# End-expiratory lung volumes as a potential indicator for COVID-19 associated acute respiratory distress syndrome: a retrospective study

## TL;DR

This study suggests that end-expiratory lung volume (EELV) can help assess severity and monitor outcomes in patients with COVID-19-related ARDS.

## Contribution

The study introduces EELV as a potential indicator for monitoring disease progression and prognosis in CARDS patients.

## Key findings

- Survivors had significantly higher EELV, EELV/PBW, and EELV/preFRC compared to non-survivors.
- EELV correlated positively with lung volume and negatively with lesion volume from CT scans.
- EELV/PBW and EELV/preFRC remained elevated in survivors during follow-up assessments.

## Abstract

End-expiratory lung volume (EELV) has been observed to decrease in acute respiratory distress syndrome (ARDS). Yet, research investigating EELV in patients with COVID-19 associated ARDS (CARDS) remains limited. It is unclear whether EELV could serve as a potential metric for monitoring disease progression and identifying patients with ARDS at increased risk of adverse outcomes.

This retrospective study included mechanically ventilated patients diagnosed with CARDS during the initial phase of epidemic control in Shanghai. EELV was measured using the nitrogen washout-washin technique within 48 h post-intubation, followed by regular assessments every 3–4 days. Chest CT scans, performed within a 24-hour window around each EELV measurement, were analyzed using AI software. Differences in patient demographics, clinical data, respiratory mechanics, EELV, and chest CT findings were assessed using linear mixed models (LMM).

Out of the 38 patients enrolled, 26.3% survived until discharge from the ICU. In the survivor group, EELV, EELV/predicted body weight (EELV/PBW) and EELV/predicted functional residual capacity (EELV/preFRC) were significantly higher than those in the non-survivor group (survivor group vs. non-survivor group: EELV: 1455 vs. 1162 ml, P = 0.049; EELV/PBW: 24.1 vs. 18.5 ml/kg, P = 0.011; EELV/preFRC: 0.45 vs. 0.34, P = 0.005). Follow-up assessments showed a sustained elevation of EELV/PBW and EELV/preFRC among the survivors. Additionally, EELV exhibited a positive correlation with total lung volume and residual lung volume, while demonstrating a negative correlation with lesion volume determined through chest CT scans analyzed using AI software.

EELV is a useful indicator for assessing disease severity and monitoring the prognosis of patients with CARDS.

The online version contains supplementary material available at 10.1186/s12890-024-03118-2.