The anatomical shape of the airway during endotracheal intubation.

The shape of the airway during endotracheal intubation was studied from lateral radiographs of patients lying supine on the operating table, with the neck in the normal, extended and flexed position. A computer programme calculated the anterior contour of the tube and the posterior contour of the airway as mean values of the original contours on the radiographs. The mean configuration of the airway in intubated individuals was then presented in a standard coordinate system. The results were compared with the shape of the airway in the same patients before intubation. This study and a previous one (1) have provided relevant data concerning airway anatomy that can be used in standardized testing of tube deformation forces. Our results also showed that patients were routinely placed on the operating table with the head in an unnecessarily extended position. Such a position may partly obstruct the blood flow in the vertebral arteries. An improvement in operating table design is desirable to facilitate optimal positioning of the patient's head during routine surgery.