New methods for monitoring dynamic airway tissue oxygenation and perfusion in experimental and clinical transplantation.

A dual circulation, supplied by bronchial and pulmonary artery-derived vessels, normally perfuses the airways from the trachea to the terminal bronchioles. This vascular system has been highly conserved through mammalian evolution and is disrupted at the time of lung transplantation. In most transplant centers, this circulation is not restored. The Papworth Hospital Autopsy study has revealed that an additional attrition of periairway vessels is associated with the development of chronic rejection, otherwise known as the bronchiolitis obliterans syndrome (BOS). Experimental studies subsequently demonstrated that airway vessels are subject to alloimmune injury and that the loss of a functional microvascular system identifies allografts that cannot be rescued with immunosuppressive therapy. Therefore, surgical and medical strategies, which preserve the functionality of the existent vasculature in lung transplant patients, may conceivably limit the incidence of BOS. Given these unique anatomic and physiological considerations, there is an emerging rationale to better understand the perfusion and oxygenation status of airways in transplanted lungs. This article describes novel methodologies, some newly developed by our group, for assessing airway tissue oxygenation and perfusion in experimental and clinical transplantation.