Acute Respiratory Distress Syndrome, Hypoxemic Respiratory Failure, Mechanical Ventilation Pressure High
Conditions
Brief summary
Mechanical ventilation can cause damage by overstretching the lungs, especially when the lungs are collapsed or edematous. Raising ventilator pressures can reduce lung collapse and this can prevent overstretching from mechanical ventilation. It remains uncertain how much pressure (PEEP - positive end-expiratory pressure) should be used on the ventilator and how to identify patients who will benefit from higher ventilator pressures vs. lower ventilator pressures. The investigators are using a unique new imaging technology, electrical impedance tomography (EIT), to study this problem and to determine the safest and most effective ventilator pressure level. The results of this study will inform future trials of higher vs. lower PEEP strategies in mechanically ventilated patients.
Detailed description
Patients participating in this physiological cross-over randomized trial will undergo a series of PEEP maneuvers designed to assess lung recruitability, PEEP responsiveness, and optimal PEEP. EIT imaging and esophageal manometry will be employed throughout the protocol to quantify the effect of PEEP on lung function. Patients will be randomized to be ventilated at PEEP levels supplied by the ExPRESS strategy or by the EIT hyperdistention/collapse algorithm. The biological response will be assessed by measuring serum cytokines.
Interventions
DEVICEElectrical Impedance Tomography
Electrical impedance tomography (EIT) is a new technique that enables real-time visualization of the distribution of ventilation at the bedside. This technique allows clinicians and investigators to immediately determine how applying higher or lower PEEP levels affect stress and strain in the lung. The investigators propose to apply this new technique to test a strategy for finding the optimal level of PEEP that prevents lung injury and improves outcomes in critically ill patients.
OTHERExPRESS-derived PEEP level
The ExPRESS algorithm is a traditional approach to selecting PEEP based on respiratory mechanics.
Sponsors
University Health Network, Toronto
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No
Inclusion criteria
* Acute (≤7 days) hypoxemia with PaO2:FiO2 ratio less than or equal to 200 mm Hg * Oral endotracheal intubation and mechanical ventilation * Bilateral airspace opacities on chest radiograph or CT
Exclusion criteria
* Contraindication to EIT electrode placement (burns, chest wall bandaging limiting electrode placement) * Contraindication to esophageal catheter placement (recent upper GI surgery, actively bleeding esophageal varices) * Respiratory failure predominantly due to cardiogenic cause or fluid overload * Ongoing hemodynamic instability (requiring 2 vasopressor agents by continuous infusion AND rising vasopressor infusion rate requirements in the previous 8 hours) * Ongoing ventilatory instability (P/F \< 70 mm Hg, pH \< 7.2; ventilator driving pressures, PEEP, or FiO2 increasing by more than 25% in previous 30 minutes) * Intracranial hypertension (suspected or diagnosed by medical team) * Known or suspected pneumothorax recognized within previous 72 hours * Bronchopleural fistula * Bridge to lung transplant * Recent lung transplantation (within previous 6 weeks) * Attending physician deems the transient application of high airway pressures (\>40 cm H2O) to be unsafe
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Intratidal ventilation heterogeneity | Assessed after completion of 3 hours on randomized strategy (EIT vs ExPRESS) | A measure of variation in the distribution of ventilation throughout the lung as detected by electrical impedance tomography |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Difference in the optimal PEEP levels identified by several different PEEP titration strategies | Assessed immediately after completion of decremental PEEP titration procedure | Compare the relative degree of agreement or disparity between PEEP levels recommended by different PEEP titration strategies |
| Change in ratio of partial pressure of oxygen (PaO2) to inspired fraction of oxygen (FiO2) ratio following a standardized increased in PEEP | Assessed 10 minutes after step PEEP increase from 6-8 to 16-18 cm H2O | Measurement of changes in oxygenation by PaO2/FiO2 ratio due to PEEP |
| Respiratory mechanics (transpulmonary driving pressure) | Assessed after completing 3 hours on the randomized PEEP strategy (EIT vs ExPRESS) | The swing in transpulmonary pressure during inspiration, a measure of dynamic lung stress |
Countries
Canada
Outcome results
None listed