Briefly discuss the problems specific to aeromedical transport of a critically ill patient.

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College Answer

•    Transport by any means involves risk to staff and patients
•    Need   to   be   familiar   with   the   use   of   the   transport   vehicle’s   O2,   suction, communications,and other equipment systems.
•    Reduction  in partial pressure  of oxygen  with altitude,  critically  ill patients  who are already dependent on high FiO2 may be further compromised.
•    Expansion of trapped gases – pneumothoraces, intracranial air from injuries
•    Expansion   of  air  containing   equipment   –  ET  tube,  Sengstaken   tube.  ET  cuff pressures will need to be adjusted
•    IABP difficult to transport
•    Risk of hypothermia
•    As water partial pressure falls, risk of dehydration through resp losses and passive humidification important
•    Auscultation is difficult.
•    The ventilated patient is placed in the Trendelenburg and the reverse Trendelenburg positions during take off and landing respectively. This can impact on perfusion and oxygenation.
•    Potential for pacemaker malfunction due to avionic interference.
•    Staff doing air transport should refrain from compressed gas diving for at least 24 hrs prior to transfer.
•    Physical   problems:   cold,   noise,   lighting,   access   to  patient,   motion   sickness, acceleration injuries (eg head to front of plane to avoid increased ICP on takeoff)

Discussion

This answer would benefit from a systematic approach:

Limitations of the aircraft

  • Little space for large equipment (eg. ECMO, IABP)
  • Little space for gas reserve (O2)
  • Less equipment available
  • Little room for CPR
  • Changes in aircraft tilt place the patient in Trendelenberg and reverse Trendelberg positions
  • Hypothermia can develop in the cold cabin
  • The aircraft is noisy
  • The lighting is sub-optimal
  • Turbulence can cause injuries to the poorly restrained patient

Dangers of altitude: changes in the behaviour of gases

  • ETT cuffs expand
  • Gas-filled cavities expand (eg. bowel, pneumothorax, pneumoencephalus)
  • Partial pressures of gas mixtures is lower (100% FiO2 at 2100m, the standard "cabin altitude" of commercial aircraft, is only 597mmHg)
  • Evacuation by air of those who have bee deep-sea diving is best avoided for about 24 hours- decompression sickness may result.

Dangers of altitude: changes in fluid behaviour

  • Decreased boiling point at altitude increases the rate of evaporative loss

Dangers of aircraft operation

  • Avionics may interfere with pacemakers
  • Noise may interfere with equipment alarms
  • Vibration interferes with examination of the pulse
  • Auscultation is practically impossible
  • Motion sickness may cause vomiting and aspiration (it would suck to be intubated purely because of motion sickness)

References