Acute Respiratory Distress SyndromeSBA-APRVNCT07798154
Effect of Spontaneous Breathing in APRV Mode on Respiratory Physiology of ARDS Patients
A study testing APRV ventilation with low-level spontaneous breathing, APRV ventilation with high-level spontaneous breathing and APRV ventilation with fully suppressed spontaneous breathing in people with Acute Respiratory Distress Syndrome, run by Union Hospital, Tongji Medical College, Huazhong University of Science and Technology at 1 site in China.
Trial 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). Read more about this study
- Who is it for?
- Ages 18 to 80 years
- Conditions the study is for
- Acute Respiratory Distress Syndrome
- What is being tested?
- APRV ventilation with low-level spontaneous breathing, APRV ventilation with high-level spontaneous breathing and APRV ventilation with fully suppressed spontaneous breathing
- Type of treatment
- Medical device
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 15 participants
- Where
- 1 siteChina
- Study dates
- 1 Oct 2026to Dec 2026
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 80 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- 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.
Who cannot join
- 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.
Show all 9Show fewer
- 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.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
China1 site
Wuhan Union Hospital, Tongji Medical College, Huazhong University of Science and Technology
Wuhan, Hubei, 430022
Xiaojing Zou, +86-27-85351606, 249126734@qq.com
About this study
Official title: A Randomized Controlled Trial Of The Effect Of Spontaneous Breathing In APRV Mode On Respiratory Physiology In Patients With Acute Respiratory Distress Syndrome
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.
Read the detailed description
Acute respiratory distress syndrome (ARDS) is a life-threatening critical respiratory illness characterized by heterogeneous pulmonary injury and severe ventilation-perfusion mismatch. Airway Pressure Release Ventilation (APRV) permits spontaneous breathing throughout the whole respiratory cycle, which may improve regional ventilation-perfusion matching and hemodynamic status. Nevertheless, excessive spontaneous breathing effort may trigger pendelluft phenomenon, augment regional lung strain and precipitate patient-self-inflicted lung injury (P-SILI). To date, the safe intensity range of spontaneous breathing during APRV for moderate-to-severe ARDS patients has not been well defined.
This single-center, randomized 3-period crossover self-controlled physiological trial enrolls ICU adult patients aged 18-80 years, diagnosed with moderate-to-severe ARDS (PaO₂/FiO₂ ≤ 150 mmHg) within 48-hours of invasive mechanical ventilation. After written informed consent obtained from legal surrogates, subjects will first receive a 60-minute baseline ventilation period following ARDSnet low-tidal-volume pressure-control ventilation strategy under deep sedation without spontaneous breathing. Subsequently, every participant will undergo three APRV intervention states in computer-generated random order: Condition A: APRV with low-intensity spontaneous breathing (spontaneous-contributed minute ventilation 10%-30%); Condition B: APRV with high-intensity spontaneous breathing (31%-50%); Condition C: APRV with fully suppressed spontaneous breathing via deep sedation (RASS -4 to -5). Each intervention maintains target spontaneous-breathing intensity for 30-minute stabilization before data collection. A mandatory 30-minute wash-out phase will be implemented between successive interventions to revert subjects back to baseline pressure-control ventilation and sedation status.
Primary endpoint is the comparison of ventilation-perfusion mismatch percentage (mismatch%, calculated as sum of dead-space fraction and shunt fraction) among three states measured by bedside EIT. Secondary endpoints contain multiple EIT quantitative indices, respiratory mechanics parameters (including esophageal-pressure-derived transpulmonary pressure), hemodynamic and right-ventricular function, diaphragmatic ultrasound indices, arterial blood gas variables. Adverse events related to respiratory, circulatory and operational procedures are closely monitored as safety outcomes.
Planned sample size is 14-16 enrolled participants to achieve 12 evaluable subjects completing all three intervention sequences considering dropout rate. All ventilator and sedation modifications are short-term and reversible; standard clinical therapeutic regimens will not be altered except for study-related procedures. After finishing all three intervention periods, ventilator and sedation settings will be returned to clinical team's discretion. Linear mixed-effect models will be applied for statistical analysis of crossover-design data.
