Comparison of Flex-It Stylet to Malleable Stylet for GlideScope Intubation: A Randomized Controlled Trial
Condition: Intubation
Study type: Interventional

Summary: 
      Patients presenting for elective surgery requiring tracheal intubation will be randomized to
      one of two different ETT stylets. The primary outcome is time to intubation.

      The null hypothesis is that there will be no difference.

      The GlideScope video laryngoscope (Verathon) is a widely used intubating device that uses a
      high-resolution camera embedded into a plastic laryngoscope blade. An LED provides
      illumination. The GlideScope often provides a good laryngoscopic view, but passing the
      endotracheal tube (ETT) through the vocal cords is sometimes difficult. Because of the 60
      degree anterior curvature of the GlideScope's blade, ETT's must have stylets inserted so that
      the ETT distal tip can be positioned anteriorly. Various authors have recommended different
      angles of the ETT to optimally place it into the trachea, including matching the GlideScope's
      60 degree angle, or configuring the ETT with a 90 degree bend. Previous studies demonstrated
      that 90 degree sharp bend was both faster and subjectively easier in a heterogeneous group of
      intubators. With the introduction of the Flex-It stylet by Parker Medical, the question
      arises as to the the best configuration of stylet for the ETT. Therefore, this prospective,
      randomized, single-blinded trial is proposed.
    

Detailed description: 
      Written informed consent will be obtained by one of the study investigators, and a copy will
      be given to each participant. Written informed consent will also be obtained from the
      operator of the GlideScope. Envelopes with computer-generated randomized group assignments
      will be present at each site. The envelopes will be consecutively numbered (i.e. "U1", "U2"
      for University Hospital, "S1", "S2" for St Joseph's Health Care, etc.). After consent,
      randomization will occur by selecting the next consecutive envelope. The envelope will
      contain the data collection form as well as a piece of paper that has the following
      information:

        -  at the top will be the randomization group (A, B) and a text description of the
           endotracheal tube angle and stylet (i.e. "90 degrees - malleable stylet")

        -  in the body of the piece of paper will be a template that shows the exact shape into
           which the tube must be bent, including where the distal and proximal ends are, the angle
           of curvature that must be followed, and the location along the length of the tube at
           which to create this angle. The angle and location will be the same for both males and
           females.

      There are three distinct anesthesia providers involved in the conduct of this study, as
      follows:

        1. "operator" - person performing the intubation

        2. "timer" - person timing the outcome (one of the co-investigators)

        3. "shaper" - person who ensures that the angle and stylet of the tube matches the group to
           which the patient was allocated

      Because the person intubating must be blind up until the time at which the tube is to be
      used, the unopened envelope will be taken to a third anesthesia provider, who will prepare
      the ETT with stylet in an area that is not visible to the person performing the intubation or
      to the person timing the intubation. The person performing the intubation will specify what
      size of tube to be prepared. This will most commonly be 7.5 mm internal diameter (ID) for a
      female and 8.0 ID for males, but the operator is free to use whatever size they feel is
      appropriate. The tube size selection will take place before unblinding so the group
      allocation cannot affect the decision of tube size.

      The tubes will all be cut at the 27 cm marking. "Group A" ETT's will be shaped with the aid
      of a standard malleable stylet (Rusch 14 Fr) that has been lubricated with single-use
      water-soluble lubricant. "Group B" ETT's will be instrumented with the Flex-It Stylet, with
      identical lubricant. The prepared tube will then be concealed under a standard green OR towel
      and brought to the operating room (OR). This tube will be placed close to the patient's head
      so that it is readily accessible.

      Data Collection

      In the OR, the GlideScope will be turned on at least 60 seconds before use so that the lens
      can warm-up to prevent fogging. The patient will be cared for in the usual fashion with
      respect to monitoring and induction of general anesthesia. To ensure adequate
      pre-oxygenation, the patient's end-tidal oxygen must be ≥ 70%. Muscle relaxation will be
      used, and the agent used is at the discretion of the operator. After induction of anesthesia,
      bag-mask ventilation will be used in the usual fashion until the operator decides to proceed
      to laryngoscopy with the GlideScope. The operator will remain blinded to the group allocation
      until after the laryngoscopic view has been obtained with the GlideScope, where upon he will
      be handed the endotracheal tube.

      The timer (who cannot see the tube under the green towel) will watch the operator until the
      GlideScope is inserted into the patient's mouth, start the timer, and then turn 180º to face
      the anesthetic monitor. The timer will not be able to see the ETT, stylet, or curvature
      because he will be facing the monitor screen.

      Timing will continue until end-tidal CO2 of at least 30 mmHg is seen on the anesthesia
      monitor, at which point the data collection form will be filled out, and the study protocol
      will be finished. (The time to intubation will be recorded to the nearest tenth of a second.)
      If the operator fails to intubate within 3 attempts or 150 seconds, the intubation will be
      noted as a failure, and the ultimately successful means of securing the airway will be
      recorded.

      The definition of an "attempt" for the purposes of this clinical trial are as follows:

        1. anytime the GlideScope blade is removed from the patients mouth and then re-inserted

        2. anytime the endotracheal tube is re-shaped (regardless of whether or not the GlideScope
           is actually removed from the patient's mouth

        3. if substantial adjustments are made to the patient's position (such as head position,
           neck flexion, or neck extension). Small movements that would occur in the normal process
           of intubation would not count as "substantial".

      If oxygen desaturation (as recorded by pulse oximetry) below 95% occurs, then the patient
      will be ventilated in the usual fashion to ensure oxygenation, and re-attempting intubation
      using the GlideScope may proceed, but the timing will continue, and the same limits to
      successful intubation (within 3 attempts or total of 150s) will apply. Between attempts, the
      tube may be re-shaped by the operator if the operator feels that another curvature would be
      preferred.
    

Intervention name(s): Flex-It Stylet; Standard malleable stylet
Intervention type(s): Device; Device
Intervention description(s): Patients will be intubated using the GlideScope with an ETT fitted with a Flex-It stylet.; Patients will be intubated using the GlideScope with an ETT fitted with a standard malleable stylet.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Investigator)
Primary purpose: Treatment
Keywords: Intubation, Flex-It, stylet, GlideScope