Determination of the Cricothyroid Membrane Height by Age and Sex and Optimal Tracheal Tube Size

OBJECTIVES

The primary aim of this study was to determine the average cricothyroid membrane (CTM) height in healthy volunteers, and the secondary aim was to determine the hypothetical success rate for emergency cricothyrotomy with a tracheal tube with an 8.0 mm outer diameter.

METHODS

This study included healthy volunteers aged 18 years and older. The participants' clinical characteristics were recorded, and their CTM height was measured using ultrasound, with their necks placed sequentially in the neutral and extension positions. The relationship between the CTM height and sex, age, height, weight, body mass index, and sternomental distance was evaluated using linear regression analysis. An equation that could estimate the height of the CTM was obtained with the parameters found significant in this analysis.

RESULTS

Of the 340 participants, 208 (61.2%) were male. The mean (SD) height of the CTM in the extension position was 9.60 (1.54) mm, and it was significantly shorter in the women than in the men (8.72 [1.19] mm vs. 10.16 [1.48] mm, p < 0.001). Among the participants of short stature, the CTM was significantly shorter, regardless of sex. The hypothetical success rate for emergency cricothyrotomy was 93.3% for the males and 73.5% for the females. The equation for estimating the height of the CTM in the extension position was determined as -4.36 + 5.27 × height (m) + 0.32 × sternomental distance (cm).

CONCLUSIONS

Since the CTM height may differ according to age, sex, and height, cricothyrotomy sets should be available in various outer diameters.

LEVEL OF EVIDENCE

NA Laryngoscope, 134:1825-1830, 2024.

Point-of-care ultrasound for airway management in the emergency and critical care setting

Airway management is a common procedure within emergency and critical care medicine. Traditional techniques for predicting and managing a difficult airway each have important limitations. As the field has evolved, point-of-care ultrasound has been increasingly utilized for this application. Several measures can be used to sonographically predict a difficult airway, including skin to epiglottis, hyomental distance, and tongue thickness. Ultrasound can also be used to confirm endotracheal tube intubation and assess endotracheal tube depth. Ultrasound is superior to the landmark-based approach for locating the cricothyroid membrane, particularly in patients with difficult anatomy. Finally, we provide an algorithm for using ultrasound to manage the crashing patient on mechanical ventilation. After reading this article, readers will have an enhanced understanding of the role of ultrasound in airway management.

Spanish Society of Anesthesiology, Reanimation and Pain Therapy (SEDAR) Spanish Society of Emergency and Emergency Medicine (SEMES) and Spanish Society of Otolaryngology, Head and Neck Surgery (SEORL-CCC) Guideline for difficult airway management. Part II

The Airway Management section of the Spanish Society of Anesthesiology, Resuscitation, and Pain Therapy (SEDAR), the Spanish Society of Emergency Medicine (SEMES), and the Spanish Society of Otorhinolaryngology and Head and Neck Surgery (SEORL-CCC) present the Guide for the comprehensive management of difficult airway in adult patients. Its principles are focused on the human factor, cognitive processes for decision-making in critical situations, and optimization in the progression of strategies application to preserve adequate alveolar oxygenation in order to enhance safety and the quality of care. The document provides evidence-based recommendations, theoretical-educational tools, and implementation tools, mainly cognitive aids, applicable to airway management in the fields of anesthesiology, critical care, emergencies, and prehospital medicine. For this purpose, an extensive literature search was conducted following PRISMA-R guidelines and was analyzed using the GRADE methodology. Recommendations were formulated according to the GRADE methodology. Recommendations for sections with low-quality evidence were based on expert opinion through consensus reached via a Delphi questionnaire.

Anatomic Characteristics of the Adolescent Cricothyroid Membrane on Computed Tomography Scans

BACKGROUND

The cricothyroid membrane (CTM) is the most important anatomic structure when performing emergency front-of-neck access (FONA) procedures. Adolescence is a period of rapid morphologic change in laryngeal structures, including the CTM. We hypothesized that the adolescent CTM would be sufficiently different from pediatric or adult anatomy to merit special consideration in FONA.