- Conditions
- Acute Respiratory Distress Syndrome
- Being tested
- APRV ventilation with low-level spontaneous breathing, APRV ventilation with high-level spontaneous breathing, APRV ventilation with fully suppressed spontaneous breathing
- Keywords
- Airway Pressure Release Ventilation, spontaneous breathing, electrical impedance tomography, ventilation-perfusion mismatch
- Medical subject headings
- Respiratory Distress Syndrome
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
APRV ventilation with low-level spontaneous breathingDevice
APRV ventilation mode, spontaneous-contributed minute-ventilation proportion maintained at 10%-30%. 30-minute stabilization before outcome measurement.
APRV ventilation with high-level spontaneous breathingDevice
APRV ventilation mode, spontaneous-contributed minute-ventilation proportion maintained at 31%-50%. 30-minute stabilization before outcome measurement.
APRV ventilation with fully suppressed spontaneous breathingDevice
APRV ventilation mode, spontaneous breathing fully suppressed by deep sedation (RASS-4 to -5). 30-minute stabilization before outcome measurement.
| Study group | Role | What they receive |
|---|---|---|
| Low-level spontaneous breathing under APRV | Experimental | APRV ventilation with spontaneous-contributed minute-ventilation proportion maintained at 10%-30%. A stabilization period of 30 minutes is performed before data collection Receives: Device: APRV ventilation with low-level spontaneous breathing |
| High-level spontaneous breathing under APRV | Experimental | APRV ventilation with spontaneous-contributed minute-ventilation proportion maintained at 31%-50%. A stabilization period of 30 minutes is performed before data collection. Receives: Device: APRV ventilation with high-level spontaneous breathing |
| Fully suppressed spontaneous breathing under APRV | Experimental | APRV ventilation with spontaneous breathing completely suppressed by deep sedation (RASS-4 to -5). A stabilization period of 30 minutes is performed before data collection. Receives: Device: APRV ventilation with fully suppressed spontaneous breathing |
What is being measured
The primary outcome is the main question the study is designed to answer.
Ventilation-perfusion mismatch percentage (Mismatch%)
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: %
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Secondary outcomes (44)
Match percentage(match%)
Match percentage derived from electrical impedance tomography (EIT). Unit: %.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Pendelluft amplitude
Pendelluft amplitude derived from electrical impedance tomography (EIT). Unit: %.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Dead-space percentage
Dead-space percentage derived from electrical impedance tomography (EIT), assessed at baseline and under three APRV experimental conditions. Unit: %.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Shunt percentage
Intrapulmonary shunt percentage derived from electrical impedance tomography (EIT), assessed at baseline and under three APRV experimental conditions. Unit: %.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Global inhomogeneity index (GI)
Global inhomogeneity index (GI) derived from electrical impedance tomography (EIT). Unit: unitless.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period
Center of ventilation (CoV)
Center of ventilation (CoV) derived from electrical impedance tomography (EIT), assessed at baseline and under three APRV experimental conditions. Unit: %.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Tidal recruitment-derecruitment
Tidal recruitment-derecruitment (Tidal R/D) derived from electrical impedance tomography (EIT), assessed at baseline and under three APRV experimental conditions. Unit: %.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Ventilation distribution
Regional ventilation distribution derived from electrical impedance tomography (EIT), assessed at baseline and under three APRV experimental conditions. Unit: %.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Perfusion distribution
Regional pulmonary perfusion distribution derived from electrical impedance tomography (EIT), assessed at baseline and under three APRV experimental conditions. Unit: %.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Peak airway pressure (Ppeak)
Airway peak pressure (Ppeak) measured by mechanical ventilator, assessed at baseline and under three APRV experimental conditions. Unit: cmH₂O
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Plateau pressure (Pplat)
Airway plateau pressure (Pplat) obtained from end-inspiratory hold maneuver, assessed at baseline and under three APRV experimental conditions. Unit: cmH₂O.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Driving pressure (ΔP)
Driving pressure (ΔP) derived from mechanical ventilator measurements. Unit: cmH₂O.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Static respiratory system compliance (Cstat)
Static respiratory system compliance (Cstat), assessed at baseline and under three APRV experimental conditions. Unit: mL/cmH₂O.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
End-inspiratory esophageal pressure (PesI)
End-inspiratory esophageal pressure (PesI) measured by esophageal manometry, assessed at baseline and under three APRV experimental conditions. Unit: cmH₂O.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
