Accuracy and reliabillity of a Cosmed K4b2 portable gas analysis system

The purpose of this study was to assess the validity and reliability of a Cosmed K4b(2) portable telemetric gas analysis system. Twelve physically fit males performed a treadmill running session consisting of an easy 10 min run, a hard 3 min run and a 1 min sprint (with rest periods of 10 min separating each run), on four separate occasions. Sessions were identical with the exception of the apparatus used to measure (V) over dot O-2. During two (test-retest) sessions a Cosmed K4b(2) portable gas analysis system was used; in another, a laboratory metabolic cart and, in one session, both systems were used to measure (V) over dot O-2 simultaneously. Comparison of Cosmed K4b(2) and metabolic cart measurements in isolation revealed significantly (p<0.05) increased values of (V) over dot O-2, (V) over dot CO2, F-E CO2 (except F-E CO2 at 10 min) and lower values of F-E O-2 for each run duration by the Cosmed system. Linear regression equations to predict metabolic cart results from Cosmed values were, respectively; cart (V) over dot O-2 = 0.926 (Cosmed (V) over dot O-2 - 0.227 [r(2) = 0.84) and cart (V) overdot CO2 = 1.057 (Cosmed (V) over dot CO2 - 0.606 [r(2) = 0.92). Bland-Altman plots and comparison of the test-retest Cosmed measurements revealed that the K4b(2) system showed good repeatability of measurement for measures of (V) over dot (E), (V) over dot O-2 and (V) over dot CO2, particularly for 10 min and 3 min tests (ICC = 0.7 - 0.9, p<0.05). In conclusion, the Cosmed K4b(2) portable gas analysis system recorded consistently higher (V) over dot O-2 and (V) over dot CO2 measurements in comparison to a metabolic cart. However, satisfactory test-retest reliability of the system was demonstrated.