Detection of acute inhalation injury in fire victims by means of technetium-99m DTPA radioaerosol inhalation lung scintigraphy

Mortality and morbidity in fire victims are largely a function of injury due to heat and smoke. While the degree and area of burn together constitute a reliable numerical measure of cutaneous injury due to heat, as yet no satisfactory measure of inhalation injury has been developed. In this study, we employed technetium-99m diethylene triamine penta-acetic acid (DTPA) radioaerosol lung scintigraphy (inhalation scan) to evaluate acute inhalation injury in fire victims. Ten normal controls and 17 survivors from a fire accident were enrolled in the study. All patients suffered from respiratory symptoms (dyspnoea and/or cough with sputum).99mTc-DTPA aerosol inhalation lung scintigraphy was performed in all subjects, using a commercial lung aerosol delivery unit. The degree of lung damage was presented as the clearance rate (k; %/min) calculated from the time-activity curve over the right lungs. In addition, the distribution pattern of the radioactivity in the lungs was evaluated and classified into two groups: homogeneous distribution and inhomogeneous distribution. A plain chest radiograph (CxR) and pulmonary function test (PFT) were performed in the same group of patients. The results showed that 6/17 (35.3%) opatients had inhomogeneous distribution of radioactivity in their inhalation scans, and 11/17 (64,7%) had homogeneous scans. Five of the six patients with inhomogeneous scans were admitted for further management, and all patients with homogeneous scans were discharged from the emergency department and needed no further intensive care. The clearance rates of the right lung were 0.73%±0.13%/min from normal controls and 1.54%±0.58%/min for fire victims. The difference was significant, with aP value of less than 0.01. Using a cut-off value of 0.9%/min (all normal subjects were below 0.9%/min) 14 (82.4%) patients had abnormal clearance rates of99mTc-DTPA from the lung. In contrast, only three (17.6%) patients had abnormal CxR and three (17.6%) had abnormal PFTs. We conclude that (1) conventional CxR and PFT are not good modalities for evaluating inhalation injury in fire victims because of their low sensitivity, and (2)99mTc-DTPA radioaerosol inhalation scintigraphy can provide an objective evaluation of inhalation injury during a fire accident and may be useful in therapeutic decision-making and disease monitoring.