Ventilation response to CO2 and exercise-induced hypoxaemia in master athletes

Exercise-induced hypoxaemia (EIH) in master athletes may be related to a diminished exercise hyperpnoea. The aim of this study was to determine whether EIH is associated with a change in the sensitivity of the ventilation response to activation of the central chemoreceptors. The ventilation response to CO2 was measured in nine elderly untrained men (UT) [mean age 66.3 (SEM 3.1) years] and nine master athletes (MA) [mean age 62.7 (SEM 0.8) years] at rest, during moderate exercise (40% maximal oxygen uptake, (V) over dotO(2max)), and during strenuous exercise (70% (V) over dotO(2max)) using the rebreathing method. Our results showed that the ventilation response to CO2 did not differ with endurance training and/or exercise, that the threshold of the CO2 response (Th) increased with exercise (P < 0.001), that the increase in Th in MA was higher than in UT between rest and moderate exercise [Delta Th0-40: 8.55 (SEM 1.8) vs 3.06 (SEM 1.72) mmHg, P < 0.05], and that Delta Th0-40 and Th during moderate exercise were negatively correlated with arterial O-2 saturation during maximal exercise (r = 0.50, P < 0.05). We concluded therefore that exercise-induced hypoxaemia in master athletes may not be due to a lower ventilation response to CO2, but may be partly related to a greater increase in Th during moderate exercise.