Search

Abstract Pulmonary hypertension is associated with significant risk of perioperative life-threatening events. We present a case of a 12-year-old child with severe pulmonary arterial hypertension who successfully underwent diagnostic cardiac catheterization under ketamine and dexmedetomidine sedation with the support of high-flow nasal oxygen. Ketamine and dexmedetomidine are reported to have minimal effect on pulmonary vasculature in children with pulmonary hypertension and can be safely used in this population along with its lack of respiratory depression. Positive pressure generated by high-flow nasal oxygen improves upper airway patency, prevents micro-atelectasis, and is shown to improve the effectiveness of ventilation and oxygenation in patients under sedation breathing spontaneously. The presented strategy may contribute to enhancing the safety and effectiveness of procedural sedation for children with life-threatening pulmonary hypertension.

In this paper, the large deflection response of a circular mesh tube under pure bending was investigated by using FE analysis. In the previous study[Nakamura, T., Ushijima, K., Evaluation of large deflection response of circular mesh tubes, Transaction of the JSME (in Japanese), Vol. 88, No. 915 (2022)], the effect of the ovalization across the cross-section on the bending response was neglected, but in this study, the influence of cross-sectional flattening on the nonlinear bending moment versus curvature was taken into consideration. There are three reasons for arising the maximum bending moment, but in this paper, we mainly focused on the two mechanisms (the large flattening response in elastic deformation and the plastic yielding behaviour) to the maximum bending moment. Based on our FE analysis, we proposed theoretical equations for predicting the maximum bending moment as a function of tube geometries and material parameters such as Poisson’s ratio and the plastic yielding stress.

Abstract Background During pandemic situations, many guidelines recommend that surgical masks be worn by both healthcare professionals and infected patients in healthcare settings. The purpose of this study was to clarify the levels and changes of oxygen concentration over time while oxygen was administered over a surgical mask. Methods Patients scheduled to undergo general anesthesia (n = 99) were enrolled in this study. First, patients were administered oxygen at 6 L/min via an oxygen mask over a surgical mask for 5 min. The patients removed the surgical mask and then took a 3-min break; thereafter, the same amount of oxygen was administered for another 5 min via the oxygen mask. We measured the fraction of inspired oxygen (FiO2), the end-tidal CO2 (EtCO2), and respiratory frequency every minute for 5 min, both while administering oxygen with and without a surgical mask. The FiO2 was measured at the beginning of inspiration and the EtCO2 was measured at the end of expiration. Results The FiO2 at 5 min was significantly lower when breathing with a surgical mask than that without it (mean difference: 0.08 [95% CI: 0.067–0.10]; p

In this paper, the large deflection of a circular mesh tube was investigated by using a finite element method. During this investigation, it is assumed that the tube is deformed elastically, and its structural nonlinearity due to large deflection was considered. In addition, a theoretical model of an arc-shaped beam is proposed in order to predict the equivalent stiffness. The equivalent stiffness can be used to estimate the nonlinear large deflection response of the tube. In particular, the effects of the number of spirals and the number of turns on the prediction accuracy was discussed.