Three Inflation Methods of Ambú Auragain™ and Its Adverse Effects
Condition: Laryngeal Mask Airway
Study type: Interventional

Summary: 
      Laryngeal mask is a common supraglottic device (SGD) used in the daily practice for airway
      management. Consecutive generations have permitted an expansion of its use. At the moment,
      the SGD is being used in several situations, which include general anesthesia,
      cardiopulmonary resuscitation, and difficult airway management.

      To insert the SGD safely in these situations, the Fourth National Audit Project has
      encouraged the use of second-generation SGD equipped with the passage of a nasogastric tube.
      Ambu Auragain™ is a recent second-generation SGD with an incorporated gastric drainage
      channel and the capability of working as a conduit for tracheal intubation. It has higher
      leak pressure than the ones of first generation, which is a key marker of efficacy and safety
      of its use; a higher leak pressure suggests a better seal between the artificial airway and
      patient's airway.

      However, there are still few reports of which volume of cuff is the most appropriate for it
      use. The cuff inflating volume is not standardized and it is common practice to inflate the
      SGD cuff according to the manufacturer's recommendations, without using a manometer.

      A hyperinflation of the laryngeal mask cuff was associated with complications ranging from
      sore throat, or dysphagia and dysphonia, to more serious complications such as paralysis of
      the vocal cord, arytenoid cartilages dislocation, recurrent laryngeal nerve injury and
      hypoglossal nerve injury. Also, the excess of volume or pressure is related to poor
      ventilation and increase the risk of gastric insufflation.

      The aim of this study is to evaluate the best cuff inflation method, in order to limit the
      intracuff pressure beyond the recommended maximum pressure (PM < 60 cmH2O) and to allows
      decrease the pharyngo-laryngeal complications.

      The Primary outcome is to compare three different cuff inflating methods using Auragain™
      laryngeal mask during fibro bronchoscopy and endobronchial ultrasound (EBUS) procedures, and
      to control the intracuff pressure, and the effect on pharyngo-laryngeal complications.

      The three different cuff inflating methods are: 1) residual volume group (RV group ) 2) half
      of the maximum volume group (MV group) 3) unchanged volume group (NV group)
    

Detailed description: 
      This is a prospective randomized controlled trial. The study was approved by the Ethics
      Committee of University Hospital of La Paz, Madrid. Written informed consent will be obtained
      from each participant before the procedure. The investigators plan to include 210
      participants scheduled for fibrobronchoscopy with EBUS-trans-bronchial needle aspiration
      (TBNA)) procedures under general anesthesia using a laryngeal mask airway device (LMA).
      Participants will be allocated randomly to one of three groups of cuff inflating methods
      according to computer-generated randomization. The size of LMA will be chosen according to
      body weight, following the manufacturer recommendations (LMA size 3 for patients of 30-50 kg,
      LMA size 4 for patients of 50-70 kg and LMA size 5 for patients with a weight >70 kg). After
      standard monitoring with electrocardiography, noninvasive blood pressure device and pulse
      oximeter were applied, general anesthesia will be induced with Propofol 2.5 mg.kg-1 and
      fentanyl 1 mcg.kg-1 intravenously, face mask ventilation with 100% oxygen will be used after
      participants have lost eyelash reflex. Then, the assigned LMA will be inserted, after
      appropriate conditions for laryngeal mask insertion are obtained. LMA Insertion will be
      performed with standard maneuver according to LMA practice manual by the same experienced
      anesthesiologist (> 1-year use experience). The initial position of LMA will be assessed by
      visualization of bilateral chest movement when positive pressure ventilation will be
      performed and the square capnography waveform is observed on the monitor screen.

      If the LMA is not in the proper position at the first attempt, anesthetist will use an "up
      and down" maneuver to adjust and reposition LMA to attain satisfactory ventilation. If this
      maneuver fails, LMA will be withdrawn from the mouth of the participants and a second attempt
      will be authorized to acquire a correct position. If the proper position of LMA cannot be
      achieved after two attempts, the airway will be controlled with another device or a tracheal
      intubation will be performed and the participants will be excluded from the trial.

      The patient´s lungs will be ventilated with the anesthesia machine in controlled volume mode,
      using the following parameters: Tidal volume, 8 ml/kg; frequency, 12-14 per min; the ratio of
      inspiratory and expiratory, (I: E) = 1:2; and positive end expiratory pressure, 5 cmH20.

      After the laryngeal mask will be fixed with adhesive tape and the vital signs will be stable,
      the laryngeal mask cuff will be connected with a closed system manometer composed of a
      three-way stopcock, a 5 ml syringe and a manometer. Intracuff pressure will be measured and
      recorded, if it exceeds of 60 cmH20 we will deflate the cuff 1 mL by 1 mL with the syringe
      until intracuff pressure reaches 60 cmH20. The deflated volume and the final intracuff
      pressure will be recorded. We will measure the inspiratory peak airway pressure, the volume
      difference of inspiratory and expiratory tidal volume under the positive pressure
      ventilation. The plateau pressure, medium pressure and Compliance will also be recorded at
      the corresponding cuff inflating volume, before and after measuring OLP. The OLP will be
      measured simultaneously at the corresponding cuff inflating volume, by setting the airway
      pressure relief valve (APL) of the breathing circuit to 40 cmH20 at a fixed gas flow rate of
      4 L/ min and reading the airway pressure on manometer at which equilibrium of airway pressure
      will be established or at the pressure the air leakage will be heard.

      Fiberoptic visibility scores will be recorded on a scale of 1 to 4 (4: only vocal cords
      visible, 3: vocal cords plus posterior epiglottis visible, 2: vocal cords plus anterior
      epiglottis visible, 1: vocal cords not seen). A score of 1 will be considered the worst and a
      score of 4 was considered the best.

      Any adverse events (i.e., desaturation (pulse oximetry< 90%), aspiration/regurgitation,
      bronchospasm, airway obstruction, coughing, gagging or vomiting) and corresponding
      interventions will be recorded.

      After the procedure, all participants will be transferred to the recovery unit and observed
      for at least 1 hour. Observed adverse effects, such as sore throat, hoarseness, aphasia,
      nausea and vomiting will be recorded in the recovery room period.

      At 24h, a home telephone interview will record these parameters, as well as participants
      satisfaction scores using visual analog scales.
    

Intervention name(s): Intracuff pressure measurement
Intervention type(s): Procedure
Intervention description(s): Intracuff pressure is measured by a pressure manometer.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Triple (Participant, Care Provider, Investigator)
Primary purpose: Prevention
Keywords: laryngeal mask; intracuff pressure; sore throat; oropharyngeal leak pressure