Description

Physicians commonly help with in-flight medical events (IME). Many IMEs fall outside a practitioner’s normal scope of practice. The aircraft environment is cramped with limited medical resources. Despite these obstacles, health care workers should be prepared to render assistance in these situations.

Epidemiology

Incidence

• 2.9 million passengers travel daily worldwide. In the United States, 1.7 million individuals travel by plane every day.
• Airlines estimate an IME occurs on 1 in 40 flights or in 1 per 7,500 to 40,000 passengers. Most are minors, and 65–70% are handled by the flight crew (1),(2).
• The likelihood of encountering an IME is increasing because of larger aircraft, longer flights, and an aging population.
• The most common IMEs involve syncope/near syncope (32.7%), gastrointestinal (14.8%), respiratory (10.1%), and cardiovascular symptoms (7%) (2).
• In otherwise healthy passengers, vasovagal syncope represents up to 90% of IMEs.
• 5% of passengers suffer from a chronic illness and account for 2/3 of IMEs.
• 15% of ground-based physician calls are for pediatric passengers.
• 3% of IMEs are fatal.

Etiology and Pathophysiology

Hypobaric hypoxia: Atmospheric pressure of oxygen drops from 160 mm Hg at sea level to 120 mm Hg at cruising altitude in a pressurized cabin. In healthy people, the arterial oxygen tension drops from 100 to 60 mm Hg with associated mean inflight oxygen saturations of 93% (range: 85 to 98).

• Gas expansion: Gases expand about 30% in flight. This can lead to a pneumothorax, wound dehiscence or perforation from bowel gas expansion, sinus pressure, and tympanic membrane rupture in children with ear infections.
• Venous thromboembolism: There is an increased risk of deep vein thromboses (DVTs) on longer flights and in passengers with underlying medical conditions because of prolonged sitting, hypoxic conditions, and dehydration.
• Stress: Travelling is mentally and physically stressful, which may lead to psychiatric emergencies or acute coronary syndrome (ACS).
• Insomnia: Passengers have disrupted circadian rhythms, which may trigger seizures and contribute to medication nonadherence.
• Turbulence: Motion sickness is common and traumatic injury can result from falling luggage.
• Medication nonadherence: Forgotten or checked medications may lead to glycemic control problems, seizures, blood pressure instability, and inaccessible as needed medications.
• Decreased access to food and drink: Vasovagal syncope may result from dehydration. Diabetics may suffer hypoglycemia.
• Low air humidity: Cabin air is <20% relative humidity, which contributes to dehydration, epistaxis, and asthma or COPD exacerbations.
• Viral infections: Parainfluenza and influenza are the most common viruses communicated by proximity. The cabin air is filtered and not infectious.

Risk Factors

• Recent surgery: Passengers are at risk for wound dehiscence, bowel perforation, and compartment syndrome from gas expansion.
• COPD, asthma, CHF, or coronary artery disease: Passengers may suffer from hypoxemia and may not be able to compensate appropriately.
• Recent cast placement: Passengers are at risk for compartment syndrome due to tissue edema.
• Hypercoagulability: Passengers with inherited or acquired hypercoagulable conditions, pregnancy, certain medications, heart disease, or recent surgery are at increased risk for DVTs.
• Recent scuba diving: Passengers are at risk for decompression syndromes.
• Long flights: The effects of hypoxia are cumulative and time dependent.

General Prevention

General guidelines:

• Travelers should discuss medication timing with their doctor and bring necessary medications and equipment onboard.
• Supplemental inflight oxygen is required for patients with a baseline PaO₂ <70 mm Hg or who are unable to walk a flight of stairs or 150 feet without having shortness of breath or experiencing angina (3)[C].

Pregnancy Considerations
Women are generally safe to fly until 36 weeks’ gestation.

Pediatric Considerations

• Travelers with children should bring liquid formulations of medication in allowed quantities on the plane. Children with asthma should have a rescue inhaler with spacer and facemask.
• Specific guidelines:
  • Avoid flying 10 to 14 days after surgery (varies by type of surgery).
  • Casts may need to be bivalved if applied 24 to 48 hours before a flight.
  • Avoid scuba diving 24 hours before flying.
  • DVT prevention (3)[C]:
    • Adequately hydrate.
    • Stand, stretch, and exercise the legs in flight.
    • Passengers with risk factors may need compression stockings, aspirin, or anticoagulation.