VENTILATORY RESPONSES TO EXERCISE AND CARBON-DIOXIDE IN ELDERLY AND YOUNGER HUMANS

The present investigation examined the relationship between CO2 sensit ivity [at rest (S(R)) and during exercise (S(E))] and the ventilatory response to exercise in ten elderly (61-79 years) and ten younger (17- 26 years) subjects. The gradient of the relationship between minute ve ntilation and CO2 production (DELTAV(E)/DELTAVCO2) Of the elderly subj ects was greater than that of the younger subjects [mean (SEM); 32.8 ( 1.6) vs 27.3 (0.4); P<0.01]. At rest, SR was lower for the elderly tha n for the younger group [10.77 (1.72) vs 16.95 (2.13) 1.min-1.kPa-1; 1 .44 (0.23) vs 2.26 (0.28) 1.min-1-mmHg-1; P<0.05], but SE was not sign ificantly different between the two groups [17.85 (2.49) vs 19.17 (1.6 2) 1.min-1.kPa-1; 2.38 (0.33) vs 2.56 (0.21) 1.min-1.mmHg-1]. There we re significant correlations between both S(R) and S(E), and DELTAV(E)/ DELTAVCO2 (P<0.05; P<0.001) for the younger group, bot none for the el derly. The absence of a correlation for the elderly supports the sugge stion that DELTAV(E)/DELTAVCO2 is not an appropriate index of the vent ilatory response to exercise for elderly humans.