IJCS | Volume 33, Nº1, January / February 2019

80 drugs that cannot be withdrawn from patients during data collection, and the inclusion of patients with different disease severity and, consequently, different cardiovascular conditions. Other methods to assess the CAM consist of standardized autonomic functional tests, including controlled breathing (CB) techniques, which promote the increase of respiratory sinus arrhythmia frequently employed as an index of cardiac parasympathetic control. During CB, the oscillatory components present in the high frequency band (0.15 to 0.4 Hz) of HRV, related to cardiac parasympathetic activity, are generally potentiated 1,14-16 and sensitive changes in the RRi are documented. Considering these assumptions, the objective of the present study was to evaluate and compare the CAM in COPD patients with CAM in healthy people, subjected to spontaneous breathing (SB) and CB trials, to identify the presence of cardiac dysautonomia in COPD and how much the CB may interfere with cardiac modulation of these patients. Method Cross-sectional observational study approved by the Ethics Committee in Research Involving Human Beings of the Pontifical Catholic University of Campinas (PUC Campinas – approval number 393.938), São Paulo state, Brazil. Selection of Volunteers From a total of 40 COPD patients preselected from the outpatient physiotherapy clinic, 18 met the inclusion criteria. The sample calculation (20% error margin and 90% confidence level) indicated a minimum of 13 COPD patients. All of them were clinically stable and had mild or moderate COPD, with clinical diagnosis confirmed by specialists. Also, they were ex-smokers (who had quit smoking at least 6 months before intervention), non-alcoholic, did not participate in any physical activity program, and had a body mass index (BMI) between 20 and 35 kg/m². In addition, a further 12 healthy individuals (control group - CG) were selected, who met the following inclusion criteria: age group similar to that of the COPD, BMI between 20 and 35 kg/m², had not performed any regular physical activity in the last six months and did not use any medication. The study was conducted at the outpatient physiotherapy clinic of PUCCampinas andall participants signed the consent form developed in accordance with Resolution 466/12 of the National Health Council. Anthropometric and Clinical Assessment The clinical assessment consisted of clinical history, measurement of heart rate (HR) and blood pressure (BP), cardiac and pulmonary auscultation, and measurement of peripheral oxygen saturation (SpO 2 ) by a pulse oximeter (Nonin ® , USA). Anthropometric evaluation consisted of the measurement of weight and height using the Filizola ® scale (São Paulo, Brazil), for BMI calculation. Heart Rate Measurement in SB and CB Before heart rate measurement in SB or CB conditions, we confirmed that each volunteer had followed the protocol instructions to refrain from tea, soda, coffee or chocolate on the day of registration and that they had had a good night’s sleep before the test. Heart rate recording was performed using a Polar RS800CX ® heart ratemonitor (Kempele, Finland), in a room at 23°C of temperature. The volunteers were instructed to relax, and not to move or talk during the recordings. First, participants were asked to stand on a bench, where they remained for 5min before the beginning of the recordings. During the first five minutes of heartbeat recording, the volunteers were asked to breath spontaneously, followed by another five minutes of CB. CBwas performed by 5 seconds (s) for inspiration and 5 s for expiration, at six respiratory cycles per minute, as proposed by Andresen et al., 17 Instructions on breathing were given orally by the investigator who performed the test and used a timer to control the process. Participants were asked to perform diaphragmatic breathing, i.e., by contracting the diaphragm. Subsequently, the RRi recordings were sent to a computer via an interface (Polar IR ® interface - Kempele, Finland), and HRV was analyzed using the Polar Precision Performance ® software (Kempele, Finland). Data Analysis Since HRV analysis was based on RRi recordings obtained under controlled conditions, there was a great concern about possible artifacts, and thus a very narrow filter (of the own software) was applied. Paschoal et al. Cardiac autonomic modulation in COPD Int J Cardiovasc Sci. 2020;33(1):79-86 Original Article