Anatomic Features of the Neck and Preoperative Tests as Predictive Markers of Difficult Laryngoscopy

Anatomic Features of the Neck and Preoperative Tests as Predictive Markers of Difficult Direct Laryngoscopy

In this prospective, open cohort study the diagnostic value of tests based on neck anatomy in predicting difficult laryngoscopy was assessed.

The anatomic features of the neck measured were head extension, mouth opening, upper lip bite, Mallampati class, thyromental distance, sternomental distance, ratio of height to thyromental, neck circumference, thyrosternal distance, hyomental distance at full head extension (FHE) and at neutral position (NP), ratio of neck circumference to thyromental distance and ratio of hyomental distance FHE to hyomental distance NP.

Study Overview

• Status: Completed
• Conditions: Airway Management; Predictive Value of Tests

Detailed Description

Difficult airway assessment is based on various anatomic parameters of upper airway, much of it being concentrated on oral cavity and the pharyngeal structures. The diagnostic value of tests based on neck anatomy in predicting difficult laryngoscopy was assessed in this study .

The sample consisted of adult patients scheduled to receive general anaesthesia. Anatomic features of the neck were measured pre-operatively.

The anatomic features of the neck measured were thyromental distance, sternomental distance, ratio of height to thyromental, neck circumference, thyrosternal distance, hyomental distance at full head extension (FHE) and at neutral position (NP), ratio of neck circumference to thyromental distance and ratio of hyomental distance FHE to hyomental distance NP. The commonly used predictive tests head extension, mouth opening, upper lip bite test and Mallampati class were also measured.

The laryngoscopic view was classified according to the Cormack-Lehane Grade (1-4). Difficult laryngoscopy was defined as Cormack-Lehane Grade 3 or 4. Years of experience of the anaesthesiologists were recorded, as well as the number of tries needed to intubate the patient.

The optimal cut-off points for each predictive tests were identified by using receiver operating characteristic analysis. Sensitivity, specificity and positive predictive value and negative predictive value (NPV) were calculated for each test. Multivariate analysis with logistic regression, including all variables, was used to create a predictive model. Comparisons between genders were also performed to explore possible differences in diagnostic value and cut-off points. Finally, the years of experience of the clinician and the number of tries needed to intubate the patient were compared to assess risk of bias.

• Study Type: Observational
• Enrollment (Actual): 1142

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 14 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

• Sampling Method: Non-Probability Sample

Study Population

Adult patients with BMI less than 35 kg/m2, wihthout any known neck or airway pathology, scheduled for surgical procedures under general anaesthesia with tracheal intubation were assessed for eligibility to be included in the study.

Description

Inclusion Criteria:

• Adult patients
• BMI less than 35 kg/m2
• No known neck or airway pathology
• Scheduled for surgical procedures under general anaesthesia with tracheal intubation

Exclusion Criteria:

• Age less than 18 years
• BMI higher than 35 kg/m2
• Obvious airway malformations
• Need for rapid sequence induction/intubation under cricoid pressure
• Awake intubation
• Cervical spine pathology requiring specific manipulation
• Obstetric cases

Study Plan

How is the study designed?

Design Details

• Observational Models: Cohort
• Time Perspectives: Prospective

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Difficult laryngoscopy classification using Cormack-Lehane Grade	Assessment of difficult laryngoscopy at the time of the airway management procedure. Classified as Grade I - visualization of entire laryngeal aperture, grade II - visualization of only posterior commissure of laryngeal aperture, grade III - visualization of only epiglottis, grade IV - visualization of just the soft palate.	immediate

