Hong Kong Med J 2008;14(Suppl 1):S29-32
Understanding droplets produced by nebulisers and respiratory activities
YG Li, ATY Chwang, WH Seto, PL Ho, PL Yuen
Department of Mechanical Engineering, The University of Hong Kong, Hong Kong
1. The size of large droplets produced during respiratory activities such as coughing can be larger than 50-100 _ m. These droplets tend to evaporate quickly and contribute to both airborne and droplet transmission of disease.
2. Large droplets from respiratory activities can travel up to 1.5 m, which agrees well with the established range of infection due to droplet transmission. The distance between beds should be greater than 1.5 m.
3. Large droplets cannot be removed effectively from a room using currently available ventilation systems. Such droplets leave the air via surface deposition on floors, beds, and the patient’s body, etc.
4. Taking nasopharyngeal aspirates can stimulate coughing and promote aerosol generation.
5. Nebulisers generate very fine droplets (<1 µm) and large volumes can escape through the holes in ventilator facemasks. These fine droplets may be contaminated by the patient’s exhalation in the mask.