This physiological observational study will assess respiratory drive and inspiratory effort across varying levels of pressure support ventilation (PSV) in adult surgical ICU (SICU) patients after major abdominal surgery. By using non-invasive bedside indices (airway occlusion pressure at 100 ms after the onset of inspiration \[P0.1\], maximum negative occlusion pressure \[Pocc\], and pressure muscle index \[PMI\]), we aim to quantify how patients adapt to changes in ventilatory support and determine patterns of under- and over-assistance. Findings may inform optimal titration of PSV to reduce complications and improve clinical outcomes.
Adult patients (≥18 years) admitted to the surgical ICU
Recent major abdominal surgery (intra-peritoneal operation without primary thoracic involvement, including luminal resection and/or resection of a gastrointestinal solid organ) requiring postoperative ICU care
Receiving invasive mechanical ventilation in pressure support ventilation (PSV) mode at the time of enrollment
Duration of invasive mechanical ventilation >48 hours
Known neuromuscular disease affecting respiratory muscle function
Hemodynamic instability requiring escalation of vasopressor support
Severe hypoxemic respiratory failure requiring Positive End-Expiratory Pressure (PEEP) >10 cmH₂O or FiO₂ >60%
Deep sedation (Richmond Agitation-Sedation Scale [RASS] score < -3) or ongoing neuromuscular blockade
Mahidol University
Lead sponsor
Siriraj Hospital
Collaborator