Oxygen uptake at maximal exercises in chronic airflow obstruction

Abstract

In order to gain a better understanding of maximal oxygen uptake in patients with chronic airflow obstruction, we compared the results of three different cyclo-ergospirometric protocols: progressive (30 W/3 min), constant and trapezoidal (10 min of 40 W + 30 W/3 min), in 26 male chronic bronchitis from 30 to 65 years of age. Eleven normal subjects of similar ages served as a control group. VE, VCO2, VO2, respiratory rate (RR) and VT were measured with an open circuit. The electrocardiogram was continuously monitored. Arterial lactate was measured at the end of the trapezoidal test in 20 patients. There were excellent correlations between the individual values of VO2 during the three maximal exercises and a low coefficient of variation of the differences between each paired measurement. There was great variability in VO2 between individuals, with values ranging from 14.7 to 46.2 ml X kg-1 X min-1 (control group : 29.5 to 54.4 ml X kg-1). A "levelling-off" in VO2 was observed in 22 patients who carried out, for 1 or 2 min, the exercise level immediately above the last step maintained for the full 3 min of the progressive test, i.e. the increase in VO2 was smaller than the average one for the preceding levels. In 14 patients, VO2 max was obtained as evidenced by the following criteria : heart rate = 220- age, respiratory quotient greater than 1.1 and arterial lactate greater than 7 mmol X l-1. In the remaining 12 patients, all these criteria were not achieved. After the progressive test, 61% of the patients said they could have performed better. However, in the subsequent maximal tests, these patients reached the same maximal VO2 values. All patients complained of pain in the legs at the end of the exercises, but only 8 of the 26 complained of breathlessness.(ABSTRACT TRUNCATED AT 250 WORDS)