Hypoxic (HVR) and hypercapnic (HCVR) ventilatory responses are influenced by both metabolic activity and hormonal factors. By studying 67 subjects of both sexes, including those at the extremes of stature, we examined the influence of gender, CO2 production (V̇co2), O2 consumption (V̇o2), body surface area (BSA), and vital capacity (VC) on resting ventilation (V̇), HVR, and HCVR. We measured resting V̇E, V̇o2, and V̇co2 and then performed isocapnic progressive hypoxic and hypercapnic ventilatory responses. The effect of stature was reflected in higher V̇E and metabolic rate (both P < 0.001) in tall men compared with short men that was ablated by correction for BSA. Perhaps because their heights vary less than those of the men, tall women were not statistically distinguishable from short women in any of these measured parameters. Tall men tended to have greater hypoxic chemosensitivity than short men but this was not significantly different (P = 0.07). Gender affected the control of ventilation in a number of ways. Men had higher V̇E (P < 0.05) and metabolic rate (P < 0.001) than women. Even after correction than BSA men still had higher metabolic rates. Women had higher V̇E/Vγo2 than men (P < 0.05) and lower resting end-tidal Pco2 (PET(co2)) values (P < 0.05). Both A, the shape parameter of the hyperbolic HVR curve, and HVR determined from mouth occlusion pressure (A(P)) were greater in women than in men, although only A(P) reached statistical significance. However, corrections of A for BSA (P < 0.05). Vγo2 (P < 0.01), and VC (P < 0.001) amplified these differences. The HCVR quantitated by the slope (S) as well as with occlusion pressures (S(P)) was greater in men than women but there was no difference when corrected for V̇co2 and V̇o2. We conclude that HVR, quantitated by the shape parameter A, should be corrected for metabolic rate so that the influence of stature is diminished and the male-female disparity becomes even greater. Furthermore, expression of chemosensitivity using mouth occlusion pressure may be a useful determinant of ventilatory drives.
All Science Journal Classification (ASJC) codes
- Physiology (medical)