Role of cerebral blood flow in the pathophysiology of central and obstructive sleep apnea

Sleep apnea occurs when a person repeatedly stops breathing for a short period of time while they sleep. This common disorder affects about 20 per cent of Canadians. During sleep apnea episodes, blood oxygen levels fall, resulting in persistent low levels of oxygen, called hypoxia. Consequently, people with sleep apnea commonly experience adverse health outcomes, including high blood pressure, heart attacks and strokes. Preliminary findings from Dr. Philip Ainslie’s research lab have shown that reductions in brain blood flow can worsen sleep apnea, while increases in brain blood flow may reduce it. Dr. Shawnda Morrison's research will expand on these exciting initial findings by exploring the possibility of treating sleep apnea by manipulating brain blood flow. Dr. Morrison will use sophisticated imaging techniques to examine the effect of an oral medication, which alters brain blood flow, in patients at rest and while they sleep. Her first study will examine patients with and without sleep apnea in a controlled laboratory setting. In her second study, Dr. Morrison will induce sleep apnea in otherwise healthy humans at high altitude (5,000 metres, near the base camp of Mt. Everest, Nepal). In this study, she will also conduct the same experiments on a group of high-altitude residents who do not develop sleep apnea, and compare any differences observed between the two groups. The results of these studies will have major implications for understanding what influences brain blood flow and how these different factors can then affect sleep apnea. Those people who do not develop sleep apnea will provide insight into future sleep apnea treatments. Indeed, these studies will provide a “proof of concept” that an oral medication, which alters brain blood flow, can be an effective treatment for sleep apnea. This will, in turn, dramatically reduce the incidence of heart disease and stroke in patients who have sleep apnea.