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

Summary: 
      Laryngeal mask airway device (LMA) is a common device used in the daily practice for airway
      management. Consecutive generations have permitted an expansion of its use, probably because
      of a rapid increase of ambulatory surgical procedures and also due to the development of
      procedures in areas away from the operating room.

      The cuff inflating volume is not standardized and it is common practice to inflate the LMA
      cuff according to the manufacturer's recommendations, without using a manometer.

      A hyperinflation of the LMA 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 AuraOnce™ LMA
      during fibrobronchoscopy 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 (NVgroup)
    

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 patient before the procedure. We plan to include 210 patients scheduled for a
      fibrobronchoscopy with EBUS-transbronchial needle aspiration (TBNA) procedures under general
      anesthesia using a LMA. Patients 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 patients have lost eyelash reflex. Then, the assigned LMA will be
      inserted, after appropriate conditions for 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, we 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 patients 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 patients 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 LMA will be fixed with adhesive tape and the vital signs will be stable, the LMA
      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 patients 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 patient
      satisfaction scores using visual analog scales.
    

Intervention name(s): intracuff pressure measurement; intracuff pressure measurement; intracuff pressure measurement
Intervention type(s): Device; Device; Device
Intervention description(s): intracuff pressure is measured by a pressure manometer; intracuff pressure is measured by a pressure manometer; 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