Small Droplet Emission in Exhaled Breath During Different Breathing Manoeuvres: Implications for Clinical Lung Function Testing during COVID-19

Transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) within the healthcare setting is a major concern for infection prevention. In particular concern has been noted for small droplets (typically ≤5 microns), which have been shown to contain virus1 , as well as remaining airborne for longer, potentially increased spread2 . Modelling has shown particular spread of particles once exhaled during movement and exercise3 , but increases in exhaled particle mass are less well established, and likely to vary depending on breathing pattern. Pulmonary function testing (PFTs) is essential to respiratory medicine, and COVID-19 has had considerable implications4 . International guidance highlights PFTs as an aerosol generating procedure, but to date the varying response of different breathing manoeuvres have not been considered (see supplemental figure). The use of in-line filters are standard of care in many lung function labs, reducing the risk of viral and bacterial contamination. [Opening paragraph]