The control of breath holding

The development of a new model for the control of breath holding is described, which is based on the interaction of two dynamic factors; a chemical factor (P CO 2 ), and a non chemical factor which arises from the absence of normal respiratory movement.

Abstract

The factors known to influence the maximum duration of voluntary apnoea (breath holding time) are reviewed and previous ideas on the interaction of these factors are discussed. It is shown that no satisfactory explanation had previously been found to account for all the experimental observations. The development of a new model for the control of breath holding is described, which is based on the interaction of two dynamic factors; a chemical factor (PCO2), and a non chemical factor which arises from the absence of normal respiratory movement. The static lung volume is also incorporated in the model and the role of hypoxia is considered. Sensation is generated as a result of the development of tension in the respiratory muscles which are voluntarily prevented from shortening. The model provides a working hypothesis for the control of breath holding under all of the conditions discussed. These include the effects of alterations in PCO2, PO2, hyperventilation, exercise, acid loading and altitude. By means of the model, it is possible to obtain considerable insight into the behaviour of breath holding under various circumstances.