Anesthesia Intubation ComplicationNCT07366177
Can the "Face Index"; an Anthropometric Measurement, Predict Difficult Laryngoscopy and Intubation?
An observational study of Anesthesia Intubation Complication and Laryngoscopy, run by Ordu University.
Trial summary
Patient safety is the cornerstone of anesthetic practice, and maintaining adequate respiration represents its most critical initial step. In situations where spontaneous breathing cannot be sustained-such as during general anesthesia-the airway must be mechanically secured. Read more about this study
- Who is it for?
- Ages 18 to 95 years
- Conditions the study is for
- Anesthesia Intubation Complication, Laryngoscopy, Intubation; Difficult or Failed
- What is being tested?
- Face index
- How many people
- 1,000 participants
- Where
- No sites listed yet
- Study dates
- Nov 2026to Nov 2027
- Phase
- Observational
- 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 95 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Study population: All patients who have general anesthesia
Who may be able to join
- Adult patients over the age of 18
- Patients who received general anesthesia
Who cannot join
- A prior history of difficult airway
- All patients who have undergone facial deformities
- All patients who have tracheostomy
- 5. Children patients 6. Pregnant patients
Trial locations and contacts
No sites are listed yet. Contact the study team or a site near you to ask about taking part.
About this study
Patient safety is the cornerstone of anesthetic practice, and maintaining adequate respiration represents its most critical initial step. In situations where spontaneous breathing cannot be sustained-such as during general anesthesia-the airway must be mechanically secured. While simple face masks may be sufficient in some cases, endotracheal intubation remains the most reliable method for airway control in conditions associated with respiratory depression.
Airway management may be challenging due to various patient-related anatomical factors, including facial and mandibular structure, obesity, limited mouth opening, facial hair, sunken cheeks, wide facial morphology, and a short or muscular neck. These challenges are collectively described as difficult ventilation and difficult intubation (cannot ventilate-cannot intubate), which may occur unexpectedly or be anticipated. A difficult airway is defined as difficulty encountered by a trained anesthesiologist in face mask ventilation, tracheal intubation, or both.
Read more
Several predictors of difficult airway are widely accepted, such as thyromental and sternomental distances, neck circumference, Mallampati classification, upper lip bite test, mouth opening, and interincisor distance. Thorough preoperative airway evaluation is mandatory, as difficult mask ventilation and failed intubation remain major contributors to anesthesia-related morbidity and mortality. Although numerous studies have examined these predictors, research focusing on facial morphology and anthropometric indices-particularly the face index-is extremely limited.
Facial morphology varies considerably among individuals and can be evaluated anthropometrically using simple, noninvasive tools such as a digital caliper. Anthropometric analysis is commonly applied in forensic medicine and reconstructive surgery but has rarely been incorporated into airway assessment.
This study aims to introduce face index analysis as a novel predictor of difficult airway alongside conventional methods. By evaluating measurements such as trichion-gnathion distance, total facial index, upper facial index, and nasal index, the study investigates whether airway difficulty can be predicted using a single index value. All measurements are standard, noninvasive, and routinely performed during preoperative assessment.
Read the detailed description
Patient safety is the most critical aspect of anesthetic practice, and the first step in ensuring this safety is the maintenance of adequate respiratory function. Under anesthesia, or in any situation where spontaneous respiration cannot be sustained, the upper and lower airways must be mechanically secured. Airway control can often be achieved using simple face masks; however, in cases of general anesthesia or similar conditions associated with respiratory depression, airway management must be ensured through the more reliable method of endotracheal intubation.
During artificial ventilation, numerous physical characteristics such as facial structure, mandibular anatomy, obesity, limited mouth opening, the presence of a beard, a thin face with sunken cheeks, a wide facial structure, and a short, muscular neck may pose challenges for the anesthesiologist. These situations, defined in the medical literature as "difficult ventilation - difficult intubation" (cannot ventilate - cannot intubate), are not uncommon and may present as either anticipated or unanticipated difficult airways. A difficult airway is defined as a clinical situation in which a trained anesthesiologist experiences difficulty with face mask ventilation, tracheal intubation, or both, due to upper airway conditions (1,2).
