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Could supplemental oxygen help sleep apnoea patients?

Supplemental oxygen eliminates morning blood pressure rise in patients who stop using CPAP

Louise Prime

Monday, 23 July 2018

Supplemental oxygen almost eliminates the morning blood pressure rise in patients with moderate to severe sleep apnoea who stop using continuous positive airway pressure (CPAP), UK research has shown. However, authors of the study*, published online first in the American Journal of Respiratory and Critical Care Medicine, warned that further research is needed to examine the safety of supplemental oxygen before it can be considered as an alternative to CPAP, which people often find difficult to tolerate.

Researchers led from the University of Oxford explained that obstructive sleep apnoea (OSA) is well known to be associated with systemic hypertension and cardiovascular disease; and that some studies have linked the acute blood pressure (BP) rise that OSA sufferers experience while sleeping, to having to wake frequently when their breathing stops. They wanted to find out whether these recurrent arousals were also responsible for higher daytime BP in OSA patients; or whether this is caused by intermittent hypoxia resulting from interrupted breathing during sleep.

To establish the role of intermittent hypoxia in the increased morning BP in patients with OSA, they conducted a randomised, double-blinded, cross-over trial to assess the effects of overnight supplemental oxygen on morning BP, following withdrawal of CPAP in patients with moderate to severe OSA.

They recruited 25 adults, all of who had been using CPAP for at least a year, and withdrew CPAP for 14 nights. Participants received either supplemental oxygen (intervention) or normal air (control), via a face mask or nasal cannula, for the first CPAP withdrawal period; then they crossed over to the opposite treatment for the second period. Neither patients nor researchers knew which patients were having oxygen or air.

The researchers then compared the primary outcome – the change in home morning BP following CPAP withdrawal for 14 nights – and several secondary outcomes between the intervention and control treatments. They reported that supplemental oxygen almost eliminated the BP rise following CPAP withdrawal; and, compared with air, it also significantly reduced the rise in mean systolic BP ( 6.6mmHg), mean diastolic BP ( 4.6mmHg), and median oxygen desaturation index ( 23.8/h), following CPAP withdrawal. They found no significant difference, oxygen versus air, in apnoea hypopnoea index (AHI), or in subjective or objective sleepiness. Nor was there any difference between the groups in objective or subjective measures of daytime sleepiness.

They concluded: “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.”

However, they noted that because previous research has shown that supplemental oxygen could increase injury to the heart when administered after a heart attack – and that in some patients, supplemental oxygen causes hypercapnia – more research must be done to prove it is safe before it can be used as an alternative to CPAP.

They said: “The next challenge for researchers will be to see if supplemental oxygen treatment has similar effects in patients in the longer-term along with assessing its longer-term safety.”

*Turnbull CD, Dushendree Sen, Kohler M, et al. Effect of supplemental oxygen on blood pressure in obstructive sleep apnea (SOX): a randomised, CPAP withdrawal trial. American Journal of Respiratory and Critical Care Medicine 2018; doi: 10.1164/rccm.201802-0240OC.

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