Can the "Face Index"; an Anthropometric Measurement, Predict Difficult Laryngoscopy and Intubation?

January 18, 2026 updated by: Nilay Tas, Ordu University

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.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

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 Type

Observational

Enrollment (Estimated)

1000

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

All patients over 18 years of age who will undergo general anesthesia and intubation

Description

Inclusion Criteria:

All adult patients over the age of 18 who have given written consent to undergo elective and/or emergency surgery under general anesthesia and be intubated in the operating rooms of our hospital's main building and annex building

Exclusion Criteria:

Patients with a prior history of difficult airway/difficult intubation, those who have undergone facial, neck, or airway surgery, those with deformities or scars in the facial and neck area due to burns or injuries, those with previous or recent tracheostomy, those with facial deformities due to any cause (congenital or acquired pathologies), and those with communication problems and who are uncooperative during measurements will be excluded from the study. Children and pregnant patients will not be included.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Face index and face mask ventilation
Time Frame: 365 days
Face index is useful measurement about difficult laryngoscopy management in anesthesia
365 days

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Face index and intubation
Time Frame: 365 days
Face index is useful measurement about difficult laryngoscopy management in anesthesia
365 days

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Ordu University

Investigators

  • Principal Investigator: Nilay Taş, Prof. Dr., Ordu University School of Medicine, Türkiye

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

March 1, 2026

Primary Completion (Estimated)

September 1, 2026

Study Completion (Estimated)

March 1, 2027

Study Registration Dates

First Submitted

January 18, 2026

First Submitted That Met QC Criteria

January 18, 2026

First Posted (Actual)

January 26, 2026

Study Record Updates

Last Update Posted (Actual)

January 26, 2026

Last Update Submitted That Met QC Criteria

January 18, 2026

Last Verified

January 1, 2026

More Information

Terms related to this study

Keywords

Other Study ID Numbers

  • NTasFACE

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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