Characterization and Optimization of the Subsalve Helmet Ventilation Circuit in a High-Fidelity Acute Respiratory Distress Syndrome (ARDS) Lung Model

John Donahue,1 Clinton O Chichester III,1 Alex Hornstein,2 Michael Lombardi,3 Amanda M Chichester4 1Department of Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, RI, USA; 2Inventilator LLC, Pawtucket, RI, USA; 3Lombardi Undersea LLC, Middletown, RI, USA; 4Department of Pharmacy Practice and Clinical Research, University of Rhode Island, Kingston, RI, USACorrespondence: Amanda M Chichester, Department of Pharmacy Practice and Clinical Research, University of Rhode Island, Avedisian Hall, 7 Greenhouse Road, Kingston, RI, USA, Tel +1-401-874-5037, Email [email protected]: The Subsalve helmet continuous positive airway pressure (CPAP) circuit is a low-cost, easy to implement non-invasive ventilation option for treatment of acute respiratory failure. The circuit is simple to set up and operate, and is designed to be used with any commonly available continuous positive airway pressure device.Model (Materials) and Methods: Simulation of an acute respiratory distress syndrome (ARDS) patient allows optimization of treatment parameters without risk. The boundaries of safe and effective helmet CPAP treatment were measured in the TestChest® lung simulator with AQAI SIS software. The capabilities of the TestChest allow for representation of complex breathing patterns, simulation of muscular fatigue, and the ability to model patients with worsening ARDS. Treatment settings were tested by varying CPAP pressure and oxygen flow rate in a simulated ARDS patient.Results: Moderate CPAP pressure led to significant increases in SpO2 (oxygen saturation) (10% increase at 14 cmH2O pressure) and maintained improvements compared to the control even at the latest stage of the disease. When oxygen was introduced, patient SpO2 increased proportional to the oxygen flow rate. 5 liters per minute (LPM) oxygen increased patient SpO2 by 3% in the severe ARDS model and 30 LPM oxygen increased SpO2 by 7%. Moderate pressure led to significant increases in SpO2 comparable to high concentrations of oxygen. CO2 does not accumulate in the helmet as long as the minimal flow rate (60 LPM of air) is maintained during treatment.Conclusion: Our data demonstrate that the Subsalve helmet CPAP circuit, with limited oxygen availability, is an effective treatment strategy for ARDS patients in low-resource settings. Moderate positive end expiratory pressure (PEEP) is recommended to improve blood oxygenation. Subsalve has the potential to conserve critical resources in future epidemics.Keywords: acute respiratory distress syndrome, noninvasive ventilation, continuous positive airway pressure, helmet-CPAP, positive end expiratory pressure