Michael F. Murphy
Introduction
The first laryngeal mask airway (LMA) was introduced in 1981 as an alternative to mask anesthesia. It quickly became apparent that this device was not only easier to use than a mask, but it was also more effective than the existing alternative, a face mask, and less invasive than an endotracheal tube (ETT). The esophageal tracheal Combitube (ETC or Combitube) has been in use since 1987. In concept, it is similar to the LMA. It provides a direct conduit for gas exchange that is easier to use and more effective than a bag and a mask, and less invasive than an ETT. The success these devices have enjoyed has spawned the evolution of similar devices attempting to mimic or improve on their safety; ease of use; and ability to facilitate spontaneous, assisted, or mechanical ventilation.
The terminology referring to these devices has been confusing. Some authors have referred to them as supraglottic devices (SGDs), although only certain designs are truly supraglottic (e.g., LMAs, CobraPLA [perilaryngeal airway], Pharyngeal Airway Express or PAXpress). The term retroglottic device(RGD) or infraglottic device(IGD) has been used to refer to those devices that pass behind and beyond the larynx to enter the upper esophagus (e.g., ETC, King LT airway, Rusch EasyTube). The following taxonomy emerges as reasonably descriptive of the class: the general term for this family of devices is extraglottic device (EGD). There are two subclasses: a SGD, which sits above and surrounds the glottis (e.g., LMA), and a RGD, or an IGD, which enters the upper esophagus (e.g., Combitube). These devices are supplied in reuseable and single-use variants.
EGDs differ from face mask gas delivery apparatus in that they are inserted through the mouth to a positon where they provide a direct conduit for air to flow into the lungs. They vary in size and shape, and most have balloons or cuffs that when inflated provide a reasonably tight seal in the upper airway to permit positive-pressure ventilation with variable limits of peak airway pressure.
Although bag-mask ventilation (BMV) is relatively simple in concept, it is difficult or impossible to perform in selected patients (see Chapter 7), even in the hands of experts. Use of an EGD is a more easily acquired skill than BMV for the nonexpert airway practitioner.
Tracheal intubation is the “gold standard” for effective ventilation and protection from aspiration, but the skill is not easily mastered or maintained. The EGDs are a viable alternative to tracheal intubation in many emergency settings, particularly in prehospital care.
Finally, airway management difficulty and failure are associated with significant morbidity and mortality. Certain EGDs have a potential role in both the difficult (LMA) and failed (most EGDs) airway.
Thus, the indications for these devices have expanded over the past two decades to include using the devices:
· As an airway rescue when BMV is difficult and ETT has failed
· As a “single attempt” rescue device performed simultaneously with preparation for cricothyrotomy in the “can't inbutate, can't oxygenate” (CICO) failed airway (see Chapter 2)
· As an easier and more effective alternative to BMV in the hands of basic life support providers
· As an alternative to endotracheal intubation by advanced life support providers
· As an alternative to endotracheal intubation for elective airway management in the OR for appropriately selected patients
· As a conduit to facilitate endotracheal intubation (e.g., LMA Fastrach, Cookgas intubating laryngeal airway [ILA]).
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Figure 10-1 • LMA Classic. Note the aperture bars at the end of the plastic tube intended to limit the ability of the epiglottis to herniate into this opening. |
The Supraglottic Class
The LMA Classic (Fig. 10-1) serves as the prototype for much of the supraglottic class, although other designs also exist. Variants of this original design, also made by the Laryngeal Mask Company Limited, include both reuseable and nonreuseable (disposable) devices:
· Fastrach or intubating LMA (ILMA; reuseable and disposable) (Fig. 10-2)
· LMA Supreme (disposable) (Fig. 10-3)
· LMA ProSeal (reuseable)
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Figure 10-2 • LMA Fastrach or Intubating LMA (ILMA). Both the reuseable and disposable variants are pictured. The most unique feature of this device that confers a particular advantage is the handle to permit positioning in the hypopharynx to improve airway seal and the capacity for adequate gas exchange. This factor may be crucial in rescuing a failed airway. |
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Figure 10-3 • LMA Supreme. The rigid construction of the tube and the curvature of the device enhance insertion characteristics and the immediacy of the seal obtained once inflated. |
· LMA Unique (disposable variant of the LMA Classic)
· LMA Flexible (reinforced tube variant of the LMA Classic)
· LMA CTrach, a videocapable variant of the LMA Fastrach (Fig. 10-4)
Other SGDs (both original designs and LMA derived) include:
· A variety of disposable LMA Classic–type designs (e.g., Portex, Solus)
· Ambu LMA (ALMA; disposable and reuseable) (Fig. 10-5)
· CobraPLA (disposable) (Fig. 10-6)
· Pharyngeal Airway Express (PAXpress) (Fig. 10-7)
· Cookgas ILA (reuseable) and Air Q (disposable) (Fig. 10-8A and B)
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Figure 10-4 • LMA CTrach. |
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Figure 10-5 • Ambu LMA (ALMA). This is the family of ALMAs. |
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Figure 10-6 • CobraPLA. |
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Figure 10-7 • PAXpress. |
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Figure 10-8 • A: The reuseable Cookgas ILA. B: The disposable Air Q variant. |
Laryngeal Mask Company Limited Devices
The original LMA was introduced into clinical practice in 1981 and looks like an ETT equipped with an inflatable, elliptical, silicone rubber collar (laryngeal mask) at the distal end (Fig. 10-1). The laryngeal mask component is designed to surround and cover the supraglottic area, providing upper airway continuity. Two rubber bars cross the tube opening at the mask end to prevent herniation of the epiglottis into the tube portion of the LMA. The LMA Classic is a multiuse (reuseable) device.
