Validity of Oxycon Mobile in measuring inspiratory capacity in healthy subjects

Inspiratory capacity (IC) assessments have been performed mainly in laboratory settings, because of fixed measurement devices. Oxycon Mobile (OM) is the mobile and wireless version of Oxycon Pro (OP), a commonly used fixed measurement device. The purpose of this study was to examine IC agreement between OM and OP at rest and during steady-state exercise. Also, the within- and between-days variability of IC's were determined.

Thirty-five healthy subjects were recruited. Twenty-five subjects were included for determining validity of the OM and ten subjects for the variability study. For validation of OM, resting and exercise IC's (IC(rest) and IC(exercise) respectively) were measured consecutively by OM and OP, in random order. Exercise consisted of cycle ergometry at 50% of subject's predicted maximal exercise capacity.

The mean difference between OM and OP regarding IC(rest) was -0.05L, with limits of agreement of -0.47 to 0.37L (or -1.2% with limits of agreement of -11.6 to 9.3%) (P>0.05). The mean difference of IC(exercise) was -0.06L, and the limits of agreement were -0.48 to 0.35L (or -1.4% with limits of agreement of -11.8 to 9.0%) (P>0.05). No significant differences in IC's within- or between-days were found.

The limits of agreement of the IC measured by OM and OP were +/-10%, which is recommended for interdevice reproducibility. We conclude that OM and OP can be used interchangeably for measuring IC at rest and during steady-state exercise.