Metabolic

Cardiopulmonary exercise tests can be used

Image: Professor Victor Zuniga Dourado with a volunteer
outlook more

Photo credit: Alan Carlos Brisola Barbosa

Cardiopulmonary exercise tests (CPET), also known as ergospirometry, can be used for the early detection of respiratory diseases in overweight and obese people. This is the main finding of a study by Brazilian researchers who wanted to investigate the influence of obesity on the physiological responses in CPET.

CPET combines a conventional ergometric test with expelled air analysis to obtain measurements of pulmonary oxygen uptake (VO2), carbon dioxide production (VCO2), respiratory rate, and pulmonary ventilation. It determines the level of aerobic conditioning and is indicated for initial assessment in physical training programs both in clinical practice and for amateur or high-performance athletes.

The study showed that the main respiratory responses in obese volunteers were unchanged. For example, the ratio of minute ventilation (VE, the volume of air exhaled in one minute) to VCO2 averaged 25.4 for the obese group and 25.6 for the non-obese control group. The ratio corresponds to the amount of ventilation used to eliminate a certain amount of carbon dioxide during the test and is an indicator of breathing efficiency.

Finding that obesity does not affect this variable means that abnormal values ​​can be useful in early detection of respiratory disease and can indicate potential problems before symptoms appear, regardless of obesity.

However, obesity, as expected, affected performance for almost all of the many maximum and submaximal variables analyzed in the study. The cardiovascular, metabolic, and gas exchange variables were most affected.

An article about the study is available released in PLOS ONE. Most of the authors are researchers at the Department of Human Movement Sciences at the Federal University of São Paulo (UNIFESP) in Santos. The study was supported by FAPESP. Three doctors from the Angiocorpor Institute of Cardiovascular Medicine in Santos also attended.

“CPET is inadequately used in obese patients. It can bring many potential problems to light and has significant diagnostic and predictive potential that is not adequately researched. Our study shows that a change in ventilation efficiency is very likely to be an incipient respiratory disease and not a consequence of obesity, ”said Victor Zuniga Dourado, Head of UNIFESP’s Epidemiology and Human Movement Laboratory (EPIMOV) and lead researcher on the study.

The test does not diagnose a specific disorder or disease, explained Dourado, but can be used to detect exercise intolerance at an early stage and identify its causes, so that the patient can be referred to a specialist for a more precise diagnosis.

###

About the São Paulo Research Foundation (FAPESP)

The São Paulo Research Foundation (FAPESP) is a public institution that aims to support scientific research in all fields of knowledge by awarding scholarships, grants and grants to researchers associated with universities and research institutions in the Brazilian state of São Paulo. FAPESP is aware that the very best research can only be done internationally by working with the best researchers. For this reason, it has established partnerships with funding agencies, universities, private companies and research organizations in other countries that are known for the quality of their research, and encourages scholars funded by their scholarships to further expand their international collaboration. You can learn more about FAPESP at http://www.fapesp.br/en and visit the FAPESP news agency at http://www.agencia.fapesp.br/en to keep up to date with the latest scientific breakthroughs, the FAPESP through its many programs, awards and research centers. You can also subscribe to the FAPESP news agency at http://agencia.fapesp.br/subscribe.

“There are changes in the airways that can take a long time to detect when at rest. Movement is an excellent challenge to spot them early on. Our results can be used very well in practice to identify movement restrictions regardless of overweight or obesity, ”he said.

The course was part of the master’s research by Barbara de Barros Gonzé, First author of the article. According to Gonze, one of his innovations was the assessment of maximal and submaximal physiological responses during CPET. These vary depending on the physical fitness of the individual. “Submaximal data does not require maximum effort and can therefore be useful for diagnosing the onset of exercise tolerance restrictions, especially in people who are not very fit or who have a chronic illness. In the study, we showed that the measurement and interpretation of submaximal responses to the test can be promoted in routine clinical practice, ”she said.

“To the best of our knowledge, this is the first study to examine the influence of obesity according to its severity and adjusted for the most important cardiovascular risk factors on the dynamic physiological responses obtained in CPET in a robust sample,” the authors write.

Methods

The group conducted a cross-sectional, retrospective analysis of 1,594 adult CPETs (755 obese) between 2013 and 2018. The test results were taken from the database of the endocrinological outpatient clinic of the Angiocorpor Institute and from UNIFESP’s Epidemiological Study of Human Movement (EPIMOV.)).

Obesity is a chronic disease that is characterized by an excessive amount of body fat. The most frequently used criterion for diagnosis in adults is the body mass index (BMI), which is the weight in kilograms divided by the square of the height in meters. A BMI of 25-29.9 kg / m² is classified as overweight by the World Health Organization (WHO), while 30 kg / m² or more is considered obese.

Obesity is one of the world’s leading health problems and more than doubled in 2012-19 in Brazil, where more and more children and young adults are obese. The proportion of the adult population considered obese increased from 12.2% to 26.8% during the reporting period. The proportion considered overweight or obese rose from 43.3% to 61.7% according to the 2019 National Health Survey (Pesquisa Nacional de Saúde).

A high BMI is an important risk factor for cardiovascular diseases, musculoskeletal diseases and cancer as well as severe COVID-19.

The criteria for inclusion in the study were the absence of previously diagnosed heart, lung or motion disorders and the ability to perform physical exertion. The researchers performed a series of multivariate analyzes of covariance to assess the effects of obesity on the CPET variables by comparing data for non-obese people (normal weight and overweight) with data for obese people.

The test was performed on a motorized treadmill according to an individualized ramp protocol. The same variables were taken into account for the automatic increase in speed and incline, starting at 3 km / h and 0%, respectively. The treadmill software estimated the maximum VO2 based on age, gender, body mass, height, and physical activity.

The resting VO2 level in adults averages 3.5 ml / kg / min, which is often referred to as the metabolic task equivalent (MET). The maximum VO2 averages 35-40 ml / kg / min for untrained healthy men and 27-30 ml / kg / min for women, while top athletes can reach 70 ml / kg / min.

In the study, the maximum VO2 averaged 39.6 ml / kg / min in subjects of normal weight and 33.8 and 19.2 ml / kg / min in overweight and obese subjects, respectively.

Before the test, the subjects rested for three minutes while the baseline measurements were taken. The test then continued to exhaustion within 8-12 minutes of exercise (or an interruption due to symptoms), followed by three minutes of recovery.

Cardiovascular, metabolic, and gas exchange variables were most affected by obesity. Other maximum and submaximal responses were changed only in morbidly obese individuals.

Research subject

persons

Article heading

Dynamic physiological responses in obese and non-obese adults subjected to cardiopulmonary stress test

Publication date of the article

08/09/2021

Related Articles