Intra-Abdominal Pressure, Respiratory Mechanics, and Ventilator Liberation After Emergency Major Laparotomy

This prospective observational cohort study aims to investigate the relationship between intra-abdominal pressure (IAP), respiratory system mechanics, and successful liberation from invasive mechanical ventilation in adult patients admitted to the intensive care unit (ICU) following emergency major laparotomy. Increased intra-abdominal pressure may impair respiratory mechanics by reducing chest wall compliance, increasing airway pressures, and limiting diaphragmatic movement. These physiological changes may contribute to prolonged mechanical ventilation and difficulties in ventilator liberation. The study will enroll 100 adult patients who undergo non-traumatic emergency major laparotomy with primary fascial closure and require invasive mechanical ventilation upon postoperative ICU admission. Intra-abdominal pressure will be measured using a standardized intravesical technique through an existing urinary catheter. Serial measurements will be performed during the first 48 hours after ICU admission, alongside simultaneous assessments of respiratory system mechanics, including static respiratory system compliance and driving pressure. The primary objectives are to evaluate the longitudinal association between IAP and static respiratory system compliance and to investigate whether early IAP trajectories are associated with time to successful liberation from invasive mechanical ventilation within 28 days. Secondary outcomes include driving pressure, mechanical ventilation status on day 7, extubation failure, ventilator-free days through day 28, and mortality. All clinical management decisions, including ventilator settings, sedation, spontaneous breathing trials, extubation, and tracheostomy, will remain under the responsibility of the treating ICU team. No study-directed therapeutic interventions will be performed.