Acute Respiratory Distress Syndrome
Conditions
Brief 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. 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.
Interventions
OTHERAirway pressure, flow, esophageal pressure, ventilation distribution
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.
Sponsors
Poitiers University Hospital
Study design
Observational model
COHORT
Time perspective
PROSPECTIVE
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| To assess the prevalence of avalanche phenomenon during low-flow lung inflation. | 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
| Measure | Time frame | Description |
|---|---|---|
| To compare characteristics of patients and their outcomes according to the existence of avalanche phenomenon during low-flow lung inflation. | 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. |
| To assess the existence of an inflection point on the low-flow deflation pressure-volume curve. | 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. |
| 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 | 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. |
Countries
France
Contacts
Primary ContactRémi Coudroy, MD, PhD
Backup ContactCéline DELETAGE
Outcome results
None listed