Key result
Nocturnal CPAP cuts daytime MSNA by ~10 bursts/min in heart failure patients with OSA.
Why the study?
Daytime muscle sympathetic nerve activity is elevated in HF patients with coexisting OSA, and although abolishing OSA with CPAP lowers morning systolic BP, it was uncertain whether these BP reductions are associated with reduced sympathetic vasoconstrictor tone.
Does nocturnal continuous positive airway pressure reduce daytime muscle sympathetic nerve activity, morning systolic blood pressure, and heart rate in medically treated heart failure patients with moderate to severe obstructive sleep apnea?
RCT (n=17)
Randomly allocated
Does nocturnal continuous positive airway pressure reduce daytime muscle sympathetic nerve activity, morning systolic blood pressure, and heart rate in medically treated heart failure patients with moderate to severe obstructive sleep apnea?
Nocturnal CPAP therapy for 1 month significantly reduces daytime sympathetic vasoconstrictor tone, morning systolic blood pressure, and heart rate in patients with HFrEF and moderate to severe obstructive sleep apnea.
Answers are grounded in this paper and cite their sources.
May link morning BP reductions to lower sympathetic tone in treated HF-OSA; leaves open whether this mechanism improves outcomes.
Objectives This study was designed to determine whether reductions in morning systolic blood pressure (BP) elicited by treatment of moderate to severe obstructive sleep apnea (OSA) in heart failure (HF) patients are associated with a reduction in sympathetic vasoconstrictor tone. Background Daytime muscle sympathetic nerve activity (MSNA) is elevated in HF patients with coexisting OSA. In our recent randomized trial in HF, abolition of OSA by continuous positive airway pressure (CPAP) increased left ventricular ejection fraction (LVEF) and lowered morning systolic BP. Methods Muscle sympathetic nerve activity, BP, and heart rate (HR) of medically treated HF patients (EF <45%) and OSA (apnea-hypopnea index > or =20/h of sleep) were recorded on the morning after overnight polysomnography, and again one month after patients were randomly allocated nocturnal CPAP treatment or no CPAP (control). Results In nine control patients, there were no significant changes in the severity of OSA, MSNA, systolic BP, or HR. In contrast, in the 8 CPAP-treated patients, OSA was attenuated, and there were significant reductions in daytime MSNA (from 58 +/- 4 bursts/min to 48 +/- 5 bursts/min; 84 +/- 4 bursts/100 heart beats to 72 +/- 5 bursts/100 heart beats; p < 0.001 and p = 0.003, respectively), systolic BP (from 135 +/- 5 mm Hg to 120 +/- 6 mm Hg, p = 0.03), and HR (from 69 +/- 2 min(-1) to 66 +/- 2 min(-1); p = 0.013). Conclusions Treatment of coexisting OSA by CPAP in HF patients lowers daytime MSNA, systolic BP, and HR. Inhibition of increased central sympathetic vasoconstrictor outflow is one mechanism by which nocturnal CPAP reduces awake BP in HF patients with moderate to severe OSA.
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Bradley et al. (2005) conducted an RCT in Heart failure with moderate to severe obstructive sleep apnea (n=17). Nocturnal continuous positive airway pressure (CPAP) vs. No CPAP (control) was evaluated on Daytime muscle sympathetic nerve activity (MSNA, bursts/min) (p=<0.001). Nocturnal CPAP significantly lowered daytime MSNA (58 to 48 bursts/min, p<0.001) and systolic BP (135 to 120 mm Hg, p=0.03) in HF patients with OSA.
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