What is obstructive sleep apnea?
What does “obstructive sleep apnea” mean? Apnea is the absence of breathing. The commoner type of sleep apnea involves a block in the back of the throat (the airway), so it is referred to as “obstructive”.
Who gets obstructive sleep apnea? Individuals who are prone to develop OSA have either a small or crowded airway from the normal anatomic structures (tongue, uvula, tonsils, soft palate) ganging together.
What is actually happening in the throat? During wakefulness, the throat widening muscles keep the upper airway open. With the onset of sleep, these muscles relax, allowing collapse of the airway in those persons who are susceptible to OSA. The airway collapses in the velopharynx, which is behind the uvula and soft palate, or the hypopharynx, behind the tongue.
How does the body respond then? OSA causes reduced or absent airflow into the lung. The air that is available in the tiny lung sacs (alveoli) becomes stale, which results in too little oxygen in the blood and too much carbon dioxide. These blood gas changes stimulate the patient to breathe harder. The effort against the collapsed airway arouses the sufferer into a lighter stage of sleep or to waken so as to reestablish an open airway.
With the arousal, the sufferer will hyperventilate to increase oxygen and decrease carbon dioxide levels. As the blood gases returns to normal, the OSA sufferer will fall back to a deeper stage of sleep and the cycle will begin again. This pattern can be repeated numerous times each hour during the night leading to many symptoms:
What symptoms? One or more of these may be experienced by those with OSA:
Daytime fatigue is common because repeated arousals during the night causes many wakenings, some lasting seconds and others up to hours. This sleep fragmentation also prevents deeper, more satisfying sleep. The result is fatigue.
Memory and concentration difficulty may result from poor sleep quality.
Urinary frequency at night may result because people who have OSA stimulate the heart wall and brain to release a hormone similar to a water pill with each apnea event.
Sweating mildly or profusely comes from the sympathetic nervous system being aroused by the anxiety of the struggles to breathe. More frequent apnea causes greater sweating.
Morning headache can occur from the carbon dioxide being too high and the oxygen too low in the blood after prolonged apneas. The changes in the blood gases cause the arteries of the brain to spasm, leading to headache.
Bizarre or repeated dreams, sometimes with a metaphor for asphyxiation, can occur.
What is the sleeping partner going through?
Sounds of snoring, gasping, choking, snorting, or clicking may be heard by the partner.
Movements such as kicking, arms thrashing, and rarely jumping up from the bed to get air may be felt.
Anxiety may occur in the partner, who can observe prolonged apneas throughout the night and thus worry for the wellbeing of the apneic person.
Treatments for OSA
Since the problem is anatomic, the best solutions for OSA involve correcting the anatomic problem(s) temporarily or permanently. One or more of the following treatment options may be appropriate in those wishing to address it.
Total Body options
Weight reduction is an effective therapy for many persons with OSA, particularly for obese persons. The amount of weight reduction required is, however, often so prohibitively high as to put it out of reach for most dieting persons. Even those who undergo bariatric surgery often find that some form of apnea therapy is still needed until well over 100 pounds is lost.
Occasionally, the OSA is positional and can be entirely eliminated by avoidance of sleeping on the back. Testing may be needed to confirm the success of positional therapy.
Air pressure therapy (CPAP)
Ordinarily, breathing air involves sucking the air in by creating negative pressure in the chest that pulls the air in but also the tissues in the airway together. Continuous positive airway pressure (CPAP) is the therapy most commonly used to treat OSA. With CPAP, a blower generates air under positive pressure and delivers it by a tube to a nasal mask or cannula. CPAP will pneumatically splint the upper airway open throughout the breathing cycle. The tissues that would be causing apnea are pushed aside. CPAP has been the standard therapy for OSA since 1985. Bilevel PAP, a variant of CPAP, involves use of a higher air pressure during inspiration and a lower pressure delivered with exhalation.
The mandible is the bone of the chin to which the tongue is attached inside the mouth. By drawing the mandible forward during sleep, a “mandibular advancing appliance (MAA)” can alleviate snoring and milder apnea provided the reason for airway closure is much related to the tongue. The tongue is one of the causative factors in OSA when it is either too large or set back in the pharynx, either an inherited, developmental or hormonal trait.
Surgery for OSA
There are at least a few approaches for eliminating or modifying the throat anatomy.
Tissues in the pharynx such as the tonsillar pillars, tonsils, and adenoids may be blocking the airway. The soft palate and uvula combined may be long, redundant, swollen or simply placed close to the back pharyngeal wall, allowing for little room when the head is placed on the pillow. An ear/nose/throat surgeon can remove some or all these tissues in a major surgery that results in much pain in the airway for at least 10-15 days, but if the tissue is the only reason for airway blockage, apnea may be much less frequent after healing. The tongue may still be positioned in the back of the throat during sleep, so another surgical procedure can be done to effectively alter its position during sleep.
Sometimes, snoring can be alleviated by a surgery that involves the nostrils, nasal septum, or the uvula alone but to treat apnea with surgery, it is generally necessary to remove offending tissue in the throat.
Treatment goals for persons with OSA are
• To maintain an open airway to prevent apneas and hypopneas
• To improve the quality of sleep by eliminating arousals and wakenings
• To alleviate excessive daytime sleepiness due to poor sleep quality
• To reduce sympathetic activation causing nighttime anxiety and restlessness
• To forestall cardiovascular morbidity & mortality associated with OSA
• To eliminate noises associated with airway closure (i.e., snoring, choking, etc.)