Assessing inhalation exposure to infectious particles in hospitals using a breathing thermal manikin
Hospitals serve as professional institutions for diagnosing,treating,preventing,and controlling infectious diseases,marked by high population density,a significant influx of individuals,and many pathogenic microorganisms.These factors make hospitals prime locations for the transmission of infectious diseases.In previous outbreaks of respiratory infections,clusters of infections in large hospitals are not uncommon.In addition,many diagnostic and therapeutic procedures in hospitals must be performed by doctors or nurses using hand-held instruments,which reduces the linear distance between the doctor's face and the patient's face.Inhaling infectious particles in hospitals is the most direct route of exposure to respiratory infections.Accurately measuring respiratory exposure doses is a crucial indicator for assessing the human infection risk.Breathing thermal manikins,simulating the human microenvironment,and accounting for human-environment interactions are powerful tools for studying infectious particles inhalation exposure.To overcome the inadequacies of biomimicry in existing breathing thermal manikins,this study develops an advanced breathing thermal manikin system that incorporates human morphological features,heat dissipation simulation,respiratory activity,and respiratory tract geometry.The system performs three fundamental functions:Simulating the human thermal plume,simulating human breathing,and respiratory tract bionic.It serves as a platform for directly measuring exposure doses in the respiratory tract.The reliability of the breathing thermal manikin in simulating the human microenvironment was assessed by measuring surface temperature and respiratory parameters.The results indicated that,within 57.6 min,the manikin's surface temperature could stabilize between 28.9-30.9℃,while respiratory flow varied with time close to the sinusoidal fluctuating respiratory boundary.Moreover,the system can adjust respiratory minute ventilation(RMV)and breathing frequency(BF)at various metabolic rates,with regulation ranges of 6-20 L/min and 10-20 min-1 for RMV and BF,respectively.We conducted a proximity infectious particles exposure experiment based on a breathing thermal manikin system under displacement ventilation conditions,and the particles source was positioned at a 1.5 m height with 0.63 μm particle size.Our objectives were to assess the impact of human thermal plumes on particles concentration in the breathing zone and quantify correlations among environmental,breathing zone,and respiratory tract particle concentration.The findings reveal a roughly 23％reduction in particle concentration within the breathing zone when considering the thermal plume.Additionally,concentrations in the breathing zone and respiratory tract at G0 and G4 levels are approximately 4.0,2.7,and 2.0 times higher than the environmental concentrations.Discrepancies in concentration highlight that although a relationship exists between the environment concentration and the concentration in the breathing zone and respiratory tract,these values do not accurately reflect respiratory exposure,let alone enable a direct assessment of the human infection risk.In this study,we developed a breathing thermal manikin system as an innovative approach to measuring respiratory exposure dose.It efficiently addresses ethical and subject safety concerns,ensures excellent experimental repeatability,shortens the experimental cycle,reduces the experiments costs,and provides a more advanced and reliable measurement instrument for studying infectious particle inhalation exposure within hospital environments.This advancement lays the groundwork for quantifying the link between personnel infection risk and respiratory exposure,formulating evaluation criteria that authentically reflect infection risk among hospital staff.
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