EMS Air Medical Transport

Issues of Concern

Advantages and Disadvantages

Air medical transport offers several advantages over ground transport, including greater speed and maneuverability. Road availability, road conditions, and traffic limit ground transport. Ground transport also travels much more slowly than air transport, especially compared with fixed-wing aircraft. However, air transport also has disadvantages. These disadvantages may be common to both fixed-wing and rotor-wing aircraft, or specific to each type. Common disadvantages include higher costs, which depend on factors such as staffing, aircraft type, and transport distance. Operating air medical transport is also very expensive because the aircraft itself can cost several million dollars, and maintenance is strictly regulated. Air transport is more susceptible to weather conditions than ground transport, especially in rotor-wing aircraft. Weight must also be carefully calculated because the engines can only produce a finite amount of power. An overweight aircraft can end in disaster.

Safety

Another disadvantage of air medical transport is that it is inherently more dangerous than ground transport, especially by helicopter. No specific data directly compares air transport to ground transport. However, some studies examine each mode individually. Between 1992 and 2011, there were approximately 4500 ambulance accidents. Of these accidents, 29 resulted in fatal injuries. In the 10 years between 1998 and 2008, there were 146 helicopter accidents, and of these, 50 (34%) resulted in fatal injuries. This suggests that air transport accidents are more likely to be fatal than ground accidents. The percentage of fatal accidents is roughly the same in fixed-wing accidents as well.

Characteristics of Air Medical Transport

Aircraft can have a single engine or multiple engines. Helicopters typically have either 1 or 2 engines. With 2 engines, a helicopter can carry more weight and travel faster. However, they also consume more fuel, which increases the cost. They also cost more for maintenance. Airplanes usually have more than one engine because typical single-engine airplanes are not big or powerful enough to transport a patient, the crew, and required equipment. Multiple engines also add a safety factor, since 1 engine can malfunction and the aircraft still has a working engine to land safely.

Helicopters are ideal for transporting critical trauma patients because they are more effective in decreasing the time of transport to a trauma hospital. This is important because, for many critical trauma patients, the most important factor in decreasing mortality is getting them quickly to an operating room with a trauma surgeon. Patients have to be considered a critical trauma patient (often called a “trauma alert”) for consideration of helicopter transport. The following is an example of adult trauma alert criteria used by Holmes Regional Medical Center in Melbourne, Florida.

One of the following:

• Active airway assistance required beyond administration of oxygen
• Heart rate greater than 120 without radial pulses
• Systolic blood pressure less than 90
• Best motor response less than or equal to 4, or a total Glasgow Coma Scale less than or equal to 12
• Second or third-degree burns on greater than or equal to 15% of body
• Amputation proximal to wrist or ankle
• Penetrating injury to head, neck, or torso excluding superficial wounds where the depth of the wound can be determined
• Two or more long-bone fracture sites (humerus, radius/ulna, femur, tibia/fibula)
• Paralysis, loss of sensation, or suspected spinal cord injury
• Judgment of EMT, paramedic, or another healthcare provider

Two of the following:

• Respiratory rate greater than or equal to 30
• Sustained heart rate greater than or equal to 120
• GlasgowComa Scalee best motor response equal to 5
• Major degloving injury or flap avulsion greater than or equal to 5 inches
• Gunshot wound to the extremity
• One long-bone fracture from a motor vehicle collision or fall greater than or equal to 10 feet
• Ejected or thrown from any vehicle (including ATV, motorcycle, moped, or truck bed)
• Steering wheel deformity

Helicopters can land close to the scene of the incident, often landing on roads or open fields. These landing areas usually must be at least 100 feet by 100 feet and relatively flat and free of debris. First responders will often mark the area for the helicopter crew and provide security to keep bystanders from approaching the landing area. Ground crews need training in landing zone safety so they do not put themselves or the helicopter crew in danger by being struck by the main rotor or tail rotor. Helicopter crews are trained on exiting and entering the aircraft on scene, which usually requires pilot approval. This can occur with the aircraft shut down or with the rotors turning, which is called a hot load or hot offload. The pilot has the final say on if the landing zone is safe for landing. Many obstacles can create a safety hazard, such as proximity to power lines, crowds of people, or the type of landing surface. Landing in a muddy field can cause the landing gear or skids to sink, making it difficult to take off. Loose objects or debris can also be a hazard because the main rotor's downwash can blow them into the air, where they can be sucked into the rotor blades and/or engines.

