d blood cells), produces more of a particular enzyme that facilitates, and releases oxygen from hemoglobin to body tissues, these are all changes to try and carry more oxygen throughout the body (Curtis 2). Any or all of these changes may encourage periodic breathing to start. Periodic breathing is cycles of normal breathing – breath holding – accelerated breathing, these are caused by the differ!
             ence of carbon dioxide in the blood. Carbon dioxide is the key signal to the brain to breathe, so with the different levels of carbon dioxide in the blood it may confuse the brain, which causes periodic breathing (Dietz 2).
             General measures for normal acclimazation are to avoid sleeping at greater then 3000 meters after a rapid ascent, spend 2 to 3 nights at 2500 meters to 3000 meters before ascending further. Spend an extra night for acclimazation every 600 meters to 900 meters if continuing to ascend. Day trips to higher altitude with return to lower altitudes are also suggested (Hackett 2-3). Between 2000 meters and 3000 meters ascent should not exceed 400 meters a day
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