LAUSR

Background SARS-CoV-2 aerosolization during noninvasive positive pressure ventilation may endanger healthcare professionals. Various circuit setups have been described in order to reduce virus aerosolization. However, these setups may alter ventilator performances. Research question What are the consequences of the different suggested circuit setups on ventilator’s efficacy during continuous positive airway pressure (CPAP) and noninvasive ventilation (NIV)? Study Design and Method Eight circuit setups were evaluated on a bench made of a 3-D printed head and an artificial lung. Setups were a dual-limb circuit with an oro-nasal mask, a dual-limb circuit with a helmet interface, a single-limb circuit with a passive exhalation valve, three single-limb circuits with custom-made additional leaks and two single-limb circuits with active exhalation valves. All setups were evaluated during NIV and CPAP. The following variables were recorded: the inspiratory flow preceding trigger of the ventilator, the inspiratory effort required to trigger the ventilator, the triggering delay, the maximal inspiratory pressure delivered by the ventilator, the tidal volume (Vt) generated to the artificial lung, the total work of breathing (WOB) and the pressure time product to trigger the ventilator (PTPt). Results With NIV, the type of circuit setup had a significant impact on inspiratory flow preceding the trigger of the ventilator (p<0.0001), the inspiratory effort required to trigger the ventilator (p<0.0001), the triggering delay (p<0.0001); the maximal inspiratory pressure (p<0.0001), the Vt (p:0.0008), the WOB (p<0.0001), the PTPt (p<0.0001). Similar differences and consequences were seen with CPAP as well as with the addition of bacterial filters. Best performance was achieved using a dual limb circuit with an oro-nasal mask. Worst performance was achieved using a dual-limb circuit with a helmet interface. Interpretation Ventilator performance is significantly impacted by the circuit setup. The use of dual-limb circuit with oro-nasal masks should be used preferentially.