title: Submandibular sonography: assessment of hyomental distances and ratio, tongue size, and floor of the mouth musculature using portable sonography.
abstract: OBJECTIVE
  The aim of this study was to evaluate the feasibility of sonography as a tool to measure the hyomental distance ratio and tongue size in obese patients with a large neck circumference. The hyomental distance ratio is a predictor of difficult laryngoscopy that may result in difficult intubation.
  
  
  METHODS
  Five obese and 7 morbidly obese adult patients with a history of either difficult or easy intubation had a submandibular sonographic examination performed in the supine position. The hyomental distance was measured while the head was placed in the neutral position and then in a hyperextended position, and the ratio of two distances (hyomental distance ratio) was calculated. Their tongue volumes were derived from multiplication of the midsagittal cross-sectional area of the tongue by its width obtained from transverse sonograms.
  
  
  RESULTS
  The mean hyomental distance ratios ± SD in 6 patients with difficult intubation and 6 with easy intubation were 1.02 ± 0.01 and 1.14 ± 0.02 (P < .002), respectively. Tongue volumes did not differ statistically between the two groups: 137 ± 29 cm(3) (difficult intubation) and 168 ± 34 cm(3) (easy intubation). The mean body mass indices were 36.3 ± 6.0 and 43.2 ± 7.2 kg/m(2) in the difficult and easy intubation groups. The mean neck circumferences were 44.5 ± 7.4 and 46.8 ± 7.0 cm in the difficult and easy intubation groups.
  
  
  CONCLUSIONS
  Sonography allows bedside measurements of the hyomental distance ratio and tongue size in morbidly obese patients. Preoperative assessment of the hyomental distance ratio may predict difficult laryngoscopy resulting in difficult intubation.
authors.affiliation: Department of Anesthesiology, Box 604, University of Rochester School of Medicine and Dentistry, 601 Elmwood Ave, Rochester, NY 14642, USA. gryf70@yahoo.com
authors.forename: Jacek A
authors.initials: JA
authors.lastname: Wojtczak
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D006928:Hyoid Bone; D007442:Intubation, Intratracheal / Q000379:methods; D008297:Male; D008334:Mandible / Q000000981:diagnostic imaging*; D008875:Middle Aged; D009055:Mouth / Q000000981:diagnostic imaging*; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging*; D009767:Obesity, Morbid / Q000000981:diagnostic imaging*; D019095:Point-of-Care Systems; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014059:Tongue / Q000000981:diagnostic imaging*; D014463:Ultrasonography / Q000379:methods*; D055815:Young Adult