Effect of different mask design for measuring respiratory input impedance in pre-school children by forced oscillation technique (FOT)

To improve children’s comfort during FOT measurement, use of full face masks has been suggested as an alternative to mouthpieces. However, mask’s additional internal dead space and the presence of both nose and mouth breathing paths may influence the breathing pattern (BP) and FOT measurements. Different mask designs allowing or excluding nasal breathing are commercially available. The aim of this study was to evaluate the effect of mask design on measured FOT and BP parameters. Twenty-four children (14/10 males/females; 3.9±1.0 years) were recruited between those attending the pulmonary function test lab. Within-breath FOT at 8 Hz and BP parameters were measured during 10-15 quiet breaths using a commercial device (RESMON PRO FULL, RESTECH Italy) using in random order: 1) a mouthpiece with a nose clip; 2) a full face mask A allowing nasal and mouth breathing and 3) a full face mask B allowing only mouth breathing. Differences in variables were tested by ANOVA for repeated measurements. Compared to mouthpiece, full face mask A generated an underestimation of both resistance and reactance but not in BP parameters. Use of mask B provided similar results to mouthpiece and no differences were observed in any of the FOT and BP parameters. Mask design had an impact on FOT measurements. Only masks impeding nasal breathing provided comparable results to conventional mouthpieces.