Effect of Pursed-Lip Breathing in Patients With COPD: Linear and Nonlinear Analysis of Cardiac Autonomic Modulation

Figures & data

Table 1.  Anthropometric and spirometric variables of COPD and control groups

Variables	COPD	Control
Age (years)	67.29 ± 6.87 (68)[63.76 –70.82]	63.2 ± 7.96 (61)[57.92 –66.74]
Weight (Kg)	70.29 ± 11.05^a[64.61 –75.97]	81.85 ± 16.77[72.56 –91.14]
Height (m)	1.66 ± 0.05[1.63 –1.68]	1.69 ± 0.06[1.65 –1.73]
BMI (Kg/m^2)	25.54 ± 4.44[23.25 –27.82]	28.41 ± 4.9[25.7 –31.13]
FEV1/FVC	45.3 ± 9.38 (44.4)^a[40.48 –50.12]	77.25 ± 9.73 (79.6)[71.86 –82.65]
FEV1 (% predicted)	42.19 ± 14.2^b[34.89 –49.5]	102.89 ± 21.88[90.76 –115.01]

Mean ± standard deviation (median) [confidence interval]; ^a Statistically significant difference in relation to control group (Mann-Whitney test; p < 0.05); ^b Statistically significant difference in relation to control group (unpaired t-test; p < 0.05); Abbreviations: BMI (body mass index), FEV₁ (forced expiratory volume in first second); FEV₁/FCV (forced expiratory volume in first second/forced vital capacity ratio).

Table 2.  Analysis of nonlinear HRV indices in each phase of protocol

Variable		Phase I	Phase II	Phase III
SD1 (ms)	COPD	9.45 ± 5.5 (7.6)^ae[6.62 –12.28]	12.32 ± 6.8 (12.2)^f[8.82 –15.82]	10.1 ± 5.24 (8.5)^e[7.4 –12.79]
	Control	14.04 ± 5.14 (13.7)^a[8.7 –27.6]	17.72 ± 5.95 (15.8)[14.42 –21.01]	15.38 ± 5.92 (13.0)[12.1 –18.66]
SD2 (ms)	COPD	31.86 ± 12.83^be[25.26 –38.46]	46.14 ± 27.07^f[32.21 –60.06]	35.61 ± 15.02^e[27.89 –43.34]
	Control	46.66 ± 17.52 (40.8)[36.95 –56.36]	76.49 ± 29.51 (65.5)^c[60.14 –92.84]	50.73 ± 19.96 (44)[39.67 –61.79]
SD1/ SD2	COPD	0.29 ± 0.1 (0.26)[0.24 –0.34]	0.28 ± 0.11 (0.23)[0.22 –0.34]	0.28 ± 0.07 (0.27)[0.24 –0.31]
	Control	0.30 ± 0.08 (0.29)^a[0.26 –0.35]	0.24 ± 0.06 (0.23)[0.21 –0.27]	0.31 ± 0.06 (0.29)[0.27 –0.34]
α1	COPD	1.12 ± 0.18[1.03 –1.22]	1.23 ± 0.29[1.08 –1.38]	1.17 ± 0.20[1.07 –1.28]
	Control	1.05 ± 0.16[0.96 –1.14]	1.38 ± 0.12^d[1.31 –1.4]	1.08 ± 0.14[1.00 –1.16]
α2	COPD	0.97 ± 0.23 (1.01)[0.85 –1.08]	0.62 ± 0.22 (0.64)^cf[0.51 –0.74]	0.85 ± 0.23 (0.89)[0.73 –0.97]
	Control	0.94 ± 0.09[0.89 –0.99]	0.48 ± 0.17^d[0.38 –0.57]	0.88 ± 0.16[0.79 –0.97]

Mean ± standard deviation (median) [confidence interval]; ^aStatistically significant difference in relation to phase II (Friedman's test followed by Dunn's test; p < 0.05); ^bStatistically significant difference in relation to phase II (repeated-measure analysis of variance followed by Tukey's test; p < 0.05); ^cStatistically significant difference in relation to phases I and III of protocol (Friedman's test followed by Dunn's test; p < 0.05); ^dStatistically significant difference in relation to phase I and III of protocol (repeated-measure analysis of variance followed by Tukey's test; p < 0.05); ^eStatistically significant intergroup difference in each phase of protocol (Mann-Whitney test; p < 0.05); ^fStatistically significant intergroup difference in each phase of protocol (unpaired t-test; p < 0.05).

