A 57-year-old male was admitted for laparoscopic appendectomy for acute appendicitis. He was otherwise healthy, apart from essential hypertension, for which he took hydrochlorothiazide. He had fasted for more than 12 hours.

On examination, he was lying in a stretcher in a moderate amount of pain. He was hemodynamically stable. His height was 183 cm and his weight was 80 kg with a body mass index (BMI) 23.9 kg·m⁻². His airway examination demonstrated a Mallampati score of II, mouth opening of 4.5 cm, thyromental distance of 6 cm, and good jaw protrusion. He had a full set of teeth, was not obese, and was estimated to be easy to ventilate. His cardiac and respiratory examinations were normal.

The patient was premedicated with intravenous midazolam 1 mg, fentanyl 200 mcg, and this was followed by denitrogenation with 100% oxygen by facemask. As he didn’t have any indicators of a difficult airway, a decision was made to induce anesthesia with propofol 200 mg and rocuronium 50 mg. Bag-mask-ventilation (BMV) was established with an oral airway. Initial evaluation with direct laryngoscopy (DL) using a Macintosh laryngoscope showed a Cormack-Lehane (C/L) Grade 3 view. The first attempt with DL and an Eschmann Tracheal Introducer (ETI) resulted in an esophageal intubation. BMV was reestablished and a Glidescope^® was prepared. When the Glidescope^® was inserted, only the posterior arytenoids could be visualized, and two attempts with a styleted endotracheal tube (ETT) and a Tracheal Introducer were unsuccessful (and were associated with a small amount of bleeding in the oropharynx).

At this point, the decision was made to attempt flexible bronchoscopy. Unfortunately, BMV became more difficult, the patient’s oxygen saturation dropped into the low 80’s, and it became necessary to insert nasal and oral pharyngeal airways and begin a two-hand and two-person BMV technique. A #4 Laryngeal Mask Airway Classic^® (LMA Classic^®) was rapidly prepared and inserted without complication, at which point it became possible to easily ventilate the patient. Sevoflurane was selected to maintain anesthesia, and to manage escalating tachycardia and hypertension. A pediatric bronchoscope with an ensleeved Aintree Intubation Catheter (AIC, Cook Medical Inc., Bloomington, IN) was then inserted through the LMA into the trachea. Both the bronchoscope and the LMA were then removed leaving the AIC in the trachea. An ETT was advanced into the trachea over the AIC. Correct tracheal placement was confirmed by auscultation and capnograph recording.

The surgery was uneventful and the patient emerged from anesthesia fully awake, warm, with adequate analgesia, and with no residual neuromuscular blockade. The difficult airway cart was brought to the room. Tracheal extubation was uneventful, although he did complain of a sore throat in the post-anesthetic care unit, which gradually improved. He was later informed of the difficulty and provided with a notice to inform any subsequent practitioner of his difficult airway.

What are Extraglottic Devices? Why Do We Need These Devices?

Difficulties in airway management are associated with significant morbidity and mortality,¹ and it is crucial that practitioners responsible for airway management continue to refine existing skills, and acquire new knowledge and skills as they become available. Two decades ago, ventilation and oxygenation were achieved primarily via a facemask, or an ETT.

While BMV is seemingly simple to perform, it has limitations.^2,3 Tracheal intubation has been considered to be the “gold standard” for providing effective ventilation, while at the same time providing protection from the aspiration of gastric contents. However, tracheal intubation is a skill that is not easily mastered⁴ and requires regular practice. Employing an extraglottic device (EGD) to successfully facilitate gas exchange may be a more easily acquired skill for the nonexpert airway practitioner.

In contrast to a mask placed on the face to provide BMV, an EGD establishes a direct conduit for air to flow when placed in the periglottic area. The terminology has been somewhat confusing since some have referred to these devices as “supraglottic airway devices,” although many have components that extend infraglottically (e.g., the Combitube^®, the Laryngeal Tube^® [King LT in North America], and the Easy Tube).⁵ Hence, we agree with Brimacombe that the term “extraglottic devices,” or EGDs, is the more appropriate terminology.

