Expiratory Flow Limitation Assessment

Study Overview
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Brief Summary
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This study intended to assess the expiratory flow limitation (EFL) during tidal breath in patients intubated in intensive care unit (ICU) for moderate or severe acute respiratory distress syndrome (ARDS). EFL is defined as the lack of increase in expiratory flow in response to an increase in alveolar-to-atmospheric pressure gradient. It reflects airway closure. Early studies have been done using the Negative expiratory pressure (NEP) technique, which is no longer available. We proposed in present study a new method, which consists of diverting manually the expiratory flow to the atmosphere by-passing the expiratory valve. We aimed at assessing EFL at positive expiratory pressure (PEP) 5 cmH2O in semi-recumbent then in supine position together with measurement of trans-pulmonary pressure and regional lung ventilation. Higher PEP levels will be tested, namely 10, 15 and a trans-pulmonary PEP of 3 cmH2O, in semi-recumbent position.

Official Title
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Expiratory Fow Assessment in ARDS Patients

Conditions
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Acute Respiratory Distress Syndrome

Intervention / Treatment
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* Other: increase in positive end expiratory pressure


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: 18 years or more in age moderate to severe ARDS according to the Berlin definition : Intubated (or tracheotomized) and mechanically ventilated in the ICU no pregnancy informed consent from the next of kin Exclusion Criteria: Contra-indication to PEP > 5 cmH2O extracorporeal membrane oxygenation (ECMO) chest tube mean arterial pressure < 65 mmHg Contra-indication to oesophageal device underlying disease fatal in less than one year active therapy limitation under guardian refusal to participate not affiliated to insurance regimen speaking barrier of the next of kin investigator not available

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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Design Details