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Thyromental distance measured in cm with a measuring tape	The distance from the mentum to the thyroid notch while the patient's neck is fully extended and the mouth closed	immediate
Sternomental distance measured in cm with a measuring tape	The distance from the suprasternal notch to the mentum while the patient's neck is fully extended and the mouth closed	immediate
Ratio of height to thyromental distance	Calculated ratio of the height in cm to the aforementioned thyromental distance	immediate
Thyrosternal distance calculated in cm	Calculated from the subtraction: sternomental (cm) minus thyromental (cm)	immediate
Neck circumference measured in cm with a measuring tape	Measurement at the level of the cricoid cartilage while the patient's neck is in neutral position	immediate
Ratio of neck circumference to thyromental distance	Calculated ratio of the neck circumference to the aforementioned thyromental distance	immediate
Hyomental distance at full head extension (FHE) measured in cm with a measuring tape	The distance from the mentum to the hyoid bone while the patient's neck is fully extended and the mouth closed	immediate
Hyomental distance at neutral position (NP) measured in cm with a measuring tape	The distance from the mentum to the hyoid bone while the patient's neck is in neutral position and the mouth closed	immediate
Ratio of hyomental distance at FHE to hyomental distance at NP	Calculated ratio of the aforementioned variables	immediate
Mallampati class	Classified as class I - soft palate, fauces, uvula, and pillars seen, class II - soft palate, fauces, and uvula seen, class III - soft palate and base of uvula seen and class IV - soft palate not visible.	immediate
Mouth opening measured in cm with a measuring tape	The distance between the upper and lower incisors with the mouth fully open	immediate
Upper lip bite test	Classified as class I - lower incisors can bite the upper lip above the vermilion line, class II - lower incisors can bite the upper lip below the vermilion line and class III - lower incisors cannot bite the upper lip.	immediate
Head extension measured in degrees with goniometer	The patient was asked to hold head erect, facing directly to the front, then asked to extend the head maximally and the examiner estimated the angle traversed by the occlusal surface of upper teeth using a goniometer.	immediate

Collaborators and Investigators

• Sponsor: National and Kapodistrian University of Athens
• Investigators: Study Director: Chryssoula Staikou, MD, PhD, Assistant Professor, National and Kapodistrian University of Athens, 1st Department of Anaesthesia, Aretaieio Hospital

