Three Inflation Methods of Ambú Auragain™ and Its Adverse Effects

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)

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.

Eligibility Criteria:
Inclusion Criteria:

* Patients age between 18 and 90 years
* American Society of Anesthesiologist (ASA) physical status I-III
* fiberoptic bronchoscopy procedure and EBUS-TBNA procedure programmed.
* Fasted for 6 hours before procedure.
* Management of the airway for the same anesthetic.
* Use de laryngeal mask airway for boarding and maintenance of airway permeability.

Exclusion Criteria:

* LMA is contraindicated because high risk of aspiration (full stomach, gastroesophageal reflux history, pregnant)
* predictors of difficult airway such restricted mouth opening (\< 2 cm of interincisal distance)
* patients with any pathology of the neck, upper respiratory or upper alimentary tract
* dysphagia o hoarseness.