A portable hyperbaric bag, of which one brand is the Gamow bag, is an inflatable pressure bag large enough to accommodate a person. The patient can be placed inside the bag, which is then sealed and inflated with a foot pump. Within minutes, the effective altitude can be decreased by 1000 m to as much as 3000 m depending on the elevation. The bag is pressurised to 14.0–29.3 kPa (105–220 mmHg); the pressure gradient is regulated by pop-off valves set to the target pressure.