Morbidly obese patients undergoing open heart surgery are at increased risk of breathing problems after removal of the breathing tube due to reduced lung function and chest wall restriction following surgery. These complications may result in poor oxygenation, respiratory failure, and prolonged ICU stay.

Airway Pressure Release Ventilation (APRV) is a mechanical ventilation mode that improves lung recruitment and oxygenation. This study aims to evaluate whether the prophylactic use of APRV after ICU admission, compared with conventional lung-protective mechanical ventilation, improves oxygenation, lung function, and ICU outcomes in morbidly obese patients undergoing elective cardiac surgery.

Patients will be randomly assigned to receive either APRV or conventional ventilation during postoperative mechanical ventilation, followed by standard weaning and extubation. Outcomes include oxygenation index, lung ultrasound findings, need for reintubation, and ICU clinical outcomes.

Morbid obesity is increasingly prevalent among patients undergoing elective cardiac surgery and is associated with significant postoperative respiratory morbidity. Reduced functional residual capacity, impaired chest wall compliance, atelectasis, and diaphragmatic dysfunction are further exacerbated by median sternotomy, cardiopulmonary bypass, and postoperative pain. These factors increase the risk of hypoxemia, difficult weaning from mechanical ventilation, extubation failure, and prolonged intensive care unit (ICU) stay in this high-risk population.

Conventional postoperative mechanical ventilation strategies in obese cardiac surgery patients typically rely on lung-protective volume-controlled ventilation with moderate to high positive end-expiratory pressure (PEEP). However, despite these strategies, postoperative atelectasis and impaired oxygenation remain common, particularly in morbidly obese patients.

Airway Pressure Release Ventilation (APRV) is a pressure-controlled mode of ventilation characterized by prolonged periods of high continuous airway pressure with brief release phases, allowing spontaneous breathing throughout the ventilatory cycle. APRV has been shown to improve alveolar recruitment, ventilation-perfusion matching, and oxygenation while limiting alveolar collapse and reducing atelectrauma. Its physiological advantages suggest a potential role in preventing postoperative pulmonary complications when applied early in the ICU course.

This randomized controlled study aims to evaluate the prophylactic application of APRV initiated upon ICU admission, compared with conventional lung-protective mechanical ventilation, in morbidly obese patients undergoing elective cardiac surgery. Mechanical ventilation will be applied according to group allocation until patients meet predefined criteria for extubation. Prior to extubation, both groups will be transitioned to standardized spontaneous breathing trials using continuous positive airway pressure (CPAP) or pressure support ventilation.

The primary outcome of the study is oxygenation index measured at predefined time points, including on ICU admission, immediately prior to extubation, and after extubation. Secondary outcomes include lung ultrasound score, incidence of reintubation, duration of mechanical ventilation, ICU length of stay, postoperative pulmonary complications, and hemodynamic stability.

By focusing on early postoperative ventilation strategy rather than rescue therapy, this study seeks to determine whether prophylactic APRV can improve respiratory physiology and clinical outcomes in morbidly obese patients following elective cardiac surgery.

Inclusion Criteria:

Adult patients aged 18-65 year of both sex.

Morbidly obese patients (body mass index ≥ 40 kg/m² or ≥ 35 kg/m² with obesity-related comorbidities)

Scheduled for elective cardiac surgery (CABG, valve, or combined) requiring cardiopulmonary bypass

Planned postoperative admission to the cardiac surgical intensive care unit

Patients eligible for mechanical ventilation with planned early extubation within 6-12 hours postoperatively

Ability to provide written informed consent

Exclusion Criteria:

Severe pulmonary disease (e.g., COPD GOLD III/IV, home oxygen therapy, and pulmonary fibrosis).

Patients with history of previous spontaneous pneumothorax or postoperative pneumothorax.

Intracranial hypertension or contraindication to APRV. Hemodynamically unstable on admission (MAP less than 65 mmHg) Vasopressor/inotropic score (VIS) more than 10 Requirement for postoperative extracorporeal membrane oxygenation (ECMO) or intra-aortic balloon pump (IABP).

Inability to obtain informed consent

All data will be shared once study is completed

before 12/2026

free