Prophylactic Use of APRV Before Extubation in Morbidly Obese Patients After Cardiac Surgery.

Official title

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.

Overview

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.

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.

Interventions

• 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,
• 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.

Primary outcome measures

• Oxygenation Index (OI) [Time frame: 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 (7)

• Lung Ultrasound Score (LUS) [Time frame: o 1 hour before extubation o 6 hours post extubation]
• PaO₂/FiO₂ Ratio [Time frame: 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 [Time frame: Within 48 hours after extubation]
• Duration of Mechanical Ventilation [Time frame: From ICU admission until successful extubation, assessed up to 24 hours]
• Incidence of Post-Extubation Pulmonary Complications [Time frame: Within 48 hours post-extubation]
• Number of Participants Requiring Vasopressor or Inotropic Support During APRV [Time frame: From APRV initiation until 24 hours post-extubation]
• Mean Arterial Pressure During and After APRV [Time frame: Immediately before APRV initiation 1 hour before extubation 1 hour post-extubation 3 hours post-extubation 6 hours post-extubation 24 hours post-extubation]

Eligibility criteria

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

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: No

Study design

Allocation

Randomized

Model

Parallel assignment

Masking

Single blind

Primary purpose

Prevention

Study locations

Center list to be confirmed — check the primary protocol.

Identifiers

NCT: NCT07409324 · FMASU MD288/2025

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