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Concerns have been ramping up with regard to the propagation of infectious droplets due to the recent COVID-19 pandemic. The effects of filter microstructures and ambient air flows on droplet dispersion by sneezing are investigated by a fully coupled Eulerian-Lagrangian computational modeling with a micro-to-macroscale bridging approach. Materials that are commonly applied to face masks are modeled to generate two different virtual masks with various levels of filtration efficiency, and the leakage percentages through the unsealed nose and cheek areas were set to 11% and 25%, respectively. The droplet propagation distance was simulated with and without mask wearing in still and windy conditions involving head wind, tail wind, and side wind. The results demonstrate that wearing a face mask reduces the transmittance distance of droplets by about 90%-95% depending on the mask type; nonetheless, the droplets can be transmitted to distances of 20-25 cm in the forward direction even with mask-wearing. Thus, a social distance of at least 20 cm between people would help to prevent them from becoming exposed to ejected droplets. This study is significant in that important aspects of mask materials, in this case the porous microstructure-dependent filtration efficiency and permeability under varied ambient flow conditions, were considered for the first time in an evaluation of the barrier performance against droplet transmittance through a multiphase computational fluid dynamics simulation of air-droplet interaction and turbulence flow dynamics.
RESUMO
BACKGROUND: The symptom severity of back pain/leg pain is not correlated with the severity of degenerative changes and canal stenosis in lumbar stenosis. Considering the individual pain sensitivity might play an important role in pain perception, this discordance between the radiologic findings and clinical symptoms in degenerative lumbar stenosis might originate from the individual difference of pain sensitivity for back pain and/or leg pain. OBJECTIVE: To determine the relationship among the clinical symptoms, radiologic findings, and the individual pain sensitivity in the patients with degenerative lumbar spinal stenosis. STUDY DESIGN: Retrospective analysis of prospectively collected data. SETTING: A spine center in the department of orthopedic surgery. METHODS: In 94 patients who had chronic back pain and/or leg pain caused by degenerative lumbar spinal stenosis, a medical history, a physical examination, and completion of a series of questionnaires, including pain sensitivity questionnaire (PSQ) [total PSQ and PSQ-minor], Oswestry Disability Index (ODI), Visual Analog Pain Scale (VAS) for back pain, and Short Form-36 (SF-36) were recorded on the first visit. Radiologic analysis was performed using the MRI findings. The grading of canal stenosis was based on the method by Schizas, and the degree of disc degeneration was graded from T2-weighted images with the Pfirrmann classification. The correlations among variables were statistically analyzed. RESULTS: Total PSQ and PSQ-minor were not dependent on the grade of canal stenosis after gender adjustment. VAS for leg pain and back pain was highly associated with the total PSQ and the PSQ-minor. Total PSQ and PSQ-minor were also significantly associated with ODI. Among SF-36 scales, the PSQ minor had significant correlations with SF-36 such as bodily pain (BP), Role-emotional (RE), and Mental Component Summary (MCS) after control of confounding variables such as body mass index (BMI), age, and the grade of canal stenosis/disc degeneration. Total PSQ was significantly associated with the SF-36 RP, BP, and RE. Furthermore, after adjustment for gender and pain sensitivity, there was no significant association between the grade of canal stenosis and VAS for back pain/leg pain and ODI, and no correlation was found between the grade of disc degeneration and VAS for back pain/leg pain and ODI, either. LIMITATIONS: The multiple lesions of canal stenosis and/or disc degeneration and the grade of facet degeneration were not considered as a variable. CONCLUSION: The current study suggests that the pain sensitivity could be a determining factor for symptom severity in the degenerative spinal disease.
