Airway Pressure Release Ventilation as a Rescue Ventilatory Strategy in COVID-19 Patients

INTRODUCTION Airway Pressure Release Ventilation (APRV) is a pressure controlled intermittent mandatory mode of ventilation characterized by inverse ratio ventilation and high mean airway pressure. Several studies have showed that APRV can improve oxygenation and lung recruitment in patients with ARDS. Although most patients with COVID-19 meet the Berlin criteria, hypoxic respiratory failure due to COVID-19 may differ from traditional ARDS as patients often present with severe, refractory hypoxemia and significant variation in respiratory system compliance. To date, no studies investigating APRV in this population have been published.The aim of this study was to evaluate the effectiveness of APRV as a rescue mode of ventilation in critically ill patients diagnosed with COVID-19 and refractory hypoxemia.METHODS We conducted a retrospective analysis of patients admitted with COVID-19 who developed refractory hypoxemia (PaO2/FIO2 ratio (P/F ratio) <200) while on mechanical ventilation and were treated with a trial of APRV for at least 8 hours. P/F ratio, ventilatory ratio and ventilation outputs before and during APRV were compared.Student's t-test and Wilcoxon signed-rank test were used to compare parametric and nonparametric data, respectively.RESULTS There were 60 patients who met the inclusion criteria. Mean age was 65, 36.6% of the patients were female and in-hospital mortality was 80%. We found that APRV significantly improved the P/F ratio (103 [75-154.23] vs 131.75 [94.15-221, p 0.0001]) and decreased the FiO2 requirements (80[60-100] vs 100[75-100], p 0.0034). PaCO2 (45.8 [41-56.75]mmHg vs 54[42-73]mmHg p 0.0051), and Ventilatory ratio (2.32 [1.92-3.15] vs 2.85 [2.07-3.85], p 0.0054) were also improved during the APRV trial. There was an increase in tidal volume per predicted body weight during APRV (7.86 [7.06-9.85] mL/Kg vs 6.58 [5.69-7.86] mL/Kg, p< 0.0001]) and a decrease in total minute ventilation (10.87±3.11 L/min vs 12.39±2.99 L/min, p 0.0005). On multivariate analysis, higher I:E and airway pressure were associated with greater improvement of P/F ratio.CONCLUSION Patients with COVID-19 and severe hypoxemia have a high in-hospital mortality.APRV may benefit these patients as it maximizes alveolar recruitment resulting in improved oxygenation, alveolar ventilation and CO2 clearance.These effects are more pronounced for higher airway pressure and I:E ratio. APRV was associated with an increase in tidal volume.However, tidal volumes remained within the recommended limits of lung protective ventilation.This study contributes to the growing evidence on the positive effects of APRV on oxygenation and ventilation.Prospective studies are urgently needed to evaluate the potential benefits of APRV on clinical outcomes in patients with COVID-19 and severe hypoxemia.