Semiautonomous ventilation in a porcine hemorrhage and lung injury model provides lung protective ventilation.

Background: Mechanical ventilation requires frequent reassessment from providers to ensure delivery of lung protective ventilation. However, in resource-limited settings, the time and attention lung protective ventilation requires are not always feasible. This study aimed to compare a physiologic closed-loop control (PCLC) ventilator capable of self-adjusting based on patient parameters against standard of care (SOC) ventilatory management in a porcine model.

Methods: The study compared SOC (n = 15) with PCLC (n = 15) for three porcine injury models: hemorrhage, lung injury, and hemorrhage with lung injury. Hemorrhage animals were progressively bled to three mean arterial pressures (60, 50, and then 40 mm Hg) and monitored for 60 minutes after each bleed. Lung injury used saline surfactant washout to a targeted PO2/fraction of inspired oxygen (FiO2) ratio of <250 mm Hg. Hemorrhage with lung injury combined surfactant washout followed by hemorrhage. Study end points were defined by the percent of time spent within target values: Acute Respiratory Distress Syndrome Network concordance, oxygenation (>96% with FiO2 0.21% or oxygen saturation [SpO2] <92% on FiO2 1.00%), tidal volume (4 ≤ VT/kg ≤ 10 mL/kg), and plateau pressure (≤30 cm H2O).

Results: Standard of care animals spent a lower percentage of time within targeted SpO2 range compared with PCLC (49% ± 25% vs. 68% ± 24% of time, p = 0.04) across all injury models, while all other parameters were comparable. In the hemorrhage group, the percentage of time within targeted SpO2 was also lower in SOC compared with PCLC (p = 0.01), while the remaining parameters, and all parameters within lung injury alone and hemorrhage with lung injury were otherwise equivalent (p > 0.05).

Conclusion: Physiologic closed-loop control performed equally to or better than SOC during both hemorrhage and lung injury. Physiologic closed-loop control has the potential to provide intensive care unit-level ventilator management in resource-limited circumstances, both in civilian and military operations.

Level of evidence: Therapeutic Study; Level III.