The aim of respiratory support is to optimize oxygen delivery to vital organs by ensuring adequate oxygenation with minimal cardiovascular depression. The risk of pulmonary infection should be minimized by aseptic tracheal suction and postural drainage, as there are no constraints on these procedures once the diagnosis of brainstem death has been established. PaCO2 should be allowed to return to normal levels in order to avoid the vasoconstriction associated with hypocarbia. Since carbon dioxide production falls after brainstem death, this may require a considerable reduction in minute volume or the addition of dead-space. The inspired oxygen concentration should be adjusted to achieve adequate saturation of hemoglobin with oxygen but, particularly if the lungs are to be transplanted, the fractional inspired oxygen concentration should, if possible, be maintained below 0.5 to 0.6 to avoid oxygen toxicity. High levels of positive end-expiratory pressure (PEEP), which can reduce cardiac output and exacerbate ventilator-induced lung injury, should be avoided, although if the lungs are to be transplanted, a low level of PEEP (5 cmH 2O) is recommended to prevent alveolar collapse. Other recommendations for potential lung donors include the avoidance of barotrauma by keeping peak inspiratory pressure below 30 cm H2O and the use of colloids rather than crystalloids to maintain the circulating volume.
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