The effects of age and sex on mechanical ventilatory constraint and dyspnea during exercise in healthy humans

Abstract

We examined the effects of age, sex, and their interaction on mechanical ventilatory constraint and dyspnea during exercise in 22 older (age = 68 ± 1 yr; n = 12 women) and 22 younger (age = 25 ± 1 y, n = 11 women) subjects. During submaximal exercise, older subjects had higher end-inspiratory (EILV) and end-expiratory (EELV) lung volumes than younger subjects (both P < 0.05). During maximal exercise, older subjects had similar EILV ( P > 0.05) but higher EELV than younger subjects ( P < 0.05). No sex differences in EILV or EELV were observed. We noted that women had a higher work of breathing (W) for a given minute ventilation (V̇e) ≥65 l/min than men ( P < 0.05) and older subjects had a higher W for a given V̇e ≥60 l/min ( P < 0.05). No sex or age differences in W were present at any submaximal relative V̇e. At absolute exercise intensities, older women experienced expiratory flow limitation (EFL) more frequently than older men ( P < 0.05), and older subjects were more likely to experience EFL than younger subjects ( P < 0.05). At relative exercise intensities, women and older individuals experienced EFL more frequently than men and younger individuals, respectively (both P < 0.05). There were significant effects of age, sex, and their interaction on dyspnea intensity during exercise at absolute, but not relative, intensities (all P < 0.05). Across subjects, dyspnea at 80 W was significantly correlated with indexes of mechanical ventilatory constraint (all P < 0.05). Collectively, our findings suggest age and sex have significant impacts on W, operating lung volumes, EFL, and dyspnea during exercise. Moreover, it appears that mechanical ventilatory constraint may partially explain sex differences in exertional dyspnea in older individuals. NEW & NOTEWORTHY We found that age and sex have a significant effect on mechanical ventilatory constraint and the perception of dyspnea during exercise. We also observed that the perception of exertional dyspnea is associated with indexes of mechanical ventilatory constraint. Collectively, our results suggest that the combined influences of age and biological sex on mechanical ventilatory constraint during exercise contributes, in part, to the increased perception of dyspnea during exercise in older women.

Manipulation of mechanical ventilatory constraint during moderate intensity exercise does not influence dyspnoea in healthy older men and women

“…) and absolute work rate (Molgat‐Seon et al . ) than older men. Although the precise causes of sex‐differences in the perception of dyspnoea during exercise are likely multifactorial, it is possible that inherent differences in the structure of the respiratory system play a contributory role.…”

“…The magnitude of inspiratory resistance was chosen in order to increase the resistive component of W b to the same degree as the magnitude of the sex‐difference in W b at a given absolute based on our previous work in healthy older men and women (Molgat‐Seon et al . ). In other words, we wanted to increase the W b in older men to a similar level as observed in women at the same absolute and we aimed to increase the W b in older women by an equivalent amount above their normally occurring W b at a given .…”

“…Consequently, older individuals have a greater magnitude of mechanical ventilatory constraint during exercise than younger individuals, as indicated by a greater work of breathing ( W b ), higher operating lung volumes, and an increased propensity towards expiratory flow limitation (EFL) (Molgat‐Seon et al . ). The magnitude of mechanical ventilatory constraint directly affects the degree of respiratory effort required to exercise at a given absolute intensity (O'Donnell et al .…”

“…First, older women have a higher W b for a given minute ventilation () and are more likely to exhibit EFL during exercise than older men (Molgat‐Seon et al . ). Second, indices of mechanical ventilatory constraint and respiratory effort during submaximal exercise have been shown to correlate with ratings of dyspnoea in older men and women (Molgat‐Seon et al .…”

“…Second, indices of mechanical ventilatory constraint and respiratory effort during submaximal exercise have been shown to correlate with ratings of dyspnoea in older men and women (Molgat‐Seon et al . ). Third, when the degree of mechanical ventilatory constraint is experimentally increased during exercise, using resistive loading or dead‐space loading, the perception of dyspnoea is increased concomitantly (el‐Manshawi et al .…”