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

Abstract

Introduction Lung 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. Methods Healthy 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 once each second using both 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. Results 33 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 similar peak aerosol emission as talking, and addition of a viral filter to the mouthpiece reduced peak flow aerosol emission to similar levels. The filter made little difference to recorded peak flow values. FENO measurement produced negligible aerosol. Re usable CPET masks with filter reduced aerosol emission when breathing, speaking, and coughing significantly. Conclusions Compared to voluntary coughing, all lung function testing produced less aerosol. Filtered spirometry produces similar peak aerosol emission to speaking, 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.

Real-life measurement of size-fractionated aerosol concentration in a plethysmography box during the COVID-19 pandemic and estimation of the associated viral load

“…Present results seem to underpin this hypothesis, as in the case of 69% of the measurements we could detect a statistically significant increase of particle concentration. The increase was slightly higher than that obtained by [8] but lower than those reported by [7]. It is worth noting that four patients had a cough during the measurements, which may have further increased the number of generated particles.…”

“…In the months following the first pandemic peak in 2020 efforts were spent to reveal whether PFTs are significant sources of aerosol generation and whether the increase in transmission of risk associated with PFT is real or not [5]- [8]. The values of the increase in particle concentration attributable to PFT documented in the above studies span between a few hundreds of particles up to more thousands of particles per litre, but there were notable differences among the studies regarding the circumstances.…”

Comparing aerosol number and mass exhalation rates from children and adults during breathing, speaking and singing

“…Figure 2 compares the ranges of aerosol number concentrations generated by children ( n = 18) and adults ( n = 118, aggregate cohort across PERFORM and AERATOR studies) [ 4 , 31 , 34 , 36 ] while breathing and speaking at 70–80 dBA. For both breathing and speaking and across both cohorts, differences in aerosol generation among individuals are lognormally distributed, consistent with previous comparisons of aerosol generation across smaller cohorts [ 4 , 31 ].…”

“…Figure2compares the ranges of aerosol number concentrations generated by children (n = 18) and adults (n = 118, aggregate cohort across PERFORM and AERATOR studies)[4,31,34,36] …”