If for some reason the MAST has to be deflated in the field, this should be done slowly and methodically with the vital signs taken after each deflation and prior to deflating further. During the deflation, the blood pressure should be checked every two minutes. A drop of 5 mm Hg or more indicates the need to stop the deflation and have 100 to 200 ml of fluid by IV until the blood pressure is stabilized. The process is continued until fully deflated. Rapid loss in pressure or deflation of the MAST can be dangerous.
Sudden deflation is physiologically equivalent to losing two units of blood in a few seconds time.
Changes in temperature can also cause partial deflation. Going from summer heat to the air-conditioned ER can cause partial deflation of the garment. The same is true for helicopter use. The pressure in the garment increases as altitude is gained and decreases as altitude is lost. The pressure should be carefully monitored whenever there are any temperature or altitude changes.