NORTHBROOK, Ill -- November 12, 2008 -- Carbon monoxide (CO) levels in a patient's blood may determine the severity of a patient's obstructive sleep apnea (OSA), according to a study published in the November issue of CHEST.
Masayoshi Kobayashi, MD, Department of Internal Medicine and Clinical Immunology, Yokohama City University Graduate School of Medicine, Yokohama, Japan, and colleagues determined the CO levels in 35 patients with OSA and 17 healthy controls matched for age, both before and after polysomnography.
Although there was no difference in CO levels between the 2 groups prior to sleep, the post-sleep circulating CO levels were significantly higher in patients with OSA compared with control subjects.
Furthermore, the change in CO level, which was defined as a gap between the pre-sleep and post-sleep CO levels, correlated with the apnea-hypopnea index and hypoxia duration as a percentage of total sleep time. This showed that the higher the CO level, the more severe the OSA.
Treatment with continuous positive airway pressure (CPAP) resulted in normalisation of the post-sleep CO level. Researchers speculate that because patients with OSA have an increased risk for cardiovascular morbidity and CO levels are a marker for cardiovascular risk, using CPAP to reduce CO levels could, ultimately, reduce a patient's risk for cardiovascular morbidity.
SOURCE: American College of Chest Physicians
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