The mouthpiece is the standard interface for spirometry tests. Although the use of a mouthpiece can be challenging for patients with orofacial weakness, maintaining a proper seal with a facemask can be an issue for healthy individuals during forceful efforts. We compared respiratory muscle activity and tests using a mouthpiece and facemask in healthy adults to investigate whether they can be used interchangeably.
In this observational study, subjects (n = 12) completed forced vital capacity, maximal respiratory pressure, and peak cough flow with a mouthpiece and facemask. Root mean square values of the genioglossus, diaphragm, scalene, and sternocleidomastoid were compared between conditions.
When switching from a mouthpiece to a facemask, significantly higher values were seen for peak cough flow (average bias = −54.36 L/min, P < .05) and the difference seen with maximal expiratory pressure (MEP) and maximal inspiratory pressure (MIP) were clinically significant (average bias: MEP = 27.33, MIP = −5.2). In addition, the submental activity was significantly greater when MIP was conducted with a mouthpiece. No significant differences were seen in respiratory muscle activity during resting breathing or spirometry.
There are clinically significant differences with cough and MEP tests, and neck muscles are activated differently based on interface. Considering the small sample size, our findings suggest a facemask may be used to complete some pulmonary function tests.