Blunted hypoxic pulmonary vasoconstriction in apnoea divers.

, P = 0.0222). With sildenafil, Divers and Controls had similar blunted increases in total pulmonary resistance after 20-30 min of hypoxia. Divers also had a significantly lower systemic vascular resistance after sildenafil in normoxia. These data indicate that repetitive apnoea diving leads to a blunted hypoxic pulmonary vasoconstriction. We suggest that this is a beneficial adaption allowing for increased cardiac output with reduced right heart work and thus reducing cardiac oxygen utilization in hypoxaemic conditions.