Publications and helpful links

General Publications

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• Lundstrom LH. Detection of risk factors for difficult tracheal intubation. Dan Med J. 2012 Apr;59(4):B4431.
• Shiga T, Wajima Z, Inoue T, Sakamoto A. Predicting difficult intubation in apparently normal patients: a meta-analysis of bedside screening test performance. Anesthesiology. 2005 Aug;103(2):429-37. doi: 10.1097/00000542-200508000-00027.
• Frova G, Sorbello M. Algorithms for difficult airway management: a review. Minerva Anestesiol. 2009 Apr;75(4):201-9. Epub 2008 Oct 23.
• Cheney FW. The American Society of Anesthesiologists Closed Claims Project: what have we learned, how has it affected practice, and how will it affect practice in the future? Anesthesiology. 1999 Aug;91(2):552-6. doi: 10.1097/00000542-199908000-00030. No abstract available.
• Chipas A, Ellis W, Zaglaniczny K. Airway management. In: Zaglaniczny K, Nagelhout J. Nurse Anesthesia. 3rd edition. USA: Elsevier Saunders; 2004:408
• Crosby ET, Cooper RM, Douglas MJ, Doyle DJ, Hung OR, Labrecque P, Muir H, Murphy MF, Preston RP, Rose DK, Roy L. The unanticipated difficult airway with recommendations for management. Can J Anaesth. 1998 Aug;45(8):757-76. doi: 10.1007/BF03012147.
• Peterson GN, Domino KB, Caplan RA, Posner KL, Lee LA, Cheney FW. Management of the difficult airway: a closed claims analysis. Anesthesiology. 2005 Jul;103(1):33-9. doi: 10.1097/00000542-200507000-00009.
• Rucker JC, Cole D, Guerina LR, Zoran N, Chung F, Friedman Z. A prospective observational evaluation of an anatomically guided, logically formulated airway measure to predict difficult laryngoscopy. Eur J Anaesthesiol. 2012 May;29(5):213-7. doi: 10.1097/EJA.0b013e3283502168.
• Koay CK. Difficult tracheal intubation--analysis and management in 37 cases. Singapore Med J. 1998 Mar;39(3):112-4.
• Burkle CM, Walsh MT, Harrison BA, Curry TB, Rose SH. Airway management after failure to intubate by direct laryngoscopy: outcomes in a large teaching hospital. Can J Anaesth. 2005 Jun-Jul;52(6):634-40. doi: 10.1007/BF03015776.
• Cattano D, Panicucci E, Paolicchi A, Forfori F, Giunta F, Hagberg C. Risk factors assessment of the difficult airway: an italian survey of 1956 patients. Anesth Analg. 2004 Dec;99(6):1774-1779. doi: 10.1213/01.ANE.0000136772.38754.01.
• Rose DK, Cohen MM. The airway: problems and predictions in 18,500 patients. Can J Anaesth. 1994 May;41(5 Pt 1):372-83. doi: 10.1007/BF03009858.
• Turkan S, Ates Y, Cuhruk H, Tekdemir I. Should we reevaluate the variables for predicting the difficult airway in anesthesiology? Anesth Analg. 2002 May;94(5):1340-4, table of contents. doi: 10.1097/00000539-200205000-00055.
• Khan ZH, Kashfi A, Ebrahimkhani E. A comparison of the upper lip bite test (a simple new technique) with modified Mallampati classification in predicting difficulty in endotracheal intubation: a prospective blinded study. Anesth Analg. 2003 Feb;96(2):595-9, table of contents. doi: 10.1097/00000539-200302000-00053.
• Patil VU, Stehling LC, Zauder HL. Predicting the difficulty of intubation utilizing an intubation gauge. Anesthesiol Rev. 1983;10:32-3.
• Savva D. Prediction of difficult tracheal intubation. Br J Anaesth. 1994 Aug;73(2):149-53. doi: 10.1093/bja/73.2.149.
• Naguib M, Malabarey T, AlSatli RA, Al Damegh S, Samarkandi AH. Predictive models for difficult laryngoscopy and intubation. A clinical, radiologic and three-dimensional computer imaging study. Can J Anaesth. 1999 Aug;46(8):748-59. doi: 10.1007/BF03013910.
• Gupta S, Sharma R, Jain D. Airway assessment: predictors of difficult airway. Indian J Anaesth. 2005:49(4):257-62
• Schmitt HJ, Kirmse M, Radespiel-Troger M. Ratio of patient's height to thyromental distance improves prediction of difficult laryngoscopy. Anaesth Intensive Care. 2002 Dec;30(6):763-5. doi: 10.1177/0310057X0203000607.
• Huh J, Shin HY, Kim SH, Yoon TK, Kim DK. Diagnostic predictor of difficult laryngoscopy: the hyomental distance ratio. Anesth Analg. 2009 Feb;108(2):544-8. doi: 10.1213/ane.0b013e31818fc347.
• Greek Society for Airway management, Basic and Advanced Management of the Airway, 2nd edition, Athens, 2011

Study record dates

Study Major Dates

• Study Start: March 1, 2013
• Primary Completion (Actual): December 1, 2014
• Study Completion (Actual): December 1, 2014

Study Registration Dates

• First Submitted: October 29, 2016
• First Submitted That Met QC Criteria: November 3, 2016
• First Posted (Estimate): November 6, 2016

Study Record Updates

• Last Update Posted (Estimate): November 6, 2016
• Last Update Submitted That Met QC Criteria: November 3, 2016
• Last Verified: November 1, 2016

More Information

Terms related to this study

• Keywords: neck circumference; difficult laryngoscopy; sternomental distance; thyromental distance; hyomental distance; thyrosternal distance
• Other Study ID Numbers: 10634 (REGISTRY: DAIDS ES)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: No