Diaphragm Ultrasound Vs Transpulmonary Pressure To Set PEEP in ARDS

Study Overview
=================
Brief Summary
-----------------
This is a proof of concept study where the investigators aim to study the correlation between the use of a simple bedside ultrasound measurement of diaphragmatic muscle excursion with established (but time consuming) measurements made to optimize an important setting on the mechanical ventilator (positive end expiratory pressure or PEEP) in intubated adults with acute respiratory distress syndrome (ARDS) in the medical ICU.

Detailed Description
-----------------
Ventilator induced lung injury (VILI) generates morbidity and mortality in mechanically ventilated patients. The awareness of respiratory mechanics is essential in the prevention of VILI. Currently, plateau pressures are widely used as a guide to assess alveolar pressure and minimize alveolar injury. However, patients with reduced chest wall compliance can have higher plateau pressures that may not reflect true alveolar pressure. The transpulmonary pressure has been cited as the true alveolar driving pressure because it takes into account pleural pressure that reflect chest wall mechanics; however, this requires measurement of esophageal pressure. The investigators have experienced a disproportionate degree of excursion between the posterior and anterior right hemidiaphragm on bedside ultrasound imaging in patients with ARDS, which may reflect the dependent atelectasis that occurs during low tidal volume ventilation, cardiac weight, weight of injured lung and accumulation of extravascular lung water in critically ill patients. The optimal PEEP can be guided by measurement of esophageal pressure (and subsequent calculation of transpulmonary distending pressure) with a balloon catheter placed into the esophagus much like a nasogastric tube for enteral access. The investigators believe that the normalization of the disproportionate degree of excursion between the anterior and posterior diaphragm can also be used to identify optimal PEEP, and may be correlated with changes in transpulmonary pressure (the current gold standard).

Official Title
-----------------
Diaphragm Excursion By Ultrasound As Compared To Transpulmonary Pressure To Optimize PEEP In ARDS: A Pilot Study

Conditions
-----------------
Acute Respiratory Distress Syndrome, Acute Respiratory Failure

Intervention / Treatment
-----------------
* Device: Ultrasound


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Adults older than 18 years old who develop ARDS, as defined by the Berlin criteria, within 72 hours of ICU admission. Exclusion Criteria: Any contraindication for nasogastric tube placement including recent injury or pathologic condition of the esophagus. Major bronchopleural fistula. Solid organ transplant recipient. History or current diagnosis of diaphragmatic paralysis. Non-conventional mechanical ventilation strategy including high frequency oscillation, airway pressure release ventilation, prone ventilation and extra- corporeal membrane oxygenation. Hemodynamic instability defined as MAP<65 with multiple vasopressors. Declining to sign consent form.

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

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

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

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

Design Details

Primary Purpose: Diagnostic
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Ultrasound<br>Adults older than 18 years old who develop ARDS, as defined by the Berlin criteria, within 72 hours of ICU admission. | Device: Ultrasound<br>* Diaphragmatic excursion ultrasound assessment<br>|

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

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Feasibility | This is a proof of concept study that investigates the degree of dorsal and ventral diaphragmatic excursion with bedside ultrasound during PEEP titration. Optimal PEEP management was guided by an esophageal probe calculating transthoracic pulmonary pressure. Each patient underwent a series of PEEP titrations for which data was recorded on diaphragm excursion (mm) and esophageal pressure (cmH2O). Diaphragm excursion (mm) was measured at the ventral and dorsal side using anatomic m-mode with bedside ultrasound. Esophageal pressure was measured using an esophageal probe which was placed at the bedside. | one year | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
ARDS, PEEP, Critical Care Ultrasound