Impact of ageing and pregnancy on the minute ventilation/carbon dioxide production response to exercise

Abstract

Ventilatory efficiency can be evaluated using the relationship between minute ventilation (V′E) and the rate of CO2 production (V′CO2). In accordance with the modified alveolar ventilation equation, this relationship is determined by changes in dead space volume (VD) and/or the arterial CO2 tension (PaCO2) equilibrium point. In this review, we summarise the physiological factors that may account for normative ageing and pregnancy induced increases in V′E/V′CO2 during exercise. Evidence suggests that age-related increases in VD and pregnancy-related decreases in the PaCO2 equilibrium point are mechanistically linked to the increased V′E/V′CO2 during exercise. Importantly, the resultant increase in V′E/V′CO2 (ratio or slope), with normal ageing or pregnancy, remains below the critical threshold for prognostic indication in cardiopulmonary disease, is not associated with increased risk of adverse health outcomes, and does not affect the respiratory system's ability to fulfil its primary role of eliminating CO2 and maintaining arterial oxygen saturation during exercise.