Self-contained system for mitigation of contaminated aerosol sources of SARS-CoV-2

Abstract

Contaminated aerosols and micro droplets are easily generated by infected hosts through sneezing, coughing, speaking and breathing^1-3 and harm humans' health and the global economy. While most of the efforts are usually targeted towards protecting individuals from getting infected,⁴ eliminating transmissions from infection sources is also important to prevent disease transmission. Supportive therapies for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS CoV-2) pneumonia such as oxygen supplementation, nebulizers and non-invasive mechanical ventilation all carry an increased risk for viral transmission via aerosol to healthcare workers.^5-9 In this work, we study the efficacy of five methods for self-containing aerosols emitted from infected subjects undergoing nebulization therapies with a diverse spectrum on oxygen delivery therapies. The work includes five study cases: Case I: Use of a Full-Face Mask with biofilter in bilevel positive airway pressure device (BPAP) therapy, Case II: Use of surgical mask in High Flow Nasal Cannula (HFNC) therapy, Case III: Use of a modified silicone disposable mask in a HFNC therapy, Case IV: Use of a modified silicone disposable mask with a regular nebulizer and normal breathing, Case V: Use of a mitigation box with biofilter in a Non-Invasive Positive Pressure Ventilator (NIPPV). We demonstrate that while cases I, III and IV showed efficacies of 98-100%; cases II and V, which are the most commonly used, resulted with significantly lower efficacies of 10-24% to mitigate the dispersion of nebulization aerosols. Therefore, implementing cases I, III and IV in health care facilities may help battle the contaminations and infections via aerosol transmission during a pandemic.

Figure 1.. Nebulization Aerosol Dispersion.

a) Particle count concentration during HFNC treatment with 21% of Oxygen, 30 L/min of air flow rate and nebulization with 3 ml of medicine in saline physiological solution to a COVID-19 patient, respiratory exercise therapy and toilet flushing activity. The aerosol particle count profiles are simultaneously taken at 3 different positions of: 3 feet (----), 6 feet (–––) and 9 feet (····) from the subject by an aerosol particle counter system (DL). The subject has no mitigation mask. b) Experimental design for testing the nebulization’s aerosol dispersion in the patient’s room (air exchange rate = 20 h⁻¹).

Figure 2.. Efficacy of aerosol mitigation systems applied in this work during nebulization.

Total volume of nebulization solution: 3 mL. The is efficacy for different study cases is assessed from particle count concentration vs. time profiles obtained during simulated nebulization therapies and includes a) peak analysis with (Eq. 1), b) area under the curve with (Eq. 2). Study cases correspond to (I): biofilter with fully sealed Full-Face Mask in BPAP oxygen therapy with filter, (II) surgical mask in HFNC, (III) modified silicone mask with biofilter and fan in HFNC, (IV) modified silicone mask with biofilter and fan in normal breathing, and (V) FFM with box mitigation. A piezoelectric nebulizer is used Cases I-III and V, and mechanical pump nebulizer is used in Case IV. c) Example of particle count concentration vs. time profiles assessed at distance of 3 feet from the subject during the simulated nebulization therapy for Case IV. Rectangular area at the bottom shows the room’s particle baseline levels. Aerosol level obtained in absence (----) and presence (----) of the mitigation system: modified silicone mask with biofilter and fan.

Figure 3.. Different cases of combination of oxygen therapy and mitigation systems for nebulization.

a) See text for description of Cases I-V. b) Silicone Mask* built for nebulization aerosol mitigation (see text for more details).