Posted on April 01, 2013 13:05
Obstructive sleep apnea (OSA) or obstructive sleep apnea syndrome is the most common type of sleep apnea and is caused by obstruction of the upper airway. It is characterized by repetitive pauses in breathing during sleep, despite the effort to breathe, and is usually associated with a reduction in blood oxygen saturation. These pauses in breathing, called "apneas" (literally, "without breath"), typically last 20 to 40 seconds.
The individual with OSA is rarely aware of having difficulty breathing, even upon awakening. It is recognized as a problem by others witnessing the individual during episodes or is suspected because of its effects on the body (sequelae). OSA is commonly accompanied with snoring.
Symptoms may be present for years or even decades without identification, during which time the sufferer may become conditioned to the daytime sleepiness and fatigue associated with significant levels of sleep disturbance. Sufferers who generally sleep alone are often unaware of the condition, without a regular bed-partner to notice and make them aware of their symptoms.
As the muscle tone of the body ordinarily relaxes during sleep, and the airway at the throat is composed of walls of soft tissue, which can collapse, it is not surprising that breathing can be obstructed during sleep. Although a very minor degree of OSA is considered to be within the bounds of normal sleep, and many individuals experience episodes of OSA at some point in life, a small percentage of people are afflicted with chronic, severe OSA.
Many people experience episodes of OSA for only a short period of time. This can be the result of an upper respiratory infection that causes nasal congestion, along with swelling of the throat, or tonsillitis that temporarily produces very enlarged tonsils. The Epstein-Barr virus, for example, is known to be able to dramatically increase the size of lymphoid tissue during acute infection, and OSA is fairly common in acute cases of severe infectious mononucleosis. Temporary spells of OSA syndrome may also occur in individuals who are under the influence of a drug (such as alcohol) that may relax their body tone excessively and interfere with normal arousal from sleep mechanisms
Common signs of OSA include unexplained daytime sleepiness, restless sleep, and loud snoring (with periods of silence followed by gasps). Less common symptoms are morning headaches; insomnia; trouble concentrating; mood changes such as irritability, anxiety and depression; forgetfulness; increased heart rate and/or blood pressure; decreased sex drive; unexplained weight gain; increased urination and/or nocturia; frequent heartburn or gastroesophageal reflux disease; and heavy night sweats.
There are a variety of treatments for OSA; use is determined by an individual patient's medical history, the severity of the disorder and, most importantly, the specific cause of the obstruction.
In acute infectious mononucleosis, for example, although the airway may be severely obstructed in the first 2 weeks of the illness, the presence of lymphoid tissue (suddenly enlarged tonsils and adenoids) blocking the throat is usually only temporary. A course of anti-inflammatory steroids such as prednisone (or another kind of glucocorticoid drug) is often given to reduce this lymphoid tissue. Although the effects of the steroids are short term, in most affected individuals, the tonsillar and adenoidal enlargement are also short term, and will be reduced on its own by the time a brief course of steroids is completed. In unusual cases where the enlarged lymphoid tissue persists after resolution of the acute stage of the Epstein-Barr infection, or in which medical treatment with anti-inflammatory steroids does not adequately relieve breathing, tonsillectomy and adenoidectomy may be urgently required.
OSA in children is sometimes due to chronically enlarged tonsils and adenoids. Tonsillectomy and adenoidectomy is curative. The operation may be far from trivial, especially in the worst apnea cases, in which growth is retarded and abnormalities of the right heart may have developed. Even in these extreme cases, the surgery tends to cure not only the apnea and upper airway obstruction, but allows normal subsequent growth and development. Once the high end-expiratory pressures are relieved, the cardiovascular complications reverse themselves. The postoperative period in these children requires special precautions.
The treatment of OSA in adults with poor oropharyngeal airways secondary to heavy upper body type is varied. Unfortunately, in this most common type of OSA, unlike some of the cases discussed above, reliable cures are not the rule.
Some treatments involve lifestyle changes, such as avoiding alcohol and medications that relax the central nervous system (for example, sedatives and muscle relaxants), losing weight, and quitting smoking. Some people are helped by special pillows or devices that keep them from sleeping on their backs, or oral appliances to keep the airway open during sleep. For those cases where these conservative methods are inadequate, doctors can recommend continuous positive airway pressure (CPAP), in which a face mask is attached to a tube and a machine that blows pressurized air into the mask and through the airway to keep it open. There are also surgical procedures intended to remove and tighten tissue and widen the airway, but none has been reproducibly successful. Some individuals may need a combination of therapies to successfully treat their condition. Home polysomnogram equipment can assist patients in reviewing treatment effectiveness. Though some equipment is marketed as sleep hygiene devices not intended for medical use, the equipment can prove invaluable under medical supervision to evaluate overall treatment effectiveness in conjunction with physician administered sleep studies.
Old age is often accompanied by muscular and neurological loss of muscle tone of the upper airway. Decreased muscle tone is also temporarily caused by chemical depressants; alcoholic drinks and sedative medications being the most common. Permanent premature muscular tonal loss in the upper airway may be precipitated by traumatic brain injury, neuromuscular disorders, or poor adherence to chemical and or speech-therapy treatments.
Individuals with decreased muscle tone, increased soft tissue around the airway, and structural features that give rise to a narrowed airway are at high risk for OSA. Men, in which the anatomy is typified by increased mass in the torso and neck, are at increased risk of developing sleep apnea, especially through middle age and later. Women suffer typically less frequently and to a lesser degree than do men, owing partially to physiology, but possibly also to differential levels of progesterone. Prevalence in post-menopausal women approaches that of men in the same age range. Women are at greater risk for developing OSA during pregnancy.
OSA also appears to have a genetic component; those with a family history of it are more likely to develop it themselves. Lifestyle factors such as smoking may also increase the chances of developing OSA as the chemical irritants in smoke tend to inflame the soft tissue of the upper airway and promote fluid retention, both of which can result in narrowing of the upper airway. An individual may also experience or exacerbate OSA with the consumption of alcohol, sedatives, or any other medication that increases sleepiness as most of these drugs are also muscle relaxants.