Fig. 1

Schematic diagram of two methods with or without neck extension for tube advancement from the nasal cavity into the oropharynx. a depicts advancement of a preformed nasal RAE tube with neck extension. With neck extension, the angle between the axis of the distal part of the tube and the posterior wall of the nasopharynx could be obtuse, and the wrinkled soft tissue might be spread, such as a change from dotted lines to solid lines. Based on our results, we hypothesized that these possible changes might aid smooth advancement of the tube. However, these hypotheses were not investigated in the study. b depicts advancement of a preformed nasal RAE tube without neck extension (neutral head position). Although not presented in the results, the angle between the nasal floor and the posterior wall of the nasopharynx, without neck extension, was measured as about 100 degrees in the sagittal view of maxillofacial computed tomography of 39 among the study subjects. Also, we observed the angle became widen with neck extension in 3 patients who were preoperatively examined about cervical spine mobility, when we reviewed radiologic findings of cervical spine series of flexion/neutral/extension postures. RAE indicates Ring-Adair-Elwyn