The disposable and much less expensive variety of this device is called the LMA Unique. The LMA Flexible incorporates a nonkinkable design (“wire reinforced”) in the tube portion of the device to prevent kinking as the device warms. We do not recommend it for management of the emergency airway.
The LMA ProSeal incorporates an additional lumen through which one can pass a suction catheter into the esophagus or stomach. It also has a higher sealing pressure capacity than the LMA Classic (28 cm H2O vs. 24 cm H2O), theoretically conferring an advantage for ventilating patients requiring higher airway pressures, although the difference may not be clinically significant. Because of its expense, relative difficulty in insertion, and marginal benefit in the emergency situation, the LMA ProSeal does not currently have a place in emergency airway management.
A recently introduced disposable device called the LMA Supreme has compelling design characteristics that may make it suitable for emergency airway rescue, although evidence to support this contention is limited. It is the easiest of the Laryngeal Mask Company Limited devices to insert (comparable to the ALMA), seals readily, and, like the LMA ProSeal, has a channel through which a gastric tube can be passed. This device can be considered as a replacement for BMV and endotracheal intubation in the hands of nonexpert airway managers.
The LMA Fastrach, also called the ILMA, is the most important version of the LMA for rescue emergency airway management because it combines the high insertion and ventilation success rate of the other LMAs with specially designed features to facilitate blind intubation. The LMA Fastrach has an epiglottic elevating bar and a rigid guide channel that directs an ETT anteriorly into the larynx, enhancing the success rate of blind intubation. The LMA Fastrach device is a substantial advance in airway management, particularly as a rapidly attempted rescue device in the CICO situation while preparations for cricothyrotomy are underway. The LMA Fastrach is supplied in both reuseable and disposable forms.
The LMA devices are easy to use, produce little in the way of adverse cardiovascular responses on insertion, and, as mentioned previously, have the potential to play a significant role in both routine and rescue emergency airway management. Ventilation success rates near 100% have been reported in operating room (OR) series, but patients with difficult airways were excluded, so the emergency airway ventilation success rate is probably somewhat lower. Intubation success rates through the ILMA are consistently in the 95% range, significantly better than through the standard LMA (about 80%). However, an LMA does not constitute definitive airway management, defined as a protected airway (i.e., a cuffed ETT in the trachea) unless one is successful at passing an ETT through the device into the trachea. Although they do not reliably prevent the regurgitation and aspiration of gastric contents, LMAs confer some protection of the airway from aspiration of blood and saliva from the mouth and pharynx.
The patient must have effective topical airway anesthesia (see Chapter 8) or be significantly obtunded (e.g., by RSI medications) to tolerate insertion of these devices. The LMA Classic and the LMA Fastrach are fairly expensive but can be autoclaved and reused. The disposable models, LMA Unique, LMA Supreme, and the LMA Fastrach, are much less expensive.
The LMA CTrach is an LMA Fastrach with a video capability that transmits the image at the distal end of the device to a screen mounted on the airway component. It has the same indications and insertion technique as an LMA Fastrach. The expense and learning curve of the device are unlikely to be acceptable to most emergency and emergency medical services (EMS) providers.
Indications and Contraindications
The standard LMA is now widely used in anesthetic practice instead of mask anesthesia, and the LMA Fastrach is becoming incorporated into difficult airway management.
