What is the clinical evidence from this study?

Study design: Cross-Sectional. Population: Obesity (n=1594). Intervention: Obesity (BMI ≥ 30 kg/m2) vs. Non-obese (normal weight and overweight). Primary outcome: Maximum pulmonary oxygen uptake (VO2max) relative to body mass (mL/min/kg) (p=≤0.05).

August 9, 2021Open Access

Dynamic physiological responses in obese and non-obese adults submitted to cardiopulmonary exercise test

Key Result

Obesity significantly worsened most maximal and submaximal cardiopulmonary exercise test responses, including maximum oxygen uptake, but prognostic ventilatory efficiency variables remained unchanged.

Study Design

Type

Cross-Sectional (n=1,594)

Multicenter

Structured PICO

Does obesity influence maximal and submaximal physiological responses during cardiopulmonary exercise testing in adults?

Population

1,594 adults without previously diagnosed heart, lung, or locomotor diseases capable of performing physical effort (755 obese with BMI ≥ 30 kg/m2, 839 non-obese including normal weight and overweight), mean age 39-42, 50.8-61.3% female, based in Brazil.

Intervention

Cardiopulmonary exercise testing (CPET) using an individualized ramp protocol on a motorized treadmill in obese adults (BMI ≥ 30 kg/m2)

Comparator

Cardiopulmonary exercise testing (CPET) using the same protocol in non-obese adults (normal weight and overweight, BMI < 30 kg/m2)

Outcome

Maximal and submaximal physiological responses during CPET (including oxygen uptake, carbon dioxide production, tidal volume, minute ventilation, heart rate, and submaximal dynamic variables like OUES and VE/VCO2)surrogate

While obesity worsens most maximal cardiopulmonary exercise testing parameters, submaximal ventilatory efficiency responses remain unchanged and can be reliably used for prognostic evaluation in obese patients.

Main Result

Absolute Event Rate: 22.8% vs 36.9%

p-value: p=≤0.05

Limitations

Use of the treadmill implies a lack of objective workload
Estimation of the peak of VO2 by using Hansen's equation can overestimate this value in obese subjects
Convenience sample

Abstract

PURPOSE: Obese individuals have reduced performance in cardiopulmonary exercise testing (CPET), mainly considering peak values of variables such as oxygen uptake (Formula: see text), carbon dioxide production (Formula: see text), tidal volume (Vt), minute ventilation (Formula: see text) and heart rate (HR). The CPET interpretation and prognostic value can be improved through submaximal ratios analysis of key variables like Formula: see text, Formula: see text, Formula: see text Formula: see text 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. METHODS: We 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. RESULT: Obesity 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, Formula: see text, Vt/Inspiratory Capacity, Vt/Forced Vital Capacity, Lowest Formula: see text, Formula: see text, and the y-intercepts of Formula: see text did not significantly differ regardless of obesity. CONCLUSION: Obesity 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.

Bookmark

View Full Paper