EGDs vary in size, shape, and material. Most have balloons, or cuffs, that upon inflation can provide a reasonably tight seal in the upper airway. As illustrated in the case presentation, these EGDs (including the LMA Classic^®) have been used successfully as rescue airway devices. There is clear evidence of their effectiveness and safety in providing ventilation and oxygenation. These devices have changed the landscape of contemporary airway management. They are a part of the Difficult Airway Management Algorithm recommended by the American Society of Anesthesiologists (ASA),^6,7 the Canadian Airway Focus Group,^8,9 as well as the Difficult Airway Society¹⁰ in managing unanticipated difficult intubations in adults.

Do Manufacturing Standards Exist for EGDs to Ensure Patient Safety?

The American Society for Testing and Materials Standards (ASTM) Committee F29 on Anesthetic and Respiratory Equipment has proposed the establishment of standards related to EGDs used in human subjects. A task group has proposed the standardization of: terminology, design, production, manufacturing, testing, labeling, and promotion. Devices produced according to the proposed ASTM standards will:

• 
  

  Facilitate unobstructed access of respiratory gases to the glottic inlet by displacing tissue;

  
  
• 
  

  Not require a (external) facial seal to maintain airway patency;

  
  
• 
  

  Terminate in a 15/22 millimeter (mm) connector to facilitate positive pressure ventilation (PPV) via an anesthetic breathing system;

  
  
• 
  

  Be capable of maintaining airway patency when the (15/22 mm) airway connector is open to ambient atmosphere;

  
  
• 
  

  Minimize the escape of airway gases to the atmosphere.

What EGDs are Commercially Available?

Many EGDs have been introduced.⁵ The best known are the Laryngeal Mask Airway Classic^®, ProSeal^® Laryngeal Mask Airway (PLMA), Laryngeal Mask Airway Fastrach^® (LMA FT), LMA Supreme^® (LMA-S), and Combitube^® (CBT). Other EGDs such as the Laryngeal Tube^® (LT), CobraPLA^® (CPLA), Airway Management Device^® (AMD), LaryVent^® (LV), Air-Q^® device, Ambu^® AuraOnce Laryngeal Mask, Portex^® Soft Seal^® Laryngeal Mask, Streamlined Liner of the Pharynx Airway (SLIPA^®), and iGel^® are also gaining acceptance.

There are at least 25 different types of EGDs available.¹¹ This chapter will review the commonly used EGDs, which also have sufficient information available in the literature, but it should not be considered an exhaustive review of all available devices. It should be emphasized that some devices (e.g., the COPA and PAxpress™) are no longer being manufactured, and so they would not be discussed in this chapter.

What Is the LMA? When Was It Introduced?

The LMA^® (Teleflex^®, Morrisville, NC [Figure 13–1]) was designed in 1981 by Dr. Archie Brain, as he searched for a device that was easier to use and more effective than the face mask, and less invasive than a ETT. The LMA is designed to cover the periglottic area and provide continuity of airflow between the environment and the lungs. The device has a wide-bore tube connecting to an oval inflatable cuff that seals around the larynx. It is currently available in eight different sizes for use in patients ranging from neonates to large adults. Typically, a #3 LMA-Classic is used in teenagers and small adult females, while #4, #5, and #6 are used in average and large size adults.

The use of LMAs has transformed the practice of anesthesiology and airway management.^12,13 The LMA is specified in the ASA’s Difficult Airway Management Algorithm.^6,7 Moreover, the LMA has a role in emergency airway management during cardiopulmonary resuscitation (CPR), the transport of the critically ill patient, and in the intensive care unit.^14,15 Although the LMA is a potentially useful device in situations in which tracheal intubation and mask ventilation are not possible (e.g., “can’t intubate, can’t ventilate” [CICV], or more appropriately “can’t intubate, can’t oxygenate” [CICO]),^6,7,9 it should never be used as a substitute for a surgical airway (see Chapters 2). While this device can provide adequate ventilation and oxygenation, it does not protect the airway from aspiration, and it does not easily allow for the removal of pulmonary secretions. Therefore, when employed as a rescue device, the LMA can only be considered a temporizing measure, until a more definitive and protective airway is secured.

