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.


CONCLUSIONS
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.
Centre for Emerging Infectious Diseases, School of Public Health, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China.
Margaret
M
Ip
Julian W
JW
Tang
David S C
DS
Hui
Alexandra L N
AL
Wong
Matthew T V
MT
Chan
Gavin M
GM
Joynt
Albert T P
AT
So
Stephen D
SD
Hall
Paul K S
PK
Chan
Joseph J Y
JJ
Sung
D000336:Aerosols / Q000009:adverse effects / Q000032:analysis*; D004867:Equipment Design; D045853:Exhalation; D006801:Humans; D017053:Infection Control; D017758:Infectious Disease Transmission, Patient-to-Professional; D008397:Masks / Q000009:adverse effects*; D010102:Oxygen Inhalation Therapy / Q000295:instrumentation*; D016544:Patient Simulation; D012141:Respiratory Tract Infections / Q000635:transmission*; D012906:Smoke / Q000032:analysis; D014741:Video Recording
D000336:Aerosols; D012906:Smoke