ABSTRACTThis paper reviews the contributions of hypothermia and the mammalian diving reflex (MDR) to human survival of cold-water immersion incidents. It also examines the relationship between the victim's age and MDR and considers the protective role played by hypothermia. Hypothermia is the result of a reduced metabolic rate and lowered oxygen consumption by body tissues. Although hypothermia may produce fatal cardiac arrhythmias such as ventricular fibrillation, it is also associated with bradycardia and peripheral vasoconstriction, both of which enhance oxygen supply to the heart and brain. The MDR also causes bradycardia and reduced peripheral blood flow as well as laryngospasm, wh ...view middle of the document...
Hypoxia during drowning and near-drowning incidentsThe major physiological problem facing drowning victims is hypoxia, or lack of adequate oxygen perfusion to body cells. Hypoxia results in damage to many organs, including the heart, lungs, kidneys, liver, and intestines. Generally, the length of time the body has been deprived of oxygen is closely related to patient prognosis. Only 6-7 s of hypoxia may cause unconsciousness; if hypoxia lasts longer than 5 min at relatively warm temperatures, death or irreversible brain damage may result. However, some victims of cold-water immersion have survived after periods of oxygen deprivation lasting up to 2 h.CONCLUSIONSRecent research on cold-water immersion incidents has provided a better understanding of the physiological processes occurring during drowning and near-drowning accidents. Current findings suggest that the cooperative effect of the MDR and hypothermia plays a critical role in patient survival during a cold-water immersion incident . However, the relationship between the two processes is still unclear. Because it is impossible to provide an exact reproduction of a particular drowning incident within the laboratory, research is hampered by the lack of complete details. Consequently, it is difficult to draw comparisons among published case studies.More complete and accurate documentation of cold-water immersion incidents--includ...
