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NCT Number: NCT05224323

Avalanche Phenomenon During Airways Opening in Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome accounts for 23% of mechanically ventilated patients and is associated with high mortality rate. Although life-saving, mechanical ventilation may worsen lung injury through two main mechanisms: lung overdistension and atelectrauma. Indeed, the cyclic opening and closure of airways during tidal ventilation may cause lung and bronchial injuries as suggested by animal models and autopsy findings. Complete airways closure has recently been described in 40% of patients with acute respiratory distress syndrome, and setting positive end-expiratory pressure above the airway opening pressure may limit atelectrauma. However, animal and mathematical models suggest that above the airway opening pressure, more distal airways open unevenly according to their own opening pressure, resulting in an "avalanche"-like phenomenon during lung inflation. This phenomenon has never been described in humans. A better understanding of the opening of airways in acute respiratory distress syndrome may help to limit ventilation-induced lung injury and to improve outcomes.

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Key information

Conditions

Acute Respiratory Distress Syndrome Lung Diseases Respiration Disorders Respiratory Distress Syndrome Respiratory Tract Diseases

Age range

18 year and older

Sex eligibility

All sexes

Study type

Observational

Primary location

CHU Poitiers

Poitiers, 86000, France

Location status: Recruiting

Location contact

Rémi COUDROY, Pr

CONTACT

[email protected]

Who can participate

Healthy volunteers accepted: No

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

Inclusion criteria

  • Age ≥ 18
  • Moderate-to-severe acute respiratory distress syndrome within the first 72 hours after meeting the Berlin definition criteria:
  • Within 1 week of a known clinical insult or new or worsening respiratory symptoms;
  • Bilateral opacities (not fully explained by effusions, lobar/lung collapse, or nodules);
  • Respiratory failure not fully explained by cardiac failure or fluid overload;
  • PaO2/FiO2 ≤ 200 mmHg with positive end-expiratory pressure ≥ 5 cmH2O.
  • Absence of spontaneous breathing efforts
  • Consent to participate to the study from the patient and/or its surrogate

Exclusion criteria

  • Pneumothorax
  • Broncho-pleural fistula
  • Tracheostomy
  • Hemodynamic instability
  • Severe hypoxemia
  • Suspected of proven intracranial hypertension
  • Chronic obstructive lung disease
  • Pacemaker or defibrillator
  • Decision to withhold of withdraw life-sustaining measures
  • Under protection

Treatment and study plan

Airway pressure, flow, esophageal pressure, ventilation distribution

Other

After informed consent, baseline characteristics of patients will be collected. Airway pressure, flow and esophageal pressure will be recorded using high sampling rate and ventilation distribution using electrical impedance tomography will be recorded during the study. The ventilator will be set at a positive end-expiratory pressure of 15 cmH2O during 10 minutes. Then, respiratory rate will be decreased to 8 breaths/min, and positive end-expiratory pressure will be decreased to 5 cmH2O over one breath to measure the recruited volume. Then, three low-flow inflation and deflation pressure-volume curves will be performed before resuming clinical ventilator settings. Patients will be followed until Day 28 after inclusion or ICU discharge. Maneuvers performed are part of the usual care of patients with acute respiratory distress syndrome in our unit.

Primary outcomes

  1. To assess the prevalence of "avalanche" phenomenon during low-flow lung inflation.

    Time frame: At inclusion

    The distribution of pressure drops on low-flow inflation pressure-volume curves will be described and plotted on a log-log scale graph. "Avalanche" phenomenon will be defined if this distribution follows power law (i.e. is linear on a log-log scale) with a R2 ≥ 0.80. The prevalence of "avalanche" phenomenon will be described as frequency and 95% confidence interval.

Secondary outcomes

  1. To compare characteristics of patients and their outcomes according to the existence of "avalanche" phenomenon during low-flow lung inflation.

    Time frame: Day 28

    Continuous variables will be summarized as mean ± standard deviation or median [25th-75th percentile] according to their distribution and compared by means of the Mann-Whitney or the Student's t test. Categorical variables will be summarized as frequency (percentage) and 95% confidence interval, and compared by means of Fisher or Chi2 test.

  2. To assess the existence of an inflection point on the low-flow deflation pressure-volume curve.

    Time frame: At inclusion

    The slope of the low-flow deflation pressure-volume curve will be computed by means of linear regression and summarized as mean ± standard deviation or median [25th-75th percentile] according to its distribution. The existence of an inflexion point will be summarized as number (percentage) and 95% confidence interval. The airway pressure corresponding to this inflexion point will be summarized as mean ± standard deviation or median [25th-75th percentile] according to its distribution.

  3. To assess the airway pressure value of the inflection point on the low-flow deflation pressure-volume curve in patients with an inflexion point on the low-flow deflation pressure-volume curve

    Time frame: At inclusion

    The airway pressure corresponding to the inflexion point on the low-flow deflation pressure-volume curve will be summarized as mean ± standard deviation or median [25th-75th percentile] according to its distribution.

Study contacts

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

Céline DELETAGE

CONTACT

[email protected]

+33 5 49 44 38 54

Rémi Coudroy, MD, PhD

CONTACT

[email protected]

+ 33 5 49 44 40 07

Sponsors and collaborators

Lead sponsor

Poitiers University Hospital

Other

Registry information

Acronym: AVALANCHE

Important dates

Study start
2022
Primary completion
2026
Study completion
2026
First posted
Feb 4, 2022
Registry last updated
Dec 24, 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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