623220 Methods and systems are disclosed for maintaining, evaluating, and providing therapy to a lung ex vivo. The methods and systems involve positioning the lung in an ex vivo perfusion circuit； circulating a perfusion fluid through the lung, the fluid entering the lung through a pulmonary artery interface and leaving the lung through a left atrial interface； and ventilating the lung by flowing a ventilation gas through a tracheal interface. Maintaining the lung for extended periods involves causing the lung to rebreathe a captive volume of air, and reaching an equilibrium state between the perfusion fluid and the ventilation gas. Evaluating the gas exchange capability of the lung involves deoxygenating the perfusion fluid and measuring a time taken to re-oxygenate the perfusion fluid by ventilating the lung with an oxygenation gas.
