Optimized Aerosol Hood Design Performance and Clinical Efficacy to Protect Health Care Workers from Nosocomial Infection

Abstract

Health Care Workers (HCWs) are the most vulnerable group of professionals for SARS-CoV-2 virus infection via airborne or direct contact. The current main three protective methods are PPE, training, and the hospital’s ventilations with negative pressure rooms. Negative pressure rooms are limited in availability in any hospital network. PPE and training also have the side effects of headache, skin injury and importantly, inconsistent donning and doffing procedures that affect the health and productivity of HCWs. Therefore, there is a clinical unmet need for additional modes of protection for HCWs against nosocomial infection.An aerosol hood is a partially enclosed negative pressure chamber placed around the head of a patient to mitigate HCWs exposure during aerosol generating clinical procedures such as intubation. The optimized aerosol hood design is intended to be an engineering control to protect HCWs by combining a physical isolation hood with negative pressure system. The objective of this thesis is to1) model droplet trajectories and evaporation/settling rates and translate to the aerosol hood design performance; 2) to assess the optimized aerosol hood design performance; and 3) to evaluate the clinical efficacy of the aerosol hood during simulated intubation procedures. Droplet trajectory modeling revealed that smaller droplets evaporate within 5 seconds in the aerosol hood and would get cleared by the negative pressure system, while larger droplets would follow an exhaled jet path impacting inside the aerosol hood. An aerosol hood design performance was assessed by measuring particle penetration, Air Exchange Time, and Air Changes per Hour (ACH). At a half power blower setting, the particle penetration resulted in 10-4 with a corresponding protection efficiency of 99.99%. The aerosol hood has an average Air Exchange Time of 2.76 minutes for a 99.9% reduction using a half power blower setting and an average of 151.44 Air Changes per Hour (ACH). The clinical efficacy was studied in a simulated intubation procedure by measuring the aerosol exposure in the room and particle deposition on the participants’ PPE. Bedside location to the SIM-man had a higher particle concentration exposure than a background location, however, when the negative pressure system aerosol hood is used, the bedside location has a lower particle concentration similar to the background exposure. Particle deposition decreased by 42% for the face shield and gowns: and 32% increase on the gloves when measuring the on participants’ PPE substrate. Overall, the optimized aerosol hood design has a high performance in clearance of human respiratory droplets and aerosols due to its design feature of a physical isolation and negative pressure system. The clinical study has shown the efficacy of the aerosol hood technology and promising in supplementing PPE and hospital’s negative pressure rooms to protect HCWs against nosocomial infection.