The LMA and LMA Fastrach have two principal roles in rescue emergency airway management: (a) as a rescue device in a “can't intubate, can oxygenate” situation, or (b) as a single attempt to effect gas exchange in the CICO failed airway as one concurrently prepares to perform a cricothyrotomy (see Chapter 2). Any attempt to rescue the patient's airway with an LMA, however, must not delay the initiation of the cricothyrotomy.
The handle of the LMA Fastrach permits easier insertion of the device and allows for its manipulation to achieve optimum seal once the cuff is inflated. Thus, if one operator (or an assistant) is opening the cricothyrotomy tray, the principal airway manager can be placing the LMA Fastrach without risk of delay and increased duration of hypoxia. The LMA Fastrach can be used as a rescue device for a CICO airway when laryngeal pathology is not the reason BMV and endotracheal intubation have been unsuccessful. These devices have been used successfully in pediatrics, by novice intubators, during cardiopulmonary resuscitation, and in EMS.
Technique: LMA Fastrach
The LMA Fastrach comes in three sizes: no. 3, no. 4, and no. 5. The no. 3 will fit a normal-size 10- to 12-year-old child and small adults, and is recommended for persons weighing approximately 30 to 50 kg. Most average-size women will require a no. 3. Larger women and smaller men will take a no. 4, recommended for patients weighing 50 to 70 kg, and larger men will generally require a no. 5, recommended for those weighing more than 70 kg. For patients on the borderline between one mask size and another, it is generally advisable to select the larger mask because it provides a better seal.
The intention is to rescue a patent airway initially and recover the oxygen saturations by ventilating through the LMA Fastrach device. Once the saturations are adequate, endotracheal intubation through the device using the silicone-tipped ETT (although conventional ETTs can be used as well) that comes with the device can be accomplished. This can be done blindly or by using a fiberoptic scope or a lighted stylet (e.g., Trachlight). When using the Trachlight (see Chapter 11), it is helpful to remove the rigid metal stylet and and then mount the silicone-tipped LMA Fastrach ETT on the light-tipped wand. The result is instantaneous verification of successful tracheal intubation using the transillumination attribute of the Trachlight.
Select the appropriate-size LMA Fastrach. Deflate the cuff of the mask, and apply a water-soluble lubricant to the anterior and posterior surfaces and the greater curvature of the bend in the metal “stem.” Inflating the mask, and then deflating it while pressing the ventral surface of the inflatable collar firmly against a flat surface, produces a smoother and “flipped-back” leading edge (this is a feature of all Laryngeal Mask Company Limited device collars [Fig. 10-9]) and thus enhances the insertion performance. Hold the device in the dominant hand by the metal handle and open the airway. Insert the collar in the mouth, ensuring that the curved silicone-coated metal tube portion of the device is in contact with the chin and the mask tip is flat against the palate before rotation (Fig. 10-9).
1. Rotate the mask into place with a circular motion, maintaining firm pressure against the palate and posterior pharynx (Fig. 10-10A–C). Insert the device until resistance is felt and only the metal end of the silicone-coated tube protrudes from the airway.
2. Inflate the cuff of the LMA Fastrach and hold the metal handle firmly in the dominant hand, using a “frying pan” grip. Ventilate the patient with a ventilation bag, attached to the LMA Fastrach using the other hand. While ventilating, manipulate the mask with the dominant hand by lifting slightly as if to pull the mask toward the ceiling over the patient's feet (Fig. 10-11). This will provide a good mask seal and will ensure that the mask is correctly positioned for intubation. Best mask positioning will be identified by essentially noiseless ventilation, almost as if the patient is being ventilated through a cuffed ETT.
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Figure 10-9 • Correct method of deflating the LMA cuff. |
3. Visually inspect and inflate the silicone-tipped ETT that is supplied with the LMA Fastrach to verify cuff integrity and symmetry. Fully deflate cuff (important), lubricate the ETT liberally, and pass it through the LMA Fastrach. With the black vertical line on the ETT facing the operator (indicates that the bevel will be oriented with the narrowest part advancing in an anatomically advantageous orientation through the cords), insert the ETT to the 15-cm-depth marker, which corresponds to the transverse black line on the silicone-tipped ETT. This indicates that the silicone tip of the tube is about to emerge from the LMA Fastrach, pushing the epiglottic elevating bar up to lift the epiglottis. Use the handle to gently lift the LMA Fastrach as the ETT is advanced (Fig. 10-11). Carefully advance the ETT until intubation is complete. Do not use force of the ETT. Inflate the ETT cuff and confirm intubation. Then deflate the cuff on the LMA Fastrach.
