Clinical
Practice Guideline
for
SLEEP
DISORDERS
Developed for the
Aerospace Medical Association
by their
constituent organization
American Society of Aerospace Medicine Specialists
Overview: The common thread running through
most sleep disorders is insufficient quantity or quality of sleep, which leads
to excessive daytime sleepiness and diurnal impairment of alertness and
cognitive function. While pathologic
sleep disorders command the greatest attention, one of the commonest causes of
excessive sleepiness, particularly in young adults, is poor sleep hygiene. Chronic sleep deprivation due to individual
behavior patterns may cause as much debility as a pathologic disorder. While the definition of sufficient sleep
varies, one should generally not work up a complaint of hypersomnolence unless
the individual is attempting to get six to eight hours of sleep for a
twenty-four hour period, on a reasonably regular schedule. Careful attention must also be paid to
alcohol use, since heavy use may disrupt sleep patterns, and may induce or
worsen sleep apnea.
In civilian practice,
insomnia is the commonest sleep complaint.
The pattern of disturbance is usually helpful; chronic difficulty
initiating sleep is most often associated with anxiety or stress, while early
morning awakenings suggest depression.
Frequent brief awakenings throughout the night are more suggestive of
sleep-disordered breathing.
While narcolepsy was the
classic sleep disturbance, the first description dating back to 1880, it is
actually relatively rare. Narcolepsy is
an exception to the rule noted above; narcoleptics tend to have a disrupted
pattern of sleep, but the hypersomnolence is not simply related to sleep
deprivation. Instead, narcolepsy appears
to be a neurologic disorder characterized by the early onset of rapid eye
movement (REM) sleep, with an age of onset usually in childhood or
adolescence. The intrusion of REM
patterns into different parts of the sleep-wake cycle may lead to unusual manifestations,
such as hypnagogic (predormital) and hypnopompic (postdormital) hallucinations,
and sleep paralysis. While classic,
these manifestations usually occur only in about a quarter of narcoleptic
patients. The essential disorder in
narcolepsy is nearly uncontrollable attacks of sleepiness leading to brief
naps, from which they usually awake feeling refreshed. Narcoleptics also experience episodic lapses
of consciousness typified by automatic behavior and amnesia. Most subjects if questioned carefully have
also had some form of cataplexy, characterized by loss of postural control
(e.g., head drooping, knees buckling, even falling) associated with laughter or
other emotions.
Obstructive sleep apnea (OSA)
has emerged as a major sleep disorder.
The best available estimates of prevalence suggest that among American adults ages 30 to 60, 4% of males and 2% of females are
affected. Prevalence among military
aviators is unknown, but because obesity is much less common in that
population, the rate is likely to be considerably lower. The key in OSA lies in the pattern of muscle
activity that occurs in different stages of sleep. While diaphragmatic activity is largely
unaffected by sleep stage, muscle tone in the upper airway is considerably
depressed in stages III and IV of non-REM sleep, a pattern which continues
throughout REM periods. This loss of
muscle tone leads to increased resistance to airflow through the upper airway
during inspiration; in expiration, on the other hand, positive intraluminal
pressure tends to stent the pharynx open.
A modest amount of obstruction results in snoring,
while a greater amount of obstruction may lead to hypopnea (>50% reduction
of airflow for >10 seconds) or apnea (total cessation of airflow for >10
seconds). The disordered
breathing causes either awakening or a lighter stage of sleep, which in turn
results in fragmented sleep, while apneic episodes of sufficient duration may
produce arterial hypoxemia. More
recently it has been recognized that the increase in airway resistance itself,
even in the absence of an actual decrease in airflow, may be enough to cause
sleep fragmentation, a phenomenon known as the upper airway resistance syndrome
(UARS). While the existence of this
entity has been documented by esophageal manometry, with awakenings correlated
to excessively negative intrathoracic pressures, the use of an esophageal
balloon is too invasive for most clinical situations. Instead, UARS is usually diagnosed
presumptively when the snoring patient with hypersomnolence and sleep
fragmentation responds to a diagnostic trial of nasal CPAP during
polysomnography.
The predominant symptom is
typically daytime sleepiness; the greater the degree of sleep apnea, the more
likely the individual is to fall asleep, especially when involved in boring or
repetitious activity. He or she may feel
an urge to nap, but unlike in narcolepsy these naps are usually not refreshing,
since the disordered breathing occurs there as well. Sleep apnea may be associated with restless
nocturnal behavior, choking sensations resolving immediately upon awakening (as
opposed to esophageal reflux with aspiration), vivid dreams of
strangulation/drowning, and in severe cases with morning headache (due to
hypercarbia). While these symptoms are
classic for OSA, the only symptom in moderate cases is typically
hypersomnolence of varying degree.
Recent development or worsening of symptoms is frequently due to weight
gain. When symptoms are variable,
particularly when a symptomatic patient has a negative polysomnogram, one
should pay particular attention to the alcohol history.
Sleep apnea is clearly
associated with hypertension. Sleep
apnea patients have a 41% prevalence of systemic hypertension, about double
what would be expected. The cause is
unclear, though it may be due to sympathetic overstimulation from multiple
arousals. Nocturnal hypoxia may
occasionally result in cardiac arrhythmias, including ventricular tachycardia,
a phenomenon primarily seen in older patients.
