Cardiorespiratory optimal point: A submaximal variable of the Cardiopulmonary Exercise Testing

Abstract

Background: At the maximal Cardiopulmonary Exercise Testing (CPET), several ventilatory variables are analyzed, including the ventilatory equivalent for oxygen (VE/VO2). The minimum VE/VO2 value reflects the best integration between the respiratory and cardiovascular systems and may be called "Cardiorespiratory Optimal Point (COP)". Objective: To determine the behavior of the COP according to gender and age in healthy adults and verify its association with other CPET variables. Methods: Of 2,237 individuals, 624 were selected (62% men and 48 ± 12 years), non-athletes, healthy, who were submitted to maximal CPET. COP or minimum VE/VO2 was obtained from the analysis of ventilation and oxygen consumption in every minute of CPET. We investigated the association between age and COP for both genders, as well as associations with: VO2 max, VO2 at anaerobic threshold (VO2 AT), oxygen uptake efficiency slope (OUES) and with maximum VE. We also compared the intensity of exertion (MET) at the COP, AT and VO2 max. Results: COP increases with age, being 23.2 ± 4.48 and 25.0 ± 5.14, respectively, in men and women = (p < 0.001). There are moderate and inverse associations with VO2 max (r = -0.47; p < 0.001), with VO2 AT (r = -0.42; p < 0.001) and with OUES (r = -0.34; p < 0.001). COP occurred, on average, at 44% do VO2 max and before AT (67% of VO2 max) (p < 0.001). Conclusion: COP, a submaximal variable, increases with age and is slightly higher in women. Being modestly associated with other ventilation measures, there seems to be an independent contribution to the interpretation of the cardiorespiratory response to CPET.