ELASTIN FIBER ANALYSIS IN ACUTE DIFFUSE LUNG INJURY CAUSED BY SMOKE-INHALATION

Objective: The evaluation of various techniques to diagnose or exclude ventilator-associated bacterial pneumonia has been a focus of much re search. One such technique involves elastin fiber detection. It has be en inferred from previous work that 40% potassium hydroxide preparatio ns of respiratory secretions that demonstrate elastin fibers have a 10 0% specificity in diagnosing bacterial pneumonia in intubated, mechani cally ventilated patients without acute diffuse lung injury. The purpo se of this investigation was to ascertain if elastin fibers might be d etected in respiratory secretions in acute, diffuse lung injury in the absence of pneumonia (i.e., assess specificity). Design: An animal mo del using a standardized smoke inhalation protocol to cause acute, dif fuse lung injury was used. Materials and Methods: Respiratory secretio ns collected from the endotracheal tubes from eight sheep that underwe nt the standardized smoke inhalation protocol and were examined with 4 0% potassium hydroxide. Histologic data were obtained from autopsy to diagnose or exclude lung injury and pneumonia. Measurements and Main R esults: We found six (false) positive elastin fiber preparations in th e absence of histologic pneumonia. Specificity was 0.25. Conclusions: We concluded that seeing these results, given a true specificity of 0. 99 inferred from previous work, is highly improbable with a probabilit y of 2.74 x 10(-7). Thus, elastin fiber analysis is likely to be highl y nonspecific for diagnosing pneumonia in the setting of acute diffuse lung injury.