Ultrasound Measurement of Skin-to-Epiglottis Distance for Prediction of Difficult Airway in Adult Patients

Airway management is a critical component of anesthesia and intensive care practice. Predicting difficult airway remains challenging with conventional bedside tests. Ultrasound has emerged as a non-invasive, bedside tool for airway assessment. This study aims to investigate the relationship between skin-to-epiglottis distance measured by ultrasound and difficult laryngoscopy/intubation. Secondary comparisons will include traditional airway assessment methods such as Mallampati score, thyromental distance, and neck circumference

Primary outcomes

• Skin to epiglottis distance [Preintubation (within 30 minutes before procedure)]: Distance measured via ultrasound in the anterior neck region

Secondary outcomes

• Incidence of difficult laryngoscopy (Cormack-Lehane grade ≥ 3) [During intubation procedure (intraoperative period)]: The proportion of patients with difficult laryngoscopy defined as Cormack-Lehane grade 3 or 4 during direct laryngoscopy.
• Intubation Difficulty Score (IDS) [During intubation procedure]: Assessment of intubation difficulty using the Intubation Difficulty Score based on number of attempts, operators, alternative techniques, glottic exposure, lifting force, external laryngeal pressure, and vocal cord position.
• Correlation between ultrasound measurements and Mallampati score [Preoperative assessment]: Correlation between tracheal diameter and skin to epiglottis distance measured by ultrasound and preoperative Mallampati classification.
• Skin-to-Epiglottis Distance Measured by Ultrasound [Immediately before induction of anesthesia]: Skin-to-epiglottis distance will be measured using ultrasound immediately before anesthesia induction. The distance is recorded in millimeters (mm) as a continuous variable. Larger values indicate a greater skin-to-epiglottis distance and may be associated with an increased likelihood of difficult laryngoscopy. This is not a scored scale; therefore, no predefined minimum or maximum score exists.Cormack-Lehane Grading System. Scores range from Grade I to Grade IV. Grade I indicates full visualization of the glottis (easier laryngoscopy), whereas Grade IV indicates that neither the glottis nor the epiglottis is visible (most difficult laryngoscopy). Higher grades indicate a worse airway view.

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* ≥18 yaş elective surgery

Exclusion Criteria:

* emergency surgery
* head and neck surgery
* pregnant patients

• Gani, E. (2020). Obez hastalarda zor entübasyonun öngörülmesinde ultrasonla ölçülen cilt-epiglot mesafesinin önemi (Tıpta Uzmanlık Tezi). Düzce Üniversitesi, Tıp Fakültesi, Anesteziyoloji ve Reanimasyon Anabilim Dalı, Düzce.
• Uzumcugil F, Celebioglu EC, Ozkaragoz DB, Yilbas AA, Akca B, Lotfinagsh N, Celebioglu B. Body Surface Area Is Not a Reliable Predictor of Tracheal Tube Size in Children. Clin Exp Otorhinolaryngol. 2018 Dec;11(4):301-308. doi: 10.21053/ceo.2018.00178. Epub 2018 Aug 25. PMID 30139232
• Ahmad I, El-Boghdadly K, Iliff H, Dua G, Higgs A, Huntington M, Mir F, Nouraei SAR, O'Sullivan EP, Patel A, Rivett K, McNarry AF. Difficult Airway Society 2025 guidelines for management of unanticipated difficult tracheal intubation in adults. Br J Anaesth. 2026 Jan;136(1):283-307. doi: 10.1016/j.bja.2025.10.006. Epub 2025 Nov 7. PMID 41203471
• Altinsoy KE, Bayhan BU. Ultrasound-Measured Skin-to-Epiglottis Distance as a Predictor of Difficult Intubation in Obese Patients: A Prospective Observational Study. J Clin Med. 2025 Mar 19;14(6):2092. doi: 10.3390/jcm14062092. PMID 40142901
• Sayir TN, Tuncer B, Erkilic E. Evaluation of upper airway ultrasonographic measurements in predicting difficult intubation: A cross-section of the Turkish population. Open Med (Wars). 2024 Aug 21;19(1):20241013. doi: 10.1515/med-2024-1013. eCollection 2024. PMID 39176250
• Cinar Kose EO, Tekin M, Cesur S, Cam I, Baykara ZN. Evaluation of neck ultrasound measurements as a difficult airway predictor: A prospective observational study. Medicine (Baltimore). 2024 Jul 19;103(29):e38591. doi: 10.1097/MD.0000000000038591. PMID 39029084
• Daggupati H, Maurya I, Singh RD, Ravishankar M. Development of a scoring system for predicting difficult intubation using ultrasonography. Indian J Anaesth. 2020 Mar;64(3):187-192. doi: 10.4103/ija.IJA_702_19. Epub 2020 Mar 11. PMID 32346164
• Sotoodehnia M, Rafiemanesh H, Mirfazaelian H, Safaie A, Baratloo A. Ultrasonography indicators for predicting difficult intubation: a systematic review and meta-analysis. BMC Emerg Med. 2021 Jul 3;21(1):76. doi: 10.1186/s12873-021-00472-w. PMID 34217221
• Cook TM, Woodall N, Frerk C; Fourth National Audit Project. Major complications of airway management in the UK: results of the Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society. Part 1: anaesthesia. Br J Anaesth. 2011 May;106(5):617-31. doi: 10.1093/bja/aer058. Epub 2011 Mar 29. PMID 21447488
• Zhang W, Du L, Huang Y, Liu D, Li T, Zheng J. Artificial intelligence for difficult airway assessment: a protocol for a systematic review with meta-analysis. BMJ Open. 2025 Jun 10;15(6):e096744. doi: 10.1136/bmjopen-2024-096744. PMID 40499971
• Falcetta S, Cavallo S, Gabbanelli V, Pelaia P, Sorbello M, Zdravkovic I, Donati A. Evaluation of two neck ultrasound measurements as predictors of difficult direct laryngoscopy: A prospective observational study. Eur J Anaesthesiol. 2018 Aug;35(8):605-612. doi: 10.1097/EJA.0000000000000832. PMID 29889671

• Almıla g Pamuk, Doç Dr., Study director, Hacettepe Univercity