Postoperative continuous positive airway pressure (CPAP) can improve lung function. The risk of pulmonary complications is high after major abdominal surgery but may be reduced by prophylactic postoperative noninvasive ventilation using CPAP. This study compared the effects of auto-CPAP via a nasal mask (JPAP) and constant-CPAP via a facial mask (O2-Max Trio) on oxygenation and pulmonary function in elderly patients after major open abdominal surgery.

After being informed about the study and potential risks, all patients giving written informed consent will undergo screening period to determine eligibility for study entry.

Patients aged over 60 years, scheduled for major open abdominal surgery (i.e., gastrectomy, colectomy, proctocolectomy, or abdominal aortic aneurysm repair).

All patients received standardized anesthetic management following the established protocols of our hospital. Before induction, an epidural catheter was placed in the epidural space at thoracic T7-9 level for upper abdominal surgery and at lumbaric L1-3 level for lower abdominal surgery. A 0.2% bupivacaine solution was administered with a 5 ml bolus dosage, maintained at 5 ml/h during surgery, and the infusion rate was adjusted for pain management until postoperative day 3. General anesthesia was induced using propofol, fentanyl, and rocuronium, with maintenance using sevoflurane. Neuromuscular blockade was monitored using the train-of-four (TOF) stimulation. Fentanyl and epidural infusion rates were adjusted to maintain the Surgical Pleth Index (SPI) in the range of 40-70. Extubation was only performed when the TOF ratio was > 90%.

In the PACU, after extubation, all patients lay on their backs with a backrest tilted to 45 degrees. Postoperative pain was assessed using a numeric rating scale (NRS; 0-10) and treated with epidural boluses or IV opioids if pain exceeded NRS 3 at rest or NRS 5 during movement. Acute pain, nausea, or circulatory problems were managed and ruled out. CPAP was administered when patients were conscious and had the ability to cough and expectorate phlegm.

Patients were randomly assigned in a 1:1 ratio to either the O2-Max Trio or JPAP group through a computer-generated randomization list.

Patients in the O2-Max Trio group received CPAP via the O2-Max Trio CPAP system (Pulmodyne, Indianapolis, USA) with a facial mask that was adjusted to maintain a CPAP at 7.5 cm H2O and FiO2 30% continuously for the following 1 h.

JPAP group patients connected to the JPAP system (Metran, Saitama, Japan) via a nasal mask with the initial CPAP 2 cmH2O, then reach CPAP 7.5 cmH2O after a ramping time of 5 minutes.

Discharge from the PACU was according to a modified Aldrete discharge score. The criteria for discharge from the PACU were hemodynamic stability, SpO2 .90% with FIO2,0.4, absence of clinical signs of respiratory distress, full consciousness, and sufficient diuresis (>0.3 ml/kg/h).

Inclusion Criteria:

• Patient agrees to participate in the study
• Age 60 or older
• ASA I, II, III
• Patients underwent open abdominal surgery under general anesthesia, and extubation without complications

Exclusion Criteria:

• Upper airway deformities
• Significant bullous emphysema
• Bronchopleural fistula
• Facial deformation
• Non-epidural anesthesia
• Hemodynamic unstable
• Inability to provide consent.

the treatment allocation was unblinded to both the patient and the staffs