OBJECTIVE

The aim of the study was to define the procedurally relevant CTM anatomy in an adolescent population.

METHODS

This was a retrospective, multicenter cohort study composed of patients who underwent a diagnostic computed tomography scan during routine clinical care. Inclusion criteria were ages 16 to 19 years and a computed tomography of the neck with or without contrast. The primary outcome was CTM height measured in the midsagittal plane using electronic calipers.

RESULTS

One hundred thirty-four imaging studies met inclusion criteria. The average CTM height was strongly associated with age and ranged between 5.4 and 6.2 mm in male adolescents and 4.6 and 5.8 mm in female adolescents. We predicted that standard cuffed endotracheal and tracheostomy tubes recommended for FONA procedures (5.0- and 6.0-mm devices) could potentially fail for most patients in our cohort.

CONCLUSIONS

The adolescent CTM is smaller than previously recognized. We recommend having a variety of equipment sizes readily available at any site where airway management in adolescents may occur.

Comparison of the Conventional Downward and Modified Upward Laryngeal Handshake Techniques to Identify the Cricothyroid Membrane: A Randomized, Comparative Study

BACKGROUND

Accurate identification of the cricothyroid membrane is crucial for successful cricothyroidotomy. The aim of this study was to compare the conventional downward and modified upward laryngeal handshake techniques in terms of accuracy to identify the cricothyroid membrane in nonobese female patients.

METHODS

In 198 anesthetized female patients, the cricothyroid membrane was identified by either the conventional downward laryngeal handshake technique (n = 99) or the modified upward laryngeal handshake technique (n = 99). According to the conventional downward laryngeal handshake technique, the cricothyroid membrane was identified by palpating the neck downward from the greater cornu of the hyoid bone, thyroid laminae, and cricoid cartilage. According to the modified upward laryngeal handshake technique, the cricothyroid membrane was located by moving up from the sternal notch. The primary outcome was the accuracy of identifying the cricothyroid membrane. Secondary outcomes included the accuracy of midline identification and time taken to locate what participants believed to be the cricothyroid membrane. The primary and secondary outcomes according to the technique were analyzed using generalized estimating equations.

RESULTS

The cricothyroid membrane could be identified more accurately by the modified upward laryngeal handshake technique than by the conventional downward technique (84% vs 56%, respectively; odds ratio [OR], 4.36; 95% confidence interval [CI], 2.13-8.93; P < .001). Identification of the midline was also more accurate by the modified laryngeal handshake than by the conventional technique (96% vs 83%, respectively; OR, 4.98; 95% CI, 1.65-15.01; P = .004). The time taken to identify the cricothyroid membrane was not different between the conventional and modified techniques (20.2 [16.2-26.6] seconds vs 19.0 [14.5-26.4] seconds, respectively; P = .83).

CONCLUSIONS

The modified upward laryngeal handshake technique that involved tracing the trachea and laryngeal structures upward from the sternal notch was more accurate in identifying the cricothyroid membrane than the conventional downward technique in anesthetized female patients.

Dimensional compatibility of currently available equipment for cricothyroidotomy and adult airway anatomy: an in vitro analysis

BACKGROUND

There are scant data on the dimensional compatibility of cricothyroidotomy equipment and related airway anatomy. We compared the dimensional design of devices for cricothyroidotomy with anatomical airway data for adult patients.

METHODS

For all available cricothyroidotomy equipment the outer diameter was recorded from manufacturer information or, if not available, measured using a sliding calliper. Outer diameters were compared with recently published mean (standard deviation [sd]) values for the height of the cricothyroid membrane obtained from computed tomography, separately for males (7.9 [2.2] mm) and for females (5.9 [1.7] mm).

RESULTS

Twenty-one cricothyroidotomy sets (10 uncuffed, 11 cuffed) with 15 differently designed devices were included. Inner diameters of the tubes ranged from 3.5 to 6.0 mm and outer diameters from 5.0 to 11.7 mm. The outer diameter of the 15 different tubes was found to be greater than the mean membrane height of the adult male cricothyroid membrane in eight devices and greater than the mean membrane height for female adults in 10 devices. Considering the lower range of cricothyroid membrane height, 12 tube outer diameters would be too large for male adults and all 15 for female adults in this range.