Universally accepted predictors of difficult airway among anesthesiologists and the scientific community include physical measurements and classifications such as thyromental distance, sternomental distance, neck circumference, upper lip bite test, Mallampati classification, mandibular length, mouth opening, and interincisor distance (1,3,4). A comprehensive preoperative airway evaluation is both necessary and mandatory during the physical examination of patients scheduled for general anesthesia (5,6). One of the most common-and arguably the most significant-causes of anesthesia-related morbidity and mortality is difficult mask ventilation and failed intubation. In daily anesthetic practice, these classifications are frequently used to reduce the risk of airway difficulty and enhance patient safety, and numerous studies and theses addressing these physical examination criteria are available in the literature.
Despite the abundance of such studies, research evaluating facial morphology and anthropometric measurements-including the "face index"-is almost nonexistent. Facial morphology varies widely among individuals worldwide. It can be analyzed anthropometrically using various measurements and indices, which are currently most commonly applied in fields such as forensic medicine and aesthetic or reconstructive surgery. Anthropometric measurement is a technique that examines metrically definable body characteristics and can be performed easily using a simple measurement tool such as a digital caliper (7).
The primary aim of this study is to introduce a novel perspective on difficult airway assessment by incorporating face index analysis as an additional airway predictor alongside traditional measurement methods that have long been used in anesthesiology. Specifically, the study seeks to determine whether airway difficulty can be predicted using a single index value rather than multiple measurements in patients with different facial morphologies.
Airway management involves sequential steps, beginning with ventilation via a face mask, followed by visualization of the vocal cords (laryngeal inlet and vocal folds) using laryngoscopy, and finally placement of an endotracheal tube into the trachea. Facial measurements may identify physical factors that contribute to difficulty at any of these stages. This study primarily investigates the predictive value of conventional difficult airway assessments in comparison with components of the face index, including trichion-gnathion length (Tri-Gn), total facial index, upper facial index, and nasal index, in determining airway management difficulty.
All measurements employed in this study are standard, noninvasive, and harmless physical examination methods routinely used by anesthesiologists worldwide and are mandatory components of preoperative assessment.
- Conditions
- Anesthesia Intubation Complication, Laryngoscopy, Intubation; Difficult or Failed, Anesthesia Morbidity
- Being tested
- Face index
- Keywords
- Difficult airway, face index, anesthesia
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Face indexOther
Face index is an anthropometric measurement
What is being measured
The primary outcome is the main question the study is designed to answer.
1. The facial index: Unit of Measure: Ratio (dimensionless) 2. Upper Face Height: Unit of Measure: mm 3. Total Face Height: Unit of Measure: mm 4. Mallampati: Categorical (Class I-IV) 5. Difficult Airway: Categorical (yes / no)
- The facial index in will be calculated as the ratio of total face height (nasion-gnathion) to bizygomatic width measured preoperatively.
- Upper Face Height: Linear distance between subnasale and stomion measured preoperatively.
- Total Face Height: Linear distance between nasion and gnathion measured preoperatively.
- Mallampati Categorical (Class I-IV): Airway classification assessed preoperatively.
- Difficult Airway: Categorical (yes / no): Defined as the presence of difficult mask ventilation and/or difficult intubation.
Measured: Preoperative period (before induction of anesthesia)
Face index and face mask ventilation
Facial Anthropometric Measurements: Facial anthropometric measurements, including trichion-gnathion distance, upper face height (subnasale-stomion), total face height (nasion-gnathion), bizygomatic width, and alar width, measured preoperatively and recorded for each participant.
Measured: Preoperative period (before induction of anesthesia)
Secondary outcomes (1)
Facial Index and Preoperative Airway Assessment Parameters
Facial index values and preoperative airway assessment parameters, including Mallampati classification, thyromental distance, sternomental distance, mandible length, interincisor gap, Upper Lip Bite Test, and atlanto-occipital joint angle, measured preoperatively and recorded for each participant prior to intubation.
Measured: Preoperative period (before 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 posted26 Jan 2026
- Study startNov 2026 (estimated)
- Primary completionNov 2027 (estimated)
- Study completionNov 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (6)Papers the sponsor has linked to this study.
- Other trials for Anesthesia Intubation ComplicationStudies of the same condition, open and under way.
