sleep apnea

Introduction

Sleep apnea is a medical condition that may adversely affect an individual’s quality of life and heath. The negative effects of sleep apnea range from annoying to life threatening. For pilots and controllers, sleep apnea may also compromise flying safety and may result in loss of FAA medical certification.

Fortunately, the condition is treatable. Most people treated for sleep apnea quickly notice a significant improvement in their quality of life. More importantly, treatment minimizes risk factors for negative health effects. Upon documentation of successful treatment, the FAA will consider reinstatement of a pilot or controller’s medical certification.

Prevalence

The National Institutes of Health estimates that 18 million Americans have sleep apnea. Approximately 4% of the adult population between ages 30 and 60 years has sleep apnea associated with daytime sleepiness. The estimated percentages rise to 7% in adults over age 60. Most sleep apnea (80%) is undiagnosed.

The prevalence is higher in men than in women. According to the New England Journal of Medicine, 16% of men and 22% of women have chronic daytime sleepiness alone, while 24% of adult men and 9% of adult women meet objective criteria for apnea while sleeping.

The FAA granted 1555 Special Issuance medical certificates (First Class = 279, Second Class = 335, Third Class = 1041) for successfully treated sleep apnea as of November 2003.

What is Sleep Apnea?

Sleep apnea is a potentially serious, and possibly life-threatening, condition resulting from interference or interruption of breathing when sleeping. Sleep is fragmented and is of poor quality. Most people with sleep apnea are unaware that they have this condition, although their bed partners are likely to have noticed some of the symptoms.

The syndrome was first described in the medical literature in 1965. However, within the last decade, the seriousness and potential complications of this disease are now being recognized. Interestingly, Charles Dickens described a character with massive obesity, snoring, disturbed sleep, a flushed face and daytime sleepiness in his novel, “The Pickwick Papers”. As a result, sleep apnea is often referred to as the Pickwickian syndrome.

Specific criteria define the various types of sleep apnea. In general, persons with sleep apnea will have more than five episodes an hour during sleep when they cease breathing for ten or more seconds. Often, the breathing will cease for more than 30 seconds and may occur up to 60 times an hour. Most people with sleep apnea will also have snoring and daytime fatigue.

Sleep apnea is associated with a number of medical conditions related to the cardiovascular system. It is also associated with headaches, anxiety, memory loss and poor concentration. The primary symptom is daytime sleepiness. Of major concern is the well documented increase risk of automobile accidents in people with sleep apnea NEJM 1999; 340:847-51 and NEJM 1999 340:881-883. Obviously, this finding also has significant implications for pilots/controllers and aviation safety.

Types of Sleep Apnea

Two major types of sleep apnea exist. The most common type, representing 90% of cases, is Obstructive Sleep Apnea (OSA). A second type is Central Sleep Apnea (CSA).

OSA is primarily a mechanical phenomenon with the structures of the mouth, tongue, neck and pharynx blocking an individual’s airway during sleep. These soft tissues cause repeated obstruction of the airways. This obstruction is caused both by gravity pulling tissues into the airway and by excess tissue encroaching on and narrowing the airway. As a result, the individual makes a respiratory effort that can be documented in the rib cage and diaphragm when monitored in sleep studies. However, because of the obstruction, there is restricted airflow through the mouth and nose.

Partial obstruction of the airway results in snoring. Snoring is produced when a small amount of air passes by a partial or intermittent obstruction in the airway. Usually, this obstruction is at the level of the oropharnyx (tongue, soft palette and epiglottis).

After a period of apnea (not breathing) or struggling to breathe, the individual arouses slightly, increases the tone of the muscles, unblocks the airway and then moves air through the mouth and nose into the lungs. This process is repeated dozens to hundreds of times during the night.

Essentially, OSA is a continuous cycle of sleep, snoring, obstruction, nocturnal arousal and sleep. The result is very fragmented, poor quality sleep. Significant cardiovascular side effects result from the apnea as well.