End-expiratory esophageal pressure (PesE)
End-expiratory esophageal pressure (PesE) measured by esophageal manometry, assessed at baseline and under three APRV experimental conditions. Unit: cmH₂O
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Esophageal pressure swing (ΔPes)
Esophageal pressure swing (ΔPes) measured by esophageal manometry, assessed at baseline and under three APRV experimental conditions. Unit: cmH₂O.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
End-inspiratory transpulmonary pressure (PtpI)
End-inspiratory transpulmonary pressure (PtpI) derived from airway and esophageal pressure measurements. Unit: cmH₂O.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Transpulmonary driving pressure (ΔPtp)
Transpulmonary driving pressure (ΔPtp) derived from airway and esophageal pressure measurements. Unit: cmH₂O.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
End-expiratory transpulmonary pressure (PtpE)
End-expiratory transpulmonary pressure (PtpE) derived from airway and esophageal pressure, assessed at baseline and under three APRV experimental conditions. Unit: cmH₂O.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Esophageal pressure-time product per minute (PTPes/min)
Esophageal pressure-time product per minute (PTPes/min) read directly from the ventilator interface. Unit: cmH₂O·s/min.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Dynamic transpulmonary driving pressure (ΔPL,dyn)
Dynamic transpulmonary driving pressure (ΔPL,dyn) obtained from ventilator measurements; only measured in the presence of spontaneous breathing effort. Unit: cmH₂O.
Measured: At the end of each 30-minute APRV experimental condition (after stabilization)
Inspiratory muscle pressure (Pmus)
Inspiratory muscle pressure (Pmus) obtained from ventilator measurements; only measured in the presence of spontaneous breathing effort. Unit: cmH₂O
Measured: At the end of each 30-minute APRV experimental condition (after stabilization)
End-expiratory occlusion pressure (ΔPocc)
End-expiratory occlusion pressure (ΔPocc) obtained from ventilator measurements; only measured in the presence of spontaneous breathing effort. Unit: cmH₂O
Measured: At the end of each 30-minute APRV experimental condition (after stabilization)
Airway occlusion pressure (P0.1)
Airway occlusion pressure (P0.1) obtained from ventilator measurements; only measured in the presence of spontaneous breathing effort. Unit: cmH₂O
Measured: At the end of each 30-minute APRV experimental condition (after stabilization)
Muscular pressure index (PMI)
Muscular pressure index (PMI) obtained from ventilator measurements; only measured in the presence of spontaneous breathing effort. Unit: cmH₂O
Measured: At the end of each 30-minute APRV experimental condition (after stabilization)
Negative inspiratory force (NIF)
Negative inspiratory force (NIF) obtained from ventilator measurements; only measured in the presence of spontaneous breathing effort. Unit: cmH₂O
Measured: At the end of each 30-minute APRV experimental condition (after stabilization)
Heart rate
Heart rate from continuous bedside monitoring, assessed at baseline and under three APRV experimental conditions. Unit: beats per minute.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Mean arterial pressure (MAP)
Mean arterial pressure (MAP) measured via invasive arterial catheter, assessed at baseline and under three APRV experimental conditions. Unit: mmHg.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Vasopressor dosage (μg/kg/min)
Dosage of vasoactive medications, assessed at baseline and under three APRV experimental conditions. Unit: μg/kg/min
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Central venous pressure (CVP)
Central venous pressure (CVP), assessed at baseline and under three APRV experimental conditions. Unit: mmHg.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Right-ventricular fractional area change
Right-ventricular fractional area change measured by transthoracic echocardiography, assessed at baseline and under three APRV experimental conditions. Unit: %.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Velocity-time-integral (VTI)
Velocity-time-integral (VTI) measured by transthoracic echocardiography, assessed at baseline and under three APRV experimental conditions. Unit: cm.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Tricuspid annular plane systolic excursion (TAPSE)
Tricuspid annular plane systolic excursion (TAPSE) measured by transthoracic echocardiography, assessed at baseline and under three APRV experimental conditions. Unit: mm.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Cardiac output (CO)
Cardiac output (CO) calculated from velocity-time integral (VTI) measured by transthoracic echocardiography, assessed at baseline and under three APRV experimental conditions. Unit: L/min.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Stroke volume (SV)
Stroke volume (SV) calculated from velocity-time-integral (VTI) measured by transthoracic echocardiography, assessed at baseline and under three APRV experimental conditions. Unit: mL.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Diaphragm displacement
Diaphragm displacement measured by bedside diaphragm ultrasound, assessed in two out of the three APRV experimental conditions only when spontaneous breathing was present. Unit: mm.
