How does serum brain natriuretic peptide level change under nasal continuous positive airway pressure in obstructive sleep apnea-hypopnea syndrome?

Figures & data

Table 1 Clinical characteristics, results of sleep studies, and spirometric measurements: comparison of OSAHS patients, normotensive and hypertensive patients, and controls

Characteristics/groups	1 Control (n=21)	2 OSAHS (n=43)	3 Normotensive OSAHS (n=24)	4 Hypertensive OSAHS (n=19)	Total (n=64)
Age (years)	41.3±10.07	46±11.05	43.8±12.50	48.6±8.40	44.4±10.90
Sex (male/female)	10/11	22/21	14/10	8/11	32/32
Smoking status (%)	19.0	27.9	33.3	21.1	25.0
ESS (mean±SD)	7.7±4.79	10.3±3.24*	9.6±3.40	10.2±2.87**	9.4±3.97
BMI (kg/m^2)	32.9±5.90	34.2±6.51	32±7.20	36.9±4.30***	33.8±6.30
Average BP (mmHg)	9.4±0.60	9.6±0.70	9.2±0.50	10.0±0.70****	9.5±0.70
AHI (mean±SD)	2.6±1.27	28.0±16.95	28.2±18	29.7±16	19.65±18.34
ODI	2.1±2.14	25.5±22.09*****	22.3±21.60	29.4±22.60	17.8±21.19
FEV1 ml (mean±SD)	3.0±0.57	3.1±0.63	3.1±0.63	3.1±0.65	3.1±0.61
FVC ml (mean±SD)	3.6±0.63	3.7±0.78	3.7±0.78	3.8±0.79	3.7±0.73
FEV1/FVC (mean±SD)	83.6±5.69	83.25±5.95	83.6±5.40	82.8±6.69	83.4±5.82

OSAHS, obstructive sleep apnea-hypopnea syndrome; ESS, Epworth sleepiness scale; BMI, body mass index; BP, blood pressure; AHI, apnea-hypopnea index; SD, standard deviation; ODI, oxygen desaturation index; FEV1, first second forced expiratory volume; FVC, forced vital capacity.

*Patients with OSAHS were more somnolent than control subjects (p=0.013). **Hypertensive OSAHS patients had a higher ESS score than normotensive OSAHS patients (p=0.015). ***BMI was significantly higher in hypertensive OSAHS patients than in normotensive OSAHS patients (p=0.032). ****Average blood pressure was significantly higher in hypertensive OSAHS patients than in normotensive patients (p=0.01) and in controls (p=0.014). *****Desaturation index was significantly altered in OSAHS patients in comparison with controls (p=0.0001).

Table 2 Baseline clinical and polygraph data according to baseline BNP levels

	BNP <37 pg/ml (n=53)	BNP ≥37 pg/ml (n=11)	p
Sex (male/female)	27/26	5/6	0.07
Age (years)	42.7±10.16	53±10.58	0.003
Smoking status (%)	93.7	6.3	0.18
ESS	9.3±4.05	10.4±3.58	0.408
BMI (kg/m^2)	33.3±6.67	36.1±3.29	0.17
Creatinine clearance (ml/min)	114±31.10	117.3±27	0.13
Blood sugar level (mmol/L)	5.4±0.59	5.7±0.98	0.15
AHI	16.7±17.10	33.6±18.42	0.005
Mean SpO2 (%)	94.7±2.85	90.8±3.26	<0.0001
Minimal SpO2 (%)	85.6±8.89	75.3±11.43	0.002
ODI (/h)	13.9±18.64	36.6±23.43	0.001
TST90 (%)	6.1±12.95	20.2±12.53	0.002

BNP, brain natriuretic peptide; n, number; %, percentage; ESS, Epworth sleepiness scale; BMI, body mass index; AHI, apnea-hypopnea index; SpO₂, transcutaneous oxygen saturation; TST90, total sleep time with SpO₂ <90%; ODI, oxygen desaturation index. Bold values indicate statistically significant difference.

Fig. 1 Distribution of BNP by OSAHS severity. OSAHS, obstructive sleep apnea-hypopnea syndrome; BNP, brain natriuretic peptide.

