Effect of APRV and LTV on Lung Ventilation and Perfusion in Patients With Moderate-to-severe ARDS

Study Overview
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Brief Summary
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Low tidal volume ventilation (LTV) has been proposed and widely used in patients with acute respiratory distress syndrome (ARDS) to prevent ventilator-induced lung injury (VILI) and mitigate its effects. The LTV strategy is intended to protect the baby lung from overdistension while simultaneously allowing acutely injured tissue to continually collapse. Airway pressure release ventilation (APRV) is a highly effective strategy improving lung recruitment and oxygenation in clinical studies, but its effects on lung injury and mortality is debatable. Animal studies revealed that APRV could normalize post-injury heterogeneity and reduce the risk of VILI. Our objective was to investigate the impact of APRV and LTV on regional ventilation and perfusion distribution in ARDS patients by electrical impedance tomography (EIT).

Official Title
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Effect of APRV and LTV on Lung Ventilation and Perfusion in Patients With Moderate-to-severe ARDS: a Single-center, Pilot Randomized Controlled Study

Conditions
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Acute Respiratory Distress Syndrome

Intervention / Treatment
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* Device: APRV
* Device: LTV


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients aged ≥18 and ≤80 years; Moderate-to-severe ARDS patients according to the Berlin definition; Endotracheal mechanical ventilation ≤48 h before enrollment; Expected to require continuous invasive mechanical ventilation ≥72 h. Exclusion Criteria: Severe chronic obstructive pulmonary disease, severe asthma, pulmonary bulla, subcutaneous emphysema, mediastinal emphysema, etc; Contraindications to the use of electrical impedance tomography (e.g., chest surgical wounds dressing or presence of pacemaker)； Pulmonary interstitial lesions； End-stage of chronic disease, with an expected survival period of <6 months； Body mass index >35 kg/m2; Refractory shock； Intracranial hypertension； Pregnant and parturient woman； Intra-abdominal pressure persisted > 20 mmHg and could not be relieved within 24 hours； Severe thoracic deformity； Severe cardiac dysfunction； Atrial fibrillation and other malignant arrhythmias that seriously affect cardiac output； Pulmonary embolism； Extracorporeal membrane oxygenation is needed； Prone positioning was performed before randomization； Patients who have participated in other clinical trials within 30 days； Patients who have not signed informed consent.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: APRV Group<br>Patients with moderate-to-severe ARDS were supported with APRV. | Device: APRV<br>* Patients with moderate-to-severe ARDS were supported with APRV.<br>|
| Active Comparator: LTV Group<br>Patients with moderate-to-severe ARDS were supported with LTV. | Device: LTV<br>* Patients with moderate-to-severe ARDS were supported with LTV.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Lung ventilation/perfusion matching | Lung ventilation/perfusion matching assessed by EIT | 24hour | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Lung ventilation distrubution | Lung ventilation distrubution assessed by EIT | up to 72hour | 
| Lung perfusion distrubution | Lung perfusion distrubution assessed by EIT | up to 72hour | 
| Dead-space% and shunting% | Lung Dead-space% and shunting% assessed by EIT | up to 72hour | 
| Oxygenation index | Oxygenation index=Arterial partial pressure of oxygen /fraction of inspired oxygen | up to 72hour | 
| Arterial partial pressure of carbon dioxide (PaCO2) | PaCO2 is one of the key indicators of pulmonary ventilation which can be obtained from arterial blood gas analysis. | up to 72hour | 
| Static respiratory compliance (Crs) | Crs=tidal volume/driving pressure | up to 72hour | 
| Cardiac output | Cardiac output assessed by echocardiography | up to 72hour | 
| Right ventricular function | Right ventricular function assessed by echocardiography | up to 72hour | 
| Ventilator free days | 28d-ventilator free days after randomization | up to 28days | 
| Duration of Intensive care units stay | 28d-duration of Intensive care units stay after randomization | up to 28days | 
| Mortality after randomization | 28d-all-cause mortality | up to 28days |