Measured: At the end of 30-minute APRV experimental conditions with spontaneous breathing effort (after stabilization)
Diaphragm thickening fraction
Diaphragm thickening fraction measured by bedside diaphragm ultrasound, assessed in two out of the three APRV experimental conditions only when spontaneous breathing was present. Unit: %.
Measured: At the end of 30-minute APRV experimental conditions with spontaneous breathing effort (after stabilization)
Lung 12-zone ultrasound score
Lung ultrasound score based on 12-zone lung ultrasound assessment, assessed at baseline and under three APRV experimental conditions. Unit: unitless.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Overdistension (OD) pixel count
Pixel count of lung overdistension (OD), exported directly from electrical impedance tomography (EIT) software basic module, averaged over complete respiratory cycles within selected time interval, measured at baseline (prior to intervention, after stabilization) and at the end of each 30-minute APRV experimental condition (after stabilization). Unit: pixels.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Overdistension (OD) proportion
Proportion of lung overdistension (OD) relative to total lung-region pixels, exported directly from electrical impedance tomography (EIT) software basic module, averaged over complete respiratory cycles within selected time interval, measured at baseline (prior to intervention, after stabilization) and at the end of each 30-minute APRV experimental condition (after stabilization). Unit: %.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Recruitment (CR) pixel count
Pixel count of lung recruitment (CR), exported directly from electrical impedance tomography (EIT) software basic module, averaged over complete respiratory cycles within selected time interval, measured at baseline (prior to intervention, after stabilization) and at the end of each 30-minute APRV experimental condition (after stabilization). Unit: pixels.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Recruitment (CR) proportion
Proportion of lung recruitment (CR) relative to total lung-region pixels, exported directly from electrical impedance tomography (EIT) software basic module, averaged over complete respiratory cycles within selected time interval, measured at baseline (prior to intervention, after stabilization) and at the end of each 30-minute APRV experimental condition (after stabilization). Unit: %.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Atelectasis (AT) pixel count
Pixel count of lung atelectasis (AT), exported directly from electrical impedance tomography (EIT) software basic module, averaged over complete respiratory cycles within selected time interval, measured at baseline (prior to intervention, after stabilization) and at the end of each 30-minute APRV experimental condition (after stabilization). Unit: pixels.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Atelectasis (AT) proportion
Proportion of lung atelectasis (AT) relative to total lung-region pixels, exported directly from electrical impedance tomography (EIT) software basic module, averaged over complete respiratory cycles within selected time interval, measured at baseline (prior to intervention, after stabilization) and at the end of each 30-minute APRV experimental condition (after stabilization). Unit: %.
Measured: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted1 Sep 2026
- Study start1 Oct 2026 (estimated)
- Primary completionNov 2026 (estimated)
- Study completionDec 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Acute Respiratory Distress SyndromeStudies of the same condition, open and under way.
