Point-of-care ultrasound in the airway assessment: A correlation of ultrasonography-guided parameters to the Cormack–Lehane Classification

Abstract

Background and Aim:The sonographic assessment of airway in the preoperative period has encouraging results in predicting difficult laryngoscopy.Materials and Methods:The prospective, observational study was conducted on 120 patients scheduled for elective surgery requiring general anesthesia and tracheal intubation. The depth of the pre-epiglottic space (Pre-E), the distance from the epiglottis to the midpoint of the distance between the vocal cords (E-VC) was measured sonographically. Similarly, hyomental distance ratio (HMDR) was sonographically measured with head in neutral and extended positions. The primary outcome was the efficacy of Pre E/E-VC, HMDR for predicting difficult laryngoscopy (Cormack–Lehane [CL] Grade 3, 4). The secondary outcome was to correlate these parameters to CL grading.Results:Difficult intubation was observed in 12.5% of patients. The mean ± standard deviation (SD) of Pre E/E-VC ratio was 1.33±0.335, 1.62±0.264 and 1.87±.243, 2.22±.29 for CL Grade 1, 2, 3, and 4, respectively (P = 0.00). The mean ± SD of HMDR was 1.11±.35, 1.12±.29, and 1.07±.39, 1.04 ± 0.01 for CL Grade 1, 2, 3, and 4, respectively (P = 0.00). Pre E/E-VC ratio of more than 1.77 cm had 82% sensitivity, specificity 80%, whereas HMDR less than1.085 had sensitivity 75% and specificity 85.3%, in predicting difficult laryngoscopy (P = 0.00).Conclusion:The sonographic measurement of the Pre E/E-VC ratio is a better predictor of CL grading as compared to HMDR. The noninvasive prediction of CL grading can be precisely done by Pre-E/E-VC ratio (range: 0–1.425 corresponds to CL Grade 1; 1.425–1.77 ≈ CL Grade 2; 1.77–1.865 ≈ CL Grade 3, more than 1.865 corresponds to CL Grade 4).

Ultrasound measurement of anterior neck soft tissue and tongue thickness to predict difficult laryngoscopy - An observational analytical study

“…Previous studies on airway ultrasound have evaluated parameters such as tongue thickness, volume of tongue, skin to hyoid bone distance in supine and in neck extended position and ratio of these two distances, skin to thyrohyoid membrane distance, distance from the epiglottis to the midpoint of vocal cord (E-VC), depth of the pre-epiglottic space and ratio of these distances for predicting difficult laryngoscopy. [8910111213]…”

Clinical versus Ultrasound Measurements of Hyomental Distance Ratio for the Prediction of Difficult Airway in Patients with and without Morbid Obesity

“…Ultrasound is comparable to these, but is a cheaper, faster, non-irradiating, and non-invasive technique [25]. The sonographic assessment of the airway has encouraging results in predicting difficult laryngoscopy [9]. HMDR obtained by ultrasonography can be used for difficult airway prediction [10].…”

“…With a cutoff of 1.24, the sensitivity of ultrasound-measured HMDR was 86-100%, while the specificity was 72-90.5% in the non-obese and obese populations [10,11]. Using ROC analysis, Koundal et al found a cutoff of 1.08-1.085 for HMDR echo , with 65-75% sensitivity and 77-85% specificity [9,12]. However, a low sensitivity of 42.9% has also been reported, leading to the conclusion that these individual sonographic parameters, among others, have unsatisfactory diagnostic profiles [13].…”

“…The diagnostic accuracy of this parameter varied widely in subsequent studies, suggesting that evaluation of clinical parameters might be operator-dependent or that there might be difficulties regarding the palpation of the hyoid bone in certain patients [4][5][6][7][8]. In the last years, ultrasound measurements were applied for the hyomental distance ratio (HMDR echo ), also with variable sensitivity and specificity [9][10][11][12][13]. However, until now, each of the previous studies on HMDR focused on a single technique of measurement, either clinical or ultrasonographical, and no study compared the two.…”

Measurement of subglottic diameter and distance to pre-epiglottic space among Chinese adults

“…Also, several US studies have been conducted regarding DSE and difficult intubations. Rana et al reported that the ratio between DSE and distance from the epiglottis to the midpoint of the vocal cord was a good predictor of difficult laryngoscopy in 120 patients receiving elective surgery [33]. Gupta et al reported a strong association between the pre-epiglottic distance and the Cormack-Lehane classification [14].…”