by MAJ Devon Greer, MD
Q: I was recently diagnosed with Central Sleep Apnea (CSA) and have my upcoming medical examination. I’ve heard of Obstructive Sleep Apnea and its impact on flight status, but what is Central Sleep Apnea? Will it affect my flight status? How is it treated? Does flying affect it?
FS: Central Sleep Apnea (CSA) has many of the same symptoms of Obstructive Sleep Apnea (OSA) but is significantly different. CSA occurs when the brain fails to tell the diaphragm and ribs to breathe, and that causes shortness of breath while sleeping. This tends to break up sleep, causes wakening, and sleepiness during the day due to poor quality sleep. OSA is similar because breathing interruptions cause night awakenings, but the root cause is choking on a collapsed airway. In OSA, the brain is still sending signals to breathe, but the airway is blocked. CSA and OSA can occur together, called “Mixed Sleep Apnea.” Treatment of OSA with CPAP sometimes uncovers underlying CSA that was previously undiagnosed. There are a number of different types of CSA based on the root cause of the interruption in breathing, some reversible, while others are not well understood or treated. Doctors may need to test for underlying causes, such as heart disease and lung diseases. If a cause is found, it may affect your flight status until it can be adequately controlled.
Central Sleep Apnea is important in Aviation because it carries the same symptoms and risks as Obstructive Sleep Apnea. These include sleepiness during the day, reduced concentration, increased risk of errors, and development of medical issues, such as hypertension, pulmonary hypertension (high blood pressure in the lungs), and heart failure. Although CSA or OSA has not directly been responsible for accidents in Federal Aviation Administration (FAA) investigations, the diagnoses were directly responsible for a near-miss when both pilot and copilot fell asleep and overflew their destination. Fatigue is consistently a listed concern of the National Transportation Safety Board that is responsible for mishap investigations on the ground and in the air. As such, untreated sleep disorders are considered incompatible with flight even when the exact syndrome is not specifically named in medical requirements for flight in the military or FAA.
As a further complication, high-altitude exposure can worsen CSA and associated symptoms. Since these evaluations occurred at high altitude camps, it is not clear if flying in unpressurized aircraft bears a similar risk. Short duration trips to elevated altitude do seem to cause more symptoms and worse clinical scores (such as sleep study results and concentration tests) than those who live and acclimatize at high altitude. This makes it possible that flight (particularly 15,000 ft above sea level) may develop or worsen CSA and its outcomes. Further study to evaluate how flight relates to the development, symptoms, and treatment of CSA remains necessary.
Treatment of CSA is a current area of research. Most people with CSA receive a trial of Continuous Positive Airway Pressure (CPAP) therapy, similar to OSA. However, the response rate and improvement of symptoms using CPAP is much lower with CSA than OSA. Other forms of positive pressure therapy that may be more effective, such as BiPAP, which can force a baseline breathing rate. Some improve on these therapies, but they can be harder to tolerate. Some trials suggest certain patients improve using simple supplemental oxygen during sleep, but this does not help every patient. Another treatment is Acetazolamide (Diamox®), usually used to help people adjust to altitude. It seems to improve breathing patterns and symptoms for many patients with CSA. Finally, treating underlying causes for CSA is vital. Heart disease, obesity, brain lesions, and other illnesses may cause CSA. Treating those illnesses may resolve CSA entirely.
What does this mean for a pilot with Central Sleep Apnea? The disease puts pilots at a higher risk of mishaps if it is not treated effectively and sleepiness persists. Flight surgeons will apply the same precepts used in treating OSA towards CSA evaluations. To ensure a pilot with CSA is safe to fly, the pilot must demonstrate that nighttime awakening and symptoms resolved with treatment. If symptoms persist despite appropriate treatment, then it’s not safe to fly. Although CSA is more challenging to diagnose and treat than OSA, it can be treated for the majority of people. Your flight surgeon is there to help you through the diagnosis, management, and treatment to ensure you’re safe to return to flight. Reach out to your flight surgeon and you can work together to keep you healthy and flying.
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The views and opinions offered are those of the author and researchers and should not be construed as an official Department of the Army position unless otherwise stated.
MAJ Devon Greer, MD, is a flight surgeon at the United States School of Army Aviation Medicine, Fort Rucker, AL