Prophylactic Use of APRV Before Extubation in Morbidly Obese Patients After Cardiac Surgery. (APRV-OBESE-CS)

Prophylactic Use of Airway Pressure Release Ventilation (APRV) Prior to Extubation in Morbidly Obese Patients Undergoing Elective Cardiac Surgery: Impact on Pulmonary Function, Oxygenation, and ICU Outcomes.

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.

Study Overview

• Status: Not yet recruiting
• Conditions: Postoperative Respiratory Dysfunction; Morbid Obesity in Cardiac Surgery Patients; Mechanical Ventilation Strategies
• Intervention / Treatment: Device: Airway Pressure Release Ventilation (APRV); Device: Conventional Lung-Protective Mechanical Ventilation

Detailed Description

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.

• Study Type: Interventional
• Enrollment (Estimated): 180
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Aya M Abbas, M.B.B.CH., M.Sc; Phone Number: +201157115835 +201157115835; Email: ayaaabbass75@gmail.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: APRV Ventilation Strategy Group; Intervention Name: Airway Pressure Release Ventilation (APRV) Patients will receive airway pressure release ventilation immediately upon admission to the intensive care unit following elective cardiac surgery. APRV will be applied as the primary ventilatory mode until the patient fulfills predefined extubation readiness criteria. Prior to extubation, patients will be transitioned to continuous positive airway pressure (CPAP) with pressure support or a T-piece trial for 15-30 minutes according to ICU protocol.	Device: Airway Pressure Release Ventilation (APRV); Patients will be ventilated using the Airway Pressure Release Ventilation (APRV) mode immediately upon ICU admission. This mode will be maintained throughout the postoperative period until the patient meets the clinical criteria for extubation. with the following standardized steps: Initial APRV Settings; P High: 20-25 cm H₂O; P Low: 0 cm H₂O; T High: 4.0-6.0 seconds; T Low: 0.5-0.8 seconds; FiO₂: Adjusted to maintain SpO₂ >92% Note: P High may be titrated according to patient tolerance, Mean airway pressure (MAP), and plateau pressures. T Low is set to terminate expiratory flow at 50-75% to preserve lung recruitment. Weaning/Transition from APRV to Extubation Once oxygenation and ventilation criteria are met: T High will be gradually increased (to ≥8 sec) and P High decreased (to 10-15 cm H₂O); Then transition to CPAP/PS for 15-30 minutes Final decision for extubation will be based on successful spontaneous breathing trial (SBT) (RSBI < 105) and clinical readiness; Other Names: APRV
Active Comparator: Conventional Lung-Protective Ventilation Group; Patients will receive conventional lung-protective mechanical ventilation using synchronized intermittent mandatory ventilation (SIMV) in volume-controlled mode with a tidal volume of 6-8 mL/kg of ideal body weight and high positive end-expiratory pressure upon admission to the intensive care unit. Ventilation will be continued until extubation readiness criteria are met, followed by a CPAP with pressure support or T-piece trial for 15-30 minutes prior to extubation.	Device: Conventional Lung-Protective Mechanical Ventilation; Patients will be ventilated using the SIMV Volume-Controlled mode with lung-protective strategies: Tidal volume: 6-8 mL/kg of Ideal Body Weight (IBW); PEEP: Set at 8-12 cm H₂O, individualized based on oxygenation status; Respiratory rate: Adjusted to maintain normocapnia, typically starting from 12-18 breaths per minute; FiO₂: Titrated to maintain SpO₂ > 92%; Also transition to CPAP/PS for 15-30 minutes as a transition before extubation will be applied.; Other Names: SIMV Volume-Controlled Ventilation

