The usefulness of point of care ultrasound (POCUS) in preanaesthetic airway assessment

Evaluation of preoperative difficult airway prediction methods for adult patients without obvious airway abnormalities: a systematic review and meta-analysis

BACKGROUND

This systematic review aims to assist clinical decision-making in selecting appropriate preoperative prediction methods for difficult tracheal intubation by identifying and synthesizing literature on these methods in adult patients undergoing all types of surgery.

METHODS

A systematic review and meta-analysis were conducted following PRISMA guidelines. Comprehensive electronic searches across multiple databases were completed on March 28, 2023. Two researchers independently screened, selected studies, and extracted data. A total of 227 articles representing 526 studies were included and evaluated for bias using the QUADAS-2 tool. Meta-Disc software computed pooled sensitivity (SEN), specificity (SPC), positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR). Heterogeneity was assessed using the Spearman correlation coefficient, Cochran's-Q, and I2 index, with meta-regression exploring sources of heterogeneity. Publication bias was evaluated using Deeks' funnel plot.

RESULTS

Out of 2906 articles retrieved, 227 met the inclusion criteria, encompassing a total of 686,089 patients. The review examined 11 methods for predicting difficult tracheal intubation, categorized into physical examination, multivariate scoring system, and imaging test. The modified Mallampati test (MMT) showed a SEN of 0.39 and SPC of 0.86, while the thyromental distance (TMD) had a SEN of 0.38 and SPC of 0.83. The upper lip bite test (ULBT) presented a SEN of 0.52 and SPC of 0.84. Multivariate scoring systems like LEMON and Wilson's risk score demonstrated moderate sensitivity and specificity. Imaging tests, particularly ultrasound-based methods such as the distance from the skin to the epiglottis (US-DSE), exhibited higher sensitivity (0.80) and specificity (0.77). Significant heterogeneity was identified across studies, influenced by factors such as sample size and study design.

CONCLUSION

No single preoperative prediction method shows clear superiority for predicting difficult tracheal intubation. The evidence supports a combined approach using multiple methods tailored to specific patient demographics and clinical contexts. Future research should focus on integrating advanced technologies like artificial intelligence and deep learning to improve predictive models. Standardizing testing procedures and establishing clear cut-off values are essential for enhancing prediction reliability and accuracy. Implementing a multi-modal predictive approach may reduce unanticipated difficult intubations, improving patient safety and outcomes.

The diagnostic accuracy of point-of-care ultrasound parameters for airway assessment in patients undergoing intubation in emergency department-an observational study

BACKGROUND

Endotracheal intubation is an essential resuscitative procedure in the emergency setting. Airway assessment parameters such as the Mallampati classification are difficult to perform in an emergency setting. As point-of-care ultrasound (POCUS) assessment of airway parameters does not require patients to perform any mandatory action, ultrasound may become the potential first-line noninvasive airway assessment tool in the emergency department (ED). The use of POCUS in the ED has not been sufficiently studied. Using POCUS in airway assessment for predicting difficult intubation may be the next step in successful airway management.

METHODOLOGY

The study was an observational study conducted at the ED of the All India Institute of Medical Sciences (Rishikesh). The treating emergency physician recorded the patient history and systemic examination along with an indication for intubation. The POCUS assessment of airway parameters pre-epiglottis to epiglottic vocal cord ratio (Pre-E/E-VC), tongue thickness, hyomental distance, and distance from skin to the hyoid bone was performed by the study investigator. During laryngoscopy, Cormack-Lehane (CL) grading was assessed. The data was entered and analyzed.

RESULTS

Seventy patients who required intubation in the ED were enrolled in the study. Among the study population, 48.6%, 28.6%, 14.3%, 1.4%, and 7.1% were classified with the following CL grading: 1, 2a, 2b, 3a, and 3b, respectively. At a cutoff of ≥ 1.86, Pre-E/E-VC predicts difficult laryngoscopy (AUC 0.835) with a sensitivity of 83% and a specificity of 94%. At a cutoff of ≥ 5.98 cm, tongue thickness predicts difficult laryngoscopy (AUC 0.78) with a sensitivity of 83% and a specificity of 88%. At a cutoff of hyomental distance ≤ 6 cm, it predicts difficult laryngoscopy with a sensitivity of 83% and a specificity of 88%. All parameters can act as a promising tool for predicting difficult laryngoscopy, with the single best parameter being Pre-E/E-VC.

