An observational study in Airway Assessment and Laryngoscopy, sponsored by Sir Ganga Ram Hospital. Recruiting at 1 site in India. Open to participants aged 18 Years to 65 Years. Per ClinicalTrials.gov, last updated 2026-06-30.
Sponsored by Sir Ganga Ram Hospital · Observational
The goal of this observational study is to evaluate thyromental distance (TMD) and mandibular triangle perpendicular length (MTPL); to know which correlates better with the incisor vallecula distance (IVD). Based on the direction and strength of the correlation measure, a multiple regression equation can then be created to first predict the IVD with external linear measure, and second, based on IVD length prediction, the appropriate laryngoscope blade size can be ascertained.
Preoperative evaluation of the upper airway is vital to the success, safety, and quality of airway access. The evaluation primarily aims to anticipate the course of direct laryngoscopy and intubation (DLI) of the trachea. While assessment of mouth opening, neck extension, and dentition forms the preliminary step of knowing whether DLI is feasible; there are certain other parameters whose evaluation facilitates understanding as to how the actual DLI will turn out. Among the secondary parameters, the linear thyromental distance (TMD) is an important measure that determines how the direct laryngoscopy aspect of conducting DLI will go - in terms of ease-of-laryngoscopy to gain the desired visual access to the view to the vocal cords. The ease of laryngoscopy involves as to how the laryngoscope blade would be able to displace tongue to one side, create forward space enhancement, and reach the vallecula at the base of the tongue; before lifting the epiglottis to view the cords. Though in use for over 4 decades, the TMD suffers from weakness, including, low sensitivity and specificity, not relating to the actual and direct teeth vallecular distance, and getting confounded by neck dimensions (thickness, length), state of dentition, and the tongue size.
The present study is built on the premise that it's the mandibular space to which the tongue is displaced at the time of DLI, the bony mandibular space is more exclusive of the confounders, and that the teeth (lower incisors) vallecular distance represent the actual distance that needs to be predicted.
The present study aims to evaluate TMD and mandibular triangle perpendicular length (MTPL); to know which correlates better with the incisor vallecula distance (IVD). Based on the direction and strength of the correlation measure, a multiple regression equation can then be created to first predict the IVD with external linear measure, and second, based on IVD length prediction, the appropriate laryngoscope blade size can be ascertained.
Sir Ganga Ram Hospital is the lead sponsor of 30 studies on the registry; 8 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Patients undergoing elective surgery under general anaesthesia
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Dental issues:
presence of artificial teeth and/or dental implants
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Correlation of thyromental distance (TMD) and mandibular triangle perpendicular length (MTPL) with incisor vallecular distance (IVD)
In all patients thyromental distance (TMD) and mandibular triangle perpendicular length (MTPL) will be measured. TMD will be measured as a straight line distance between the bony mentum (tip of the chin) and the superior thyroid notch (upper border of the thyroid cartilage). MTPL will be measured as the perpendicular of the mandibular triangle formed by joining the mental protuberence and point at angle of mandible on either side. During direct larygngosocpoy when the tip of the laryngoscope blade lies on the vallecula, the distance between the laryngoscope blade tip and the point of laryngoscope blade flange overlying the lower incisors will be measured. A correlation between TMD and MTPL with IVD if any will be established.
Time frame: From entry into preoperative area (0 minutes) to time patient is shifted to operating room ( 10-minutes)
Correlation of incisor vallecular distance (IVD), mandibular triangle perpendicular length (MTPL), and thyromental distance (TMD) with Macintosh blade (MCB) size#3 length
Macintosh blade size # 3 length will be determined by measuring the linear distance between the tip of the blade and the point where the concave surface of the blade flange joins the heel of the the laryngoscope blade. A correlation between IVD, MTPL, and TMD with Macintosh blade size # 3 length if any will be established
Time frame: From induction of anaesthesia (0 minutes) to insertion of endotracheal tube ( 10-minutes)
Cormack and Lehane score
The grade view to the glottic-opening upon direct laryngoscopy will be done using the 4-point Cormack-Lehane grading system (grade 1: entire glottic opening is seen; grade 2: anterior larynx not visualised, only posterior laryngeal aperture is seen; grade 3: only tip of epiglottis is seen; grade 4: neither glottis or epiglottis is visible, only soft palate is seen)
Time frame: From induction of anaesthesia (0 minutes) to insertion of endotracheal tube ( 10-minutes)
Plan to share: No
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Sir Ganga Ram Hospital