RELATIONSHIP BETWEEN DIFFICULT TRACHEAL INTUBATION AND OBSTRUCTIVE SLEEP-APNEA

The upper airway abnormalities predisposing to difficult tracheal intu bation may also predispose to obstructive sleep apnoea (OSA). The pote ntial association is important as both conditions increase perioperati ve risk and patients with a trachea that is difficult to intubate may need assessment for OSA. We determined if patients with difficult intu bation are at greater risk of OSA and, if so, whether or not they have characteristic clinical;or radiographic upper airway changes. We stud ied 15 patients in whom the trachea was difficult to intubate and 15 c ontrol patients. Each was evaluated clinically (Mallampati score, thyr omental distance, neck circumference, head extension), polysomnographi cally (apnoeahypopnoea index (AHI)) and radiographically (lateral ceph alometry). AHI was greater in the difficult intubation group (mean 28. 4 (SD 31.7)) compared with controls (5.9 (8.9)) (P<0.02); eight of 15 patients in the difficult intubation group and two of 15 in the contro l group had an AHI >10 (P<0.03). Difficult intubation, but not OSA, wa s associated (P<0.05) with a smaller thyromental distance and mandibul ar length, and greater soft palate length. Both difficult intubation a nd OSA were associated (P<0.05) with a greater Mallampati score, anter ior mandibular depth, and smaller mandibular and cervical angles. OSA, but not difficult intubation, was associated (P<0.05) with increased neck circumference, tongue area and craniocervical angle, and decrease d head extension, mandibular ramus length and atlantooccipital distanc e. We conclude that difficult intubation and OSA are related significa ntly. They share anatomical features which act to reduce the skeletal confines of the tongue. Patients with OSA may compensate, when awake, by increasing craniocervical angulation, which increases the space bet ween the mandible and cervical spine and elongates the tongue and soft tissues of the neck.