Table 3 OSAHS classification according to baseline BNP levels (pg/ml)

	Mild OSAHS	Moderate OSAHS	Severe OSAHS	Total
BNP (pg/ml)	12.2±9.13*	24.4±17.13	26.3±12.93	22.3±14.79
BNP <37 pg/ml (n,%)	10 (100)	10 (62.5)	12 (61.6)	32
BNP ≥37 pg/ml (n,%)	0 (0)	6 (62.5)	5 (38.4)	11

OSAHS, obstructive sleep apnea-hypopnea syndrome; BNP, brain natriuretic peptide; n, number;%, percentage.

*The mean serum BNP level in the mild OSAHS group was significantly lower than in the severe OSAHS group (p=0.029).

Table 4 Baseline patient characteristics according to baseline AHI

Settings/groups	AHI <5 (n=21)	AHI ≥5 (n=43)	p
BNP (pg/ml)	9.2±6.75	22.3±14.79	<0.001
Males/females (n)	10/11	22/21	0.79
Age (years)	41.3±10.07	46±11.05	0.11
Smoking (%)	35.4	64.6	0.44
Average BP (mmHg)	9.4±0.60	9.6±0.70	0.33
ESS (points)	7.7±4.78	10.3±3.24	0.013
BMI (kg/m^2)	32.9±5.90	34.2±6.51	0.46
AHI (events/h)	2.6±1.26	28±16.95	<0.001
Mean SpO2 (%)	96.6±1.39	92.8±3.21	<0.001
Min SpO2 (%)	92.3±4.30	79.7±9.46	<0.001
FVC (%)	3.6±0.63	3.7±0.77	0.41
FEV1 (%)	3.0±0.57	3.1±0.63	0.45
Blood sugar level (mmol/L)	5.2±0.56	5.6±0.70	0.029
Creatinine clearance (ml/min)	113.5±34.20	115.1±28.50	0.22

AHI, apnea-hypopnea index; BNP, brain natriuretic peptide; n, number; %, percentage; BP, blood pressure; ESS, Epworth sleepiness scale; BMI, body mass index; SpO₂, transcutaneous oxygen saturation; FVC, forced vital capacity; FEV1, first second forced expiratory volume. Bold values indicate statistically significant difference.

Fig. 2 The BNP levels in hypertensive OSAHS were significantly higher than in normotensive OSAHS patients (18.05±11.73 pg/ml) (p=0.039) and controls (9.26±6.75 pg/ml) (p=0.001). Normotensive OSAHS patients had higher baseline BNP levels in comparison with controls, but there was no statistically significant difference between the two groups (p=0.058). Boxes represent values within the interquartile ranges. Whiskers represent the data range, and the lines across the boxes represent the median values. The bottom and top of the boxes are the 25th and 75th percentiles, respectively. OSAHS, obstructive sleep apnea-hypopnea syndrome; BNP, brain natriuretic peptide.

Fig. 3 Effect of CPAP treatment in hypertensive (n=11) and normotensive (n=12) OSAHS patients compared with controls (n=21). OSAHS, obstructive sleep apnea-hypopnea syndrome; BNP, brain natriuretic peptide; CPAP, continuous positive airway pressure. Red: baseline levels; blue: levels after 6 months of CPAP therapy.

Fig. 4 In linear regression, the changes in BNP levels in 23 patients OSAHS after 6-month CPAP treatment were more important in OSAHS patients with higher baseline BNP levels. Note that hypertensive OSAHS patients had the higher delta BNP (T₆–T₀) (p=0.015, r=0.72) in comparison with normotensive OSAHS patients (p=0.03, r=0.62). OSAHS, obstructive sleep apnea-hypopnea syndrome; BNP, brain natriuretic peptide; CPAP, positive airways pressure. Blue: hypertensive OSAHS; red: normotensive OSAHS.

Fig. 5 In linear regression, the changes in BNP levels in 23 patients OSAHS after 6-month CPAP treatment were more pronounced in OSAHS patients with prolonged nocturnal desaturation (TST90) (r=+0.65, p=0.001). OSAHS, obstructive sleep apnea-hypopnea syndrome. BNP, brain natriuretic peptide; CPAP, continuous positive airway pressure.