Airflow and droplet spreading around oxygen masks: A simulation model for infection control research
Background
Respiratory assist devices, such as oxygen masks, may enhance the potential to spread infectious aerosols from patients with respiratory infections.
Methods
A technique was developed to visualize exhaled aerosols during simulated patients' use of oxygen masks in a health care setting and tested using the simple, the nonrebreathing, and the Venturi oxygen masks. A smoke tracer was introduced into one of the lungs of the model to enable it to mix with the incoming oxygen and then to be further inhaled/exhaled by the model according to a variety of realistic respiratory settings (14, 24, and 30 breaths per minute, with tidal volumes of 500, 330, 235 mL, respectively) and oxygen supply flow rates (between 6 and 15 liters per minute). Digital recordings of these exhaled airflow patterns allowed approximate distances to be estimated for the extent of the visible exhaled air plumes emitted from each oxygen mask type at these settings.
Results
It was found that the simple, the nonrebreathing, and the Venturi-type oxygen masks produced exhaled smoke plumes over minimum distances of 0.08 to 0.21 m, 0.23 to 0.36 m, and 0.26 to 0.40 m, respectively.
Conclusion
Health care workers may therefore consider any area within at least 0.4 m of a patient using such oxygen masks to be a potential nosocomial hazard zone.
aCentre for Emerging Infectious Diseases, School of Public Health, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China
bDepartment of Microbiology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China
cDepartment of Medicine and Therapeutics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China
dDepartment of Building and Construction, City University of Hong Kong, Kowloon, Hong Kong SAR, China
eDepartment of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China
fSchool of Mechanical Engineering, University of New South Wales, Sydney, Australia
Address correspondence to Julian W. Tang, MRCPath, Department of Microbiology, Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong SAR, China.
Supported by the Research Fund for the Control of Infectious Diseases (RFCID) from the Health, Welfare, and Food Bureau of the Hong Kong SAR government (grant No. CUHK-CS-002; to project team).
ABSTRACT