WHAT CAUSES OBSTRUCTIVE SLEEP APNEA?
WHAT DOES OBSTRUCTIVE SLEEP APNEA DO?
HOW IS THE SEVERITY OF SLEEP APENA MEASURED?
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 frequently
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
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 1 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.
(*Note: Please click illustrations to
FIGURE 1 – NORMAL BREATHING DURING SLEEP
FIGURE 2 – SLEEP APNEA DURING SLEEP
Figure 2 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.
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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 1.
OF OBSTRUCTIVE SLEEP APNEA
FREQUENT MOVEMENTS (Tossing and turning)
FREQUENT NIGHTTIME URINATION
AWAKING FROM CHOKING
AWAKING FROM SNORING
SLEEPINESS ON AWAKING
SLEEPINESS DURING THE DAY
EXCESSIVE STIMULANT USE
MOOD DISORDERS (DEPRESSION) WITH SLEEP COMPLAINTS
FREQUENT PATIENT COMMENTS
“I can drink a cup of coffee at bedtime and go to
“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
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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 3 shows the normal anatomy of the upper airway. The obstruction
in sleep apnea occurs above the larynx.
FIGURE 3 – 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
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 4 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
FIGURE 4 – OBSTRUCTION OF THE AIRWAY IN SLEEP
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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
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, 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 1.
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.
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HOW IS THE SEVERITY OF OBSTRUCTIVE
SLEEP APNEA 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
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