• K E Shepherd, C S Faulkner, and E N Brown.
• Department of Anaesthesia, Harvard Medical School, Massachusetts General Hospital, Boston 02114, USA.
• J Trauma. 1995 Mar 1; 38 (3): 375-8.

ObjectiveThe evaluation of various techniques to diagnose or exclude ventilator-associated bacterial pneumonia has been a focus of much research. One such technique involves elastin fiber detection. It has been inferred from previous work that 40% potassium hydroxide preparations of respiratory secretions that demonstrate elastin fibers have a 100% specificity in diagnosing bacterial pneumonia in intubated, mechanically ventilated patients without acute diffuse lung injury. The purpose of this investigation was to ascertain if elastin fibers might be detected in respiratory secretions in acute, diffuse lung injury in the absence of pneumonia (i.e., assess specificity).DesignAn animal model using a standardized smoke inhalation protocol to cause acute, diffuse lung injury was used.Materials And MethodsRespiratory secretions collected from the endotracheal tubes from eight sheep that underwent the standardized smoke inhalation protocol and were examined with 40% potassium hydroxide. Histologic data were obtained from autopsy to diagnose or exclude lung injury and pneumonia.Measurement And Main ResultsWe found six (false) positive elastin fiber preparations in the absence of histologic pneumonia. Specificity was 0.25.ConclusionsWe concluded that seeing these results, given a true specificity of 0.99 inferred from previous work, is highly improbable with a probability of 2.74 x 10(-7). Thus, elastin fiber analysis is likely to be highly nonspecific for diagnosing pneumonia in the setting of acute diffuse lung injury.

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