Mouthpieces and test quality

Mouthpieces serve at least two purposes. The first is to prevent cross-contamination among patients using PFT equipment. The ATS Statement on General Considerations for Lung Function Testing, (Eur Resp J, 2005; 26: 153-161) discusses this and it is clear that mouthpieces should be used whenever and wherever pulmonary function tests are performed.

The second purpose however, is to prevent patients from leaking air during testing. Leaks are a chronic problem for all pulmonary function tests and my experience has been that when they occur it is almost always the patient that is leaking and not the equipment.

Although all pulmonary function tests can be affected by patient leaks the helium dilution and nitrogen washout lung volume measurements are particularly prone to leaks due of the length of time it takes for them to be performed. These tests are also sensitive to small leaks because the accuracy of the measurements is based on relatively small changes in gas concentrations.

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