Demo on how to use a PAC 

On all our high altitude trips we carry a PAC (Portable Altitude Chamber), the other designs available are Gamow Bag & Certec Bag. All these hyperbaric chambers are artificial pressure chambers, which simulate the altitude at significantly lower elevations with an increase of air pressure inside them.
In case of an altitude emergency the patient is made to descend as quickly as possible. When immediate descent is difficult due to hazards of weather, lack of manpower, light conditions, difficult terrain or geography PAC comes in really handy.
Have a look at the video to see how it is used !