Age and sex differences in blood pressure responses during hyperpnoea

Abstract

New Findings What is the central question of this study?Increased respiratory muscle activation is associated with neural and cardiovascular consequences via the respiratory muscle‐induced metaboreflex. Does ageing and/or sex influence the arterial blood pressure response during voluntary normocapnic incremental hyperpnoea? What is the main finding and its importance?The increase in blood pressure during hyperpnoea was smaller in younger females than in older females, whereas no difference was found between older males and older females. The blunted respiratory muscle‐induced metaboreflex in younger females is normalized with advancing age, whereas ageing has no such effect in males. Abstract We hypothesized that older females (OF) have a greater arterial blood pressure response to increased respiratory muscle work compared with younger females (YF) and that no such difference exists between older males (OM) and younger males (YM). To test these hypotheses, cardiovascular responses during voluntary normocapnic incremental hyperpnoea were evaluated and compared between older and younger subjects. An incremental respiratory endurance test (IRET) was performed as follows: target minute ventilation was initially set at 30% of the maximal voluntary ventilation (MVV12) and was increased by 10% of MVV12 every 3 min. The test was terminated when the subject could not maintain the target percentage of MVV12. Heart rate and mean arterial blood pressure (MAP) were recorded continuously. The increase in MAP from baseline (ΔMAP) during the IRET in OM (+24.0 ± 14.7 mmHg, mean ± SD) did not differ (P = 0.144) from that in YM (+24.3 ± 13.4 mmHg), but it was greater (P = 0.004) in OF (+31.2 ± 11.6 mmHg) than in YF (+10.3 ± 5.5 mmHg). No significant difference in ΔMAP during the IRET was observed between OM and OF (P = 0.975). These results suggest that the respiratory muscle‐induced metaboreflex is blunted in YF, but it could be normalized with advancing age. In males, ageing has little effect on the respiratory muscle‐induced metaboreflex. These results show no sex difference in the respiratory muscle‐induced metaboreflex in older adults.

Sex, gender and the pulmonary physiology of exercise

“…During hyperpnoea or inspiratory muscle loading, the mean arterial pressure response is similar in older males and females, suggesting that the sex difference in the respiratory muscle metaboreflex observed in younger adults is likely due to hormonal differences that are absent in post-menopausal females relative to age-matched males [37,100]. Whether or not this observation translates to whole-body exercise, or influences blood flow distribution during exercise, remains unclear; however, it suggests that for a given level of respiratory muscle work, the distribution of blood flow to respiratory and locomotor muscles during exercise is likely similar in older males and females.…”

“…When performing fatiguing inspiratory resistive or threshold breathing, the rise in mean arterial pressure is greater in males compared to females [33,35,100]. A blunted inspiratory metaboreflex in females has also been observed during voluntary hyperpnoea, which is more representative of the spontaneous breathing patterns observed during exercise [36,37]. The blunted metaboreflex in females is likely due to oestrogen upregulation of β 2 -adrenergic receptors which promotes vasodilation [101].…”

“…• Males above the age of ∼14 years have proportionally greater airway luminal area of the large conducting airway (i.e., trachea to the third generation) than females [15,[17][18][19][20] • Males have larger absolute lung volumes and more alveoli than females [9, 21] • Females have "prismatic" geometry of the ribcage and lung while males have "pyramidal" ribcage and lung geometry [22][23][24] Functional differences • Higher W b and V ̇O2 RM for a given absolute V ̇E during exercise in females compared to males [10,13,53-27] Due to a higher resistive component of W b [25,[28][29][30] • Females have greater activation of "extra-diaphragmatic" inspiratory muscles for a relative or absolute V ̇E during exercise Noted in the scalene and sternocleidomastoid muscles [31,32] • Highly trained males are less likely to develop expiratory flow limitation during exercise than highly trained females [13,25] • Females have a blunted respiratory muscle metaboreflex [33][34][35][36][37] • EIAH can occur in untrained females but does not appear to occur in untrained males [38][39][40] • Older females have a higher perception of dyspnoea at absolute and relative exercise intensities than older males [10,11,41] EIAH: exercise-induced arterial hypoxaemia; V ̇E: minute ventilation; V ̇O2 RM : oxygen uptake of the respiratory muscles; W b : work of breathing.…”

Blood pressure and coeliac artery blood flow responses during increased inspiratory muscle work in healthy males

“…Sex‐ and age‐related differences in the respiratory muscle‐induced metaboreflex were reported recently. Younger females had a blunted inspiratory muscle metaboreflex‐induced increase in sympathetic vasomotor outflow and ABP compared with age‐matched males (Katayama et al., 2018; Shimizu et al., 2021; Smith et al., 2016). Furthermore, the degree of increase in ABP attributable to increased respiratory muscle work was greater in older females than in younger females.…”

“…Furthermore, the degree of increase in ABP attributable to increased respiratory muscle work was greater in older females than in younger females. Additionally, the blunted metaboreflex seen in females associated with the respiratory muscle‐induced metaboreflex might normalize with advancing age (Shimizu et al., 2021; Smith et al., 2017). Therefore, the blood flow responses of the visceral organs might differ between young and older females when the respiratory metaboreflex is activated.…”