Measurement of Forces Applied Using a Macintosh Direct Laryngoscope Compared to GlideScope Video Laryngoscope

Study Overview
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Brief Summary
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During Anesthesia many patients require that a breathing be inserted into their windpipe. This is usually achieved using a direct laryngoscope, consisting of a retraction blade with a light near its end. When achieving a direct line-of-sight to the windpipe is difficult, more force is often applied, resulting in greater patient stress. A GlideScope video laryngoscope uses a camera and light source to see the windpipe. This enables the user to see objects that may not be in the direct line-of-sight. This likely results in less force being required, reducing patient stress. Because such stresses are often confounded by patient variables, we are comparing the forces required by the direct and video laryngoscopes on patients with at least one risk factor for difficulty, by directly measuring these with special sensors attached to the laryngoscope blades.

Official Title
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Measurement of Forces Applied Using a Macintosh Direct Laryngoscope Compared to GlideScope Video Laryngoscope in Patients With at Least One Difficult Intubation Risk Factor

Conditions
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Moderately Difficult to Intubate

Intervention / Treatment
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* Device: Intubation with GlideScope Video Laryngoscope or Macintosh Direct Laryngoscope


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: age > 18years elective surgery single lumen endotracheal intubation required signed informed consent one risk factor for a difficult laryngoscopy ( Mallampati score >3, inter-incisor gap < 3.5cm, thyromental distance < 6.5cm, sternomental distance < 12.5cm, reduced neck extension and flexion) Exclusion Criteria: lack of patient consent anesthesiologist declines to consent contraindication to neuromuscular blockade ASA 4 rapid sequence intubation previous failed intubation other method of intubation indicated eg fiberoptic intubation, awake tracheostomy symptomatic gastro-esophageal reflux cervical spine instability unstable hypertension and symptomatic coronary artery disease cerebrovascular disease or raised intracranial pressure oral/pharyngeal/laryngeal carcinoma loose teeth/poor dentition

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Macintosh Direct Laryngoscope<br>2 main forces - a 'lifting' force to elevate the structures not in the line of sight and a force exerted by the user's wrist to counterbalance the torque effect of the tongue tissues on the blade | Device: Intubation with GlideScope Video Laryngoscope or Macintosh Direct Laryngoscope<br> <br> |
| Active Comparator: GlideScope Video Laryngoscope<br>The GlideScope has a 60º angulation anteriorly at the distal portion of the blade, allowing an anterior view of the larynx. | Device: Intubation with GlideScope Video Laryngoscope or Macintosh Direct Laryngoscope<br> <br> |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Peak forces during intubation | Peak forces generated during the laryngoscopy and intubation process using both laryngoscopes. | Intraoperatively |