In obstructive sleep apnea (osa sleep apnea), the upper airway becomes blocked during sleep by the tissue of the soft palate, throat, and/or tongue.
The person with obstructive sleep apnea struggles to breathe against an obstructed airway. His chest moves in and out but, because of the blockage, the air cannot flow into or out of his lungs. Finally, his oxygen concentration drops, as Mr. Kennedy’s did, to the point where his arousal reflex causes him to breathe. He awakens with a loud, gasping, snorting sound.
An obstructive apnea event. The polysomnographic recording shows airflow in and out of the airway and the movements of the breathing muscles. A: Normal breathing while awake. B: The airway collapses and becomes obstructed during sleep. The breathing muscles continue to move, but no air can flow into the airway. C: Emergency arousal awakens the person, and he resumes breathing with a gasp.
People with obstructive apnea may have one or more anatomical abnormalities associated with their upper airway: the passages in their nose and pharynx (throat). Such abnormalities can be seen in head radiograph images of many people with osa sleep apnea.
Possible sources of airway obstructions in people with osa sleep apnea.
In the nose, the abnormal structure may be a deviated nasal septum or chronic swelling of the nasal passages as a result of allergies.
In the upper pharynx, obstructions may include enlarged tonsils or adenoids, an extra-long or fleshy soft palate, or a large uvula (the fleshy tab that dangles in the back of your throat). In the lower pharynx, the problem might be a large tongue, a tongue that is located unusually far back or far down, an unusually small airway opening, a short lower jaw, or a short neck.
Any one of these structural features, or a combination of them, can help cause obstructive sleep apnea.
Body weight is often a factor in the development of obstructive apnea. One-half to three-fourths of patients with obstructive sleep apnea are more than 15 percent over their ideal weight. Obstructive sleep apnea is common in overweight people for several reasons. First, people who are carrying extra weight usually have fatty deposits within the throat tissue, which narrow the upper airway. Second, in some heavy people, the extra weight on the abdomen changes the way their stomach and chest muscles work, alters the operation of their breathing reflexes, and contributes to the development of apnea.
Age is also a factor in osa sleep apnea (obstructive sleep apnea), because the shape and muscle tone of the upper airway tend to change with age. Many people have no sign of obstructive sleep apnea when they are younger but develop it in their 50s or 60s.
Gender is also a factor. Obstructive sleep apnea is approximately three times more prevalent among men. However, after menopause, a woman’s tendency to develop obstructive sleep apnea increases dramatically.
Obstructive sleep apnea is treated by removing whatever is blocking the airway. This can be accomplished by means of a breathing device, or through surgery, and sometimes by both. If obesity is a factor, weight loss usually helps, if it can be maintained (see Chapter 10 for treatment of sleep apnea).
When a physician is seeking the cause of obstructive sleep apnea, it is extremely important to very carefully determine which of these many factors are contributing to the obstruction in order to choose the most effective treatment.
A typical osa sleep apnea (Obstructive Sleep Apnea)
CASE STUDY
Mr. Kennedy crawls into bed and turns out the light. He immediately falls asleep and begins to snore softly. His wife stuffs earplugs into her ears and wills herself to fall asleep quickly, before her husband really starts to snore. She reaches over and shakes his elbow.
“Roll over,” she reminds him.
He complies, turns onto his side, and resumes his snoring.
Over the next few minutes, the sound of each snore becomes louder, more prolonged, more emphatic. Then all at once the room is silent. The snoring has stopped.
Is he still breathing? His ribs are moving in and out as though he is breathing, but no air is going in or out of his lungs. This is because the airway in his throat has collapsed shut while he is relaxed in sleep. His chest heaves in and out now, straining to breathe, even shaking the mattress with the force of the muscle contractions; but his throat is closed, so there still is no actual movement of air in and out. Mr. Kennedy is suffocating.
This is osa sleep apnea (obstructive apnea). Mr. Kennedy may struggle for a breath of air for as long as a minute, or even longer. Meanwhile, the oxygen supply in his body is running out and the carbon dioxide is accumulating.
Fortunately for Mr. Kennedy and the rest of our species, we all have a primitive, fail-safe, emergency arousal response. It awakens us at just such times as this and keeps us from suffocating during sleep. When Mr. Kennedy’s arousal response finally is triggered, he wakes up. His body jerks and he gasps for air with a series of loud, snorting breaths, sucking oxygen into his lungs like a diver returning from the depths. This is the explosive snoring that is typical of osa sleep apnea.
In just a few seconds, fresh air pours into his lungs and the oxygen concentration in his blood reaches nearly normal, the carbon dioxide is expelled, and he returns to sleep. The arousal has been so brief that Mr. Kennedy is not aware of being awakened. He quickly returns to sleep, and the whole process will repeat itself.
Sleep Apnea Can Damage the Heart—And More
We need to pay attention to three important changes that took place in Mr. Kennedy’s body during an apnea event:
1. When his emergency breathing reflex was triggered, his body experienced a surge in epinephrine (adrenalin), the “fight-or-flight” reflex, making his heart beat faster. These surges, repeated throughout the night, may eventually cause high blood pressure, even during daytime. High blood pressure increases the risk of stroke.
2. Each time Mr. Kennedy strained to breathe against the closed airway, sucking his rib cage inward, he made his heart work harder, pumping against that low pressure in order to send blood to his lungs and the rest of his body. This extreme pressure difference can cause enlargement of the heart, lung problems, and irregular heart rhythms. It may increase the chances that the heart will beat slower and slower and finally … stop … during sleep.
3. Finally, awakening to breathe again and again broke up the normal pattern of Mr. Kennedy’s sleep. People with severe sleep apnea may never reach deep sleep; they have very fragmented REM sleep because of the constant arousals. Thus, throughout the night it is the deepest sleep that is most disturbed. Disturbed sleep leads to daytime drowsiness, sometimes so severe that it literally ruins a person’s life. Automobile crashes are a common side effect of untreated sleep apnea.