invasive tests such as twitch Pdi with phrenic nerve stimulation, or esophageal and gastric balloon placement may be required in these patients (9–11). 4. If testing is not performed with the patient in an upright sitting position, make a note on the report. 5. If the values observed are less than predicted, reassess the patient for cooperation and technique. If there is a physical reason for abnormal results, such as back injury or lip-seal leak, note those factors . (4). 6. Note if the patient appears not to understand the directions or does not appear to give a maximal effort. 7. If results are questioned, check the system calibration, and/or the technicians can test themselves. This serves the purpose of demonstrating the procedure again for the patient and comparing a known patient’s results to validate the instrument.

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