What Is the Proper Way to Insert the LMA?

While many techniques have been suggested for the insertion of the device, including the midline approach, the lateral approach, and the thumb technique,¹⁶ the authors recommend the following steps:

• 
  

  To minimize the risk of down-folding the epiglottis, it is recommended that the cuff be completely deflated.

  
  
• 
  

  The LMA cuff should be 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. A head tilt will help to open the mouth.

  
  
• 
  

  In order to have 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 nondominant hand. This lifts the tongue and epiglottis away from the posterior pharyngeal wall to facilitate placement of the LMA. The LMA should be inserted into the mouth with the index finger placed at the mask-tube junction, pressing the cuff against the hard palate, and advancing the LMA into the oropharynx following the natural curve of the posterior pharyngeal wall. The dimensions and design of the device allow the tip of the LMA to wedge into the hypopharynx. A definite resistance should be felt when the tip of the LMA enters the hypopharynx. Occasionally, resistance is encountered during insertion because of backward folding of the cuff (also called ‘tip roll’). Sweeping a finger behind the cuff to redirect it inferiorly into the laryngopharynx can usually overcome this problem.¹⁷

  
  
• 
  

  Following placement, the cuff should be inflated with the minimal volume of air necessary to achieve an adequate seal. However, this “just-seal” volume may not be adequate to seal the hypopharynx from the esophagus.¹⁶ Therefore, most practitioners commonly inflate the cuff with more volume. In general, approximately 20 mL is required for #3, 30 mL for #4, and 40 mL for #5 LMA. Seal characteristics may be improved by ensuring that the LMA is secured in the midline of the mouth, and the head and neck placed in a neutral position.

  
  
• 
  

  The LMA should be fixed in position by taping it to the face, or by attaching it to the anesthesia breathing circuit.¹⁸

What Is the Proper Way to Remove the LMA?

In its normal position, the LMA is less stimulating than an ETT and is generally well tolerated by most patients on emergence. Many studies have compared removal under deep anesthesia versus while awake. Although airway obstruction appears to be less frequent if the device is removed with the patient awake, this technique is associated with more coughing, laryngospasm, biting, and hypersalivation.¹⁹ While much controversy remains, it is the opinion of the authors that, in adults, the LMA should be removed awake. This is particularly true if mask ventilation is expected to be difficult. Many pediatric airway practitioners prefer removal under deep anesthesia, as children are more prone to laryngospasm.

It is unclear whether the LMA should be removed with the cuff deflated or inflated. Some recommend an inflated cuff because of its capacity to remove secretions that accumulate above the device from the oral cavity.²⁰ Others argue that the cuff should be deflated to minimize trauma and damage to the cuff itself. Brimacombe recommends the removal of the LMA with the cuff partially deflated.¹⁹

What Are the Advantages and Disadvantages of Using the LMA as Opposed to an Endotracheal Tube?

Brimacombe conducted a meta-analysis of randomized prospective trials involving 2440 patients comparing the LMA with other forms of airway management, including tracheal intubation.²¹ He reported many advantages of the LMA including: rapidity and ease of placement, particularly for inexperienced operators; improved hemodynamic stability on induction and during emergence; minimal rise in intraocular pressure following insertion; reduced anesthetic requirements for airway tolerance; lower frequency of coughing during emergence; improved oxygen saturation during emergence; and a lower incidence of sore throat in adults.

An additional advantage of the LMA is its utility as a rescue device and during resuscitation.²² Further, studies have shown that the LMA has less impact on mucociliary clearance than an ETT, and may reduce the risk of retention of secretions, atelectasis, and pulmonary infection.²³

The major disadvantage of the LMA is its inability to seal the larynx and protect against aspiration, gastric insufflation, and air leak with PPV.²¹ The mask is designed in such a way that the distal end of the device is intended to become wedged into the upper esophageal sphincter. However, in reality, the distal end may lie anywhere from the nasopharynx to the hypopharynx.