CONCLUSION

Assessment of the airway with POCUS may be helpful to the emergency physician when the clinical airway assessment parameters fail to predict difficult laryngoscopy as most patients requiring intubation are uncooperative. Assessment of the parameters in our study Pre-E/E-VC, tongue thickness, and hyomental distance can act as a promising tool for predicting difficult laryngoscopy in the emergency scenario.

A Scoping Review of Ultrasonographic Techniques in the Evaluation of the Pediatric Airway

Point-of-care ultrasound is making rapid advancements in pediatrics, and ultrasonographic assessment of the airway is being employed in many specialties such as the pediatric, cardiac, and neonatal intensive care units, emergency department, pulmonary clinic, and the perioperative setting. This scoping review provides a technical description of image acquisition and interpretation, accompanying ultrasound images of the hallmark airway applications in pediatrics, and supporting evidence when available. We describe and illustrate ultrasound-determined endotracheal tube (ETT) sizing, ETT placement and depth confirmation, vocal fold assessment, prediction of post-extubation stridor, difficult laryngoscopy prediction, and cricothyrotomy guidance. This review aims to provide the descriptions and images necessary to learn and apply these skills at the point of care in the pediatric patient.

Expert consensus on difficult airway assessment

Background

Identifying a potentially difficult airway is crucial both in anaesthesia in the operating room (OR) and non-operation room sites. There are no guidelines or expert consensus focused on the assessment of the difficult airway before, so this expert consensus is developed to provide guidance for airway assessment, making this process more standardized and accurate to reduce airway-related complications and improve safety.

Methods

Seven members from the Airway Management Group of the Chinese Society of Anaesthesiology (CSA) met to discuss the first draft and then this was sent to 15 international experts for review, comment, and approval. The Grading of Recommendations, Assessment, Development and Evaluation (GRADE) is used to determine the level of evidence and grade the strength of recommendations. The recommendations were revised through a three-round Delphi survey from experts.

Results

This expert consensus provides a comprehensive approach to airway assessment based on the medical history, physical examination, comprehensive scores, imaging, and new developments including transnasal endoscopy, virtual laryngoscopy, and 3D printing. In addition, this consensus also reviews some new technologies currently under development such as prediction from facial images and voice information with the aim of proposing new research directions for the assessment of difficult airway.

Conclusions

This consensus applies to anesthesiologists, critical care, and emergency physicians refining the preoperative airway assessment and preparing an appropriate intubation strategy for patients with a potentially difficult airway.

Pre-operative ultrasound prediction of difficult airway management in adult patients: A systematic review of clinical evidence

BACKGROUND

Predicting a difficult airway, including difficult laryngoscopy, intubation or mask ventilation, is paramount in peri-operative management. As clinical predictors are only partially reliable, ultrasound-based measurements might be useful in evaluating anterior neck fat tissues depth.

OBJECTIVES

The aim of this systematic review is to report clinical evidence on pre-operative ultrasound as a predictor of difficult laryngoscopy, difficult intubation or difficult mask ventilation.

DESIGN

A systematic review of randomised controlled trials and observational studies.

DATA SOURCES

The MEDLINE, EMBASE and Google Scholar databases were queried from inception until 28 February 2022.

ELIGIBILITY CRITERIA

Studies involving adult patients who had undergone orotracheal intubation after evaluation with airways ultrasound were considered suitable. Exclusion criteria were a clinical history of difficult airways, cancer or trauma, pregnancy, supraglottic airway devices, video-laryngoscopy. Parameters were classified by reporting their accuracy in discriminating 'difficult' vs. 'not difficult' laryngoscopy, intubation or mask ventilation.

RESULTS

Thirty-one observational studies were included and a total of 41 single parameters and 12 different combinations of clinical and ultrasound parameters were reported. The distance from skin to epiglottis midway with neutral position of head and neck, the distance from hyoid bone to skin surface with a neutral position of head and neck and the hyomental distance extended/neutral ratio are the most associated with difficult laryngoscopy or difficult intubation. A combination of clinical and ultrasound parameters (a modified Mallampati score, the distance from the skin to the epiglottis midway with neutral position of the head and neck, and the USED-MSH score) showed high accuracy. Only two studies reported the role of ultrasound in predicting difficult mask ventilation: the distance from hyoid bone to skin surface with neutral position of head and neck, the thickness of the base of the tongue with hyperextension of the head, and the hyomental distance with hyperextension of the head and active subluxation of the mandible are the parameters with the highest correlation.