Central sleep apnea is a neurological phenomenon resulting from a failure of the brain to send a signal to the muscles of the rib cage and diaphragm to breathe. No obstruction is present in pure CSA. During monitoring, there is no activity in the rib muscles, diaphragm or the airway.

Mixed sleep apnea is a condition with components of both OSA and CSA. All types of sleep apnea result in a drop in the oxygen saturation of the blood. In an effort to compensate for the reduced oxygen saturation, the body will increase heart rate and blood pressure. This places additional strain on the cardiovascular system during sleep, a period designed for recovery rather than stress. Eventually, the reduced oxygen causes the brain to send a signal to the respiratory muscles to resume breathing.

Risk Factors

A primary risk factor for OSA is obesity, though not everyone with OSA is obese. People with short, thick necks may have compression of the airway when relaxed. The New England Journal of Medicine published an article on the increased risk of OSA in football players. An increase in the Body Mass Index of 1 (approximately 7 pounds in a six foot tall individual) increases the risk of abnormal sleep due to disordered breathing by 30% over 4 years.

Additional risk factors include a recessed or underdeveloped jaw. These conditions may force the soft tissues of the neck to a more rearward position than normal when supine and obstruct the airway. Chronic tonsillitis and upper respiratory infections/allergies may also increase the risk of OSA.

An association between hypertension and OSA has been documented. Approximately half of people with hypertension are estimated to have OSA and half of those with OSA will have hypertension. A similar relationship exists with obesity.

The risk of sleep apnea increases with increasing age. Family history of OSA is another risk factor. Other risk factors include abnormally excessive tissue in the throat or nasal passages. There is some controversy about whether nasal polyps or a deviated nasal septum will increase the risk of OSA.

Sedative medications, drugs and alcohol increase the risk of both central and obstructive sleep apnea.

Symptoms of Sleep Apnea

Persons who snore heavily should be evaluated for OSA. This is the primary symptom of OSA. Additionally, sleeping partners may notice that an affected individual may stop breathing for prolonged periods of time and then awake with a deep breath.

The second major symptom is daytime sleepiness. Because the night time sleep is fragmented and disturbed, daytime sleepiness is a manifestation of the body’s attempt to recover. Daytime sleepiness is especially common during period of relative inactivity. Sitting at a desk, reading, driving or flying when on autopilot are high risk times for falling asleep for people with OSA

Other associated symptoms are recent increases in weight, excessively loud snoring (“shake the bed, wake the dead”), awakening with a fatigued feeling despite an adequate period in bed and high blood pressure.

Adverse Medical Effects

The medical effects of sleep apnea can be significant. There are no conclusive studies that demonstrate a direct causal relationship with particular cardiac events. However, a growing body of literature links moderate and severe sleep apnea with hypertension, stroke, heart attacks, cardiac arrhythmias, congestive heart failure and death. The risk of hypertension is increased three-fold in people with severe OSA. Treating OSA may reduce hypertension.

Patients with OSA may also have complications following surgery. Sedatives and narcotics used may lead to reduced muscle tone in the muscles of the neck and pharynx during recovery. This may lead to reduced oxygen levels, increased carbon dioxide levels, heart rhythm irregularities and cardiopulmonary arrest.

Depression and anxiety may be exacerbated by chronic fatigue due to disturbed sleep. Additionally, OSA has been linked with memory loss and poor concentration.

Safety Threats

An alarming scientific study in 1999 demonstrated a six-fold increase in automobile accident rates in people diagnosed with OSA over those who did not have this condition. The risk was even higher if alcohol had been consumed on the day of the accident if the subject met the criteria for moderate or severe sleep apnea. These risks were independent of numerous other risk factors for automobile accidents. The study subjects were aged 30 to 70 years with a mean age of 44. Three quarters of the subjects involved were men.

