Author(s): FRIOCOURT, M., SHEEL, A.W., ALIVERTI, A., BERTIN, D., MAIGNANT, G., BOUGAULT, V., Institution: UNIVERSITÉ CÔTE D'AZUR, Country: FRANCE, Abstract-ID: 1669

INTRODUCTION:
In sports and health sciences, the assessment of minute ventilation (V ̇E) is needed to determine ventilatory thresholds, to identify some abnormal breathing patterns, but also to quantify the inhaled dose of a pollutant during exercise. However, V ̇E measurement is currently not routinely available in the field. The smart Hexoskin T-shirt (Carré Technologies, Canada) is a promising tool in this regard, but validation studies are still conflicting, especially for ventilations above the first ventilatory threshold (VT1). Our aim is to investigate the validity of the V ̇E measurements provided by the Hexoskin T-shirt at different intensities in healthy active participants.
METHODS:
Healthy subjects (6 W, 6 M, age 24±7 yrs, height 172±10 cm, body mass 68±12 kg, V ̇O2max 51±9 ml.min-1.kg-1, mean ± SD) underwent a cardiopulmonary exercise test (CPET) with 2-min increments on a cycle ergometer (Saris H3, Saris, USA). After a 20-min of rest, a time to exhaustion (TTE) test was performed at 95% of maximal aerobic power or greater to add high intensity V ̇E data set. V ̇E was measured continuously using a metabolic system (Metamax 3B, Cortex, France) and Hexoskin. The tidal volume of Hexoskin was adjusted a posteriori for each subject by multiplying the values by a conversion factor, as specified by the manufacturer. This factor was obtained thanks to a spirometric forced expiratory manoeuvre before exercising, allowing to obtain the volume per signal amplitude. The V ̇E obtained by the two techniques were then synchronised in time and compared breath by breath. The VT1 was determined by the respiratory equivalent method.
RESULTS:
8 subjects completed the TTE test. When considering V ̇E during both CPET and TTE, the Pearson correlation coefficient (r) between both methods varied from 0.72-0.98. Individual mean differences vary between 3 l.min-1 and 54 l.min-1, with a total mean difference of 34 l.min-1. The coefficients of variation (CV) varied from -160 % to 310%. In CPET alone (n=12), r varied from 0.92-0.99 and mean differences between -3 l.min-1 and 71 l.min-1. In TTE alone (n=8), r varied from 0.54-0.98 and mean difference vary between 2 l.min-1and 88 l.min-1. When we compared 𝑉̇E values below the VT1 only, r varied between 0.77 and 0.98 and mean differences between -4 l.min-1and 34 l.min-1. Above VT1, r varied from 0.59-0.97 and mean differences from -3 l.min-1 to 105 l.min-1. Except for one subject, Hexoskin overestimates V ̇E values.
CONCLUSION:
We found poor agreement between V ̇E as measured with Hexoskin and the Metamax. Despite good correlation coefficients, the mean differences and CV are high, with very dispersed values around the mean difference, whatever the intensity. It seems the validity is better in some subjects compared with the others, and the explicative variable remain to be investigated.