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Air and ground transports are not without risk. King and Woodward published a 5-year review of accidents involving pediatric and neonatal transports in 2002 and found that accident rates were approximately 1 per 1000 transports, accidents rates where an injury was sustained were 0.546 per 1000 accidents, and all eight fatalities occurred with air transports.9 According to the National Transportation Safety Board (NTSB), accident rates and the number of flight hours have increased substantially since this study was concluded.
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Safety considerations should be part of a team's initial and continuing training. Transport personnel must be familiar with safety features of the various transport vehicles in which they will be traveling. Policies and procedures should specifically address safety considerations, including considering weather, use of lights and sirens on the ambulance, use of restraints, weight limitations for flight, and vehicular maintenance. In the case of hazardous weather conditions, the final decision as to safety of travel should reside with the pilot or driver of the transport vehicle, and should be supported by the transport medical director, erring on the side of caution for patient and personnel safety.
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Personal protective equipment is important to protect the team members. The NTSB has stated that “helmets, flame-and-heat-resistant uniforms, and protective footwear can help reduce or prevent injury” in accidents.10 Appropriate universal infectious disease precautions should be undertaken when dealing with all patients, not just those patients with known infections or who are bleeding. Gowns, gloves, and masks should be used whenever appropriate and possible, and transport policies should mirror the institutional-based policies in the case of accidental needle stick injuries or exposure to blood and/or body fluids.
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It is important to provide appropriate equipment to personnel to prevent injury when lifting patients. Much media attention has focused on the growing problem of obesity in children and equipment such as hydraulic stretchers should be available to the teams to minimize back injuries. Policies and procedures are necessary to protect the teams from disruptive patients and parents, including addressing the possession of firearms and knives by family members. Psychiatric patients require special consideration, such as the need for restraint.
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Medical Safety Issues and Altitude Physiology
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There are multiple medical stresses that need to be taken into consideration when transporting critically ill and injured children by air. Stresses of flight affect both the patient and crew members. These include changes in barometric pressure, hypoxia, temperature, dehydration, noise, vibration, g-forces, third spacing, and fatigue. Teams may suffer visual problems and spatial disorientation, particularly when flying at night. Teams and patients also need protection from potential toxic hazards in the air medical transport environment (Table 148-4).11
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Changes in barometric pressure and hypoxia are perhaps the most significant stressor to the patient and crew. During ascent, the barometric pressure falls unless it is controlled by the aircraft. Boyle's law states that the volume of a gas is inversely proportional to its pressure, when temperature is constant; therefore, as barometric pressure is reduced, gases expand. At 8000 ft, which is effective cabin altitude for most pressurized aircraft, gas expansion is approximately 30% greater than at sea level. This can result in a small clinically insignificant pneumothorax becoming a life-threatening tension pneumothorax during flight. Air in other body cavities can also expand. In the brain this can lead to intracranial hypertension. Air in the stomach can cause nausea and vomiting and gastric distension that can interfere with lung expansion. In the middle ear, it can cause significant pain if the eustachian tube is blocked. Air in endotrachial (ET) tube cuffs can expand, resulting in compressive forces on the inner trachea. Thus, preventive measures are undertaken to minimize the risk of gas expansion. Pneumothoraxes are drained prior to flight, nasogastric tubes inserted to decompress the stomach, and cuff pressures on ET tubes are monitored and decompressed as necessary. If a child is awake, he or she should be encouraged to suck on a pacifier and/or chew on descent. The aircraft should ascend and descend slowly, or fly at a lower altitude. A team member with a significant upper respiratory infection or blocked eustachian tube may not be able to participate in an air transport. Another medical implication of altitude is the fact that the amount of gas dissolved in solution is directly proportional to the pressure of the gas over the solution (Henry's law). As barometric pressure falls with altitude, less gas is dissolved in solution, so there is less oxygen dissolved in blood and the child can become hypoxic just by the change in altitude. At sea level, the percentage oxygen saturation in room air is 98%; at 8000 ft, this saturation falls to 93% based on barometric pressure alone. This has implications for patients who are already hypoxic or are very sensitive to oxygen content in the blood, such as children with pulmonary hypertension. Therefore, oxygen administration may be increased prior to ascent, or consideration may be given to flying at lower altitude.
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As altitude increases the air cools and humidity drops. For each 1000-ft gain in altitude there is a 2°C drop in temperature. Ambient humidity in a pressurized aircraft after 1 hour of flying is <5%. Pumping additional gas into an airplane may cause the environment to be cooler and dryer. Patients and team members need warm, light clothing. Temperature and hydration are monitored, particularly with neonates who are already more vulnerable to cold. Using a hat will reduce up to 60% of radiated heat loss. Transporting an infant in an isolette is also protective. Teams and patients may need to wear ear protection to protect against noise stress, as damage to hearing from noise-induced causes is permanent. Hearing tests should be administered annually to transport team members who fly. Vibration and g-forces may cause nausea and fatigue and should be minimized where possible (Table 148-5).11
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