4. Most of the time in the emergency situation, the LMA Fastrach and ETT are both left in situ. However, the LMA Fastrach can be removed fairly easily, leaving just the ETT in place. The key to successful removal of the mask is to remember that one is attempting to keep the ETT precisely in place and to remove the mask over it. First remove the 15-mm connector from the ETT. Then immobilize the ETT with one hand and gently ease the deflated LMA Fastrach out over the ETT with a rotating motion until the proximal end of the mask channel reaches the proximal end of the ETT. Use the stabilizer rod provided with the device to hold the ETT in position as the LMA Fastrach is withdrawn over the tube (Fig. 10-12). Remove the stabilizer rod from the LMA Fastrach and grasp the ETT at the level of the incisors (Fig. 10-13). The stabilizer bar must be removed to allow the pilot balloon of the ETT to pass through the LMA Fastrach (Fig. 10-14). Failure to do so may result in the pilot balloon being avulsed from the ETT, rendering the balloon incompetent and necessitating reintubation, preferably over an ETT changer.
Technique: LMA Classic, LMA Unique, and LMA Supreme
Although the LMA Classic, LMA Unique, and LMA Supreme can be rapidly inserted as primary airway management devices, or to rescue a failed airway with ventilation success rates comparable to that of the LMA Fastrach, they are not as effective as the LMA Fastrach for facilitating intubation. In fact, the LMA Fastrach is often easier to insert because of the handle and metal tube design. Select the appropriate size of LMA as described previously for the LMA Fastrach. Unlike the LMA Fastrach, the LMA Classic and the LMA Unique have smaller sizes (1, 1.5, 2, and 2.5) available for use in infants and children. The LMA Supreme is available in sizes 3 to 5.
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Figure 10-10 • A–C: Insertion of the LMA Fastrach. Note that only a short segment of the tubular portion of the device extends beyond the lips. This metal tube accepts a bag-mask device fitting to enable bag-mask ventilation. |
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Figure 10-11 • Lift the handle of the LMA Fastrach as the endotracheal tube is about to pass into the larynx to improve the success rate of intubation. This is called the Vergese maneuver after Dr. Archie Brain's associate Dr. Chandy Vergese. |
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Figure 10-12 • Use of the stabilizer rod to ensure the endotracheal tube is not inadvertently dragged out of the trachea as the LMA Fastrach is removed. |
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Figure 10-13 • The stabilizer rod is removed from the LMA Fastrach to permit the pilot balloon of the endotracheal tube (ETT) to go through the LMA Fastrach and prevent it from being avulsed from the ETT. |
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Figure 10-14 • The pilot balloon of the endotracheal tube emerges from the end of the LMA Fastrach intact. |
1. Place the device so that the collar is on a flat surface and inflate; then deflate the mask by aspirating the pilot balloon (Fig. 10-9). Completely deflate the cuff and ensure that it is not folded. The collar is designed to flip backward so the epiglottis is not trapped between the collar and the glottic opening. Lubricate both sides of the LMA with water-soluble lubricant to facilitate insertion.
2. Open the airway by using a head tilt as one would in basic airway management, if possible. Some, including the device inventor, recommend that a jaw lift be performed to aid insertion.
3. Insert the LMA into the mouth with the laryngeal surface directed caudally and the tip of your index or long finger resting against the cuff-tube junction (Fig. 10-15). Press the device onto the hard palate (Fig. 10-16) and advance it over the back of the tongue as far as the length of your index or long finger will allow (Fig. 10-17). Then use your other hand to push the device to its final seated position (Fig. 10-18), allowing the natural curve of the device to follow the natural curve of the oro- and hypopharynx to facilitate its falling into position over the larynx. The dimensions and design of the device allow it to wedge into the esophagus with gentle caudad pressure and to stop in the appropriate position over the larynx.
4. Inflate the collar with air—20 mL, no. 3; 30 mL, no. 4; 40 mL, no. 5—or until there is no leak with bag ventilation (Fig. 10-19). If a leak persists, ensure that the tube of the LMA emerges from the mouth in the midline, ensure that the head and neck are in anatomical alignment (i.e., neither flexed nor extended), reinsert the device, or go to the next larger size.
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Figure 10-15 • Correct position of the fingers for LMA insertion. |
Complications and Limitations
Unfortunately, the distal collar tip of the Laryngeal Mask Company Limited devices tends to “roll up” on insertion, creating a partial “insertion block” hindering optimal placement.
