air travel

Introduction

FiO2 in most commercial aircraft pressured cabins is similar to that an altitude of 6000-8500 feet.

Epidemiology

• in-flight emergencies occur in 1 of every 604 flights
  • physician passengers provided medical assistance in 48%
  • flights were diverted because of the emergency in 7% of cases

Diagnostic procedures

• pulse oximetry for patients with cardiopulmonary disease
  • SaO2 < 92%: probable need for in-flight oxygen
  • SaO2 > 95%: in-flight hypoxia unlikely, no further testing
  • SaO2 of 92-95%: hypoxia altitude simulation test (HAST)
• hypoxia altitude simulation test if prior symptoms on flight
• older recommendations
  • PaO2 < 50 mm Hg or SaO2 < 85%

Complications

• majority of in-flight emergencies involve syncope or presyncope (37%), respiratory symptoms (12%) & nausea/vomiting (9.5%), cardiac symptoms (8%), seizures (6%), abdominal pain (4%), infectious disease (3%), psychosis (2.5%), allergic reaction (2%)
  • risk of becoming infected with COVID-19 during air travel is low
    • modern aircraft maintain cabin air through a mix of fresh air with recycling through HEPA filters
    • there is little airflow forward or backward between rows
    • aircaft cabins have ~20% relative humidity
      • 40%-60% indoor relative humidity associated with fewest COVID-19 cases & deaths
    • face masks recommended if not required
  • risk may be higher if aircraft is idle & ventilation system is off
• deep vein thrombosis (not a medical emergency)
  • 14-fold increased risk with oral-contraceptives
  • prophylaxis
    • ambulation &/or in-chair exercises
    • adequate hydration (avoid diuretics {alcohol, caffeine})
    • compression stockings {graded pressure}
    • aspirin 325 mg before a long flight (controversial)
    • enoxaparin (Lovenox) for high-risk patients
    • avoid pre-flight sedatives (reduces movement)
  • hypobaric hypoxia of airline cabins does not seem to be risk factor for deep vein thrombosis
• case of acute ischemic stroke reported
  • role of physician on board in advising crew & captain that patient must be taken to hospital within 3 hours to receive thrombolysis for ischemic stroke
• cardiac arrest

Management

• when a physician is faced with an in-flight emergency, the medical team includes the physician, medical ground control, & the flight attendants
• all flight attendants are trained in basic life support including use of automated external defibrillators (AED)
• commercial aircraft carry an emergency medical kit, an oxygen tank, & an AED
• airline requirements for an emergency medical kit are listed in ref
• supplemental oxygen should be provided to air travelers with an SaO2 < 92%
  • without additional testing
  • 2 liters/min of oxygen by nasal cannula is suggested
• in patients already on long-term supplemental oxygen, doubling the flow rate is generally sufficient to prevent hypoxia
• acute ischemic stroke
  • role of physician on board in advising crew & captain that patient must be taken to hospital within 3 hours to receive thrombolysis for ischemic stroke
• cardiac arrest
  • difibrillation, aspirin, flight diversion

Notes

• physicians should always carry a copy of their medical license when traveling for documentation by the airline if they assist in a medical emergency during a flight
• physicians are not obligated to assist during an in-flight medical emergency
• in the United States, a bystander who assists in an emergency is generally protected by Good Samaritan laws
• for international airlines, laws where the airline is based generally apply
• the Aviation Medical Assistance Act of 1998 protects people from being sued for negligence while providing medical assistance, unlessthe person is guilty of gross negligence or willful misconduct
• airRx is a free app that walks one through the most common inflight emergencies & what to consider doing

Additional terms

• aircraft
• hypoxia altitude simulation test (HAST)
• travel medicine (traveler's health)