Obstructive Sleep Apnea
December 9, 2008 by rainier
Obstructive sleep apnea (OSA): The more common of the two forms of apnea, it is caused by a blockage of the airway, usually when the soft tissue in the back of the throat collapses during sleep.
* On its way to the lungs, air passes through the nose, mouth, and throat (the upper airway).
* Under normal conditions, the back of the throat is soft and tends to collapse inward as a person breathes.
* Dilator (widening) muscles work against this collapse to keep the airway open. Interference or abnormalities in this process cause air turbulence.
* If the tissues at the back of the throat collapse and become momentarily blocked, apnea occurs. Breath is temporarily stopped. In most cases the person is unaware of it, although sometimes they awaken and gasp for breath.
* In some cases, the interference is incomplete (called obstructive hypopnea) and causes continuous but slow and shallow breathing. In response, the throat vibrates and makes the sound of snoring. Snoring can occur whether a person breathes through the mouth or the nose. (Snoring also occurs without sleep apnea.)
* Apnea decreases the amount of oxygen in the blood, and eventually this lack of oxygen triggers the lungs to suck in air.
* At this point, the patient may make a gasping or snorting sound but does not usually fully wake up.
*Typically, the frequency of waking episodes is somewhere between 10 and 60. A person with severe OSA may have more than 100 waking episodes in a single night.
Risk Factors
The primary risk factor for OSA is excessive weight gain. The accumulation of fat on the sides of the upper airway causes it to become narrow and predisposed to closure when the muscles relax. Age is another prominent risk factor. Loss of muscle mass is a common consequence of the aging process. If muscle mass decreases in the airway, it may be replaced with fat, leaving the airway narrow and soft. Men have a greater risk for OSA. Male hormones can cause structural changes in the upper airway.
Obstructive sleep apnea is defined as five or more episodes of apnea or hypopnea per hour of sleep in individuals who have excessive daytime sleepiness. Patients with 15 or more episodes of apnea or hypopnea per hour of sleep are considered to have moderate-to-severe sleep apnea.