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Oxygenation Index (OI)	The oxygenation index will be used as a quantitative measure of pulmonary oxygenation efficiency. It will be calculated using the formula: OI = (Mean Airway Pressure × FiO₂ × 100) / PaO₂. Changes in oxygenation index will be assessed to compare the effect of prophylactic APRV versus conventional lung-protective ventilation on pulmonary function in morbidly obese patients after elective cardiac surgery.	o Immediately before APRV initiation o 1 hour before extubation o 1 hour post-extubation o 6 hours post extubation o 24 hours post extubation

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Lung Ultrasound Score (LUS)	Lung aeration will be assessed using lung ultrasound scoring across standardized thoracic zones. Each zone will be graded based on the presence of A-lines, B-lines, or consolidation, with higher scores indicating worse aeration. The lung ultrasound score will be used to evaluate postoperative lung recruitment and aeration in both study groups.	o 1 hour before extubation o 6 hours post extubation
PaO₂/FiO₂ Ratio	The PaO₂/FiO₂ ratio will be measured as an indicator of oxygenation efficiency and gas exchange. Higher values indicate improved pulmonary oxygenation.	o Immediately before APRV initiation o 1 hour before extubation o 1 hour post-extubation o 6 hours post extubation o 24 hours post extubation
Reintubation Rate	Reintubation will be defined as the need for endotracheal intubation within 48 hours following planned extubation due to predefined clinical criteria including hypoxemia, hypercapnia, respiratory distress, altered mental status, or hemodynamic instability.	Within 48 hours after extubation
Duration of Mechanical Ventilation	Total duration of invasive mechanical ventilation from ICU admission until successful extubation.	From ICU admission until successful extubation, assessed up to 24 hours
Incidence of Post-Extubation Pulmonary Complications	Includes: Hypoxemia (SpO₂ <90% ); Use of noninvasive ventilation (NIV) support; Development of pulmonary edema or new radiographic infiltrates; Need for rescue bronchodilators or diuretics	Within 48 hours post-extubation
Number of Participants Requiring Vasopressor or Inotropic Support During APRV	The number of participants who require initiation or escalation of vasopressor or inotropic support to maintain adequate hemodynamics (defined as mean arterial pressure ≥65 mmHg) during and after application of airway pressure release ventilation (APRV).	From APRV initiation until 24 hours post-extubation
Mean Arterial Pressure During and After APRV	Mean arterial pressure (MAP (mmHg)), measured invasively, will be recorded to assess hemodynamic stability during and after APRV application.	Immediately before APRV initiation 1 hour before extubation 1 hour post-extubation 3 hours post-extubation 6 hours post-extubation 24 hours post-extubation

Collaborators and Investigators

• Sponsor: Ain Shams University
• Investigators: Principal Investigator: Aya M Abbas, M.B.B.CH., M.Sc, Ain Shams University

Study record dates

Study Major Dates

• Study Start (Estimated): February 1, 2026
• Primary Completion (Estimated): October 1, 2026
• Study Completion (Estimated): November 1, 2026

Study Registration Dates

• First Submitted: January 24, 2026
• First Submitted That Met QC Criteria: February 8, 2026
• First Posted (Actual): February 13, 2026

Study Record Updates

• Last Update Posted (Actual): February 13, 2026
• Last Update Submitted That Met QC Criteria: February 8, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: Morbid Obesity; Cardiac Surgery; Airway Pressure Release Ventilation; Oxygenation; Lung Ultrasound; Postoperative Ventilation
• Additional Relevant MeSH Terms: Nutrition Disorders; Overnutrition; Body Weight; Overweight; Obesity; Pathological Conditions, Signs and Symptoms; Nutritional and Metabolic Diseases; Signs and Symptoms; Obesity, Morbid; Therapeutics; Airway Management; Respiratory Therapy; Positive-Pressure Respiration; Respiration, Artificial; Continuous Positive Airway Pressure
• Other Study ID Numbers: FMASU MD288/2025

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: All data will be shared once study is completed
• IPD Sharing Time Frame: before 12/2026
• IPD Sharing Access Criteria: free
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF; CSR

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No