ABSTRACT
Hypoxia is an insufficient supply of oxygen reaching the tissues. Acute hypoxia refers to effects experienced over a few seconds to a few hours; chronic effects of hypoxia predominate over days to weeks. There are four main forms of hypoxia: hypoxic, anaemic, ischaemic and histotoxic. In the aviation environment, main cause of acute hypoxia is insufficient alveolar oxygen as a result of reduced atmospheric pressure – Hypoxic hypoxia. Multiple types of hypoxia can coexist. Alveolar gas equation is used to calculate alveolar oxygen content. Alveolar water vapour pressure remains constant with ascent to altitude, and so becomes increasingly important component of alveolar content. Hypoxic ventilatory response is a reflex which increases ventilatory drive in an attempt to maintain oxygen levels. Hyperventilation is defined as breathing in excess of metabolic needs, eliminating more carbon dioxide than is produced, to produce hypocapnia.
