Acute Respiratory Distress SyndromeAVALANCHENCT05224323
Avalanche Phenomenon During Airways Opening in Acute Respiratory Distress Syndrome
An observational study of Acute Respiratory Distress Syndrome, run by Poitiers University Hospital at 1 site in France.
Trial summary
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. Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Acute Respiratory Distress Syndrome
- What is being tested?
- Airway pressure, flow, esophageal pressure, ventilation distribution
- How many people
- 50 participants
- Where
- 1 siteFrance
- Study dates
- 1 Mar 2022to Oct 2026
- How long will I take part?
- 28 Days
- Phase
- Observational
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Study population: Patients with moderate-to-severe acute respiratory distress syndrome will be included within the first 72 hours after meeting the Berlin definition criteria. After ruling out exclusion criteria and obtaining informed consent from their relatives, patients will be included in the study.
Who may be able to join
- 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
Who cannot join
- Pneumothorax
- Broncho-pleural fistula
- Tracheostomy
- Hemodynamic instability
- Severe hypoxemia
- Suspected of proven intracranial hypertension
Show all 10Show fewer
- Chronic obstructive lung disease
- Pacemaker or defibrillator
- Decision to withhold of withdraw life-sustaining measures
- Under protection
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
France1 site, 1 recruiting
- Recruiting
CHU Poitiers
Poitiers, 86000
Rémi COUDROY, Pr, remi.coudroy@chu-poitiers.fr
About this study
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.
- Conditions
- Acute Respiratory Distress Syndrome
- Being tested
- Airway pressure, flow, esophageal pressure, ventilation distribution
- Medical subject headings
- Respiratory Distress Syndrome
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Airway pressure, flow, esophageal pressure, ventilation distributionOther
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.
What is being measured
The primary outcome is the main question the study is designed to answer.
To assess the prevalence of "avalanche" phenomenon during low-flow lung inflation.
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.
Measured: At inclusion
Secondary outcomes (3)
To compare characteristics of patients and their outcomes according to the existence of "avalanche" phenomenon during low-flow lung inflation.
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.
Measured: Day 28
To assess the existence of an inflection point on the low-flow deflation pressure-volume curve.
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.
Measured: At inclusion
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
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.
Measured: At inclusion
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted4 Feb 2022
- Study start1 Mar 2022
- Primary completionSep 2026 (estimated)
- Study completionOct 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (2)Papers the sponsor has linked to this study.
- Other trials for Acute Respiratory Distress SyndromeStudies of the same condition, open and under way.
- More trials run by Poitiers University HospitalThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Observational
- Observational model
- Cohort
- Time perspective
- Prospective
- Enrolment
- 50 participants (estimated)
- Target duration
- 28 Days
Sponsor and investigators
- Lead sponsor
- Poitiers University Hospital
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05224323
- Sponsor's protocol ID
- AVALANCHE
- Acronym
- AVALANCHE
- Status last verified
- Dec 2025
- First submitted
- 25 Jan 2022
- Last updated
- 24 Dec 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided
Publications
Suki B, Barabasi AL, Hantos Z, Petak F, Stanley HE. Avalanches and power-law behaviour in lung inflation. Nature. 1994 Apr 14;368(6472):615-8. doi: 10.1038/368615a0.
PubMed 8145846Chen L, Del Sorbo L, Grieco DL, Shklar O, Junhasavasdikul D, Telias I, Fan E, Brochard L. Airway Closure in Acute Respiratory Distress Syndrome: An Underestimated and Misinterpreted Phenomenon. Am J Respir Crit Care Med. 2018 Jan 1;197(1):132-136. doi: 10.1164/rccm.201702-0388LE. No abstract available.
PubMed 28557528
Study at a glance
From the registry record, last updated by the sponsor on 24 Dec 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Avalanche Phenomenon During Airways Opening in Acute Respiratory Distress Syndrome
- ClinicalTrials.gov ID
- NCT05224323
- Acronym / sponsor ID
- AVALANCHE / AVALANCHE
- Conditions
- Acute Respiratory Distress Syndrome
- Study type
- Observational
- Recruitment status
- Recruiting
- Enrolment
- 50 participants (estimated)
- Lead sponsor
- Poitiers University HospitalUniversity, hospital or other
- Study start
- 1 Mar 2022 (actual)
- Primary completion
- Sep 2026 (estimated)
- Study completion
- Oct 2026 (estimated)
- First posted
- 4 Feb 2022 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Study design
- Observational model
- Cohort
- Time perspective
- Prospective
- Target follow-up
- 28 Days
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
- Study population
- Patients with moderate-to-severe acute respiratory distress syndrome will be included within the first 72 hours after meeting the Berlin definition criteria. After ruling out exclusion criteria and obtaining informed consent from their relatives, patients will be included in the study.
Key inclusion criteria (8 listed)
- 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;
Key exclusion criteria (10 listed)
- Pneumothorax
- Broncho-pleural fistula
- Tracheostomy
- Hemodynamic instability
- Severe hypoxemia
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Airway pressure, flow, esophageal pressure, ventilation distributionAfter 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. | Other | – |
Primary outcome
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.
3 secondary outcomes
To compare characteristics of patients and their outcomes according to the existence of "avalanche" phenomenon during low-flow lung inflation.
Time frame: Day 28
To assess the existence of an inflection point on the low-flow deflation pressure-volume curve.
Time frame: At inclusion
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
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 24 Dec 2025.
- Background: PubMed 8145846Suki B, Barabasi AL, Hantos Z, Petak F, Stanley HE. Avalanches and power-law behaviour in lung inflation. Nature. 1994 Apr 14;368(6472):615-8. doi: 10.1038/368615a0.
- Background: PubMed 28557528Chen L, Del Sorbo L, Grieco DL, Shklar O, Junhasavasdikul D, Telias I, Fan E, Brochard L. Airway Closure in Acute Respiratory Distress Syndrome: An Underestimated and Misinterpreted Phenomenon. Am J Respir Crit Care Med. 2018 Jan 1;197(1):132-136. doi: 10.1164/rccm.201702-0388LE. No abstract available.
- Individual participant dataSharing planned: Undecided
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of Acute Respiratory Distress Syndrome, run by Poitiers University Hospital at 1 site in France.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 8 inclusion and 10 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 24 Dec 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in France. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Rémi Coudroy, MD, PhD (+ 33 5 49 44 40 07, remi.coudroy@chu-poitiers.fr), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
To assess the prevalence of "avalanche" phenomenon during low-flow lung inflation. (time frame: At inclusion). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT05224323, which also lists 2 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 24 Dec 2025.