Those with severe sleep apnea may develop diurnal hypoxia and hypercarbia,
and eventually pulmonary hypertension and right-sided congestive heart failure.
Diagnosis of pathologic sleep
disorders requires polysomnography (PSG) at a sleep disorders laboratory. This involves monitoring at least one night’s
sleep with electroencephalography, submental electromyography, electro-oculography, measurements of airflow and
thoracic/abdominal excursion, and oximetry.
Usually electrocardiography and video monitoring are performed as
well. If the polysomnogram suggests
narcolepsy, multiple sleep latency testing needs to be performed the following
day. The overwhelming problem with sleep
laboratories is the huge degree of variability of results. Even accreditation is no guarantee, because
standards for interpretation have been difficult to establish.
While multiple treatment
options usually exists for sleep apnea, not all are
compatible with aviation or worldwide duty.
Positional therapy is likely to be effective only in mild OSA, and even
then only when a significant positional component is identified during the
sleep study. Medications have largely
been ineffective for OSA, and those that have been tried are not waiverable
drugs in and of themselves. Oral
appliances, which attach to the teeth or more rarely the tongue to advance the
lower jaw, are frequently effective in moderate OSA, and are fully
waiverable. Nasal continuous positive
airway pressure (CPAP), which acts as a pneumatic stent to maintain airway
patency, is usually effective for any degree of sleep apnea. Compliance with long-term use has been a
problem. For active duty personnel, the
more immediate problem is that the use of CPAP is incompatible with worldwide
qualification, since the device needs a continuous power supply. Several surgical options are available for
OSA, including such procedures as palatoplasty and mandibular advancement; if
effective at controlling the problem, any of these is waiverable. Tracheostomy would obviously not be
waiverable, but is no longer performed for OSA.
Narcolepsy is controlled by medications, but neither the disease nor the
medications are waiverable for military aviation.
Aeromedical Concerns: Any of the sleep disorders above may result in excessive daytime sleepiness and an inability to maintain the alertness necessary for safety while flying. Cognitive function and neuromuscular coordination may both be affected by the sleep disorder and/or the treatment modalities used. When called upon to perform in operational situations with less than optimal sleep, those with OSA are already sleep deprived. Furthermore, normal individuals when sleep deprived respond by altering sleep patterns, e.g., going into REM early or even immediately, but in the individual with OSA those deeper stages of sleep are fragmented by disordered breathing. Persons with a sleep disorder may have more than the usual difficulty in adjusting to the circadian rhythm disruption which occurs with travel across time zones. This would present an additional hazard to a flier who may travel or deploy several time zones away and would still be expected to perform flying duties.
Medical Work-up: If there is a high index of
suspicion of a sleep disorder, it is very important that the aviator obtain a
sleep study from an accredited sleep center.
Any aviator with a documented sleep disorder will require a thorough
aeromedical evaluation prior to returning to flying duties. That evaluation should include a
polysomnography at a sleep laboratory and neuropsychologic testing to evaluate
cognitive function.
If an aviator is diagnosed with OSA, it is reasonable to
treat him or her with an oral appliance to try to control the problem prior to
the waiver evaluation. However, given
the extreme variability in civilian sleep studies, it is difficult to make the
same recommendation concerning surgery.
If the aviator does not have symptoms clearly associated with the
diagnosis, the disorder should be confirmed at a sleep center before
considering a surgical procedure.
If narcolepsy is diagnosed or considered, it may be useful
to get a second opinion as this often will result in permanent disqualification
from all flying duties.
Aeromedical Disposition
(military): Aviators
with mild documented OSA are waiverable for full flying duties. Aviators with moderate or severe OSA must be
controlled by either an oral appliance or surgery before waiver will be
considered. However, aviators with mild
to moderate OSA may be considered for waiver if results of neuropsychologic
testing are normal.
Aeromedical Disposition
(civilian): In the
case of a civilian airman, they may present for examination after they have
already been diagnosed with a sleep disorder. If they do, then they need to
provide a current status report and a Maintenance of Wakefulness Test (MWT).
This is a test where the airman is monitored in a dark room for four periods
spread out throughout the day. There is
a twenty and forty minute version and both are acceptable. The airman cannot use artificial means to
stay awake during the test. If the airman falls asleep for more than a total of
90 seconds during the four study periods they are considered to have failed the
test for FAA purposes.
The FAA accepts the following treatments: CPAP, BiPAP, oral
fixation device, Uvuloplasty (UPPP), and Nasal septal surgery. They do not accept any medications such as
Provigil nor do they accept the use of tennis balls sewn into pajama top.
Aeromedical Disposition (NASA): OSA and any sleep disorder that may interfere with the
performance of duties are disqualifying for spaceflight duty.
Waiver Experience (military): A military database was queried with data going back to
2001. There were 128 aviators with
waiver requests for the diagnosis of sleep apnea. Of that total, 48 were disqualified for
flying duties, one of whom had earlier been granted a waiver. This is an approval rate of 62%.
Waiver Experience (civilian): As of 2007 there are
898 first-class, 873 second-class and 2,184 third-class airmen currently issued
with sleep apnea diagnosis.
Waiver Experience (NASA): There are no current waivers for OSA, though a history of
OSA would be considered if the astronaut had successfully treated the condition
through weight loss or surgery. Other sleep disorders would not be waiverable
if they interfere with crew duties.
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Updated: January 19, 2008