Transthoracic ultrasound in the diagnosis and follow-up of ventilator-associated pneumonia

Abstract

Context
Patients in the intensive care unit (ICU) are at risk not only from their critical illness but also from secondary processes such as nosocomial infection. Pneumonia is the second most common nosocomial infection in critically ill patients. Indeed, diagnosis of ventilator-associated pneumonia (VAP) requires a high clinical suspicion combined with bedside examination, radiographic examination, microbiological analysis of respiratory secretions, and blood test.


Aims
This study aimed to evaluate the effectiveness and accuracy of lung ultrasound for VAP diagnosis and follow-up.


Settings and design
A prospective cohort study was conducted on 74 patients, with a total number of 54 with a high likelihood of VAP and 20 with a low likelihood of VAP.


Methods and material
Mechanically ventilated patients for 48 h or more were included. We calculated the clinical pulmonary infection score and the lung ultrasound was performed within 24 h.


Statistical analysis
Data were collected and analyzed using SPSS (Statistical Package for the Social Sciences, version 20, IBM, and Armonk, New York). Quantitative data were expressed as mean ±standard deviation (SD) and compared with Student’s t-test. Nominal data were given as number (n) and percentage (%). Chi2 test was implemented on such data.


Results
Based on the clinical pulmonary infection score (CPIS) with a cutoff point of ≥6, the sensitivity of transthoracic ultrasound was 81.5%, the specificity was 82%, and the accuracy was 81.6%. Regarding sonographic signs, the highest sensitivity was for subpleural dots of consolidation (82%), then B-lines (56%), followed by pleural effusion, and air bronchogram (both 19%). The highest specificity was for air bronchogram (100%), then B-lines, and pleural effusion (both 90%), followed by subpleural dots of consolidation (80%). The positive predictive value for transthoracic ultrasound was 92%; the area under the receiver-operating characteristic (ROC) curve (AUC) for the total ultrasound score was 0.82.


Conclusions
Transthoracic ultrasound is an easy bedside tool for the diagnosis and follow-up of ventilator-associated pneumonia.