Differences in respiratory oscillometry measurements using mouthpiece, mouth- and nasal mask in healthy adults

Airway resistance measurements using oscillometry provide a potential alternative to spirometry in assessing airway obstruction and dynamics due to measurements taken during tidal breathing. Oscillometry typically requires participants to form a tight seal around a mouthpiece which can prove challenging in some people. To address this challenge, we conducted a prospective study to evaluate the effect of different interfaces: mouthpiece, mouth mask and nasal mask; on respiratory impendence results from oscillometry in a cohort of healthy adults. Ten healthy adults (seven females; mean age: 38.9 years (SD ±15.5) underwent oscillometry using each of the three interfaces. We measured resistance at 5Hz (Rrs5); frequency dependence of resistance at 5 -20Hz (Rrs5-20); and reactance area (Ax). Rrs5 was not different when using the mouthpiece compared to the mouth mask (mean 2.98 cmH2O.l-1.s (SD ±0.68) vs mean 3.2 cmH2O.l-1.s (SD ±0.81; p=0.92; 95% CI -0.82 to +0.38) respectively. Nasal mask Rrs5 measurements were significant higher than mouthpiece measurements (mean 7.31 cmH2O.l-1.s; SD ±2.62; p < 0.01; 95%CI -6.91 to -1.75). With Ax5 we found a mean of 4.01 cm H2O/l (SD ±2.04) with the mouth mask compared to a mean of 4.02 cm H2O/l (SD ±1.87;p=1.0 95% CI -1.86 to +1.87) for the mouthpiece, however, we found a significant difference between the mouthpiece and nasal mask for Ax (mean= 10.71; SD ±7.0 H2O/l; p=0.04, 95% CI -12.96 to -0.43). Our findings show that oscillometry using a mouth mask may be just as effective as using a mouthpiece in assessing airway dynamics and resistance.