Relationship of Extravascular Lung Water and Pulmonary Vascular Permeability to Respiratory Mechanics in Patients with COVID-19-Induced ARDS

Abstract

During acute respiratory distress syndrome (ARDS), the increase in pulmonary vascular permeability and lung water induced by pulmonary inflammation may be related to altered lung compliance. A better understanding of the interactions between respiratory mechanics variables and lung water or capillary permeability would allow a more personalized monitoring and adaptation of therapies for patients with ARDS. Therefore, our main objective was to investigate the relationship between extravascular lung water (EVLW) and/or pulmonary vascular permeability index (PVPI) and respiratory mechanic variables in patients with COVID-19-induced ARDS. This is a retrospective observational study from prospectively collected data in a cohort of 107 critically ill patients with COVID-19-induced ARDS from March 2020 to May 2021. We analyzed relationships between variables using repeated measurements correlations. We found no clinically relevant correlations between EVLW and the respiratory mechanics variables (driving pressure (correlation coefficient [CI 95%]: 0.017 [-0.064; 0.098]), plateau pressure (0.123 [0.043; 0.202]), respiratory system compliance (-0.003 [-0.084; 0.079]) or positive end-expiratory pressure (0.203 [0.126; 0.278])). Similarly, there were no relevant correlations between PVPI and these same respiratory mechanics variables (0.051 [-0.131; 0.035], 0.059 [-0.022; 0.140], 0.072 [-0.090; 0.153] and 0.22 [0.141; 0.293], respectively). In a cohort of patients with COVID-19-induced ARDS, EVLW and PVPI values are independent from respiratory system compliance and driving pressure. Optimal monitoring of these patients should combine both respiratory and TPTD variables.

Keywords: SARS-CoV-2; acute respiratory distress syndrome; driving pressure; lung compliance; mechanical ventilation; transpulmonary thermodilution.

Figure 1

Flowchart. ARDS: acute respiratory distress syndrome; ECMO: extracorporeal membrane oxygenation; ICU: Intensive Care Unit; TPTD: transpulmonary thermodilution.

Figure 2

Boxplot showing time evolution of extravascular lung water indexed for ideal body weight (EVLWi) (A), pulmonary vascular permeability index (PVPI) (B) and driving pressure (C) from the day of intubation to the 10th day.

Figure 3

Repeated measures correlation between extravascular lung water indexed for ideal body weight (EVLWi) and compliance of the respiratory system (Crs) (A), EVLWi and driving pressure (B), pulmonary vascular permeability index (PVPI) and Crs (C) and between PVPI and driving pressure (D). The data of each participant and the corresponding regression line are shown in a different color. Multiple points of the same color represent different measurements performed on the same patient. We estimated the common regression slope for all points in the diagram, and the parallel regression lines are fitted to each participant’s data according to their corresponding color.