About Obstructive Sleep Apnea

Introduction

Sleep apnea is the most common form of sleep-disordered breathing (SDB), a general term for any sleep disorder with apneas and hypopneas.

• Apnea: when you stop breathing for ten seconds or longer
• Hypopnea: abnormally shallow breathing lasting at least 10 seconds

Both apneas and hypopneas cause sleep arousals—moments when you wake up enough to start breathing again but not enough to remember waking. Some sleep arousals simply cause you to shift into a lighter stage of sleep. In either case, the sleep arousal hurts the quality of your sleep and puts stress on your cardiovascular system.

Apneas and hypopneas have two causes:

• upper airway obstruction, either full or partial
• a problem with the body's automatic drive to breathe.

Apneas and hypopneas can cause a number of physical changes:

• blood oxygen level drops
• heart rate drops during each apnea and increases after each arousal
• blood pressure increases after each arousal
• additional biological-chemical changes.

Sleep Apnea Syndrome (SAS)

There are three types of sleep apnea: obstructive, central, and mixed.

• Obstructive sleep apnea (OSA) is the most common type of sleep apnea. It occurs when your upper airway closes but your efforts to breathe continue. The primary causes of upper airway obstruction are lack of muscle tone during sleep, excess tissue in the upper airway, and physical abnormalities in the upper airway and jaw.
• Central sleep apnea (CSA) affects only 5-10% of people with sleep apnea. It occurs when your breathing stops but your airway is open. This type of apnea results from the body's failure to breathe automatically. It's as if a short circuit prevented the brain from keeping the lungs going.
• Mixed sleep apnea is a combination of both OSA and CSA.

All three types of sleep apnea have the same basic health consequences: increased risk of hypertension (high blood pressure), excessive daytime sleepiness, poor concentration, poor memory, sexual dysfunction, and depression. The biggest noticeable difference is that people with CSA tend not to snore. While people with OSA use continuous positive airway pressure (CPAP) therapy, some people with CSA use bilevel positive airway pressure therapry.

Obstructive Sleep Apnea (OSA)

Obstructive sleep apnea (OSA) is a common disorder. Estimates for the number of Americans with OSA vary depending on the criteria researchers use for the study. Conservative estimates, however, put the number of adult Americans with OSA at approximately 20 million. OSA occurs because of upper airway obstructions that can cause a person to snore or to stop breathing. While snoring is a common symptom of OSA, many people with OSA don't snore at all, and some people who snore don't have OSA.

Upper airway obstructions occur during sleep for two primary reasons: lack of muscle tone and gravity. Excess tissue in the upper airway and physical abnormalities increase the problem. During sleep, especially in rapid eye movement (REM) sleep, our bodies relax, and muscle tissues like the tongue and soft palate lose their slight rigidity. Because we tend to sleep lying down, gravity pulls these tissues toward the back of the throat and closes the upper airway.

Normal breathing	Obstructive apnea

Snoring—the symptom most commonly associated with OSA—happens when the upper airway becomes partially obstructed. As air moves through the limited space, it causes the soft tissues of the throat, uvula, and soft palate to vibrate. These vibrations create the sound we recognize as snoring. Instead of a steady stream of air, a snorer gets small "puffs" of air. These puffs don't provide as much fresh oxygen as a good, strong breath.

Snoring

When these tissues obstruct the upper airway completely, they prevent breathing. They actually work to suffocate the sleeper. The sleeper wakes up enough to regain control of the upper airway, breathe again, and then fall back to sleep. This happens from dozens to hundreds of times per night for people with OSA, but they usually don't remember waking up.

Each obstruction deprives the body of oxygen and forces it to retain carbon dioxide that it would normally exhale. As a result, the body's blood gases get out of balance, creating a "toxic" environment. When the body sets off "alarms" that it needs more oxygen, the brain wakes the sleeper, breathing resumes, and the individual falls back to sleep until the next obstruction occurs. These obstructions increase heart rate, raise blood pressure, and eventually weaken the body's automatic response system, resulting in increasingly more severe apneas and hypopneas.

The brief wake-ups that people with OSA experience also diminish their quality of sleep, resulting in sleep deprivation. The symptoms of sleep deprivation may be what bring most people with OSA to see their physicians. Symptoms like excessive daytime sleepiness, poor concentration, poor memory, and even depression are common for people with OSA.

Symptoms

Hypertension and a decreased blood oxygen level are common symptoms for people with sleep apnea, but these are not easily detected. Here are the symptoms that are easiest to identify without diagnostic testing. People with sleep apnea will probably not have all these symptoms.

• Excessive sleepiness (use the Epworth Sleepiness Scale to evaluate your sleepiness)
• Snoring (people with obstructive sleep apnea [OSA] usually snore but not always)
• Witnessed apneas or irregular breathing during sleep (gasping, long pauses, etc—a spouse or partner may notice these)
• Poor concentration
• Forgetfullness
• Morning headaches
• Sexual dysfunction
• Depression
• Nocturia (frequent urination during the night)
• Night sweats

Risk Factors

Doctors have identified a number of factors that may increase a person's risk of having obstructive sleep apnea (OSA):

• obesity
• snoring
• family history of OSA or snoring
• small upper airway (large tongue, large uvula, recessed chin, excess tissue in the throat and/or soft palate)
• gender (men are at higher risk; after menopause, women are at same risk level).

A number of serious diseases have been linked to OSA:

• hypertension (high blood pressure)
• congestive heart failure (CHF)
• stroke
• diabetes.

Heavier people have a greater risk of sleep apnea. In addition, the heavier a person becomes the more severe OSA becomes, so most physicians recommend exercise and a healthy diet for people with OSA.

Researchers have discovered people who don't get enough rapid eye movement (REM) sleep have increased appetites and decreased energy levels. Consequently, researchers believe that OSA might start a downward spiral for some people because as they lose sleep, they eat more, gain weight, and make their OSA worse.

Copyright © ResMed 2005, Used with Permission