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NCT Number: NCT07199881

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

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.

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Key information

Conditions

Inspiratory Effort Major Abdominal Surgeries Mechanical Ventilation

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Faculty of Medicine, Siriraj Hospital, Mahidol University

Bangkok, Bangkoknoi, 10700, Thailand

Location status: Recruiting

Location contact

Nuanprae Kitisin, MD

CONTACT

[email protected]

+66896767706

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

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

Treatment and study plan

Stepwise PSV adjustment protocol

Procedure

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.

Primary outcomes

  1. 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

  1. Incidence of ventilatory response patterns during PSV

    Time frame: 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.

  2. Duration of mechanical ventilation after protocol

    Time frame: 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.

  3. Reintubation or non-invasive ventilation use

    Time frame: 48 hours after extubation

    Proportion of patients requiring reintubation or initiation of non-invasive ventilation within 48 hours after extubation following study participation.

  4. ICU length of stay

    Time frame: Through ICU stay, an average of 7-21 days

    Total number of days from ICU admission to ICU discharge.

  5. Hospital discharge disposition

    Time frame: 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).

Study contacts

Contact information is provided by the study sponsor or research team.

Nattaya Raykateeraroj, MD

CONTACT

[email protected]

+66993519963

Nuanprae Kitisin, MD

CONTACT

[email protected]

+66896767706

Sponsors and collaborators

Lead sponsor

Mahidol University

Other

Collaborators

  • Siriraj Hospital

Registry information

Important dates

Study start
2025
Primary completion
2026
Study completion
2027
First posted
Sep 30, 2025
Registry last updated
Nov 18, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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