PULMONARY INFECTION DURING THE ACUTE RESPIRATORY-DISTRESS SYNDROME

Pulmonary infection is thought to be a common complication of ARDS. We undertook this prospective study to determine the incidence of pulmon ary infection in patients with ARDS, and to evaluate the impact of nos ocomial pneumonia on severity of ARDS and on survival. Two hundred one bronchoscopies were performed in 105 patients with ARDS with retrieva l of distal airway secretions by bronchoalveolar lavage (BAL) and prot ected specimen brush (PSB). Whenever possible, bronchoscopy was perfor med at predetermined times: Day 3, Day 7, Day 14, and Day 21 after the onset of ARDS. The majority of patients were receiving antibiotics at the time of study. Changes in bacterial flora over time were determin ed by quantitative cultures of BAL and PSB. Bacterial growth was commo n, but usually at small concentrations, Only 16 patients met quantitat ive culture criteria for pneumonia (PSB greater than or equal to 10(3) cfu/ml or BAL greater than or equal to 10(4) Cfu/ml), Correlation was poor between clinical evidence of pneumonia and pneumonia by quantita tive culture criteria: clinical criteria had a very low sensitivity (2 4%) for predicting positive quantitative culture results, and a low sp ecificity (77%) for predicting negative quantitative culture results. There was no correlation between total colony counts on BAL or PSB and severity of ARDS as judged by Pa-O2/Fl(O2) ratios, days receiving ven tilation, or compliance. Furthermore, there was no correlation between bacterial growth and survival. We conclude that pneumonia defined by quantitative bacteriology is uncommon in ARDS. The potentially confoun ding role of broad-spectrum antibiotics should be studied further.