- 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
- Observational
- Observational model
- Cohort
- Time perspective
- Prospective
- Enrolment
- 1,000 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Ordu University
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Nilay Tas, Ordu University
- Investigators
- Nilay Taş, Prof. Dr., Principal investigator, Ordu University School of Medicine, Türkiye
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07366177
- Sponsor's protocol ID
- NTasFACE
- Status last verified
- Aug 2026
- First submitted
- 18 Jan 2026
- Last updated
- 24 Aug 2026
- Results posted
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Publications
Apfelbaum JL, Hagberg CA, Connis RT, Abdelmalak BB, Agarkar M, Dutton RP, Fiadjoe JE, Greif R, Klock PA, Mercier D, Myatra SN, O'Sullivan EP, Rosenblatt WH, Sorbello M, Tung A. 2022 American Society of Anesthesiologists Practice Guidelines for Management of the Difficult Airway. Anesthesiology. 2022 Jan 1;136(1):31-81. doi: 10.1097/ALN.0000000000004002.
PubMed 34762729Coskun A, Duzgun SA, Bozer M, Akinci OF, Uzunkoy A. Modified technique for correction of gynaecomastia. Eur J Surg. 2001 Nov;167(11):822-4. doi: 10.1080/11024150152717643.
PubMed 11848235Jackson JS, Rondeau B. Mallampati Score. 2025 Jul 7. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan-. Available from http://www.ncbi.nlm.nih.gov/books/NBK585119/
PubMed 36256766Chow HH, Tolle KM, Roe DJ, Elsberry V, Chen H. Application of neural networks to population pharmacokinetic data analysis. J Pharm Sci. 1997 Jul;86(7):840-5. doi: 10.1021/js9604016.
PubMed 9232526Garber DA, Beverley SM, Coen DM. Demonstration of circularization of herpes simplex virus DNA following infection using pulsed field gel electrophoresis. Virology. 1993 Nov;197(1):459-62. doi: 10.1006/viro.1993.1612.
PubMed 8212585Vidon N, Palma R, Bernier JJ. [Water-electrolyte movements along the human intestine in diarrhea induced by mannitol]. Gastroenterol Clin Biol. 1983 Jan;7(1):23-9. No abstract available. French.
PubMed 6404686
Study at a glance
From the registry record, last updated by the sponsor on 24 Aug 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Can the "Face Index"; an Anthropometric Measurement, Predict Difficult Laryngoscopy and Intubation?
- ClinicalTrials.gov ID
- NCT07366177
- Acronym / sponsor ID
- NTasFACE
- Conditions
- Anesthesia Intubation Complication, Laryngoscopy, Intubation; Difficult or Failed, Anesthesia Morbidity
- Keywords
- Difficult airway, face index, anesthesia
- Study type
- Observational
- Recruitment status
- Not yet recruiting
- Enrolment
- 1,000 participants (estimated)
- Lead sponsor
- Ordu UniversityUniversity, hospital or other
- Study start
- Nov 2026 (estimated)
- Primary completion
- Nov 2027 (estimated)
- Study completion
- Nov 2027 (estimated)
- First posted
- 26 Jan 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.
Patient safety is the cornerstone of anesthetic practice, and maintaining adequate respiration represents its most critical initial step. In situations where spontaneous breathing cannot be sustained-such as during general anesthesia-the airway must be mechanically secured. While simple face masks may be sufficient in some cases, endotracheal intubation remains the most reliable method for airway control in conditions associated with respiratory depression.
Airway management may be challenging due to various patient-related anatomical factors, including facial and mandibular structure, obesity, limited mouth opening, facial hair, sunken cheeks, wide facial morphology, and a short or muscular neck. These challenges are collectively described as difficult ventilation and difficult intubation (cannot ventilate-cannot intubate), which may occur unexpectedly or be anticipated. A difficult airway is defined as difficulty encountered by a trained anesthesiologist in face mask ventilation, tracheal intubation, or both.
Several predictors of difficult airway are widely accepted, such as thyromental and sternomental distances, neck circumference, Mallampati classification, upper lip bite test, mouth opening, and interincisor distance. Thorough preoperative airway evaluation is mandatory, as difficult mask ventilation and failed intubation remain major contributors to anesthesia-related morbidity and mortality. Although numerous studies have examined these predictors, research focusing on facial morphology and anthropometric indices-particularly the face index-is extremely limited.
