An observational study in Intra-Abdominal Hypertension, Respiratory Mechanics and Mechanical Ventilation, sponsored by Bursa Yuksek Ihtisas Training and Research Hospital. Not yet recruiting at 1 site in Turkey (Türkiye). Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-22.
Sponsored by Bursa Yuksek Ihtisas Training and Research Hospital · Observational
This prospective observational cohort study aims to investigate the relationship between intra-abdominal pressure (IAP), respiratory system mechanics, and successful liberation from invasive mechanical ventilation in adult patients admitted to the intensive care unit (ICU) following emergency major laparotomy.
Increased intra-abdominal pressure may impair respiratory mechanics by reducing chest wall compliance, increasing airway pressures, and limiting diaphragmatic movement. These physiological changes may contribute to prolonged mechanical ventilation and difficulties in ventilator liberation.
The study will enroll 100 adult patients who undergo non-traumatic emergency major laparotomy with primary fascial closure and require invasive mechanical ventilation upon postoperative ICU admission.
Intra-abdominal pressure will be measured using a standardized intravesical technique through an existing urinary catheter. Serial measurements will be performed during the first 48 hours after ICU admission, alongside simultaneous assessments of respiratory system mechanics, including static respiratory system compliance and driving pressure.
The primary objectives are to evaluate the longitudinal association between IAP and static respiratory system compliance and to investigate whether early IAP trajectories are associated with time to successful liberation from invasive mechanical ventilation within 28 days.
Secondary outcomes include driving pressure, mechanical ventilation status on day 7, extubation failure, ventilator-free days through day 28, and mortality.
All clinical management decisions, including ventilator settings, sedation, spontaneous breathing trials, extubation, and tracheostomy, will remain under the responsibility of the treating ICU team. No study-directed therapeutic interventions will be performed.
Background and Rationale:
Elevated intra-abdominal pressure (IAP) is frequently encountered in critically ill surgical patients, particularly following emergency major abdominal surgery. Intra-abdominal sepsis, intestinal edema, ileus, abdominal distension, fluid resuscitation, and primary abdominal fascial closure may contribute to increased IAP.
Intra-abdominal hypertension, generally defined as a sustained or repeated IAP of at least 12 mmHg, may adversely affect respiratory mechanics through cranial displacement of the diaphragm, reduced chest wall compliance, decreased lung volumes, and increased airway pressures.
Previous studies have demonstrated an association between intra-abdominal hypertension and mechanical ventilation. However, prospective data examining simultaneous longitudinal changes in IAP and respiratory system mechanics specifically in patients undergoing emergency major laparotomy remain limited.
Furthermore, the relationship between early postoperative IAP trajectories and successful liberation from invasive mechanical ventilation has not been adequately characterized in this patient population.
Study Design and Population:
This single-center, prospective observational cohort study will be conducted in the postoperative general surgery intensive care unit of Bursa Yuksek Ihtisas Training and Research Hospital, Turkiye.
A total of 100 adult patients undergoing non-traumatic emergency major laparotomy with primary fascial closure and requiring invasive mechanical ventilation upon postoperative ICU admission will be consecutively enrolled.
The study will not involve randomization or assignment to therapeutic interventions. All surgical procedures, mechanical ventilation strategies, sedation and analgesia, fluid administration, vasopressor treatment, spontaneous breathing trials, extubation decisions, and tracheostomy procedures will follow routine clinical practice.
Intra-Abdominal Pressure Measurements:
Intra-abdominal pressure will be measured using the standardized intravesical technique through an indwelling urinary catheter already present for routine clinical care. No additional urinary catheterization will be performed for research purposes.
Measurements will be obtained within the first hour after ICU admission and subsequently at 6, 12, 18, 24, 36, and 48 hours.
An additional measurement at 72 hours may be performed in patients who remain invasively mechanically ventilated.
The following IAP parameters will be evaluated:
Respiratory System Mechanics:
Respiratory mechanics will be assessed simultaneously with IAP measurements, preferably within five minutes of each IAP assessment.
Measurements will be obtained during periods of passive mechanical ventilation without significant spontaneous respiratory effort, coughing, or patient-ventilator asynchrony.
The following parameters will be recorded:
Static respiratory system compliance and driving pressure will be calculated using standard respiratory mechanics parameters.
