A field study of the ventilatory response to ambient temperature and pressure in sport diving

Abstract

This study reports on the relationship between minute ventilation (V̇E) and environmental variables of temperature (T) and pressure (P) during open water diving. The author conducted a total of 38 dives involving either a light (20 dives) or a moderate (18 dives) level of physical activity. Within each of these groups, P and T taken together accounted for about two thirds of the variance in the V̇E data. A very significant increase in V̇E was observed as T decreased (1 < T(°C) < 22), and the magnitude of this increase at a given pressure level was similar in the 'light' and the 'moderate' data sets. A second order observation, particularly notable at lower temperature, was the decrease in V̇E with increasing pressure under conditions of light work. Empirical functions of the form V̇E = A + B/P n[1 + exp (T - 8)/10], where A, B, and n are adjustable variables, could accommodate both data sets over the whole range of T and P. These results are the first obtained under actual diving conditions to provide evidence for interactions between P, T, and V̇E. Understanding the physiological mechanisms by which these interactions occur would assist in appreciation of the limitations imposed on scuba divers by the environmental conditions as they affect their ventilatory responses. © 1995.