Airway AssessmentNCT07642206
Combined Ultrasound and Upper Lip Bite Test Assessment of Difficult Laryngoscopy in Obese Patients
A study testing Hyomental distance measured using ultrasound in neutral head position, maximum head extension and during upper lip bite test in people with Airway Assessment, run by Cairo University at 1 site in Egypt.
Trial summary
The aim of this observational study is to evaluate the accuracy of the HMDR combined with the ULBT as a predictor of difficult laryngoscopy in obese patients undergoing elective surgery under general anesthesia, regarding: Correlation of HMDR-ULBT values with Cormack-Lehane grades during laryngoscopy. Read more about this study
- Who is it for?
- Ages 18 to 65 years
- Conditions the study is for
- Airway Assessment
- What is being tested?
- Hyomental distance measured using ultrasound in neutral head position, maximum head extension and during upper lip bite test
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 134 participants
- Where
- 1 siteEgypt
- Study dates
- 1 Jul 2026to 1 Mar 2027
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 65 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Adult obese patients aged 18 to 65 years.
- Both sexes.
- American Society of Anesthesiologists (ASA) physical status II- III.
- Body Mass Index (BMI) ≥ 30 kg/m² (classified as obese).
- Scheduled for elective surgical procedures requiring general anesthesia with endotracheal intubation.
- Ability to understand and provide informed written consent.
- Cooperative and able to perform the ULBT on command.
- Normal dentition (presence of upper and lower incisors to perform ULBT accurately).
Who cannot join
- History of maxillofacial trauma, surgery, or congenital facial anomalies affecting mandibular movement or neck anatomy.
- Known or suspected difficult airway requiring awake intubation.
- Patients with limited neck mobility (e.g., cervical spine disease or immobilization).
- Temporomandibular joint disorders or restricted mandibular mobility.
- Pregnancy.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Egypt1 site
Kasr Al-Ainy Hospital, Cairo University
Cairo, Cairo Governorate
Makarious Morris Aboelkheir, MSc, +201225246321, makariousmorris0@gmail.com
Yasmin Khalid Ahmed, MD, +201095015566, dr_ykh@hotmail.com
About this study
Official title: Ultrasound-Measured Hyomental Distance Ratio Combined With the Upper Lip Bite Test as a Predictor of Difficult Laryngoscopy in Obese Patients: A Prospective Observational Study
The aim of this observational study is to evaluate the accuracy of the HMDR combined with the ULBT as a predictor of difficult laryngoscopy in obese patients undergoing elective surgery under general anesthesia, regarding:
- Correlation of HMDR-ULBT values with Cormack-Lehane grades during laryngoscopy.
- Comparison of HMDR-ULBT with standard HMDR in predicting difficult laryngoscopy.
Read the detailed description
Airway management is a cornerstone of safe anesthesia practice. Difficult laryngoscopy and intubation remain a critical challenge for anesthesiologists. The ability to predict difficult airway situations preoperatively remains crucial, particularly in high-risk populations such as obese patients. These patients have significantly higher rates of difficult mask ventilation and tracheal intubation.
Numerous bedside screening tests have been established to predict difficult laryngoscopy, including the Mallampati classification, thyromental distance, the upper lip bite test (ULBT), and hyomental distance (HMD) measurements. However, none of these tests alone possesses sufficient sensitivity or specificity, and their predictive performance in obese individuals remains variable .
The Hyomental Distance Ratio (HMDR), defined as the ratio of the hyomental distance in maximal head extension to that in the neutral position , is a dynamic parameter reflecting upper airway compliance and anatomical displacement. An HMDR value <1.2 has been associated with increased risk of difficult laryngoscopy in several studies . Traditionally, the HMDR is measured either manually with a ruler or more objectively using ultrasound.
The Upper Lip Bite Test (ULBT) is a simple, validated bedside test assessing mandibular protrusion and temporomandibular joint mobility, two key factors influencing the success of glottic visualization . The ULBT is performed in a conscious state, making it a practical tool in airway assessment.
Given that the ULBT involves active mandibular protrusion, it may mimic the anterior displacement of airway structures achieved during head extension or jaw thrust. Therefore, measuring the hyomental distance while the patient performs the ULBT could serve as a novel dynamic modification of the traditional HMDR-potentially offering a more functional and patient-cooperative measure.
Recent studies have validated the HMDR (extension/neutral) as a useful predictor of difficult laryngoscopy by ultrasound, due to its capacity to evaluate the anterior neck space and upper airway alignment . However, these studies primarily assess neck extension without incorporating mandibular movement, despite its key role in airway visualization. To date, no published studies have evaluated the hyomental distance combined with the ULBT using ultrasound or compared it with the traditional HMDR, leaving an interesting gap in the literature.
