Cardiopulmonary exercise testing (CPET), also known as ergospirometry, can help to early signal respiratory disease in obese people. This was the main finding of a research developed to assess the influence of obesity on physiological responses obtained during the test.
Ergospirometry is an exam that associates the conventional exercise test with the analysis of the exhaled air by the individual, which allows obtaining measures such as the capacity of oxygen consumption by the lungs (VO2), the production of carbon dioxide (VCO2), the respiratory rate and lung ventilation. Identifies which range of aerobic conditioning the person is in. Therefore, it is indicated for initial evaluation in physical exercise programs, both in clinical practice and for amateur or high performance athletes.
The study showed that the results of the main ventilatory responses remained unchanged in volunteers with obesity compared to non-obese. One example is the relationship between volume expired per minute (VE) and VCO2, which averaged 25.4 and 25.6, respectively. This variable represents the amount of ventilation used to eliminate a given amount of carbon dioxide throughout the test and indicates the ventilatory efficiency.
That is, obesity does not influence this variable. Therefore, abnormal values ​​in this case can be useful in the early detection of respiratory disorders and give signs of problems when the person still has no symptoms, regardless of obesity.
However, as expected for almost all of the dozens of maximum and submaximal variables evaluated in the test, obesity had a negative influence on the performance of individuals. The most influenced were cardiovascular, metabolic and gas exchange.
The work, published in the journal Plos One, was carried out by researchers from the Department of Human Movement Sciences at the Federal University of São Paulo (Unifesp), on the Santos campus, with support from Fapesp. It also had the participation of three medical researchers from the Angiocorpore Institute of Cardiovascular Medicine, in Santos.
“The cardiopulmonary exercise test is still underused in patients with obesity. It can point out many variables and has a great diagnostic and pre-diagnostic potential that is not adequately explored. It is very likely that it is an incipient respiratory disease and not a consequence of obesity”, says Professor Victor Zuniga Dourado, coordinator of the Laboratory of Epidemiology and Human Movement (Epimov) at Unifesp and supervisor of the research.
According to him, the test does not specifically indicate the type of disease, but it can be used as a potential test to identify early causes of exercise intolerance and make it possible to refer the patient to a specialist doctor for a more accurate diagnosis.
“There are respiratory alterations that take a long time to be detected at rest. Exercise is a great challenge to identify them at the beginning. Our results have great practical applicability in the identification of exercise limitation, especially ventilatory, regardless of overweight and obesity”, he explains. the teacher.
For Bárbara de Barros Gonze, first author of the work (result of her master’s degree), one of the innovations was the evaluation of the maximum and submaximal physiological responses during the test, which vary according to the physical preparation of each person.
“The submaximal data do not require maximum effort to be obtained, so they can be useful in the early diagnosis of limitations in exercise tolerance, especially for people with less physical fitness or some chronic disease. At work, we showed that measurement and interpretation of submaximal responses in the test can be encouraged in routine clinical practice”, says Gonze.
Zuniga Gold also highlights the number of tests included in the analysis. “To our knowledge, this is the first study to investigate the influence of obesity, according to severity and adjusted for major cardiovascular risk factors, on the dynamic physiological responses obtained in CPET in a robust sample,” the researchers write in the article.
how was it done
The group carried out a cross-sectional study, in which 1,594 CPETs of adults (755 obese participants) obtained between 2013 and 2018 were analyzed. association between low level of physical activity and low physical fitness with the development of diseases and chronic conditions, especially cardiovascular, respiratory and musculoskeletal ones.
Obesity is a chronic disease characterized by the excessive accumulation of fat in the body. For diagnosis in adults, the most used parameter is the body mass index (BMI), which is calculated by dividing the person’s weight (in kilograms) by the height (in meters) squared.
Overweight individuals have a BMI of 25 to 29.9 kg/m². An index equal to or above 30 kg/m² is considered obesity, according to the World Health Organization (WHO).
One of the main public health problems in the world, obesity has more than doubled in 17 years in Brazil, also affecting more and more children and young people. The percentage of adults with the disease increased from 12.2% to 26.8% between 2002 and 2019. Including those with excess weight, the rate grew from 43.3% to almost 62.1%, representing about 96 million of Brazilians, according to the National Health Survey 2019.
High BMI is a major risk factor for cardiovascular disease, musculoskeletal disorders, cancer and, more recently, it is also linked to the worsening of Covid-19.
In the research, the inclusion criterion for volunteers was the absence of previously diagnosed heart, lung or locomotor diseases. The variables obtained between the “non-obese” (normal weight and overweight) and “obese” groups were compared using multivariate analysis of covariance.
Performed on a motorized treadmill, the test followed an individualized ramp protocol. The same variables for each participant were considered to automatically increase speed and incline, which started at 3 km/h and 0%, respectively.
Based on age, sex, body mass, height and physical activity level, the software estimated VO2 (maximum oxygen consumption capacity by the lungs).
At rest, an adult individual has an estimated VO2 of about 3.5 ml/min-1 kg, also called metabolic equivalent (MET). A healthy man reaches a VO2 max in effort around 35 to 40 ml/min-1 kg and women between 27 and 30 ml/min-1 kg, while elite athletes reach 70 ml/min-1 kg.
In the survey, normal-weight patients had, on average, a VO2 max of 39.6 ml/min-1 kg, falling to 33.8 ml/min-1 kg in overweight individuals. For people with higher BMI, it reached 19.2 ml/min-1 kg.
Before exertion until exhaustion, the volunteer remains at rest for 3 minutes, allowing an initial assessment of baseline measurements. Then, maximal or symptom-limited CPET aims to exhaust the patient within 8 to 12 minutes of exercise, followed by 3 to 6 minutes of recovery.
During the examination, a continuous assessment of the cardiovascular, respiratory and locomotor systems is carried out, obtaining results when the body is subjected to physical effort. It also assists in the medical investigation of diseases not clearly diagnosed at rest.
The article Dynamic physiological responses in obese and non-obese adults submitted to cardiopulmonary exercise test can be read here.
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