Research Paper

CHAPTER 1

THE PROBLEM AND ITS BACKROUND

ABSTRACT

This 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, which protects victims against rapid inhalation of water. Studies of drowning and near drowning of children and adults suggest that victim survival depends on the presence of both hypothermia and the MDR, as neither alone can provide adequate cerebral protection during long periods of hypoxia. Future research is suggested to improve patient care.

INTRODUCTION

Drowning and near-drowning incidents are leading causes of mortality and morbidity in both children and adults. 1 2

Over the past 30 years, there has been considerable interest in cold-water immersion incidents, particularly the reasons for the survival of some victims under seemingly fatal conditions. Research suggests that both hypothermia and a “mammalian diving reflex” (MDR) may account for survival in many near-drowning episodes.

However, the extent to which these two processes interact is not fully understood. Controversy also exists regarding the effect of the victim’s age on the physiological responses to cold-water immersion.

In this paper, I provide an overview of recent research on the protective value of hypothermia and the MDR in cold-water immersions. I also examine hypotheses concerning the effects of age on these processes and conclude with suggestions about...