Aeromedical transportation involves the use of fixed-wing (airplane) or rotor-wing (helicopter) aircraft to move patients from one location to another. Using aircraft for this purpose began in World War I, with the goal of moving wounded soldiers from the battlefield to hospitals in a more rapid manner. Today, the civilian and military sectors depend on helicopters and airplanes to respond to medical and trauma emergencies that may not be well served by ground ambulances. Approximately 3% of all ambulance transports in the United States are performed by aeromedical assets, with over 300 air ambulance services, 1000 bases, and 1400 registered aircraft according to the 2017 Atlas and Database of Air Medical Services (ADAMS). The care emergency medical service (EMS) providers offer has changed drastically over the past 60 years. Advancements in technology and field care now allow EMS to provide critical medical and trauma care while moving the patient toward definitive care.
This article reviews basic information regarding comparisons between air and ground transportation, medical care provided in aircraft, different mission profiles, safety and cost considerations, preparing patients for transport, and the potential clinical impact of air medical services.
The safety of aeromedical assets is an important focus when comparing aeromedical to ground transportation. Rotor-wing aircraft have drawn intense scrutiny because of multiple high profile crashes. Because of the rapid response requirements and often unsecured scenes, helicopter EMS (HEMS) units are considered the highest risk mode of patient transportation. Although ground units are involved in far more crashes than their air counterparts, air incidents are more likely to involve fatalities. Based on data from the National Highway Traffic Safety Administration, approximately 2% of ground ambulance accidents result in fatalities, while upward of 20% of HEMS crashes end with at least one death.
Most safety issues are related to weather, obstacles, night flying, and mechanical problems. Each of these is mitigated using multiple strategies, with a key emphasis on crew resource management and communication. Standard strategies include shift safety briefings, preflight checklists, utilizing pre-selected landing zones, weather prediction models and radar, scheduled maintenance, and crash avoidance technology on the aircraft. Flight services often follow the best practices rule of “3 to go, 1 to say no”, wherein all crew members including pilot(s) and medical team must agree that the mission falls within predefined safety parameters, and any crew member can abort the flight for any reason, and the flight will be canceled, no questions asked. It is also an accepted best practice to withhold patient acuity information from the pilot until after the accept/reject mission decision has been made, to not bias the pilot’s decision regarding safety.
With that in mind, requesting air transportation for patients should not be based on the requestor’s perceived safety risk; rather, the other advantages and disadvantages of flight medicine should be weighed, and the decision regarding mode of transportation should be based on what is best for patient care. The decision regarding mode of transportation is usually left to the requesting medical provider. The aircraft crews and program management are in the best position to decide how to mitigate the risks of using their aircraft, and safety decisions should be left to these experts.
Aircraft pose other risks to providers related to stressors that are specific to flying. These include noise, vibration, rapid temperature changes, and possible dehydration, all of which can lead to adverse sequelae if not managed appropriately. Hearing protection equipment is standard, and many programs have implemented fatigue recognition and management strategies to assist crews with these issues. Flight crew positions are often very coveted given their prestige, compensation, and schedule. However, the job can be very stressful, and caution must be taken to ensure crew members do not suffer from burnout.
There are several organizational and staffing models in use in the United States. The traditional flight program model is organized around a hospital or healthcare group, and flight crew members are hospital employees. Aviation staff members, including mechanics and pilots, are usually employed/supplied by a contractor. A community model is different in that the aviation contractor provides the medical and aviation staff, and is often utilized by private, for-profit aeromedical groups that may or may not be affiliated with a hospital or EMS agency. Hybrid programs also exist, wherein the aviation company contracts with a hospital to provide hospital employees as the medical crew for a privately held aircraft. In rare circumstances, public service agencies may own and provide staffing for aeromedical services. These aircraft often serve in multiple roles, including law enforcement and search and rescue.
Staffing models also vary widely, depending on mission profile, local needs, EMS regulations, and other factors. The typical flight medical crew has two providers though there are programs that include a third team member. Rarely, programs have a single medical crew member assigned to the aircraft. Crew configurations also vary, with the most common team composed of a nurse and paramedic. Less common configurations include nurse/nurse, paramedic/paramedic, nurse/respiratory therapist, and combinations that include a flight physician.
The regulation of emergency medical services is typically overseen at the state government level. However, since the passage of the Airline Deregulation Act of 1978, the ability of states to manage air medical transportation has been severely limited. While it is generally accepted that the EMS personnel and patient care protocols used on aircraft are subject to state oversight, state and local government attempts to regulate decisions regarding type and placement of aircraft, staffing, equipment, and response have been successfully challenged in federal court. While discussions regarding specific regulations are beyond the scope of this chapter, important Federal Aviation Administration (FAA) regulations for aeromedicine include Part 91, and all EMS aircraft must hold Part 135 certification.
