EMS Flight Safety Decisions

Issues of Concern

Illness

Piloting aircraft is a task that requires constant focus and attention for prolonged periods to conduct safe flight operations. All illnesses, including the common cold, can adversely affect flight safety. For instance, nasal and sinus congestion during flight can lead to severe, acute pain that may abruptly resolve with tympanic membrane perforation due to the changes in barometric pressure that often accompany flight. Gastroenteritis, accompanied by dehydration and the frequent urgency to eliminate, can impair focus on instrument cross-checking, in-flight airspace clearance, and quick response to deconfliction instructions.[1] Febrile illness can affect wakefulness and job performance, both necessary for safe flight.[1] Before flight, each crew member should systematically check their health to determine whether they feel well enough to fly. Designated flight physicians (flight surgeons in the military) are specially trained to assist in the treatment of transient illness and to help the aviators and passengers determine whether medications are necessary, which ones are safe, or if the illness presents a No-Go condition.[2]

Medication

The internal pressure exerted by each aircrew member and passenger manifest to complete the flight is also a risk factor, often making flyers reluctant to disclose an illness. Previous studies of fatal aviation accidents have shown that pilots may not accurately self-report medication usage, with up to 96% failing to disclose the use of psychiatric medications before studied mishaps.[3] The awareness that even a minor illness could be a No-Go event—and that the flight physician may ground the affected aircrew member—occasionally causes the member to self-medicate without medical advice. This practice is against military regulation and strongly discouraged in civilian aviation by the FAA. According to the Official Air Force Aerospace Medicine Approved Medications list, many over-the-counter medications that are seemingly benign to the patient can negatively impact performance. The FAA Guide for Aviation Medical Examiners provides similar guidance in its Over-the-Counter Medications Reference Guide. Clinicians should refer to specifically approved medication guidance to ensure no prescription written requires a grounding period before resuming flying duties.  

Stress

Short-term stress has been shown to positively impact the performance of mental and physical tasks (more so in women than men), but chronic stress can impair spatial memory and performance in some individuals.[4] stressors can include financial problems, marital issues, legal troubles, family discord, or health concerns. If an aviator is experiencing chronic, unmanaged, or acute stress, it can affect their ability to focus, communicate, and function safely as part of the aircrew. External stressors such as pressure to complete the mission no matter what, return home, impress a rater, demonstrate proficiency, or prove a point can induce the flyer to take unnecessary risks, potentially resulting in actions that could be injurious or fatal. Mitigation strategies for those reporting stress often involve interviewing aviators and referring them to appropriate support staff to address the issue, especially if it is severe enough to require a period of non-flying. Open communication within the crew is the first step in mitigating stress-related risks.[5] Other crew members should be aware when their wingman is under increased stress. If the mission continues, they should have a lower threshold for voicing concerns or, if necessary, terminating flying activities in the air due to any decline in that airman's performance.[6]  

Alcohol

Alcohol consumption impairs the aircrew member's ability to perform mission-essential duties and serves as an additional stressor. Alcohol lowers the threshold of hypoxia tolerance and increases the risk of spatial disorientation, which can be life-threatening for everyone on board.[7] The FAA mandates a minimum of 8 hours between the last alcohol consumption and aircrew responsibilities. In contrast, the military requires 12 hours between the last consumption of alcohol and aircrew responsibilities, often referred to as the bottle-to-throttle rule. Aircrew members must self-identify if they fall within these parameters, and all members of the aircrew, medical, and technical support staff regard this as a No-Go for the safety of flight.[8]

Fatigue

Human error is the leading cause of aviation accidents, accounting for 60% to 80% of such incidents in the United States due to human factors.[9] Fatigue is the primary human factor, according to the NTSB, due to long shifts, frequent time zone changes, and short rest periods between flight duties. As wakeful time increases, symptoms of fatigue worsen, including slower reaction times, decreased concentration, increased risk tolerance, and impaired decision-making ability.[10] Short rest periods between flights lead to increased levels of serum cortisol and dehydroepiandrosterone in pilots.[11] Studies have shown that less sleep, longer duty hours, and early starts contribute to more significant fatigue, especially when accumulated over a 7-day period.[12] In civilian aviation, a study found up to 7% of aviation incidents were due to aircrew fatigue. In military aviation, Air Force statistics note fatigue as a factor in 7.8% of Class A mishaps—the most serious type of aviation accident—and Army statistics found fatigue to be a contributing factor in 4% of accidents.[13] A study by the FAA evaluating 50 aviation accidents over 20 years found a significant increase in accidents involving pilots who had been on duty for 13 hours or more.[14]

In 2011, the FAA established more stringent regulations to decrease pilot fatigue by limiting duty hours and mandating crew rest periods. These regulations apply universally to domestic, international, or unscheduled flights, with stricter limits depending on the number of flight segments and duty day start time. Key guidelines include a minimum of 24 hours off in a 7-day period, limited flight hours per given time period, and a minimum of a 9-hour rest period between shifts, with longer rest periods for extended flights.[15] Members of the International Civil Aviation Organization have inscribed shift hour limitations; however, implementation is variable and does not consider the accumulation of sleep debt and circadian rhythm disruption.[16]