An accompanying editorial in the same journal outlines recommendations to restrict driving in people afflicted with sleep apnea and other sleep disorders. Additional recommendations included having physicians report people diagnosed with sleep apnea to state motor vehicle authorities, similar to requirements for people with seizures. Diverse groups such as the American Thoracic Society, the Federal Highway Administration and several states have made these recommendations. California will issue a time-limited driver’s certificate requiring review every 3-6 months in partially controlled sleep disorders and suspends licenses in uncontrolled sleep apnea.

The FAA has similar concerns regarding pilots flying with sleep apnea. In solo operations, micro-sleeps or repeated “dozing off” may result in mishaps, deviations from ATC instructions or violations of Federal Aviation Regulations. In commercial operations requiring crew coordination, a pilot with uncontrollable fatigue presents an unacceptable risk to flight safety. Memory loss and impaired concentration still compromise safety, even in the absence of in-flight sleep. Policies on medical certification are discussed below.

Diagnosis

Sleep apnea must be distinguished from simple snoring and other causes of sleep disturbances. These causes include insufficient sleep, circadian rhythm disturbance, narcolepsy and periodic limb movements/restless legs syndrome. Conditions that may also present with excess daytime sleepiness include depression, anxiety, and use of medications and abuse of stimulants, sedatives and alcohol. [See International Classification of Sleep Disorders for a complete listing.]

A simple questionnaire may help identify people at risk for sleep apnea who should be formally evaluated. The Berlin questionnaire successfully predicted those people who had the most significant abnormal findings on sleep testing. Questions about weight change, snoring loudness, snoring frequency, breathing pauses, daytime fatigue, hypertension and falling asleep when driving are used in the Berlin survey. Several alternate surveys exist addressing OSA risk. One in common use is the Epworth Sleepiness Scale, which develops a score based on a person’s self-rating of likeliness to fall asleep in eight situations.

Individuals at high risk for sleep apnea or those who have symptoms such as daytime sleepiness, multiple automobile accidents and loud snoring should be referred for formal sleep testing. Additionally, people with short, thick necks or recessed jaws may benefit from testing.

Sleep Testing - Polysomnogram

The diagnosis of sleep apnea is confirmed by testing known as nocturnal polysomnography. The polysomnogram (PSG) measures a number of physiological factors when an individual is sleeping. Factors include brain wave activity (electroencephalogram), eye movement, airflow, chest movement, leg movement, heart rhythms (electrocardiogram) and oxygen saturation of the blood. Video monitoring is sometimes conducted during the PSG.

Two measures characterize the severity of abnormal breathing during the PSG. The Respiratory Disturbance Index (RDI), used in home/portable monitors, is a measure of the number of breathing disturbances during one hour of monitoring. The Apnea – Hypopnea Index (AHI) is used during the more formalized PSG testing. It describes the number of time breathing ceases (apnea) or is sub-optimal (hypopnea) per hour of monitoring. The RDI and AHI are roughly equivalent.

A RDI/AHI of less than 5 usually is interpreted as normal. “Mild” sleep apnea usually is associated with a RDI/AHI of 10-20. Higher RDI/AHIs may be characterized as “moderate” (20-30) or “severe” sleep apnea (greater than 30). These RDI/AHI figures are not rigid. Other factors, such as measured daytime sleepiness and oxygen saturation during sleep influence the classification of mild, moderate and severe sleep apnea.

Oxygen saturation of the arterial blood should remain above 90% in the normal individual when sleeping. The PSG measures both the mean and the minimum oxygen saturation during the study. Lower oxygen saturations raise concern about the severity of the sleep apnea.

Frequently, polysomnography may be divided into two phases during the same study. The first phase measures all parameters in the natural state of sleep. The second phase measures the same factors when the individual is being treated for the sleep apnea (see below) to see if there improvement with treatment. This type of PSG is known as a “split sleep study” or a “split-night study”.

