Pilot Study to Determine the Utility of Point‐of‐care Ultrasound in the Assessment of Difficult Laryngoscopy

Abstract

Objectives: Prediction of difficult laryngoscopy in emergency care settings is challenging. The preintubation clinical screening tests may not be applied in a large number of emergency intubations due to the patient's clinical condition. The objectives of this study were 1) to determine the utility of sonographic measurements of thickness of the tongue, anterior neck soft tissue at the level of the hyoid bone, and thyrohyoid membrane in distinguishing difficult and easy laryngoscopies and 2) to examine the association between sonographic measurements (thickness of tongue and anterior neck soft tissue) and difficult airway clinical screening tests (modified Mallampati score, thyromental distance, and interincisor gap).Methods: This was a prospective observational study at an academic medical center. Adult patients undergoing endotracheal intubation for an elective surgical procedure were included. The investigators involved in data collection were blinded to each other's assessments. Demographic variables were collected preoperatively. The clinical screening tests to predict a difficult airway were performed. The ultrasound (US) measurements of tongue and anterior neck soft tissue were obtained. The laryngoscopic view was graded using Cormack and Lehane classification by anesthesia providers on the day of surgery. To allow for comparisons between difficult airway and easy airway groups, a two-sided Student's t-test and Fisher's exact test were employed as appropriate. Spearman's rank correlation coefficients were used to examine the association between screening tests and sonographic measurements. Results:The mean (±standard deviation [SD]) age of 51 eligible patients (32 female, 19 male) was 53.1 (±13.2) years. Six of the 51 patients (12%, 95% confidence interval [CI] = 3% to 20%) were classified as having difficult laryngoscopy by anesthesia providers. The distribution of laryngoscopy grades for all subjects was 63, 25, 4, and 8% for grades 1, 2, 3, and 4, respectively. In this study, 83% of subjects with difficult airways were males. No other significant differences were noted in the demographic variables and difficult airway clinical screening tests between the two groups. The sonographic measurements of anterior neck soft tissue were greater in the difficult laryngoscopy group compared to the easy laryngoscopy group at the level of the hyoid bone (1.69, 95% CI = 1.19 to 2.19 vs. 1.37, 95% CI = 1.27 to 1.46) and thyrohyoid membrane (3.47, 95% CI = 2.88 to 4.07 vs. 2.37, 95% CI = 2.29 to 2.44). No significant correlation was found between sonographic measurements and clinical screening tests.Conclusions: This pilot study demonstrated that sonographic measurements of anterior neck soft tissue thickness at the level of hyoid bone and thyrohyoid membrane can be used to distinguish difficult and easy laryngoscopies. Clinical screening tests did not correlate with US measurements, and US was able to detect difficult laryngoscopy, indicating the limitations of the conventional screening tests for predicting ...

Ultrasound-based assessment of hyomental distances in neutral, ramped, and maximum hyperextended positions, and derived ratios, for the prediction of difficult airway in the obese population: a pilot diagnostic accuracy study

“…However, data on the impact of US use in airway management remain limited [14]. In the non-obese population, the ultrasonographic measurements of the distance from skin to epiglottis, the ability or inability to visualise the hyoid bone by performing sublingual sonography, and tongue thickness, have been correlated with Cormack-Lehane scores [15][16][17][18][19][20]. Similarly, in the obese population, the pretracheal soft tissue thickness has been linked to difficult airway [21].…”

Intrathecal opioids and fetal heart rate abnormalities

“…Importantly, the use of higher doses of fentanyl is not associated with a bupivacaine dose-sparing effect. The ED 95 for plain bupivacaine with 15 lg fentanyl is 1.66 lg [3]. Since the dose we used was significantly above both ED 50 and ED 95 , we do not believe that this easily explains why a proportion of parturients in the CSE group experienced ineffective analgesia.…”

“…The authors noted that deterioration in the fetal heart rate pattern has a multifactorial causation, but is usually transient, resolving spontaneously or following intrauterine fetal resuscitative measures, including the reduction or discontinuation of oxytocin before initiation of analgesia, fluid administration, and/or reducing the dose of intrathecal opioids [2,3]. However, the authors do not justify their use of a low dose of intrathecal fentanyl (5 lg) in the present study, when most published literature supports the use of intrathecal fentanyl ≥ 15 lg for analgesia [4], which may explain why 32% of parturients in the CSE group had ineffective analgesia.…”

Is there a correlation of sonographic measurements of true vocal cords with gender or body mass indices in normal healthy volunteers?

“…looked at sonographic measurements of anterior neck soft-tissue thickness at the level of hyoid bone and thyrohyoid membrane, but not vocal cord measurements to help distinguish difficult and easy laryngoscopies. [13] There is limited literature on the sonographic measurements of true vocal cords in adults[8] and normal parameters must be established before abnormal parameters can be accurately identified. There has only been one study investigating the parameters for real and false vocal cords according to age group.…”