This feature also likely contributes to pharyngeal abrasion and bleeding that is often seen with these devices. Some authorities recommend partial inflation of the cuff to minimize tip roll, although there is little evidence that this helps. Insertion of the LMA Classic and LMA Unique “upside down” and rotating into place once in the hypopharynx has also been described and is preferred by some. This author prefers the deflated cuff, jaw lift, hard palate press technique.
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Figure 10-16 • Starting insertion position for the LMA Classic and LMA Unique. |
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Figure 10-17 • Insert the LMA to the limit of your finger length. |
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Figure 10-18 • Complete the insertion by pushing the LMA in the remainder of the way with your other hand. |
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Figure 10-19 • Inflate the collar of the LMA. |
Achieving a seal sufficient to enable positive-pressure ventilation with an LMA may be difficult. Keeping the tube portion of the device in the midline and altering the position of the head in neck from flexion (more usual) to neutral or extension may be of help. Overall, ventilation success rates are very high with all LMA-type devices. Optimal positioning improves ventilatory effectiveness and, in the case of the LMA Fastrach, facilitates intubation.
The LMA does not prevent the aspiration of gastric contents, serving to emphasize its role as a temporizing measure only. This limits its usefulness in prehospital and emergency airway care beyond that of a temporizing measure, except when the LMA Fastrach is used to achieve intubation. Cricoid pressure has variously been reported to hinder and help in achieving proper seat and seal of the LMA.
Other Supraglottic Devices
Disposable LMA-type Designs
Several manufacturers produce disposable devices that appear almost identical to the LMA Classic. Although they do not incorporate the epiglottic obturator bars seen in the LMA Classic and LMA Unique, the effect of their absence is not clear. These devices have the same indications, contraindications, insertion techniques, and complictions as similar Laryngeal Mask Company Limited devices.
The ALMA device (Fig. 10-5) has several unique design features that confer particular insertion and seal advantages:
· The device is semi-inflated in the package. This feature provides an “immediate seal” once inserted, eliminating the inflation step and speeding the time to ventilation.
· The leading tip of the inflatable collar is reinforced and “spatulated” to minimize tip roll and improve insertion characteristics.
· The tube incorporates a curve that is flexible at the curved portion and more rigid proximally to improve insertion characteristics.
Recently, the manufacturer softened the plastic in the curved portion of the tube in response to concerns that this portion of the tube might compress the hypopharyngeal mucous membrane and lead to ischemia. In this author's experience, this device and the LMA Supreme are the most easily inserted and rapid to seal of the disposable LMA-type devices.
Cookgas ILA and Air Q
Like the LMA Fastrach, the Cookgas ILA device (Fig. 10-8A) is a supraglottic ventilatory device that also permits endotracheal intubation. Conventional ETTs are used for intubation as opposed to a unique ETT as is supplied with the LMA Fastrach. The Air Q (Fig. 10-8B) is a disposable version of the Cookgas ILA.
CobraPLA
The CobraPLA (Fig. 10-6) consists of a breathing tube with a circumferential inflatable cuff proximal to the ventilation outlet portion, a 15-mm standard adapter, and a distal widened “cobra head,” which holds soft tissues apart and allows ventilation of the trachea. Once in place, the cobra head should lie in front of the laryngeal inlet. Inside the cobra head is a ramp that directs breathing gases into the trachea. Over the distal, anteriorly placed breathing hole of the cobra head, there is a soft grill. This feature helps direct the epiglottis off the cobra head anteriorly. The bars of the grill are flexible enough to allow the passage of an ETT. The cuff is shaped to reside in the hypopharynx at the base of the tongue, and when inflated, raises the base of the tongue exposing the laryngeal inlet, as well as effecting an airway seal. The CobraPLA is available in eight sizes according to the weight of the patient. The no. 3 is used for most female patients, the no. 4 for most men, and the no. 5 for larger men. When one is unsure of size, or when learning placement technique, it is advisable to pick the smaller size. The manufacturer supplies suggested age ranges for each size and cuff inflation volumes.
The lack of evidenciary support has hindered the application of this device in emergency airway management, routine or rescue.
Pharyngeal Airway Express
The PAXpress (Fig. 10-7) is a recently introduced SGD. It has not found its way into mainstream use, particularly in emergency airway management, due to a variety of factors, including a relatively high incidence of mucosal trauma. In addition, mucosal pressures may exceed pharyngeal perfusion pressure, and the PAXpress produces more marked changes in hemodynamic variables as compared with those produced by the LMA. Further studies are required to evaluate the safety and indications of this new extraglottic airway.
