Sleep apnoea raises carbon dioxide level

People suffering from seep apnoea may develop high levels of carbon dioxide in the blood during the daytime — a condition known as hypercapnia. Sleep apnoea is a disorder of disrupted breathing during sleep. The throat muscles relax during deep sleep. In people with sleep apnoea, the muscles relax so much that they cause obstruction to the windpipe making breathing difficult. In some cases, the breathing may actually stop for some time. The symptoms of sleep apnoea include heavy snoring, drowsiness during the day due to disturbed sleep, headaches on waking up, decrease in muscle coordination, and mood changes and depression, in the long run. Researchers from the Chiba University studied 1,227 patients with obstructive sleep apnoea. Tests showed that 168 patients, i.e. 14 per cent, suffered from daytime hypercapnia. These patients weighed significantly more and had worse sleep apnoea than patients with normal blood levels of carbon dioxide. The researchers also studied the effect of a standard treatment for sleep apnoea called continuous positive airway pressure (CPAP) therapy in 37 hypercapnic patients who had severe sleep apnoea. With CPAP, a special facemask is worn that continuously blows air into the throat, preventing the tissues from collapsing. At three months, CPAP had corrected daytime hypercapnia in 19 (51 per cent) of these patients. The finding that about half the patients of sleep apnoea and high blood carbon dioxide levels respond to CPAP therapy suggests that the two conditions are related; daytime hypercapnia in sleep apnoea syndrome may be an end product of a complex conglomerate.