Studies the energy metabolism and respiratory functions in Korean UDT divers
There are a number of reports on the respiratory, circulatory, and metabolic adaptive changes during long-term diving, but most of these investigations have been generally confined to skin diving(breath-hold diving) or self-contained underwater breathing apparatus (SCUBA) diving and sometimes deep sea diving.
Modifications of pulmonary mechanics have been reported in Korean diving women (Hong, 1961; Song et al., 1963), Japanese ama (Tatai, 1957; Tatai and Tatai, 1965; Kobayasi et al., 1971), U.S. Navy submarine escape training tank instructors (Carey et al., 1956; Schaefer, 1958) and swimmers (Newman et al., 1961). In the study of breath holding time and ventilatory responses to CO^^2 in Korean ama (Song et al., 1963; Kang et al., 1965) and in U.S. Navy tank instructors (Schaefer, 1955, 1958),
the aquatic adaptative changes were also observed.
The underwater demolition team (UDT) of the Korean Navy is engaged daily in hard exercise including swimming, SCUBA diving and breath-hold diving all year around including the winter season i.e. they are engaged in a mixed type of diving. When
the temperature of the sea water is cold, they wear thermal protecting suits.
Considering such differences in water activity, i.e. "a mixed type of dive" for UDT, this study was conducted to see whether any difference exists in physiological adaptations between UDT and other divers. In this study, 30 members of the UDT and
10 members of the ROK Navy were chosen as experimental and control group, respectively.
The items measured were the lung volumes, maximal breathing capactiy, breath holding time, maximal respiratory pressure (MIPand MEP), cardiopulmonary responses to CO^^2 and daily energy metabolism. The lung volumes (except residual volume) and maximal breathing capacity were measured by a Collins 9-L spirometer and the residual volume was measured by "Rahn's three breathing method". Breath holding time with maximal inspiration was determined with the face immersed in water;
Maximal respiratory pressure was measured by a mercury manometer. The daily energy metabolism was calculated from the oxygen consumption (VO^^2) during each activity and from the daily activity chart in both summer and winter.
The results are briefly summarized as follows;
1) Among the various lung volumes measured, residual volume and functional residual capacity were significantly smaller in the UDT compared to that of controls.
2) Breath holding time of the UDT (122.3 sec) was significantly longer than that of controls(76.6 sec).
3) Both the maximal inspiratory and expiratory pressure at different lung volumes were significantly higher in the UDT than that of controls.
4) Ventilatory response to a 5% CO^^2 breathing mixture, among other cardiopulmonary responses, was significantly diminished in the UDT compared to the controls.
5) The daily energy expenditure was higher in winter than in summer, i.e. 5,036 Cal/day and 4,378 Cal/day, respectively. This difference was attributed to a larger heat loss during dives in winter. The results of breath holding time and ventilatory response to CO^^2 in the UDT are comparable to those of other reports, suggesting that there was a decrease of sensitivity of the respiratory center to carbon dioxide. However, it is of interest that the maximal inspiratory pressure at each lung volumes was distinctively higher in Korean ama(Song et al., 1963) and Japanese ama (Kobayasi et al., 1971), whereas both the maximal inspiratory and expiratory pressures were higher in the UDT> This may be possibly attributed to the fact that ama engages in negative pressure breathing during skin diving, while the UDT members are engaged in positive pressure breathing during SCUBA dives.
On the basis of above results, it may be concluded that the UDT members who practice a mixed type of dive, also develope adaptive changes in the aquatic environment.