ARTICLE REVIEW

Early and reliable diagnosis of Ventilator-associated pneumonia (VAP) is crucial, however, it remains difficult. Chest X-ray, which is routinely used for that purpose, lacks specificity. Lung Ultrasound (LUS), a non-invasive, bedside technique, has been applied in community-acquired pneumonia, and in VAP cases to monitor aeration, nevertheless its performance had not been validated in VAP diagnosis.

Mongodi et al. conducted a prospective, international pragmatic study in three ICUs to determine whether LUS, alone and in combination with clinical and microbiological data, could improve early VAP diagnosis. The cohort consisted of 99 patients with clinically suspected VAP. Upon admission CPIS was recorded, endotracheal aspirate (EA) was collected for gram-stain (EAgram) and culture, and bronchoscopy and LUS were performed. VAP was definitely diagnosed by a positive BAL or by simultaneous presence of all clinical criteria in case of negative BAL and antibiotic start/modification within the previous 48 hours.

Patients with confirmed VAP were compared with non-VAP patients. Two LUS-based scores were calculated, the Clinical-LUS score (VPLUS) [≥2 areas with subpleural consolidations: 1 point; ≥1 areas with dynamic arborescent/linear air-bronchogram: 2 points; purulent EA: 1 point] and the Clinical-microbiological-LUS score (VPLUS-EAgram) [as above, plus positive EAgram: 2 points].

The prevalence of VAP in the cohort was 64%. For VAP diagnosis, VPLUS-EAgram ≥3 had of 77% specificity and 78 sensitivity, while VPLUS ≥2 had 69% specificity and 71% sensitivity. The combination of dynamic linear/arborescent air-bronchogram and subpleural consolidation with positive EAgram had 97% specificity and positive likelihood ratios of 6.6, while in the simultaneous presence of all VPLUS criteria both specificity and positive predictive value were 100%. The AUC for VPLUS-EAgram and VPLUS were respectively 0.832 and 0.743. Interestingly, VPLUS-EAgram AUC was higher than CPIS-EAgramAUC and equivalent to the CPIS-EAquant AUC.

The limitations of the current study include the operator-dependence of LUS, along with the small size of the cohort, the high prevalence of VAP, the lack of a gold-standard procedure for VAP diagnosis.

Take home message    
VPLUS and VPLUS-EAgram scores are easy to calculate and can be used in patients with suspected VAP to identify high-risk cases and start early antibiotics. However, further studies are needed to establish the role of this new combination approach in early VAP diagnosis and assess whether it leads to earlier prescription of antibiotics to patients who do develop VAP, while preventing antibiotic overuse to those without VAP.

This article review was submitted by ESICM Journal Review Club Members Evi Tsigou and Despoina Koulenti on behalf of the Pneumonia Working Group.

Reference

Mongodi S, Via G, Girard M, Rouquette I, Misset B, Braschi A, Mojoli F, Bouhemad B. Lung Ultrasound for Early Diagnosis of Ventilator-Associated Pneumonia, CHEST (2016), doi: 10.1016/j.chest.2015.12.012.