Expiratory Flow Limitation Assessment

Expiratory Fow Assessment in ARDS Patients

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.

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