CONCLUSION

The outer diameter of many devices currently marketed for cricothyroidotomy are oversized for adult airway anatomy, particularly for females. For emergency front-of-neck access through the cricothyroid membrane, anatomical data suggest that cricothyroidotomy devices with outer tube diameters of <7 mm for male and <6 mm for female adult patients should be preferred.

American Society of Regional Anesthesia and Pain Medicine expert panel recommendations on point-of-care ultrasound education and training for regional anesthesiologists and pain physicians-part I: clinical indications

Point-of-care ultrasound (POCUS) is a critical skill for all regional anesthesiologists and pain physicians to help diagnose relevant complications related to routine practice and guide perioperative management. In an effort to inform the regional anesthesia and pain community as well as address a need for structured education and training, the American Society of Regional Anesthesia and Pain Medicine (ASRA) commissioned this narrative review to provide recommendations for POCUS. The guidelines were written by content and educational experts and approved by the Guidelines Committee and the Board of Directors of the ASRA. In part I of this two-part series, clinical indications for POCUS in the perioperative and chronic pain setting are described. The clinical review addresses airway ultrasound, lung ultrasound, gastric ultrasound, the focus assessment with sonography for trauma examination and focused cardiac ultrasound for the regional anesthesiologist and pain physician. It also provides foundational knowledge regarding ultrasound physics, discusses the impact of handheld devices and finally, offers insight into the role of POCUS in the pediatric population.

Canadian Airway Focus Group updated consensus-based recommendations for management of the difficult airway: part 2. Planning and implementing safe management of the patient with an anticipated difficult airway

PURPOSE

Since the last Canadian Airway Focus Group (CAFG) guidelines were published in 2013, the published airway management literature has expanded substantially. The CAFG therefore re-convened to examine this literature and update practice recommendations. This second of two articles addresses airway evaluation, decision-making, and safe implementation of an airway management strategy when difficulty is anticipated.

SOURCE

Canadian Airway Focus Group members, including anesthesia, emergency medicine, and critical care physicians were assigned topics to search. Searches were run in the Medline, EMBASE, Cochrane Central Register of Controlled Trials, and CINAHL databases. Results were presented to the group and discussed during video conferences every two weeks from April 2018 to July 2020. These CAFG recommendations are based on the best available published evidence. Where high-quality evidence is lacking, statements are based on group consensus.

FINDINGS AND KEY RECOMMENDATIONS

Prior to airway management, a documented strategy should be formulated for every patient, based on airway evaluation. Bedside examination should seek predictors of difficulty with face-mask ventilation (FMV), tracheal intubation using video- or direct laryngoscopy (VL or DL), supraglottic airway use, as well as emergency front of neck airway access. Patient physiology and contextual issues should also be assessed. Predicted difficulty should prompt careful decision-making on how most safely to proceed with airway management. Awake tracheal intubation may provide an extra margin of safety when impossible VL or DL is predicted, when difficulty is predicted with more than one mode of airway management (e.g., tracheal intubation and FMV), or when predicted difficulty coincides with significant physiologic or contextual issues. If managing the patient after the induction of general anesthesia despite predicted difficulty, team briefing should include triggers for moving from one technique to the next, expert assistance should be sourced, and required equipment should be present. Unanticipated difficulty with airway management can always occur, so the airway manager should have a strategy for difficulty occurring in every patient, and the institution must make difficult airway equipment readily available. Tracheal extubation of the at-risk patient must also be carefully planned, including assessment of the patient's tolerance for withdrawal of airway support and whether re-intubation might be difficult.

A marking of the cricothyroid membrane with extended neck returns to correct position after neck manipulation and repositioning

BACKGROUND

Emergency front of neck airway access by anaesthetists carries a high failure rate and it is recommended to identify the cricothyroid membrane before induction of anaesthesia in patients with a predicted difficult airway. We have investigated whether a marking of the cricothyroid membrane done in the extended neck position remains correct after the patient's neck has been manipulated and subsequently repositioned.

