الفهرس 
Anatomy of the Airway
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Abstract
Supraglottic airways (SGAs), including laryngeal mask airways (LMAs), are used for airway management for anesthesia, for primary airway management, as conduits for endotracheal intubation, and for rescue ventilation.
SGAs are available in a range of sizes and a variety of styles; some are designed to allow placement of an orogastric tube, while others are designed to allow endotracheal intubation through the device. The optimal SGA size for a given patient is one that minimizes leak without excessive cuff inflation.
The usual method for LMA and other SGA insertion is as follows:
- The LMA cuff is lubricated with a water-based lubricant.
- The device is then held with the index finger of the dominant hand placed at the junction between the cuff and the airway tube.
- The cuff is pressed upward against the hard palate with the index finger, then backward and downward along the palate in a smooth movement until resistance is encountered. As the index finger is removed, the nondominant hand pushes down on the LMA in order to prevent dislodgment.
- The cuff is subsequently inflated to a target cuff pressure of around 40 cmH2O or to the minimum pressure needed to create an adequate seal.
SGAs can be used with the patient breathing spontaneously or with positive pressure ventilation (PPV). Pressure-limited ventilation (ie, pressure support or pressure control) is usually used with a SGA in place, rather than volume-control ventilation. Peak pressures should be kept below 20 cmH2O in order to minimize leak and gastric insufflation.
A SGA can be used as an airway rescue device when mask ventilation is difficult or impossible. It can also be used as a conduit for endotracheal intubation.
SGAs do not provide complete protection against aspiration of stomach contents.
Use of SGAs in obese patients is limited by the potential need for higher peak inspiratory pressures and the possibility of difficult seating of the device.
SGAs can be used for airway management in the prone position, as the primary airway device in selected patients, and as rescue devices. We limit prone SGAs to those patients without risk factors for difficult airway management, without limitations in neck movement, and who will undergo short procedures that do not require paralysis (eg, hemorrhoidectomy, rectal fistulotomy).
Complications of SGA use include failed placement, aspiration, and airway complications, including airway trauma. Sore throat, dysphonia, and dysphagia may be related to high SGA cuff pressures. The cuff inflation should be limited to approximately 40 cmH2O or the minimum volume required for an adequate seal.