Combining the anatomical advantages of anterior neck space assessment with functional jaw mobility via the HMDR combined with the ULBT may yield a more comprehensive and accurate predictor of difficult airway, especially in obese or anatomically challenging patients. This novel approach may detect subtle impairments in upper airway dynamics not captured by the static HMDR alone. To our knowledge, this application has not yet been explored in existing literature.
This study, therefore, aims to evaluate the accuracy of the HMDR combined with the ULBT as a predictor of difficult laryngoscopy in obese patients undergoing elective surgery under general anesthesia, using difficult laryngoscopy-defined as Cormack-Lehane grade 3 or 4-as the primary outcome .
- Conditions
- Airway Assessment
- Being tested
- Hyomental distance measured using ultrasound in neutral head position, maximum head extension and during upper lip bite test
- Keywords
- airway ultrasound, upper lip bite test
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Hyomental distance measured using ultrasound in neutral head position, maximum head extension and during upper lip bite testDiagnostic test
Hyomental distance will be measured using ultrasound in three positions: neutral head position, maximum head extension, and during the upper lip bite test (ULBT).
| Study group | Role | What they receive |
|---|---|---|
| HMD measured by US in neutral head position , maximum head extension and during upper lip bite test | Other | Hyomental distance will be measured using ultrasound in three positions: neutral head position, maximum head extension, and during the upper lip bite test (ULBT). Receives: Diagnostic Test: Hyomental distance measured using ultrasound in neutral head position, maximum head extension and during upper lip bite test |
What is being measured
The primary outcome is the main question the study is designed to answer.
Prediction of difficult laryngoscopic view, defined as Cormack-Lehane Grade 3 or 4 on the first laryngoscopy attempt without external laryngeal manipulation.
Difficult laryngoscopic view is defined as Cormack-Lehane Grade III or IV during the first laryngoscopy attempt without external laryngeal manipulation
Cormack-Lehane classification for laryngoscopic view :
grade 1: most of the vocal cords is seen; grade 2: only the posterior part of the vocal cords or the arytenoid cartilages are seen; grade 3: only epiglottis is seen; grade 4: epiglottis is not seen.
Measured: Day of surgery from preoperative assessment to first laryngoscopy attempt after induction of general anethesia and after three minutes of mask ventilation.
Secondary outcomes (2)
Determination of an optimal cutoff value for HMDR-ULBT to predict difficult laryngoscopy.
Receiver operating characteristic (ROC) curve analysis will be performed to determine the optimal cutoff value of the hyomental distance ratio measured during the upper lip bite test (HMDR-ULBT) for predicting difficult laryngoscopic view, defined as Cormack-Lehane Grade III or IV on the first laryngoscopy attempt without external laryngeal manipulation. The area under the ROC curve (AUC), sensitivity, specificity, positive predictive value, and negative predictive value corresponding to the optimal cutoff value will be calculated.
Measured: From preoperative airway assessment until completion of the first laryngoscopy attempt during induction of anesthesia on the day of surgery
Comparison of HMDR-ULBT with standard HMDR in predicting difficult laryngoscopy.
The predictive performance of the hyomental distance ratio measured during the upper lip bite test (HMDR-ULBT) will be compared with that of the standard hyomental distance ratio (HMDR) for predicting difficult laryngoscopic view, defined as Cormack-Lehane Grade III or IV during the first laryngoscopy attempt without external laryngeal manipulation. Diagnostic accuracy parameters, including sensitivity, specificity, positive predictive value, negative predictive value, and area under the receiver operating characteristic (ROC) curve, will be compared between the two methods.
Measured: From preoperative airway assessment until completion of the first laryngoscopy attempt during induction of anesthesia.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted11 Jun 2026
- Study start1 Jul 2026 (estimated)
- Primary completion1 Feb 2027 (estimated)
- Study completion1 Mar 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (4)Papers the sponsor has linked to this study.
- Other trials for Airway AssessmentStudies of the same condition, open and under way.
- More trials run by Cairo UniversityThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Other
- Allocation
- Not applicable
- Intervention model
- Single group
- Model description
- Hyomental distance will be measured using ultrasound in three different positions, neutral head position , maximum head extension and during performing upper lip bite test .
- Masking
- None (open label)
- Enrolment
- 134 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Cairo University
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Makarious Morris Aboelkheir Shenouda, Cairo University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07642206
- Sponsor's protocol ID
- Airway Ultrasound
- Status last verified
- Jun 2026
- First submitted
- 7 Jun 2026
- Last updated
- 12 Jun 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Publications
Bhanushali A, Date A. Evaluation of upper lip bite test and thyromental height test for prediction of difficult laryngoscopy: A prospective observational study. Airway. 2021;4(3):621-42.