- More trials run by Union Hospital, Tongji Medical College, Huazhong University of Science and TechnologyThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Crossover
- Model description
- Each participant receives all three APRV ventilation conditions in random sequence with 30-minute wash-out period between successive conditions. This is a three-period crossover self-controlled physiological study
- Masking
- None (open label)
- Enrolment
- 15 participants (estimated)
Sponsor and investigators
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, XiaoJing Zou,MD, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology
- Investigators
- xiaojing zou, MD, Principal investigator, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07798154
- Sponsor's protocol ID
- PROTO-APRV-2026-01
- Other IDs
- MR-42-26-065895
- Acronym
- SBA-APRV
- Status last verified
- Aug 2026
- First submitted
- 20 Aug 2026
- Last updated
- 1 Sep 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 1 Sep 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Randomized Controlled Trial Of The Effect Of Spontaneous Breathing In APRV Mode On Respiratory Physiology In Patients With Acute Respiratory Distress Syndrome
- ClinicalTrials.gov ID
- NCT07798154
- Acronym / sponsor ID
- SBA-APRV / PROTO-APRV-2026-01
- Conditions
- Acute Respiratory Distress Syndrome
- Keywords
- Airway Pressure Release Ventilation, spontaneous breathing, electrical impedance tomography, ventilation-perfusion mismatch
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 15 participants (estimated)
- Lead sponsor
- Union Hospital, Tongji Medical College, Huazhong University of Science and TechnologyUniversity, hospital or other
- Study start
- 1 Oct 2026 (estimated)
- Primary completion
- Nov 2026 (estimated)
- Study completion
- Dec 2026 (estimated)
- First posted
- 1 Sep 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Detailed description
Acute respiratory distress syndrome (ARDS) is a life-threatening critical respiratory illness characterized by heterogeneous pulmonary injury and severe ventilation-perfusion mismatch. Airway Pressure Release Ventilation (APRV) permits spontaneous breathing throughout the whole respiratory cycle, which may improve regional ventilation-perfusion matching and hemodynamic status. Nevertheless, excessive spontaneous breathing effort may trigger pendelluft phenomenon, augment regional lung strain and precipitate patient-self-inflicted lung injury (P-SILI). To date, the safe intensity range of spontaneous breathing during APRV for moderate-to-severe ARDS patients has not been well defined.
This single-center, randomized 3-period crossover self-controlled physiological trial enrolls ICU adult patients aged 18-80 years, diagnosed with moderate-to-severe ARDS (PaO₂/FiO₂ ≤ 150 mmHg) within 48-hours of invasive mechanical ventilation. After written informed consent obtained from legal surrogates, subjects will first receive a 60-minute baseline ventilation period following ARDSnet low-tidal-volume pressure-control ventilation strategy under deep sedation without spontaneous breathing. Subsequently, every participant will undergo three APRV intervention states in computer-generated random order: Condition A: APRV with low-intensity spontaneous breathing (spontaneous-contributed minute ventilation 10%-30%); Condition B: APRV with high-intensity spontaneous breathing (31%-50%); Condition C: APRV with fully suppressed spontaneous breathing via deep sedation (RASS -4 to -5). Each intervention maintains target spontaneous-breathing intensity for 30-minute stabilization before data collection. A mandatory 30-minute wash-out phase will be implemented between successive interventions to revert subjects back to baseline pressure-control ventilation and sedation status.
Primary endpoint is the comparison of ventilation-perfusion mismatch percentage (mismatch%, calculated as sum of dead-space fraction and shunt fraction) among three states measured by bedside EIT. Secondary endpoints contain multiple EIT quantitative indices, respiratory mechanics parameters (including esophageal-pressure-derived transpulmonary pressure), hemodynamic and right-ventricular function, diaphragmatic ultrasound indices, arterial blood gas variables. Adverse events related to respiratory, circulatory and operational procedures are closely monitored as safety outcomes.
Planned sample size is 14-16 enrolled participants to achieve 12 evaluable subjects completing all three intervention sequences considering dropout rate. All ventilator and sedation modifications are short-term and reversible; standard clinical therapeutic regimens will not be altered except for study-related procedures. After finishing all three intervention periods, ventilator and sedation settings will be returned to clinical team's discretion. Linear mixed-effect models will be applied for statistical analysis of crossover-design data.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Number of arms
- 3
- Model description
- Each participant receives all three APRV ventilation conditions in random sequence with 30-minute wash-out period between successive conditions. This is a three-period crossover self-controlled physiological study
| Arm | Type | Receives |
|---|---|---|
| Low-level spontaneous breathing under APRV | Experimental | Device: APRV ventilation with low-level spontaneous breathingAPRV ventilation with spontaneous-contributed minute-ventilation proportion maintained at 10%-30%. A stabilization period of 30 minutes is performed before data collection |
| High-level spontaneous breathing under APRV | Experimental | Device: APRV ventilation with high-level spontaneous breathingAPRV ventilation with spontaneous-contributed minute-ventilation proportion maintained at 31%-50%. A stabilization period of 30 minutes is performed before data collection. |
| Fully suppressed spontaneous breathing under APRV | Experimental | Device: APRV ventilation with fully suppressed spontaneous breathingAPRV ventilation with spontaneous breathing completely suppressed by deep sedation (RASS-4 to -5). A stabilization period of 30 minutes is performed before data collection. |
Who may qualify
- Ages
- 18 to 80 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (3 listed)
- 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.
