Mitigation of Aerosols Generated during Exercise Testing with a Portable High-Efficiency Particulate Air (HEPA) Filter with Fume Hood
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 6 healthy volunteers aged 20-56 years. In the first experiment, exercise was performed in a small tent with controlled airflow using stationary cycle, portable HEPA filter with fume hood, and particle counter to document aerosol concentration. Subjects performed a 4-stage maximal exercise test lasting 12 minutes plus 5 minutes pre-test quiet breathing and 3 minutes 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 1722±1484/L vs. 96±124/L (P<.04) for all particles (> 0.3µm), 1339±1281/L vs. 76±104/L (P<.05) for smaller particles (0.3-1.0µm), and 333±209/L vs. 17±19/L (P<.01) for larger particles (1.0-5.0µm) at the end of the protocol comparing mitigation vs. portable HEPA filter. Use of portable HEPA filter in a clinical exercise laboratory clearance experiment reduced aerosol clearance time 47% versus HVAC alone. INTERPRETATION: 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 might therefore be useful in clinical exercise testing laboratories to reduce the risk of COVID-19 transmission.