Facial morphology varies considerably among individuals and can be evaluated anthropometrically using simple, noninvasive tools such as a digital caliper. Anthropometric analysis is commonly applied in forensic medicine and reconstructive surgery but has rarely been incorporated into airway assessment.
This study aims to introduce face index analysis as a novel predictor of difficult airway alongside conventional methods. By evaluating measurements such as trichion-gnathion distance, total facial index, upper facial index, and nasal index, the study investigates whether airway difficulty can be predicted using a single index value. All measurements are standard, noninvasive, and routinely performed during preoperative assessment.
Detailed description
Patient safety is the most critical aspect of anesthetic practice, and the first step in ensuring this safety is the maintenance of adequate respiratory function. Under anesthesia, or in any situation where spontaneous respiration cannot be sustained, the upper and lower airways must be mechanically secured. Airway control can often be achieved using simple face masks; however, in cases of general anesthesia or similar conditions associated with respiratory depression, airway management must be ensured through the more reliable method of endotracheal intubation.
During artificial ventilation, numerous physical characteristics such as facial structure, mandibular anatomy, obesity, limited mouth opening, the presence of a beard, a thin face with sunken cheeks, a wide facial structure, and a short, muscular neck may pose challenges for the anesthesiologist. These situations, defined in the medical literature as "difficult ventilation - difficult intubation" (cannot ventilate - cannot intubate), are not uncommon and may present as either anticipated or unanticipated difficult airways. A difficult airway is defined as a clinical situation in which a trained anesthesiologist experiences difficulty with face mask ventilation, tracheal intubation, or both, due to upper airway conditions (1,2).
Universally accepted predictors of difficult airway among anesthesiologists and the scientific community include physical measurements and classifications such as thyromental distance, sternomental distance, neck circumference, upper lip bite test, Mallampati classification, mandibular length, mouth opening, and interincisor distance (1,3,4). A comprehensive preoperative airway evaluation is both necessary and mandatory during the physical examination of patients scheduled for general anesthesia (5,6). One of the most common-and arguably the most significant-causes of anesthesia-related morbidity and mortality is difficult mask ventilation and failed intubation. In daily anesthetic practice, these classifications are frequently used to reduce the risk of airway difficulty and enhance patient safety, and numerous studies and theses addressing these physical examination criteria are available in the literature.
Despite the abundance of such studies, research evaluating facial morphology and anthropometric measurements-including the "face index"-is almost nonexistent. Facial morphology varies widely among individuals worldwide. It can be analyzed anthropometrically using various measurements and indices, which are currently most commonly applied in fields such as forensic medicine and aesthetic or reconstructive surgery. Anthropometric measurement is a technique that examines metrically definable body characteristics and can be performed easily using a simple measurement tool such as a digital caliper (7).
The primary aim of this study is to introduce a novel perspective on difficult airway assessment by incorporating face index analysis as an additional airway predictor alongside traditional measurement methods that have long been used in anesthesiology. Specifically, the study seeks to determine whether airway difficulty can be predicted using a single index value rather than multiple measurements in patients with different facial morphologies.
Airway management involves sequential steps, beginning with ventilation via a face mask, followed by visualization of the vocal cords (laryngeal inlet and vocal folds) using laryngoscopy, and finally placement of an endotracheal tube into the trachea. Facial measurements may identify physical factors that contribute to difficulty at any of these stages. This study primarily investigates the predictive value of conventional difficult airway assessments in comparison with components of the face index, including trichion-gnathion length (Tri-Gn), total facial index, upper facial index, and nasal index, in determining airway management difficulty.
All measurements employed in this study are standard, noninvasive, and harmless physical examination methods routinely used by anesthesiologists worldwide and are mandatory components of preoperative assessment.
