Abstract
PurposeObese individuals have reduced performance in cardiopulmonary exercise testing (CPET), mainly considering peak values of variables such as oxygen uptake (), carbon dioxide production (), tidal volume (Vt), minute ventilation () and heart rate (HR). The CPET interpretation and prognostic value can be improved through submaximal ratios analysis of key variables like , , and oxygen uptake efficiency slope (OUES). The obesity influence on these responses has not yet been investigated. Our purpose was to evaluate the influence of adulthood obesity on maximal and submaximal physiological responses during CPET, emphasizing the analysis of submaximal dynamic variables.MethodsWe analyzed 1,594 CPETs of adults (755 obese participants, Body Mass Index ≥ 30 kg/m2) and compared the obtained variables among non-obese (normal weight and overweight) and obese groups (obesity classes I, II and III) through multivariate covariance analyses.ResultObesity influenced the majority of evaluated maximal and submaximal responses with worsened CPET performance. Cardiovascular, metabolic and gas exchange variables were the most influenced by obesity. Other maximal and submaximal responses were altered only in morbidly obese. Only a few cardiovascular and ventilatory variables presented inconsistent results. Additionally, Vtmax, , Vt/Inspiratory Capacity, Vt/Forced Vital Capacity, Lowest , , and the y-intercepts of did not significantly differ regardless of obesity.ConclusionObesity expressively influences the majority of CPET variables. However, the prognostic values of the main ventilatory efficiency responses remain unchanged. These dynamic responses are not dependent on maximum effort and may be useful in detecting incipient ventilatory disorder. Our results present great practical applicability in identifying exercise limitation, regardless of overweight and obesity.
Highlights
Cardiopulmonary exercise test (CPET) presents indisputable clinical applicability for the diagnosis of exercise intolerance and its causes, as well to quantify cardiorespiratory fitness (CRF) [1, 2]
Our results present great practical applicability in identifying exercise limitation, regardless of overweight and obesity
Considering possible difficulties in reaching the maximum effort leading to interpretative limitation of the maximal incremental exercise variables (e.g., V_O2max, Maximum heart rate (HRmax), metabolic equivalent of task (MET), gas exchange rate (R) and the other variables registered at peak of effort), the CPET interpretation can be significantly improved by an evaluation of the tendency of submaximal relationships (e.g., anaerobic threshold (AT) values and lowest Minute ventilation (V_E)=V_CO2, while oxygen uptake efficiency slope (OUES) and the aforementioned ratios and intercepts) obtained before the peak of the exercise
Summary
Cardiopulmonary exercise test (CPET) presents indisputable clinical applicability for the diagnosis of exercise intolerance and its causes, as well to quantify cardiorespiratory fitness (CRF) [1, 2]. Obese individuals present decreased CRF, mainly caused by low pulmonary complacency and functional residual capacity [3] combined with a less pronounced chronotropic response during sustained effort [4]. Considering possible difficulties in reaching the maximum effort leading to interpretative limitation of the maximal incremental exercise variables (e.g., V_ O2max, HRmax, metabolic equivalent of task (MET), gas exchange rate (R) and the other variables registered at peak of effort), the CPET interpretation can be significantly improved by an evaluation of the tendency of submaximal relationships (e.g., anaerobic threshold (AT) values and lowest V_ E=V_ CO2, while OUES and the aforementioned ratios and intercepts) obtained before the peak of the exercise. The evaluation of these submaximal variables is especially interesting in obese population, which present difficulties to achieve maximum effort [10, 11]
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