Implications of breath-by-breath oxygen uptake determination on kinetics assessment during exercise.

We tested that the breath-by-breath V(O2) determination by an algorithm termed BR did not bias the kinetics parameters. It was compared to two other algorithms using a correction for changes in lung gas stores between two successive breaths (AU, W) and one without correction (NC). Ten healthy male subjects cycled 10 min at 15 and 30 W below and above ventilatory threshold (VT) after 3 min at 0 W. The breath-by-breath V(O2) variability was lower with BR than the other methods during the last 3 min at each power. V(O2) kinetics was described by a mono-exponential model at power below VT and a bi-exponential model above VT. Differences in parameter were only observed for the primary component between estimates using AU and NC. The between-subject variability in the parameters of the slow component at 15 W above VT was lower with AU and BR than W and NC. It was concluded that the BR algorithm could be used to analyse the V(O2) kinetics during exercise.