The magnitude of potential gastric insufflation probably depends on the airway pressure generated and the position of the LMA. However, very large series have shown that PPV with the LMA is both safe and effective, with no episodes of gastric dilatation in 11,910 LMA anesthetics under both spontaneous and PPV.²⁴

According to a meta-analysis involving 547 LMA publications, the incidence of gastric aspiration associated with the use of laryngeal mask airway is rare (0.02%),²¹ and most of these cases had predisposing risk factors for pulmonary aspiration. However, fatal aspiration of gastric content has been reported,²⁵ and so proper assessment for aspiration risk prior to the use of the LMA is imperative. Most airway practitioners hesitate appropriately to use the LMA in patients with a history of symptomatic hiatal hernia, gastroesophageal reflux, in obstetrical patients, or in patients with a bowel obstruction. Careful placement of the device, and vigilance at emergence of anesthesia, may attenuate the risk of gastric aspiration.

Is It Safe to Use the LMA for Positive Pressure Ventilation?

Over the last two decades, the use of a face mask to facilitate the administration of anesthesia has largely been replaced by the LMA. While a few studies have reported the successful use of the LMA for PPV in a variety of patient populations and procedures,^26–28 they involved mostly small numbers of patients, with few large prospective randomized trials.²⁹ Bernardini and Natalini³⁰ compared the risk of pulmonary aspiration, in a study involving 65,712 patients, with PPV via an ETT (30,082 procedures) compared to an LMA (35,630 procedures). Although three pulmonary aspirations occurred in the LMA group compared to seven with the ETT, there were no deaths related to these pulmonary aspirations. The investigators concluded that, while there was a selection bias related to contraindications and exclusions to the use of the LMA in their study group, the use of a laryngeal mask airway was not associated with an increased risk of pulmonary aspiration, compared with an ETT in this selected population.

Based on the current evidence, the LMA appears to be effective and probably safe for PPV in patients with normal airway resistance and compliance and normal tidal volumes. However, gastroesophageal insufflation may occur when the LMA is used in conjunction with, and in the presence of, decreased pulmonary or chest wall compliance.^31,32

Pressure-controlled ventilation (PCV), rather than volume-controlled ventilation (VCV), may provide effective mechanical ventilation in patients with high airway pressure, or reduced lung compliance, while at the same time minimizing the risk of gastric insufflation with the LMA.³³ It must be reemphasized that, although rare, cases of serious and even fatal gastric aspiration associated with the use of LMA have been reported.^25,34–36 Because of the potential for serious complications, more evidence with studies involving a large number of patients may be needed to confirm the safety of the use of the LMA for PPV.²⁹

How are LMAs Used Appropriately in Clinical Practice?

Since its introduction in 1988, the LMA has been used in more than 200 million patients worldwide,¹³ and it has largely replaced the ETT and face mask for patients undergoing simple and uncomplicated surgical procedures. The extensive use of the LMA is a reflection of its overwhelming effectiveness and safety in a variety of age groups and surgical procedures. The LMA has also been shown to be effective and safe for elective caesarean section in non-obese parturients, though its use for this indication is controversial.³⁷

A meta-analysis of currently available data shows that the LMA is safe and effective for pediatric airway management.³⁸ Furthermore, the LMA has been used successfully in the management of large numbers of difficult pediatric airways associated with a variety of congenital anomalies. In 2010, Weiss and Engelhardt³⁹ proposed the use of LMA in the management of the unexpected difficult pediatric airway algorithm.

The LMA was approved for resuscitation by the European Resuscitation Council in 1996,⁴⁰ and the American Heart Association (AHA) in 2000.⁴¹ However, the possibility of gastric insufflation, related to high peak airway pressure, continues to be a concern in these patient populations, similar to those managed with BMV.