CONCLUSIONS

The use of ultrasound parameters might be useful in predicting difficult laryngoscopy or difficult intubation. Several ultrasound parameters and combinations have been associated with difficult laryngoscopy or difficult intubation prediction. The use of scores combining clinical predictors and ultrasound measures are very promising. Data on difficult mask ventilation are scarce and the role of ultrasound is still controversial. Future studies are needed.

CLINICAL TRIAL REGISTRATION

CRD42021250574.

Point-of-Care Ultrasound in Airway Evaluation and Management: A Comprehensive Review

Airway management is a common and critical procedure in acute settings, such as the Emergency Department (ED) or Intensive Care Unit (ICU) of hospitals. Many of the traditional physical examination methods have limitations in airway assessment. Point-of-care ultrasound (POCUS) has emerged as a promising tool for airway management due to its familiarity, accessibility, safety, and non-invasive nature. It can assist physicians in identifying relevant anatomy of the upper airway with objective measurements of airway parameters, and it can guide airway interventions with dynamic real-time images. To date, ultrasound has been considered highly accurate for assessment of the difficult airway, confirmation of proper endotracheal intubation, prediction of post-extubation laryngeal edema, and preparation for cricothyrotomy by identifying the cricothyroid membrane. This review aims to provide a comprehensive overview of the key evidence on the use of ultrasound in airway management. Databases including PubMed and Embase were systematically searched. A search strategy using a combination of the term "ultrasound" combined with several search terms, i.e., "probe", "anatomy", "difficult airway", "endotracheal intubation", "laryngeal edema", and "cricothyrotomy" was performed. In conclusion, POCUS is a valuable tool with multiple applications ranging from pre- and post-intubation management. Clinicians should consider using POCUS in conjunction with traditional exam techniques to manage the airway more efficiently in the acute setting.

Evaluation of ultrasound airway assessment parameters in pregnant patients and their comparison with that of non-pregnant women: a prospective cohort study

BACKGROUND

Clinical airway assessment parameters differ significantly between pregnant and non-pregnant patients, however literature comparing their ultrasound (US) airway parameters is limited. We planned a prospective cohort study to compare US-assessed airway parameters between pregnant and non-pregnant women.

METHODS

We enrolled 82 pregnant females scheduled for elective cesarean section under neuraxial anesthesia and 80 age-matched non-pregnant females scheduled for elective surgery. Pre-operative clinical airway assessment was performed in both groups. The US airway assessment was done pre-operatively in non-pregnant and postoperatively in pregnant patients. Our primary objective was to compare US-assessed parameters, and secondary objectives included a comparison of clinical airway assessment parameters and investigating a relationship between a difficult airway (defined as a modified Mallampati grade (MMG) ≥ 3) and other airway assessment parameters.

RESULTS

Among several US airway parameters, pregnant patients had significantly higher hyomental distance, anterior neck soft tissue thickness at the hyoid and vocal cord level, and oral cavity height, while the tongue thickness and mandibular condylar movements were significantly lower than in non-pregnant patients. Similarly, for the clinical airway assessment, pregnant patients had significantly higher MMG and upper lip bite test scores, mentohyoid distance, and neck circumference. Pregnancy, the ratio of pre-epiglottic space and epiglottis-to-vocal cords distance (Pre-E/E-VC), and hyoid bone visibility were independent predictors of a difficult airway.

CONCLUSION

The US airway assessment parameters differ significantly between pregnant and non-pregnant patients. Pregnancy, hyoid bone visibility, and Pre-E/E-VC ratio were independent predictors of the difficult airway in female patients.

Accuracy of airway ultrasound parameters to predict difficult airway using the LEMON criteria as a reference: A cross-sectional diagnostic accuracy study

OBJECTIVES

Ultrasound (US) airway indexes were frequently compared with other scoring systems such as Mallampati score and Cormack - Lehane classification system, but to the best of our knowledge never with LEMON. Here, in this study, we evaluated the accuracy of some recommended airway US parameters in terms of screening difficult airway using the LEMON criteria as a reference.

METHODS

This was a cross-sectional diagnostic accuracy study in which people with at least 18 years old coming to the emergency departments for any reason who had consent for participation, were enrolled with the simple random sampling method. Hyo-mental distance (HMD), skin to epiglottis distance (EP), and peri-epiglottic space to epiglottis to vocal cord ratio (PEP/E. VC) were the US indexes that were calculated in all participants. Using a preprepared checklist, measured US parameters were recorded. For each participant, the LEMON score variables were also assessed and recorded, and the cutoff point for considering as a difficult airway case, based on LEMON score, was 2. Demographic characteristics of the participants were also registered.