Primary Purpose: Diagnostic
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: Patients with EFL at PEP 5<br>Patients with EFL at PEP 5 at the time of inclusion either in supine or semi-recumbent position | Other: increase in positive end expiratory pressure<br>* increase in positive end expiratory pressure from 5 to 10 then 15 cmH2O then at the value for trans pulmonary end expiratory pressure amounting to 3 cmH2O<br>|
| Other: Patients with no EFL at PEP 5<br>Patients with no EFL at PEP 5 at the time of inclusion in both supine and semi-recumbent positions | Other: increase in positive end expiratory pressure<br>* increase in positive end expiratory pressure from 5 to 10 then 15 cmH2O then at the value for trans pulmonary end expiratory pressure amounting to 3 cmH2O<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| EFL at PEP 5 cmH2O | A Fleish 2 pneumotachograph and a port to measure airway pressure are attached at the Y piece of the ventilator circuit and connected to a Biopac 150. At the end of inspiration the air is expelled to the atmosphere upstream the expiratory valve. The flow volume loop at baseline and that during the manoeuver are plotted and patients classified as EFL or not EFL (NFL). Measurements are taken in semi-recumbent then after 5 minutes in supine position. | at inclusion | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Trans-pulmonary pressure at end expiratory at PEP 5 | After insertion of esophageal balloon together with pneumotachograph and port for airway pressure trans-pulmonary pressure (airway-esophageal pressure) is measured after a 3-sec end-expiratory pause in semi-recumbent and then after 5 minutes in supine position | at inclusion | 
| Trans-pulmonary pressure at end expiratory at PEP 10 in EFL and NFL patients | PEP is increased to 10 cmH2O and 15 minutes later trans-pulmonary pressure is measured after a 3-sec end-expiratory pause in semi-recumbent position | 15 minutes after PEP set to 10 cm H2O | 
| Lung compliance at PEP 10 in EFL and NFL patients | PEP is increased to 10 cmH2O and 15 minutes later lung compliance is measured after a 3-sec end-expiratory pause in semi-recumbent position | 15 minutes after PEP set to 10 cm H2O | 
| lung ventilation distribution at PEP 10 in EFL and NFL patients | PEP is increased to 10 cmH2O and 15 minutes later lung ventilation is measured by using electrical impedance tomography (EIT) in semi-recumbent position (an EIT belt having been inserted together with the previous measurement devices). | 15 minutes after PEP set to 10 cm H2O | 
| Transcutaneous oxygen saturation (SpO2) at PEP 10 in EFL and NFL patients | PEP is increased to 15cmH2O and 15 minutes later SpO2 is read from the vital functions monitoring device and SpO2/FIO2 computed | 15 minutes after PEP set to 10 cm H2O | 
| Trans-pulmonary pressure at end expiratory at PEP 15 in EFL and NFL patients | PEP is increased to 15 cmH2O and 15 minutes later trans-pulmonary pressure is measured after a 3-sec end-expiratory pause in semi-recumbent position | 15 minutes after PEP set to 15 cm H2O | 
| Lung compliance at PEP 15 in EFL and NFL patients | PEP is increased to 15 cmH2O and 15 minutes later lung compliance is measured after a 3-sec end-expiratory pause in semi-recumbent position | 15 minutes after PEP set to 15 cm H2O | 
| lung ventilation distribution at PEP 15 in EFL and NFL patients | PEP is increased to 15 cmH2O and 15 minutes later lung ventilation is measured by using electrical impedance tomography (EIT) in semi-recumbent position (an EIT belt having been inserted together with the previous measurement devices). | 15 minutes after PEP set to 15 cm H2O | 
| transcutaneous oxygen saturation (SpO2) at PEP 15 in EFL and NFL patients | PEP is increased to 15 cmH2O and 15 minutes later SpO2 is read from the vital functions monitoring device and SpO2/FIO2 computed. | 15 minutes after PEP set to 15 cm H2O | 
| Trans-pulmonary pressure at end expiratory at PEP to reach Trans-pulmonary pressure at end expiratory =+3 cmH2O in EFL and NFL patients | PEP is set to reach Trans-pulmonary pressure at end expiratory =+3 cmH2O and 15 minutes later trans-pulmonary pressure is measured after a 3-sec end-expiratory pause in semi-recumbent position | 15 minutes after PEP set to reach Trans-pulmonary pressure at end expiratory =+3 cmH2O | 
| Lung compliance at PEP to reach Trans-pulmonary pressure at end expiratory =+3 cmH2O in EFL and NFL patients | PEP is set to reach Trans-pulmonary pressure at end expiratory =+3 cmH2O and 15 minutes later lung compliance is measured after a 3-sec end-expiratory pause in semi-recumbent position | 15 minutes after PEP set to reach Trans-pulmonary pressure at end expiratory =+3 cmH2O | 
| lung ventilation distribution at PEP set to reach Trans-pulmonary pressure at end expiratory =+3 cmH2O in EFL and NFL patients | PEP is set to reach Trans-pulmonary pressure at end expiratory =+3 cmH2O and 15 minutes later lung ventilation is measured by using electrical impedance tomography (EIT) in semi-recumbent position (an EIT belt having been inserted together with the previous measurement devices). | 15 minutes after PEP set to reach Trans-pulmonary pressure at end expiratory =+3 cmH2O | 
| Transcutaneous oxygen saturation (SpO2) at PEEP set to reach Trans-pulmonary pressure at end expiratory =+3 cmH2O in EFL and NFL patients | PEEP is increased to 15 cmH2O and 15 minutes later SpO2 is read from the vital functions monitoring device and SpO2/FIO2 computed. | 15 minutes after PEEP set to reach Trans-pulmonary pressure at end expiratory =+3 cmH2O | 
| lung recruitment at PEEP 10 in EFL and NFL patients | PEEP is increased to 10 cmH2O and 15 minutes later lung recruitment is measured between PEEP 10 and PEEP 5 (in each body position) from volume-pressure curves recorded at PEEP 10 and PEEP 5. The lung recruitment is the change in lung volume for a given pressure (higher PEEP and 20 cmH2O) | 15 minutes after PEEP set to 10 cm H2O | 
| lung recruitment at PEEP 15 in EFL and NFL patients | PEEP is increased to 15 cmH2O and 15 minutes later lung recruitment is measured between PEEP 15 and PEEP 5 (in each body position) from volume-pressure curves recorded at PEEP 15 and PEEP 5. The lung recruitment is the change in lung volume for a given pressure (higher PEEP and 20 cmH2O) | 15 minutes after PEEP set to 15 cm H2O | 
| lung recruitment at PEEP set to reach Trans-pulmonary pressure at end expiratory =+3 cmH2O in EFL and NFL patients in EFL and NFL patients | PEEP is increased to PEEP set to reach Trans-pulmonary pressure at end expiratory =+3 cmH2O and 15 minutes later lung recruitment is measured between PEEP set to reach Trans-pulmonary pressure at end expiratory =+3 cmH2O and PEEP 5 (in each body position) from volume-pressure curves recorded at PEEP set to reach Trans-pulmonary pressure at end expiratory =+3 cmH2O and PEEP 5. The lung recruitment is the change in lung volume for a given pressure (higher PEEP and 20 cmH2O) | 15 minutes after PEEP set to 15 cm H2O | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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trans-pulmonary pressure, airway closure, ARDS, expiratory flow limitation