LUNG/HEART RATIO TC99m ALBUMIN STUDIES TO SEPARATE PULMONARY EDEHA DUE TO PRESSURE/VOLUME OVERLOAD FROM THAT DUE TO DAMAGED CAPILLARIES

The hypothesis tested was that edema resulting from pulmonary capillary damage is accompanied by an increased net leakage of molecules such as albumin from the vascular space into the lung, whereas edema resulting primarily from increased venous pressure is not. Tc99m albumin was injected intravenously in three groups of patientsnormal, cardiac failure, and adult respiratory distress syndrome (ARDS). One minute of data from an anterior view of the chest was obtained at 20 minutes and 3 hours following injection of 20mCi. A lung heart ratio (L/H) was calculated placing a box region of interest over the right mid lung field and the middle of the cardiac silhouette. In absolute increase of less than 10% between L/H1 (20 min) and L/H2 13 hrs) included all normal patients. All but 2 of the 18 patients with heart failure or volume overload edema had a L/H ratio which increased less 10%. Patients with ARDS showed a spectrum of L/H ratio changes from less than 10% in all 6 with narcotic overdose to an increased ratio in 3/10 with pneumonia, 2 of 2 with seizures, one each with blood transfusion reaction, sickle cell disease, eclampsia and 1 of 2 with tuberculosis.Using a ratio change corrects for geometric factors, chest wall uptake, variable blood clearance rates and label loss. This simple procedure, adaptable to the bedside, clearly distinguishes a volume or pressure overload group showing no L/H change over time, from those with other causes of pulmonary edema. It suggests that ARDS contains a wide spectrum of capillary changes.