LOWER RESPIRATORY-TRACT COLONIZATION AND INFECTION DURING SEVERE ACUTE RESPIRATORY-DISTRESS SYNDROME - INCIDENCE AND DIAGNOSIS

Ventilator-associated pneumonia (VAP) is difficult to detect and Is of ten unsuspected duping adult respiratory distress syndrome (ARDS). We prospectively evaluated lower respiratory tract (LRT) colonization and infection in 30 patients with severe ARDS (Pa-O2/Fi(O2) ratio < 150 m m Hg), using repeated quantitative cultures of plugged telescopic cath eter (PTC) specimens taken blindly via the endotracheal tube every 48 to 72 h after onset of ARDS. All patients except one were receiving an tibiotics. When VAP was suspected on the presence of clinical criteria for infection, a repeated PTC and, when possible, a bronchoalveolar l avage (BAL) were obtained before any new antimicrobials were administe red; samples growing greater than or equal to 10(3) cfu/ml (PTC) or gr eater than or equal to 10(4) cfu/ml (BAL) were considered diagnostic o f infection. Twenty-four VAP episodes were diagnosed in 18 patients (6 0% of patients or 4.2/100 ventilator-days) a mean of 9.8 +/- 5.7 d aft er onset of ARDS. Eighteen LRT colonization episodes were recorded; 16 of 24 (66%) VAP episodes were preceded (by 2 to 6 d) by LRT colonizat ion with the same organism(s), and only two episodes of colonization w ere not followed by VAP. We conclude that although VAP is of relativel y late-onset during severe ARDS, its incidence is much higher than in other conditions and can be underestimated. Lower airways colonization is consistently followed by infection with the same organisms and pre cedes VAP in two thirds of episodes. Repeated protected specimens take n blindly may provide a useful means to predict infection and therefor e allow early antimicrobial therapy in high-risk patients with diffuse lung injury.