Hemodynamic and respiratory changes in athletes during deep breath-hold diving

BACKGROUND: The study analysed the hemodynamic and respiratory aspects of deep breath-hold diving. METHODS: One male (59-year-old) and one female (32-year-old) subject were enrolled. They were both champion deep breath-hold divers. The dives were performed in the wet compartment of the hyperbaric chamber, first in thermoneutral (35 degrees C) and then cool (25 degrees C) water. The subjects were monitored using ECG recordings; percentage cannulation of the right radial artery using an aseptic technique. Stroke volume (SV) and cardiac output (CO) were measured using impedance cardiography (Bomed). RESULTS: Variations were observed in heart rhythm, cardiac output, arterial blood pressure and breathing. Both bradycardia and many hemodynamically effective dysrhythmias influenced CO, which showed a tendency to decrease in the diver in cool water. Changes in CO were caused by concomitant changes in HR as SV showed no significant variations. During breath-hold diving, a drop in intra-thoracic pressure is likely to enhance redistribution of blood from the periphery to the chest, which might distend the heart even more, contributing to dysrhythmogenesis. The observation that dysrhythmias were more frequent in cool water is in line with these concepts. CONCLUSIONS: Only two leading divers were recruited in this study and observed for hemodynamic and respiratory changes. However, these findings are in line with similar studies carried out by other authors.