Assessment of Respiratory Drive and Inspiratory Effort Across Pressure Support Levels in Patients After Major Abdominal Surgery

Not Applicable

Not yet recruiting

• Conditions: Inspiratory Effort; Mechanical Ventilation; Major Abdominal Surgeries

• Registration Number: NCT07199881
• Lead Sponsor: Mahidol University

Brief Summary

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.

Detailed Description

Not available

Study Timeline

• Status Verified: 2025-09
• Study First Submitted: 2025-09-10
• Study Start: 2025-09-20
• Study First Submitted QC: 2025-09-22
• Last Update Submitted: 2025-09-22
• Study First Posted: 2025-09-30
• Last Update Posted: 2025-09-30
• Primary Completion: 2026-09-30
• Study Completion: 2027-09-30

Recruitment & Eligibility

• Status: NOT_YET_RECRUITING
• Sex: All
• Target Recruitment: 40

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

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: SINGLE_GROUP

Primary Outcome Measures

Name	Time	Method
Respiratory drive and inspiratory effort across pressure support levels	Baseline and during protocol sessions, up to 3 days after enrollment	Respiratory drive and inspiratory effort will be assessed using airway occlusion pressure at 0.1 seconds (P0.1), maximum negative inspiratory occlusion pressure (Pocc), and the pressure muscle index (PMI). These indices are measured non-invasively via ventilator maneuvers during standardized stepwise adjustments of pressure support ventilation (baseline, ±3 cmH₂O, ±6 cmH₂O, return to baseline). The mean of three repeated measurements at each step will be analyzed.

Secondary Outcome Measures

Name	Time	Method
Incidence of ventilatory response patterns during PSV	Baseline and during protocol sessions, up to 3 days after enrollment	Ventilatory response patterns will be categorized as quasi-passive or active based on physiological criteria derived from changes in tidal volume, plateau pressure, and PMI during stepwise PSV adjustments. Patterns will be determined from individual response trends.
Duration of mechanical ventilation after protocol	Within 48 hours after extubation	Time from completion of the PSV protocol until successful extubation, measured in hours. Reintubation within 48 hours will be recorded separately.
Reintubation or non-invasive ventilation use	48 hours after extubation	Proportion of patients requiring reintubation or initiation of non-invasive ventilation within 48 hours after extubation following study participation.
Hospital discharge disposition	Through hospital stay, an average of 14-60 days	Patient's status at hospital discharge (alive vs. deceased; home vs. rehabilitation vs. long-term care).
ICU length of stay	Through ICU stay, an average of 7-21 days	Total number of days from ICU admission to ICU discharge.

Trial Locations

Locations (1)

Faculty of Medicine, Siriraj Hospital, Mahidol University; 🇹🇭 Bangkok, Bangkoknoi, Thailand