Risk and mitigation of aerosolisation from lung function testing: results from the AERATOR study

IntroductionLung function tests are fundamental diagnostic and monitoring tools for patients with respiratory symptoms. There is significant uncertainty around whether potentially infectious aerosol is produced during different lung function testing modalities; and limited data on possible mitigation strategies to reduce risk to staff and limit fallow time.MethodsHealthy volunteers were recruited in an ultraclean, laminar flow theatre and had standardised spirometry as per ERS/ATS guidance, as well as peak flow measurement and FENO assessment of airway inflammation. Aerosol emission was sampled minimum once each second using both an Aerodynamic Particle Sizer (APS) and Optical Particle Sizer (OPS), and compared to breathing, speaking and coughing. Mitigation strategies such as a peak flow viral filter and a CPET facemask (to mitigate induced coughing) were tested.Results33 healthy volunteers were recruited. Aerosol emission was highest in cough (1.61 particles/cm3/sample), followed by unfiltered peak flow (0.76 particles/cm3/sample). Filtered spirometry produced lower peak aerosol emission (0.11 particles/ cm3/sample) than that of a voluntary cough, and addition of a viral filter to the mouthpiece reduced peak flow aerosol emission to similar levels. The filter made little difference to recorded FEV peak flow values. Peak aerosol FENO measurement produced negligible aerosol. Reusable CPET masks with filter reduced aerosol emission when breathing, speaking, and coughing significantly.ConclusionsCompared to voluntary coughing, all lung function testing produced fewer aerosol particles. Filtered spirometry produces lower peak aerosol emission than peak voluntary coughing, and should not be deemed an aerosol generating procedure. The use of viral filters reduces aerosol emission in peak flow by > 10 times, and has little impact on recorded peak flow values. CPET masks are a useful option to reduce aerosol emission from induced coughing while performing spirometry.