Page 229 - 2026 SMOG

ALTITUDE PHYSIOLOGY AND PATIENT TRANSFER
Altitude Concerns for Aeromedical Transfers
• Gas expansion occurs as altitude above sea level increases. Gas volume doubles at 18,000'
mean sea level (½ sea level atmospheric pressure) and increases 25% from 5,000'–10,000'. This
will typically not affect the operational ceiling for the UH-60 Blackhawk during aeromedical
evacuation operations. Certain conditions and precautions to note:
˚ Air embolism/Decompression illness—This is the only absolute contraindication to
transport of patients at altitude. These patients should be transferred at sea level or in an A/C
capable of cabin pressurization to sea level.
˚ Pneumothorax—There is little risk of developing a tension PTX due to gas expansion from
altitude during typical aeromedical evacuation flights in rotary-wing A/C. However, altitude
should be limited when possible to <5,000' MSL. If mission requirements mandate higher
altitudes, the use of aeromedical evacuation platforms with pressurized cabins should be
considered as applicable and tactically capable. Prophylactic chest tubes (for altitude-related
concerns) are recommended for any flights above 10,000' mean sea level.
˚ Gastric distention—Gas expansion does increase the risk of vomiting and, therefore,
aspiration. Therefore, all patients with decreased LOC should have an NG/OG tube placed
prior to transfer.
˚ Head injury—As with PTX, there is little concern of altitude-related elevation of ICP
in head-injured patients, although penetrating intracranial or maxillofacial injuries may
set conditions for an entrappedgas phenomenon with adverse clinical consequences. Any
evidence of elevated ICP should result in treatment per the guidelines. Altitude restrictions
do not differ from those listed for PTX. Constant vigilance should be maintained for
evidence of elevation of ICP.
˚ Eye injury—Penetrating eye injuries or surgeries may introduce air into the globe. Again,
the altitudes obtained for rotary-wing A/C do not pose a risk of elevating the IOP during
normal operations.
˚ Gas-filled equipment—Medical equipment with gas-filled bladders also may suffer from
interference at high-altitudes. Primarily, endotracheal tube cuffs and pressure bags should be
evaluated at altitude by testing the pressure of the exterior bladder or by filling them with air.
If able, utilize a manometer to verify tube pressure. A cuff pressure between 20–30cmH O
2
is recommended to provide an adequate seal and reduce the risk of complications or
tissue damage. Verify with the supervising physician or flight surgeon before filling the
endotracheal tube with saline. Routine filling of endotracheal tubes with saline is no longer
recommended.
• Flow Rates—Decreased atmospheric pressure may interfere with IV flow rates and/or pump
function. These must be monitored continuously.
• Invasive Blood Pressure—Adjust/recalibrate monitor every 1000' if required based upon
monitoring device.
• Hypothermia—As altitude increases, the temperature will drop about 3.5°F per 1000 feet. This
is further complicated in the MH-60 due to rotor-wash, forward airspeed, and normal lapse rate.
Therefore, patients must be protected from hypothermia at all times. This includes the use of
the Hypothermia Prevention and Management Kit (HPMK), blankets, heaters if available, and
closing cabin doors/crew windows during transport.
(continues)

2026 Standard Medical Operating Guidelines (SMOG) • 221