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Background: During anaesthetic induction with a facemask, the inconsistent inspiratory flow with manual ventilation (MV) raises the peak airway pressure (PAP), which can be significantly higher than PAP during pressure-controlled ventilation (PCV). In this study, PAP was compared between MV and PCV at the same tidal volume of 8-10 ml/kg during facemask ventilation for anaesthetic induction in children. The occurrence of gastric insufflation (GI) was evaluated with ultrasonography and stethoscopic auscultation.Methods: Forty-eight children, aged 0.5-7 years, undergoing elective urologic surgery were randomly allocated into either Group MV or Group PCV. Under light sedation with thiopental iv., ultrasonography (US) was performed and the gastric antrum was identified. After additional thiopental and rocuronium administration, facemask ventilation with a tidal volume of 8-10 ml/kg was performed for 3 min, whereas respiratory parameters were recorded at 1 min intervals. Real-time US and stethoscopic auscultation were performed for evaluation of GI.Results: In the MV group, PAP was higher at all the time points compared with the PCV group (14 vs. 9.5, 15 vs. 10 and 15 vs. 9 cmH2 O, all P < 0.05). However, there was no difference in the GI occurrence between Group MV and Group PCV (7 vs. 3, P = 0.284). There was no difference between PAP in patients with GI and without GI (P > 0.05). Ultrasonography was more sensitive in detecting GI than the stethoscopic auscultation (10 vs. 5). Gastric antral area was expanded after facemask ventilation in both groups, but there were no intergroup differences.Conclusion: Although PCV provided lower PAP than MV at the same tidal volume, the risk of GI may not be eliminated during facemask ventilation in paralysed small children. [ABSTRACT FROM AUTHOR]

Face-centred cubic Cr-rich carbide is known to precipitate in a face-centred cubic matrix with a cube-cube orientation relationship, thereby minimizing the elastic strain energy. In the present study, for the first time, the precipitation was observed of an abnormal Cr-rich carbide, which did not have the cube-cube orientation relationship in its face-centred cubic matrix. The abnormally oriented carbides nucleated and grew around random grain boundaries, and were observed to have a lamellar or plate-like morphology. The crystallographic orientation anomaly was characterized by measuring the tilt angles of the three crystal poles of the matrices, carbides and adjacent grains, using a transmission electron microscope to find the closest coincidence site lattice boundary. The carbides showed a slight deviation from a cube-cube orientation with adjacent grains and did not present any particular orientational relationship with the matrix. The deviation angles from coincidence site lattice boundaries between the matrices and carbides were smaller than those between matrices and adjacent grains. The abnormally oriented carbides appeared to nucleate on adjacent grains, and underwent a rotation within the matrix during the initial stage of growth to release the phase boundary energy between the carbides and the matrix. [ABSTRACT FROM AUTHOR]

The article describes a technique for the characterization of parameters relating adjacent grains using transmission electron microscopy (TEM). The technique utilizes the orthogonal relationship between the tilt axes used in TEM and the axes of the cubic crystal, which was established using the triangulation method. The evaluation of the measurement errors from the tilt angles of the zone axes is also discussed.