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

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

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.

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