The physics of altitude and anaesthesia

Abstract

South Africa’s major cities are located at various altitudes. High altitude is defined as an elevation greater than 1 500 m, which includes most of Gauteng.¹ Globally, about 140 million people live above 2 500 m and an equal number will visit high altitudes each year.²  Consequently, anaesthetists require an understanding of how respiratory and anaesthetic gases behave under conditions of altered barometric pressure.³ As altitude increases and barometric pressure falls, the partial pressure and density of gases decrease. There must be an awareness of the potential for hypoxia, decreased anaesthetic effectiveness, equipment recalibration, and the accuracy of certain equipment at altitude.