Evaluate the Effect of Prone Ventilation on Ventilated-blood Flow Ratio in Patients With ARDS by EIT

Study Overview
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Brief Summary
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Patients with ARDS often suffer a gravity-dependent alveolar collapse, resulting in a reduction of tidal volume, residual alveolar excessive distension, and ventilator-related lung injury(VILI) induced by unreasonable ventilator setting.Prone ventilation (PPV) improves the gravity-dependent alveolar ventilation and promotes lung recruitment in the gravity-dependent area and improves lung compliance. Previous studies showed that prolonged PPV combined with low tidal volume(LTV) lung protected ventilation can significantly reduce the mortality of patients with moderate to severe ARDS.Although more than 60% of patients with moderate to severe ARDS due to COVID-19 has been widely implemented PPV,studies showed an improvement in oxygenation in patients with ARDS(the P/F radio improved by more than 20% before and after PPV) was 9-77%, that is, That is, some patients are unresponsive to PPV. In addition, some patients showed CO2 responsiveness after PPV(ventilation rate (VR) decreased significantly after PPV).The tools for monitoring the effects of PPV on ventilation and blood flow at bedside are still lacking, Electrical impedance tomography (EIT) is a non-invasive, non-radiative, real-time bedside lung imaging technique that can monitor local lung ventilation distribution. This study intends to use EIT to evaluate pulmonary ventilation, blood flow distribution and local V/Q ratio before and after PPV, as well as to monitor the changes in pulmonary physiology before and after PPV, explore the mechanism of PPV improving oxygenation by combined with the changes in oxygenation, and explore the factors that predict and affect PPV responsiveness.

Detailed Description
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Acute respiratory distress syndrome (ARDS) is presented as acute hypoxemia and pulmonary edema due to the increased permeability of alveolar capillaries. Endothelial damage injury and swelling, microthrombosis, and hypoxic pulmonary vasoconstriction can lead to low pulmonary blood vessels perfusion and even occlusion, while patients with ARDS often suffer a gravity-dependent alveolar collapse, resulting in a reduction of tidal volume, residual alveolar excessive distension, and ventilator-related lung injury(VILI) induced by unreasonable ventilator setting.Prone ventilation (PPV) improves the gravity-dependent alveolar ventilation and promotes lung recruitment in the gravity-dependent area and improves lung compliance. Besides, pulmonary blood perfusion is less affected by gravity distribution, thus the improvement of gravity-dependent alveolar ventilation can significantly reduce shunt, and lung heterogeneity and improve V/Q radio. Previous studies showed that prolonged PPV combined with low tidal volume lung protected ventilation can significantly reduce the mortality of patients with moderate to severe ARDS.Although more than 60% of patients with moderate to severe ARDS due to COVID-19 has been widely implemented PPV,studies showed an improvement in oxygenation in patients with ARDS(the P/F radio improved by more than 20% before and after PPV) was 9-77%, that is, That is, some patients are unresponsive to PPV. In addition, some patients showed CO2 responsiveness after PPV (ventilation rate (VR) decreased significantly after PPV).The tools for monitoring the effects of PPV on ventilation and blood flow at bedside are still lacking, Electrical impedance tomography (EIT) is a non-invasive, non-radiative, real-time bedside lung imaging technique that can monitor local lung ventilation distribution. By injecting hypertonic saline through a central vein catheter, we can obtain lung perfusion images to indicate local lung blood flow distribution. In addition, combined with lung ventilation images, we can evaluate the pulmonary shunt, dead space, V/Q ratio, to better clarify the physiological and pathological status of lung.This study intends to use EIT to evaluate pulmonary ventilation, blood flow distribution and local V/Q ratio before and after PPV, as well as to monitor the changes in pulmonary physiology before and after PPV, explore the mechanism of PPV improving oxygenation by combined with the changes in oxygenation, and explore the factors that predict and affect PPV responsiveness.

Official Title
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Evaluate the Effect of Prone Ventilation on Ventilated-blood Flow Ratio in Patients With Acute Respiratory Distress Syndrome by Electrical Impedance Tomography

Conditions
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Acute Respiratory Distress Syndrome, Electrical Impedance Tomography, Prone Position Ventilation, Ventilation Perfusion Mismatch

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: 1. Age ≥18 years. 2. ARDS patients with endotracheal intubation and mechanical ventilation in prone position Exclusion Criteria: 1. Contraindications of EIT such as chest wound dressing, installation of pacemaker, defibrillator, etc. 2. Unstable vertebral fracture 3. Within 15 days after severe facial trauma or facial surgery 4 within 15 days after tracheal surgery or sternotomy 5. Hemodynamic instability or recent cardiac arrest 6. Increased intraocular pressure. 7. Unstable femoral or pelvic fractures and pelvic external fixation. 8 He had severe chest wall disease and unstable rib fractures. 9 Recent cardiothoracic surgery. 10. Pneumothorax 11. Chronic lung disease: severe obstructive pulmonary disease, severe asthma, interstitial lung disease. 12. Maternal 13. Extracorporeal membrane oxygenation(ECMO) had been administered on admission to the ICU. 14. Intracranial hypertension 15. Pulmonary embolism, acute or chronic right heart failure 16. Severe cardiac dysfunction (New York Heart Association class III or IV, acute coronary syndrome, or sustained ventricular tachyarrhythmia), cardiogenic shock; 17. No informed consent was obtained

