Decompression is achieved by turning a tap. This simple physical treatment can undoubtedly be life saving. Patients with AMS feel improved within a few minutes. The treatment can be repeated every few hours, over several days. The patient is enclosed in the chamber, and when this is combined with serious illness, claustrophobia is a problem.
Reassurance is necessary to confirm that there are no serious unwanted effects.
Pain in the ear is sometimes a problem as the pressure changes, particularly if the patient has had a head cold. The subject should be told to swallow regularly to equalise pressure in the ears. An altimeter taken inside the chamber is useful. Outside, the observers should maintain contact with the patient, and should not lean on the bag, which causes a sudden, unpleasant increase in pressure within. It is important that members of an expedition understand how to use a Pressure Bag, and actually test the system themselves, before an emergency arises.