Comparação entre a resposta cardiopulmonar, metabólica e sintomas declaudicação de indivíduos com doença arterial periférica em teste de exercícioincremental na esteira versus cicloergômetro

Abstract

Peripheral arterial disease (PAD) is a vascular disease that impair peripheral blood flow. Methods for evaluation of exercise tolerance are important in the initial characterization and clinical follow-up of patients with PAD and usually are carried out on treadmill protocols. Few studies have made comparisons with other test modes so far, using methods that allow the direct evaluation of responses to exercise. The near-infrared spectroscopy (NIRS) is a method that monitors the supply of oxygen to the peripheral muscle tissue, a key pathophysiologicalmechanism of PAD, which can help better understand the peripheral limitations of these individuals. The aim of this study was to compare the cardiopulmonary and metabolic responses, claudication symptoms and behavior of deoxyhemoglobin and tissue saturation index at calf in incremental tests on treadmill and cycle ergometer. The volunteers were submitted to a spirometry and two incremental tests, one in a treadmill and one in a cycle ergometer, in random order. The incremental treadmill test was started with 3.2 km/h and 0% of slope for five minutes, followed by stages with fixed speed of 3.2 km/h and increased by 3.5% in the slope every three minutes. For the test in cycle ergometer the subject was instructed to maintain a cadence of 60 revolutions per minute, pedalling initially at 20 watts (W) for five minutes followed by a 20 W increment every three minutes. During each test, the subjects had their calf monitored by NIRS and blood samples were collected for lactate analysis and expired gases analysis were made. Subjects were instructed for signalling thestart of the claudication symptom. Normal distribution of the data was evaluated by Shapiro-Wilk test. Mixed ANOVA was used to compare variables using the type of test as plot and level of obstruction as a subplot. LSD was used for posthoc analysis. To evaluate the ability of peak oxygen consumption (peak VO2) and peak relative concentration of deoxyhemoglobin (peak HHb) in discriminating the level of obstruction (proximal versus distal), a discriminant analysis was performed. For the measures of association Pearson correlation coefficient was applied. For all analysis, an alpha of 5% was considered as significance level. The final sample consisted of 16 individuals with DAP, from which two individuals did not perform one of the tests and were excluded from the comparison analysis. The average age was 64.8 ± 8.5 years, with a body mass index (BMI) of 25.52 ± 3.34 kg/m² and average ankle-brachial index for both members of 0.63 ± 0.16. When comparing the test on a treadmill versus cycle ergometer, a lower respiratory exchange ratio at peak exercise (peak RER), less variation in serum lactate (Lactate), a higher test duration and a lower ratio between the time to onset of pain and the test duration to exercise was found for the treadmill test. Between subjects with proximal and distal obstruction there were difference inpeak VO2, peak minute ventilation (peak VE), Lactate, test duration and time to onset of pain. The discriminant analysis considering the peak VO2 and peak HHb was able to correctly classify 89.5% of subjects with proximal obstruction and 81.8% of subjects with distal obstruction, regardless of the type of test. The cycle ergometer and treadmill test was able therefore to produce similar maximal cardiopulmonary response, despite differences in metabolic response, parameters observed by NIRS and claudication symptoms. A greater contribution of the glycolytic pathway and lower distal peripheral demand for oxygen extraction was observed in cycle ergometer, with the variation of serum lactate concentration as a factor associated with the performance in this mode ofexercise. Individuals with proximal involvement performed worse in both tests and in the absence of imaging test for diagnosing level of involvement, the use of cardiopulmonary exercise testing and NIRS as a non-invasive tool for patient stratification can be performed with good accuracy.