Procedures for the diagnosis of pneumonia in ICU patients.

The optimal technique for diagnosing nosocomial bacterial pneumonia in critically ill patients cared for in the intensive care unit remains unclear, especially in the subgroup of patients requiring mechanical ventilation. An important advance has been the development of the protected specimen brush technique. Secretions obtained using this technique and evaluated by quantitative cultures are useful in distinguishing patients with and without pneumonia. However, this procedure has important limitations in that results are not available immediately, and in that a few false negative of false positive results may occur. Bronchoalveolar lavage has been suggested to be of value in establishing the diagnosis of pneumonia, because the cells and liquid recovered can be examined microscopically immediately after the procedure and are also suitable for quantitative culture. Microscopic identification of bacteria within cells recovered by lavage may provide a sensitive and specific means for the early and rapid diagnosis of pneumonia in this setting. The lavage technique can also be conveniently incorporated into a protocol along with quantitative culture of samples obtained using the protected specimen brush. This combination will probably improve the overall accuracy of diagnosis while allowing the administration of prompt empiric antimicrobial therapy in most patients with pneumonia.