Because esophageal pressure measurements will not be performed, lung and chest wall compliance will not be assessed separately. The measured compliance will therefore be defined as static respiratory system compliance.
Measurements will be postponed or omitted when reliable assessment is not possible or patient safety could be compromised.
Clinical Data Collection:
Demographic, surgical, and clinical characteristics will be prospectively recorded.
These will include age, sex, body mass index, predicted body weight, frailty status, smoking history, pulmonary and cardiovascular comorbidities, surgical diagnosis, laparotomy indication, presence and extent of peritonitis, Mannheim Peritonitis Index, surgical procedure, operative duration, and intraoperative fluid administration.
ICU variables will include Acute Physiology and Chronic Health Evaluation II (APACHE II) and Sequential Organ Failure Assessment (SOFA) scores, septic shock, vasopressor requirements, cumulative fluid balance, sedation depth, neuromuscular blocking agent use, patient position, and relevant pulmonary conditions.
Arterial blood gas parameters and laboratory results will be collected only when available from routine clinical assessments. No additional blood sampling will be performed solely for research purposes.
Ventilator Liberation and Follow-up:
Patients will be evaluated daily for readiness to undergo spontaneous breathing trials (SBTs), beginning on the first postoperative day.
SBT eligibility, performance, and failure will be assessed according to the clinical criteria described in the study protocol.
Extubation decisions will be made by the treating intensive care team based on respiratory stability, airway protection, neurological status, secretion management, and overall clinical condition.
Successful liberation from invasive mechanical ventilation will be defined as extubation followed by survival without reintubation during the subsequent seven days.
Use of high-flow nasal oxygen or noninvasive ventilation after extubation will not, by itself, be considered liberation failure.
Early extubation failure will be defined as reintubation within 48 hours after extubation.
Patients will be followed for 28 days after ICU admission to assess successful ventilator liberation, ventilator-free days, continued mechanical ventilation, tracheostomy requirements, and mortality.
Outcome Assessment:
The study has two primary outcomes.
Secondary outcomes include the association between IAP and driving pressure, invasive mechanical ventilation status on day 7, extubation failure, ventilator-free days through day 28, total duration of invasive mechanical ventilation, spontaneous breathing trial outcomes, tracheostomy requirements, ICU mortality, and 28-day mortality.
Statistical Analysis:
Continuous variables will be summarized using means and standard deviations or medians and interquartile ranges, as appropriate. Categorical variables will be presented as frequencies and percentages.
The longitudinal relationship between IAP and static respiratory system compliance will be analyzed using linear mixed-effects models accounting for repeated measurements within individual patients.
Similar models will be used to evaluate the association between IAP and driving pressure.
The association between early IAP trajectories and time to successful ventilator liberation will be analyzed using competing-risk regression, considering death as a competing event.
Logistic regression will be used for selected binary outcomes, including mechanical ventilation status on day 7 and extubation failure.
Multivariable analyses will account for potential confounders, including age, body mass index, illness severity, PEEP, fluid balance, and relevant pulmonary conditions.
Results will be reported using effect estimates, 95% confidence intervals, and corresponding p-values.
65 studies on the registry are indexed under Intra-Abdominal Hypertension; 14 are open to participants now.
This study's planned enrollment of 100 is close to the median of 98 across 32 observational studies indexed under Intra-Abdominal Hypertension.
Browse Intra-Abdominal Hypertension studies →Bursa Yuksek Ihtisas Training and Research Hospital is the lead sponsor of 50 studies on the registry; 21 are open to participants now.
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Adult patients aged 18 years or older who undergo non-traumatic emergency major laparotomy with primary abdominal fascial closure and require invasive mechanical ventilation upon postoperative admission to the general surgery intensive care unit of Bursa Yuksek Ihtisas Training and Research Hospital, Turkey, will constitute the study population. Eligible patients will be consecutively enrolled during the study period. All participants will undergo serial intra-abdominal pressure measurements and simultaneous assessment of respiratory system mechanics during the first 48 hours after ICU admission, followed by clinical outcome assessment through day 28.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria
Adult patients undergoing non-traumatic emergency major laparotomy with primary fascial closure who require invasive mechanical ventilation upon postoperative admission to the intensive care unit. All participants will undergo serial intra-abdominal pressure measurements using a standardized intravesical technique through an existing urinary catheter, together with simultaneous assessment of respiratory system mechanics during the first 48 hours after ICU admission. Patients will be followed for up to 28 days to evaluate successful liberation from invasive mechanical ventilation and other clinical outcomes. All treatment and ventilator management decisions will follow routine clinical practice without study-directed therapeutic interventions.
