Pulmonary Clearance of 99mTc-DTPA in the Diagnosis and Evolution of Increased Permeability Pulmonary Oedema

Abstract

We measured pulmonary clearance of aerosolised 99m technetium-labelled diethylenetriaminepentacetate (99mTc-DTPA) in thirty-four patients with acute respiratory dysfunction. Results were expressed as a half-time clearance from lung to blood (T½). In sixteen non-smoking patients with acute lung injury, clearance was monoexponential, median T½ 11, range 4–40 min, and in five multi-exponential, median rapid T½ 3 min, with a slower median T½ of 18 min (range 2–4 and 15–31 min respectively). Clearance was significantly (P < 0.0001) more rapid than normal non-smoking subjects previously studied (median T½ 70, range 37–182 min). Three smokers with acute lung injury had T½s of 5, 18 and 22 min, not significantly (P> 0.05) quicker than normal smokers previously studied (median T½ 20, range 6–73 min). One smoking lung-injured patient had an abnormal multi-exponential 99mTc-DTPA clearance. Four patients with cardiogenic pulmonary oedema had T½s within the normal range. Repeated measurements made on nine patients with acute lung injury showed that clearance remained abnormally rapid despite improvements in lung radiographic appearance and gas exchange. We conclude that the 99mTc-DTPA technique provides a virtually non-invasive measure of alveolar-capillary barrier dysfunction in non-smoking patients with acute lung injury.