Airway Pressure Release Ventilation for Moderate-to-severe Acute Respiratory Distress Syndrome


This study will examine the feasibility of a large clinical trial investigating the effectiveness of airway pressure release ventilation and low tidal volume ventilation for patients with moderate-to-severe acute respiratory distress syndrome.

Full Title of Study: “Early Use of Airway Pressure ReLease Ventilation in Critically Ill Adults With Moderate-to-severe Acute Respiratory Distress Syndrome”

Study Type

  • Study Type: Interventional
  • Study Design
    • Allocation: Randomized
    • Intervention Model: Parallel Assignment
    • Primary Purpose: Treatment
    • Masking: None (Open Label)
  • Study Primary Completion Date: June 2021

Detailed Description

Acute respiratory distress syndrome (ARDS) is a disease that has an incidence of 5% of hospitalized mechanically ventilated patients. ARDS is associated with high morbidity and mortality in critically ill patients, with mortality reported as high as 45% in severe ARDS. Patients who develop ARDS will require mechanical ventilation. Patients with ARDS are graded by the partial pressure of oxygen to fraction of inspired oxygen ratio (PaO2/FiO2) into three categories of severity: mild (PaO2/FiO2 201-300 mm Hg), moderate (PaO2/FiO2 101-200 mmHg), and severe (PaO2/FiO2 ≤ 100).

Volutrauma and barotrauma are thought to contribute to the development of ARDS and alter mortality. The damage that occurs to the lungs manifests itself as inflammation, which leads to poor gas exchange of oxygen and carbon dioxide. Several strategies of lung-protective mechanical ventilation have been investigated in ARDS, including the use of low tidal volume ventilation (LTVV) or ARDSNet strategy, high frequency oscillation ventilation (HFOV), and airway pressure release ventilation (APRV). Lung protective strategies may be best beneficial prior to the onset of the development of ARDS or early in the course of the disease. As a result of the ARDSNet trial, LTVV has been adopted as the usual standard of care of ventilation and safest mode of ventilation for patients with ARDS.

Recently, APRV has been proposed as a potential alternative to LTVV. APRV is a form of ventilation that keeps the lungs inflated through the majority of the breath cycle and allows patients to breathe spontaneously above this level of inflation. APRV allows for spontaneous respiration with increased airway pressure, potentially allowing for decreased sedation, shorter duration of mechanical ventilation, and decreased need for vasopressors. APRV has been associated with possible reduction in incidence of ARDS and in-hospital mortality in non-randomized observational studies. In patients with established ARDS, the use of APRV has also not been well studied, with most studies limited to small observational studies often with no comparison group. One randomized trial using APRV alone had less than 30% of patients having a diagnosis of ARDS and did not show any difference in any outcomes. Recently, Zhou and colleagues conducted a randomized trial comparing APRV to conventional ventilation in 138 mechanically ventilated patients with mild to severe ARDS and found that APRV may shorten the duration of mechanical ventilation and reduce intensive care unit (ICU) length of stay.

While some of these studies had shown promise of APRV compared to LTVV, there has not been acceptance of APRV into guidelines as first line ventilation, and recommendations of institutions such as the Canadian Agency for Drugs and Technology in Health (CADTH) recommends interpreting these results with caution. Consequently, there remains clinical equipoise on this issue. Some ICU clinicians will currently use APRV as a rescue mode of ventilation in ARDS in their clinical practice while others will continue with the use of LTVV. We would like to randomize patients to LTVV or APRV and examine the feasibility of conducting a large multicentre randomized controlled trial in Canada.


  • Device: Low tidal volume ventilation
    • Conventional ventilation strategy for patient with ARDS
  • Device: Airway pressure release ventilation
    • Experimental ventilation protocol for patients with ARDS

Arms, Groups and Cohorts

  • Active Comparator: Low tidal volume ventilation
    • Conventional low tidal volume ventilation
  • Experimental: Airway pressure release ventilation
    • Early use of airway pressure release ventilation

Clinical Trial Outcome Measures

Primary Measures

  • Informed consent rate
    • Time Frame: Informed consent rate will be measured over a 1 year period of the pilot study
    • A successful informed consent rate will be defined as ≥70% of substitute decision makers or patients approached choosing to participate in this trial
  • Recruitment rate
    • Time Frame: Recruitment rate will be measured over the one year of the pilot study.
    • A successful recruitment rate will be achieving at least 15 patients over the 1 year period.
  • Protocol adherence rate
    • Time Frame: Protocol adherence will be measured for each study patient, and compiled over the duration of the pilot study (i.e. 1 year).
    • An adherence rate of at least 80% will be considered successful.

Secondary Measures

  • 28-day mortality
    • Time Frame: Up to Day 28
    • Death, measured from time of enrollment until 28 days.
  • In-hospital mortality
    • Time Frame: Up to 365 days
    • Death, at hospital discharge
  • ICU length of stay
    • Time Frame: Up to 365 days
    • Length of stay in the intensive care unit
  • Hospital length of stay
    • Time Frame: Up to 365 days
    • Length of stay in the hospital in days
  • Length/duration of mechanical ventilation
    • Time Frame: Up to 365 days
    • Length of time patient was on mechanical ventilation
  • Incidence of tracheostomy
    • Time Frame: Up to 365 days
    • Incidence of tracheostomy during their ICU stay

Participating in This Clinical Trial

Inclusion Criteria

  • Fulfilling the diagnostic criteria of ARDS, according to the Berlin definition
  • Moderate to severe ARDS as defined as a PaO2: FiO2 ratio of ≤150 during invasive mechanical ventilation
  • Endotracheal intubation and mechanical ventilation for ARDS less than 48 hours

Exclusion Criteria

  • Age less than 18 years
  • Pregnancy
  • Intracranial hypertension (suspected or confirmed)
  • Severe chronic obstructive pulmonary disease as defined by either:

1. FEV1/FVC less than 50% predicted, or

2. Chronic hypercarbia (PaCO2>45 mmHg), chronic hypoxemia (PaO2 < 55 mmHg) on room air, and/or elevated admission serum HCO3 >30 mmol/L

  • Presence of documented barotrauma, i.e. pneumothorax
  • Treatment with extracorporeal support (ECMO) at enrollment
  • Refractory shock
  • Advanced directives indicating preferences to not have advanced life support
  • Moribund patient, i.e. not expected to survive longer than 24 hours

Gender Eligibility: All

Minimum Age: 18 Years

Maximum Age: N/A

Are Healthy Volunteers Accepted: No

Investigator Details

  • Lead Sponsor
    • Saskatchewan Health Authority – Regina Area
  • Provider of Information About this Clinical Study
    • Principal Investigator: Eric Sy, Critical Care Physician – Saskatchewan Health Authority – Regina Area
  • Overall Official(s)
    • Eric J Sy, MD MPH FRCPC, Principal Investigator, Saskatchewan Health Authority – Regina Area
  • Overall Contact(s)
    • Eric Sy, MD MPH FRCPC, 306-766-4444,


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