Figure 1.  Poincaré plots of phases of protocol in COPD and control groups.

Table 3.  Analysis of linear HRV variables in each phase of protocol

Variables		Phase I	Phase II	Phase III
SDNN (ms)	COPD	23.61 ± 9.65^ad[18.65 –28.58]	33.87 ± 19.52^e[23.83 –43.91]	26.23 ± 11.09^d[20.53 –31.94]
	Control	34.55 ± 12.71 (29.7)[27.51 –41.59]	55.58 ± 21.08 (49.1)^c[43.91 –67.26]	37.56 ± 14.57 (32.4)[29.49 –45.64]
RMSSD (ms)	COPD	13.34 ± 7.77 (10.8)^bd[9.34 –17.33]	17.39 ± 9.61 (17.2)^e[12.45 –22.34]	14.27 ± 7.39 (12.1)^d[10.46 –18.07]
	Control	19.81 ± 7.24 (19.3)^b[15.8 –23.82]	25 ± 8.41 (22.3)[20.34 –29.65]	21.72 ± 8.37 (18.3)[17.08 –26.36]
LF (ms^2)	COPD	211.76 ± 297.5 (119)^bd[58.79 –364.73]	1182.35 ± 1846.8 (526)^d[232.77 –2131.9]	243.52 ± 259.45 (112)^d[110.13 –376.93]
	Control	365.8 ± 358.06 (195)[167.49 –564.11]	2149.13 ± 1640.5 (1732)^c[1240.5 –3057.7]	518.2 ± 594.67 (299)[188.85 –847.55]
HF (ms^2)	COPD	62.94 ± 79.82 (37)^d[21.89 –103.99]	120.94 ± 181.21 (58)[27.76 –214.12]	76.17 ± 100.56 (33)^d[24.47 –127.88]
	Control	144.86 ± 127.67 (104)[74.15 –215.58]	133.46 ± 99.51 (102)[78.35 –188.58]	182 ± 235.66 (99)[51.48 –312.52]
LF/HF	COPD	5.58 ± 4.84 (3.19)[3.09 –8.07]	16.21 ± 17.25 (12.03)[7.34 –25.08]	4.91 ± 4.47 (4.01)[2.62 –7.21]
	Control	3.07 ± 3.07 (2.17)[1.37–4.78]	26.67 ± 21.08 (15.0)^c[13 –36.35]	3.58 ± 2.84 (2.29)[2.01 –5.15]

Mean ± standard deviation (median) [confidence interval]; ^aStatistically significant difference in relation to phase II (repeated-measure analysis of variance followed by Tukey's test; p < 0.05); ^bStatistically significant difference in relation to phase II (Friedman's test followed by Dunn's test; p < 0.05); ^cStatistically significant difference in relation to phases I and III of protocol (Friedman's test followed by Dunn's test; p < 0.05); ^dStatistically significant intergroup difference in each phase of protocol (Mann-Whitney test; p < 0.05); ^eStatistically significant intergroup difference in each phase of protocol (unpaired t-test; p < 0.05).

Figure 2.  Behavior of respiratory rate during protocol; mean ± standard deviation; ^#significant difference in phase 2 in relation to phase 1 and phase 3 in both groups (repeated-measure analysis of variance followed by Tukey's test); *significant intergroup difference in each phase of protocol (unpaired t-test; p ≤ 0.05).