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Pulmonary ventilation perfusion(V/Q) ratio after 16 hours of PPV monitored by EIT | the V/Q radio were monitored by EIT after patients were implemented prone position ventilation(PPV) for 16h. The images of ventilation distribution were collected by EIT, and the images of perfusion distribution were collected by injected 10ml of 10% hypertonic saline through a central vein catheter during inspiratory hold or expiratory hold. The ventilation and perfusion images were analysed by specialized software to obtain the data of V/Q radio. | 16 hours after prone position ventilation | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Pulmonary ventilation perfusion(V/Q) ratio before PPV monitored by EIT before PPV | The V/Q radio were monitored by EIT before patients were implemented prone position ventilation(PPV). The images of ventilation distribution were collected by EIT, and the data of perfusion distribution were collected by injected 10ml of 10% hypertonic saline through a central vein catheter during inspiratory hold or expiratory hold. The ventilation and perfusion images were analysed by specialized software to obtain the data of V/Q radio. | within 1 hour before preparing PPV | 
| Pulmonary ventilation perfusion(V/Q) ratio after PPV ending 8h monitored by EIT | the V/Q radio were monitored by EIT 8 hours after prone position ventilation ending.The images of ventilation distribution were collected by EIT, and the data of perfusion distribution were collected by injected 10ml of 10% hypertonic saline through a central vein catheter during inspiratory hold or expiratory hold. The ventilation and perfusion images were analysed by specialized software to obtain the data of V/Q radio. | 8 hours hours after prone position ventilation ending | 
| Pulmonary ventilation distribution before PPV, PPV for 16h and 8h after PPV ending | Pulmonary ventilation distribution were monitored by EIT before PPV, PPV for 16h and 8h after PPV ending. The images of ventilation distribution were collected by EIT and analysed by specialized software to obtain the data. | within 1hour before preparing PPV, 16 hours after and 8 hours after PPV ending | 
| Pulmonary perfusion distribution before PPV, PPV for 16h and 8h after PPV ending | The pulmonary perfusion distribution were monitored by EIT before PPV, PPV for 16h and 8h after PPV ending. The images of perfusion distribution were collected by injected 10ml of 10% hypertonic saline through a central vein catheter during inspiratory hold or expiratory hold. The perfusion images were analysed by specialized software to obtain the data of pulmonary perfusion distribution. | within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending | 
| Pulmonary shunt percentage before PPV, PPV for 16h and 8h after PPV ending | The ventilation and perfusion images were analysed by specialized software to obtain the data of pulmonary shunt percentage. | within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending | 
| Pulmonary dead space percentage before PPV, PPV for 16h and 8h after PPV ending | The ventilation and perfusion images were analysed by specialized software to obtain the data of pulmonary dead space percentage. | within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending | 
| Peak pressure before PPV, PPV for 16h and 8h after PPV ending | Peak pressure data were obtained from ventilators | Within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending | 
| Plat pressure before PPV, PPV for 16h and 8h after PPV ending | Plat pressure data were obtained from ventilators | Within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending | 
| Tidal volume before PPV, PPV for 16h and 8h after PPV ending | Tidal volume data were obtained from ventilators | within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending | 
| Driving pressure before PPV, PPV for 16h and 8h after PPV ending | Driving pressure(DP) data were obtained from ventilators | within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending | 
| Static compliance(Cs) before PPV, PPV for 16h and 8h after PPV ending | Cs is equal to tidal volume divided by DP | within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending | 
| P/F ratio before PPV, PPV for 16h and 8h after PPV ending | P/F ratio data were obtain from arterial blood gas analysis | within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending | 
| Carbon dioxide partial pressure(PaCO2) before PPV, PPV for 16h and 8h after PPV ending | PaCO2 data were obtain from arterial blood gas analysis | within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending | 
| Ventilatory ratio(VR) before PPV, PPV for 16h and 8h after PPV ending | VR=[minute ventilation (ml/min)×arterial partial tension of carbon dioxide (mmHg)] / [predicted body weight×100×37.5 | within 1 hour before preparing PPV, 16 hours after and 8 hours after PPV ending | 
| 28 days mortality | Mortality of from the day of enrollment to day 28 | From the day of enrollment to day 28 | 
| Ventilator free days(VFD) within 28 days | The number of ventilator free days for patients from enrollment day to day 28, if patients died within 28 days,VFD was equal to zero. | From the day of enrollment to day 28 | 
| Mortality in the ICU | Mortality in the ICU of all participants | From the day of enrollment to the day of transfer from the ICU or death，up to 90 days | 
| Length of stay(LOS) | LOS(length of stay) of hospital | From the day of to the day of admitting to hospital to depart from the hospital or death，up to 90 days | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Acute Respiratory Distress Syndrome, Electrical impedance tomography, prone position ventilation