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Vascular responses to hypoxia are not impaired in obstructive sleep apnoea patients free of overt cardiovascular disease.

Abstract：

NEW FINDINGS:What is the central question of this study? Does treatment of obstructive sleep apnoea (OSA) with nocturnal oxygen or continuous positive airway pressure (CPAP) improve hypoxic vascular responses, which are reportedly impaired in OSA? What is the main finding and its importance? Cerebrovascular and cardiovascular hypoxic responses were not impaired in OSA patients free of overt cardiovascular disease and known risk factors, and were not altered by nocturnal oxygen or CPAP treatment. We conclude that this OSA patient phenotype has normal vascular responses to hypoxia and is unlikely to obtain long term cardiovascular benefits from nocturnal oxygen or CPAP therapy. ABSTRACT:Cerebral blood flow (CBF) and cardiovascular responses to hypoxia are reportedly impaired in obstructive sleep apnoea (OSA) patients and corrected by continuous positive airway pressure (CPAP), beneficial effects that are ascribed to correction of OSA-related intermittent hypoxia (IH). However, CPAP corrects both IH and ancillary OSA features (i.e. intermittent hypercapnia, sympathetic activation, blood pressure surges, negative intrathoracic pressure swings and sleep fragmentation). Whether correction of these ancillary OSA features contribute to CPAP's beneficial effects on vascular hypoxic responses is unknown. Nocturnal oxygen corrects OSA-induced IH, but apnoeas and ancillary features persist. Thus, we examined the effects of nocturnal oxygen and CPAP on cerebrovascular and cardiovascular hypoxic responses in untreated OSA patients. Responses were assessed in 52 OSA patients free of overt cardiovascular disease and known risk factors at baseline, after 2 weeks of nocturnal oxygen (n = 26) or no treatment (n = 26), and after ∼4 weeks of CPAP treatment (n = 40). Twenty-two age-matched controls were assessed at baseline and follow-up visits. Resting, isocapnic euoxia mean blood pressure was decreased following nocturnal oxygen (-3.6 ± 6.0 mmHg; P = 0.006) and CPAP (-4.5 ± 7.5 mmHg; P < 0.001) while cerebrovascular conductance was increased with CPAP (P = 0.001). However, these changes were not different from controls. Unexpectedly, OSA patients and controls had similar hypoxic vascular responses at baseline that were not changed by either nocturnal oxygen or CPAP. We conclude that OSA patients free of overt cardiovascular disease and known risk factors did not have impaired cerebrovascular or cardiovascular responses to hypoxia and are unlikely to obtain long term cardiovascular benefits from nocturnal oxygen or CPAP therapy.

journal_name

Exp Physiol

journal_title

Experimental physiology

authors

Beaudin AE,Hanly PJ,Raneri JK,Sajobi TT,Anderson TJ,Poulin MJ

doi

10.1113/EP086845

subject

Has Abstract

pub_date

2019-04-01 00:00:00

pages

580-600

issue

eissn

0958-0670

issn

1469-445X

journal_volume

104

pub_type

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Vascular responses to hypoxia are not impaired in obstructive sleep apnoea patients free of overt cardiovascular disease.