Useful Ultrasonographic Parameters to Predict Difficult Laryngoscopy and Difficult Tracheal Intubation—A Systematic Review and Meta-Analysis

Abstract

Unexpected difficult airway management can cause significant morbidity and mortality in patients admitted for elective procedures. Ultrasonography is a promising tool for perioperative airway assessment, nevertheless it is still unclear which sonographic parameters are useful predictors of difficult laryngoscopy and tracheal intubation. To determine the ultrasonographic predictors of a difficult airway that could be applied for routine practice, a systematic review and meta-analysis was conducted. Literature search was performed on PubMED, Web of Science and Embase using the selected keywords. Human primary studies, published in English with the use of ultrasonography to prediction of difficult laryngoscopy or tracheal intubation were included. A total of 19 articles (4,570 patients) were analyzed for the systematic review and 12 articles (1,141 patients) for the meta-analysis. Standardized mean differences between easy and difficult laryngoscopy groups were calculated and the parameter effect size quantified. A PRISMA methodology was used and the critical appraisal tool from Joanna Briggs Institute was applied. Twenty-six sonographic parameters were studied. The overall effect of the distance from skin to hyoid bone (p = 0.02); skin to epiglottis (p = 0.02); skin to the anterior commissure of vocal cords (p = 0.02), pre-epiglottis space to distance between epiglottis and midpoint between vocal cords (p = 0.01), hyomental distance in neutral (p < 0.0001), and extended (p = 0.0002) positions and ratio of hyomental distance in neutral to extended (p = 0.001) was significant. This study shows that hyomental distance in the neutral position is the most reliable parameter for pre-operative airway ultrasound assessment. The main limitations of the study are the small sample size, heterogeneity of studies, and absence of a standardized ultrasonographic evaluation method [Registered at International prospective register of systematic reviews (PROSPERO): number 167931].

Morphometric and ultrasonographic determinants of difficult laryngoscopy in obese patients: A prospective observational study

“…Second, some ultrasonographic parameters were not examined, such as skin to epiglottis and skin to hyoid distances. 33 Third, our results may not be applicable to non-Asian populations due to the ethnic differences in morphometric and airway characteristics. 34 Fourth, although the risk of difficult laryngoscopy, defined as a Cormack and Lehane’s grade III or IV, was as high as 21.3% in this study, all patients were intubated successfully by direct laryngoscopy.…”

Point-of-Care Ultrasound in the Pediatric Intensive Care Unit

“…Airway ultrasound is promising in the prediction of a difficult laryngoscopy. A recent meta-analysis found robust test characteristics for prediction of a difficult laryngoscopy with significant sensitivity and specificity in adult patients using ultrasound ( 96 ). Ultrasound metrics evaluating anterior neck soft tissue thickness and mobility of the neck were found to be important predictors of a difficult laryngoscopy ( 96 ).…”

“…A recent meta-analysis found robust test characteristics for prediction of a difficult laryngoscopy with significant sensitivity and specificity in adult patients using ultrasound ( 96 ). Ultrasound metrics evaluating anterior neck soft tissue thickness and mobility of the neck were found to be important predictors of a difficult laryngoscopy ( 96 ). To date, only one pediatric study evaluating ultrasound for difficult laryngoscopy has been performed that demonstrated good sensitivity (100%) and negative predictive value (100%) but with modest specificity (62%) and positive predictive value (19%) ( 97 ).…”

Point-of-Care Ultrasound for the Trauma Anesthesiologist

“…To date, the majority of POCUS airway studies have focused on confirming that the endotracheal tube (ETT) is in the trachea and to identify the cricothyroid membrane for a surgical airway. A recent meta-analysis confirmed there may be some utility in preoperative POCUS airway assessment to predict difficult airway for routine anesthetic care[ 41 ] and there is evidence that these airway scans, when used in combination with the classic clinical airway exams, can reasonably predict difficult airway management [ 42 ]. The prediction of difficult airway relies on measurement of airway anatomical structures, which presents a challenge in rapidly deteriorating trauma patients.…”