Measurement of regional pulmonary oedema in man using radioactive water (H215O).

Regional extravascular lung water (rELW) has been measured in normal subjects and in patients with left heart diseases using a double-indicator dilution technique and external counting over the chest. Gamma-emitting radioisotopes were injected intravenously, 113Inm as a vascular non-duffusible indicator, and H215O as a freely diffusible indicator. Time activity curves were then recorded over the upper and lower zones of the lung in the supine position with external probes. rELW per unit of blood volume and rELW per unit of blood flow were increased in patients with raised left atrial pressure even in the presence of radiologically clear lung fields. There was a uniform distribution of these ratios between upper and lower zones in normals, whereas in patients rELW was preferentially distributed in the lower zones.