Submandibular sonography: assessment of hyomental
distances and ratio, tongue size, and floor of the mouth musculature using portable sonography.
Patient Characteristics Parameter Mean [+ or -]SD Age (year) 45.2 15.8 Sex ratio (male/female) 106/94 -- Weight (kg) 58.65 14.31 Height (cm) 156.97 10.30 BMI (kg/m2) 23.90 5.30 Mouth Opening 2.87 0.32 Mallampati Grade (I/II) 145/47 -- Neck movement (NM) A/R 180/20 -- Neck circumference (NC) 35.77 5.02 Hyomental
distance (HM) 5.1 0.92 Thyromental distance (TM) 7.21 1.25 NC/TMD 5.10 1.10 NC/SM 2.38 0.56 Ratio of height to thyromental distance 22.45 4.31 Intubation Difficulty Scale (IDS) 2.02 2.55 Data are represented as mean [+ or -] SD, n (%) and ratio, SD=Standard deviation.
(14) Measurements by sonography and ImageJ did not indicate tongue size alone to be statistically significant between difficult and easy intubation, though hyomental
distance in the head-extended position was found to be statistically significant.
The hyomental distance ratio (HMDR) is the ratio between the hyomental distance (HMD) (the distance between the hyoid bone and the tip of the chin) at the extreme of head extension (HMDe) and the one in the neutral position (HMDn).
Preoperative evaluation of extension capacity of the occipitoatlantoaxial complex in patients with rheumatoid arthritis: Comparison between the Bellhouse test and a new method, hyomental distance ratio.
thyromental distance, hyomental
distance, inter-incisor distance to predict difficult airway may prove to be better to predict difficult intubation.
Another study found that pretracheal soft tissue thickness is not a good indicator for difficult intubation in morbidly obese patients.21 Wojtczak's study22 showed that hyomental space measurements using USG can be useful in predicting difficult intubation.
Submandibular sonography: assessmentof hyomental distances and ratio tongue size and floorof the mouth musculature using portable sonography.
These include assessment of relative tongue pharyngeal size (Mallampati Classification)4 (Figure); atlanto-occipital extension in assuring sniff or Magil position 5 assessed by Wilson Risk Sum (Table); and Thyromental or hyomental
distance to assess mandibular space (space anterior to larynx) with a ruler 6.
There are other parameters like movements of head and neck, sternomental and hyomental
distance, length of mandible that is horizontal and neck circumference, etc.
Thyromental distance less than 6 cm, sternomental distance less than 12.5 cm, hyomental
distance less than two large finger breadths, anteriorly tilted larynx and reduction of atlanto-occipital joint extension suggest difficult intubation.
Not much work has been published regarding the use of HMD (Hyomental
Distance) or TSD (Thyrosternal Distance) as screening tests to detect difficulty in intubation.