The use of rotor-wing transportation is often very expensive. Similar to ground units, there are fixed and variable operating costs to consider. Aircraft are more expensive to purchase and maintain. Combining very high fixed costs with a relatively low call volume and higher fuel prices makes the cost per transport extremely high in many cases. Patient charges are dependent on many factors, including operating costs and market forces. Unlike ground ambulances, there is no federal fee schedule or standard for reimbursement for air medical services, which allows providers to charge patients thousands (sometimes tens of thousands) of dollars more than a typical ground ambulance transport. There is significant debate regarding these charges and the handling of charges above what is reimbursed by insurers. However, it is important to understand that mileage becomes the main factor involved in ground ambulance fees for distances over 30 miles, and it is distinctly possible that air transportation, especially by fixed-wing aircraft, may be cheaper for greater distances.
Aircraft form an important part of EMS systems of care, especially between outlying communities and tertiary/quaternary referral centers. This is most often due to the rapid speed and greater distance that can be covered by rotor- and fixed-wing ambulances. The usual distance range of a rotor-wing asset is 150 to 200 miles, with maximum speeds of 100 to 180 mph; for fixed-wing aircraft, it is very dependent on the type of aircraft and fuel capacity, with ranges over 500 miles at speeds between 200 to 300 mph. The airspeeds of these aircraft easily exceed those of ground units, especially when considering ground traffic. However, all aircraft require a warmup time (generally 5 to 10 minutes for HEMS, longer for airplanes) and are usually farther away from the patient than a local ground unit. Runway requirements for takeoff and landing further restrict airplanes, and the patient will usually need one or more transfers involving a ground unit to move them to/from the runway/airport. This limitation may be offset by de-icing capabilities and the less restrictive weather minimums of fixed-wing aircraft. When considering the potential time savings of using aeromedical assets, the caregiver must carefully account for these and other factors. It is also possible that the need for uninterrupted continuous critical care will outweigh a longer transport time. Note that each aircraft and aeromedical program has strengths and weaknesses, and mission requirements should dictate the decision regarding flight.
Aeromedical transportation is used in many different scenarios including scene response, interfacility transfers, delivering specialty care, and repatriation. While this is not an exhaustive list, it includes the most common mission types with each discussed briefly below.
When citizens living or traveling abroad desire to return home for their medical care, this is termed Medical repatriation. These flights are not uncommon. However, no single organization tracks these numbers making detailed analysis difficult. These missions can be for unexpected emergencies while away, or for scheduled or urgent specialty care that may not be available in some foreign countries. While repatriation is often accomplished via commercial airlines, patients needing constant medical attendance and monitoring will often require fixed-wing aeromedical transport. Most repatriation flights do not require critical care resources though some countries require a physician on board. These flights are often elective, and may not be covered unless the patient has separate trip insurance that includes a repatriation rider. The rules and regulations regarding international medical flights can be complex and depend on which jurisdictions are involved.
As regional systems of specialty care continue to develop, transferring patients from outlying community hospitals to regional referral centers becomes more and more common. Many conditions requiring specialty care are time-dependent, including cardiac, stroke, and trauma care. Transferring patients between medical facilities poses specific medical and legal implications. Notably, EMTALA will likely apply, and it is important for sending and receiving physicians to understand their obligations under that law. The sending physician must stabilize the patient to the best capability of that hospital before the transfer. That physician is also ultimately responsible for choosing the mode of transportation, level of care to be provided during the transfer, and treatment orders if needed or requested.
The use of aircraft to respond to emergency scenes is termed primary air transport, and is very dependent on geography and the local EMS system. Distance, traffic patterns, and time to definitive care are usually the most important considerations for the ground crews deciding to call for an air ambulance. There are many areas in the United States that require aircraft to be able to respond to an emergency quickly and effectively. While only 19% of the US population lives in a rural area, over 50% of fatal motor vehicle crashes occur there. Additionally, many terrains may necessitate flight retrieval including mountains, islands, ships, and offshore drilling sites. For many localities, aircraft provide support to ground units on an as-needed basis. Emergency department closures and a reduction in the number of level I and II trauma centers nationwide has also fueled growth in aeromedical flights. Trauma scene calls are common, with HEMS responding at the request of the local EMS agency to reduce the time needed to transport the patient to a trauma center. Acute strokes and patients with STEMI are also sometimes flown from a scene if the EMS responders think it will provide significant time savings to a stroke center or cardiac catheterization lab. This is much more common in rural areas where ground transportation may take an hour or more to get the patient to the cardiac catheterization lab or thrombolytics.
