Effect of supplemental oxygen on blood pressure in obstructive sleep apnea (SOX): A randomised, CPAP withdrawal trial

Journal article

Rationale

Obstructive sleep apnea (OSA) is associated with systemic hypertension. Either overnight intermittent hypoxia, or the recurrent arousals that occur in OSA, could cause the daytime increases in blood pressure (BP).

Objectives

To establish the role of intermittent hypoxia in the increased morning BP in patients with OSA.

Methods

Randomised, double blinded, cross over trial assessing the effects of overnight supplemental oxygen versus air (sham) on morning BP, following continuous positive airway pressure (CPAP) withdrawal in patients with moderate to severe OSA. The primary outcome was the change in home morning BP following CPAP withdrawal for 14 nights, oxygen versus air. Secondary outcomes included oxygen desaturation index (ODI), apnea hypopnea index (AHI), subjective (Epworth sleepiness score) and objective (Oxford sleep resistance test) sleepiness.

Measurements and main results

Supplemental oxygen virtually abolished the BP rise following CPAP withdrawal and, compared to air, significantly reduced the rise in mean systolic BP ( 6.6mmHg; 95% confidence interval or CI 11.3 to 1.9; p=0.008), mean diastolic BP ( 4.6mmHg; 95% CI 7.8 to 1.5; p=0.006), and median ODI ( 23.8/h; interquartile range 31.0, 16.3; p<0.001), following CPAP withdrawal. There was no significant difference, oxygen versus air, in AHI, subjective or objective sleepiness.

Conclusions

Supplemental oxygen virtually abolished the rise in morning BP during CPAP withdrawal. Supplemental oxygen substantially reduced intermittent hypoxia, but had a minimal effect on markers of arousal (including AHI), subjective or objective sleepiness. Therefore intermittent hypoxia, and not recurrent arousals, appears to be the dominant cause of daytime increases in BP in OSA.

Authors: Turnbull, C; Sen, D; Kohler, M; Petousi, N; Stradling, J

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Thoracic Society
• Journal: American Journal of Respiratory and Critical Care Medicine
• Publication date: 2019-01-15
• Acceptance date: 2018-07-06
• DOI: 10.1164/rccm.201802-0240oc
• EISSN: 1535-4970
• ISSN: 1073-449X
• Pmid: 30025470
• Language: English
• Keywords: blood pressure; intermittent hypoxia; sleep apnea, obstructive