Aerosolization Risks of Noninvasive Ventilation in the Era of COVID-19
COVID IN FOCUS: PERSPECTIVES ON THE LITERATURE
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Aerosolization Risks of Noninvasive Ventilation in the Era of COVID-19
By: Sherri L. Katz, MDCM, MSc, FRCPC, FCCP; Meredith Kendall Greer, MD; and Ashima S. Sahni, MD, FCCP
Home-Based Mechanical Ventilation and Neuromuscular Disease Network
Published: April 9, 2021
At the beginning of the COVID-19 pandemic, great concern was raised about the aerosolization of infectious droplets with noninvasive ventilation (NIV), which could propagate the spread of SARS-CoV-2. Aerosolized particles, generally less than 5-100 microns in size, persist longer in the air compared with larger droplets and have the potential to travel further distances.
Although we do not know the concentration of virus in these particles, it is suspected that infection risk would increase with increasing particle concentration and trajectory.1 As NIV is widely used in the treatment of patients with both acute and chronic respiratory disease, it is paramount that we understand the safety of its use in patients with suspected or confirmed COVID-19.
Emerging evidence from hospital environments has begun to challenge the dogma that NIV is a higher risk delivery method for viral particle dispersion.1 Two studies show that aerosol generation with NIV is not different—or indeed is lower—than with oxygen delivery devices.2,3 While other factors may have also contributed to the decreased aerosol dispersion seen in these studies, namely the use of negative pressure rooms and in-line HEPA filters, there are potential biological mechanisms that may explain the lower than expected aerosol generation with NIV. One thought is that high gas flow opposes exhalation of patient-generated bioaerosol and/or greater dispersion of aerosol droplets. Another theory, termed the bronchiole fluid film burst model, postulates that it is the opening of closed bronchioles that generates aerosol by stretching out a film of fluid, which then bursts, creating aerosol that travels to the alveoli and is then exhaled. The greater positive end-expiratory pressure generated with NIV may prevent closure of small bronchioles and avoid this phenomenon.2
The use of helmet NIV, nonvented masks, and in-line HEPA filters all appear to curtail the spread of aerosol droplets to a greater degree, although these may not be appropriate for children or in-home or sleep laboratory environments. Ensuring a good interface seal also minimizes aerosol dispersion.3 These factors become increasingly important in environments outside the hospital, such as a home or sleep laboratory, which do not have the benefit of high ventilation rates that further dilute aerosol and reduce exposure of individuals close to the source.4 Appropriate personal protective equipment should therefore be worn at all times when caring for individuals using NIV, and extra caution is recommended in environments outside of hospitals.
References
- Li J, Ehrmann S. High-flow aerosol-dispersing versus aerosol-generating procedures. Am J Respir Crit Care Med. 2020;202(8):1069-1071.
- Gaeckle NT, Lee J, Park Y, et al. Aerosol generation from the respiratory tract with various modes of oxygen delivery. Am J Respir Crit Care Med. 2020;202(8):1115-1124.
- Avari H, Hiebert RJ, Ryzynski AA, et al. Quantitative assessment of viral dispersion associated with respiratory support devices in a simulated critical care environment. Am J Respir Crit Care Med. 2021.
- Sze To GN, Wan MP, Chao CYH, et al. Experimental study of dispersion and deposition of expiratory aerosols in aircraft cabins and impact on infectious disease transmission. Aerosol Science and Technology. 2009;43(5):466-485.
Ashima S. Sahni, MD, FCCP
• Assistant Professor of Clinical Medicine and Associate Program Director, Sleep Medicine Fellowship, in the Division of Pulmonary, Critical Care, Sleep and Allergy, Department of Medicine, at the University of Illinois at Chicago
Sherri L. Katz, MDCM, MSc, FRCPC, FCCP
• Pediatric Respirologist and Division Chief of Pediatric Respirology, Children's Hospital of Eastern Ontario; Senior Scientist, Children's Hospital of Eastern Ontario Research Institute; and Associate Professor, University of Ottawa
Meredith Kendall Greer, MD
• Sleep Medicine Fellow in the Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine, Department of Medicine, at Emory University in Atlanta, GA
Read more COVID in Focus: Perspectives on the Literature:
Aerosol Generation Risk of Chest Physiotherapy and Airway Clearance Techniques in Patients With COVID-19
Asthma and COVID-19
Obstructive Sleep Apnea as a Risk Factor for Adverse Outcomes in COVID-19
Timing of Intubation in Patients With COVID-19