Inspiratory Effort, Major Abdominal Surgeries, Mechanical Ventilation
Conditions
Keywords
Pressure support ventilation, respiratory drive, inspiratory effort, mechanical ventilation, Major Abdominal Surgery
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.
Interventions
PROCEDUREStepwise PSV adjustment protocol
Patients will undergo standardized stepwise PSV changes (baseline, ±3 cmH₂O, ±6 cmH₂O, return to baseline), with 2-minute stabilization and repeated measurements of ventilatory parameters.
Sponsors
Siriraj Hospital
Mahidol University
Study design
Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
DIAGNOSTIC
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| 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
| Measure | Time frame | Description |
|---|---|---|
| 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. |
| ICU length of stay | Through ICU stay, an average of 7-21 days | Total number of days from ICU admission to ICU discharge. |
| 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). |
Countries
Thailand
Contacts
Primary ContactNuanprae Kitisin, MD
Backup ContactNattaya Raykateeraroj, MD
Outcome results
None listed