[Ventilatory adaptations for breath holding in divers]

Abstract

The length of breath-hold duration in divers is dependant on a number of interacting variables which include mechanical factors (lung volumes), chemical factors (sensitivity to hypoxia and hypercapnia), non-chemical factors (involuntary muscular contractions), psychological factors (motivation, stress, competition) and various extrinsic factors (training, muscular exercise). These stimulus provoke the unpleasant sensation of an urge to breathe at the termination point of the breath hold. Training and experience produces adaptations in divers which decreases sensitivity to CO(2) and which delays and minimises the involuntary contractions of respiratory muscles provoked by the absence of respiratory movements. These adaptations modify the breaking point of, and increase the duration of breath holding. Godfrey & Campbell's model (1968), modified by Courteix et coll. (1993) and Delapille (2000), attempts to explain the control of breathing in the context of apnea and to define the effects of each of these stimulus on the respiratory activity of divers and non-divers.