Extravascular lung water index, pulmonary vascular permeability index, and global end-diastolic volume index in mechanically ventilated COVID-19 patients requiring prone position ventilation: a preliminary retrospective study

BACKGROUND: There is a lack of data on extravascular lung water index (EVLWi), pulmonary vascular permeability index (PVPi), and global end-diastolic volume index (GEDVi) during prone position ventilation (PPV) in coronavirus disease 2019 (COVID-19) patients. The objectives of this study were to analyze trends in EVLWi, PVPi, and GEDVi during PPV and the relationships between these parameters and PaO(2)/FiO(2). METHODS: In this preliminary retrospective observational study, we performed transpulmonary thermodilution (TPTD) in seven mechanically ventilated COVID-19 patients without cardiac and pulmonary comorbidities requiring PPV for 18 hours, at specific times (30 minutes pre-PPV, 18 hours after PPV, and 3 hours after supination). EVLWi, PVPi and GEDVi were measured. The relationships between PaO(2)/FiO(2) and EVLWi, and PVPi and GEDVi values, in the supine position were analyzed by linear regression. Correlation and determination coefficients were calculated. RESULTS: EVLWi was significantly different between three time points (analysis of variance, P=0.004). After 18 hours in PPV, EVLWi was lower compared with values before PPV (12.7±0.9 ml/kg vs. 15.3±1.5 ml/kg, P=0.002). Linear regression showed that only EVLWi was correlated with PaO(2)/FiO(2) (β =–5.757; 95% confidence interval, –10.835 to –0.679; r=–0.58; R(2)=0.34; F-test P=0.029). CONCLUSIONS: EVLWi was significantly reduced after 18 hours in PPV and values measured in supine positions were correlated with PaO(2)/FiO(2). This relationship can help clinicians discriminate whether deterioration in gas exchange is related to fluid overload or disease progression. Further clinical research should evaluate the role of TPTD parameters as markers to stratify disease severity and guide clinical management.