Sleep Apnoea

During sleep the muscles that hold the throat open relax. In some people the airway then narrows so far that airflow drops or stops altogether, despite continued effort to breathe. Oxygen falls, carbon dioxide rises, and the brain briefly wakes just enough to restore muscle tone and reopen the airway. Breathing resumes and sleep continues, and none of it is remembered.

This can happen dozens of times an hour. The number of events per hour is what defines the severity and is the figure a sleep study produces. Each arousal fragments sleep, so the night is long but almost none of it is restorative, and each drop in oxygen provokes a surge in blood pressure and heart rate.

Body weight, particularly around the neck, is the strongest risk factor in adults, along with a receding jaw, a crowded throat and a blocked nose. In children the picture is usually different: the airway is obstructed by enlarged tissue at the back of the nose and throat, and a tired child often presents as an overactive or inattentive one instead of a sleepy one.

A sleep study is required to make the diagnosis, and no combination of examination and questionnaires can substitute for it. A home study records airflow, effort, oxygen saturation and pulse; a laboratory study adds brain wave recording and is used where the picture is complicated or the home result does not fit.

The result gives an index of events per hour and how far oxygen falls, and those two numbers set the severity and drive everything that follows. Questionnaires such as the Epworth scale are used alongside to record how much daytime function is affected.

Examination maps where the airway is narrow: the nose by endoscopy, the throat for tonsil size and how much is visible past the tongue, and the jaw position. Blood pressure, weight, neck circumference and a check for diabetes and thyroid disease are part of the workup because they travel with it. Where surgery is being considered, sleep endoscopy shows which level actually collapses under sedation.

CPAP works from the first night it is tolerated, and tolerating it is the whole issue. The first two weeks are the hardest, and most problems are solved by changing the mask instead of abandoning the machine. Humidification helps a dry nose and mouth, and the machine records how many hours it is used, which is reviewed honestly at follow-up.

Weight loss changes the disease itself and not just the way it is managed, and a ten per cent reduction produces a measurable fall in the event rate. Alcohol and sedatives in the evening make every version worse.

After airway surgery, the throat is genuinely painful for about two weeks in an adult and swallowing is the difficulty. A repeat sleep study at three to six months is standard, since the point is the numbers and not how the person feels, and people frequently report improvement that the study does not confirm.