Comparison of gas exchange data using the Aquatrainer^® system and the facemask with Cosmed K4b2 during exercise in healthy subjects

The aim of this study was to determine the level of agreement between the new Aquatrainer^® system and the facemask in the assessment of submaximal and maximal cardiopulmonary responses during exercise performed on ergocycle. Twenty-six physically active healthy subjects (mean age: 41 ± 14 years) performed a submaximal constant work test followed by maximal incremental exercise test on ergocycle, one with cardiopulmonary responses measured using the Cosmed K4b2 facemask, the other using the Cosmed K4b2 Aquatrainer^®. Using the Aquatrainer^®, the gas exchange variables at 100 W were significantly lower for VO₂ (1,483 ± 203 vs. 1,876 ± 204 ml min⁻¹, P < 0.0001), VCO₂ (1,442 ± 263 vs. 1,749 ± 231 ml min^-1, P < 0.0001), VE (38 ± 5 vs. 44 ± 6 l min⁻¹, P < 0.0001), and VT (1.92 ± 0.47 vs. 2.18 ± 0.41 l, P < 0.0001) relative to facemask. The bias ±95% limits of agreement (LOA) for VO₂ was 393 ± 507 ml min⁻¹ for the submaximal constant work test at 100 W and 495 ± 727 ml min⁻¹ for VO_2max. At maximal intensity, cardiopulmonary responses measured with the Aquatrainer^® system were significantly lower for: VO₂ (2,799 ± 751 vs. 3,294 ± 821 ml min⁻¹, P < 0.0001), VCO₂ (3,426 ± 836 vs. 3,641 ± 946 ml min⁻¹, P = 0.012), VE (98 ± 21 vs. 108 ± 26 l min⁻¹, P = 0.0009) relative to facemask. A non-constant measurement error [interaction effect: (facemask or aquatrainer) × power] was noted from 60 to 270 W for VO₂ (ml min⁻¹), VCO₂ (ml min⁻¹), ventilation (l min⁻¹) (P < 0.0001) and VT (l, P = 0.0001). Additional studies are required to detect the main sources of error that could be physical and/or physiological in nature. Due to the significant measurement error, the new Aquatrainer^® system should be used with extreme caution in filed testing conditions of swimmers.