http://www.usairambulance.net/effects-of-altitude.php

The Effects of Altitude

Even in pressurized aircraft, the air medical environment presents unique stresses on our patients. These stresses include immobility, noise, motion, vibration, hypoxemia, decreased humidity, gravity, and decreased barometric pressure with subsequent air expansion. To assure that our patients are transported as safely and comfortably as possible, the following protocols apply:

1. Head and Neck

• Balloons: All balloons (e.g. nasal balloons for posterior nasal bleed) shall be filled with water whenever possible.
• Trapped air: Medical aircraft pressure may need to be adjusted for patient comfort due to the expansion of trapped air in sinuses, dental cavities, or middle ear blockage. Patients with intracranial or intracerebral air will need to be flown at or near a sea-level equivalent pressure. Patients prone to middle ear block will be offered chewing gum and/or afrin nasal spray if clinically appropriate.
• Eye injuries: Air ambulance cabin pressure may need to be adjusted for patients with eye injuries. In addition, these patients and patients with recent eye surgeries shall have their heads elevated and immobilized during flight. Supplemental oxygen will be used for all patients with recent eye injury or eye surgery due to the high oxygen requirements of the retina.
• Neurology insults: All patients with head injuries, brain injuries or cranial surgery shall be loaded with their feet to the rear of the medical aircraft. The patient’s head will be elevated to 30 degrees. Oxygen saturation will be maintained at or above 95%. Foley catheters will be inserted. Patients with a Glasgow Coma Scale (GCS) score of 9 or less shall be intubated unless their baseline GCS is normally 9 or less, or unless they have a valid current DNR requesting no intubation. NG tubes will be inserted unless the patient has a crib form plate or basilar skull fracture.
• Eye humidification: Comatose patients shall be given artificial tears every hour during a medical flight unless eyelids are taped closed. Patients and passengers with contact lenses shall be offered moisturizing eye drops at frequent intervals.
• Seizures: All patients with a history of seizures or a high potential for seizures shall be evaluated for anticonvulsant medication and/or sedation.
• Trauma patients: If the patient complains of c-spine, examine x-ray. If x-ray is not available, apply neck brace prior to transport.
• Wired jaws: An antiemetic shall be given prior to transport via air ambulance. Wire cutters shall be available in the event of emesis.

2. Cardiovascular

• Trapped air: Patients with decompression sickness or those who are at risk of decompression sickness shall be flown at a sea-level equivalent altitude for pressurization purposes.
• Hydration: Fluids shall be encouraged (clinical condition permitting) or IVs administered or adjusted to compensate for low humidity environment. Patients shall receive frequent mouth care with lemon glycerin swabs or fluids.
• Recent MI or unstable angina: Those patients shall be flown in accordance with U.S. Air Ambulance’s unstable angina/recent MI protocol.
• Shock: All patients in shock of any kind shall have an NG tube inserted.
• CHF: All patients in CHF shall have oxygen saturation at or above 95%. They shall be placed with their feet to the rear of the medical aircraft and transported in a sitting or semi-fowler’s position.

3. Pulmonary

• Trapped air: Patients with a pneumothorax shall have this air vented via closed chest tube or needle decompression. If venting is not possible, air ambulance cabin altitude will be adjusted to accommodate this.
• Air filled devices: Airway cuffs shall be filled with water to prevent excessive tracheal pressure.
• Suctioning: Patients with artificial airways shall be suctioned prior to the medical air flight, then at each refueling stop. Frequent suctioning may be required depending on the patient’s clinical condition.
• Pulmonary secretions: Thick and difficult pulmonary secretion may be worsened by the low humidity. Mucous plugs may form. Patients with this problem will be offered humidified air via mask or Guifesen preparations to act as expectorant/mucolytic.
• Oxygen: Oxygen will be available on all medical flights. All air ambulances should prepare for at least 2 lpm. Any patient with a known disease or condition that lessens tissue oxygenation, (e.g. CHF, anemia, COPD, narcotics) or whose condition might be aggravated by hypoxia shall be placed on oxygen during flight with oxygen saturation at or above 90% at all times. (Exceptions to this are addressed elsewhere in this protocol). Patients already on 100% oxygen prior to flight will need to be flown at lower altitudes to maintain adequate oxygenation.
• Special precautions for chronically hypoxic COPD patients: Patients with severe COPD whose oxygen saturations normally run less than 90% should be given only enough oxygen to maintain their “normal” oxygen saturation. Attempting to go higher will only lead to further carbon dioxide retention and possible respiratory arrest or cardiac arrest.
• Severely obese patients: To reduce the risk of barobariatrauma, the patient will be placed on 100% oxygen for 15 minutes prior to the medical air transport. Oxygen saturation will then be maintained at or above 95% throughout the flight with supplemental oxygen.
• Appropriate oxygen supplies: For patients known to require oxygen, the Medical Coordinator will calculate the amount of oxygen needed to meet the patient’s needs for the duration of the air ambulance trip, bedside-to-bedside. Due to potential unforeseen delays in patient transport, a minimum of 150% of the calculated need will be loaded with the patient.

4. Gastrointestinal

• Air filled devices: All balloons shall be filled with water, when possible. If not possible, the pressure must be monitored closely. (e.g. Sengstaken-Blakemore tubes for bleeding esophageal varices.)
• Trapped air: NG tubes, orogastric tubes and colostomy bags shall be vented during flight, not clamped.
• Patients with non-vented intestinal or peritoneal air (e.g. bowel obstruction or recent surgery) may need medical aircraft cabin pressure adjusted to avoid complications of air expansion.
• Air sickness: Patients who are prone to or who develop air sickness shall be offered an antiemetic. This can be done by mouth, injection (IM or IV), suppository (e.g. phenergan) or patch such as trans-derm Scop.

5. Genito-urinary

• Air filled devices: Balloons such as Foley catheters shall be filled with water when possible.
• Voiding: Patients shall be encouraged to void prior to their air ambulance flight as well as during fueling stops. For patients who cannot void easily, Foley catheters will be considered on all flights that are expected to be six hours or longer.

6. Skin

• Patient shall be turned and repositioned at least every two hours whenever possible. For flights over 4 hours, the stretcher should be padded to reduce tissue breakdown.