Comparison of the Macintosh, King Vision®, Glidescope® and AirTraq® Laryngoscopes in Routine Airway Management
Condition: Patients Need Tracheal Intubation
Study type: Interventional
Phase: Phase 1/Phase 2

Summary: 
      Failure to successfully intubate the trachea and secure the airway remains a leading cause of
      morbidity and mortality, in the operative [1-2] and emergency settings. [3-4]. When the
      concept of endotracheal intubation was developed, 100 years ago the procedure was performed
      blindly. Shortly thereafter, laryngoscopes were invented, allowing for direct visualization
      of the larynx with a viewing angle of 15 degrees [5]. Insufficient laryngoscopic view
      constitutes the main reason for difficult intubations [6].

      Video laryngoscopes provide an improved view of the glottis, as the camera is a few
      millimeters away from the glottis. The use of Glidescope [7-8] and AirTraq [9] laryngoscopes
      has superior glottis view and ease of tracheal intubation compared with the traditional
      Macintosh laryngoscope. Unfortunately, the use video laryngoscopes is associated with longer
      time to tracheal intubation compared with the traditional techniques which be explained with
      the variable learning curves of the practitioners. [10]

      The King Vision video laryngoscope® (King Systems Company, a division of Consort Medical,
      Indianapolis, Indiana, USA) is a relative newcomer to the video laryngoscopes of devices that
      claim to provide the "perfect view" for intubation via use of video and digital technology.

      The King Vision Video laryngoscope is a two piece design. It has a reusable monitor that
      attaches to disposable blades. Blades are made of high quality poly-carbonate plastic and
      house a complementary semi-conductor (CMOS) micro camera offers a 160 degree of view and LED
      light source.

      Up to best of the authors' knowledge, there is no current published or ongoing randomized
      controlled comparative study of the use of King Vision laryngoscope with traditional
      laryngoscope and other video laryngoscopes for endotracheal intubation.
    

Detailed description: 
      Eighty six ASA I-II patients aged 18-65 years scheduled for elective minor surgery under
      general anesthesia who need tracheal intubation will be included in this prospective,
      randomized, single-blind, controlled study at the author's center after obtaining approval of
      the local ethical committee and an informed written consent from all participants.

      Patients will be randomly allocated to one of four groups (n=30 for each) namely, Macintosh,
      King Vision, Glidescope, or AirTraq groups, by drawing sequentially numbered sealed opaque
      envelopes containing a software-generated randomization code (Random Allocation Software,
      version 1.0.0, Isfahan University of Medical Sciences, Isfahan, Iran).

      Anesthesia:

      The Mallampati airway score, thyromental and sternomental distances with neck extension, and
      the degree of mouth opening will be evaluated preoperatively as factors predicting difficult
      intubation. Patients' monitoring includes pulse oximetry, noninvasive blood pressure
      electrocardiography, state and response Entropy (SE and RE) and train of four (TOF) before
      induction of anesthesia.

      The intubators who will participate in the study received a standardized manikin based
      training course followed by 10 successful intubations in clinical practice with the use of
      Macintosh, King Vision®, Glidescope®, and the Airtraq® laryngoscopes for endotracheal
      intubation.

      Anesthetic technique will be standardized in all studied. After breathing 100% oxygen for 3
      min through a facemask in a supine "sniffing" position, all patients will receive intravenous
      propofol 2-3 mg/kg and remifentanail 0.05-0.25 µg/kg/min for induction of anesthesia until
      loss of consciousness defined as decrease of SE less than 50 and the difference between RE
      and SE is less than 10. Rocrunium 0.6 mg.kg will be administered and complete relaxation will
      be monitored using a nerve stimulator (TOF-GE, Datex-Ohmeda Division, Instrumentarium
      Corporation, Helsinki, Finland).

      The studied data during intubation will be collected by an independent investigator; the
      intubator will not informed about the time taken to achieve any intubations. Tracheal
      intubation will be performed with the Macintosh, King Vision, Glidescope, or AirTraq
      laryngoscopes, according to the assigned randomization code.

      Time to tracheal intubation, defined as the time when the investigated laryngoscope passes
      the central incisors to the time when the tip of the tracheal tube passed through the
      glottis, will be determined. The duration of laryngoscopy, defined as the time from holding
      of the investigated laryngoscope to the appearance of as the first upward deflection on the
      capnograph, will be recorded.

      Before each procedure, the capnograph gas sample delay time will be measured and then
      subtracted from total recorded duration of laryngoscopy, to correct for the different
      sampling times between the capnographs used. [11] The best view during laryngoscopy (using
      Cormack and Lehane classification) will be recorded. [12]

      If intubation is unsuccessful at the first attempt, took longer than 120 seconds, or if
      desaturation noted on the pulse oximeter (defined as SpO2 < 92%) [13], the intubation attempt
      will be stopped and the lungs will be ventilated with an oxygen-volatile anesthetic mixture
      for 3 min. A second attempt will be allowed with the randomly allocated airway device. If
      intubation is unsuccessful after two attempts, the protocol allows intubating the patient
      with the anesthesiologist's instrument of choice. [14]

      The anesthesiologist will be asked to rate the ease of intubation using a 10 cm visual analog
      scale (0 for much of ease and 10 for extremely difficult). Hemodynamic parameters (heart
      rate, systolic and mean blood pressures) will be recorded at baseline, during the intubation
      process, and each 1-min for 5 min and 10 min after tracheal intubation.

      A careful examination of the oropharynx will be performed after intubation to determine any
      lip, dental or mucosal trauma. Following recovery from anesthesia in the post-anesthesia care
      unit, a trained anesthesiologist who will not be involved in the study and who is blind to
      the device used will evaluate all patients for a postoperative sore throat to ensure
      consistency and severity.

      Statistical Analysis

      Data will be tested for normality using the Kolmogorov-Smirnov test. Serial changes in the
      studied data at intubation will be analyzed with repeated-measures analysis of variance.
      Categorical data will be analyzed using Fischer's exact test. Repeated measure analysis of
      variance (ANOVA) will be used for continuous parametric variables and the differences will be
      then corrected by post-hoc Bonferoni test. The Kruskal-Wallis one-way ANOVA will be performed
      for intergroup comparisons for the non-parametric values and post hoc pairwise comparisons
      will be done using the Wilcoxon rank sum t test. p value < 0.05 will be considered
      statistically significant.
    

Intervention name(s): Macintosh; King Vision; Glidescope; AirTraq
Intervention type(s): Device; Device; Device; Device
Intervention description(s): Laryngeal exposure and tracheal intubation using that device; Laryngeal exposure and tracheal intubation using that device; Laryngeal exposure and tracheal intubation using that device; Laryngeal exposure and tracheal intubation using that device
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Prevention
Keywords: Laryngoscope; Macintosh; Glidescope; King Vision; AirTraq; tracheal intubation