Pulmonary (V) over dot O2 kinetics at the onset of exercise is faster when actual changes in alveolar O2 stores are considered

Breath-by-breath (BbB) oxygen uptake rate ((V) over dot O-2) Was measured at the mouth (MO) and at the alveolar level, at the onset of square wave cycling exercise of moderate intensity in six healthy male subjects. Alveolar BbB (V) over dot O-2 values were calculated correcting MO (V) over dot O-2 values by (i) estimating (GR): and (ii) measuring (opto-electronic plethysmography, OEP) BbB lung O-2 store changes. (V) over dot O-2 kinetics was then described by a bi-exponential model. GR yielded larger values of the time constants (tau(2)) of the primary phase of (V) over dot O-2 kinetics. The mean response times (MRTs) calculated by analysing GR BbB (V) over dot O-2 values were larger than (i) those obtained by using MO and OEP at 90W; and (ii) that by using MO at 120W. OEP corrected (V) over dot O-2 yielded the highest normalised amplitude of the cardiodynamic phase of the (V) over dot O-2 on-response. Correction of BbB (V) over dot O-2 for actual BbB changes of lung O-2 stores by OEP thus seems more appropriate for the study of the early cardiodynamic phase of (V) over dot O-2 kinetics than GR. (C) 2009 Elsevier B.V. All rights reserved.