Key exclusion criteria (9 listed)
- 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.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| APRV ventilation with low-level spontaneous breathingAPRV ventilation mode, spontaneous-contributed minute-ventilation proportion maintained at 10%-30%. 30-minute stabilization before outcome measurement. | Device | Low-level spontaneous breathing under APRV |
| APRV ventilation with high-level spontaneous breathingAPRV ventilation mode, spontaneous-contributed minute-ventilation proportion maintained at 31%-50%. 30-minute stabilization before outcome measurement. | Device | High-level spontaneous breathing under APRV |
| APRV ventilation with fully suppressed spontaneous breathingAPRV ventilation mode, spontaneous breathing fully suppressed by deep sedation (RASS-4 to -5). 30-minute stabilization before outcome measurement. | Device | Fully suppressed spontaneous breathing under APRV |
Primary outcome
Ventilation-perfusion mismatch percentage (Mismatch%)
Time frame: 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: %
44 secondary outcomes
Match percentage(match%)
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Pendelluft amplitude
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Dead-space percentage
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Shunt percentage
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Global inhomogeneity index (GI)
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period
Center of ventilation (CoV)
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Tidal recruitment-derecruitment
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Ventilation distribution
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Perfusion distribution
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Peak airway pressure (Ppeak)
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Plateau pressure (Pplat)
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Driving pressure (ΔP)
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Static respiratory system compliance (Cstat)
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
End-inspiratory esophageal pressure (PesI)
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
End-expiratory esophageal pressure (PesE)
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Esophageal pressure swing (ΔPes)
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
End-inspiratory transpulmonary pressure (PtpI)
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Transpulmonary driving pressure (ΔPtp)
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
End-expiratory transpulmonary pressure (PtpE)
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Esophageal pressure-time product per minute (PTPes/min)
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Dynamic transpulmonary driving pressure (ΔPL,dyn)
Time frame: At the end of each 30-minute APRV experimental condition (after stabilization)
Inspiratory muscle pressure (Pmus)
Time frame: At the end of each 30-minute APRV experimental condition (after stabilization)
End-expiratory occlusion pressure (ΔPocc)
Time frame: At the end of each 30-minute APRV experimental condition (after stabilization)
Airway occlusion pressure (P0.1)
Time frame: At the end of each 30-minute APRV experimental condition (after stabilization)
Muscular pressure index (PMI)
Time frame: At the end of each 30-minute APRV experimental condition (after stabilization)
Negative inspiratory force (NIF)
Time frame: At the end of each 30-minute APRV experimental condition (after stabilization)
Heart rate
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Mean arterial pressure (MAP)
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Vasopressor dosage (μg/kg/min)
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Central venous pressure (CVP)
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Right-ventricular fractional area change
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Velocity-time-integral (VTI)
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Tricuspid annular plane systolic excursion (TAPSE)
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Cardiac output (CO)
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Stroke volume (SV)
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Diaphragm displacement
Time frame: At the end of 30-minute APRV experimental conditions with spontaneous breathing effort (after stabilization)
Diaphragm thickening fraction
Time frame: At the end of 30-minute APRV experimental conditions with spontaneous breathing effort (after stabilization)
Lung 12-zone ultrasound score
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Overdistension (OD) pixel count
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Overdistension (OD) proportion
Time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 1 Sep 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
xiaojing zou, MD principal investigator
Union Hospital, Tongji Medical College, Huazhong University of Science and Technology
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing APRV ventilation with low-level spontaneous breathing, APRV ventilation with high-level spontaneous breathing and APRV ventilation with fully suppressed spontaneous breathing in people with Acute Respiratory Distress Syndrome, run by Union Hospital, Tongji Medical College, Huazhong University of Science and Technology at 1 site in China.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 3 inclusion and 9 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 1 Sep 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in China. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Xiaojing Zou (+86-27-85351606, 249126734@qq.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Ventilation-perfusion mismatch percentage (Mismatch%) (time frame: Baseline and at the end of each 30-minute experimental condition during the study intervention period.). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 1 Sep 2026.