Specialty care services are often limited by availability because it is often cost prohibitive to equip and staff every ground unit in a system with special equipment and subject matter experts. For example, neonatal critical care teams are relatively uncommon, so centralizing a team and using an aircraft to get them quickly to outlying areas and hospitals make the most sense. This strategy is sometimes employed for taking physician specialists to remote areas during a time-sensitive emergency, such as transporting a trauma surgeon to the scene of an entrapped patient for performing a limb amputation. In many systems, the crews and equipment on air assets represent the highest level of out-of-hospital care available in the region. Patient transfers involving an intra-aortic balloon pump (IABP), extracorporeal membrane oxygenation (ECMO), resuscitative endovascular balloon occlusion of the aorta (REBOA), and other very advanced devices are often best served by a flight team who has the requisite training and experience to manage these complex technologies and their potential complications.
Common indications for aircraft utilization include surgical emergencies, conditions requiring emergency coronary intervention, and acute strokes. Several organizations have provided guidance on the indications for EMS aircraft utilization, including the Air Medical Physicians Association (AMPA), the National Association of EMS Physicians (NAEMSP), and the American College of Surgeons Committee on Trauma (ACS COT). Below is a representative list of medical and trauma indications, which is not necessarily exhaustive.
Using aircraft for these or other issues is best handled based on a predetermined plan rather than ad hoc decision-making. Preplanning improves consistency and provides additional safety for responding crews. This can include written indications and contraindications for flights, predetermined landing zones (and how to set up ad hoc LZs when necessary), communication plans, and shared protocols.
There are very few absolute contraindications to using aeromedical transportation. Weather is usually the limiting factor and can include issues with visibility, cloud ceiling, precipitation, wind, and temperature. The decision to fly or not should lie solely with the aircraft crew. Prelaunch weather checks, including weather prediction, are completed before accepting a flight mission, with FAA minimums setting absolute rules governing these flights. Patient weight and girth may also be a contraindication to flight, though this is dependent on the type of aircraft and the crew configuration. The pilot must use an accurate patient weight combined with current and predicted fuel levels, weather, and crew weight to determine if it is safe to fly. Again, this accept/deny mission decision is made by the aircraft crew. It is never appropriate to try and circumvent weather or safety-related flight turndowns. The practice of calling a different flight program after another rejects a mission due to weather concerns is known as “helicopter shopping.” The FAA officially discourages this practice though no written regulation exists.
Certain types of patients may create a risk for the aircraft. Flying uncontrolled violent patients is an absolute contraindication though this can potentially be mitigated with sedation and restraints. Flights involving a prisoner are not necessarily contraindicated. However, most services will refuse these flights because they require an armed prison guard to be aboard the aircraft. Patients contaminated by hazardous materials should not be allowed on any aircraft until they are decontaminated, as the fumes may affect the pilot’s ability to fly safely and may render the aircraft unavailable for additional flights for an extended period.
Relative contraindications are based on the ability of the crew to manage the patient and expected complications in a space that allows for little movement and limited patient access. Most specifically to HEMS, the patient is often situated in such a way that performing procedures below the waist is difficult to impossible. This precludes taking care of pregnant patients with imminent delivery as visualizing the perineum and safely delivering a newborn would be nearly impossible. This does not necessarily mean that pregnant patients cannot be flown in aircraft, but the requesting team and the flight crew must assess the likelihood of delivery in flight and perform an educated risk/benefit analysis before taking off. Examples of potentially appropriate pregnancy-related transfers are severe pre-eclampsia and eclampsia, fetal hydrops, and surgical emergencies with a fetus of less than 34 weeks gestation. The benefits of transferring premature labor with an estimated gestational age of fewer than 34 weeks may outweigh the risks if the sending facility (or potentially the EMS crew on the scene) is ill-equipped to handle the premature delivery.
Another difficult to manage scenario is a patient who is in extremis or cardiac arrest. Unless the aircraft has access to a mechanical CPR device, continuous high-performance CPR is realistically impossible in most rotor-wing ambulances. Manual CPR would also require at least one of the providers to remain unbelted in flight, posing a potential danger to the crew and patient. Since CPR is one of the most important procedures for a patient in cardiopulmonary arrest, most flight crews will decline these missions unless they are equipped with a mechanical CPR device. Given the high acuity of patients transported by air, especially HEMS, providers should prepare in advance for patients who decompensate and go into cardiac arrest. The NAEMSP recommend that BLS flight crews divert to the closest hospital and ALS crews consider the risks and benefits of diverting versus returning to the facility of origin if applicable. Preplanning for these and similar events will help to reduce stress on the crew so they can focus on patient care instead of destination decisions.
