Review and demonstration of equations applied to models of filtering facepiece respirator particle capture efficiency.

The use of filtering facepiece respirators (FFRs) of various types increased dramatically by both workers and the public during the ongoing COVID-19 pandemic. This increased use has, likewise, instigated a proliferation of research on the qualities of FFRs. An aspect of FFR development and optimization involves the use of mathematical models that predict filter efficiency based on various filter characteristics while also considering a number of particle capture forces. An evaluation of current literature failed to identify a publication that provides a comprehensive assessment of the models developed to predict filter efficiency. The purpose of this review was, therefore, to describe models developed to include the forces associated with diffusion, interception, impaction, and electrostatic attraction as they contribute to the efficiency of an entire filter. The literature review was augmented with figures created with the use of many of the models discussed to compare different models of the same force as well as to illustrate the influence of electrostatic forces on overall filter efficiency.

Characterization of performance and disinfection resilience of nonwoven filter materials for use in 3D-printed N95 respirators.

The COVID-19 pandemic has caused a high demand for respiratory protection among health care workers in hospitals, especially surgical N95 filtering facepiece respirators (FFRs). To aid in alleviating that demand, a survey of commercially available filter media was conducted to determine whether any could serve as a substitute for an N95 FFR while held in a 3D-printed mask (Stopgap Surgical Face Mask from the NIH 3D Print Exchange). Fourteen filter media types and eight combinations were evaluated for filtration efficiency, breathing resistance (pressure drop), and liquid penetration. Additional testing was conducted to evaluate two filter media disinfection methods in the event that the filters were reused in a hospital setting. Efficiency testing was conducted in accordance with the procedures established for approving an N95 FFR. One apparatus used a filter-holding device and another apparatus employed a manikin head to which the 3D-printed mask could be sealed. The filter media and combinations exhibited collection efficiencies varied between 3.9% and 98.8% when tested with a face velocity comparable to that of a standard N95 FFR at the 85 L min-1 used in the approval procedure. Breathing resistance varied between 10.8 to >637 Pa (1.1 to > 65 mm H2O). When applied to the 3D-printed mask efficiency decreased by an average of 13% and breathing resistance increased 4-fold as a result of the smaller surface area of the filter media when held in that mask compared to that of an N95 FFR. Disinfection by dry heat, even after 25 cycles, did not significantly affect filter efficiency and reduced viral infectivity by > 99.9%. However, 10 cycles of 59% vaporized H2O2 significantly (p < 0.001) reduced filter efficiency of the media tested. Several commercially available filter media were found to be potential replacements for the media used to construct the typical cup-like N95 FFR. However, their use in the 3D-printed mask demonstrated reduced efficiency and increased breathing resistance at 85 L min-1.

Aerosols, airflow, and airspace contamination during laparoscopy.

Laparoscopic surgery has been undermined throughout the COVID-19 pandemic by concerns that it may generate an infectious risk to the operating team through aerosolization of peritoneal particles. There is anyway a need for increased awareness and understanding of the occupational hazard for surgical teams regarding unfiltered escape of pollutants generated by surgical smoke and other microbials. Here, the aerosol-generating nature of this access modality was confirmed through repeatable real-time methodology both qualitatively and quantitively to inform best practice and additional engineering solutions to optimize the operating room environment.

Laparoscopic surgery has been undermined throughout the COVID-19 pandemic by concerns that it may generate an infectious risk to the operating team through aerosolization of peritoneal particles. There is anyway a need for increased awareness and understanding of the occupational hazard for surgical teams regarding unfiltered escape of pollutants generated by surgical smoke and other microbials. Here, the aerosol-generating nature of this access modality was confirmed through repeatable real-time methodology both qualitatively and quantitively to inform best practice and additional engineering solutions to optimize the operating room environment.

Quality Assurance During a Global Pandemic: An Evaluation of Improvised Filter Materials for Healthcare Workers.

OBJECTIVE: The proliferation of improvised masks during the COVID-19 pandemic has raised questions regarding filter effectiveness and safety. We sought to compare the effectiveness of commonly used improvised filter materials against N95 industry standards. METHODS: Six different filter materials commonly used in the community were tested using both single- and multi-layer configurations with the TSI 8130 automated filter tester in accordance with National Institute for Occupational Safety and Health (NIOSH) standards for N95 respirators. RESULTS: Only three of the tested filter material configurations met N95 parameters with regard to filtration efficiency and pressure drop across the filter material-the: True-high-efficiency particulate air (HEPA) filter, four-layer MERV 13 and 14 HVAC filters. CONCLUSIONS: Many proposed filter materials for improvised masks do not meet current industry standards and may pose safety and efficacy concerns. Care should be taken when selecting materials for this critical respirator component, particularly for health care workers or others at high risk for pathogen exposure.

Endoscopic skull base and transoral surgery during COVID-19 pandemic: Minimizing droplet spread with negative-pressure otolaryngology viral isolation drape.

BACKGROUND: The coronavirus disease (COVID-19) pandemic has raised concern of transmission of infectious organisms through aerosols formation in endonasal and transoral surgery. METHODS: Retrospective review. We introduce the negative-pressure otolaryngology viral isolation drape (NOVID) system to reduce the risk of aerosol. NOVID consists of a plastic drape suspended above the patient's head and surgical field with a smoke evacuator suction placed inside the chamber. RESULTS: Four patients underwent endonasal (4) and endo-oral surgery (1). Fluorescein was applied to the surgical field. Black light examination of fluorescein-treated operative fields revealed minimal contamination distant to the surgical field. In two prolonged cases with high-speed drilling, droplets were identified under the barrier and on the tip of the smoke evacuator. Instruments and cottonoids appeared to be a greater contributor to field contamination. CONCLUSIONS: Negative-pressure aspiration of air under a chamber barrier, which appears to successfully keep aerosol and droplet contamination to a minimum.