Hrithma D, K R, Mahadevaiah DT, K N V. A Cross-Sectional Study on Hyomental Distance Ratio (HMDR) as a New Predictor of Difficult Laryngoscopy in ICU Patients. Cureus. 2022 May 28;14(5):e25435. doi: 10.7759/cureus.25435. eCollection 2022 May.
PubMed 35774688Liaskou C, Vouzounerakis E, Trikoupi A, Staikou C. [Evaluation of bedside tests and proposal of a model for predicting difficult laryngoscopy: an observational prospective study]. Braz J Anesthesiol. 2020 Mar-Apr;70(2):125-133. doi: 10.1016/j.bjan.2020.02.007. Epub 2020 May 13.
PubMed 32482358Liu Y, He Y, Wang X, Li J, Zhang Z, Zhuang X, et al. Advances in airway management in recent 10 years from 2013 to 2023. Anesthesiol Perioper Sci. 2023;1(4):27-30.
Study at a glance
From the registry record, last updated by the sponsor on 12 Jun 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Ultrasound-Measured Hyomental Distance Ratio Combined With the Upper Lip Bite Test as a Predictor of Difficult Laryngoscopy in Obese Patients: A Prospective Observational Study
- ClinicalTrials.gov ID
- NCT07642206
- Acronym / sponsor ID
- Airway Ultrasound
- Conditions
- Airway Assessment
- Keywords
- airway ultrasound, upper lip bite test
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 134 participants (estimated)
- Lead sponsor
- Cairo UniversityUniversity, hospital or other
- Study start
- 1 Jul 2026 (estimated)
- Primary completion
- 1 Feb 2027 (estimated)
- Study completion
- 1 Mar 2027 (estimated)
- First posted
- 11 Jun 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The aim of this observational study is to evaluate the accuracy of the HMDR combined with the ULBT as a predictor of difficult laryngoscopy in obese patients undergoing elective surgery under general anesthesia, regarding:
- Correlation of HMDR-ULBT values with Cormack-Lehane grades during laryngoscopy.
- Comparison of HMDR-ULBT with standard HMDR in predicting difficult laryngoscopy.
Detailed description
Airway management is a cornerstone of safe anesthesia practice. Difficult laryngoscopy and intubation remain a critical challenge for anesthesiologists. The ability to predict difficult airway situations preoperatively remains crucial, particularly in high-risk populations such as obese patients. These patients have significantly higher rates of difficult mask ventilation and tracheal intubation.
Numerous bedside screening tests have been established to predict difficult laryngoscopy, including the Mallampati classification, thyromental distance, the upper lip bite test (ULBT), and hyomental distance (HMD) measurements. However, none of these tests alone possesses sufficient sensitivity or specificity, and their predictive performance in obese individuals remains variable .
The Hyomental Distance Ratio (HMDR), defined as the ratio of the hyomental distance in maximal head extension to that in the neutral position , is a dynamic parameter reflecting upper airway compliance and anatomical displacement. An HMDR value <1.2 has been associated with increased risk of difficult laryngoscopy in several studies . Traditionally, the HMDR is measured either manually with a ruler or more objectively using ultrasound.
The Upper Lip Bite Test (ULBT) is a simple, validated bedside test assessing mandibular protrusion and temporomandibular joint mobility, two key factors influencing the success of glottic visualization . The ULBT is performed in a conscious state, making it a practical tool in airway assessment.
Given that the ULBT involves active mandibular protrusion, it may mimic the anterior displacement of airway structures achieved during head extension or jaw thrust. Therefore, measuring the hyomental distance while the patient performs the ULBT could serve as a novel dynamic modification of the traditional HMDR-potentially offering a more functional and patient-cooperative measure.
Recent studies have validated the HMDR (extension/neutral) as a useful predictor of difficult laryngoscopy by ultrasound, due to its capacity to evaluate the anterior neck space and upper airway alignment . However, these studies primarily assess neck extension without incorporating mandibular movement, despite its key role in airway visualization. To date, no published studies have evaluated the hyomental distance combined with the ULBT using ultrasound or compared it with the traditional HMDR, leaving an interesting gap in the literature.
Combining the anatomical advantages of anterior neck space assessment with functional jaw mobility via the HMDR combined with the ULBT may yield a more comprehensive and accurate predictor of difficult airway, especially in obese or anatomically challenging patients. This novel approach may detect subtle impairments in upper airway dynamics not captured by the static HMDR alone. To our knowledge, this application has not yet been explored in existing literature.
This study, therefore, aims to evaluate the accuracy of the HMDR combined with the ULBT as a predictor of difficult laryngoscopy in obese patients undergoing elective surgery under general anesthesia, using difficult laryngoscopy-defined as Cormack-Lehane grade 3 or 4-as the primary outcome .
