Sleep apnea, although once ignored, is now recognized as a serious potentially fatal medical condition. The primary feature is frequent respiratory pauses (lasting at least 10 seconds). Some patients simply stop trying to breathe and this results in a cessation of air movement that is called "central apnea." Others patients develop collapse of the upper air passages that prevent air movement despite continued breathing efforts. This is called "obstructive apnea." Patients must temporarily arouse or partially awaken to terminate the apnea.
Victims: Although all age groups and sexes are affected, Sleep apnea is more commonly seen in middle-aged overweight men. It is possibly more common in African Americans and Polynesians. It has been estimated that as many as 18 million Americans have sleep apnea. People who are overweight, those with low thyroid function, those with physical abnormalities of the nose, jaw or throat, men receiving testosterone replacement and snorers are at increased of having or developing sleep apnea. Sleep apnea runs in families supporting a likely genetic basis in many cases.
Causes: Central sleep apnea develops when there is instability or failure of an interacting network of nerves (brainstem respiratory motor neurons, brainstem carbon dioxide sensing neurons, carotid body oxygen sensing neurons and the phrenic nerve which connects to the diaphragm) that drives the respiratory system. People with brain disease or severely weakened heart muscle are at increased risk for central sleep apnea. Obstructive sleep apnea develops when there is physical obstruction to airflow through the upper airway (nose and throat). In some people, apnea occurs when the throat muscle and tongue relax and partially block the airway. In others the uvula (fleshy tissue extending from the palate and hanging in the center of the back of the throat) becomes larger and longer than normal and partially block the airway. Because the airway is partially blocked, people tend to breath harder. This creates vibrations that we hear as snoring. Alcohol, sleeping pills and pain pills affect the muscles of the tongue and throat and increase the problem for people with sleep apnea.
Consequences: Sleep apnea impairs your ability to obtain restful sleep; therefore excessive daytime sleepiness is essentially always present. This can often erode normal day-to-day work and social performance. The frequency of work-related and traffic accidents increase. Because of frequent nighttime awakenings and episodes of low blood oxygen, the brain fails to cycle in a restorative manner. Memory impairments may develop and risk for stroke increases. The episodes of low blood oxygen also cause irregular surges of the autonomic nervous system, which governs heart function. Risk for high blood pressure, poor control of diabetes and heart attacks increases. Depression and sexual dysfunction are also common.
Diagnosis: The signs and symptoms of sleep apnea can be subtle; therefore a healthy dose of suspicion is needed. The most obvious symptoms are excessive daytime sleepiness, loud nocturnal snoring and witnessed breathing pauses by bed partners. Other signs and symptoms may include recurrent accidents, increased irritability and forgetfulness, difficult to control hypertension or diabetes or nocturnal angina, sexual dysfunction, unexplained pulmonary hypertension or unusually high red blood cell counts. Polysomnography is a laboratory study which involves measuring brain electrical activity, eye movements, air movement at mouth and nose, chest and abdomen movements, leg movement, muscle tone, heart rate and blood oxygen levels during sleep. This test is critical for diagnosing sleep apnea, assessing its severity and assessing the effectiveness of therapy.
Treatment: There is no one best therapy for obstructive sleep apnea. Therapeutic strategies must be individualized to achieve success. Obese patients with poor sleep hygiene and mild disease may be best managed with behavioral modification, i.e., elimination of alcohol, tobacco or sleeping pills usage, initiation of weight reduction and avoid sleeping on the back.
Patients with moderate to severe disease are best managed with physical techniques to open the airway. Continuous positive airway pressure (CPAP) administered via a small fitted nasal mask is the most common and at present the most effective physical technique. The amount of pressure in the CPAP system is adjusted to keep the airway from collapsing. This restores normal breathing, stable blood oxygen level and normal sleep. Some people have problems tolerating CPAP because of claustrophobia, facial and nasal irritation, headaches, abdominal bloating and mask leaks. Dental appliances, which advance the tongue and lower jaw, can open the airway and may be useful for some patients with mild to moderate disease and are not accepting CPAP. Injury to teeth, soft tissue and jaw joints is possible. Incomplete treatment of the apnea is also possible; therefore follow-up sleep study is needed.
Somnoplasty is a technique, which uses radio waves to decrease the size of tissues in the back of the throat. It is growing in popularity and may be useful for some patients with simple snoring and some with mild sleep apnea. Some patients with obvious airway abnormalities (enlarged adenoids and tonsils, nasal polyps or other upper airway tumors) may benefit for a more formal surgical approach to opening the airway. The success rates of surgery (Uvulopalatopharyngoplasty, mandible advancement, laser assisted uvulopalatoplasty) in the absence of an obvious lesion are mixed (30-60%) and the risk is high compared to non-surgical approaches.
Tracheostomy, a procedure that creates a small hole in the breathing tube below the level of the voice box and below the level of obstruction, is essentially 100% effective in obstructive sleep apnea. It is however highly invasive and should be reserved for patients with life-threatening cardiac consequences of sleep apnea who have failed CPAP. Patients with central sleep apnea without elevated carbon dioxide levels are best treated with oxygen and usual medicines to treat heart failure if present. Patients with central sleep apnea with elevated carbon dioxide levels are best treated with bilevel positive airway pressure (BiPAP). By applying a higher airway pressure during inspiration and a lower pressure during expiration, BiPAP assists the respiratory efforts making each breath more effective and carbon dioxide levels decline.