METHODS

The subject was first placed in the extended head and neck position and had the cricothyroid membrane identified and marked with 3 methods, palpation, 'laryngeal handshake' and ultrasonography and the distance from the suprasternal notch to the cricothyroid membrane was measured. The subject then moved off the table and sat on a chair and subsequently returned to the extended neck position and examinations were repeated.

RESULTS

Skin markings of all 11 subjects lay within the boundaries of the cricothyroid membrane when the subject was repositioned back to the extended neck position and the median difference between the two measurements of the distance from the suprasternal notch was 0 mm (range 0-2 mm).

CONCLUSION

The cricothyroid membrane can be identified and marked with the subject in the extended neck position. Then the patient's position can be changed as needed, for example to the 'sniffing' neck position for conventional intubation. If a front of neck airway access is required during subsequent airway management, the patient can be returned expediently to the extended-neck position, and the marking of the centre of the membrane will still be in the correct place.

The effect of patient positioning on ultrasound landmarking for cricothyrotomy

PURPOSE

Our primary objective was to assess the difference in position of the ultrasound-guided landmark of the cricothyroid membrane (CTM) when performed with the supine patient positioned at different head of bed (HOB) elevations.

METHODS

In this prospective observational study of patients presenting to the emergency department with non-life-threatening complaints, subjects underwent ultrasound-guided landmarking of the CTM with HOB elevation at 0°, 30°, and 90°. A linear mixed effects regression model was used to assess the change in the CTM landmark associated with head position. We used a second adjusted linear mixed effects model to assess possible confounding patient factors associated with these changes.

RESULTS

One-hundred and ten patients were enrolled, with a median [interquartile range] age of 39 [29-59] yr and 51:49 female:male ratio. Head of bed elevation at 30° and 90° resulted in a cephalad change in the CTM landmark of 2.7 mm (99% confidence interval [CI], 1.7 to 3.8; P < 0.001) and 4.2 mm (99% CI, 3.2 to 5.3; P < 0.001) respectively compared with the landmark at 0°. Body mass index (BMI) was associated with a change of 4.6 mm (99% CI, 0.5 to 8.7; P = 0.004) for BMI ≥ 30 compared with < 18.5 kg·m^-2 The impact of patient age on distance depended on HOB elevation, where patients > 70 yr had a change of 2.6 mm (99% CI, 0.01 to 5.1; P = 0.009) at 90° HOB elevation compared with 30°.

CONCLUSION

The location of the ultrasound-identified surface landmark of the CTM moves in a cephalad direction by changing the position of the HOB from supine 0° to elevation at 30° and 90°. This may be clinically important when attempting cricothyrotomy using a percutaneous (blind) technique, particularly when CTM identification and cricothyrotomy are performed at different head elevations.

The role of ultrasound in front-of-neck access for cricothyroid membrane identification: A systematic review

PURPOSE

Conventional palpation techniques for cricothyroid membrane (CTM) identification are inaccurate and unreliable. Ultrasound plays a multi-faceted role in airway management, however there is limited literature around its use for CTM identification prior to cricothyrotomies. This review sought to compare ultrasound to palpation in the general population, identify its indications in subjects with ill-defined neck anatomy, and determine its role in defining neck anatomy.

METHODS

Two reviewers independently assessed titles, abstracts and full-text English articles through the Ovid Medline and EMBASE databases. Studies related to ultrasound for CTM assessment and/or cricothyrotomy in subjects older than 12 years were included.

RESULTS

Fourteen studies were selected. Compared to palpation, ultrasound has greater accuracy, but longer CTM identification times in those with normal airway anatomy. Interestingly, ultrasound offers comparable times to palpation in patients with difficult airways. Ultrasound also helps define anatomical parameters in the neutral and extended neck positions thereby underscoring the importance of neck positioning during cricothyrotomies and confirming consensus-based incision recommendations set by the Difficult Airway Society.

CONCLUSION

Ultrasound appears to be superior to palpation for CTM localization especially in those with difficult airway anatomy and objectively defines neck anatomy. Its pre-emptive use should be incorporated during difficult airway management.