Cardiac Sympathetic Hyperactivity in Patients with Chronic Obstructive Pulmonary Disease and Obstructive Sleep Apnea

Figures & data

Table 1. Anthropometric data, smoking habits, and sleepiness questionnaire score.

	COPD	OSA	OSA + COPD
	(n = 16)	(n = 24)	(n = 14)
Age, years	70 [13]^Footnote‡	59 [8.5]^Footnote†	61 [11.5]
BMI, kg/m^2	29.1 [7.5]^Footnote*	32.4 [4.4]	34.2 [7.1]^Footnote†
Neck circumference, cm	N/A	45.0 [5]	46.5 [4.3]
Waist circumference, cm	N/A	116.9 [14.8]	120.5 [12.8]
ESS	N/A	8.5 [4]	9.0 [3.5]
Smoking history, n (%)	16 (100) ^Footnote‡	10 (42)^Footnote*	13 (93)^Footnote‡

Data are expressed as median [interquartile range].

^* significantly different vs OSA + COPD (p < 0.05)

^† significantly different vs COPD (p < 0.05)

^‡ significantly different vs OSA (p < 0.05).

BMI, body mass index; COPD, chronic obstructive pulmonary disease; ESS, Epworth sleepiness scale; N/A, not available; OSA, obstructive sleep apnea.

Table 2. Co-morbidities and medications of the patients analyzed.

	COPD	OSA	OSA + COPD
Co-morbidities	(n = 16)	(n = 24)	(n = 14)
Asthma, n (%)	1 (6)	1 (4)	1 (7)
Allergies, n (%)	1 (6)	1 (4)	1 (7)
Hypertension, n (%)	9 (56)	15 (63)	9 (64)
Ischemic cardiomyopathy, n (%)	2 (12.5)	1 (4)	0 (0)
Diabetes, n (%)	2 (12.5)	3 (12.5)	4 (29)
Medications
ACE-I/ARB, n (%)	8 (50)	11 (46)	6 (43)
β-Blockers, n (%)	4 (25)	7 (17)	3 (21)
Calcium antagonists, n (%)	2 (12.5)	4 (29)	2 (14)
Diuretics, n (%)	4 (25)	5 (21)	4 (29)
Anticholinergics, n (%)	11 (69)^Footnote‡	0 (0)^Footnote†^Footnote*	3 (21)^Footnote‡
β2-Agonists, n (%)	12 (75)^Footnote‡	0 (0)^Footnote†^Footnote*	7 (50)^Footnote‡
Inhaled corticosteroids, n (%)	3 (18.7)^Footnote‡	0 (0)^Footnote†^Footnote*	3 (21)^Footnote‡
Oral hypoglycemics, n (%)	2 (12.5)	3 (12,5)	4 (29)
Statins, n (%)	3 (18.7)	2 (8)	2 (14)

^* Significantly different vs OSA+COPD (p < 0.05)

^† significantly different vs COPD (p < 0.05)

^‡ significantly different vs OSA (p < 0.05).

COPD, chronic obstructive pulmonary disease; OSA, obstructive sleep apnea; ACE-I, angiotensin-converting enzyme inhibitors; ARB, angiotensin receptor blocker.

Table 3. Functional data from polygraphy, spirometry, and arterial blood gases.

