To the Editor: We applaud Kanaya et al.’s effort in research for the cause of unanticipated difficult endotracheal intubations (1,2). Their findings of narrowing pharyngolaryngeal space, posterior displacement of epiglottis, and lowering of larynx, as well as their three-dimensional computed tomography (3D-CT) evaluation method and two-person fiberscope-aided intubation technique, are interesting and different from traditional teachings. In our practice, we have been using cervical soft tissue radiography and WuScope (Achi Corporation, Fremont, CA) in evaluating and managing similar airway problems. In our view, a further explanation to Kanaya et al.’s (1,2) findings can be provided based on the concept of long mandibulohyoid distance (MHD) (3) and large hypopharyngeal tongue (4) in patients with a relatively short mandibular ramus and/or caudally positioned larynx (5,6) and our understanding of difficult laryngoscopy (7). Figure 1 is the radiograph of such a patient. Under general anesthesia, only the tip of the epiglottis could be seen with a conventional blade. Flexible fiberoptic intubation failed because of an inability to advance the fibercord beyond the epiglottis. Then, the WuScope was used with tip of blade placed into the vallecula, exerting slight tension on the glossoepiglottic mucous membrane; the epiglottis was raised, larynx exposed, and trachea intubated.Figure 1: Lateral cervical soft tissue radiograph of a 55-yr-old woman (91 kg, 183 cm) with difficult endotracheal intubation. Patient’s head was in upright neutral position with mouth closed and occlusal line horizontal. Atlanto-occipital gap (AOG) was measured from upper margin of posterior tubercle of atlas (A) vertically upward to occiput (O). Mandibular angle was determined by drawing a horizontal line from the intersection of two tangents of posterior ramus and lower border of the mandible (M), across to the cervical spine. Position of the hyoid bone (H) was determined by drawing a horizontal line from the upper margin of the hyoid bone (H) to the adjacent cervical spine. Mandibulohyoid distance (MHD) was measured from the upper margin of the hyoid bone (H) vertically upward to the lower margin of the mandible (M). Arrow was inserted to point to the epiglottis (E). The radiographic results in this patient showed AOG = 0 mm; unusually rostral mandibular angle at upper C2 (normal level, lower C2 or C2-3); very long MHD = 38 mm (normal female mean, 15 mm); and hyoid at relatively normal level of C3-4. The presence of a relatively short mandibular ramus is evident. Note the air and soft tissue contrast clearly demonstrates a large hypopharyngeal tongue with a long and narrow pharyngolaryngeal airway passage.As seen from the radiograph, the greater rostrocaudal separation of mandible and hyoid (longer MHD) renders a large portion of the tongue mass to situate in the confined neck trunk instead of the oral cavity, thus creating a long and narrow airway passage to the larynx. When the patient is upright or awake, there may be adequate air space between the epiglottis and posterior pharyngeal wall (Fig. 1). However, when the patient is supine and under general anesthesia, the large hypopharyngeal tongue weighs down on the epiglottis and against the posterior wall, diminishing the space permissible for the fibercord to pass through. Moreover, the fiberscope lacks the mechanical means to raise or pick up the epiglottis. In our view, Kanaya et al.’s (1,2) two-person intubation technique aims at overcoming the inherent deficiency of a flexible fiberscope by supplying the mechanical advantage of a rigid blade. The rigid tubular fiberoptic, one-person operated WuScope is in fact such a combination laryngoscope that creates space and raises or picks up the epiglottis. In summary, Kanaya et al.’s (1,2) findings for unanticipated difficult intubations are consistent with our conclusions (3–7). Cervical radiography and the WuScope may be simple and effective alternatives to the 3D-CT and two-person technique in evaluating and managing these airway problems. Hsiu-chin Chou, MD Tzu-lang Wu, MD