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

Tomisa, Gábor; Horváth, Alpár; Farkas, Árpád; Nagy, Attila; Kis, Erika; Tamási, Lilla

INTRODUCTION: There are concerns about pulmonary function tests (PFT) being associated with aerosol generation and enhanced virus transmission. As a consequence, the number of PFTs was significantly reduced during the COVID-19 pandemic. However, there are no robust data supporting this fear. OBJECTIVES: The aim of this work was to perform real-life measurement of aerosol concentration in a PFT laboratory to monitor the concentration of particles near the patient and to model the associated potential viral load. METHODS: Two optical particle counters (OPC) were used to sample the background concentration and the concentration of particles in the vicinity of the mouth of the patients in the whole-body plethysmography box. A statistical evaluation of the measured particle concentration time series was completed. The particle exhalation rate was assessed based on the measured particle concentration data by applying the near-field/far-field theory. The number of exhaled viruses by an infected patient during the test was assessed in comparison with the emission of viruses during quiet breathing and speaking. RESULTS: Twenty-five patients were involved in the study. Eighteen patients produced a significant increase of the aerosol concentration, which was 1910±593 particles/L. Submicron particles dominated the number size distribution of the generated particles, but large particles represented a higher volume fraction in the generated particles compared to the background. An average gene exhalation rate of 0.2/min was estimated from this data. This is one order of magnitude higher than the release rate of the same infected person during quiet breathing and of the same order of magnitude with the release rate during normal speaking. CONCLUSIONS: Present results demonstrated that PFT is an aerosol generating procedure. Based on current results, the moderate increase of viral load does not underpin the stopping of such examinations.