Development and demonstration of the protective efficacy of a convertible respiratory barrier enclosure: a simulation study

Objective The efficacy of previously developed respiratory barrier enclosures to limit healthcare workers’ exposure to aerosols from COVID-19 patients remains unclear; in addition, the design of these devices is unsuitable for transportation or other emergency procedures. Therefore, we developed a novel negative pressure respiratory isolator to improve protection from patient-generated aerosols and evaluated its protective effect in conversion to systemic isolator. Methods This in vitro study simulated droplets by nebulizing 1% glycerol + 99% ethanol solution. We performed cardiopulmonary resuscitation (CPR) and converted a respiratory barrier enclosure into a systemic isolator with a respiratory barrier as well as a respiratory barrier with negative pressure generator (NPG), which were compared with control and room air. During the procedure, particles were counted for 30 seconds and the count was repeated 10 times. Results During CPR, the total number of particles in the respiratory barrier with NPG (280,529; interquartile range [IQR], 205,263–359,195; P=0.970) was similar to that in the control (308,789; IQR, 175,056–473,276). Using NPG with a respiratory barrier reduced the number of particles to 27,524 (IQR, 26,703–28,905; P=0.001). Particle number during conversion of the respiratory barrier into a systemic isolator was also lower than in the control (25,845; IQR, 19,391–29,772; P=0.001). Conclusion The novel isolator was converted to a systemic isolator without air leakage. The aerosol-blocking effect of the isolator was quantified using a particle counter during CPR. Further studies comparing the barrier effect of isolators within various pressure differentials are warranted.