Assessment of Respiratory Drive and Inspiratory Effort Across Pressure Support Levels in Patients After Major Abdominal Surgery
Trial Snapshot
- Phase
- Not Applicable
- Status
- Recruiting
- Sponsor
- Mahidol University
- Enrollment
- 40
- Locations
- 1
- Primary Endpoint
- Respiratory drive and inspiratory effort across pressure support levels
Study Overview
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.
Study Design
- Study Type
- Interventional
- Allocation
- Na
- Intervention Model
- Single Group
- Primary Purpose
- Diagnostic
- Masking
- None
Eligibility Criteria
- Ages
- 18 Years to — (Adult, Older Adult)
- Sex
- All
- Accepts Healthy Volunteers
- No
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
Arms & Interventions
Single Cohort (Postoperative SICU patients on PSV >48h)
Adult patients admitted to the surgical ICU after major abdominal surgery who remain on pressure support ventilation (PSV) for more than 48 hours. Each participant will undergo a standardized stepwise protocol of PSV adjustment (baseline, -6 cmH₂O, -3 cmH₂O, +3 cmH₂O, +6 cmH₂O, return to baseline). At each step, a 2-minute stabilization is followed by repeated measurements of respiratory drive and inspiratory effort indices (P0.1, Pocc, PMI) and ventilatory parameters.
Intervention: Stepwise PSV adjustment protocol (Procedure)
Outcomes
Primary Outcomes
Respiratory drive and inspiratory effort across pressure support levels
Time Frame: 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.
Respiratory drive and inspiratory effort across pressure support levels
Time Frame: 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 Outcomes
- Reintubation or non-invasive ventilation use(48 hours after extubation)
- ICU length of stay(Through ICU stay, an average of 7-21 days)
- Hospital discharge disposition(Through hospital stay, an average of 14-60 days)
- Incidence of ventilatory response patterns during PSV(Baseline and during protocol sessions, up to 3 days after enrollment)
- Duration of mechanical ventilation after protocol(Within 48 hours after extubation)
- Incidence of ventilatory response patterns during PSV(Baseline and during protocol sessions, up to 3 days after enrollment)
- Duration of mechanical ventilation after protocol(Within 48 hours after extubation)
- Reintubation or non-invasive ventilation use(48 hours after extubation)
- Hospital discharge disposition(Through hospital stay, an average of 14-60 days)
- ICU length of stay(Through ICU stay, an average of 7-21 days)