Sleep Testing - Maintenance of Wakefulness / Multiple Sleep Latency Testing

The Maintenance of Wakefulness Test (MWT) and the Multiple Sleep Latency Test (MSLT) are different measures of daytime sleepiness/alertness. For a full description, see the American Sleep Disorders Association (now the American Academy of Sleep Medicine) report. Stimulants and medications may affect the quality and accuracy of each study.

Both studies are administered in a darkened quiet room in a reclined position. Each involves a series of four or five 20-minute periods in the room with 2-hour intervals between the periods where the subject is instructed to stay awake. The five cycle MSLT is used to evaluate possible narcolepsy while the four-cycle studies may be used to evaluate other sleep disorders. Ideally the studies are administered following a PSG. The ability to remain awake during this testing may be improved by sleeping in a familiar environment the night prior to the study, if there is no sleep disturbance present.

During the MSLT, an individual is instructed to fall asleep during the 20-minute nap period. The MSLT measures the time it takes an individual to fall asleep. A normal individual will usually require over 15 minutes before falling asleep (latency) as measured by an EEG. Mild alertness impairment may be present if the sleep latency period is between 10-15 minutes, although normal individuals may have occasional periods of reduced sleep latency. Latency periods of 5-10 minutes may indicate moderate impairment and shorter period may be characterized as severe.

In contrast to the MSLT, an individual undergoing a MWT is instructed to stay awake during the period in the dark, quiet room. The expected result in a person without a sleep disorder is to remain awake during each of the four 20-minute periods and during the 2-hour intervals when walking or participating in normal activities. The MWT evaluates daytime alertness and is more relevant for medical certification authorities. The FAA prefers the MWT to the MSLT in evaluating individuals following treatment for sleep apnea.

Some sleep clinics routinely perform drug testing in conjunction with PSGs, MWTs and MSLTs to document that neither sleeping medications nor stimulants to stay awake have been used to influence the results of testing.

Obstructive Sleep Apnea Treatments

The goal of treatment of OSA is maintenance of an open, unobstructed airway during sleep. Both surgical and non-surgical treatments are available. Several treatments are acceptable to the FAA in pilots/controllers diagnosed with OSA who seek reinstatement of medical certification. However, some treatments offered for correction are not acceptable to the FAA, primarily because their effectiveness cannot be consistently demonstrated.

Nonsurgical Treatments

The most widely used and effective treatment is Continuous Positive Airway Pressure (CPAP). This treatment involves wearing a mask over the nose and strapped around the head. The mask is connected to a tube that has a fan blowing air continuously thorough the nostrils. The air pressure, which can be adjusted as necessary, keeps the soft tissues from collapsing the airway and allows regular, unobstructed breathing through the night.

Variants of CPAP include nasal CPAP (nCPAP) which uses nasal “pillows” in the nostrils instead of a mask, and BiPAP which has varying air pressures in different phases of respiration to enhance comfort. A variety of masks may be used to adjust to an individual's facial structures.

Adverse effects of CPAP may include a runny nose, nasal congestion, skin irritation from the mask and irritation / intolerance of the mask. Some people have claustrophobia to an extent that they cannot tolerate the nasal mask. Overall, non-compliance is the most significant issue in treating OSA non-surgically with CPAP.

CPAP requires a shoebox-sized machine with the fan and pressure adjusting mechanism, the associated tubing and mask and an electrical supply. Pilots who participate in transoceanic flights with rest periods may find it very challenging to set up and use a CPAP device on the aircraft, although once on the ground, treatment is usually much easier.

CPAP and its variants are the only non-surgical treatments for OSA authorized by the FAA for pilots and controllers.

Oral appliances that bring the jaw forward or prevent the tongue from relaxing back and obstructing the airway are also use to treat OSA. These devices are not as effective as CPAP or surgery in relieving OSA, but may reduce snoring. These devices may be used to complement CPAP and surgical treatments for OSA. They may also be used in persons not tolerating CPAP or declining surgery.

