Author: Jamie Aranda, MD, Medical College of Wisconsin
Editor: Jonathan Fisher, MD, Maricopa Medical Center
- Describe the structure of an aeromedical emergency medical services (AEMS) system
- Recognize the advantages and disadvantages of aeromedical services
- Determine patients who may benefit from aeromedical transport
- Understand how basic concepts of flight physiology may impact care
- Understand the roles of the transferring physician and AEMS crew in aeromedical transport
- Identify safety themes pertinent to aeromedical transport
Prehospital and interhospital transport of critically ill patients play an important role in providing access to tertiary and specialty care facilities. The time-sensitive nature and high level of care required by these patients make aeromedical services a key component of emergency medicine and Emergency Medical Services (EMS). Certain patient populations may specifically benefit from aeromedical transport, and determining which patients are appropriate for transport is often the responsibility of the emergency physician (EP). Therefore a basic understanding of aeromedical systems, patient selection and flight physiology is imperative.
Aeromedical services and crew
Aeromedical transport systems may include rotary wing (helicopter) or fixed-wing (airplane) aircraft. In addition, crew may be responsible for ground transport (ambulance) to and from the hospital, airport or helipad. Therefore, they must be familiar with aircraft safety and be able to function within various transport vehicles in their system. Like any EMS system, aeromedical crew operate under indirect medical control using protocols and standing orders. However, there may be a higher level of direct or on-line medical control amongst aeromedical services where the medical staff speak directly with a physician providing medical direction. There are no universal regulations regarding crew composition and this varies between region and EMS system. In addition to a pilot, the crew usually consists of at least two members and may be any combination of the following:
- Respiratory therapist
Helicopter responding to scene call.
Courtesy of Tim Snopek, used with permission by Flight for Life Emergency Medical Air Transport.
Advantages of aeromedical transport
- Provide critical care: Candidates for aeromedical transport are critically-ill medical or trauma patients requiring tertiary or specialty services not immediately available in their region and are often at risk of decompensation. Therefore, aeromedical crews must provide critical care – care that exceeds the scope of a paramedic as defined by the National Highway Traffic Safety Administration’s (NHTSA) National EMS Scope of Practice Model. This definition is broad and in addition to EKG interpretation, pacing, defibrillation, intubation, cricothyrotomy, and needle thoracostomy may include titration of drips, ventilator management, pericardiocentesis, umbilical vein catheterization, etc. By comparison, ground transport crews typically are designated basic life support (BLS), advanced life support (ALS) or critical care (CC) capable.
- Decreased transport time: Total time to patient arrival may not actually be shorter (due to travel to airport or helipad, or collection of crew members, equipment or blood products from a facility), the amount of time the patient spends in transit is decreased due to increased speeds of air transport. This becomes particularly important in the critically ill patient and has an increased benefit the further the patient needs to travel. Additionally, aeromedical EMS may bring advanced care to the patient sooner.
- Scene calls: Helicopters have the advantage of being able to respond to scene calls. This is relevant in the trauma patient, individuals in remote locations isolated from ground access, and some urban centers where traffic limits rapid transit via ambulance. Medical crews thus may be required to carry special equipment (including cold-weather gear) and be prepared to perform procedures outdoors and in austere environments.
Disadvantages of aeromedical transport
- Cost: Typical flight costs between $12,000 to $25,000 per flight but can be as high as $50,000 or more depending on distance and services provided. The initial cost of purchasing and equipping a helicopter for use as an ambulance is between $4 and $8 million with annual operating costs of $1.5 to $2 million dollars. Costs may include facility and aircraft maintenance, fuel, crew and support staff compensation, medical equipment purchase and maintenance, marketing and education. Insurance covers many of these transports if deemed medically necessary, but sometimes these bills have led to medical bankruptcy for patients.
- Physical limitations: The weight of fuel and passengers (including increasingly overweight and obese patients) place constraints on the catchment area. Loud noise and space limitation also pose challenges to medical crew in providing care.
- Weather and safety concerns: Helicopters, in particular are limited by weather conditions. There has been a great deal of scrutiny surrounding safety of helicopter transport given a number of high-profile crashes in recent years. Fixed-wing aircraft have a better safety profile, can carry more equipment and can travel longer distances. However, they are not ideal for short transits as they require an additional transport to and from an airport and cannot be used for scene calls.
