# Influence of airway pressure release ventilation on pulmonary gas exchange using ventilatory ratio

## TL;DR

This study examines how APRV ventilation affects gas exchange in ARDS patients, finding improvements in oxygenation and ventilation efficiency but no survival benefit.

## Contribution

The study evaluates APRV's impact on pulmonary gas exchange using the ventilatory ratio in ARDS patients.

## Key findings

- APRV improved PaO2/FiO2 ratio and reduced ventilatory ratio in patients treated for at least 72 hours.
- No significant survival difference was found between APRV and LTVV as primary ventilation strategies.
- APRV was often used late as a rescue therapy, limiting its effectiveness.

## Abstract

The COVID-19 pandemic led to a surge in Acute Respiratory Distress Syndrome (ARDS) cases. Despite important advances in ventilation strategies, ARDS mortality remains high. Airway Pressure Release Ventilation (APRV), especially when used according to the Time-Controlled Adaptive Ventilation (TCAV) protocol, has shown potential in improving oxygenation and reducing mortality in ARDS.

This retrospective dual-center study included patients with moderate to severe ARDS, who were treated with APRV or Low Tidal Volume Ventilation (LTVV) between January 2018 and March 2022. Individuals receiving APRV for at least 72 h after previously receiving LTVV were analyzed in further detail. PaO2/FiO2 ratio and Ventilatory Ratio (VR) were measured 6, 12, 24, 48, and 72 h after transition to APRV. Statistical analyses were performed using univariate repeated measures ANOVA and chi-squared test.

Out of 107 patients, 48 received APRV. In 27 cases, APRV was applied according to TCAV-protocol. APRV was often used late in treatment or as a rescue therapy. Regarding the primary ventilation strategy, there was no significant difference in survival between APRV (44%) and LTVV (42%). In patients receiving APRV for at least 72 h after being initially ventilated with LTVV (n = 8), mean PaO2/FiO2 ratio improved significantly over time (p = 0.039), while mean VR decreased (p < 0.001).

APRV demonstrated potential in improving gas exchange and ventilation efficiency in ARDS patients, particularly when used early and according to TCAV. However, no survival benefit was observed. The study’s retrospective design and heterogeneity in APRV application limit its conclusions.