RESULTS

A total of 299 cases with a mean age of 41.1 years (95% confidence interval [CI]: 39.3-42.9), were participated. Based on LEMON score ≥2, 20 participants (6.7%) were categorized in difficult airway group. Comparison of the PEP/E. VC (P = 0.007) and EP distance (P = 0.049) of the participants based on LEMON score showed a statistically significant difference; but comparison of the means of HMD in the two groups was not statistically significant (P = 0.144). The median of EP of the participants was 7.70 mm (interquartile range [IQR]: 6.70-9.40). The best cutoff point of EP distance for evaluating a difficult airway was 12.27 mm and more with the sensitivity of 35% and the specificity of 86.96% (accuracy = 0.614; 95% CI: 0.492-0.736). The median of PEP/E. VC was 1.01(IQR: 0.79-1.23). The best cutoff point of PEP/E. VC for evaluating a difficult airway was 0.88 and less with the sensitivity of 70% and the specificity of 67.38% (accuracy = 0.701; 95% CI: 0.583-0.818).

CONCLUSION

As per our results, PEP/E. VC and EP distance measured with sonography can be used in distinguishing the difficult airway, using the LEMON criteria as the reference. However, further studies are needed to use PEP/E. VC and EP distance as a part of reliable indexes.

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

OBJECTIVES

Evaluate associations between ultrasound measures and difficult laryngoscopy.

DATA SOURCES

MEDLINE, Embase, Google Scholar, Web of Science, and the Cochrane Library were searched using MeSH terms and keywords.

STUDY SELECTION

Studies published in English describing the use of airway ultrasound for identifying difficult laryngoscopy, with sufficient data to calculate sensitivity and specificity using 2 × 2 tables.

DATA EXTRACTION

We assigned the described indices of airway dimension to one of three domains based on methodology characteristics: anterior tissue thickness domain, anatomical position domain, and oral space domain. We then performed a bivariate random-effects meta-analysis, deriving pooled sensitivity, specificity, diagnostic odds ratio, positive likelihood ratio, and negative likelihood ratio estimates. We assessed risks of bias using Quality Assessment of Diagnostic Accuracy Studies-2 analysis.

DATA SYNTHESIS

Thirty-three studies evaluating 27 unique indices were included in the meta-analysis. The ultrasound protocols of the included studies were heterogeneous. Anterior tissue thickness demonstrated a pooled sensitivity of 76% (95% CI, 71-81%), specificity of 77% (95% CI, 72-81%), and an area under the receiver operating characteristic curve (AUROC) of 0.83 (95% CI, 0.80-0.86). Anatomical position demonstrated a pooled sensitivity of 74% (95% CI, 61-84%), specificity of 86% (95% CI, 78-91%), and an AUROC of 0.87 (95% CI, 0.84-0.90). Oral space demonstrated a pooled sensitivity of 53% (95% CI, 0.36-0.69), specificity of 77% (95% CI, 0.67-0.85), and an AUROC of 0.73 (95% CI, 0.69-0.77).

CONCLUSIONS

Airway ultrasound metrics associate with difficult laryngoscopy in three domains: anterior tissue thickness, anatomic position, and oral space. An assessment instrument combining clinical and ultrasound assessments may be an accurate screening tool for difficult laryngoscopy.

Airway Ultrasound for Anesthesia and in Intensive Care Patients-A Narrative Review of the Literature

Ultrasound is an everyday diagnostic tool. In anesthesia and intensive care, it has a role as an adjuvant for many procedures, including the evaluation of the airway. Ultrasound airway evaluation can help predict a difficult airway, visualize the proper positioning of an intubation cannula, or evaluate the airway post-intubation. Protocols need to be established for the better integration of ultrasound in the airway evaluation, however until a consensus is reached in this respect, the ultrasound is a reliable aid in anesthesia and intensive care.

Airway Ultrasound in Critically Ill Patients: A Narrative Review

Airway assessment and management have a central role in critical care medicine. Airway ultrasound can help us evaluate the anatomy, facilitate interventions such as intubation in difficult airways and tracheostomy, prevent post-extubation complications, and diagnose dysphagia. In this review, we will summarize the current use of ultrasound in airway assessment and management in critically ill patients.

