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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 [5,9] - physician passengers provided medical assistance in 48% - flights were diverted because of the emergency in 7% of cases [9] Special laboratory: - pulse oximetry for patients with cardiopulmonary disease - SaO2 < 92%: probable need for in-flight oxygen [2] - SaO2 > 95%: in-flight hypoxia unlikely, no further testing [2] - SaO2 of 92-95%: hypoxia altitude simulation test (HAST) - hypoxia altitude simulation test if prior symptoms on flight [2] - older recommendations - PaO2 < 50 mm Hg or SaO2 < 85% Complications: 1) 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 [11] - modern aircraft maintain cabin air through a mix of fresh air with recycling through HEPA filters [11] - there is little airflow forward or backward between rows - aircaft cabins have ~20% relative humidity [13] - 40%-60% indoor relative humidity associated with fewest COVID-19 cases & deaths [13] - face masks recommended if not required - risk may be higher if aircraft is idle & ventilation system is off 2) deep vein thrombosis (not a medical emergency) a) 14-fold increased risk with oral-contraceptives [3] b) prophylaxis 1] ambulation &/or in-chair exercises 2] adequate hydration (avoid diuretics {alcohol, caffeine}) 3] compression stockings {graded pressure} 4] aspirin 325 mg before a long flight (controversial) 5] enoxaparin (Lovenox) for high-risk patients 6] avoid pre-flight sedatives (reduces movement) c) hypobaric hypoxia of airline cabins does not seem to be risk factor for deep vein thrombosis [4] 3) case of acute ischemic stroke reported [8] - 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 [8] Management: - when a physician is faced with an in-flight emergency, the medical team includes the physician, medical ground control, & the flight attendants [9] - all flight attendants are trained in basic life support including use of automated external defibrillators (AED) [9] - commercial aircraft carry an emergency medical kit, an oxygen tank, & an AED - airline requirements for an emergency medical kit are listed in ref [10] - supplemental oxygen should be provided to air travelers with an SaO2 < 92% [2] - without additional testing [2] - 2 liters/min of oxygen by nasal cannula is suggested [2] - in patients already on long-term supplemental oxygen, doubling the flow rate is generally sufficient to prevent hypoxia [2] 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 [9] - 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 [9] - 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 [9] - airRx is a free app that walks one through the most common inflight emergencies & what to consider doing [12]

Related

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

References

  1. Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 764
  2. Medical Knowledge Self Assessment Program (MKSAP) 11, 15, 16, 17, 19. American College of Physicians, Philadelphia 1998, 2009, 2012, 2015, 2022
  3. Prescriber's Letter 11(2):8 2004 Detail-Document#: 200203 (subscription needed) http://www.prescribersletter.com
  4. Toff WD et al Effect of hypobaric hypoxia, simulating conditions during long-haul air travel, on coagulation, fibrinolysis, platelet function, and endothelial activation. JAMA. 2006 May 17;295(19):2251-61. PMID: 16705106 - Bartsch P. How thrombogenic is hypoxia? JAMA. 2006 May 17;295(19):2297-9. No abstract available. PMID: 16705111
  5. Nable JV, Tupe CL, Gehle BD, Brady WJ. In-Flight Medical Emergencies during Commercial Travel. N Engl J Med 2015; 373:939-945. September 3, 2015 PMID: 26332548 http://www.nejm.org/doi/full/10.1056/NEJMra1409213 - Peterson DC, Martin-Gill C, Guyette FX et al Outcomes of Medical Emergencies on Commercial Airline Flights. N Engl J Med 2013; 368:2075-2083 PMID: 23718164 PMCID: PMC3740959 Free PMC article https://www.nejm.org/doi/full/10.1056/nejmoa1212052
  6. British Thoracic Society Standards of Care Committee. Managing passengers with respiratory disease planning air travel: British Thoracic Society recommendations. Thorax. 2002 Apr;57(4):289-304 PMID: 11923546 Free PMC Article
  7. Silverman D, Gendreau M. Medical issues associated with commercial flights. Lancet. 2009 Jun 13;373(9680):2067-77 PMID: 19232708
  8. Schwamm LH, Jaff MR, Dyer KS, Gonzalez RG, Huck AE. CASE RECORDS of the MASSACHUSETTS GENERAL HOSPITAL. Case 13-2016. A 49-Year-Old Woman with Sudden Hemiplegia and Aphasia during a Transatlantic Flight. N Engl J Med. 2016 Apr 28;374(17):1671-80. PMID: 27119240 http://www.nejm.org/doi/full/10.1056/NEJMcpc1501151
  9. Splete H Is There a Doctor on the Plane? Tips for Providing In-Flight Assistance. Medscape. Nov 15, 2022 https://www.medscape.com/viewarticle/984075 - American College of Emergency Physicians (ACEP) 2022 Scientific Assembly: Presented October 4, 2022.
  10. Advisory Cicular. Emergency Medical Equipment. Jan 12, 2006 https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC121-33B.pdf
  11. Pombal R,Hosegood I, Powell D Risk of COVID-19 During Air Travel JAMA. 2020;324(17):1798 PMID: 33022035 https://jamanetwork.com/journals/jama/fullarticle/2771435
  12. airRx. Available for a Apple Store. Designed for iPad. Runs on iPhone. https://apps.apple.com/us/app/airrx/id1031955544
  13. Ellis R The Right Indoor Relative Humidity Could Ward Off COVID. Medscape. Nov 21, 2022 https://www.medscape.com/viewarticle/984415