Mitigation of Aerosols Generated During Exercise Testing With a Portable High-Efficiency Particulate Air Filter With Fume Hood

Abstract

Background The role of portable high-efficiency particulate air (HEPA) filters for supplemental aerosol mitigation during exercise testing is unknown and might be relevant during COVID-19 pandemic. Research Question What is the effect of portable HEPA filtering on aerosol concentration during exercise testing and its efficiency in reducing room clearance time in a clinical exercise testing laboratory? Study Design and Methods Subjects were six healthy volunteers aged 20 to 56 years. In the first experiment, exercise was performed in a small tent with controlled airflow with the use of a stationary cycle, portable HEPA filter with fume hood, and particle counter to document aerosol concentration. Subjects performed a four-stage maximal exercise test that lasted 12 min plus 5 min of pretest quiet breathing and 3 min of active recovery. First, they exercised without mitigation then with portable HEPA filter running. In a separate experiment, room aerosol clearance time was measured in a clinical exercise testing laboratory by filling it with artificially generated aerosols and measuring time to 99.9% aerosol clearance with heating, ventilation, and air conditioning (HVAC) only or HVAC plus portable HEPA filter running. Results In the exercise experiment, particle concentrations reached 1,722 ± 1,484/L vs 96 ± 124/L ( P < .04) for all particles (>0.3 μm), 1,339 ± 1,281/L vs 76 ± 104/L ( P < .05) for smaller particles (0.3 to 1.0 μm), and 333 ± 209/L vs 17 ± 19/L ( P < .01) for larger particles (1.0 to 5.0 μm) at the end of the protocol in a comparison of mitigation vs portable HEPA filter. Use of a portable HEPA filter in a clinical exercise laboratory clearance experiment reduced aerosol clearance time 47% vs HVAC alone. Interpretation The portable HEPA filter reduced the concentration of aerosols generated during exercise testing by 96% ± 2% for all particle sizes and reduced aerosol room clearance time in clinical exercise testing laboratories. Portable HEPA filters therefore might be useful in clinical exercise testing laboratories to reduce the risk of COVID-19 transmission.

Aerosol particle emission increases exponentially above moderate exercise intensity resulting in superemission during maximal exercise

“…To be able to do this, we needed to developed an experimental set up that detects the concentration of particles in a partial flow of exhaled air without correction ( 24 – 26 ) that reduces the errors that can be caused by uncontrolled inflow of particle-free air ( 13 , 14 , 27 , 28 ). By measuring aerosol particle concentration and ventilation in one individual, we were able to calculate aerosol particle emission that is a more direct measure of the risk of pathogen transmission by aerosol particles by one individual than the aerosol particle concentration in exhaled air or in room air ( 16 – 19 , 25 ).…”

“…( 30 ) proposed that the majority of outbreaks were caused by the combination of one superspreader in a small room with poor ventilation, we recommend additional measures to reduce the risk of infection during indoor group exercise above 2 W/kg when superemission occurs. This could include 15-min airing breaks in between classes, pre-exercise infection testing of participants, safety shields in between exercisers, mobile air filters ( 19 , 31 ), and the wearing of masks even during exercise ( 26 , 32 – 34 ).…”

“…These individuals have been termed “superemitters” ( 13 ). The number of aerosol particles emitted by a person per unit of time varies and increases when that person talks, coughs, sings ( 14 , 15 ), or is physically active ( 16 – 20 ). It has also been shown that the number of emitted aerosol particles is influenced by the airway hydration status ( 20 , 21 ).…”

“…Current research on airborne pathogen transmission is limited by the fact that most studies only report the concentration of aerosol particles in expired air ( 13 , 14 , 18 , 20 , 24 – 26 ) or in a room ( 16 – 19 , 23 ) but not the emission of aerosol particles by one individual. Since the latter is required for assessing the risk of infection, we developed a method to measure both the concentration and emission of aerosol particles from rest up to maximal exercise.…”

New Insights into the Prevention of Hospital-Acquired Pneumonia/Ventilator-Associated Pneumonia Caused by Viruses

“…An increasing amount of data suggests that portable HEPA filters and ultraviolet light may also be effective methods to decrease the concentration of respiratory aerosols and viruses in clinical spaces and thus a potential mitigation option for underventilated spaces. [99][100][101][102][103]…”