Comparison between positive end expiratory pressure guided by stress index and low PEEP/FiO2 table in moderate to severe ARDS

<bold>Background:</bold> Acute Respiratory Distress Syndrome (ARDS) is a high-mortality critical illness. Optimal positive end-expiratory pressure (PEEP) is a key factor in reducing lung injury and improving oxygenation. Several studies suggest that setting PEEP using the Stress Index (SI) may prevent tidal recruitment or hyperinflation, yet its impact on clinical outcomes, physiology, and oxygenation remains unclear. <bold>Methods:</bold> This retrospective study included patients meeting the Berlin definition of moderate to severe ARDS within 24 hours of intubation. Optimal PEEP was determined using either a low PEEP/FiO2 table or SI, with comparisons made between the two groups in mortality rates, outcomes, and respiratory and arterial blood gas values. <bold>Results:</bold> A total of 79 patients were included in the SI group, and 94 patients were included in the Low-PEEP group. The hospital mortality rate was lower in the former compared to the latter, but there was no statistically significant difference between the two groups (27.8% vs. 40.4%, p=0.083). Additional analysis demonstrated significant improvements in lung physiology pressure, compliance, and oxygenation values in the SI group compared to the Low-PEEP group, particularly in patients with moderate ARDS during the early course of the disease. <bold>Conclusion:</bold> In patients with moderate to severe ARDS, using stress index to set Optimal PEEP is a feasible strategy. Compared to the ARDSnet's Low PEEP/FiO2 table, this method did not yield a significant difference in mortality rates. However, it was associated with improvements in lung physiology and oxygenation. <bold>Keywords:</bold> Acute Respiratory Distress Syndrome; Stress index; Optimal PEEP