Comparing Full vs. Partial Glottis View Using CMAC D-Blade Video Laryngoscope in Simulated Cervical Injury Patient

Direct laryngoscope requires proper alignment of the oro-pharyngeal-laryngeal axis to provide an optimal glottic view for intubation. However, in cervical spine patients, this alignment is not possible thus resulting in an increased risk of fail intubations.

D-blade comes with an elliptically tapered blade shape rising at the distal end to provide better glottic visualization in comparison with direct laryngoscopes. Hence, CMAC D-blade is preferred in simulated cervical spine injury where intubator needs to maintain a neutral neck position. However, intubation time may be significantly longer due to difficulty in negotiating the endotracheal tube pass vocal cord and impingement of endotracheal tube to the anterior wall of trachea.

There is a study published Glidescope which is also a hyperangulated videolaryngoscope suggested that obtaining a partial glottic view of larynx may facilitate a faster and easier tracheal intubation when compare to a full glottis view. The aim of this study is to clinically evaluate the time of tracheal intubation in relation to the full glottic view vs. partial glottic view which is deliberately obtained when using CMAC D-blade video laryngoscopy in simulated cervical spine injury.

Direct laryngoscope requires proper alignment of the oro-pharyngeal-laryngeal axis to provide the best laryngeal view for intubation. In cervical spine patients, this alignment is not possible resulting in an increased risk of failed intubations. Difficult intubation and failed tracheal intubation are among the major causes of morbidity and mortality associated with anesthesia.

In recent years, video laryngoscope has played an increasingly important role in the management of patients with unanticipated difficult or failed endotracheal intubation. When compared with a direct laryngoscope, the video laryngoscope achieved a better view of the glottis and a high rate of successful intubation.

On comparing the C-MAC with the conventional Macintosh blade, a conventional C-MAC Macintosh blade 3 and D-blade have a blade angulation of 18° and 40° in the D-blade respectively. In addition, with D-blade is an elliptically tapered blade-shaped rising to distal.

This highly angulated C-MAC D blade provides a better glottic visualization in comparison to the direct laryngoscopes and in simulated cervical spine injury. This resulted in successful intubation in routine induction of anesthesia and rescue intubation in patients with difficult airway with C-MAC D Blade. But in terms of intubation time, study has shown a significantly shorter time with C-MAC D Blade compared with other indirect laryngoscopes. This may be due to a common problem seen in indirect video laryngoscopy whereby a good glottic view does not always allow advancing the tube into the trachea.

A study has been conducted on Glidescope which is also a hyperangulated blade suggested that obtaining a partial glottic view of larynx may facilitate a faster and easier tracheal intubation when compare to a full glottis view. Randomised controlled trial also showed that GlideScope and C-MAC D blade video laryngoscope using manual inline axial stabilization (MIAS) for tracheal intubation in patients with cervical spine injury/pathology were equally efficacious.

The aim of this study is to clinically evaluate the time of tracheal intubation in relation to deliberately obtained full glottic view vs. partial glottic view when using CMAC D-blade video laryngoscopy in simulated cervical spine injury.

Eligibility Criteria:
Inclusion Criteria:

* All patients with American Society of Anaesthesiologist (ASA) physical status I-III
* Age (≥21-75 years old)
* General anaesthesia requiring tracheal intubation
* Provide written consent to participate in the study

Exclusion Criteria:

* Pregnancy
* Body mass index (BMI) ≥ 35
* Condition requires rapid sequence induction
* Need for fibreoptic intubation
* Need for nasal intubation
* Documented difficult airway during previous surgery
* Recent (3 months) active ischemic heart disease
* Recent (3 months) cerebrovascular disease
* Acute exacerbation of respiratory disease (eg. Uncontrolled asthma, Chronic Obstructive Pulmonary Disease)