Ultrasonographic prediction of difficult laryngoscopy in obese patients

Introduction: Anticipation of difficulties in airway management is of prime importance in avoiding potential catastrophies. Obese patients form part of a population that is believed to have difficult airway. Ultrasound imaging has recently come forth as a simple, portable, noninvasive adjunct for bedside assessment. We hypothesized that there is an association between ultrasonographic measurements of the anterior neck soft-tissue thickness at level of vocal cords (VCs) and hyoid bone (HB) in predicting difficult laryngoscopy in the obese patients and evaluated the feasibility of ultrasound in predicting difficult laryngoscopy in Indian population. Materials and Methods: A total of 70 obese patients with body mass index >30 kg/m2 and American Society of Anesthesiologists Grade I and II undergoing elective surgeries and receiving general anesthesia were enrolled in the study. Ultrasound quantification of the anterior neck soft tissue was performed using a high-frequency (13-6 MHz) linear transducer. The distance from the skin to the anterior aspect of the trachea was measured at two levels: VCs and HB. Results: The incidence of difficult laryngoscopy (III and IV) in our study population was 24.3% (17 of 70 cases). The sonographic measurements of the skin thickness of the anterior neck were greater at the level of VCs in the difficult laryngoscopy group at 13.5 +/- 1.5 mm as compared to the easy laryngoscopy group at 10.2 +/- 1.6 mm, with the difference being statistically significant, P < 0.001. The soft-tissue thickness at the level of HB was also greater in the difficult laryngoscopy group in contrast to the easy laryngoscopy group (16.4 +/- 1.9 mm vs. 12.4 +/- 2.0 mm; P < 0.001). Conclusions: Ultrasonographically measured skin thickness at the level of HB and VCs has got a good correlation with difficult intubation.