Altitude sickness, also known as acute mountain sickness, is caused by low concentration of oxygen molecules at altitude. Although the percentage of oxygen remains at 21% of air, the low air pressure above 2,500m decreases the number of oxygen particles inhaled.

 

The body reacts by a rise of hemoglobin concentrations to bring oxygen to vital organs thanks to the red blood cells. But ventilation and dehydration generates a fall in the plasma volume caused by the loss of water molecules through breathing.

 

The acclimatization process is thus vital to adapt to altitude and reduce the effects of Altitude Sickness on the body. The use of supplemental oxygen also allows to ward off the primary symptoms of AMS.

 

With the altitude, the oxygen level in the blood decreases. Climbing with supplemental oxygen reduces the impact of the altitude by lowering artificially the true altitude. It prevents headaches and AMS effects (nausea, vomiting, fatigue, weakness etc). Supplemental oxygen along with adequate acclimatization processes help the body to adjust to lower oxygen levels at high altitudes.

 

We use 4L Oxygen cylinders and the "TopOut" oxygen masks manufactured by Ted Atkins, a former RAF Engineering Officer.

 

What makes the "TopOut" mask different from the Poisk system?  The mask includes a reservoir that allows a higher level of oxygen to be inhaled when breathing in without the waste of oxygen flow when breathing out. Thus, you get the right amount of oxygen when climbing. The mask is also far better fitting than the POISK ones. With two different sizes available, the mask fits your face, enhance climber's comfort, does not obstruct the climber's vision and avoids any slip on the goggles. Valves are also removable and the mask is washable with water and soap to keep the device clean and germ free.

 

The system has gained in popularity and is now used by most expeditions. On Reach Summit Everest expeditions, a number of 7 bottles (oxygen cylinders) with masks and regulators are included in the price. Additional bottles are also stored at Base Camp and will be carried by the climbing Sherpa. When in Kathmandu, you could test the TopOut system and get more familiar with it.