Assessment of the Hemodynamic Effects of PEEP According to Alveolar Recruitment During the ARDS

Study Overview
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Brief Summary
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The corner stone of the treatment of ARDS is mechanical ventilation with high levels of positive end-expiratory pressure, also called PEEP. A high level of PEEP is recommended and frequently used. But PEEP can lower cardiac output and contribute to circulatory failure during mechanical ventilation. Nevertheless, in theory, the PEEP-induced pulmonary vascular resistance (PVR) increase could depend on the level of alveolar recruitment, but it has never been proven. Thus, the aim of this study is to determine the relation between the high-PEEP induced PVR and the alveolar recruitment or overdistension.

Detailed Description
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During acute respiratory distress syndrome (ARDS) the application of positive end-expiratory pressure (PEEP) prevents expiratory alveolar collapse. However, it can induce a predominant recruitment effect or, on the contrary, alveolar overdistension. The recruitment/overdistension ratio can be easily assessed using R/I ratio (or recruitment-to-inflation ratio). However, PEEP is likely to lower cardiac output and contribute to the cardiovascular failure that often occurs in patients with ARDS. Among its hemodynamic effects, PEEP is likely to increase pulmonary vascular resistance and, thus, right ventricular afterload. In theory, this effect should only occur if PEEP over-distends the lung volume, compressing the extra-alveolar vessels and increasing their resistance. However, this different effect of PEEP on pulmonary vascular resistance depending on the degree of recruitment or overdistension has never been demonstrated during ARDS in humans. We retrospectively studied data collected from patients with ARDS, monitored by pulmonary artery catheter (PAC), to eventually find a correlation between the high PEEP-induced PVR increase and recruitement/overdistension profile.

Official Title
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Assessment of the Hemodynamic Effects of PEEP According to Alveolar Recruitment During the ARDS

Conditions
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ARDS, Human, Ventilation Therapy; Complications, Alveolar; Disorder

Intervention / Treatment
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* Device: Pulmonary artery catheter
* Device: Esophagal pressure


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: ARDS diagnosed Invasive mechanical ventilation Pulmonary artery catheter already in place Esophagal pressure measure Exclusion Criteria: Pregnancy Prone position at inclusion Legal protection measures

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Study Plan
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How is the study designed?
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Arms and Interventions

| Intervention/Treatment |
| --- |
|Device: Pulmonary artery catheter|PAC already in place|
|Device: Esophagal pressure|Esophagal pressure already in place|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Correlation between PVR and recruitment-to-inflation ratio | PVR collected at two levels of PEEP and the R/I ratio to assess a relationship between the two variables | Up to hospital discharge (maximum : day 60) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Relationship between the R/I ratio and blood gas analysis | Data collected from the daily blood samples, to assess a relationship between R/I and arterial oxygen pressure | Up to hospital discharge (maximum : day 60) | 
| Relationship between the R/I ratio and respiratory system compliance | Ventilatory parameters collected at two levels of PEEP and R/I collected every day to assess a correlation between R/I and lung compliance | Up to hospital discharge (maximum : day 60) | 
| Relationship between right ventricle size and R/I ratio | Echocardiographic data collected at two levels of PEEP and R/I collected every day to assess a relationship between R/I and changes in RV surface. | Up to hospital discharge (maximum : day 60) | 
| Relationship between PVR change and Transpulmonary gradient (TPG) according to R/I | Data collected from PAC and R/I measure every day to assess the relationship between R/I and TPG at two levels of PEEP. | Up to hospital discharge (maximum : day 60) |