Development of an Easily Reproducible Cough Simulator With Droplets and Aerosols for Rapidly Testing Novel Personal Protective Equipment.

INTRODUCTION: The current COVID-19 pandemic has produced numerous innovations in personal protective equipment, barrier devices, and infection mitigation strategies, which have not been validated. During high-risk procedures such as airway manipulation, coughs are common and discrete events that may expose healthcare workers to large amounts of viral particles. A simulated cough under controlled circumstances can rapidly test novel devices and protocols and thus aid in their evaluation and the development of implementation guidelines. Physiologic cough simulators exist but require significant expertise and specialized equipment not available to most clinicians. METHODS: Using components commonly found in healthcare settings, a cough simulator was designed for clinicians to easily assemble and use. Both droplet and aerosol particle generators were incorporated into a bimodal experimental system. High-speed flash photography was used for data collection. RESULTS: Using a gas flow analyzer, video recordings, and high-speed digital photography, the cough and particle simulators were quantitatively and qualitatively compared with known physiologic cough parameters and in vivo Schlieren imaging of human coughs. CONCLUSIONS: Based on our validation studies, this cough and particle simulator model approximates a physiologic, human cough in the context of testing personal protective equipment, barrier devices, and infection prevention measures.

Barrier Devices, Intubation, and Aerosol Mitigation Strategies: Personal Protective Equipment in the Time of Coronavirus Disease 2019.

BACKGROUND: Numerous barrier devices have recently been developed and rapidly deployed worldwide in an effort to protect health care workers (HCWs) from exposure to coronavirus disease 2019 (COVID-19) during high-risk procedures. However, only a few studies have examined their impact on the dispersion of droplets and aerosols, which are both thought to be significant contributors to the spread of COVID-19. METHODS: Two commonly used barrier devices, an intubation box and a clear plastic intubation sheet, were evaluated using a physiologically accurate cough simulator. Aerosols were modeled using a commercially available fog machine, and droplets were modeled with fluorescein dye. Both particles were propelled by the cough simulator in a simulated intubation environment. Data were captured by high-speed flash photography, and aerosol and droplet dispersion were assessed qualitatively with and without a barrier in place. RESULTS: Droplet contamination after a simulated cough was seemingly contained by both barrier devices. Simulated aerosol escaped the barriers and flowed toward the head of the bed. During barrier removal, simulated aerosol trapped underneath was released and propelled toward the HCW at the head of the bed. Usage of the intubation sheet concentrated droplets onto a smaller area. If no barrier was used, positioning the patient in slight reverse Trendelenburg directed aerosols away from the HCW located at the head of the bed. CONCLUSIONS: Our observations imply that intubation boxes and sheets may reduce HCW exposure to droplets, but they both may merely redirect aerosolized particles, potentially resulting in increased exposure to aerosols in certain circumstances. Aerosols may remain within the barrier device after a cough, and manipulation of the box may release them. Patients should be positioned to facilitate intubation, but slight reverse Trendelenburg may direct infectious aerosols away from the HCW. Novel barrier devices should be used with caution, and further validation studies are necessary.

Intraoperative aerosol box use: does an educational visual aid reduce contamination?

BACKGROUND: The aerosol box was rapidly developed and disseminated to minimize viral exposure during aerosolizing procedures during the COVID-19 pandemic, yet users may not understand how to use and clean the device. This could potentially lead to increased viral exposure to subsequent patients and practitioners. We evaluated intraoperative contamination and aerosol box decontamination and the impact of a preoperative educational visual aid. METHODS: Using a double-blinded randomized design, forty-four anesthesiology trainees and faculty completed a simulated anesthetic case using an aerosol box contaminated with a fluorescent marker; half of the subjects received a visual aid prior to the simulation. Intraoperative contamination was evaluated at 10 standardized locations using an ultraviolet (UV) light. Next, subjects were instructed to clean the aerosol box for use on the next patient. Following cleaning, the box was evaluated for decontamination using an UV light. RESULTS: Median total contamination score was significantly reduced in the experimental group (5.0 vs. 10.0, P < 0.001). The aerosol box was completely cleaned by 36.4% of subjects in the experimental group compared to 4.5% in the control group (P = 0.009). CONCLUSIONS: The use of a visual aid significantly decreased intraoperative contamination and improved box cleaning. Despite these findings, a potentially clinically significant amount of viral exposure may exist. Thorough evaluation of the risks and benefits of the aerosol box should be completed prior to use. If an aerosol box is used, a visual aid should be considered to remind practitioners how to best use and clean the box.

Differential Ventilation Using Flow Control Valves as a Potential Bridge to Full Ventilatory Support during the COVID-19 Crisis.

BACKGROUND: During the COVID-19 pandemic, ventilator sharing was suggested to increase availability of mechanical ventilation. The safety and feasibility of ventilator sharing is unknown. METHODS: A single ventilator in pressure control mode was used with flow control valves to simultaneously ventilate two patients with different lung compliances. The system was first evaluated using high-fidelity human patient simulator mannequins and then tested for 1 h in two pairs of COVID-19 patients with acute respiratory failure. Patients were matched on positive end-expiratory pressure, fractional inspired oxygen tension, and respiratory rate. Tidal volume and peak airway pressure (PMAX) were recorded from each patient using separate independent spirometers and arterial blood gas samples drawn at 0, 30, and 60 min. The authors assessed acid-base status, oxygenation, tidal volume, and PMAX for each patient. Stability was assessed by calculating the coefficient of variation. RESULTS: The valves performed as expected in simulation, providing a stable tidal volume of 400 ml each to two mannequins with compliance ratios varying from 20:20 to 20:90 ml/cm H2O. The system was then tested in two pairs of patients. Pair 1 was a 49-yr-old woman, ideal body weight 46 kg, and a 55-yr-old man, ideal body weight 64 kg, with lung compliance 27 ml/cm H2O versus 35 ml/cm H2O. The coefficient of variation for tidal volume was 0.2 to 1.7%, and for PMAX 0 to 1.1%. Pair 2 was a 32-yr-old man, ideal body weight 62 kg, and a 56-yr-old woman, ideal body weight 46 kg, with lung compliance 12 ml/cm H2O versus 21 ml/cm H2O. The coefficient of variation for tidal volume was 0.4 to 5.6%, and for PMAX 0 to 2.1%. CONCLUSIONS: Differential ventilation using a single ventilator is feasible. Flow control valves enable delivery of stable tidal volume and PMAX similar to those provided by individual ventilators.