Abstract
INTRODUCTION: Patients with COPD have increased respiratory loads and altered blood gases, both of which affect vascular function and sympathetic activity. Sleep, particularly rapid eye movement (REM) sleep, is known to exacerbate hypoxia and respiratory loads. Therefore, we hypothesize that nasal high flow (NHF), which lowers ventilatory loads, reduces sympathetic activity during sleep and that this effect depends on COPD severity. METHODS: We performed full polysomnography in COPD patients (n=17; FEV(1), 1.6±0.6 L) and in matched controls (n=8). Participants received room air (RA) at baseline and single night treatment with O(2) (2 L/min) and NHF (20 L/min) in a random order. Finger pulse wave amplitude (PWA), a measure of vascular sympathetic tone, was assessed by photoplethysmography. Autonomic activation (AA) events were defined as PWA attenuation ≥30% and indexed per hour for sleep stages (AA index [AAI]) at RA, NHF, and O(2)). RESULTS: In COPD, sleep apnea improved following O(2) (REM-apnea hypopnea index [AHI] with RA, O(2), and NHF: 18.6±20.9, 12.7±18.1, and 14.4±19.8, respectively; P=0.04 for O(2) and P=0.06 for NHF). REM-AAI was reduced only following NHF in COPD patients (AAI-RA, 21.5±18.4 n/h and AAI-NHF, 9.9±6.8 n/h, P=0.02) without changes following O(2) (NHF-O(2) difference, P=0.01). REM-AAI reduction was associated with lung function expressed as FEV(1) and FVC (FEV(1): r=-0.59, P=0.001; FEV(1)/FVC: r=-0.52 and P=0.007). CONCLUSION: NHF but not elevated oxygenation reduces peripheral vascular sympathetic activity in COPD patients during REM sleep. Sympathetic off-loading by NHF, possibly related to improved breathing mechanics, showed a strong association with COPD severity.