Hyperbaric chambers or Gamow bags are an inflatable, sealable bag. It provides concentrated oxygen to a person suffering from altitude sickness by simulating the conditions of a lower altitude. As a result, the symptoms of altitude sickness decrease.
Originally, the bag was designed as a training aid for athletes to help them acclimatize to high altitude conditions. Over time, however, the bag also got recognized for its role in treating severe altitude sickness.
After a person is treated in the Gamow bag, the acclimatization effects can last for many hours. This gives them enough time to make a descent.