Several retrospective studies have compared cost-effectiveness and outcomes in aeromedical transport with ground EMS systems and have identified select patient populations that may benefit. The following table lists the most common diagnoses:
|Patient Diagnosis||Reason for Transfer|
|Multisystem trauma||Increased survival benefit when directly transported to a Level I or Level II trauma center|
|Burn injury||Patients meeting burn center referral criteria should be transferred to a burn center to improve survival and function|
|Myocardial infarction||Patients with ST-elevation myocardial infarction (STEMI) and select cardiac diagnoses should be transferred to facilities capable of percutaneous intervention for revascularization within 90 minutes|
|Decompensated heart failure||Need for multidisciplinary care including cardiology, electrophysiology, cardiothoracic surgery. These patients may require in-flight management of a ventricular assist device, an intra-aortic balloon pump or extracorporeal membrane oxygenation (ECMO)|
|Stroke||Both ischemic and hemorrhagic stroke victims should be transferred to comprehensive stroke centers due to the potential need for tPA (ischemic only) neurovascular or neurosurgical intervention, intubation and monitoring of neurologic function|
|Patients with sepsis may need transfer to a hospital with an intensive care unit capable of initiating early goal directed therapy|
|Pediatric or Neonatal Patient||Critical care teams consisting of specially trained personnel and transport equipment often exist in partnership with pediatric specialty hospitals|
|Trauma Center Levels*|
|Level I||Full-capability Emergency Department (ED), 24-hour in-house general surgery with prompt availability of specialty care|
|Level II||Full-capability ED, 24-hour in-house general surgery with prompt specialty care in some areas|
|Level III||Full-capability ED, prompt availability of general surgery and anesthesiology|
|Level IV||Basic ED capable of implementing ATLS and 24-hour laboratory coverage|
|*For simplicity, this table does not define annual volume or additional trauma center requirements such as injury prevention, education, research, quality assessment, substance abuse screening and intervention components of the Trauma Center Designation and Verification process.|
Physiology and Special Considerations
There are a number of special considerations regarding flight physiology and physical space limitations. In accordance with Boyle’s law, the decreased atmospheric pressure at altitude allows air-filled spaces to expand. Therefore, patients with pneumothoraces may require chest tube prior to transport even if stable at the transferring facility. Endotracheal tube cuffs may need decompression to prevent tissue necrosis. Combative patients and those at high risk of respiratory or neurologic deterioration should be intubated prior to transport in order to avoid the need for an emergent airway while in-flight. Combative patients are not appropriate for transport unless chemically and/or physically restrained due to safety risk in an enclosed space.
Interior of helicopter.
Courtesy of Tammy Chatman, used with permission by Flight for Life Emergency Medical Air Transport.
Role of the Transferring Physician in Aeromedical Transport
Transferring physicians should be familiar with the capabilities and transit times of their local EMS systems and the indications for transfer to specialized centers within their region. The EP is tasked with recognizing patients with time-sensitive, high-acuity conditions that require specialty services and is responsible for transferring those patients to an appropriate facility. Under the Emergency Medical Treatment and Active Labor Act of 1986, it is important the EP communicate clearly to the accepting institution, obtain an accepting physician, obtain informed patient consent, and determine the appropriate mode of transport. If aeromedical transport is anticipated, the EP must stabilize the patient and perform any procedures (such as central line placement, intubation, tube thoracostomy) that may be required prior to transport in order to ensure a safe and efficient transfer.
Occasionally, the aeromedical crew may offer services (depending on procedures and protocols) to the transferring physician to help prepare the patient for transfer. However, these procedures fall under the supervision of the medical director and should not go beyond the scope of practice of the crewmember. On-line medical control is often available for consultation in challenging situations. Crew should obtain a report from the transferring physician including any documentation or results (imaging discs) necessary for further medical decision-making. Upon arrival at the receiving facility, the crew give a detailed report to the accepting physician of the patient diagnostics and condition prior to transport, any interventions performed or data obtained en route (including pertinent vital signs), and a current status report. It is customary for the medical crew to provide an update of safe arrival to the family or caregiver if the patient desires (in compliance with HIPAA, the Health Insurance Portability and Accountability Act of 1996).
Given the high-risk nature of aeromedical transport, a culture of safety is imperative for the success of any AEMS system. Most programs use the guiding principle, “three to say ‘go’, one to say ‘no!’” in reference to the low threshold for turning down transports in the setting of potential hazard such as unsafe weather conditions. Some programs utilize “blinding” in that the pilot and crew prepare and determine whether conditions are appropriate prior to receiving the patient report in order to avoid bias; i.e. in the setting of a pediatric transport that may bias the crew towards transport. AEMS programs are encouraged but not required to be evaluated by CAMTS, the Commission on Accreditation of Medical Transport Systems.
Aeromedical transport plays an important role in EMS and is a rewarding career choice. AEMS systems may consist of rotary wing or fixed-wing aircraft. Crews vary on region and system, but must consist of highly trained personnel capable of delivering critical care in both cramped and potentially austere environments. EPs should be familiar with local EMS capabilities, specialty services and availability at receiving hospitals and the risks and benefits of aeromedical transport. EPs should employ a basic understanding of flight physiology and safety parameters and use this information to select which patients benefit from transport and which stabilizing interventions should be performed prior to transfer.
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