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OBSTRUCTIVE SLEEP APNEA SYNDROME
WHAT IS IT?
Sleep apnea is a very common problem. It is a breathing problem that occurs during sleep. Several types of apnea problems have been recognized, but by far the most common is Obstructive Sleep Apnea. It accounts for over ninety-five percent of the individuals who have problems with sleep apnea.
What is apnea? What is obstructive apnea? What does it do? Anyone who has been diagnosed with sleep apnea or has a loved one with sleep apnea should know the answers to these questions. Apnea occurs when breathing stops. Obstructive apnea happens when breathing stops because of obstruction of the airway.
The medical problem - Obstructive Sleep Apnea - is a syndrome. A syndrome is a grouping of signs, symptoms and findings, which when placed together, are considered to be a medical condition. Syndromes are usually diagnosed by a person’s symptoms, physical findings and laboratory abnormalities. The Obstructive Sleep Apnea Syndrome is a combination of varying degrees of sleep symptoms, sleep test abnormalities and to a lesser degree, abnormalities in the physical examination. Apnea events interrupt sleep and symptoms result, but apnea is much more than symptoms. There are long-term consequences.
Apnea means “no breath.” When people have sleep apnea problems they are suffering from interruptions in their breathing while asleep. With the obstructive sleep apnea syndrome, the interruptions in breathing occur when the airway becomes blocked during sleep. The chest and diaphragm are making efforts to pull air into the lungs, but the passageway to the lungs is blocked. Figure One shows a five-minute tracing of a normal sleep test. It shows a snoring microphone recording (no snoring is seen on this record), electrocardiogram, flow of air through the nose and mouth, chest and abdominal wall movements, and the level of oxygen saturation.
FIGURE ONE – NORMAL BREATHING DURING SLEEP
FIGURE TWO – SLEEP APNEA DURING SLEEP
Figure Two shows five minutes of severe sleep apnea. Note the loud snoring, the absence of airflow (shaded areas on the flow channel), changes in respiratory effort in the chest and abdomen, and the changing oxygen levels.
Breathing is an act that we do not have to think about. It occurs regularly, without conscious thought and is regulated by physiologic factors. We breathe when we do because of the controls built into our body’s respiratory system. The levels of oxygen and carbon dioxide in our blood, the sensations of our muscles in the chest and diaphragm and the amount of acid in the blood, are all factors that determine the depth and frequency of our breaths. During sleep, our breathing is under the same controlling factors. When obstruction to the airway occurs, the sensors that control our breathing note that change and then cause an increase in the physical effort to breathe. As a result of the effort, air begins to move again.
These obstructive events occur over and over again. As seen in Figure Two in someone with the obstructive sleep apnea syndrome, they occur many times per hour. The events can result in total blockage of the airway (apnea), partial obstruction of the airway (hypopnea), or a lesser degree of obstruction (airflow reductions with arousal). These events have varying effects on the person who has them.
The majority of complaints from patients with obstructive sleep apnea syndrome focus on the quality of sleep. The person frequently does not sleep well, often has non-refreshing sleep and complains of daytime sleepiness. Almost any symptom related to the quality of sleep or the ability to sleep may be reported. Frequently reported symptoms are listed in Table One.
FREQUENT PATIENT COMMENTS
“I can drink a cup of coffee at bedtime and go to sleep.”
“If I am not busy, I’ll nod off.”
“I’m fine as long as I’m active.”
“I can sleep 12 hours and still need a nap.”
“I can sleep anywhere, at any time.”
“When I snore, the roof shakes.”
“When I snore, they hear me at the other end of the house.”
WHAT CAUSES OBSTRUCTIVE SLEEP APNEA?
The obstruction of the airway that causes the syndrome is reversible. In fact, it comes and goes. It occurs only during sleep, usually in individuals who have little awareness of the events. While awake these individuals breathe without problems. While the reason obstruction occurs remains under research, physicians now know a great deal about the site of the obstruction and individuals who develop obstructive sleep apnea.
The site of the obstruction occurs in the upper airway. That is the area above the larynx (voice box). The larynx and the airway below are held open by rings of cartilage and do not collapse. However, above the larynx the reversible obstruction occurs at the base of the tongue or at the soft palate. People with obstructive sleep apnea are essentially choking in their sleep.
Figure Three shows the normal anatomy of the upper airway. The obstruction in sleep apnea occurs above the larynx.
