USE OF VIRAL FILTER TO REDUCE EXPOSURE TO EXHALED AEROSOL DOES NOT AFFECT METHACHOLINE DOSE DELIVERY DURING BRONCHOPROVOCATION TESTING

TOPIC: Respiratory Care TYPE: Original Investigations PURPOSE: Methacholine challenge testing (MCT) is a common bronchoprovocation technique used to assess airway hyperresponsiveness. Current ERS guidelines recommend that measures should be taken to minimize technician exposure to methacholine aerosol, with added infection control concerns in the context of the ongoing COVID-19 pandemic. We previously demonstrated that the addition of a viral filter to the nebulizer exhalation limb reduced expelled particle concentrations by 77-91% during MCT. Our aim was to evaluate whether this modification resulted in a change in the delivered dose of methacholine. METHODS: Following published industry testing standards for MCT, we connected a Hamilton-G5 mechanical ventilator and Michigan lung simulator in series with respiratory rate 15 breaths/min, tidal volume (VT) 500 mL, I:E ratio 1:1 with a sinusoidal waveform. We compared methacholine dose delivery using the Hudson MicroMist and AeroEclipse II BAN nebulizers powered by either a dry gas source at 50 psi and 4.5 L/min or the Ombra compressor system, in addition to our current MCT protocol which utilizes Hudson MicroMist nebulizer with KoKo dosimeter (3 breaths). A filter placed in line between the nebulizer and test lung was weighed before and after 1 minute of nebulized methacholine delivery. Mean inhaled mass was calculated from three trials of each method with and without a viral filter on the exhalation limb. Dose delivery was calculated by multiplying the mean inhaled mass by the respirable fraction (particles < 5 µm) and inhalation time. Unpaired t-test was used to compare methacholine dose delivery with and without viral filter placement. Due to multiple independent comparisons, Bonferroni correction was used and alpha level was set at 0.01. RESULTS: The addition of a viral filter did not significantly affect methacholine dose delivery across all devices tested. Using the 50 psi dry gas source, dose delivered with the Hudson MicroMist did not differ with (461.0 µg) or without (307.8 µg) a viral filter (P=0.11) or with the AeroEclipse II BAN with (580.8 µg) or without (678.4) a viral filter (P=0.59). Using the Ombra compressor, dose delivered with the Hudson MicroMist did not differ with (1063.3 µg) or without (947.5 µg) a viral filter (P=0.026) or with AeroEclipse II BAN with (843.8 µg) or without (648.3) viral filter (P=0.42). Dose delivery did not differ significantly when using the KoKo dosimeter and Hudson MicroMist with or without a viral filter (P=0.20) using a 3-breath protocol. CONCLUSIONS: The addition of a viral filter to the nebulizer expiratory limb did not result in a significant change in the in the delivered dose of methacholine. CLINICAL IMPLICATIONS: Based on these findings, use of a viral filter to limit the concentration of expelled aerosol during MCT should be considered to improve pulmonary function technician safety and potentially reduce the risk of infectious exposure during the ongoing COVID-19 pandemic. DISCLOSURES: No relevant relationships by Kaiser Lim, source=Web Response no disclosure submitted for todd meyer;No relevant relationships by Alexander Niven, source=Web Response No relevant relationships by Paul Scanlon, source=Web Response No relevant relationships by Yosuf Subat, source=Web Response No relevant relationships by Keith Torgerud, source=Web Response

Aerosol Generation during Peak Flow Testing: Clinical Implications during the COVID-19 Pandemic

Background: Peak flow testing is a common procedure performed in ambulatory care. There are currently no data regarding aerosol generation during this procedure. We measured small particle concentrations generated during peak flow testing. Several peak flow devices were compared to assess for differences in aerosol generation. The amount of aerosol generation should objectively inform infection control and mitigation strategies during the COVID-19 pandemic. Methods: Five healthy volunteers performed peak flow maneuvers in a particle free laboratory space. Two devices continuously sampled the ambient air during the procedure. One device can detect ultrafine particles from 0.02 - 1 micron, while the second device can detect particles of size 0.3, 0.5, 1.0, 2.0, 5.0, and 10 microns. Five different peak flow meters were compared to ambient baseline during masked and unmasked tidal breathing. Results: Ultrafine particles (0.02 - 1 micron) were generated during peak flow rate measurement. Ultrafine particle mean concentration was lowest with Respironics peak flow meter (1.25±0.47 particles/cc) and similar between Philips (3.06±1.22), Clement Clarke (3.55±1.22 particles/cc), Respironics low range (3.50±1.52 particles/cc), and Monaghan (3.78±1.31 particles/cc) peak flow meters. Although ultrafine particle mean concentration increased during peak flow measurements compared ambient baseline during masked (0.22±0.29 particles/cc) and unmasked (0.15±0.18 particles/cc) tidal breathing, these differences were small and remained well below ambient PFT room particle concentrations (89.9±8.95 particles/cc). Conclusions: In this study, we were able to establish the feasibility of measuring small particle production after peak flow testing. Our study shows that ultrafine particles are generated during peak flow measurement. Although all peak flow meters demonstrated increased mean particle concentration, differences were small compared to the mean particle concentrations found in the ambient clinical environment. Outpatient practices should be aware of the potential risk of these findings and take appropriate infection control precautions.