CONFIRMATION OF PROSEAL SUPRAGLOTTIC AIRWAY DEVICE PLACEMENT BY LEAK TEST, ULTRASOUND AND FIBEROPTIC BRONCHOSCOPE

All patients will undergo a complete pre-anesthetic evaluation and NPO for 6 hours. All patients will be administered general anesthesia for the procedure. A standardized protocol for induction and maintenance of anesthesia will be follow which would comprise of intravenous fentanyl (1-2mcg/kg) followed by propofol (1.5-2mg/kg) for induction. Airway will be secured by an appropriate size Proseal SAD following administration of a non-depolarizing muscle relaxant. Size 3 Proseal will be use for patients weighing 30-50 Kg, size 4 for patients weighing 40-70 Kgs and size 5 for patients weighing 70-100 Kg.

Anesthesia will be maintained with desflurane in oxygen and nitrous oxide titrated to maintain FiO2 of 0.5 at all times.A non-depolarizing muscle relaxant will be administered for maintenance of neuromuscular blockade. Standard volume control ventilation settings will be used in both groups with tidal volume of 8ml/kg, to maintain minute ventilation of 100ml/kg and end-tidal carbon dioxide (EtCO2) between 30-40 mm Hg. Leak pressure test will be conducted in all cases receiving Proseal SAD and the leak pressure shall be recorded.

Airway leak pressure is defined as “the airway pressure (PL) at which the leak was heard with fresh gas flow (FGF) at 3 L/min and adjustable pressure limiting (APL) valve closed gradually up to 40 cm H2Oâ€. After the leak test, ultrasound examination on front of neck will be done in three planes and scoring done using the Ultrasound score system as below:

Plane             Ultrasound examination                                                                                       Comments

THT             2 cuff shadows                                                                                                      symmetrical/asymmetrical

TLS             Edge of the cuff tip and the shape of the cuff                                                       distorted and irregular/ smooth and regular

PPL             visualize the cuff tip and esophagus in the same plane by adjusting transducer   Possible/ impossible

THT = transverse plane between hyoid bone and thyroid bone;

TLS =transverse plane of lateral suprasternal notch;

PPL = parasagittal plane of pharynx and larynx.

Fiberoptic examination will be done through Proseal SAD to confirm the position of SAD. The fiberoptic endoscope will be typically positioned just proximal to the end of the ventilator conduit, and then an attempt will be made to advance it under the epiglottis to see the vocal cords. Optimal placement is when the tip of the Proseal lying behind the arytenoids with a visible epiglottis, with no folding or intrusion into the airway, and with the vocal cords visible when the fiberscope advanced under the epiglottis.All other situations will be considered suboptimal placement. Fiberoptic examination will be done in only those cases where leak test is positive.

At the end of the procedure, neuromuscular blockade will be reversed and post extubation patient will be shifted to PACU for observation.