Physiological responses to repeated apneas in underwater hockey players and controls

The aim of this study was to investigate the effects of short repeated apneas on breathing pattern and circulatory response in trained (underwater hockey players: UHP) and untrained (controls: CTL) subjects. The subjects performed five apneas (A1-A5) while cycling with the face immersed in thermoneutral water. Respiratory parameters were recorded 1 minute before and after each apnea and venous blood samples were collected before each apnea and at 0, 2, 5 and 10 minutes after the last apnea. Arterial saturation (SaO2) and heart rate were continuously recorded during the experiment. Before the repeated apneas, UHP had lower ventilation, higher P(ET)CO2 (p < 0.05) and lower P(ET)O2 than CTL (p < 0.001). After the apneas, the P(ET)O2 values were always lower in UHP (p < 0.001) than CTL but with no difference for averaged P(ET)CO2 (p = 0.32). The apnea response, i.e., bradycardia and increased mean arterial blood pressure, was observed and it remained unchanged throughout the series in the two groups. The SaO, decreased in both groups during each apnea but the post-exercise SaO2 values were higher in UHP after A2 to A5 than in CTL (p < 0.01). The post-apnea lactate concentrations were lower in UHP than in CTL. These results indicate that more pronounced bradycardia could lead to less oxygen desaturation during repeated apneas in UHP. The UHP show a specific hypoventilatory pattern after repeated apneas, as well as a more pronounced cardiovascular response than CTL. They indeed showed no detraining of the diving response.