Study design
- Observational model
- Cohort
- Time perspective
- Prospective
Who may qualify
- Ages
- 18 to 95 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
- Study population
- All patients who have general anesthesia
Key inclusion criteria (2 listed)
- Adult patients over the age of 18
- Patients who received general anesthesia
Key exclusion criteria (4 listed)
- A prior history of difficult airway
- All patients who have undergone facial deformities
- All patients who have tracheostomy
- 5. Children patients 6. Pregnant patients
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 |
|---|---|---|
| Face indexFace index is an anthropometric measurement | Other | – |
Primary outcome
1. The facial index: Unit of Measure: Ratio (dimensionless) 2. Upper Face Height: Unit of Measure: mm 3. Total Face Height: Unit of Measure: mm 4. Mallampati: Categorical (Class I-IV) 5. Difficult Airway: Categorical (yes / no)
Time frame: Preoperative period (before induction of anesthesia)
1. The facial index in will be calculated as the ratio of total face height (nasion-gnathion) to bizygomatic width measured preoperatively. 2. Upper Face Height: Linear distance between subnasale and stomion measured preoperatively. 3. Total Face Height: Linear distance between nasion and gnathion measured preoperatively. 4. Mallampati Categorical (Class I-IV): Airway classification assessed preoperatively. 5. Difficult Airway: Categorical (yes / no): Defined as the presence of difficult mask ventilation and/or difficult intubation.
Face index and face mask ventilation
Time frame: Preoperative period (before induction of anesthesia)
Facial Anthropometric Measurements: Facial anthropometric measurements, including trichion-gnathion distance, upper face height (subnasale-stomion), total face height (nasion-gnathion), bizygomatic width, and alar width, measured preoperatively and recorded for each participant.
1 secondary outcome
Facial Index and Preoperative Airway Assessment Parameters
Time frame: Preoperative period (before 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 24 Aug 2026.
- Results publication: PubMed 34762729Apfelbaum JL, Hagberg CA, Connis RT, Abdelmalak BB, Agarkar M, Dutton RP, Fiadjoe JE, Greif R, Klock PA, Mercier D, Myatra SN, O'Sullivan EP, Rosenblatt WH, Sorbello M, Tung A. 2022 American Society of Anesthesiologists Practice Guidelines for Management of the Difficult Airway. Anesthesiology. 2022 Jan 1;136(1):31-81. doi: 10.1097/ALN.0000000000004002.
- Results publication: PubMed 11848235Coskun A, Duzgun SA, Bozer M, Akinci OF, Uzunkoy A. Modified technique for correction of gynaecomastia. Eur J Surg. 2001 Nov;167(11):822-4. doi: 10.1080/11024150152717643.
- Results publication: PubMed 36256766Jackson JS, Rondeau B. Mallampati Score. 2025 Jul 7. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan-. Available from http://www.ncbi.nlm.nih.gov/books/NBK585119/
- Results publication: PubMed 9232526Chow HH, Tolle KM, Roe DJ, Elsberry V, Chen H. Application of neural networks to population pharmacokinetic data analysis. J Pharm Sci. 1997 Jul;86(7):840-5. doi: 10.1021/js9604016.
- Results publication: PubMed 8212585Garber DA, Beverley SM, Coen DM. Demonstration of circularization of herpes simplex virus DNA following infection using pulsed field gel electrophoresis. Virology. 1993 Nov;197(1):459-62. doi: 10.1006/viro.1993.1612.
- Results publication: PubMed 6404686Vidon N, Palma R, Bernier JJ. [Water-electrolyte movements along the human intestine in diarrhea induced by mannitol]. Gastroenterol Clin Biol. 1983 Jan;7(1):23-9. No abstract available. French.
- 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.
Nilay Taş, Prof. Dr. principal investigator
Ordu University School of Medicine, Türkiye
Questions about this trial
What is this clinical trial studying?
An observational study of Anesthesia Intubation Complication and Laryngoscopy, run by Ordu University.
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 2 inclusion and 4 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 24 Aug 2026. Status can change between updates, so confirm with the study contact before making plans.
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 Yasir İlyas, Ass. Prof. (+904522252344, yasirilyas@odu.edu.tr), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
1. The facial index: Unit of Measure: Ratio (dimensionless) 2. Upper Face Height: Unit of Measure: mm 3. Total Face Height: Unit of Measure: mm 4. Mallampati: Categorical (Class I-IV) 5. Difficult Airway: Categorical (yes / no) (time frame: Preoperative period (before induction of anesthesia)). The study lists 2 primary outcomes in all. 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 NCT07366177, which also lists 6 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 24 Aug 2026.