FIGURE THREE – NORMAL ANATOMY OF THE UPPER AIRWAY
Physicians have a good idea of the mechanism that results in the obstruction. The vast majority of individuals have no abnormalities of their airways. Their throats show normal tissue in normal places. For a great deal of time it was thought that a specific reason for the apneas would be discovered. However, that has not been the case. A few individuals have significant and obvious problems in their airways: enlarged tonsils, enlarged adenoids, growths or birth defects in their jaw area. These abnormalities result in a small upper airway that obstructs easily upon reclining. Uncommonly, severe hypothyroid problems result in obstructive sleep apnea.
The reversible obstructions occur mostly in normal throats. Over the past thirty years doctors have investigated why the obstructions occur and how they occur. It is clear that a large number of overweight people have obstructive sleep apnea. It has been found that when morbidly obese individuals with sleep apnea lose weight, the obstructive sleep apnea will go away about fifty-percent of the time.
Thin people have obstructive sleep apnea, too. Men, women and children have obstructive sleep apnea. They may be tall, short, thin or stocky. Studies have shown that five to fifteen percent of the American population has some degree of obstructive sleep apnea. After studying thinner individuals and obese patients who still have obstructive sleep apnea after weight loss, medical specialists are beginning to come to the conclusion that there are two major factors that result in the obstructions. The two factors are: 1) the degree of muscle relaxation that occurs in the upper airway muscles during sleep and 2) the size and shape of the throat.
Figure Four demonstrates the site of obstruction for the majority of patients with the obstructive sleep apnea syndrome. The arrow shows the area where the palate and tongue obstruct the airway during sleep.
FIGURE FOUR – OBSTRUCTION OF THE AIRWAY IN SLEEP APNEA
WHAT DOES OBSTRUCTIVE SLEEP APNEA DO?
The obstructive events have two major effects. First, the events cause a disruption in the sleeping patterns of the brain and second, the events place a stress on the cardiovascular system. When the obstructions occur, the brain senses that the breathing is not effective and breathing efforts are increased. The effort needed to open the obstruction can awaken the sleeper, or at least cause the person to change to a lighter stage of sleep. These events result in release of stress hormones, changes in heart rate, changes in blood pressure, a drop in the blood oxygen level and other changes.
Apnea will ruin a night’s sleep. People perceive that sleep is a quiet, inactive time. However, sleep is a very active time for the brain. Imaging studies demonstrate that during sleep the brain functions at a high level in a rhythmic pattern. It could be interpreted as ‘when we sleep, the brain works and the body rests’. The obstruction of the airway, apnea, disrupts the rhythmic pattern of the brain during sleep. This pattern will be restarted over and over again, but the obstructive events interrupt the processes. A few individuals will wake when the obstructions occurs, but most will have no idea what is happening. They will complain of a bad night, feel like they haven’t slept or feel sleepy during the day. It affects each person differently, but for everyone, sleep is disturbed at some level by the obstructive events and symptoms usually follow. Symptoms and patients’ comments are listed in Table One.
The second effect of obstructed breathing is on the cardiovascular system. When an obstruction occurs, it results in a release of catecholamines (adrenal stress hormones) and changes in blood pressure and heart rate. The oxygen level drops repeatedly, often to dangerously low levels. Individuals with the Obstructive Sleep Apnea Syndrome suffer these events repeatedly night after night, week after week, and year after year. The cumulative effect results in medical problems. Patients with sleep apnea have higher rates of elevated cholesterol, diabetes, high blood pressure, heart attacks, and strokes. Patients with a high number of obstructive events die significantly younger than those who do not have apnea problems. Many other medical conditions are also thought to occur more frequently when apnea is present.
HOW IS THE SEVERITY OF OBSTRUCTIVE SLEEP APENA MEASURED?
The number of significant obstructive events that occur per hour measures the severity of obstructive sleep apnea. The events are reported as the apnea/hypopnea index (AHI). Symptoms usually are more frequent and intense as the AHI increases. Essentially all insurance companies use the AHI to indicate the presence of obstructive sleep apnea and rate its severity. Medical studies have confirmed that the long-term complications associated with obstructive sleep apnea do increase as the number of events per hour increases.
The higher the AHI measured during a sleep test, the greater the risk of medical complications. It has been demonstrated that an AHI of less than five has no long-term risk. However, an AHI of greater than thirty predicts a very high risk of developing problems. Obstructive sleep apnea is rated: AHI of five to fourteen – mild, AHI of fifteen to thirty – moderate, and AHI of greater than thirty – severe.
Other sleep test measurements also influence the reviewing physician. Individuals who show very long apneas (thirty to ninety seconds), very low blood oxygen levels and heart rhythm disturbances with the apneas, may be considered to have severe obstructive sleep apnea even when the AHI is only mildly or moderately increased. In addition, patients have been recognized who have symptoms of obstructive sleep apnea even when the AHI is less than five. These patients’ symptoms usually resolve on positive airway pressure therapy.