Chronic obstructive pulmonary disease severity and its association with obstructive sleep apnea syndrome: impact on cardiac autonomic modulation and functional capacity

Figures & data

Figure 1 Volunteer flowchart.

Abbreviations: CEME, Municipal Health Specialty Center of São Carlos; COPD, chronic obstructive pulmonary disease; OSAS, obstructive sleep apnea syndrome; USE, Pulmonary Ambulatory of the School Health Unit.

Table 1 Volunteers’ baseline characteristics

Demographic data	COPD (n = 12)	COPD+OSAS (n = 12)	P-value
Age (years)	64.83 ± 1.69	64.17 ± 2.48	0.82
Sex female/male, n (%)	2 (16.7)/10 (83.3)	2 (16.7)/10 (83.3)	1.00
Weight (kg)	73.32 ± 5.61	75.53 ± 3.58	0.74
BMI (kg/m^2)	25.49 ± 1.70	27.13 ± 1.15	0.43
mMRC, 0/1/2/3/4, n (%)	1 (8.3)/1 (8.3)/2 (16.6)/4 (33.3)/4 (33.3)	1 (8.3)/4 (33.3)/2 (16.6)/1 (8.3)/4 (33.3)	0.46
Smoking habits
Never/ex/current	0.12.0	0.12.0	0.35
Pack years	53.33 ± 29.57	67.17 ± 41.09
Pulmonary function
FEV1, %pred	42.70 ± 16.56	61.32 ± 18.79	0.01*
FEV1/FVC, %pred	41.84 ± 12.22	56.29 ± 12.07	0.00*
COPD 1 and 2, n (%)	4 (33)	9 (75)	0.04*
COPD 3 and 4, n (%)	8 (67)	3 (25)	0.04*
OSA
AHI	5.81 ± 4.44	26.72 ± 13.42	0.00*
ODI	10.27 ± 7.10	46.45 ± 90.82	0.01*
SaO2 <90%, min	193.81 ± 166.72	64.48 ± 48.57	0.04*
SaO2 <80%, min	1.90 ± 3.78	1.50 ± 2.71	0.94
Therapy, n (%)
SABA	4 (33.3)	5 (41.7)	0.84
SAMA	Not applicable	1 (8.3)	0.84
LABA	9 (75)	10 (83.3)	0.84
LAMA	6 (50)	6 (50)	0.84
ICS	6 (50)	6 (50)	0.84
OCS	1 (8.33)	Not applicable	0.84
Theophylline	2 (16.6)	1 (8.33)	0.84
Antihistamine	Not applicable	1 (8.33)	0.84

Notes:

* Significant difference between COPD group and the COPD+OSAS group. The variables are presented as mean ± SD.

Abbreviations: COPD, chronic obstructive pulmonary disease; OSAS, obstructive sleep apnea syndrome; BMI, body mass index; mMRC, modified Medical Research Council dyspnea scale; FEV₁, forced expiratory volume in 1 second; pred, predicted; FVC, forced vital capacity; AHI, apnea-hypopnea index; ODI, oxygen desaturation index; SaO2 <90%, saturation time <90%; SaO2 <80%, saturation time <80%; SABA, short-acting beta2-agonist; SAMA, short-acting muscarinic agonist; LABA, long-acting beta2-agonist; LAMA, long-acting muscarinic agonist; ICS, inhaled corticosteroids; OCS, oral corticosteroids.

Table 2 HRV indices before and after active postural change from supine position to orthostatic position

	COPD (n = 12)		COPD+OSAS (n = 12)		Group	Position	Interaction
	Supine	Orthostasis	Supine	Orthostasis
Time	–	–	–	–
iRR	794 ± 103	719 ± 114*	818 ± 123	764 ± 97*	0.27	0.04	0.74
SDNN	13.9 ± 5.3	11.7 ± 6.6	16.1 ± 5.8	15.2 ± 7.3	0.12	0.38	0.73
RMSSD	14.3 ± 7.2	11.5 ± 6.5	15.8 ± 7.9	13.7 ± 6.9	0.42	0.21	0.78
pnn50	1.7 ± 2.8	0.6 ± 1.1	1.8 ± 3.7	0.5 ± 0.9	0.98	0.11	0.85
TINN	67.0 ± 22.2	55.4 ± 30.4	77.9 ± 28.3	77.0 ± 34.6	0.06	0.46	0.52
Frequency	–	–	–	–
LF_abs	79.8 ± 84.8	69.2 ± 66.6	156.7 ± 107.7+	161.3 ± 144.2+	,0.01	0.92	0.80
HF_abs	67.5 ± 47.8	60.9 ± 101.2	106.7 ± 115.1	70.6 ± 61.3	0.39	0.33	0.55
LF_nu	50.1 ± 19.9	58.3 ± 19.5	62.9 ± 14.8+	68.6 ± 14.7+	0.02	0.17	0.80
HF_nu	49.7 ± 19.8	41.2 ± 19.4	36.7 ± 14.8	31.0 ± 14.6	0.02	0.16	0.78
LF/HF	1.3 ± 1.0	3.0 ± 4.7	2.1 ± 1.2	4.6 ± 7.4	0.37	0.11	0.75
Non-linear	–	–	–	–
SD1	10.4 ± 5.1	8.1 ± 4.6	11.2 ± 5.6	9.7 ± 4.9	0.43	0.21	0.78
SD2	16.3 ± 6.6	14.3 ± 8.4	19.7 ± 6.7	18.9 ± 9.5	0.08	0.53	0.78

Notes:

* Significant difference between supine position and orthostatic position.

