This prospective observational single-center study will evaluate whether dynamic respiratory stress estimated by delta airway occlusion pressure deflection (Delta Pocc) during a standardized spontaneous breathing trial can predict extubation failure in mechanically ventilated adult intensive care unit patients.

Liberation from invasive mechanical ventilation is a critical step in ICU care. Although spontaneous breathing trials are routinely used to assess readiness for extubation, some patients may successfully complete the trial despite experiencing excessive respiratory effort and physiological stress, which may increase the risk of extubation failure.

This study will include adult ICU patients who have received invasive mechanical ventilation for at least 24 hours and are considered ready for a spontaneous breathing trial according to the treating clinical team. During the trial, respiratory, ventilatory, and hemodynamic variables will be recorded at predefined time points, including measurements of Delta Pocc as a non-invasive estimate of inspiratory effort and dynamic stress.

The primary outcome is extubation failure within 48 hours after extubation, defined as reintubation and/or the need for rescue non-invasive respiratory support due to post-extubation respiratory deterioration.

The study aims to determine whether this physiological measurement may improve risk stratification during weaning and complement conventional clinical decision-making.

Background

Liberation from invasive mechanical ventilation requires integration of clinical, hemodynamic, gas exchange, and physiological criteria. The spontaneous breathing trial (SBT) is a standard component of the weaning process and is commonly used to assess readiness for extubation. However, conventional clinical parameters may not fully capture the true respiratory workload experienced by the patient during the trial.

Some patients may tolerate a spontaneous breathing trial according to standard criteria while still developing excessive inspiratory effort and elevated dynamic respiratory stress, potentially predisposing them to post-extubation respiratory failure. Identifying these patients before extubation remains a major clinical challenge.

Delta airway occlusion pressure deflection (Delta Pocc), obtained during a brief expiratory occlusion maneuver, has emerged as a non-invasive physiological surrogate for inspiratory effort and dynamic transpulmonary stress. Incorporating this measurement into routine spontaneous breathing trial assessment may improve identification of patients at increased risk of extubation failure.

Objective

The primary objective of this study is to evaluate the predictive ability of Delta Pocc measured during a standardized spontaneous breathing trial to identify patients at risk of extubation failure within 48 hours.

Secondary objectives include:

To describe the temporal evolution of Delta Pocc and other respiratory physiological variables during the spontaneous breathing trial.

To compare respiratory effort and physiological measurements between patients with successful extubation and those with extubation failure.

To explore the discriminatory performance of Delta Pocc compared with conventional weaning variables.

To evaluate associations between Delta Pocc and clinically relevant outcomes including reintubation, rescue respiratory support, ICU length of stay, hospital length of stay, and mortality.

Study Design

This is a prospective, observational, single-center physiological study conducted in the adult intensive care unit of Sanatorio Parque.

The study does not modify standard clinical management. Participation will not delay extubation decisions or replace the clinical judgment of the treating team.

Study Population

Adult ICU patients receiving invasive mechanical ventilation for at least 24 hours who meet clinical criteria for a spontaneous breathing trial according to routine clinical practice will be eligible.

Inclusion Criteria Age 18 years or older Invasive mechanical ventilation for at least 24 hours Clinical indication for spontaneous breathing trial Hemodynamic and clinical stability Technical feasibility for physiological measurements Exclusion Criteria Significant hemodynamic instability Severe uncontrolled hypoxemia Major arrhythmias Agitation or patient-ventilator asynchrony preventing reliable measurements Significant air leak Technical inability to perform expiratory occlusion maneuver Limitation of life-sustaining treatment Procedures

Baseline respiratory, ventilatory, and hemodynamic variables will be recorded under current ventilatory settings.

A standardized spontaneous breathing trial will then be performed using:

Pressure support ventilation (PSV): 8 cmH2O Positive end-expiratory pressure (PEEP): 0 cmH2O

Measurements will be recorded at:

Baseline 15 minutes 30 minutes

Collected variables include:

Delta Pocc P0.1 Estimated inspiratory muscle pressure Negative inspiratory force Respiratory rate Rapid shallow breathing index Minute ventilation Peak airway pressure Mean airway pressure Oxygen saturation Heart rate Blood pressure Mean arterial pressure Fraction of inspired oxygen

Extubation decisions, preventive non-invasive respiratory support, rescue respiratory support, and reintubation will remain entirely at the discretion of the treating clinical team according to institutional practice.

Outcomes Primary Outcome

Extubation failure within 48 hours after extubation, defined as:

Reintubation, and/or Rescue non-invasive respiratory support due to respiratory deterioration after extubation Secondary Outcomes Spontaneous breathing trial success or failure Cause of spontaneous breathing trial failure Preventive non-invasive respiratory support Reintubation Rescue non-invasive respiratory support Duration of mechanical ventilation ICU length of stay Total hospital length of stay In-hospital mortality Statistical Considerations

The study is designed to evaluate the discriminative performance of Delta Pocc as a predictor of extubation failure.

Receiver operating characteristic (ROC) analysis will be used to assess predictive performance. Repeated physiological measurements will be analyzed using appropriate repeated-measures statistical methods. Multivariable logistic regression may be performed if the number of outcome events is sufficient.

A planned sample size of approximately 110 to 120 patients is expected to provide adequate event capture for exploratory predictive modeling.

Safety

This is a minimal-risk observational study. The only study-specific physiological maneuver is a brief expiratory occlusion measurement performed within standard ventilatory monitoring conditions.

No investigational drugs or devices are involved.

Inclusion Criteria:

• Age 18 years or older
• Invasive mechanical ventilation for at least 24 hours
• Clinical indication for spontaneous breathing trial according to the treating clinical team
• Hemodynamic and clinical stability
• Technical feasibility for respiratory physiological measurements, including expiratory occlusion maneuver

Exclusion Criteria:

• Significant hemodynamic instability
• Severe uncontrolled hypoxemia
• Major cardiac arrhythmias
• Agitation or patient-ventilator asynchrony preventing reliable measurements
• Significant air leak interfering with respiratory measurements
• Technical inability to perform expiratory occlusion maneuver
• Limitation of life-sustaining treatment
• Incomplete primary outcome follow-up

Adult intensive care unit patients receiving invasive mechanical ventilation for at least 24 hours who are considered clinically ready for a spontaneous breathing trial as part of routine weaning assessment.

Individual participant data are not planned to be shared because this is a single-center observational study and no formal institutional data-sharing infrastructure is currently in place. De-identified aggregate study results will be reported in scientific publications.