The primary strategies for managing circadian rhythm dysrhythmia or jet lag include gradually adjusting sleep and wake times before a time zone change, using light therapy, and practicing good sleep hygiene, such as avoiding caffeine, alcohol, strenuous exercise, and heavy meals right before bedtime.[17] To manage circadian rhythm dysfunction when crossing time zones, eastward travel recommendations include moving back both sleep and wake times 30 minutes per day starting 3 days before departure and, for westward travel, 30 minutes forward. Another helpful suggestion for eastward travel is to increase bright light exposure during the first 2 to 3 hours after waking and to avoid bright light close to bedtime. This strategy may require wearing sunglasses while driving and using heavy window treatments to effectively block sunlight. The opposite is advised for westward travel, with a recommendation to increase light exposure in the evening and to avoid bright light just after waking up for several hours.[18]

If first-line non-pharmacological management is not sufficient, caffeine may be used to improve alertness. Although civilian aircrew is not permitted to use stimulants, military personnel may be prescribed go pills such as dextroamphetamine and modafinil to help reduce drowsiness during flights.[19] Sedatives, also called no-go pills, such as zolpidem, temazepam, and zaleplon, are prescribed to manage circadian rhythm mismatch. Due to the varying half-lives of medications and potential adverse effects, their use is closely regulated and limited.[20]

The FAA does not approve the routine use of sleep aids besides melatonin. In addition,  FAA regulations require that pilots refrain from flying for a minimum of five times the duration of a drug's half-life. For instance, although diphenhydramine is available over the counter, due to its long half-life, a pilot must wait at least 60 hours after taking it before resuming flying duties. For no-go pill use in the military, over-the-counter medications such as diphenhydramine are not approved for aircrew use. In civilian aviation, zolpidem is permitted no later than 24 to 48 hours before taking off, depending on the formulation. However, zolpidem is typically the sedative of choice for military operations, with a moderate-length do-not-fly timeframe of 6 hours. Temazepam is the longest-acting sedative allowed in military operations, with a 12-hour restriction on subsequent flight duty. In contrast, temazepam use in civilian aviation requires 72 hours before the next flight duty. Zaleplon has the shortest half-life of all the sedatives allowed in military aviation, with only a 4-hour restriction before flight duty. In civilian aviation, zaleplon use requires 12 hours before flight duty. Other sedatives approved by the FAA for civilian aircrew use but not in the military include eszopiclone, which requires a minimum 30-hour wait before flight duty, and ramelteon, which requires a minimum 24-hour wait before flight duty.

Caffeine is the most commonly used psychoactive drug to promote wakefulness and has been shown to enhance cognitive performance in long-haul aviation conditions.[21] The FAA does not approve the use of prescribed stimulants, or go pills, such as modafinil and dextroamphetamine, for commercial pilots. However, in the military, these medications are used under strict regulations to maintain wakefulness during unavoidable long sorties. Pilots must undergo prior ground testing to assess potential adverse effects before in-flight use. Adverse effects of stimulants include insomnia (the intended adverse effect), decreased appetite, weight loss, hypertension, tachycardia, lightheartedness, headaches, irritability, overconfidence, aggression, and gastrointestinal effects such as diarrhea, constipation, and abdominal pain. There is also limited evidence of increased tics, so caution is advisable for patients with tic disorders such as Tourette syndrome. Technically, modafinil is not classified as a stimulant, but it does have stimulant-like effects. Like stimulants, modafinil does improve alertness and wakefulness. Modafinil has a slower onset with a half-life of 15 hours, so it tends to have fewer adverse effects than dextroamphetamine.[22] Dextroamphetamine has a shorter half-life of 12 hours with a quicker onset, so it tends to have more noticeable adverse effects and requires more frequent re-dosing. Non-pharmacological management of fatigue is considered the first-line approach.[23]

Emotion and Energy

The FAA requires aircrew members to assess if they are emotionally upset or have any acute physiological needs, such as hunger. These immediate needs can impact the ability to focus on less existential needs such as airspeed, altitude, and other flight safety matters. Hunger is typically easy to address during the preflight period. Identifying emotional states and discussing them before take-off can help mitigate negative emotions. However, self-awareness should sometimes lead an airman to seek guidance and support in dealing with emotional stress. Flight physicians may choose to allow airmen time for personal recovery during a no-flight period to prevent any aviation-related mishaps caused by impaired focus.

Clinical Significance

The safety of flight begins on the ground during the preparation and planning stages of the mission. Just as the aircraft undergoes preflight inspection for wear and tear, with anticipated maintenance performed before the mission, the aircrew conducts a mandatory risk assessment individually and as a team to ensure that human factor risks do not outweigh the necessity of the mission. Human error is the leading factor in most aviation accidents and becomes worse with illness, inappropriate medication use, stress, alcohol, fatigue, and immediate physiological or emotional needs. Healthcare teams should be aware of the I-M-S-A-F-E preflight check for the crew. As a clinician, it is essential to be aware of the known risks contributing to human factors in flight safety decisions to Go/No-Go and how to counsel aircrew on mitigating risks through the therapeutic alliance, behavioral guidance, and pharmacological interventions, if necessary.