Normal hypercapnic cerebrovascular conductance in obstructive sleep apnea

Area of Science:

• Neurology
• Sleep Medicine
• Cardiovascular Science

Background:

• Obstructive sleep apnoea (OSA) and impaired cerebrovascular reactivity (CVR) are recognized risk factors for stroke.
• Altered endothelial function in OSA may contribute to impaired CVR, potentially linking OSA to stroke pathogenesis.

Purpose of the Study:

• To investigate whether CVR is decreased in patients with OSA.
• To determine if impaired CVR in OSA patients is a mechanism contributing to stroke risk.

Main Methods:

• Cerebrovascular reactivity (CVR) was assessed by measuring middle cerebral artery blood flow velocity (MCAv) and mean arterial blood pressure (MAP) responses to hypercapnia.
• Overnight changes in CVR were evaluated in treatment-naïve, healthy OSA (n=13) and non-OSA (n=9) subjects under two isoxic conditions (150 and 50 mmHg).

Main Results:

• No significant overnight changes in CVR were observed in either the OSA or non-OSA groups.
• There were no significant differences in CVR between OSA and non-OSA subjects at either isoxic tension.
• CVR was found to increase in hypoxic conditions.

Conclusions:

• The study did not find evidence supporting a decrease in CVR in otherwise healthy OSA patients compared to non-OSA controls.
• The findings suggest that impaired CVR may not be the primary mechanism linking OSA to increased stroke risk in this population.