Figure 4. Cervical spine extension during laryngoscopy with best laryngeal view. The ordinate shows the difference in angles between the radiography with laryngoscopy and the baseline radiograph for each joint in the cervical spine from the atlan-tooccipital joint (C0-C1) to C3-C4. The points represent individual patients, and line segments connect the data from the same patient for the Macintosh and Bullard laryngoscopes. Angle measurements by the two radiologists were averaged. Similar results were obtained for cervical spine extension with arytenoid exposure (not shown). *P < 0.05.