Utility of chest ultrasound in the diagnosis of ventilator-associated pneumonia in the critical care unit of a tertiary care center: a prospective observational study.

Abstract

Ventilator-associated pneumonia (VAP) is a type of nosocomial pneumonia developing in patients who are mechanically ventilated for ≥48 hours. Lung ultrasound (LUS) has been shown to be useful in evaluating various pathologic pulmonary conditions. We aimed to study the utility of chest ultrasound in the diagnosis of VAP in a critical care unit. This was a monocentric, prospective observational study carried out in the intensive care unit (ICU) of our institution. On clinical suspicion of VAP, patients were subjected to ultrasound chest (lung) examination, which was done in a supine position in six areas of each hemithorax on the same day, and endotracheal aspirate (ETA) for gram stain and aerobic culture was sent within 6 hours. The final diagnosis of VAP was made when ETA culture was positive (>105 CFU/mL). Days of mechanical ventilation, ICU stay, hospital stay, and mortality were separately recorded for monitoring outcomes. Diagnostic performance of risk factors for VAP was analyzed by parameters like sensitivity, specificity, positive predictive value, negative predictive value, and likelihood ratio (positive and negative). Concerning LUS signs, subpleural consolidations >2 had a sensitivity of 96% and specificity of 63% with an odds ratio of 51.43 in predicting VAP. Dynamic air bronchogram within consolidation was seen in 45% of patients with a sensitivity and specificity of 29% and 73%, respectively. A clinical LUS score >2 had a sensitivity of 100% in predicting VAP. LUS is a robust diagnostic tool with high sensitivity for diagnosing VAP. Clinical trials are needed to study whether LUS can be used as a tool for early diagnosis of VAP, which will help in the timely introduction of antibiotics.