T5 Respiratory particle and droplet emission during speech and exercise

Abstract

<h3>Background</h3> The coronavirus disease-19 (COVID-19) pandemic has profoundly impacted sports and exercise, disrupting a plethora of events worldwide. Aerosol transmission is increasingly recognised as an important route for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with systematic evaluation of particulate matter release during exercise required to understand and mitigate transmission risk. <h3>Methods</h3> Healthy participants (n=25) performed a two stepped, flat-wave cardiopulmonary exercise test (CPET) on a cycle ergometer to replicate vigorous exercise (80% of anaerobic workload) and high intensity exercise (anaerobic workload + 30% of the difference between anaerobic workload and peak workload), as determined by a maximally exhaustive CPET performed one hour previously. Concurrent measurements of aerosol and ventilatory data were recorded via a sampling line connected to an aerodynamic particle sizer (APS). Further synchronous data were collected at rest and when speaking at 70-80dBA. Droplet data were collected at rest and during high intensity exercise, using water sensitive paper. <h3>Findings</h3> Median aerosol number concentration during speaking (at 70-80dBA), 0·26cm^-3, was greater than during vigorous exercise, 0·12 cm^-3 (p&lt;0·001) but not different to high intensity exercise, 0.24cm^-3 (p=0·92). Median aerosol mass concentration during speaking, 0·40µg/m^-3, was greater than during vigorous exercise (0·17µg/m^-3,p&lt;0·001), but not different to high intensity exercise (0·42µg/m^-3,p=0·083). Rest and exercise demonstrated similar aerosol size distributions, however speaking emitted an additional, larger mode at 2–3µm. Mean minute ventilation was 11L/min, 15L/min, 63L/min and 114L/min at rest, speaking, vigorous exercise and high intensity exercise, respectively. Median mass emission rate (aerosol mass concentration normalised for ventilation) produced by speaking, 0·092ng/s^-1, was not different to vigorous exercise, 0·207ng/s^-1, (p=0·726) but was lower than high intensity exercise 0·682ng/s^-1, p&lt;0.001). <h3>Interpretation</h3> The size distribution of airborne particles emitted during exercise, match that of breathing at rest, with increased minute ventilation a primary driver of the increased aerosol mass emissions that occur during exertion. Aerosol mass emission rates during vigorous exercise are not different to speaking at a conversational, to loud conversational volume. These findings enhance our understanding of particle release during the fundamental physiological process of exercise, enabling appropriate mitigations for airborne pathogens, including SARS-CoV-2. <h3>Funding</h3> The PERFORM 2 study was funding by EPSRC.