V/Q Matching in Pressure Support Ventilation

Study Overview
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Brief Summary
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The aim of this study is to describe the effects of different levels of pressure support on ventilation-perfusion matching in patients recovering from ARDS, using electrical impedance tomography.

Detailed Description
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Spontaneous breathing during mechanical ventilation has been attributed to both protective and negative effects on patient outcomes, largely varying based on the severity of lung injury. Indeed, in severe ARDS the avoidance of spontaneous efforts has an established protective role. However, spontaneous breathing promotes the distribution of tidal volume towards the dependent lung, and low levels of support pressure determine more homogeneous ventilation in patients recovering from ARDS, compared to higher support levels. Physiology supports the potential of spontaneous breathing to increase lung perfusion, through the decrease of intra-thoracic pressure leading to an increased venous return. This mechanism, in absence of right ventricular dysfunction, may lead to increased global lung perfusion. Furthermore, gas exchange improvements in experimental lung injury models during pressure support vs. controlled ventilation have been explained with redistribution of lung perfusion to nondependent lung areas and improvement of V/Q matching even in absence of significant lung recruitment. Electrical impedance tomography has been clinically used as a non-invasive tool to assess V/Q matching in patients with ARDS and to compare V/Q matching prior to and after a cycle of prone position in spontaneously breathing patients with COVID-19. The aim of this study is to describe the effects of different levels of pressure support on ventilation-perfusion matching in patients recovering from ARDS, using electrical impedance tomography.

Official Title
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Assessment of V/Q Matching During Pressure Support Ventilation With Electrical Impedance Tomography

Conditions
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Acute Respiratory Failure, ARDS, Electrical Impedance Tomography

Intervention / Treatment
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* Other: Level of pressure support


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age ≥ 18 years Need for invasive mechanical ventilation and ICU admission Diagnosis of ARDS at ICU admission or during ICU stay Informed consent Presence of central line in the internal jugular vein Exclusion Criteria: Any contraindication to Electrical impedance tomography monitoring (e. g. severe chest trauma or wounds) Cardiogenic pulmonary edema Pulmonary embolism Chronic obstructive pulmonary disease Pulmonary fibrosis Asthma exacerbation Pneumothorax and/or chest drainages Pre-existing diaphragmatic function impairment Neuro-muscular disease or impairment Moribund patients with limitation of care or expected survival <48h according to the treating physician

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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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Adult mechanically ventilated patients with ARDS<br>Adult mechanically ventilated patients with ARDS (see inclusion/exclusion criteria) | Other: Level of pressure support<br>* Patients will be evaluated in two different conditions sequentially. The first condition will be at a clinically selected level of pressure support under stable clinical conditions. This condition will be labeled according to P0.1: In case of P0.1<2, the clinically selected level of pressure support will be considered High Pressure support. In case of P0.1>2, the clinically selected level of pressure support will be considered Low Pressure support. After data collection at clinically selected level of pressure support, pressure support level will be transiently increased or decreased (i.e. from high to low/ from low to high) to the lowest/highest clinically tolerated level, aiming at the predefined P01 thresholds, and then kept for 20 minutes under stable clinical conditions. Data collection will be repeated and then the clinically selected level of pressure support restored.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Changes in ventilation-perfusion matching | Changes in ventilation-perfusion matching between the two different levels of pressure support (high level of pressure support and low level of pressure support) | Measured after at least 20 minutes from the application of each of the levels of pressure support and at clinical stability | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Changes in gas exchange | Changes in gas exchange measured by blood gas analysis between the two different levels of pressure support (high level of pressure support and low level of pressure support) | Measured after at least 20 minutes from the application of each of the levels of pressure support and at clinical stability | 
| Changes in regional ventilation distribution | Changes in regional ventilation distribution between the two different levels of pressure support (high level of pressure support and low level of pressure support) | Measured after at least 20 minutes from the application of each of the levels of pressure support and at clinical stability | 
| Changes in regional perfusion distribution | Changes in regional perfusion distribution between the two different levels of pressure support (high level of pressure support and low level of pressure support) | Measured after at least 20 minutes from the application of each of the levels of pressure support and at clinical stability | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Electrical impedance tomography, ARDS, V/Q matching