Technique of Placement of Extraglottic Devices
Technique of Placement of Extraglottic Devices
During the last two decades, extraglottic airway devices have dramatically changed the landscape of airway management. While there are many devices commercially available, it would be impractical to discuss all of these devices. Only a few selected ones with substantial clinical experience will be discussed in this narrative.
Segment:2 Laryngeal Mask Airway (LMA) Classic.
The Laryngeal Mask Airway Classic, or LMA Classic, has a wide-bore airway tube connecting to an inflatable cuff that seals around the larynx.
The distal airway tube has aperture bars to prevent obstruction by the epiglottis.
Successful use of the LMA often depends on the selection of an appropriate size for the patient. Typically, a number 3 LMA is used in small adults, number 4, 5, and 6 in average and large-size adults.
Following complete deflation of the cuff, the LMA is well lubricated with a water-soluble lubricant. Provided that there is no contraindication to moving the cervical spine, the patient's head and neck should be placed in a sniffing position. The head tilt will help to open the mouth.
While many techniques have been suggested for the insertion of the LMA, the following steps are recommended.
Lift the mandible forward by grasping the mandibular incisors and chin with the non-inserting hand. The LMA should be inserted into the mouth with the index finger placed between the mask tube junction, pressing the cuff against the hard palate and advancing the LMA into the oral pharynx, following the natural curve of the posterior pharyngeal wall. A definite resistance should be felt as the tip of the LMA traverses the hypopharynx to its proper position.
Following placement, a cup should be inflated with the minimal volume of air necessary to achieve an adequate seal. The LMA should be secured in position by taping it to the base.
Segment:6 Trouble Shooting.
Occasionally the glottis folds downward during the LMA placement, causing partial airway obstruction.
In order to have a clear access to the glottic opening and minimize down-folding of the epiglottis, it is recommended that the practitioner perform a jaw lift using the thumb and index finger of the non-dominant hand, as shown earlier. This lifts the tongue and epiglottis away from the posterior pharyngeal wall to facilitate placement of the LMA. Occasionally, resistance is encountered during insertion because of backward folding of the cuff.
Sweeping a finger behind the cuff to redirect it inferiorly into the laryngopharynx can easily overcome the problem, as shown in this video. A bite block should be placed to prevent biting and occlusion of the device, potentially leading to post-obstructive pulmonary edema.
Segment:7 Proseal LMA .
Segment:8 Device .
The Pro-Seal LMA is a laryngeal mask variant that incorporates several modifications of the LMA Classic.
It lacks aperture bars, has a deeper bowl, and incorporates an esophageal drain tube to provide access to the esophagus. This drain tube and the deeper bowl of the cuff make it difficult for the epiglottis to occlude the distal aperture. The ProSeal LMA also has a flexible, wire-reinforced airway tube to improve flexibility and an incorporated bite block to reduce the danger of obstruction secondary to biting.
An introducer is available as a reusable device to facilitate ProSeal LMA placement. Its distal end fits into the insertion strap of the ProSeal, and the proximal end clips to the airway tube above the bite block. Number 18 French gauge or smaller gastric tubes can be inserted through the conduit to facilitate gastric decompression.
The ProSeal LMA can be inserted similarly to the LMA by using the digital technique involving the placement of the index finger under the insertion strap during insertion. Alternatively, prior to its placement, the ProSeal LMA can be loaded onto an introducer by placing the distal end of a metal introducer in an insertion strap on the ProSeal LMA. The airway tube is folded around the introducer and clipped into a proximal matching slot.
However, to optimally place the tip of the ProSeal LMA cuff in the hypopharynx, is probably most reliable to use a tracheal introducer, such as an Eschmann introducer. The head and neck of the patient should be placed in a sniffing position. Following the placement of the tracheal introducer into the esophagus under direct vision with a laryngoscope, the ProSeal LMA is guided into a position by placing the tracheal introducer through the esophageal conduit.
The tracheal introducer is removed following placement of the ProSeal LMA above the hypopharynx. Proper placement of the ProSeal LMA can be confirmed by a number of techniques. Air leaks through the drainage tube at low airway pressures suggest malposition of the ProSeal LMA. Though air leaks are ordinarily easily detected by auscultation or by feeling air exiting the drainage tube, a small-volume leak is probably best detected by the soap bubble test.
Other tests have been used. These include passing a gastric tube through the drainage tube or passing a fiber optic bronchoscope through the drainage tube.
The Combitube is a double-tube airway with a partition wall separating the two tubes. The blue pharyngeal tube is blocked at the distal end, but there are eight small perforations.
The transparent esophagotracheal tube has open proximal and distal ends. The device has two balloons designed to trap the epiglottis between them. An oral pharyngeal balloon, positioned just behind the posterior part of the hard palate, is designed to seal both mouth and nose. Another smaller cuff seals the esophagus once inflated. Lying between the two balloons are the perforations from the pharyngeal tube to prevent the movement of gas.
Two circumference rings printed on the proximal end of the tube indicate proper depth of insertion when the upper teeth or alveolar ridges are situated between these two marks. The Combitube is available in two sizes. The 37 FSA for small adults should be used in patients 4 to 6 feet in height, or 1.2 to 1.8 meters. A size 41 F Combitube is designed for patients taller than 6 feet or 1.8 meters.
Lubrication of the device prior to its use will facilitate its placement. Insertion can be facilitated by first bending the Combitube between the balloons for a few seconds before insertion. The device can be made more pliable if heated to body temperature, attenuating its blunt trauma potential.
Placement of the Combitube is most readily performed with the patient's head in a neutral position. While the Combitube may be inserted blindly using a jaw lift to elevate the tongue and epiglottis, the use of a laryngoscope can facilitate the placement of the Combitube. With the laryngoscope elevating the tongue and the epiglottis, the Combitube is inserted along the surface of the tongue with initial downward curve dorsal caudal movement and then directed parallel to the patient's horizontal plane until the printed ring marks lie between the upper and lower teeth or alveolar ridges in the edentulous patient.
After insertion, the oropharyngeal balloon of the Combitube is inflated with 85 milliliters of air through a blue pilot balloon for a 37 F and 100 milliliters for the 41 F Combitube. Then the distal balloon is inflated with approximately 10 milliliters of air. Correct positioning of the Combitube can be confirmed by auscultation of breath sounds over the chest, the absence of gastric insufflation, end tidal C02 detection, and esophageal detection devices.
Should the Combitube enter the trachea on blind insertion,
Segment:14 Trouble Shooting.
it can function like a standard endotracheal tube and there is no need for inflation of the pharyngeal cuff. Although it is rare, ventilation may be impossible through either the proximal or distal lumen. This usually signifies that the Combitube has been placed too deeply, with the proximal lumen positioned in the esophagus and the oropharyngeal balloon obstructing the entrance to the larynx.
After deflation of the balloons, the Combitube should be withdrawn approximately 2 to 3 centimeters.
Segment:15 Summary .
In summary, extraglottic devices such as the LMA, the ProSeal LMA, and the Combitube have been shown to be effective and safe for ventilation and oxygenation. Successful use of these devices requires proper device preparation and insertion technique.
Since the introduction of the LMA, many newly designed reusable and disposable extraglottic devices have been introduced. These include the disposable LMA Unique, the LMA Supreme, the Laryngeal Tube Airway, and the Cobra Parapharyngeal Airway. However, more clinical studies are needed to confirm the safety and efficacy of these newer devices.