2022 American Society of Anesthesiologists Practice Guidelines for Management of the Difficult Airway

The American Society of Anesthesiologists; All India Difficult Airway Association; European Airway Management Society; European Society of Anaesthesiology and Intensive Care; Italian Society of Anesthesiology, Analgesia, Resuscitation and Intensive Care; Learning, Teaching and Investigation Difficult Airway Group; Society for Airway Management; Society for Ambulatory Anesthesia; Society for Head and Neck Anesthesia; Society for Pediatric Anesthesia; Society of Critical Care Anesthesiologists; and the Trauma Anesthesiology Society present an updated report of the Practice Guidelines for Management of the Difficult Airway.

Airway Ultrasound as Predictor of Difficult Direct Laryngoscopy: A Systematic Review and Meta-analysis

Despite several clinical index tests that are currently applied for airway assessment, unpredicted difficult laryngoscopy may still represent a serious problem in anesthesia practice. The aim of this systematic review and meta-analysis was to evaluate whether preoperative airway ultrasound can predict difficult direct laryngoscopy in adult patients undergoing elective surgery under general anesthesia.

Limited condylar mobility by ultrasonography predicts difficult direct laryngoscopy in morbidly obese patients: An observational study

Background and Aims

Unpredictable difficult laryngoscopy remains a challenge for anaesthesiologists, especially in morbidly obese patients. The present study aimed to determine the efficacy of different sonographic measures as predictors of difficult laryngoscopy in morbidly obese patients undergoing elective surgery.

Methods

This observational study evaluated 70 morbidly obese adult patients (body mass index >35 kg/m²) undergoing elective surgery under general anaesthesia with tracheal intubation. Pre-operative clinical and ultrasonographic variables (anterior condylar translation, tongue thickness, hyomental distance and oral cavity height) associated with difficult direct laryngoscopy ([Cormack Lehane (CL) grade>2]) were analysed. The primary outcome was to determine the efficacy of the above-mentioned sonographic measures as predictors of difficult laryngoscopy (CL grade >2). The secondary outcome compared ultrasonographic predictors with clinical predictors in morbidly obese patients for determining difficult direct laryngoscopy.

Results

Amongst the primary outcome measures, limited condylar mobility (anterior condylar translation <9.25 mm) [odds ratio (OR) 0.3, confidence interval (CI):1.04-1.22;P<0.001;area under curve (AUC):0.8] and increased tongue thickness >5.85 cm [OR: 3.2, CI: 1.05-10; P < 0.04; AUC: 0.73] were two independent sonographic predictors for difficult direct laryngoscopy by multivariate logistic regression and receiver operating characteristic curve analyses in morbidly obese patients. The secondary outcome suggested that as compared to clinical predictors such as Mallampati grade and thyromental distance, ultrasonographic variables such as tongue thickness and limited condylar mobility (sensitivity: 56.4%, 70.9%, 66.7% and 93.3%, respectively) better predicted difficult direct laryngoscopy in morbidly obese patients.

Conclusion

Limited condylar mobility and increased tongue thickness are independent sonographic predictors of difficult direct laryngoscopy in morbidly obese patients.

Ultrasonography indicators for predicting difficult intubation: a systematic review and meta-analysis

Background

Ultrasonography (US) is recently used frequently as a tool for airway assessment prior to intubation (endotracheal tube (ETT) placement), and several indicators have been proposed in studies with different reported performances in this regard. This systematic review and meta-analysis reviewed the performance of US in difficult airway assessment.

Methods

This systematic review and meta-analysis was conducted according to the guideline of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and the Cochrane book. All the studies that had carried out difficult airway assessments using US, had compared the indicators in difficult and easy groups, and had published the results in English by the time we conducted our search in April 28, 2020, were included.

Results

In the initial search, 17,156 articles were retrieved. After deleting the duplicate articles retrieved from multiple databases, 7578 articles remained for screening based on the abstracts and titles. Finally, the full text of 371 articles were assessed and the data from 26 articles were extracted, which had examined a total of 45 US indicators for predicting difficult intubation. The most common US index was the “thickness of anterior neck soft tissue at the vocal cords level”. Also, “skin to epiglottis” and “anterior neck soft tissue at the hyoid bone level” were among the most common indicators examined in this area.

