Sleep apnea is a condition in which breathing stops for more than ten secondsduring sleep. Sleep apnea is a major, though often unrecognized, cause of daytime sleepiness.
A sleeping person normally breathes continuously and uninterruptedly throughout the night. A person with sleep apnea, however, has frequent episodes (up to 400-500 per night) in which he or she stops breathing. This interruption ofbreathing is called "apnea." Breathing usually stops for about 30 seconds; then the person usually startles awake with a loud snort and begins to breatheagain, gradually falling back to sleep.
There are two forms of sleep apnea. In obstructive sleep apnea (OSA),breathing stops because tissue in the throat closes off the airway. In central sleep apnea, (CSA), the brain centers responsible for breathing failto send messages to the breathing muscles. OSA is much more common than CSA.It is thought that about 1-10% of adults are affected by OSA; only about onetenth of that number have CSA. OSA can affect people of any age and of either sex, but it is most common in middle-aged, somewhat overweight men, especially those who use alcohol.
A combination of the two forms is also possible, and is called "mixed sleep apnea."
Obstructive sleep apnea occurs when part of the airway is closed off (usuallyat the back of the throat) while a person is trying to inhale during sleep.People whose airways are slightly narrower than average are more likely to beaffected by OSA. Obesity, especially obesity in the neck, can increase the risk of developing OSA, because the fat tissue tends to narrow the airway. Insome people, the airway is blocked by enlarged tonsils, an enlarged tongue, jaw deformities, or growths in the neck that compress the airway. Blocked nasal passages may also play a part in some people.
People with OSA almost always snore heavily, because the same narrowing of the airway that causes snoring can also cause OSA. Snoring may actually help cause OSA as well, because the vibration of the throat tissues can cause them to swell. However, most people who snore do not go on to develop OSA.
- OSA and CSA cause similar symptoms. The most common symptoms are:
- Daytime sleepiness
- Morning headaches
- A feeling that sleep is not restful
- Disorientation upon waking.
Sleepiness is caused not only by the frequent interruption of sleep, but by the inability to enter long periods of deep sleep, during which the body performs numerous restorative functions. OSA is one of the leading causes of daytime sleepiness, and is a major risk factor for motor vehicle accidents. Headaches and disorientation are caused by low oxygen levels during sleep, from thelack of regular breathing.
Sleep apnea can also cause serious changes in the cardiovascular system. Daytime hypertension (high blood pressure) is common. An increase in the number of red blood cells (polycythemia) is possible, as is an enlarged left ventricle of the heart (cor pulmonale), and left ventricular failure. In some people,sleep apnea causes life-threatening changes in the rhythm of the heart, including heartbeat slowing (bradycardia), racing (tachycardia), and other typesof "arrhythmias." Sudden death may occur from such arrhythmias. Patients withthe Pickwickian syndrome (named after a Charles Dickens character) are obeseand sleepy, with right heart failure, pulmonary hypertension, and chronic daytime low blood oxygen (hypoxemia) and increased blood CO2 (hypercapnia).
Treatment of obstructive sleep apnea begins with reducing the use of alcoholor tranquilizers in the evening, if these have been contributing to the problem. Weight loss is also effective, but if the weight returns, as it often does, so does the apnea. Changing sleeping position may be effective: Snoring and sleep apnea are both most common when a person sleeps on his back. Turningto sleep on the side may be enough to clear up the symptoms. Raising the headof the bed may also help. Opening of the nasal passages can provide some relief. There are a variety of nasal devices such as clips, tapes, or holders which may help, though discomfort may limit their use. Nasal decongestants maybe useful, but should not be taken for sleep apnea without the consent of thetreating physician.
For moderate to severe sleep apnea, the most successful treatment is nighttime use of a ventilator, called a CPAP machine. CPAP (continuous positive airway pressure) blows air into the airway continuously, preventing its collapse.CPAP requires the use of a nasal mask. The appropriate pressure setting for the CPAP machine is determined by polysomnography in the sleep lab. Its effects are dramatic; daytime sleepiness usually disappears within one to two daysafter treatment begins. CPAP is used to treat both obstructive and central sleep apnea.
CPAP is tolerated well by about two-thirds of patients who try it. Bilevel positive airway pressure (BiPAP), is an alternative form of ventilation. With BiPAP, the ventilator reduces the air pressure when the person exhales. This is more comfortable for some.
Surgery can be used to correct the obstruction in the airways. The most common surgery is called UPPP, for uvulopalatopharngyoplasty. This surgery removestissue from the rear of the mouth and top of the throat. The tissues removedinclude parts of the uvula (the flap of tissue that hangs down at the back of the mouth), the soft palate, and the pharynx. Tonsils and adenoids are usually removed in this operation. This operation significantly improves sleep apnea in slightly more than half of all cases.