The Infra(Retro)Glottic Class
This class includes the following devices:
· ETC, or Combitube (Fig. 10-20)
· King LT airway (or laryngeal tube airway) (Fig. 10-21)
· Rusch EasyTube (Fig. 10-22)
· LaryVent (LV)
· Airway management device (AMD)
These devices are intended to be placed blindly into the esophagus. The Combitube, the King LT airway (called the laryngeal tube airway in some jurisdictions, e.g., Europe), and the EasyTube share a dual balloon design feature. One balloon seals the esophagus and the other the oropharynx, trapping the larynx between the two. The Combitube and the EasyTube employ two separate pilot balloons to enable independent balloon inflation; the King LT has a single pilot balloon. The LaryVent and the AMD have not achieved a body of evidence at the time of writing to recommend their use in emergency airway management and are thus not further discussed.
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Figure 10-20 • The Combitube Inserted and Seated. Note how the laryngeal aperture is trapped between the two balloons. |
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Figure 10-21 • The King LT airway. Note that there is only one pilot balloon to inflate both balloons. |
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Figure 10-22 • Rusch EasyTube. |
These devices share three indications in emergency airway management practice:
1. As a substitute for BMV in the hands of basic life support providers
2. As a substitute for endotracheal intubation when endotracheal intubation is not possible (e.g., patient entrapment) or providers are not sufficiently skilled to perform it
3. As a rescue device in the failed airway, simultaneous with preparation to perform a cricothyrotomy
These devices also share the following contraindications:
· Responsive patients with intact airway-protective reflexes
· Patients with known esophageal disease
· Caustic ingestions
· Upper airway obstruction due to laryngeal foreign bodies or pathology
These modern retroglottic devices represent a dramatic improvement over the esophageal obturator airway and the esophageal gastric tube airway of the 1970s and 1980s, which have no place in modern emergency airway management. A substantial advantage of the modern devices is that they do not require facility with BMV as did the obsolete devices.
Combitube
The Combitube (Fig. 10-20) has been in clinical use for a much longer period of time than any of the other RGDs and has therefore accumulated the largest body of evidence describing its indications, contraindications, benefits, and risks. This is an important factor that distinguishes the Combitube from the other devices, particularly as costs are compared.
The Combitube is a dual-lumen, dual-cuff, disposable airway intended to be inserted into the esophagus, although it can be accommodated by the trachea if it is inadvertently placed there, and will function adequately in the short term as an ETT. The Combitube is supplied in two sizes: 37F SA (small adult), to be used in patients 4 to 5.5 feet tall, and 41F, which is for use in patients more than 5.5 feet tall. There is no Combitube suitable for use in children less than 4 feet tall. In addition to the indications listed previously, use of the Combitube has been described in upper gastrointestinal or upper airway hemorrhage that threatens airway and tracheal patency and in a case of severe facial burns.
Insertion Technique
Insertion of the Combitube is a blind technique, although a laryngoscope may be used, permitting insertion under direct vision.
1. With the patient supine (insertion is possible in any position) and the head and neck in a neutral position, lift the tongue and jaw upward (“jaw lift”) with the nondominant hand.
2. Insert the device in the midline, allowing the curve of the device to follow the natural curve of the airway, and advance the device until the alveolar ridge is between the imprinted black bands on the device. Moderate force is required to enable the device to pass through the pharyngeal constrictor muscles into the esophagus. Substantial resistance should prompt the operator to withdraw and readvance. Inflate the proximal large oropharyngeal balloon with approximately 100 mL of air (Combitube 37F: 85 mL) via the blue pilot balloon labeled #1.
3. Inflate the white distal balloon with 5 to 15 mL of air (Combitube 37F: 5–12 mL) via the white pilot balloon labeled #2.
4. Begin ventilation using the longer blue connecting tube. The presence of air entry into the lung, the detection of end-tidal carbon dioxide, and the absence of gastric insufflation by auscultation indicate that the Combitube is in the esophagus, which occurs with virtually every insertion. The incidence of inadvertent tracheal intubation is less than 5%. Aspiration of gastric contents and gastric decompression is possible by passing the provided suction tube through the clear connecting tube into the stomach.
5. The absence of breath sounds in the chest, end-tidal carbon dioxide, and the presence of gastric insufflation by auscultation indicates that the Combitube is in the trachea (a distinctly rare event), and ventilation should be performed through the shorter clear connection tube.