Less commonly, patients may have a medical condition or device that may be adversely affected by altitude changes. This is more of a concern for fixed-wing aircraft, as helicopters are usually flying at less than 2000 feet and so are unlikely to cause significant physiologic alterations. Most fixed-wing aircraft do pressurize the patient compartment. However, pressurization is often set to 8000 to 10,000 feet. Disease states that can be negatively impacted by altitude changes include pneumothoraces and barotrauma (decompression sickness). Air-filled devices, such as endotracheal balloons, can swell with increasing altitude, and consideration should be made toward filling them with saline instead of air to counteract this problem. The use of air splints in flight is also potentially problematic, and these devices should be deflated or removed before flight.
In addition to utilizing pre-arranged agreements and obtaining acceptance from a receiving physician, the most important preparation step for interfacility transfers is adequately stabilizing the patient. This should include performing any invasive procedures that the patient needs immediately or could be anticipated to need during the transfer. As mentioned earlier, it can be difficult to perform many procedures after the helicopter lifts off. Airplanes are typically less restricted in this manner but will often have multiple transfers that take a significant amount of time, meaning the sending provider must anticipate farther into the future. Providing an accurate weight and anticipated needs (ventilator, the number of drips, the presence of a family member, among others) can be very helpful to the incoming flight crew.
The most important steps of scene preparation for flight operations are choosing a safe landing zone and communicating the location of any hazards that may present a danger to the aircraft. These situations generally involve HEMS, as most airplanes require a dedicated landing strip. Recommendations for landing zones include a minimum 100 feet by 100 feet flat area that can be secured and avoids flying debris from rotor wash. Minimizing and communicating hazards such as overhead power lines, trees, cell towers, and cranes, and direct radio communication between the pilot and landing zone team are paramount to crew safety. Ideally, GPS coordinates should be supplied. Additional helpful information includes patient weight, type of call, need for specialty resources, and how the landing zone will be marked. Again, it is ideal to have pre-established landing zones, even for scene flights. The use of a hospital landing pad as a rendezvous point for ground and air EMS units is a legitimate strategy for maximizing flight safety and does not trigger EMTALA unless the patient or EMS crew specifically asks for hospital assistance. In those instances, the hospital staff should be instructed to stay clear of the area and not interfere with the patient transfer unless asked to assist.
In the event that multiple aircraft are requested to a scene (or to a hospital), all agencies must be explicitly told of all other responding aircraft to help prevent a mid-air collision. Most localities have no air-traffic controller responsible for medical aircraft, and the pilots need to know to communicate with each other to avoid disaster.
Aeromedical transportation services in the United States require physician medical direction. These doctors are responsible for supervising all aspects of the medical care provided by the medical crew and must have final authority over all clinical aspects of care. Most medical directors have a background in emergency medicine, though this is not always necessary. The requirements for medical directors vary based on state regulations and organizational policies. The NAEMSP position statement on the topic has over 30 recommendations regarding requisite knowledge and duties of medical directors for flight programs. The recommendations include knowledge of applicable laws, ground EMS, advanced resuscitation, effects of altitude, safety, dispatching, disaster management, and adult education. The medical director should approve all operational protocols, safety procedures, and biomedical equipment in addition to participating in the initial and continuing education of all air medical personnel.
Physician presence as part of the flight crew is relatively rare in the United States but is often the standard internationally. These physicians can offer real-time medical direction in addition to an expanded skill set. For crews without a flight physician, real-time medical direction can be challenging as communication via cell phones is often prohibited in flight, making protocols and training even more important.
Aeromedical programs are charged with providing regional education regarding indications for flight requests, landing zone preparation, aircraft safety, and other perceived needs. Programs should also participate in regional trauma and medical care groups and track statistics regarding outcomes and overtriage rates. Proactive integration into EMS systems of care is highly encouraged. The medical director plays a key role in forging and maintaining these various relationships.
There is limited evidence regarding the outcomes of aeromedical versus ground transport. It would be difficult, perhaps impossible, to conduct randomized controlled trials comparing air and ground EMS care. As a result, most studies are retrospective and suffer from significant selection bias. Many studies do demonstrate higher skill success for aeromedical crews, especially with advanced airways and RSI. Research that examines patient-oriented outcomes is rare. However, there is a trend towards morbidity and mortality benefit of HEMS in time-critical trauma cases. It is generally accepted that there are many patients who are not sick enough or are too sick and cannot benefit from aeromedical transportation. Thus, the exact benefit of air transportation remains largely undefined.