A Study of Laryngoscopic Vision With the TotalTrack Device Versus Indirect Laryngoscopy
Condition: Airway Obstruction; Difficult Intubation
MeSH terms: Airway Obstruction
Study type: Observational [Patient Registry]

Summary: 
      Assessment of the airway forms part of routine anesthetic practice. However, the predictions
      referred to intubation or ventilation difficulties are usually inconclusive. In effect, the
      failure rate in predicting such difficulties exceeds 60%. In this scenario it is not possible
      to know whether a given patient will be difficult to intubate and ventilate. These are
      referred to as non-intubate and non-ventilate cases with a high risk of severe neurological
      complications and even death due to hypoxemia. According to all the clinical guides, the
      solution in such cases usually involves the use of supraglottic devices that rescue
      oxygenation through effective ventilation.

      In the event of ventilation failure with a supraglottic device, it is currently not possible
      to know whether the device is correctly positioned, unless some other instrument such as a
      flexible fiberscope is used to visualize the anatomy beyond the ventilation device.

      The TotalTrack is a new device with all the characteristics of a supraglottic device that
      moreover includes a camera at the tip, allowing us to confirm anatomical positioning with
      respect to the glottic structures. This device also allows intubation under indirect
      visualization of the glottis, thus adding the possibility of definitive patient lung
      isolation.

      The primary objective of this study is to determine the capacity to visualize the glottic
      structures through the camera of the TotalTrack device, compared with glottic visualization
      afforded by indirect laryngoscopy in the same patient. The Cormack-Lehane scale and
      percentage of glottic opening (POGO) are used for this purpose.

      The secondary objectives comprise assessment of the ventilation, intubation and TotalTrack
      device withdrawal times. The hemodynamic changes associated to both techniques during
      intubation and TotalTrack device withdrawal are also evaluated. Minimum patient oxygenation
      throughout the procedure is assessed. The sealing and ventilation pressures during operation
      of the TotalTrack device are recorded. Likewise, an analysis is made of the number of
      placement attempts, visualization improvement maneuvers, and minor complications associated
      to the use of the TotalTrack device (presence of blood upon withdrawal or pharyngeal pain),
      with their degree of severity.
    

Detailed description: 
      The study hypothesis is that the new TTK device improves laryngoscopic visualization compared
      with direct laryngoscopy, thereby facilitating orotracheal intubation success.

      The null hypothesis is that the new TTK device does not improve visualization of the glottic
      structures, the intubation conditions, or intubation success compared with direct
      laryngoscopy.

      3. Objectives 3.1 Primary objective To determine whether the new TTK device improves
      laryngoscopic visualization as determined by the Cormack-Lehane scale and percentage of
      glottic opening (POGO), versus conventional laryngoscopy.

      3.2 Secondary objectives

        1. To assess intubation success, the laryngoscopy and intubation times, sealing pressure
           and subjective difficulty with the TTK intubation device.

        2. To evaluate the hemodynamic impact, oxygenation and complications associated to the use
           of both intubation techniques.

      4. Methodology 4.1 Type of study A prospective, multicenter, comparative observational study
      has been designed.

      4.2 The study will begin following approval by the Clinical Research Ethics Committees of the
      participating hospitals, and will have an estimated duration of 9 months.

      4.3 Study population The study will involve patients scheduled for surgery and requiring
      orotracheal intubation as routine practice.

      According to the literature, the fibroscopic intubation success rate with other supraglottic
      devices is close to 98%, versus 95-98% in the case of direct laryngoscopy. Considering a 95%
      confidence interval and a study precision of 80%, the required sample size is 102 patients. A
      total of 30 patients will be enrolled per center in order to compensate for possible losses
      during follow-up.

      4.4 Inclusion criteria Patients with ASA score I-III Age > 18 years Signing of the informed
      consent document

      4.5. Exclusion criteria Age < 18 years Pregnant or breast-feeding women Patients with known
      difficult airways Patients requiring rapid sequence intubation

      4.6 Study withdrawal criteria Patients who after inclusion in the study fail to comply with
      the protocol due to medical reasons, or who withdraw consent.

      4. 7 Study protocol A prospective, multicenter, observational study has been designed,
      involving patients scheduled for surgery of any kind and requiring tracheal intubation,
      following the obtainment of informed consent. The study will include ASA I-III patients over
      18 years of age. Individuals requiring rapid sequence intubation or diagnosed with difficult
      airways will be excluded.

      Demographic data will be collected before anesthesia (age, gender, body mass index and ASA
      score), with evaluation of the airway (Mallampati score, thyroid-chin and sternum-chin
      distances, interincisal distance, upper lip bite test, neck flexion, dental prostheses,
      obstructive sleep apnea syndrome, presence of a beard and neck perimeter) and history of
      laryngoscopic procedures (if any). The patients also will be questioned about past neck
      irradiation, neck or ENT surgery and lingual tonsil hypertrophy, in order to predict
      supraglottic device management difficulties.

      With the patient in the pre-operating room, a peripheral venous line will be prepared and
      premedication will be administered according to routine anesthetic practice.

      Once in the operating room, standard monitoring will be carried out, with peripheral O2
      saturation (SpO2) pulseoximeter, noninvasive arterial pressure (NIAP) and electrocardiography
      (ECG). The depth of hypnosis should be evaluated based on the bispectral index (BIS)(or
      through entropy monitoring), with the assessment of neuromuscular relaxation through train of
      four (TOF) monitoring.

