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

Not Applicable

Not yet recruiting

• Conditions: ARDS

• Registration Number: NCT05578742
• Lead Sponsor: University Hospital, Angers

Brief Summary

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).

Detailed Description

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.

Study Timeline

• Study First Submitted: 2022-09-27
• Status Verified: 2022-10
• Study First Submitted QC: 2022-10-10
• Study First Posted: 2022-10-13
• Last Update Submitted: 2023-09-21
• Last Update Posted: 2023-09-22
• Study Start: 2023-10
• Primary Completion: 2025-10
• Study Completion: 2026-04

Recruitment & Eligibility

• Status: NOT_YET_RECRUITING
• Sex: All
• Target Recruitment: 50

Inclusion Criteria

Not provided

Exclusion Criteria

Not provided

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Primary Outcome Measures

Name	Time	Method
Difference in ventilation/perfusion mismatch between PEEP 5 and 15 cmH2O according to the two studied phenotypes	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 Outcome Measures

Name	Time	Method
Difference in respiratory mechanics between PEEP 5 and 15 cmH2O according to the two studied phenotypes	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.
Difference in oxygenation between PEEP 5 and 15 cmH2O according to the two studied phenotypes	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.
Difference in carbon clearance between PEEP 5 and 15 cmH2O according to the two studied phenotypes	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.
Difference in dead space measured by capnometric volumetry between PEEP 5 and 15 cmH2O according to the two studied phenotypes	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.
Difference in dead space measured by calorimetry between PEEP 5 and 15 cmH2O according to the two studied phenotypes	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.
Correlations between V.Q mismacth and overdisension and lung collapsus	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.
Difference in venous oxygen saturation between PEEP 5 and 15 cmH2O according to the two studied phenotypes	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.
Correlation between V/Q mismatch markers and recruitability	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.
Correlations between V/Q mismatch assessed by EIT and dead space markers	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.
Difference in stress index between PEEP 5 and 15 cmH2O according to the two studied phenotypes	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.