Emergence of Alveolar Consolidations in Serial Lung Ultrasound and Diagnosis of Ventilator-Associated Pneumonia

Abstract

Lung ultrasound (LUS) has been reported as a promising diagnostic tool for ventilator-associated pneumonia (VAP), but patients with previous lung parenchyma commitment have been not studied. To evaluate whether the emergence of sonographic consolidations, rather than their presence, can improve the VAP diagnosis in a sample including patients with previous lung parenchyma diseases. Patients who completed 48 hours of mechanical ventilation were prospectively studied with daily LUS examinations. We checked the emergence of different consolidation types on the eve and on the day of a clinical suspicion of VAP. We elaborated an algorithm considering, sequentially, the emergence of (1) subpleural consolidations in anterior lung regions on the eve of suspicion; (2) lobar/sublobar consolidation in anterior lung regions on the day of suspicion; (3) lobar/sublobar consolidation with dynamic air bronchograms on the day of suspicion; and (4) any other lobar/sublobar consolidation on the day of suspicion in association with a positive Gram smear of endotracheal aspirate. Of the 188 included patients, 60 were suspected and 33 confirmed VAP. The presence of sonographic consolidations at the clinical suspicion had no diagnostic value for VAP. The emergence of subpleural consolidations in anterior lung regions on the eve of suspicion had specificity of 95% (95% confidence interval [CI], 79%-99%). The emergence of lobar/sublobar consolidations in anterior lung regions on the day of suspicion had specificity of 100% (95% CI, 87%-100%). The emergence of lobar/sublobar consolidations with dynamic air bronchograms on the day of suspicion had specificity of 96% (95% CI, 81%-99%). Finally, the proposed algorithm had sensitivity of 63% (95% CI, 46%-77%) and specificity of 85% (95% CI, 67%-94%) for VAP. The presence of sonographic consolidations was not accurate for VAP when patients with previous lung parenchyma commitment were included. However, serial LUS examinations detected the emergence of specific signs of VAP.