Exhaled breath: Non-invasive diagnosis of ventilator-associated pneumonia

Abstract

Ventilator-associated pneumonia (VAP) is a hospital-acquired infection occurring in the intensive care unit (ICU). The current diagnostic standard is bronchoalveolar lavage (BAL). However, this method is invasive and time-consuming. Analysis of volatile organic compounds (VOCs) in exhaled breath is a non-invasive method that is able to diagnose many pulmonary diseases including COPD and asthma. The aim of this study was to assess the diagnostic potential of exhaled breath to diagnose VAP in ventilated critically ill patients in the ICU. A total of 100 ventilated critically ill patients who were clinically suspected of VAP were included. Using BAL microbial analysis, the clinical suspicion of VAP was confirmed in 32 patients (VAP+) and rejected in 68 patients (VAP-). Prior to the BAL procedure, an exhaled air sample was collected from each patient. The exhaled air samples were measured for the total amount of VOCs by gas chromatography – time of flight – mass spectrometry (GC- tof -MS), and subsequently analysed by multivariate statistics to extract the compounds with the most discriminative power. Statistical comparison revealed that 12 VOCs could correctly classify VAP+ and VAP- with an accuracy of 74.2% ± 4.3 and a sensitivity and specificity of 75.8% ± 5 and 73.0% ± 4.3 respectively. These results suggest that it is possible to determine the presence of VAP in ICU patients by exhaled breath. Such a quick and non-invasive diagnosis of VAP will reduce the disease burden of these patients by earlier diagnosis, but will also reduce the necessity for BAL in the ICU.