6. The absence of any sounds on auscultation may indicate that the device has been inserted too far and should be repositioned after the proximal balloon is deflated.
Complications
The Combitube has been shown to be an effective airway management device that is easy to position properly. The Combitube appears in one study to be superior to the LMA Classic in the prehospital setting, and it has been shown to be a useful airway rescue device in the event of a failed intubation. However, like the LMA, it does not provide optimum protection against aspiration (although aspiration has never been reported), and its merit relative to the LMA Fastrach is unknown. Complications are rare and mostly related to upper airway hematomas, pyriform perforation, and perforation of the esophagus.
Increased cuff volumes are required at times to achieve a seal sufficient to permit adequate ventilation. As cuff volume is increased, the pressure transmitted to the mucosa is increased to the point where mucosal perfusion may be compromised, particularly where the cuff is adjacent to rigid anatomical structures such as the cervical spine (pharyngeal balloon) and the larynx (esophageal balloon). Over time, this may lead to ischemic mucosal injury. A high rate of success with few complications has been reported in prehospital use for cardiac arrest victims.
Finally, it should be noted that the pharyngeal balloon on the Combitube (as opposed to the Rusch EasyTube or the King LT airway) is made of latex.
Other Retroglottic Devices
The King LT airway
The King LT airway (King Systems Corp, Noblesville, IN; also known as the laryngeal tube airway, predominantly in Europe) (Fig. 10-21) is a newly developed multiuse (King LT) and disposable (King LT-D), latexfree, single-lumen silicon tube with oropharyngeal and esophageal low-pressure cuffs with a ventilation outlet between the two cuffs. It is supplied in blind distal tip and open distal tip variants to permit gastric decompression. A single pilot balloon is employed to inflate both balloons simultaneously, which is technically easier to use than the Combitube inflation system. However, it is also this feature that may lead to the fact that this device's airway seal capability is sometimes lost following insertion necessitating a deflation of the balloons and repositioning, a feature that is not common with the Combitube.
The device is available in pediatric and adult sizes in Europe; however, at the writing of this chapter, the pediatric-size devices were not available in the United States.
The King LT is inserted similarly to the Combitube, although there is usually less resis-tance on insertion. When seated, it works in a fashion that is very similar to that of the Combitube. Ventilation and oxygenation capabilities seem to be similar to the LMA and Combitube.
Rusch EasyTube
The Rusch EasyTube (Fig. 10-22) is a dual-lumen tube designed for difficult or emergency airway intubation and ventilation. It was approved for use in the European Union in 2003 and for use in the United States by the U.S. Food and Drug Administration in 2005. Like the Combitube, the EasyTube creates a viable airway, regardless of whether it is placed in the trachea or in the esophagus. When placed in the esophagus, the EasyTube allows the passage of a fiberoptic scope, a suction catheter, or a tracheal tube introducer through the more proximally terminating lumen. It is suggested by the manufacturer that the risk of tracheal trauma relative to the Combitube is reduced due to the single-lumen diameter of the device at the distal tip.
The EasyTube is supplied in only two sizes (28F and 41F) as opposed to the Combitube, which is supplied in 37F and 41F sizes. Again, the manufacturer claims that this allows the 28F EasyTube to be employed in older children. Finally, the EasyTube is latex free.
At present, there is little published evidence with respect to the indications, contraindications, success rates, and complications associated with this device. However, it has compelling design features that may make it useful as an airway rescue device similar to the Combitube and the King LT airway.
Evidence
Supraglottic Class
1. Is the LMA effective in difficult and failed airway management? There is ample evidence that LMAs are useful in emergency airway management, both for the management of the difficult airway and rescue of the failed airway (1,2,3,4,5,6,7,8,9,10,11,12,13), provided one is concurrently preparing to undertake a surgical airway.
2. What success rates have been achieved intubating through the LMA Fastrach? Success rates for blind intubation through the LMA Fastrach range from 70% to 95% (14,15,16), and coupling the device with a Trachlight produces success rates of 100% (17,18,19). Some studies have described the technique of coupling the LMA Fastrach or LMA Classic with a fiberscope to ensure intubation success in both infants and adults (20,21).
3. Is the LMA effective in the pediatric population? There is ample evidence that the LMA is appropriate and widely accepted as a rescue device in children (22,23,24,25). Some authors have described guidelines for selecting the appropriate size in children (23), and the manufacturer provides a pocket card to guide clinicians.