      Correct patient oxygenation will be performed during 3-5 minutes, with an inspiratory oxygen
      fraction of 100% using a correctly sealed face mask, with the aim of achieving an end-tidal
      O2 level of over 90% (ETO2 > 0.9). Following the above, anesthesia induction will be carried
      out with fentanyl (1-2 µg kg-1), propofol (2-3 mg kg-1) and rocuronium (0.6 mg kg-1).
      Endotracheal intubation will be performed when TOF = 0. Conventional laryngoscopy will be
      carried out using a Macintosh blade in all patients, recording the exploration times and the
      best laryngeal visualization achieved (using the Cormack-Lehane scale and percentage of
      glottic opening [POGO]) with or without BURP (backward, upward and rightward pressure on the
      thyroid cartilage) maneuvering. The best laryngeal vision achieved after these maneuvers will
      be recorded. The TotalTrack (TTK) video laryngeal mask will then be placed.

      Prior to intubation with this new device, the investigators will measure the TTK sealing
      pressure, setting the respirator to manual mode, closing the expiratory valve to 40 cmH2O,
      and adjusting the fresh gas flow to 3 litres. The pressure at which audible leakage occurs
      will be measured. If the pressure exceeds 40 cmH2O, the test will be considered over, and
      this latter value will be recorded as the TTK sealing pressure (> 40 cmH2O).

      Lastly, intubation will be carried out with an endotracheal tube half a grade less than the
      maximum recommended by the manufacturer of the TTK.

      During both direct laryngoscopy and after placement of the TTK, the best laryngoscopic vision
      achieved will be recorded, based on the Cormack-Lehane scale and POGO, together with the
      laryngoscopy and intubation times. The laryngoscopy time is defined as the time elapsed from
      insertion of the laryngoscope or study device through the teeth to best vision of the
      glottis. The intubation time in turn is defined as the time elapsed from collapse of the
      endotracheal tube cuff to definitive positioning of the instrument beyond the vocal cords
      (insertion mark on the tube), following capnographic confirmation of correct intubation. If
      correct positioning is not achieved, the maneuver will be repeated, recording the time from
      collapse of the cuff in the esophagus to correct positioning of the endotracheal tube. The
      times will be recorded as accurately as possible. The use of a chronometer is advised.

      Data will be collected referred to heart rate, blood pressure (systolic / diastolic) and BIS
      / entropy monitoring at the following times:

        1. Before the induction of anesthesia (baseline value)

        2. Two minutes after the induction of anesthesia (post-induction baseline value)

        3. Immediately after direct laryngoscopy (post-direct laryngoscopy stress response)

        4. Before insertion of the TTK (post-direct laryngoscopy baseline value)

        5. Immediately after insertion of the TTK (post-TTK stress response)

        6. After tracheal intubation (post-intubation stress response)

      The BIS will be within anesthetic values at all times. If necessary, additional hypnotic drug
      doses (propofol) will be administered (to be reflected in the total administered dosage).

      Evaluation of the subjective technical difficulty of the new device will be based on a
      numerical scale from 1-10 (1 = very easy, 10 - insertion impossible).

      Other data to be recorded for assessing the difficulties of the two techniques are the need
      for repositioning of the TTK, external laryngeal manipulation maneuvers (BURP, lateralization
      of the neck), the use of assists in intubation, and the number of attempts required to secure
      orotracheal intubation.

      The following complications will be documented: esophageal intubation; trauma of the mouth,
      lips, tongue or teeth; presence of blood in the device; throat pain and dysphonia (in the
      post-anesthesia recovery unit and 24 hours after surgery).

      5. Statistical analysis A descriptive analysis will be made of all the variables, including
      the demographic data, predictors of difficult intubation, number of insertion and intubation
      attempts, and the TTK intubation and withdrawal times. Continuous variables will be reported
      as the mean and standard error, while categorical variables will be reported as frequency and
      percentage. The chi-squared test will be used to compare categorical variables, while
      quantitative variables will be contrasted using the Student t-test. The data will be analyzed
      using the Statistical Package for the Social Sciences (SPSS, Chicago, IL, USA), version 20.0.

      7. Strengths of the study If the study is successfully completed, the anesthesiologist will
      have a new tool for orotracheal intubation that may minimize complications in the case of
      difficult airways - thereby reducing healthcare resource utilization and the length of
      hospital stay.

      The use of this device in the management of expected or unexpected difficult airways could
      avoid important postoperative complications associated to such difficulties. In future,
      increased experience and a larger number of patients could consolidate the TTK in an
      important position in the difficult airway management algorithms.

      8. Expected impact

      If the study hypothesis is correct, the benefits of improvement in the intubation technique
      include:

        -  A lesser risk of complications derived from hypoxemia, including irreversible brain
           damage and death.

        -  Early discharge from the post-anesthesia recovery unit (PARU).

        -  Early discharge from hospital.

        -  Significant reduction of healthcare costs.
    

Observational model: Case-Only
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Patients who after inclusion in the study fail to comply with the protocol due to medical
        reasons, or who withdraw consent.
      
Keywords: intubation to supraglottic devices; intubation device; laryngeal vision; success intubation; videolaryngoscope; direct intubation