VO2 max during progressive and constant bicycle exercise in patients with chronic obstructive lung disease

Oxygen consumption (VO2) was studied during two maximal exercise tests (MET) performed on a cycle ergometer: one progressive (P-MET), the other constant (C-MET) in 6 normal men and in 21 male outpatients with chronic obstructive lung disease (COLD) from 34 to 64 years old. All of them were working. Clinical, spirographic (VC, FEV1) and cardiorespiratory parameters (VE, VO2, VCO2, f and RR) were measured. Arterial lactate was measured in the P-MET. In all patients the FEV1/VC ratio was lower than 60%. No adverse clinical effects were observed in both MET. In 19% of patients (n = 4) the VO2 was lower in the P-MET by about 20% than that observed in the C-MET. The execution of a second P-MET in these 4 patients showed values superimposed on those obtained with C-MET. Although the range of interindividual variability was considerable (VO2 0.95-2.5 l X min-1, and VE from 24 to 104 l X min-1), the comparison between the two MET showed a high correlation for VO2 (r = 0.989), VE (r = 0.969) and HR (r = 0.983) on the two occasions. A 'leveling off' of VO2 was observed in 15 patients in the P-MET. In 81% of patients VO2 max was obtained by the criteria of maximal HR (220 - age), respiratory quotient greater than 1.0, and arterial lactate greater than 8 mEq X l-1. In patients in which these criteria were not met only the reproducibility of the VO2 obtained in both the P-MET and the C-MET indicated that the maximal VO2 for these 4 patients had been reached.