PULMONARY OEDEMA/ARDS ulmonary edema is a potential cause of hypoxia in the perioperative patient. The accumulation of excessive alveolar fluid results in hypoxia due to interference with diffusion across the alveolar capillary membrane. Frothy (sometimes blood-stained) sputum may be expectorated or observed in the endotracheal tube. the abnormal accumulation of fluid in the interstitial or alveolar spaces of the lung can be explained on the basis of a disturbance in the normal Starling equation1. It involves changes in hydrostatic or oncotic pressure across the alveolar membrane or in the permeability of the alveolar membrane such that fluid moves across from the capillaries into the alveolar space. P