	COPD	OSA	OSA + COPD
	(n = 16)	(n = 24)	(n = 14)
AHI, events/hour	2.5 [4.4]^Footnote‡^Footnote*	35.5 [22.8]^Footnote†	41.0 [28.8]^Footnote†
ODI, events/hour	2.0 [4.7]^Footnote‡^Footnote*	35.8 [22.1]^Footnote†	40 [28.6]^Footnote†
Mean nocturnal SaO2, %	94.3 [3.2] ^Footnote‡^Footnote*	91.5 [2.6]^Footnote†	90.0 [2.9]^Footnote†
T90, %	0.6 [10.2] ^Footnote‡^Footnote*	17.5 [27.3]^Footnote†	22.5 [41.2]^Footnote†
Minimum SaO2, %	86.0 [3.3] ^Footnote‡^Footnote*	75.5 [8.0]^Footnote†	72.5 [9.3]^Footnote†
FEV^1, % pred.	62.5 [13.3]^Footnote‡	94.0 [7.5]^Footnote†^Footnote*	66.0 [9.3]^Footnote‡
FEV^1/FVC, % pred.	73.0 [13.5]^Footnote‡	103.5 [10.0]^Footnote†^Footnote*	85.5 [8.5]^Footnote‡
TLC (He), % pred.	103.5 [17.0]^Footnote*	96.5 [17.0]	94.5 [18.0]^Footnote†
RV (He), %pred.	113.0 [18.5]	99.0 [25.0]	115.0 [24.3]
DLCO, % pred.	95.5 [41.0]	111.0 [21.8]	110 [16.5]
KCO, % pred.	83.0 [50.0]^Footnote‡	113.0 [24.8]^Footnote†	113 [30.6]
pH	7.42 [0.04]	7.41 [0.02]	7.41 [0.06]
PaO2, KPa	10.1 [6.5]	10.3 [12.4]	10.1 [10.0]
PaCO2, KPa	5.2 [5.3]	5.3 [4.8]	5.8 [11.1]
HCO3^−, mmol/l	25.2 [1.4]	25.0 [2.7]	26 [4.4]

Data are expressed as median [interquartile range].

^* significantly different vs OSA + COPD (p < 0.05)

^† significantly different vs COPD (p < 0.05)

^‡ significantly different vs OSA (p < 0.05).

COPD, chronic obstructive pulmonary disease; OSA, obstructive sleep apnea; AHI, apnea–hypopnea index; ODI, oxygen desaturation index; SaO₂, oxyhemoglobin saturation; T90, % analysis time with SaO₂<90%; FEV¹, forced expiratory volume in 1st second; FVC, forced vital capacity; TLC (He), total lung capacity determined with helium; RV (He), residual volume determined with helium; DL_CO, diffusing lung capacity of carbon monoxide; PaO₂, partial pressure of oxygen; PaCO₂, partial pressure of carbon dioxide; KCO, Carbon Monoxide transfer coefficient.

Table 4. Heart rate variability indices in time and frequency domain.

	COPD	OSA	OSA + COPD
	(n = 16)	(n = 24)	(n = 14)
Mean heart rate, beats/min	67 [16]	67 [19]	75.2 [13.7]
SDNN	34.3 [12.3]	31.8 [11.4]	28.9 [8.5]
RMSSD	22.5 [15.3]^Footnote*	19.3 [10.4]	12.2 [9.9]^Footnote†
Triangular index	8.3 [3.1]	8.1 [3.1]	7.0 [2.1]
Total power, msec^2	218 [374]	142 [263]	155 [147]
LF power, msec^2	126 [205]	109 [148]	108 [113]
LF power, nu	0.57 [0.22]^Footnote*	0.66 [0.26]^Footnote*	0.82 [0.18]^Footnote†^Footnote‡
HF power, msec^2	104 [83]^Footnote*	55 [115]	28 [24]^Footnote†
HF power, nu	0.44 [0.21]^Footnote*	0.34 [0.26]^Footnote*	0.18 [0.18]^Footnote†

Data are expressed as median [interquartile range].

^* significantly different vs OSA + COPD (p < 0.05)

^† significantly different vs COPD (p < 0.05)

^‡ significantly different vs OSA (p < 0.05).

COPD, chronic obstructive pulmonary disease; OSA, obstructive sleep apnea; SDNN, standard deviation of the normal-to-normal intervals; RMSSD, square root of the mean squared differences of successive normal-to-normal intervals; LF, low frequency; HF, high frequency; nu, normalized units.

Figure 1. Patients with OSA and COPD have a higher index of sympathovagal balance (LF/HF ratio) of heart rate variability as compared with patients with a single disease. COPD, chronic obstructive pulmonary disease; OSA, obstructive sleep apnea; LF, low frequency; HF, high frequency.

Figure 2. Relationship between residual volume (RV) expressed as % predicted (%pred) and the ratio between low frequency and high frequency of heart rate variability power spectrum (LF/HF) in 14 patients with COPD + OSA. COPD, chronic obstructive pulmonary disease; OSA, obstructive sleep apnea.

Figure 3. Relationship between apnea–hypopnea index (AHI) and the ratio between low frequency and high frequency of heart rate variability power spectrum (LF/HF) in all patients included in the analysis.

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