Observation and quantification of respiratory droplets by laser light scattering

National Institute Of Diabetes And Digestive And Kidney Diseases

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Abstract

Migration to the lungs of an initial upper airway infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or other respiratory pathogens can lead to pneumonia, associated with progression from mild to severe symptoms. Whereas chemical pneumonitis or bacterial pneumonia may be caused by the macroaspiration of large volumes of oropharyngeal or gastroesophageal secretions into the lower respiratory tract, microaspiration, i.e., a similar mechanism but involving much smaller amounts of oropharyngeal secretions, is considered the pathogenetic mechanism for most pneumonias, including that associated with COVID-19. We investigate an alternative mechanism: Rather than by microaspiration, these fluids enter the lungs as aerosolized microdroplets that are generated by snoring and then carried by the inspired airstream. Laboratory measurements indicate that snoring generates (a) comparable numbers and sizes of oral fluid droplets as loud speaking and (b) total fluid quantities that are similar to those reported for microaspiration. Snoring propensity is strongly correlated to known risk factors for severe COVID-19, including male gender, age, obesity, diabetes, obstructive sleep apnea, and pregnancy. Our laboratory measurements of voluntary snoring-generated aerosols suggest that snoring may be the true physical mechanism behind the postulated microaspiration phenomenon. Research is focused on study of the transfer of chemical tracers from the oral cavity into the lung, with the analysis focused on the quantitative analysis of tracers in breath-generated aerosol by both NMR spectroscopy, mass spectrometry, and quantitative PCR.