IJCS | Volume 33, Nº1, January / February 2019

82 Table 1 - Clinical and anthropometric characteristics of the study groups COPD (n = 18) Control group (n = 12) p-values Age (years) 62.1 ± 8.7 47.9 ± 19.0 0.34 Weight (kg) 69.4 ± 16.5 63.7 ± 10.3 0.89 Height (cm) 159.8 ± 8.9 159.9 ± 8.0 0.98 BMI (kg/m²) 26.9 ± 5.4 25.1 ± 4.0 0.77 Rest systolic BP (mmHg) 125.5 ± 17.8 110.0 ± 12.0 p = 0.007* Rest diastolic BP (mmHg) 78,8 ± 10.2 69.1 ± 7.9 p = 0.01* Rest HR (bpm) 72.6 ± 12.2 73.9 ± 12.1 0.87 Rest resp. freq. (rpm) 18.0 ± 2.8 15.5 ± 2,8 0.34 SpO 2 95.3 ± 1.5 97.1 ± 1.8 p = 0.006* COPD: chronic obstructive pulmonary disease; BMI: body mass index; HR: heart rate; bpm: beats per minute; rpm: respiration per minute; BP: blood pressure; SpO 2 : peripheral oxygen saturation; * p ≤ 0.05 paired Student’s t test; data in mean ± standard deviation. Table 2 - Parameters of time and frequency domains of the heart rate variability during spontaneous breathing (SB) COPD (n = 18) CG (n = 12) p-values TD RRi (ms) 889.0 902.5 0.32 Sd RRi (ms) 36.6 53.2 0.04* RMSSD (ms) 26.6 42.1 0.03* pNN50 (%) 5.4 8.5 0.47 FD TP (ms²/Hz) 2,011.6 28,322.8 p < 0.0001* LF(ms²) 472.8 1,186.3 0.81 LF (un) 63.9 53.4 0.54 HF (ms²) 330.7 800.5 p = 0.04* HF (un) 36.0 46.2 0.54 LF/HF 2.25 2.1 0.62 CG: control group; COPD: chronic obstructive pulmonary disease; TD: time domain; FD: frequency domain; SD: standard deviation; RRi: RR interval; RMSSD: root mean square of the standard deviation of RRi; pNN50: percentage of RRi adjacent with equal or superior values of 50ms; TP: total power; LF: low frequency; HF: high frequency; ms: milliseconds; Hz: Hertz; u.n.: normalized units. Test U of Mann-Whitney; * p ≤ 0.05. capacity acquired through physical training, caffeine intake, sleep hours, room temperature and circadian rhythm of HR. 19,21 In addition, medications used by the patients may have influenced the results. However, one of the objectives of this investigation was to know how patients with COPD would react when they were submitted to SB and CB trials at the same conditions of their daily lives, which included their usual medications. Also, despite our concern about the influence of medications on HRVmeasurements, it is worthmentioning that there are studies that have concluded that anticholinergic or β -agonist drugs do not interfere with these measures. The only variable related to anthropometric data that may draw attention would be age, particularly due to the high standard deviation in the CG. However, no significant difference between the groups was found according to the p-value (Table 1). Paschoal et al. Cardiac autonomic modulation in COPD Int J Cardiovasc Sci. 2020;33(1):79-86 Original Article