Effects of Pulmonary Fibrosis and Surface Tension on Alveolar Sac Mechanics in Diffuse Alveolar Damage.

Diffuse alveolar damage (DAD) is a characteristic histopathologic pattern in most cases of acute respiratory distress syndrome and severe viral pneumonia, such as COVID-19. DAD is characterized by an acute phase with edema, hyaline membranes, and inflammation followed by an organizing phase with pulmonary fibrosis and hyperplasia. The degree of pulmonary fibrosis and surface tension is different in the pathological stages of DAD. The effects of pulmonary fibrosis and surface tension on alveolar sac mechanics in DAD are investigated by using the fluid-structure interaction (FSI) method. The human pulmonary alveolus is idealized by a three-dimensional honeycomb-like geometry, with alveolar geometries approximated as closely packed 14-sided polygons. A dynamic compression-relaxation model for surface tension effects is adopted. Compared to a healthy model, DAD models are created by increasing the tissue thickness and decreasing the concentration of the surfactant. The FSI results show that pulmonary fibrosis is more influential than the surface tension on flow rate, volume, P-V loop, and resistance. The lungs of the disease models become stiffer than those of the healthy models. According to the P-V loop results, the surface tension plays a more important role in hysteresis than the material nonlinearity of the lung tissue. Our study demonstrates the differences in air flow and lung function on the alveolar sacs between the healthy and DAD models.

Estimation of the Outbreak Severity and Evaluation of Epidemic Prevention Ability of COVID-19 by Province in China.

Objectives. To compare the epidemic prevention ability of COVID-19 of each province in China and to evaluate the existing prevention and control capacity of each province.Methods. We established a quasi-Poisson linear mixed-effects model using the case data in cities outside Wuhan in Hubei Province, China. We adapted this model to estimate the number of potential cases in Wuhan and obtained epidemiological parameters. We estimated the initial number of cases in each province by using passenger flowrate data and constructed the extended susceptible-exposed-infectious-recovered model to predict the future disease transmission trends.Results. The estimated potential cases in Wuhan were about 3 times the reported cases. The basic reproductive number was 3.30 during the initial outbreak. Provinces with more estimated imported cases than reported cases were those in the surrounding provinces of Hubei, including Henan and Shaanxi. The regions where the number of reported cases was closer to the predicted value were most the developed areas, including Beijing and Shanghai.Conclusions. The number of confirmed cases in Wuhan was underestimated in the initial period of the outbreak. Provincial surveillance and emergency response capabilities vary across the country.

Estimation of the Outbreak Severity and Evaluation of Epidemic Prevention Ability of COVID-19 by Province in China

Objectives. To compare the epidemic prevention ability of COVID-19 of each province in China and to evaluate the existing prevention and control capacity of each province. Methods. We established a quasi-Poisson linear mixed-effects model using the case data in cities outside Wuhan in Hubei Province, China. We adapted this model to estimate the number of potential cases in Wuhan and obtained epidemiological parameters. We estimated the initial number of cases in each province by using passenger flowrate data and constructed the extended susceptible-exposed-infectious-recovered model to predict the future disease transmission trends. Results. The estimated potential cases in Wuhan were about 3 times the reported cases. The basic reproductive number was 3.30 during the initial outbreak. Provinces with more estimated imported cases than reported cases were those in the ing provinces Hubei, including Henan and Shaanxi. The regions where the number of reported cases was closer to the predicted value were most the developed areas, including Beijing and Shanghai. Conclusions. The number of confirmed cases in Wuhan was underestimated in the initial period of the outbreak. Provincial surveillance and emergency response capabilities vary across the country. (Am J Public Health. 2020;110:1837-1843. https:// doi.org/10.2105/AJPH.2020.305893)