Comparison between the use of mouthpiece and facemask in assessing lung volumes and vital capacity in healthy subjects

Abstract

Respiratory function tests are used to determinate severity, functional consequences and progress of pulmonary and neuromotor dysfunctions. Methodological variations - by means of a mouthpiece or a facemask - and patient's cooperation may interfere in manoeuvre performance and affect measures. The aim of this study was to compare lung volume values (tidal volume [VT] and minute volume [Vm]), respiratory rate (RR), and vital capacity (VC) in healthy individuals when assessed by using a mouthpiece and a facemask. A total of 60 healthy subjects (14 men and 46 women), mean aged 22.86±7.14 years, were evaluated. Items used were a disposable, semi-rigid mouthpiece, with a nose clip, and a plastic facemask with pneumatic inflatable sealing. Measures obtained were statistically compared, with significance level set at 5%. Mean values obtained with the mouthpiece and the facemask were, respectively: RR, 15 rpm x 13 rpm (p<0.01); Vm, 14.87 l/min x 10.02 l/min (p<0.01); VT, 0.93 l x 0.8 l (p<0.01); and VC, 3.85 l x 3.52 l (p<0.01). Lung volumes and vital capacity values were thus shown to be significantly lower when assessed by means of a facemask than with a mouthpiece.