Helicopters can also be utilized to transfer patients from one hospital to another. This is usually because the patient needs to be transferred to a specialized care service which is not available at the sending hospital. Examples include a burn center, cardiac cath lab, or an intensive care unit. Hospitals usually have a landing pad for helicopters, which are generally safer than landing at a scene. Helicopter landing pads are placed in a safe area away from buildings or power lines, are flat and made of solid materials such as concrete, and have appropriate markings and lighting. Landing pads can also be placed on rooftops. Landing pads are such an ideal landing surface that patients from a scene will sometimes be transported by ambulance to the closest landing pad if a suitable area cannot be found near the scene.

Weather conditions are an important consideration for air medical transport. Helicopters are susceptible to severe weather, such as strong winds or heavy snowfall. Another important weather factor is visibility. Pilots follow regulations called Visual Flight Rules (VFR) or Instrument Flight Rules (IFR), set by the Federal Aviation Administration. Helicopters operating under VFR must have clear visibility of several miles, depending on altitude and aircraft type. For example,s helicopters operating during the day below 1200 feet must have one mile of visibility. This allows the pilot to see and avoid other aircraft or structures such as towers. Airplanes also operate under VFR, but since they are faster and operate at higher altitudes than helicopters, they have increased visibility requirements, up to five miles. VFR also requires aircraft to maintain a minimum clearance from clouds: 500 feet below, 1000 feet above, and 2000 feet horizontally.

If an aircraft flies outside the minimum VFR requirements, it must fly under Instrument Flight Rules. This is considered flying “in the clouds.” To be certified to fly IFR, aircraft must have specific equipment, including several navigational aids. Pilots must also have special training because it can be difficult to navigate using instruments alone without an outside reference for spatial orientation. Aircraft also can only land at places with an Instrument Landing System, which is usually only at airports. This means that helicopters cannot land at a scene or landing pad using IFR. Some medical transport helicopters are not equipped to fly in IFR. Because of this restriction, medical transport helicopters often cannot accept flights in poor visibility.

Airplanes also have special considerations. The most obvious being that they require a runway for takeoff and landings. The exception is a seaplane, which requires a large body of water. This requires the patient to be transported by ground to the airport, and then again picked up at the destination airport for transport to the final medical facility. Airplanes have a longer range than helicopters. Because of this, airplanes are usually used when a patient must be transported a long distance, for example, between countries. Airplanes can also travel much faster than helicopters.

Another consideration for both fixed- and rotor-wing aircraft is physiologic changes due to altitude. Boyle’s law states that a gas's volume increases when pressure decreases at a constant temperature. As an aircraft ascends, surrounding atmospheric pressure decreases proportionally. At sea level, atmospheric pressure is 14.7 pounds per square inch (psi) (101 kPa). At 10,000 feet, it is 10.1 psi. This means that as an aircraft ascends, gases on board expand. For example, a patient with a pneumothorax could have an increase in size if they do not have a properly functioning tube thoracostomy. Another issue to consider is equipment with gas-filled cuffs, such as endotracheal tubes. If the cuff volume is allowed to expand, it could damage the trachea, including pressure necrosis. Airplanes are more susceptible to altitude-related problems since they travel at higher altitudes. However, they have pressurized cabins which help correct these problems. Helicopters are still susceptible to altitude-related issues since even at an elevation of 1500 feet, atmospheric pressure decreases to 13.9 psi.

Air medical transport crews vary in type and size. They may have one or two pilots, and medical personnel may include a combination of nurses, paramedics, physicians, or respiratory therapists. These crews must have specialized training, including a course on Air Medical Resource Management. This management system makes optimal use of all available resources to ensure safe, efficient operations. The goal is to reduce unfavorable events caused by human error. Crews may also have other training specific to the equipment on their aircraft, such as night vision goggles. Medical personnel sometimes have an expanded scope of practice. For example, paramedics or nurses may be able to place chest tubes. This is often necessary to effectively treat patients who are far from the definitive care they may need. Medical personnel must be very proficient in all aspects of their scope of practice since almost all of their patients are high acuity.

Clinical Significance

The decision to use air medical transport has many considerations. Ultimately, will helicopter or airplane transport benefit the patient? While aircraft can travel much faster than ground transportation, time is lost setting up a landing zone (or transporting to an airport) and for the flight crew to evaluate the patient. Would ground transportation take a comparable amount of time to “load and go”? Also, would the patient’s condition be better served by a higher level of care or a greater scope of practice that the air medical transport crew might provide? The benefits have to be weighed against the risks.[6][7][8][9]