Keith L. Dorrington

The effects of intravenous endothelin-1 (ET-1) on the ventilatory response to hypoxia were studied in healthy humans. Nine volunteers were each exposed twice to 4 hr eucapnic hypoxia. They received a continuous infusion of ET-1 during the ET-1 protocol and an infusion of saline during the control protocol. Plasma ET-1 levels and an index of ventilation were measured regularly. Hypoxia caused a rise in plasma ET-1 in the control protocol. Hypoxia also caused the index of ventilation to increase in both protocols, and this increase was greater in the ET-1 protocol than in the control protocol. These results are consistent with the hypothesis that ET-1 plays a role in controlling the ventilatory response to hypoxia in man.

The ability of alveolar gas composition to influence pulmonary vascular tone has been appreciated for over 50 years. In particular, it has been proposed that both O₂ and CO₂ could play a role in the matching of perfusion to ventilation within the lung, improving the overall efficiency of gas exchange. A wide variety of experimental approaches has been used to investigate pulmonary vascular effects of the respiratory gases in a range of mammalian species. In this article, we review experiments performed in healthy humans, identify particular difficulties in the interpretation of such experiments, and discuss possible approaches to future study.