Weight reduction is another non-surgical approach to OSA. Unfortunately, the long-term success of weight loss programs is low. Even with gastric by-pass surgical procedures, weight loss does not result in any immediate improvement in OSA or daytime sleepiness. The FAA does not recognize weight loss alone as a sufficient treatment for medical certification.

Oxygen supplementation may be used to complement CPAP, but is not adequate as sole therapy because it does not relieve the obstruction.

Sleep posture modification has also been attempted. Because airway obstruction may be due to gravity pulling soft tissues of the neck against the airway when lying on one’s back, sleeping on the side may relieve snoring and airway obstructions. One method of sleep posture adjustment has been to wear a sleep-shirt with tennis balls sewn into the back. When feeling the pressure of the tennis balls, an individual wearing such a shirt will tend to roll from lying on the back to on the side. This method is not an FAA-approved treatment for medical certification purposes.

Surgical Treatments

If conservative measures such as CPAP are ineffective or not tolerated, surgical treatment options for OSA exist.

The primary surgical correction for OSA caused by excessive or redundant tissues in the pharynx is termed uvulopalatopharyngoplasty (UPPP). The tonsils, if present, are removed as are the uvula and rear portion of the palate. The surgery may reduce the RDI/AHI by approximately 50%. It is very effective in reducing snoring. The UPPP may require several days of hospitalization. The recovery period may extend from several weeks to two months.

An alternate to the UPPP is the laser-assisted uvulopalatoplasty (LAUP), which can be performed in the office setting using local anesthesia. The procedure involves using a laser to resect the uvula and soft palate. The LAUP is also effective in relieving snoring.

A third procedure used in people who have a recessed jaw is termed mandibular advancement. It is the most invasive and involves a prolonged recovery period with the upper and lower jaws wired together.

Another surgical procedure to treat OSA, albeit indirectly, is gastric (stomach) surgery in massively obese individual in an effort to drastically reduce weight. Hopefully, with reduction of weight over time, the excessive tissues compressing the airways will be reduced. This procedure does not have an immediate effect on improving OSA, even if it is successful. When determining medical qualification, the FAA does not consider this treatment, by itself, to be typically adequate in pilots and controllers with OSA.

FAA Policies and Certification Issues

The primary concern of the FAA with sleep disorders relates to alertness when on duty in the cockpit or tower cab. Secondary concerns involve the complications and associated symptoms of sleep apnea, such as memory and concentration impairment, heart arrhythmias and other conditions that may cause subtle or sudden incapacitation when flying or controlling. Under current policy as outlined in the FAA Guide for Aviation Medical Examiners, any degree of sleep apnea is disqualifying for all classes of medical certification. AMEs do not have the authority to grant an initial waiver for medical certification for pilots with sleep apnea.

Pilots diagnosed with sleep apnea may be granted medical certification under the Special Issuance provisions of 14 CFR 67.401. Controllers may get Special Consideration from the Regional Flight Surgeon. The FAA Protocol for Evaluation of Sleep Apnea outlines procedures for testing in support of recertification requests. The essential elements are a split-study or second PSG following treatment, a normal MWT or MSLT and documentation that the pilot/controller no longer experiences any daytime sleepiness. The individual must tolerate and comply with the treatment for OSA. The FAA usually requests an annual physician current status report in individuals requiring treatment as a requirement to maintain Special Issuance medical certification.

Summary

Sleep apnea is a relatively common medical condition with potentially serious medical and occupational consequences. For people performing safety sensitive duties, the daytime sleepiness associated with sleep apnea is the most immediately hazardous consequence. Persons with risk factors for or symptoms of sleep apnea should be evaluated with polysomnography. Several treatments are available in individuals for whom the diagnosis is confirmed. The success of the treatment should be evaluated both using repeat PSG and MWT/MSLT. With successful treatment of sleep apnea, FAA medical certification is likely. Treatment will result in improvement of subjective symptoms and health complications of sleep apnea.