Assessing Lung Inhomogeneity During Ventilation for Acute Hypoxemic Respiratory Failure (ALIVE)

University Health Network, Toronto

Status: Completed

Conditions: Mechanical Ventilation Pressure High; Hypoxemic Respiratory Failure; Acute Respiratory Distress Syndrome

Treatments: Other: ExPRESS-derived PEEP level; Device: Electrical Impedance Tomography

Study type: Interventional

Funder types: Other

Identifiers

NCT03589482

18-6091

17-6226

Details and patient eligibility

About

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.

Full 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.

Enrollment: 20 patients

Sex: All

Ages: 18+ years old

Volunteers: No Healthy Volunteers

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

Trial design

Primary purpose: Treatment

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: None (Open label)

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20 participants in 2 patient groups

EIT algorithm

Experimental group

Description:

Patients randomized to this arm will be ventilated at the PEEP level selected by the EIT algorithm, which selects a PEEP at which both collapse and hyperdistention are minimized.

Treatment:

Device: Electrical Impedance Tomography

ExPRESS algorithm

Active Comparator group

Description:

Patients randomized to this arm will be ventilated at the PEEP level selected by the ExPRESS algorithm, which is a method that targets a tidal volume of 6 ml/kg predicted body weight and then titrates PEEP until plateau airway pressure reaches 28 cm H2O.

Treatment:

Other: ExPRESS-derived PEEP level