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Obstructive sleep apnea - Introduction

Description

An in-depth report on the causes, diagnosis, treatment, and prevention of obstructive sleep apnea.

Introduction:

Obstructive sleep apnea (OSA) is a disorder in which a person stops breathing during the night, perhaps hundreds of times. These gaps in breathing are called apneas. The word apnea means absence of breath. An obstructive apnea episode is defined as the absence of airflow for at least 10 seconds.

Sleep apnea is usually accompanied by snoring, disturbed sleep, and daytime sleepiness. People might not even know they have the condition.

Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) occurs when tissues in the upper throat collapse at different times during sleep, thereby blocking the passage of air. In general, OSA occurs as follows:

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 often 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.

Obstructive sleep apnea is defined as five or more episodes of apnea or hypopnea per hour of sleep (called apnea-hypopnea index or AHI) 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- sleep apnea.

Other Causes of Apnea

Central sleep apnea is much less common. It is caused by some problem in the central nervous system, most likely a failure of the brain to signal the airway muscles to breathe. In such cases, oxygen levels drop abruptly and usually the sleeper wakes with a start. Often people with central sleep apnea recall waking up. They generally experience less sleepiness during the day than people with obstructive sleep apnea. Heart disease, and in particular heart failure, is the most common cause of central sleep apnea.
Mixed apnea is the term used when central and obstructive sleep apneas occur together.
Upper airway resistance syndrome (UARS) is a condition in which patients snore, wake frequently during the night, and have excessive daytime sleepiness. However, UARS patients do not have the breathing abnormalities that characterize sleep apnea and they do not show a reduction in blood oxygen levels. Unlike apnea, UARS is more likely to occur in women than in men. Treatments are similar to those of sleep apnea. It is not known if UARS has any serious health complications.

Resources

www.sleepapnea.org -- American Sleep Apnea Association
www.aasmnet.org -- American Academy of Sleep Medicine
www.sleepfoundation.org -- National Sleep Foundation
www.nhlbi.nih.gov/sleep -- National Center on Sleep Disorders Research
www.sleepeducation.com -- Sleep Education from the American Academy of Sleep Medicine

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Reviewed last on: 6/23/2009
Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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