Aerosol Generation Risk of Chest Physiotherapy and Airway Clearance Techniques in Patients With COVID-19

Aerosol Generation Risk of Chest Physiotherapy and Airway Clearance Techniques in Patients With 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

Chest physiotherapy (CPT) and airway clearance are critical adjuncts for secretion management in individuals with neuromuscular weakness. Increased secretion volume in the context of SARS-CoV-2 infection makes secretion removal an important aspect of care. Given the potential, however, for greater aerosolization of secretions with these therapies, it is important to understand the precautions necessary when delivering this care.

Based on recent postmortem studies in patients with COVID-19, profuse viscous secretions were observed throughout the respiratory tract, indicating the need for pulmonary hygiene.^1,2 Therefore, employing the usual techniques of CPT, such as manual techniques, cough assist, use of nebulizers with positive pressure breathing devices, and intra/extra pulmonary high frequency oscillation devices, may be beneficial in COVID-19. While there are limited data on the utility of CPT in the acute phase of the disease, it may be useful during the recovery phase.³ To date, the biggest challenge in implementing CPT in these patients is the debate surrounding the risk of aerosolization with these procedures.

CPT encompasses an array of procedures that may each generate aerosol but need to be evaluated individually. Contrary to the perceived risk of aerosolization, many CPT techniques are not substantially aerosol-generating. For example, aerosol generated from nebulizers ceases to be airborne once it encounters mucosal secretions from patients due to an increase in particle size, corroborated in pooled risk analysis of three cohort studies evaluating the risk of infection in health care workers during the SARS epidemic.^4,5,6 Metered dose inhalers (MDIs) are considered safer alternatives to nebulizers since the drug is delivered in a closed chamber with comparatively shorter treatment time and less total aerosol mass than nebulizers.⁷ Nonetheless, drugs delivered by MDI or nebulizer treatments may induce cough, which can lead to bioaerosol generation from the patient.

Manual chest physiotherapy, consisting of cycles of deep breathing with percussion or vibration followed by an assisted cough, generates droplets >10 microns, which are most concentrated in the 1-meter radius closest to a patient.⁵ In contrast, positive pressure devices, such as cough assist, can theoretically generate more bioaerosol that travels a greater distance than other CPT techniques, though a lack of studies makes extrapolation of data from manual CPT challenging.

Given the uncertainty regarding aerosol generation risk, most national and international guidelines endorse the provision of CPT and airway clearance in hospital environments with proper personal protective equipment, in negative pressure rooms, and with viral-bacterial filters, when possible. For patients at home, we encourage self-management or supervised telemedicine to assist with implementation of chest physiotherapy if needed. Care should be taken for adequate handling and disposal of secretions with expectoration of the secretions in a closed bag/chamber with strict hand hygiene.^8,9,10

As we look to the future to try to understand the best use and necessary precautions for CPT and airway clearance in SARS-CoV-2 infection, ongoing work through NCT04654481 is looking at the feasibility of home-based high frequency chest wall oscillation devices in at-risk respiratory patients to decrease acute respiratory burden during the COVID-19 pandemic.

References

1. Scheuch G. Breathing is enough: for the spread of influenza virus and SARS-CoV-2 by breathing only. J Aerosol Med Pulm Drug Deliv. 2020;33(4):230-234
2. Dhand R and Li J. Coughs and sneezes: their role in transmission of respiratory viral infections, including SARS-CoV-2. Am J Respir Crit Care Med. Preprint. Posted online June 16, 2020. PubMed 32543913. doi: 10.1164/rccm.202004–1263PP
3. Abdullahi A. Safety and efficacy of chest physiotherapy in patients with COVID-19: a critical review. Front Med. 2020;7:454. doi:10.3389/fmed.2020.00454
4. Rotherham Doncaster and South Humber NHS Foundation Trust. Infection Prevention Control Manual. Aerosol generating procedures (appendix 46). Accessed April 23, 2020. https://www.rdash.nhs.uk/wp-content/uploads/2017/08/Appendix-46-Aerosol-Generating-Procedures.pdf
5. Simonds AK, Hanak A, Chatwin M, et al. Evaluation of droplet dispersion during non-invasive ventilation, oxygen therapy, nebulizer treatment and chest physiotherapy in clinical practice: implications for management of pandemic influenza and other airborne infections. Health Technol Assess. 2010;14(46):131-172. doi:10.3310/hta14460-02
6. Tran K, Cimon K, Severn M, et al. Aerosol generating procedures and risk of transmission of acute respiratory infections to healthcare workers: a systematic review. PloS One. 2012;7(4):e35797. doi:10.1371/journal.pone.0035797
7. Ari A. Practical strategies for a safe and effective delivery of aerosol medications to patients with COVID-19. Respir Med. 2020;167:105987
8. Lazzeri M, Lanza A, Bellini R, et al. Respiratory physiotherapy in patients with COVID-19 infection in acute setting: a Position Paper of the Italian Association of Respiratory Physiotherapists (ARIR). Monaldi Archives for Chest Disease. 2020;90:1285.
9. Wang TJ, Chau B, Lui M, et al. Physical medicine and rehabilitation and pulmonary rehabilitation for COVID-19. Am J Phys Med Rehabil. 2020;99(9):769-774. doi: 10.1097/PHM.0000000000001505
10. Alison JA, McKeough ZJ, Johnston K, et al. Australian and New Zealand Pulmonary Rehabilitation Guidelines. Respirology. 2017;22(4):800-819. doi:10.1111/resp.13025

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

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