A comparison of the ventilatory responses to exercise of elderly and younger humans.

Elderly adults are assumed to have an exaggerated ventilatory response to exercise. This study sought to examine this assumption by comparing the steady-state ventilatory and gas exchange responses of a group of elderly and younger humans. Steady-state ventilatory responses to moderate cycle ergometer exercise were measured in 14 elderly (71.0 +/- 1.3, mean +/- SEM years) and 14 younger (21.8 +/- 0.7 years) subjects. Compared with the younger group, the elderly had a significantly higher VE, VCO2, and VO2 at all work rates. In addition, delta VE/delta VCO2 was significantly higher for the elderly than for the younger subjects (31.07 +/- 1.34 vs 27.16 +/- 1.01, respectively; p less than .03), but the intercept with the ventilation axis was significantly lower (0.81 +/- 0.97 1.min-1 vs 4.15 +/- 0.77 1.min-1, respectively; p less than .015). Consequently, the VE-VCO2 relationships of the two groups crossed and the ventilatory equivalent for CO2 was similar for both groups. Thus, in these elderly subjects, the steeper delta VE/delta VCO2 was misleading because it was not associated with a greater ventilatory equivalent for CO2. In summary, although the ventilatory response of these elderly subjects to a given work rate was greater than that of the younger subjects, this was secondary to a greater metabolic requirement and cannot therefore be considered exaggerated. Furthermore, the data suggest that delta VE/delta VCO2 may be an inappropriate index of the ventilatory response to exercise in the elderly.