This retrospective study investigated the impact of applying moderate versus lower positive end-expiratory pressure (PEEP) in the early postoperative period for cardiac surgery patients in the ICU. It involved 334 patients, with 102 receiving moderate PEEP (≥ 7 cm H2O). After propensity-score matching, the moderate PEEP group showed marginally shorter mechanical ventilation durations and significantly better oxygenation compared to the lower PEEP group, without affecting ICU length of stay or the need for prone positioning. The findings suggest that moderate PEEP could facilitate earlier mechanical ventilation liberation due to improved oxygenation in selected cardiac surgery patients.