Study design
- Primary purpose
- Other
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
- Model description
- Hyomental distance will be measured using ultrasound in three different positions, neutral head position , maximum head extension and during performing upper lip bite test .
| Arm | Type | Receives |
|---|---|---|
| HMD measured by US in neutral head position , maximum head extension and during upper lip bite test | Other | Diagnostic Test: Hyomental distance measured using ultrasound in neutral head position, maximum head extension and during upper lip bite testHyomental distance will be measured using ultrasound in three positions: neutral head position, maximum head extension, and during the upper lip bite test (ULBT). |
Who may qualify
- Ages
- 18 to 65 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (8 listed)
- Adult obese patients aged 18 to 65 years.
- Both sexes.
- American Society of Anesthesiologists (ASA) physical status II- III.
- Body Mass Index (BMI) ≥ 30 kg/m² (classified as obese).
- Scheduled for elective surgical procedures requiring general anesthesia with endotracheal intubation.
Key exclusion criteria (5 listed)
- History of maxillofacial trauma, surgery, or congenital facial anomalies affecting mandibular movement or neck anatomy.
- Known or suspected difficult airway requiring awake intubation.
- Patients with limited neck mobility (e.g., cervical spine disease or immobilization).
- Temporomandibular joint disorders or restricted mandibular mobility.
- Pregnancy.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Hyomental distance measured using ultrasound in neutral head position, maximum head extension and during upper lip bite testHyomental distance will be measured using ultrasound in three positions: neutral head position, maximum head extension, and during the upper lip bite test (ULBT). | Diagnostic test | HMD measured by US in neutral head position , maximum head extension and during upper lip bite test |
Primary outcome
Prediction of difficult laryngoscopic view, defined as Cormack-Lehane Grade 3 or 4 on the first laryngoscopy attempt without external laryngeal manipulation.
Time frame: Day of surgery from preoperative assessment to first laryngoscopy attempt after induction of general anethesia and after three minutes of mask ventilation.
Difficult laryngoscopic view is defined as Cormack-Lehane Grade III or IV during the first laryngoscopy attempt without external laryngeal manipulation Cormack-Lehane classification for laryngoscopic view : grade 1: most of the vocal cords is seen; grade 2: only the posterior part of the vocal cords or the arytenoid cartilages are seen; grade 3: only epiglottis is seen; grade 4: epiglottis is not seen.
2 secondary outcomes
Determination of an optimal cutoff value for HMDR-ULBT to predict difficult laryngoscopy.
Time frame: From preoperative airway assessment until completion of the first laryngoscopy attempt during induction of anesthesia on the day of surgery
Comparison of HMDR-ULBT with standard HMDR in predicting difficult laryngoscopy.
Time frame: From preoperative airway assessment until completion of the first laryngoscopy attempt during induction of anesthesia.
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 12 Jun 2026.
- BackgroundBhanushali A, Date A. Evaluation of upper lip bite test and thyromental height test for prediction of difficult laryngoscopy: A prospective observational study. Airway. 2021;4(3):621-42.
- Background: PubMed 35774688Hrithma D, K R, Mahadevaiah DT, K N V. A Cross-Sectional Study on Hyomental Distance Ratio (HMDR) as a New Predictor of Difficult Laryngoscopy in ICU Patients. Cureus. 2022 May 28;14(5):e25435. doi: 10.7759/cureus.25435. eCollection 2022 May.
- Background: PubMed 32482358Liaskou C, Vouzounerakis E, Trikoupi A, Staikou C. [Evaluation of bedside tests and proposal of a model for predicting difficult laryngoscopy: an observational prospective study]. Braz J Anesthesiol. 2020 Mar-Apr;70(2):125-133. doi: 10.1016/j.bjan.2020.02.007. Epub 2020 May 13.
- BackgroundLiu Y, He Y, Wang X, Li J, Zhang Z, Zhuang X, et al. Advances in airway management in recent 10 years from 2013 to 2023. Anesthesiol Perioper Sci. 2023;1(4):27-30.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Hyomental distance measured using ultrasound in neutral head position, maximum head extension and during upper lip bite test in people with Airway Assessment, run by Cairo University at 1 site in Egypt.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 8 inclusion and 5 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 12 Jun 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Egypt. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Makarious Morris Aboelkheir, MSc (+201225246321, makariousmorris0@gmail.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Prediction of difficult laryngoscopic view, defined as Cormack-Lehane Grade 3 or 4 on the first laryngoscopy attempt without external laryngeal manipulation. (time frame: Day of surgery from preoperative assessment to first laryngoscopy attempt after induction of general anethesia and after three minutes of mask ventilation.). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT07642206, which also lists 4 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 12 Jun 2026.