JaNice Tay

This study aimed to assess the accuracy of the Cosmed K4b2 (Cosmed, Italy) portable metabolic system that measures FEO2, FECO2 and V̇E on a breath by breath basis. For gas concentration comparisons, expired air from 20 subjects performing treadmill running was collected in a 600 litre chain compensated Collins Tissot tank and analysed for FEO2 and FECO2 using a laboratory metabolic cart and the Cosmed K4 b2 metabolic system. For ventilation comparisons, serial steady state V̇E (STPD) values were measured on 10 subjects using the Cosmed K4b2 ventilation turbine and a Morgan ventilation monitor during a continuous treadmill running protocol at ascending speeds of 8, 11 and 14 km·h−1. The Cosmed K4b2 FEO2 and FECO2 measures were significantly lower (P<0.001) than the metabolic cart values. Pearson correlation coefficients (r) and the standard error of measurement (SEM) demonstrated a high association between the Cosmed and the metabolic cart measures (FEO2r= 0.971, SEM 0.071; FECO2r= 0.925, SEM 0.087). Cosmed V̇E (l·min−1 measures were significantly greater than Morgan values at running speeds of 8 km·h−1 (P<0.001) and 11 km·h−1 (P<0.001) but not significantly different at 14 km·h−1 (P>0.05). When V̇E measures at the three running speeds were combined, the mean difference between instrument measures ranged between 3.5 – 4.0 1·min−1 but the values were highly correlated (r= 0.982, P<0.01; SEM 3.03). Linear regression analysis revealed the following regression equations to predict metabolic cart values from Cosmed measures: FEO2= 0.852+0.963 Cosmed (R2= 0.940, P<0.001), FECO2= 0.627+0.878 Cosmed (R2= 0.856, P<0.001), V̇E= −2.50+0.984 Cosmed (R2= 0.965, P<0.001). The results indicated that the Cosmed K4b2 unit assessed here produced measures of FEO2, FECO2 and V̇E that had strong correlation to values obtained from a metabolic cart. However, linear regression analysis may further improve the accuracy of Cosmed K4b2 measures when compared to metabolic cart values.