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Effect of Spontaneous Breathing in APRV Mode on Respiratory Physiology of ARDS Patients
Condition(s) studied
Acute Respiratory Distress Syndrome
Investigational drug(s) / intervention(s)
APRV ventilation with low-level spontaneous breathingAPRV ventilation with high-level spontaneous breathingAPRV ventilation with fully suppressed spontaneous breathing
APRV ventilation with low-level spontaneous breathing: APRV ventilation mode, spontaneous-contributed minute-ventilation proportion maintained at 10%-30%. 30-minute stabilization before outcome measurement.
APRV ventilation with high-level spontaneous breathing: APRV ventilation mode, spontaneous-contributed minute-ventilation proportion maintained at 31%-50%. 30-minute stabilization before outcome measurement.
APRV ventilation with fully suppressed spontaneous breathing: APRV ventilation mode, spontaneous breathing fully suppressed by deep sedation (RASS-4 to -5). 30-minute stabilization before outcome measurement.
Study summary
This is a single-center, prospective, randomized, three-period crossover physiological study in adult patients with moderate-to-severe acute respiratory distress syndrome (ARDS, PaO₂/FiO₂ ≤150 mmHg). Each enrolled subject will receive all three APRV ventilation conditions in random sequence: low-level spontaneous breathing (spontaneous minute-ventilation proportion 10%-30%), high-level spontaneous breathing (31%-50%), and fully suppressed spontaneous breathing as control. A 30-minute wash-out period is set between each condition to restore unified physiological baseline. Primary outcome is ventilation-perfusion mismatch percentage (mismatch%) measured by Electrical Impedance Tomography (EIT). Secondary outcomes include EIT-derived pulmonary parameters, respiratory mechanics, hemodynamics, diaphragmatic function and safety profiles. Only short-term, reversible ventilator and sedation adjustments will be performed; routine clinical management remains unchanged throughout the trial.
Eligibility
Inclusion Criteria:
* 1\. Age ≥18 and ≤80 years old. 2. Diagnosed with moderate-to-severe ARDS according to the 2023 global ARDS definition.
3\. Within 48 hours of invasive mechanical ventilation. After 1-hour low-tidal-volume pressure-controlled ventilation following ARDSnet strategy, arterial blood gas shows PaO₂/FiO₂ ≤ 150 mmHg.
4\. Written informed consent is obtained from the patient or their legal surrogate decision-maker after full explanation of the study by the principal investigator or authorized study physician.
Exclusion Criteria:
* 1\. Refractory shock defined as persistent hyperlactatemia and/or prolonged capillary refill time, fluid-resistant, requiring norepinephrine ≥ 0.5 μg/kg/min.
2\. Severe chronic medical conditions severely affecting cardiopulmonary function: severe chronic obstructive pulmonary disease, interstitial lung disease, pulmonary embolism, right-heart failure, pulmonary hypertension, or severe arrhythmia.
3\. Radiologically confirmed bronchopleural fistula, status post lobectomy, or other major thoracic surgery.
4\. Contraindications to electrical impedance tomography (EIT): extensive chest skin injury or infection, implanted cardiac pacemaker or defibrillator, etc.
5\. Contraindications for esophageal manometry placement: esophageal obstruction, perforation, severe esophageal varices, etc.
6\. Diaphragmatic hernia, severe chest wall deformity, or significant pulmonary bullae.
7\. Significant coagulation abnormalities (PT or APTT prolonged ≥2 times upper limit of normal, or INR\>2.0) with active bleeding risk.
8\. Severe intracranial hypertension (\>20 mmHg), severe traumatic brain injury (GCS ≤8), or neuromuscular disorders.
9\. Pregnant or breastfeeding women. 10. Patients already receiving ECMO therapy. 11. Expected survival time \<24 hours judged by attending physician. 12. Body mass index (BMI) \>35 kg/m². 13. Previously enrolled in this study or participating in other interventional clinical trials.
Primary outcome measure(s)
- Ventilation-perfusion mismatch percentage (Mismatch%) — Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Ventilation-perfusion mismatch percentage (Mismatch%), calculated as the sum of dead-space percentage and shunt percentage measured by electrical impedance tomography (EIT). A composite index reflecting overall ventilation-perfusion mismatch, assessed at baseline and under three APRV experimental conditions. Unit: %
Trial sites (1)
| Facility | City | Region | Status |
|---|
| Wuhan Union Hospital, Tongji Medical College, Huazhong University of Science and Technology |
Wuhan |
Hubei |
|
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