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. 2020 Jul;163(1):151-155.
doi: 10.1177/0194599820929275. Epub 2020 May 19.

Aerosolized Particle Reduction: A Novel Cadaveric Model and a Negative Airway Pressure Respirator (NAPR) System to Protect Health Care Workers From COVID-19

Tawfiq Khoury  1 , Pascal Lavergne  2 , Chandala Chitguppi  1 , Mindy Rabinowitz  1 , Gurston Nyquist  1 , Marc Rosen  1 , James Evans  2
Affiliations

Aerosolized Particle Reduction: A Novel Cadaveric Model and a Negative Airway Pressure Respirator (NAPR) System to Protect Health Care Workers From COVID-19

Tawfiq Khoury et al. Otolaryngol Head Neck Surg. 2020 Jul.

Abstract

Objectives: This study aimed to identify escape of small-particle aerosols from a variety of masks using simulated breathing conditions. This study also aimed to evaluate the efficacy of a negative-pressure environment around the face in preventing the escape of small aerosolized particles.

Study design: This study is an evaluation study with specific methodology described below.

Setting: This study was performed in our institution's fresh tissue laboratory.

Subjects and methods: A fixed cadaver head was placed in a controlled environment with a black background, and small-particle aerosols were created using joss incense sticks (mass-median aerosol diameter of 0.28 µ). Smoke was passed through the cadaver head, and images were taken with a high-resolution camera in a standardized manner. Digital image processing was used to calculate relative amounts of small-particle escape from a variety of masks, including a standard surgical mask, a modified Ambu mask, and our negative airway pressure respirator (NAPR).

Results: Significant amounts of aerosolized particles escaped during the trials with no mask, a standard surgical mask, and the NAPR without suction. When suction was applied to the NAPR, creating a negative-pressure system, no particle escape was noted.

Conclusion: We present a new and effective method for the study of small-particle aerosols as a step toward better understanding the spread of these particles and the transmission of coronavirus disease 2019. We also present the concept of an NAPR to better protect health care workers from aerosols generated from the upper and lower airways.

Keywords: COVID-19; aerosol; mask; rhinology; skull base.

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Figures

Figure 1.
Figure 1.
Trial without mask. (A) The first photo in the run without thresholding. (B) The first photo in the run after thresholding was performed. (C) This is the image 2 seconds into the run. A considerable amount of smoke can be seen emanating from the cadaver’s nose, mouth, and over the cadaver’s chin. (D) This image was generated by subtracting image B from image C.
Figure 2.
Figure 2.
Standard surgical mask trial. (A) The first photo in the run without thresholding. (B) The first photo in the run after thresholding was performed. (C) This is the image 2 seconds into the run. Smoke was noted to escape from the top and sides of the mask. (D) This image was generated by subtracting image B from image C.
Figure 3.
Figure 3.
Negative airway pressure respirator (NAPR) with no suction. (A) The first photo in the run without thresholding. (B) The first photo in the run after thresholding was performed. (C) This is the image 2 seconds into the run. Smoke escaped from the aperture in the middle of the mask. (D) This image was generated by subtracting image B from image C.
Figure 4.
Figure 4.
Trial with the negative airway pressure respirator (NAPR) with the suction at −120 mm Hg. (A) The first photo in the run without thresholding. (B) The first photo in the run after thresholding was performed. (C) This is the image 2 seconds into the run. No smoke was able to escape. (D) This image was generated by subtracting image B from image C.
Figure 5.
Figure 5.
Working through the negative airway pressure respirator (NAPR). (A, B) These images show how a simple modification of an Ambu mask can create a negative-pressure environment to help protect health care workers when applied to a patient. (C, D) These images show working through the NAPR with no noted aerosol escape.
See this image and copyright information in PMC

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