Cerebral and peripheral hemodynamics and oxygenation during maximal apneas

Central and peripherial hemodynamic and oxygenation in response to maximal apneas are scarcely studied in elite divers. In this study we examined whether brain perfusion and oxygenation is compromised during maximal apneas in ten divers and ten control subjects. Doppler ultrasound was used to assess middle cerebral and brachial artery mean blood velocity and near‐infrared spectroscopy for determination of cerebral and muscle oxygenation (ScO 2 and SmO 2 , respectively). Arterial desaturation and increase in arterial pressure was more pronounced in divers compared to controls. Apnea caused decrease in ScO 2 which was more evident in divers due to their greater increase in deoxyhemoglobin. Middle cerebral artery blood velocity increased significantly more in divers because greater reduction in vascular resistance but it was not capable of preventing desaturation. Larger reduction in muscle oxyhemoglobin was found in divers compared to controls, whereas brachial blood flow was reduced for similar amount in both groups. These data indicate that trained divers have decreased ScO 2 at the end of breath‐hold despite large increases in middle cerebral artery blood velocity and cerebral oxygen delivery. Greater reduction in SmO 2 occurred in divers due to longer breath‐hold duration. This study provides further evidence for the oxygen‐conserving effect in elite divers in maintaining the oxygen supply of brain in this extreme situation. This study was supported by Croatian Ministry of Science, Education and Sports.