Postoperative respiratory failure (PORF) remains a critical driver of morbidity, mortality, and incremental care costs in surgical populations. Traditional escalation often involves invasive mechanical ventilation, which is associated with ventilator-associated pneumonia (VAP), prolonged intensive care unit (ICU) stays, and increased resource burden.

Noninvasive ventilation (NIV) and high-flow nasal cannula (HFNC) have both been shown to improve oxygen levels effectively and reduce the need for reintubation in various patient groups. However, head-to-head data in patients with obstructive or restrictive pulmonary function (PORF) are scarce.

This protocol employs a robust and scalable design to generate high-quality evidence, empower perioperative stakeholders, and optimize patient-centric respiratory strategies. We hypothesize that NIV will reduce 72-hour reintubation rates compared to HFNC, translating into shorter ICU stays and lower costs.

Methodology & Operational Workflow

• Screening & Consent Identify eligible patients in the post-anesthesia care unit (PACU) or ICU. Obtain informed consent from the patient or legal surrogate.
• Baseline Assessment The baseline assessment includes demographics, comorbidities, and surgical data, as well as baseline arterial blood gases (ABG), vital signs, and comfort scores.
• Randomization & Initiation Allocate via a secure web-based randomization module. Initiate assigned respiratory support within 30 minutes of notification.
• Monitoring & Data Collection The patient is receiving continuous pulse oximetry and respiratory rate monitoring.

ABGs and fraction of inspired oxygen (FIO2) at 1 hour, 6 hours, and 24 hours. Comfort scores every six hours. Record interface-related adverse events.

- Escalation Criteria The patient exhibits persistent partial arterial oxygen pressure/fraction of inspired oxygen ratio (PaO2/FiO2) levels of less than 100, even at maximal settings.

Hemodynamic instability occurs due to the use of new-onset vasopressors. Deterioration leading to invasive ventilation → classified as "reintubation."

• Weaning Protocol. Transition to standard oxygen therapy when the flow or pressure is minimal.
• Follow-Up & Discharge Track ICU length of stay (LOS), hospital LOS, and ventilation-free days (VFD). Keep a record of the 30-day survival rate and any readmissions.
• Statistical Analysis Plan Primary Endpoint: Compare reintubation rates using a χ² test; report the risk difference and 95% confidence interval.
• Missing Data: Multiple imputation for datasets with ≤ 5% missing data; sensitivity analysis for worst-case scenarios.
• Interim Analysis: After 50% enrollment, the Data Safety and Monitoring Board (DSMB) reviews efficacy and futility, using O'Brien-Fleming boundaries.

Inclusion criteria:

• Age above 18 years
• within 48 hours after major surgery
• PAO2/FIO2 less than 200
• Signs of respiratory distress and respiratory rate (RR) more than 25 cycles/minute

Exclusion Criteria:

• Age below 18 years
• Pregnant ladies
• Orofacial trauma or burns
• Active Gastrointestinal bleeding

De-identified individual participant data supporting the primary and secondary outcomes, along with accompanying data dictionaries and the statistical analysis plan, will be made available by Assiut University's institutional data-sharing policies.

6-36 months after publication.

Data will be accessible 6-36 months after publication to qualified researchers upon submission of a study proposal, approval by the University Research Ethics Committee, and execution of a data-use agreement.