Post- End- Expiratory Pressure Affect the Alveolar Heterogeneity in Moderate and Sever ARDS Patients

Study Overview
=================
Brief Summary
-----------------
This study try to use EIT ( Electronic impedance tomography ) to evaluate the alveolar heterogeneity and use trans-pulmonary pressure and stain to evaluate the lung injury . The study use these methods to figure out how PEEP impact the alveolar heterogeneity and VILI.

Detailed Description
-----------------
ARDS(Acute respiratory distress syndrome )is common in patients suffering Sepsis, trauma, burning and other sever condition and characterized by diffuse alveolar damage and alveolar heterogeneity.ARDS patient need MV(mechanical ventilation )to maintain oxygenation and need unique MV tragedy to avoid VILI(Ventilator induced Lung injury ).PEEP(post-end-expiratory pressure) is crucial to maintain oxygenation and avoid VILI according to researches. But there are also some other research different voice. This study try to use EIT ( Electronic impedance tomography ) to evaluate the alveolar heterogeneity and use trans-pulmonary pressure and stain to evaluate the lung injury . The study use these methods to figure out how PEEP impact the alveolar heterogeneity and VILI.

Official Title
-----------------
Post- End- Expiratory Pressure Affect the Alveolar Heterogeneity in Moderate and Sever ARDS Patients

Conditions
-----------------
Ards

Intervention / Treatment
-----------------
* Device: Post-end-Expiratory pressure


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Age≥18 or<80； Moderate or sever ARDS in 2012 <Berlin definition>; Applied mechanical ventilation; Consent signed. Exclusion Criteria: Asthma or COPD； Cardiogenic edema； Sever neutropenia(<500/mm3)； Hemodynamic astatic: DOPA or Dobutamine >15 µg/kg/ min; NE > 15ug /min； GCS coma score ≤12； Thoracic injury or surgery patients contradict EIT ； Refuse to join in trail； Included in other clinical trail。

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

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
No

Study Plan
=================
How is the study designed?
-----------------

Arms and Interventions

| Intervention/Treatment |
| --- |
|Device: Post-end-Expiratory pressure|Titrate the PEEP from 24 cmH2O to 6 cmH2O, 2 cmH2O/step and record EIT, trans-pulmonary pressure, hemodynamic parameter and Blood-gas analysis.|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| alveolar hyper-distention; alveolar collapse；alveolar opening and closing； | The study use Pulmo Vista 500 device (Drager co.),is intended to perform thoracic bioimpedance measurements by applying the technique of electrical impedance tomography (EIT)to evaluate alveolar hyper-distention(%of the lung volume); alveolar collapse(% of the lung volume)；alveolar opening and closing(% of the lung volume). | September,1,2018-December 30, 2020 | 
| Trans-pulmonary pressure | The researchers place tube in the esophagus and connect it to transmitter to measure esophageal pressure (mmHg)and calculate trans-pulmonary pressure(mmHg) to evaluate stress | September,1,2018-December 30, 2020 | 
| EELV | The research use nitrogen wash out to measure EELV（end-expiratory lung volume, ml） to calculate dynamic strain and evaluate the strain | September,1,2018-December 30, 2020 | 
| peak pressure | The researchers use ventilator to measure peak pressure(cmH2O) in patients with mechanical ventilation and without spontaneous breathing.. | September,1,2018-December 30, 2020 | 
| plateau pressure | The researchers use ventilator to do inspiration pause to measure plateau pressure(cmH2O) in patients with mechanical ventilation and without spontaneous breathing. | September,1,2018-December 30, 2020 | 
| tidal volume | The researchers use ventilator to measure tidal volume(ml) in patients with mechanical ventilation and without spontaneous breathing.. | September,1,2018-December 30, 2020 | 
| respiratory rate | The researchers record the set respiratory rate(bpm) in patients with mechanical ventilation. | September,1,2018-December 30, 2020 | 
| flow | The researchers record the set Flow (L/min) in patients with mechanical ventilation. | September,1,2018-December 30, 2020 | 
| FiO2 | The researchers record the set FiO2 ( fraction of inspiratory oxygen, %) in patients with mechanical ventilation. | September,1,2018-December 30, 2020 | 
| PaO2 | The researchers use blood gas analysis to measure PaO2( arterial oxygen pressure,mmHg) | September,1,2018-December 30, 2020 | 
| PaCO2 | The researchers use blood gas analysis to measure PaCO2( arterial carbon dioxide pressure,mmHg) . | September,1,2018-December 30, 2020 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| SBP | Recording SBP(systolic pressure, mmHg),which is always continuously monitored with invasive pressure monitor. | September,1,2018-December 30, 2020 | 
| DBP | Recording DBP(Diastolic pressure, mmHg),which is always continuously monitored with invasive pressure monitor. | September,1,2018-December 30, 2020 | 
| CVP | Recording CVP(central venous Pressure）,which is always discontinuously monitored with jugular pressure monitor mmHg). | September,1,2018-December 30, 2020 | 
| vasopressor | Recording clinical vasopressor usage including Norepinephrine（ μg/Kg/min;）Epinephrine（μg/Kg/min） Dobutamine （ μg/Kg/min) | September,1,2018-December 30, 2020 | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
ARDS（Acute respiratory syndrome）;, stress;, strain;, Trans-pulmonary pressure;, FRC(functional residual capacity ), PEEP（post end-expiratory pressure）;, EIT（Electronic impedance tomography）;, RVD(region ventilation delay)