Association between PaO2/FiO2 trajectories and survival outcomes in patients with sepsis-associated acute respiratory failure under invasive mechanical ventilation: a retrospective cohort analysis based on MIMIC-IV database.

BACKGROUND: Acute respiratory failure is common in sepsis. When severe conditions like refractory hypoxemia or persistent CO2 retention occur, invasive mechanical ventilation (IMV) is required. The PaO2/FiO2 ratio is a key indicator for assessing acute respiratory failure severity and sepsis prognosis. This study investigates the early ICU trajectory of PaO2/FiO2 in septic patients requiring IMV for acute respiratory failure and its association with 28-day mortality.

METHODS: This retrospective cohort study utilized the MIMIC-IV database to examine septic patients with acute respiratory failure receiving IMV. Group-based trajectory modeling (GBTM) classified PaO2/FiO2 trends over the first 96 h. Cox and logistic regression assessed associations between trajectory patterns and 28-day or ICU mortality.

RESULTS: Among 2270 patients, ICU mortality was 27.1% and 28-day mortality 31.2%. Five distinct PaO2/FiO2 trajectories were identified. Compared to the persistently low trajectory group, patients in trajectory 5 (initially low PaO2/FiO2 that improved and stabilized at a mildly reduced level) had significantly lower risks of 28-day mortality (HR 0.73, 95% CI 0.61-0.87) and ICU mortality (OR 0.64, 95% CI 0.50-0.81).

CONCLUSION: In patients with sepsis-related acute respiratory failure receiving invasive mechanical ventilation, early dynamic patterns of PaO2/FiO2 in the ICU are closely associated with short-term outcomes. Compared to those with persistently low oxygenation levels, patients whose PaO2/FiO2 was initially low but improved and stabilized at a mildly reduced level within 96 h exhibited significantly lower risks of ICU and 28-day all-cause mortality. PaO2/FiO2 trajectories may serve as a valuable tool for early prognostic assessment in patients with sepsis.