ABSTRACT
Objective To study mechanical properties of the anisotropy for pig trachea and main bronchi, and determine the constitutive model of trachea deformation by finite element numerical simulation. Methods The pig tracheas were collected and cut through in their axial directions and expanded into two-dimensional planes. Then, by setting the length direction of the trachea aortas as 0°, each planar trachea was anticlockwisely cut into 6 samples with orientation of 30°,60°,90°,120°,150° and 180°, respectively. Uniaxial tensile tests were applied on the specimen in 6 angular directions by using the electronic universal test machine, to obtain stress and strain of the specimen in different directions. Nonlinear fitting to the experimental data was performed by using the Mooney-Rivilin hyperelastic model, in order to obtain the material characteristic parameters. Finite element models of the trachea and the main bronchi were established, and tensile numerical simulation was carried out.Results Samples at different angles showed different stress-strain curves. In the trachea, the stresses of samples with angle of 30°, 120° and 150° were in the range of 1.0-1.5 MPa, the stresses of samples with angle of 60° and 90° were in the range of 0.5-1.0 MPa, and the stresses of samples with angle of 180° were in the range of 2.5-3.0 MPa. In the main bronchi, the stresses of samples with angle of 30°, 120° and 150° were in the range of 0.8-1.0 MPa, the stresses of samples with angle of 90° and 180° were in the range of 1.4-1.8 MPa, and the stresses of samples with angle of 120° were in the range of 0.4-0.6 MPa. There was an obvious difference between the trachea and the main bronchi. The finite element simulation verified that the Mooney-Rivilin constitutive model was suitable for describing small deformation behavior of the trachea. Conclusions The pig trachea exhibits strong anisotropy. Meanwhile, the Mooney-Rivilin model can characterize small tracheal deformations. The results provide theoretical references for tracheal resection and reconstruction in clinical treatment and intervention with surgical instruments such as bronchoscopy.
ABSTRACT
Objective:To analyze the patterns of antibacterial agents in Chinese children surveyed by the China multi-center monitoring network for the application of antibacterial agents in children and neonates in 2019 by using World Health Organization (WHO) Access, Watch, Reserve and Not-recommended (AWaRe) and typical anatomical/therapeutic/chemical (ATC) in this study.Methods:The cross-sectional method was adopted.A multi-center cross-sectional survey was conducted on one day from September to December 2019.The information of all inpatients taking antibiotics was uploaded to the network-based data collection system (https: //garpec-31.mobilemd.cn/login.aspx? relogin=true). This study covered 13 hospitals from 10 provinces and cities in China.All hospitalized children in the Respiratory Department, Infectious Disease Department, General Surgery Department, Pediatric Intensive Care Units, Neonatal Intensive Care Units and Neonatology joined in this survey.The clinically used antibacterial agents were classified by AWaRe and ATC, and the AWaRe and ATC distributions of antibacterial agents prescribed for Chinese children and neonates were described.Results:Of the 2 644 antibiotic prescriptions included from 13 hospitals, 2 134 (80.71%) were for children and 510 (19.29%) were for neonates.Of all antibiotic prescriptions, there were 368 (13.92%) Access antibiotics prescriptions, 1 973 (74.62%) Watch prescriptions, 60 (2.27%) Reserve prescriptions and 243 (9.19%) Not-recommended prescriptions.The top-five antibiotics prescribed for children and neonates were third-generation cephalosporins (1 056, 39.94%), macrolides (492, 18.61%), carbapenems (275, 10.40%), beta lactam-beta lactamase inhibitors (246, 9.30%), and second-generation cephalosporins (136, 5.14%). The use ratios of Access, Watch, Reserve and Not-recommended antibiotics in each center ranged from 0 to 30.00%, 36.67% to 97.20%, 0 to 17.02% and 0 to 33.33%, respectively.In 1 360 antibiotic prescriptions for children and neonates with pneumonia, there were 152 (11.18%) Access antibiotics, 1 051 (77.28%) Watch antibiotics, 37 (2.72%) Reserve antibiotics, and 120 (8.82%) Not-recommended antibiotics.The top-five antibiotics prescribed for children with pneumonia were third-generation cephalosporins (522, 38.38%), macrolides (388, 28.53%), beta lactam-beta lactamase inhibitors (141, 10.37%), carbapenems (117, 8.6%) and penicillins (49, 3.60%).Conclusions:Watch antibiotics and broad spectrum antibiotics such as third-generation cephalosporins and macrolides prone to induce resistance are the main antibacterial agents used in Chinese children and neonates with pneumonia.Broad-spectrum antibiotics may be overused in Chinese children and neonates.