4. How easy is it for nonexperts to successfully use these LMA devices? A variety of authors have described successful insertion and use of the device by basic rescuer nonmedical personnel (26,27), paramedics, nurses, and respiratory therapists (28,29,30), and naive airway managers (28). Some of the EMS literature has questioned the ease of use of the device as a primary method of airway management in EMS (31), although analysis has shown that training is key to its successful use (31,32,33,34,35,36).
5. Are these devices acceptable airway management devices for patients undergoing cardiopulmonary resuscitation (CPR)? Numerous studies have demonstrated that the LMA (and Combitube) is at least as effective as other methods of airway management for patients requiring CPR (30,37).
6. Can the LMA fail to provide adequate ventilation, and what complications with short-term use might I expect? The LMA may fail to provide a seal sufficient to permit adequate ventilation, often attributed to the sensitivity of the seal to head and neck position (38,39,40). The head and neck should be neutral to slightly flexed, the tube of the LMA in the midline, and the natural anterior curve of the device maintained during ventilation (41). Insufflation of the stomach may occur (42). Although the LMA may not offer total protection from the aspiration of regurgitated gastric contents (43,44,45,46,47,48), it does offer protection from the aspiration of material produced above the device (49). This material that accumulates above the cuff of an ETT is suspected to be a major cause of ventilator-associated pneumonia in ventilated intensive care unit patients. Cricoid pressure may or may not interfere with proper functioning of an LMA (50,51), although in practice each case is evaluated individually. Negative-pressure pulmonary edema (mentioned previously) is caused by a patient sucking hard to inspire against an obstruction. Fluid is sucked into the alveolar spaces. This complication has been reported with patients biting down on the LMA (52) and can be prevented by placing folded gauze flats between the molar teeth on either side. This also serves to keep the device in the midline, enhancing the seal.
7. Are there any comprehensive reviews that I might find useful? Comprehensive reviews of the use of the LMA in emergency medicine and rescue airway management are available (53,54).
Retroglottic Class
1. What is the status of the Combitube with respect to its use as a rescue airway device? The Combitube has been identified as a rescue airway device for the failed airway by authoritative bodies in the United States and Canada (1,2). Its use is well described in the anesthesia, resuscitation, emergency medicine, and EMS literature both as a first-line device and as a device to be used in the face of a difficult or failed airway (55,56,57,58,59,60,61). Several authors have identified the Combitube as a valuable adjunct in CPR (62,63,64), performing as well as or better than the LMA and BMV.
2. What kind of airway management success rates have been reported with the Combitube? Success rates of 98% to 100% are regularly reported in these studies. The ease of insertion (65,66,67,68,69) and adequacy of ventilation by physicians and nonphysician providers is well established (70,71,72).
3. Has the Combitube been successful in the management of the difficult or failed airway? The device is useful in the management of the difficult airway (73) and in rescuing a failed airway (74,75,76) while one prepares to undertake a cricothyrotomy.
4. Has the Combitube been used in any unusual situations? It has been demonstrated to protect the airway, control bleeding, and permit ventilation in a case of craniofacial trauma associated with severe bleeding (77) and to secure an airway in a case of severe facial burns preventing intubation (78).
5. What precautions should I be aware of with this device? It is unclear whether the Combitube provides protection against the aspiration of gastric contents (79). The downside of the Combitube includes reports of potentially serious complications related to its use, particularly pyriform sinus perforation (80,81,82,83,84) and esophageal perforation (85,86,87,88,89). A word of caution: Mucosal pressures exerted by the inflated balloons may exceed mucosal perfusion pressure, leading to mucosal ischemia (90).
6. Has the King LT airway been demonstrated to be similarly effective in nonemergency airway management as the LMA and Combitube? Simple handling, possible aspiration protection, and availability in newborn to adult sizes are considered to be advantages of this airway device (91,92,93,94).
7. Does the King LT have a place in EMS as an airway management device? There is some evidence that this device is easily learned by EMS personnel and provides more effective ventilation than bag-mask devices (95,96,97).
8. Is the King LT airway useful as an emergency airway adjunct? The evidence that the King LT is useful as a rescue airway or in patients where intubation has failed is limited and for the most part is based on case reports (98,99,100). However, a recent publication provides compelling evidence that this device may well be of use in the difficult and failed airway (101).
9. Are there potential problems that I ought to be aware of with this device? As with the Combitube, mucosal compression by the inflated balloons may lead to mucosal ischemic injury (90,102).
References
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