Evaluation of Ultrasound Guided Measurement of Anterior Neck Soft Tissue Thickness in Predicting Difficult Laryngoscopy in Obese Patients

Abstract

Background: The incidence of unanticipated difficult airway is 14.3-17.5% in obese. Preoperative difficult airway prediction is important to avoid postoperative morbidity and mortality. USG guided measurement of anterior neck soft tissue thickness can be used to predict difficult laryngoscopy in obese patients and we thus undertook this study to determine the role of USG guided measurement of anterior neck thickness at the level of vocal cords in difficult laryngoscopy prediction.
 Methods: Sixty obese patients (BMI≥30kg/m2), 18-70 years of age of either sex, were included. Anterior neck soft tissue thickness was measured by ultrasound as the distance from the skin to the anterior commissure of vocal cord. Neck circumference was measured at mid neck just below the laryngeal prominence with the subjects standing upright and facing forward with shoulders relaxed. Thyromental distance, sternomental distance, Mallampatti score and neck circumference were also recorded.
 Results: The cut off values of BMI (46.94 kg/m2), neck circumference (41.5 cm) and anterior neck soft tissue thickness (22.1mm). Four patients in the morbidly obese and 80% of the superobese patients had a difficult laryngoscopy. Sixteen (26.67%) patients had an anterior neck soft tissue thickness of >22.1mm. Of these, 11 (91.67%) patients had difficult laryngoscopy while one (8.33%) patient with anterior neck soft tissue thickness ≤ 22.1mm had difficult laryngoscopy (P<0.05). There was also significant association between neck circumference and BMI.
 Conclusion: The USG guided measurement of anterior neck soft tissue thickness, BMI and neck circumference can reliably predict difficult laryngoscopy in obese patients.

Ultrasound-Guided Airway Evaluation: Is It a Game Changer for Predicting Difficult Endotracheal Intubation?

“…One of the earlier studies by Ezri et al [ 5 ] revealed that pre-tracheal soft tissue at the level of vocal cords (STT-VC) was a good predictor of difficult laryngoscopy in obese patients. Later, Wu et al [ 7 ], Reddy et al [ 13 ], and Jain et al [ 14 ] reported similar findings in their studies. However, a similar study by Komatsu et al [ 8 ] did not show any clinically significant difference in soft tissue thickness (STT) at the vocal cord level between difficult and easy laryngoscopy cases.…”

Prediction of Difficult Laryngoscopy Using Ultrasound: A Systematic Review and Meta-Analysis

“…However, half of the studies did not mention the exclusion of known difficult airway patients (7,(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39). All but three studies excluded morbidly obese patients (25,8,33). Several studies excluded pregnant patients (7,14,15,23,(34)(35)(36), whereas Xu et al (37) focused exclusively on pregnant patients.…”

“…Patients with known difficult airways or the presence of features likely associated with difficult airways were excluded by most studies (6, 13–25). However, half of the studies did not mention the exclusion of known difficult airway patients (7, 26–39).…”

“…Ultrasound training and experience were not defined in multiple studies (6, 13, 13, 14, 18, 21, 23–28, 31–33, 35–39). Ultrasound was performed by clinicians with quantifiable experience in three studies (15, 19, 20), and the remaining studies only described the sonographers as having received training or experience (7, 13, 16, 17, 22, 29, 30, 34, 40–42).…”

“…Actual difficult intubation was used as a comparator to ultrasound methods in three studies (15, 18, 42), and versions of the Cormack-Lehane classification were the reference standard in the remaining studies. When mentioned, the Cormack-Lehane classification was performed by anesthesiologists with 2–10 years of experience in studies (6, 8, 13, 15–18, 21, 23, 25, 26, 28–34, 36, 38, 40, 42), but relevant experience was not described in nine studies (7, 14, 18, 19, 23, 26, 35, 39).…”