CLEAR Model for Predicting Ventilatory Liberation in Severe COPD

Summary

This prospective observational cohort study aims to prospectively evaluate and validate the Clinical Load, Exchange, Ability of Respiration, and Reserve (CLEAR) model for predicting sustained ventilatory liberation in patients with severe chronic obstructive pulmonary disease (COPD) receiving invasive mechanical ventilation (MV) or non-invasive ventilation (NIV). Two parallel cohorts will be studied: CLEAR-MV for patients undergoing spontaneous breathing trials (SBT) and CLEAR-NIV for patients undergoing NIV withdrawal trials. The model integrates diaphragm ultrasound evaluating diaphragm thickening fraction (DTF), ventilatory load indices including the rapid shallow breathing index (RSBI) or Clinical Load Index (CLI), gas exchange parameters including Potential of Hydrogen (pH), partial pressure of carbon dioxide (PaCO₂), and its change over time (ΔPaCO₂) combined as the Gas Exchange Index (GEI), and peripheral muscle reserve assessing rectus femoris (RF) and vastus intermedius (VI) thickness. The primary outcome is successful liberation from ventilatory support within 72 hours. Secondary outcomes include ventilatory failure within 7 days, ventilator- or NIV-free days at 28 days, and time-fixed 90-day clinical outcomes including all-cause mortality, sustained ventilatory independence, and rehospitalization for respiratory failure. Model performance will be evaluated using discrimination (area under the receiver operating characteristic curve), calibration (calibration intercept and slope), and clinical utility (decision curve analysis and net benefit) and compared with prespecified established ventilatory indices, including the Rapid Shallow Breathing Index (RSBI) and Integrative Weaning Index (IWI) in the invasive mechanical ventilation cohort, and the Heart rate, Acidosis, Consciousness, Oxygenation, and Respiratory rate (HACOR) score and the ratio of peripheral oxygen saturation to fraction of inspired oxygen divided by respiratory rate (ROX) index in the non-invasive ventilation cohort.

Eligibility

Inclusion Criteria:

* Age ≥40 years
* Confirmed or clinically diagnosed chronic obstructive pulmonary disease (COPD) based on prior spirometry or consistent clinical history
* Admission to the intensive care unit (ICU) with acute respiratory failure requiring ventilatory support
* Receiving either:

Invasive mechanical ventilation (MV), or Non-invasive ventilation (NIV)

-Considered clinically ready for ventilatory withdrawal: Undergoing spontaneous breathing trial (SBT) in the MV cohort Undergoing structured withdrawal or low-support trial in the NIV cohort

Exclusion Criteria:

* Age \<40 years
* Primary diagnosis other than COPD driving respiratory failure (e.g., isolated pneumonia, cardiogenic pulmonary edema without COPD exacerbation)
* Known neuromuscular disease affecting respiratory muscle function
* Significant chest wall deformity or restrictive thoracic disorder affecting ventilatory mechanics
* Presence of tracheostomy at baseline
* Hemodynamic instability requiring high-dose vasopressors at the time of assessment
* Inability to perform a diaphragm or muscle ultrasound (e.g., poor acoustic window, extensive dressings)
* Reduced level of consciousness precluding valid clinical assessment (outside expected NIV cohort context)
* Refusal of consent by patient or legal representative

Conditions2

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