Other: Serial Intra-Abdominal Pressure and Respiratory Mechanics Assessment
Intra-abdominal pressure will be measured using a standardized intravesical technique through an existing urinary catheter within the first hour after postoperative ICU admission and at 6, 12, 18, 24, 36, and 48 hours. Respiratory mechanics, including plateau pressure, positive end-expiratory pressure, tidal volume, static respiratory system compliance, and driving pressure, will be assessed simultaneously. An additional measurement at 72 hours may be obtained in patients who remain invasively mechanically ventilated. These assessments are observational and will not involve modifications to routine ventilator settings or clinical management.
Association Between Intra-Abdominal Pressure and Static Respiratory System Compliance
The longitudinal association between intra-abdominal pressure (IAP, mmHg) and static respiratory system compliance (mL/cmH2O) will be evaluated using repeated simultaneous measurements obtained within the first hour after postoperative ICU admission and at 6, 12, 18, 24, 36, and 48 hours. Static respiratory system compliance will be calculated as tidal volume divided by the difference between plateau pressure and total positive end-expiratory pressure (PEEP). Linear mixed-effects models will be used to assess within-patient and between-patient associations between IAP and static respiratory system compliance, accounting for repeated measurements.
Time frame: From ICU admission through 48 hours after ICU admission
Time to Successful Liberation From Invasive Mechanical Ventilation
Time from postoperative ICU admission to successful liberation from invasive mechanical ventilation will be assessed within 28 days. Successful liberation is defined as extubation followed by survival without reintubation for seven consecutive days. The association between IAP trajectories during the first 48 hours and time to successful ventilator liberation will be evaluated using competing-risk regression, with death before successful liberation treated as a competing event.
Time frame: From ICU admission through day 28
Association Between Intra-Abdominal Pressure and Driving Pressure
The longitudinal association between intra-abdominal pressure (mmHg) and respiratory system driving pressure (cmH2O) will be evaluated using simultaneous repeated measurements. Driving pressure will be calculated as plateau pressure minus total PEEP. Linear mixed-effects models will account for repeated measurements within individual patients.
Time frame: From ICU admission through 48 hours after ICU admission
Invasive Mechanical Ventilation Requirement on Day 7
The proportion of participants who remain dependent on invasive mechanical ventilation on day 7 after postoperative ICU admission will be assessed. The association between early IAP measurements and continued ventilation will be investigated.
Time frame: Day 7 after ICU admission
Early Extubation Failure
The proportion of extubated participants requiring reintubation within 48 hours after extubation will be recorded.
Time frame: Within 48 hours after extubation, during the 28-day follow-up
Ventilator-Free Days Through Day 28
The number of days alive and free from invasive mechanical ventilation during the first 28 days after postoperative ICU admission will be calculated.
Time frame: From ICU admission through day 28
Total Duration of Invasive Mechanical Ventilation
The cumulative duration of invasive mechanical ventilation will be recorded in hours from postoperative ICU admission, including subsequent invasive ventilation episodes during follow-up.
Time frame: From ICU admission through day 28
Spontaneous Breathing Trial Failure
The proportion of participants experiencing failure of a spontaneous breathing trial (SBT) will be recorded. SBT failure will be determined according to predefined clinical criteria, including respiratory distress, oxygen desaturation, hemodynamic instability, or other signs of intolerance.
Time frame: From ICU admission through day 28
Tracheostomy Requirement
The proportion of participants requiring tracheostomy during postoperative intensive care follow-up will be recorded.
Time frame: From ICU admission through day 28
ICU Mortality Within 28 Days
The proportion of participants who die during their postoperative intensive care unit stay will be recorded.
Time frame: From ICU admission through day 28
All-Cause Mortality at Day 28
The proportion of participants who die from any cause within 28 days after postoperative ICU admission will be recorded.
Time frame: From ICU admission through day 28
Plan to share: No
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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