Evaluation of Functional Dimensions of Macintosh Laryngoscope Blade During Direct Laryngoscopy in Patients With Normal Mouth Opening

Condition(s) studied

Investigational drug(s) / intervention(s)

Direct Laryngoscopy: Tracheal intubation with direct laryngoscopy using Macintosh laryngoscope blade

Study summary

Direct laryngoscopy and intubation is an essential initial aspect of airway access during general anesthesia. To perform the procedure effectively, it requires adequate mouth opening, head and neck movement, and a normal temporo-mandibular joint mobility. Any issue with the above three results in a compromised upper airway at the outset and the condition is known as anticipated difficult airway, i.e. an airway that is difficult to access with conventional laryngoscopy and intubation methods. To overcome the difficulty, either one has to resort to newer advanced technique and equipment or the available conventional technique needs to be refined and modified to suit the requirement. While the former requires extraordinary expertise and finances, an option difficult to achieve in developing countries; the latter warrants focused interest to develop alternative approach with the same set of equipments.

Since submucous fibrosis and the associated restricted mouth opening have taken the proposition of an epidemic owing to widespread use of betel nut and tobacco; these patients, when requiring surgery, are difficult candidates for GA and airway control. The fact that, when they arrive as pre-surgical candidates, they have variable degree of mouth opening restriction, which if approached with a strategy, may be amenable to conventional control of airway. If investigators paint all the patients with mouth restriction as difficult airway, it will result in uncalled surgical, economic, health system and psychological burden. Therefore, it is prudent to undertake research relating to refinement of airway access techniques with the easily available, cheap and user- friendly equipment (conventional laryngoscope), such that a proportion of above stated burden can be reduced.

In view of the above, investigators plan to undertake a study to enhance our working knowledge with a conventional laryngoscope (Macintosh) to facilitate ways to control the airway difficulty secondary to mouth opening restriction. Investigators believe that the prospective knowledge thus generated would help us identify whether there is a feasibility of conventional airway management or an alternative advanced access technique is needed in the first place. This will prevent undue cancellations, delayed surgeries, and patient morbidity.

Eligibility

Primary outcome measure(s)

• Macintosh Blade Length Measurement (in centimeters) — 0 to 5-minutes
  Length of Macintosh blade size 3 and 4 as such (static) and during active direct laryngoscopy (active).
• Macintosh Blade Width Measurement (in centimeters) — 0 to 5-minutes
  Width of Macintosh blade size 3 and 4 as such (static) and during active direct laryngoscopy (active).
• Inter-incisor Angle on Macintosh Blade Contact Point (in degrees) — 0 to 5-minutes
  The angle formed by the line between the two contact points, viz. a point formed by upper incisor contact of upper flange curve (convex) of the Macintosh laryngoscope blade, and a point of contact between the lower incisor contact with lower flange curve (concave curve) of the Macintosh laryngoscope blade. The line formed by joining these two contact points with the baseline of the laryngoscope will form an angle. This angle will be noted as functional separation of eugnathic, retrognathic or prognathic maxilo-mandibular orientation

Trial sites (1)

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