The medical officer on a high-altitude expedition will be consulted about the prevention and treatment of highaltitude medical problems, as well as the effects of altitude on preexisting medical conditions and fitness for travel to these demanding destinations. Although there have been numerous recent advances in the field of highaltitude medicine, significant morbidity and mortality persist (Table 19.1), and it is essential to better prepare and educate the at-risk population. In this chapter, we review basic physiology of altitude ascent, recognition and management of high-altitude medical problems, altitude effects on chronic medical conditions, and suggested components of a high-altitude medical kit. The reader is also referred to a recent publication for a more detailed review (Hackett and Roach, 2007). See Table 19.2 for online resources. For discussions about children and pregnancy at altitude, see Chapter 9, and for treatment of other conditions that commonly occur on cold weather expeditions (ultraviolet keratitis, hypothermia, frostbite and other cold injuries), please see Chapters 16 on polar medicine, 31 on environmental injuries, and 36 on the eye.
At high altitude (1,500–3,500 m), decreased exercise performance and increased ventilation (lower arterial PCO2) develop due to diminished inspired oxygen. Arterial PO2 is significantly diminished, but saturation levels (SaO2) remain 90% or greater. Because of the large number of tourists who are frequenting ski resort and adventure destinations and pursuing rapid ascents to 2,500–3,500 m, high-altitude illness is common in this range (Tables 19.1 and 19.3).