Effect of altitude change on MAST suit pressure.

Transport of patients involving changes in altitude has become commonplace in the treatment of trauma patients. Often these patients are treated with medical antishock trouser (MAST) suits initially and during transport. The effects of altitude changes on the pressures generated in MAST suits were systematically investigated. Jobst Standard Antishock Air Pants were applied to the lower half of a Resusci-Anne dummy and inflated to 30 mm Hg of pressure. In a simulation of patient transport, the inflated MAST suit and dummy were placed in a helicopter and ascended from 2,500 feet to 9,500 feet. Pressures increased to 84, 87, and 87 mm Hg in three separate trials. Intermittent MAST suit pressure readings at 1,000-foot increments in altitude showed a positive linear relationship. Three descending trials, in which the MAST suit was inflated to 60 mm Hg at 9,500 feet and the helicopter descended to 2,500 feet, were also done. Pressures dropped to 7, 8.5, and 8 mm Hg in the three trials. A positive second order relationship between MAST suit pressure and altitude was noted for the descending trials. It was concluded that MAST suit pressure is a function of altitude. Emergency medicine personnel should be aware of this, and should monitor patients accordingly when transporting through changes in altitude.