+ Significant difference between the COPD group and the COPD+OSAS group. The variables are presented as mean ± SD.

Abbreviations: HRV, heart rate variability; COPD, chronic obstructive pulmonary disease; OSAS, obstructive sleep apnea syndrome; iRR, interval between consecutive heart beats; SDNN, standard deviation of all R-R intervals; RMSSD, square root of the mean squared differences between adjacent R-R intervals; pnn50, percentage of adjacent R-R intervals with duration difference greater than 50 ms; TINN, triangular interpolation of the iRR interval histogram; LF_abs, absolute power in the low frequency band; HF_abs, absolute power in the high frequency band; LF_nu, normalized power in the low frequency band; HF_nu, normalized power in the high frequency band; LF/HF, low frequency to high frequency ratio; SD1, standard deviation of instantaneous beat-to-beat variability; SD2, long-term standard deviation of the continuous R-R interval.

Table 3 HRV indices in sitting position and during RSA-m

Time	COPD (n = 12)		COPD+OSAS (n = 12)		Group	Maneuver	Interaction
	Sitting	RSA-m	Sitting	RSA-m
iRR	773 ± 113	757 ± 89	815 ± 116	802 ± 98	0.15	0.62	0.95
SDNN	14.4 ± 6.1	26 ± 16.2*	17.3 ± 7.1	34.8 ± 20.3*	0.15	0.00	0.46
RMSSD	13.2 ± 5.1	19.9 ± 19.5	17.1 ± 8.1	22.7 ± 13.6	0.37	0.10	0.87
pnn50	0.4 ± 0.9	4.1 ± 11.9	1.9 ± 3.4	4.6 ± 8.5	0.64	0.15	0.81
TINN	70 ± 29.1	123.7 ± 83.0*	87.5 ± 35.3	160 ± 87.2*	0.15	0.00	0.61

Notes:

* Significant difference between sitting position and RSA-m. The variables are presented as mean ± SD.

Abbreviations: HRV, heart rate variability; RSA-m, respiratory sinus arrhythmia maneuver; COPD, chronic obstructive pulmonary disease; OSAS, obstructive sleep apnea syndrome; iRR, interval between consecutive heart beats; SDNN, standard deviation of all R-R intervals; RMSSD, square root of the mean squared differences between adjacent R-R intervals; pnn50, percentage of adjacent R-R intervals with duration difference greater than 50 ms; TINN, triangular interpolation of the iRR interval histogram.

Table 4 6MWT parameters

	COPD (n = 12)	COPD+OSAS (n = 12)	P-value
Rest
SBP (mmHg)	118 ± 10	129 ± 9	0.01*
HR (bpm)	82 ± 11	79 ± 13	0.56
SpO2	93 ± 3	95 ± 3	0.13
BORG D	0 ± 1	0 ± 0	0.10
BORG P	0 ± 1	0 ± 1	0.75
Peaks
SBP (mmHg)	147 ± 15	159 ± 25	0.17
HR (bpm)	104 ± 17	106 ± 13	0.72
SpO2	87 ± 9	91 ± 4	0.21
BORG D	3 ± 2	2 ± 1	0.04*
BORG P	4 ± 3	1 ± 1	0.01*
Covered distance
CD predicted (m)	557.17 ± 38.48	571.58 ± 41.42	0.38
CD reached (m)	362.12 ± 123.14	419.04 ± 77.66	0.18
% predicted	64.58 ± 20.03	73.45 ± 13.54	0.21
CDR COPD 1 and 2/CDR COPD+OSAS 3 and 4	320 ± 137	448 ± 33.05	0.18
CDR COPD 3 and 4/CDR COPD+OSAS 1 and 2	394 ± 114	409 ± 87	0.76

Notes:

* Significant difference between groups (unpaired t-test). The variables are presented as mean ± SD.

Abbreviations: 6MWT, 6-minute walk test; COPD, chronic obstructive pulmonary disease; OSAS, obstructive sleep apnea syndrome; SBP, systolic blood pressure; HR, heart rate; SpO₂, peripheral oxygen saturation; BORG D, dyspnea Borg Scale; BORG P, leg discomfort Borg Scale; CD, covered distance; CDR, covered distance reach.