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NCT Number: NCT05578742

V/Q Matching Variations With PEEP in ARDS According to Compliance-based Phenotypes (France)

This study aim to compare the effect of Positive End Expiratory Pressure (PEEP) on ventilation/perfusion mismatch in two phenotypes of patients with moderate-to-severe Acute Respiratory Distress Syndrome (ARDS), characterized by their respiratory system elastance (Ers). Ventilation/perfusion mismatch will be assessed by Electrical Impedance Tomography (EIT).

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Key information

Conditions

ARDS Behavior Health Behavior Patient Acceptance of Health Care Patient Compliance Treatment Adherence and Compliance

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

About this study

Acute Respiratory Distress Syndrome (ARDS) is characterized by hypoxemia caused by inflammatory lung injury. Recent studies showed an important variability in ARDS phenotypes . The recent COVID-19 crisis highlighted the presence of ARDS patients with severe hypoxemia and normal respiratory system compliance, and retrospective series confirmed the existence of this atypical ARDS pattern also in non-COVID etiologies.

The dissociation between mechanics and hypoxemia may be related to a specific diversity in the pattern of ventilation-perfusion matching (V/Q matching) among patients with normal compliance and ARDS. In patients with low compliance, V/Q mismatch may be characterized by right-to-left shunt, secondary to collapse of the gravity-dependent regions; while, in patients with normal compliance, V/Q mismatch may show a redistribution of blood flow to hypo-ventilated lung areas by larger dead space and impaired hypoxic vasoconstriction.

These differences may also influence the response to PEEP in terms of gas exchange and lung protection . It may also explain the failure for high PEEP levels to improve significantly mortality in the global ARDS population (i.e., with patients' selection only based on hypoxemia).

Electrical Impedance Tomography (EIT) is a device allowing to assess ventilation and perfusion distribution. Thus, EIT can be used to evaluate global and regional V/Q matching, and could be used to understand mechanisms of hypoxemia, especially in patients with normal mechanics and ARDS.

The aim of this study is to assess V/Q matching according to these different ARDS phenotypes, and to evaluate the effects of PEEP in each one.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • intubated patients with moderate and severe ARDS (Berlin definition, PaO2/FiO2 ≤200 mmHg at PEEP 5 cmH2O)
  • undergoing deep sedation
  • on controlled mechanical ventilation
  • between 24 hours and 5 days after intubation.

Exclusion criteria

  • age <18 years old; pregnancy
  • patient undergoing legal protection
  • contra-indications to EIT (e. g. severe chest trauma or wounds)
  • pneumothorax; patient undergoing ECMO
  • patient with BMI ≥35 kg/m2
  • hemodynamic instability with MAP <60 mmHg despite vasopressors.

Treatment and study plan

PEEP increase

Procedure

Positive End Expiratory Pressure (PEEP) will be increased from 5 to 15 cmH2O.

PEEP decrease

Procedure

Positive End Expiratory Pressure (PEEP) will be decreased from 15 to 5 cmH2O.

Primary outcomes

  1. Difference in ventilation/perfusion mismatch between PEEP 5 and 15 cmH2O according to the two studied phenotypes

    Time frame: immediately after each intervention

    Ventilation/perfusion (V/Q) mismatch will be assessed by Electrical Impedance Tomography (EIT). Mismatch is expressed in %. Comparison between phenotype with higher and lower elastance will be performed.

Secondary outcomes

  1. Difference in respiratory mechanics between PEEP 5 and 15 cmH2O according to the two studied phenotypes

    Time frame: immediately after each intervention

    Plateau pressure and total PEEP will be aggregated to compute driving pressure (Plateau pressure minus total PEEP, all in cmH2O). Respiratory system compliance will be computed by dividing tidal volume by driving pressure (in mL.cmH2O-1; respiratory system resistance will be computed as the inverse of compliance; all these values will be assessed and compared between the two PEEP levels. Comparison between phenotype with higher and lower elastance will be performed.

  2. Difference in oxygenation between PEEP 5 and 15 cmH2O according to the two studied phenotypes

    Time frame: immediately after each intervention

    PaO2 (in mmHg) will be assessed and compared between the two PEEP levels. Comparison between phenotype with higher and lower elastance will be performed.

  3. Difference in carbon clearance between PEEP 5 and 15 cmH2O according to the two studied phenotypes

    Time frame: immediately after each intervention

    PaCO2 (in mmHg) will be assessed and compared between the two PEEP levels. Ventilatory ratio (no unit) will be derived from the PaCO2 values. Comparison between phenotype with higher and lower elastance will be performed.

  4. Difference in dead space measured by capnometric volumetry between PEEP 5 and 15 cmH2O according to the two studied phenotypes

    Time frame: immediately after each intervention

    VCO2 (measured by Vcap, in mmHg) will be assessed and compared between the two PEEP levels. Comparison between phenotype with higher and lower elastance will be performed.

  5. Difference in dead space measured by calorimetry between PEEP 5 and 15 cmH2O according to the two studied phenotypes

    Time frame: immediately after each intervention

    VCO2 (measured by calorimetry, in mmHg) will be assessed and compared between the two PEEP levels. Comparison between phenotype with higher and lower elastance will be performed.

  6. Difference in venous oxygen saturation between PEEP 5 and 15 cmH2O according to the two studied phenotypes

    Time frame: immediately after each intervention

    SvO2 (in %) will be assessed and compared between the two PEEP levels. Comparison between phenotype with higher and lower elastance will be performed.

  7. Correlation between V/Q mismatch markers and recruitability

    Time frame: immediately after each intervention

    Recruitability will be assessed between 15 and 5 cmH2O by respiratory mechanics and EIT, as the recruited volumes value (in mL). R/I ratio will be derived from these data (no unit). V/Q mismatch will be computed by EIT, and expressed in %. Correlation will be performed by linear regression.

  8. Correlations between V/Q mismatch assessed by EIT and dead space markers

    Time frame: immediately after each intervention

    Dead space will be assessed by volumetric capnography (if available), venrtilatory ratio, and calorimetriy (if available). V/Q mismatch will be computed by EIT, and expressed in %. Correlation will be performed by linear regression.

  9. Correlations between V.Q mismacth and overdisension and lung collapsus

    Time frame: immediately after each intervention

    Overdistension (%) and lung collapsus (%) will be assessed during the Step 3, by EIT. These two values cannot be measured separately. V/Q mismatch will be computed by EIT, and expressed in %. Correlation will be performed by linear regression.

  10. Difference in stress index between PEEP 5 and 15 cmH2O according to the two studied phenotypes

    Time frame: immediately after each intervention

    stress index (no unit) will be assessed and compared between the two PEEP levels. Comparison between phenotype with higher and lower elastance will be performed.

Study contacts

Contact information is provided by the study sponsor or research team.

François Beloncle, MD

CONTACT

[email protected]

+33 241 35 58 65

UH Angers DRCI

CONTACT

[email protected]

+33 2 41 35 54 96

Sponsors and collaborators

Lead sponsor

University Hospital, Angers

Other Gov

Registry information

Official study title

Effect of PEEP on Ventilartion/Perfusion Ratios According to Different Phenotypes in Patients With ARDS (France)

Acronym: MISMATCHED FR

Important dates

Study start
2024
Primary completion
2026
Study completion
2026
First posted
Oct 13, 2022
Registry last updated
Dec 8, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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