Once patients' CPOT score reaches 0, intubated patients will receive continuous high-frequency oscillation (CHFO) therapy three times daily, with 8-hour intervals and 10-minute sessions. Extubated patients will receive CHFO and continuous positive expiratory pressure (CPEP) therapy twice daily, with 12-hour intervals and 10-minute sessions.

Participants in the control group will only receive standard medical, nursing, and allied healthcare, with daily decisions made without the use of protocols. This includes spontaneous breathing and awakening trials as decided by the attending intensivist, ad hoc management of pain and delirium, and once or twice daily passive and active exercises determined by the physiotherapist, with patients typically remaining in bed if on ventilation.

Once patients' CPOT score reaches 0, intubated patients will receive continuous high-frequency oscillation (CHFO) therapy three times daily, with 8-hour intervals and 10-minute sessions. Extubated patients will receive CHFO and continuous positive expiratory pressure (CPEP) therapy twice daily, with 12-hour intervals and 10-minute sessions.

The severity of PPCs within 7 postoperative days will be assessed using an ordinal scale from 0 to 5, based on a modified definition of PPCs. Grade 0 indicated no symptoms, grade 4 represented reintubation or invasive mechanical ventilation for 48 hours or more and grade 5 indicated death before hospital discharge. PPCs occurrence and severity will be evaluated daily until 7 postoperative days or hospital discharge, using the worst score during the hospital stay for the primary analysis. Bedside chest radiographs will be performed on the first postoperative day, followed by echocardiograms on the second and third days, in addition to those requested by attending physicians.