10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Exposure of Home Healthcare Workers to Aerosolized Medications: Two-Phase Simulation Study
SERGEY A. GRINSHPUN, Yousef Elmashae, Katie Ollier, Maija Leppänen, Michael Yermakov, Tiina Reponen, University of Cincinnati
Abstract Number: 178 Working Group: Workplace Aerosol
Abstract Home healthcare is one of the most rapidly growing professions worldwide. Home-attending healthcare professionals are exposed to various aerosol contaminants, including pharmaceuticals administered in patients’ homes. One common procedure is a nebulizer treatment. Environmental conditions in homes are different from hospital environments, which should affect the aerosol concentration levels and exposure patterns. This two-phase pilot simulation study addressed the inhalation exposure of home healthcare workers to nebulized medications. The objective was to measure particles aerosolized from a commercially available nebulizer-based aerosol delivery system applied to a breathing manikin under different environmental conditions and at different proximity to the aerosol source.
The first phase of this investigation was conducted with aerosolized medications, namely Ipratropium Bromide, Budesonide, and Albuterol Sulfate (all suspended in a NaCl solution), as well as with pure NaCl (also used as medication to treat respiratory symptoms). Deionized water was used as a control. The nebulizer was applied to a manikin connected to a constant push air flow simulating an exhalation-only breathing regime. It maximizes the aerosol output and represents a “worst-case scenario” as compared to a conventional inhalation-exhalation cycle. The other manikin, which simulated a healthcare worker, was placed at different distances from the patient-simulating manikin. The aerosols were measured using an Electrical Low Pressure Impactor (Dekati Ltd). Exposure to all four selected aerosolized medications exceeded background control by one to four orders of magnitude. The particle size distributions measured for the four aerosols at a fixed distance from the source demonstrated similar trends. Although the total aerosol mass concentration in the breathing zone of the healthcare worker-simulating manikin ranged widely, from 0.229 to 1.02 g/m3, it was not significantly affected by the medication type. We concluded that NaCl can serve as a surrogate for assessing aerosol exposures, at least for the selected nebulizer-administered medications.
The second phase of the study was conducted in a room-size exposure chamber with a breathing manikin simulating a patient. However, instead of applying a constant flow, the manikin was connected to a breathing simulator, producing a cyclic pattern with the mean inspiratory flow rate of 15 L/min. More importantly, instead of using the second manikin representing a healthcare worker, the tests were conducted with an actual human subject whose inhalation point (nose/mouth) located at different distances from the aerosol source: 6ʺ, 12ʺ, 24ʺ, and 48ʺ. The total aerosol concentration was measured at these distances using a P-Trak condensation particle counter (TSI Inc.). Based on the findings of the first phase of this study, NaCl was utilized as a medication surrogate. The tests were performed at different air exchange rates in the chamber: 0 (calm air), 5 AEH (a higher end for residential environments), and 17 AEH (extremely high, typically used in stationary healthcare settings). It was concluded that the aerosol concentration (and, therefore, the inhalation exposure) decreases as the worker’s proximity to the patient increases. Although statistically significant, this effect was relatively weak: the drop ranged from 1.5- to 2.5-fold when the distance changed from 6ʺ (extremely close proximity) to as far as 48ʺ. The air exchange effect was significant between 0 and 5 AEH (typical ventilation rates in homes) with an the average difference of 3-fold; however, it essentially diminished between 5 and 17 AEH.
In summary, the inhalation exposure of home healthcare workers to particles aerosolized by medical nebulizers is significant. The proximity and ventilation affect the exposure; however, these factors are not sufficiently powerful to effectively reduce it.
The study was supported by the National Institute for Occupational Safety and Health through the Targeted Research Training Program of the University of Cincinnati Education and Research Center.