Conclusion

This systematic review showed that US can be used for predicting difficult airway. Of note, “skin thickness at the epiglottis and hyoid levels”, “the hyomental distance”, and “the hyomental distance ratio” were correlated with difficult laryngoscopy in the meta-analysis. Many other indicators, including some ratios, have also been proposed for accurately predicting difficult intubation, although there have been no external validation studies on them.

Study comparing different airway assessment tests in predicting difficult laryngoscopy: A prospective study in geriatric patients

Background and Aims

Limited studies are available comparing diagnostic accuracy of various airway predictors in geriatric patients. We conducted this study with primary aim to evaluate and validate the predictive value of 'standard airway predictors' like modified Mallampati test, thyromental distance (TMD), sternomental distance, neck movement (NM), mouth opening (MO), dentition and 'new airway predictors' like upper lip bite test (ULBT), ratio of height to thyromental distance and thyromental height test (TMHT) for predicting difficult laryngoscopy in geriatric patients.

Methods

This prospective, observational study was conducted on 140 patients above 65 years of age of either sex, scheduled for elective surgery under general anaesthesia requiring endotracheal intubation. The age, weight, height, body mass index (BMI) and airway parameters were recorded. The laryngoscopic view was assessed by modified Cormack-Lehane scale. Standard formulae were used to calculate validity indexes.

Results

The incidence of difficult larygoscopy found in our study was 25%. The mean age of our study population was 69.37 ± 4.23 years. TMD exhibited the highest sensitivity (80%) and negative predictive value (NPV) (91.86%) as compared to other studied airway predictors. The positive predictive value (PPV) of ULBT was 100%. Moreover, ULBT exhibited highest accuracy (82.14%) and odds ratio (86.88) and high specificity (91.30%) for predicting difficult laryngoscopy in geriatric patients. NM and TMHT also exhibited high accuracy (77.85%, 77.14%) and PPV (59.09%, 52.94%).

Conclusions

TMD and ULBT both showed good predictive value in diagnosing difficult laryngoscopy in geriatric patients. Furthermore, NM and TMHT also exhibited higher diagnostic accuracy in predicting difficult airway in these patients.

Focus on PoCUS or hocus pocus? Integrating point-of-care ultrasound into residency and clinical practice

Point-of care ultrasound (PoCUS) is a new clinical diagnostic paradigm that plays an instrumental role in the ongoing anesthesiologist’s evolving role towards a perioperative physician. Currently, there are few approved curricula that incorporate a PoCUS program into anesthesia residency. This article examines relevant PoCUS applications for anesthesiologists, presents an overview of existing international guidelines for education and training, and reflects on the need for specialty-wide standards. We present a possible framework, that could offer a first move towards a structured PoCUS pathway for Belgian anesthesia residents and facilitate its incorporation into national anesthesia practice.

Point-of-care ultrasound in the preoperative setting

Point-of-care ultrasound (POCUS) is a widely used diagnostic tool, especially in emergency and critical care medicine, and it is increasingly being used in the perioperative setting. Its specific role in preoperative assessment of patients, however, has not yet been defined. While some data show innovative use of the technique in the preoperative setting, higher-level evidence to underscore potential advantages is still limited. We review and discuss a range of POCUS examinations which can potentially help anaesthesiologists in the preoperative clinic decide whether to perform additional testing, can assist in selecting the best anaesthetic approach, and can support perioperative and postoperative monitoring.

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

Purpose: To describe the correlation between clinically measured hyomental distance ratio (HMDR_clin) and the ultrasound measurement (HMDR_echo) in patients with and without morbid obesity and to compare their diagnostic accuracy for difficult airway prediction. Methods: HMDR_clin and HMDR_echo were recorded the day before surgery in 160 consecutive consenting patients. Laryngoscopy was performed by a skilled anesthesiologist, with grades III and IV Cormack–Lehane being considered difficult views of the glottis. Linear regression was used to assess the correlation between HMDR_clin and HDMR_echo and receiver operating curve analysis was used to compare the performance of the two for predicting difficult airway. Results: The linear correlation between HMDR_clin and HDMR_echo in patients without morbid obesity had a Pearson coefficient of 0.494, while for patients with morbid obesity this was 0.14. A slightly higher area under the curve for HMDR_echo was oberved: 0.64 (5%CI 0.56–0.71) versus 0.52 (95%CI, 0.44–0.60) (p = 0.34). Conclusion: The association between HMDR_clin and HDMR_echo is moderate in patients without morbid obesity, but negligible in morbidly obese patients. These might be explained by difficulties in palpating anatomical structures of the airway.