Effect of age-related ventilatory inefficiency on respiratory sensation during exercise.

To examine the effect of age-related respiratory function impairment on exertional dyspnea, we compared ventilatory and perceptual responses to incremental exercise under control (CTRL) and added dead space (DS) loading conditions in healthy fit older (55-79 years) and younger (20-39 years) men. Older individuals had higher ventilatory equivalents for CO2 throughout exercise (p<0.05) suggesting greater ventilatory inefficiency but operating lung volumes were similar compared to younger individuals. With added DS compared to CTRL, both groups similarly increased tidal volume (by 0.3-0.6 L) and ventilation (by 8-13 L/min) at submaximal work rates (each p<0.05). At peak exercise with DS, both groups failed to further increase ventilation and had small reductions in peak work rate (p<0.05). Increases in dyspnea intensity ratings with the addition of DS were similar at standardized submaximal work rates in older and younger groups. We conclude that, despite differences in ventilatory efficiency, the respiratory-mechanical and sensory responses to added chemostimulation during exercise were similar in fit older and younger individuals.