Carbon Dioxide Changes in Hyperventilation and Breath-hold Diving

Breath-hold dives to a depth of 10 metres (33 ft) in fresh water at 1 640 metres (6 000 ft) above sea level, at atmospheric pressure (Ps) 625 mmHg, were performed by 5 male divers. The water pressure at 10 metres at this altitude is approximately 1,83 ATA (1 368 mmHg). Peripheral venous blood from the right antecubital vein was analysed for combined CO2 content (cC02) by the Van Slyke method and expressed in cC02 vol.%. The CO2 content of peripheral venous blood is lowered by hyperventilation and increased by repeated breath-hold diving. Individual divers had different rates of CO2 elimination from blood to alveolar air. CO2 elimination is also not the same in anyone diver from day to day. It is postulated that the effects of hyperventilation are unpredictable in different divers under the same diving conditions. This may have contributed to the deaths of several divers in South Africa