Measuring breathing drive and effort at different pressure support levels after major abdominal surgery

Is this trial a fit for you?

A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.

What this trial studies

This is a physiological, bedside observational protocol performed in adult surgical ICU patients who remain invasively ventilated after major abdominal operations. Investigators will apply a stepwise pressure support ventilation (PSV) adjustment protocol and record noninvasive indices of respiratory drive and effort, including P0.1 (airway occlusion pressure at 100 ms), Pocc (maximum negative occlusion pressure), and the pressure muscle index (PMI). The study will quantify how patients adapt to increases and decreases in PSV and identify patterns consistent with under-assistance or over-assistance. Results are intended to inform practical PSV titration strategies that could reduce ventilator-related complications and improve clinical outcomes.

Why it matters

Who can join: the full rules

Inclusion Criteria:

* 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
* Clinically stable, with no plan for extubation within 6 hours of study enrollment, defined by all of the following: Respiratory rate \<35 breaths/min, SpO₂ ≥90%, Heart rate \<140 bpm, No visible accessory muscle use, Hemodynamically stable without escalation of vasopressor support during the past hour, Able to tolerate short-term adjustments in PSV level as per protocol

Exclusion Criteria:

* 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
* History of chronic obstructive pulmonary disease (COPD) or other obstructive lung disease

Where it's running

• Faculty of Medicine, Siriraj Hospital, Mahidol University
  Bangkok, Bangkoknoi, Thailand Recruiting

Study contacts

• Principal investigator: Nuanprae Kitisin — Department of Anesthesiology, Faculty of Medicine, Siriraj Hospital, Mahidol University
• Study coordinator: Nuanprae Kitisin, MD
• Email: nuanprae.kit@mahidol.ac.th
• Phone: +66896767706

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How to take part

1. Review the eligibility criteria above with your treating physician.
2. Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
3. Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.