Respiratory infections in infants on mechanical ventilation: the immune response as a diagnostic aid.

A prospective study was undertaken in 41 newborn infants receiving artificial respiration for evaluation of the incidence of respiratory infections. Clinical and radiologic evidence of pneumonia was compared with the appearance of serum antibodies against antigens prepared from microorganisms isolated from bronchial aspirates, and with serum and bronchial immunoglobulin M values. A significant specific immune response was documented in 24% of the patients studied. The data indicate that by correlating the clinical and radiographic findings with specific antibodies and IgM antibody responses, it is possible to document a significant number of respiratory infections. One implication of this study is that subclinical infections may not be uncommon. The significance of the presence and changes in concentration of IgM in bronchial aspirate requires further study.