Brimacombe summarized the available evidence with respect to the use of the LMA in the management of the difficult and failed airway.⁴² With the exception of airway pathology that may interfere with the LMA placement or seal, there is a considerable body of evidence to support the use of the LMA in both predicted and unpredicted difficult airways.^6–9

The LMA also provides a conduit for tracheal intubation using either a blind technique, a transillumination technique (using the Trachlight^® without the stiff wire stylet),^43,44 or a flexible bronchoscope (FB) together with an AIC (Cook Medical Inc., Bloomington, IN).^45,46 Intubation success rates through the LMA have been found to be similar for patients with both normal and abnormal airways.⁴⁷

The FLMA^® was specifically designed for use in ear, nose and throat, head and neck, and dental surgery. It has been used for adenotonsillectomy,⁴⁸ laser pharyngoplasty,⁴⁹ and dental extraction.⁵⁰ The device consists of a Classic LMA bowl connected to a floppy, wire-reinforced tube with a slightly narrower bore than the LMA Classic^®. The long, flexible, narrow bore tube provides better surgical access to the oropharyngeal cavity than the standard laryngeal mask airway. The technique for placement of the FLMA is similar to that for the LMA.

The reusable LMA Classic^® is the original LMA. Variations on the original include:

• 
  

  LMA Fastrach^®, also known as the Intubating LMA (ILMA), and also available in a disposable form (Figure 13–2);

  
  
• 
  

  LMA Flexible^®, similar in design to the Classic, but incorporating a non-kinkable, wire-reinforced tube;

  
  
• 
  

  LMA ProSeal^®, a second-generation EGD that has improved seal characteristics and incorporates a gastric drainage capability (Figures 13–3 and 13–4);

  
  
• 
  

  LMA Unique^®, a single use device virtually identical to the Classic (Figure 13–5);

  
  
• 
  

  LMA Supreme^®, a disposable second-generation EGD that incorporates the insertion advantages of the Fastrach^®, with the seal and drainage characteristics of the ProSeal^® (Figure 13–6).

  
  
• 
  

  LMA Protector, a new disposable second-generation silicone EGD that also incorporates the insertion advantages of the Fastrach^®. It has two drainage channels, which emerge as separate ports proximally. It also has a built-in bite block to reduce the risk of obstruction of the airway tube in the event of biting (Figure 13–7).

What Is the LMA Fastrach^®, or Intubating LMA (ILMA), and Why Was It Developed?

While it is possible to intubate the trachea through an LMA, success rates are variable. The intubating LMA (LMA Fastrach^®, or Intubating LMA [ILMA], Teleflex^®, Morrisville, NC [Figure 13–2]) was designed by Dr. Brain. The device has a rigid metal curved airway tube with a guiding handle, an epiglottic elevating bar, a deeper bowl, and ramp that directs an ETT up and into the larynx. The device is easy to use, is associated with high success rates of intubation, and has received widespread acceptance. The ILMA is a reusable device, which can be cleaned and sterilized using an autoclave. Single use ILMAs are also available.

How Is Tracheal Intubation Performed Using the ILMA?

Tracheal intubation through the ILMA can be achieved blindly. To facilitate the insertion of an ETT through the ILMA, the following steps are recommended:

• 
  

  Lubricate the ILMA and the ETT (including the connector of the tracheal tube) with a water-soluble lubricant. Ensure that the ETT slides easily through the ILMA.

  
  
• 
  

  With the patient in a sniffing position, open the airway by using a head tilt. It should be emphasized that the insertion of an ILMA may be difficult if the inter-incisor gap is less than 20 mm.

  
  
• 
  

  Grasp the metal handle of the ILMA and insert the device straight back over the tongue to the back of the oropharynx. Then, advance the cuff into the hypopharynx following the palatopharyngeal curve by rotating the device using the metal handle and maintaining gentle pressure against the palate. Once in place, inflate the cuff to achieve a seal for manual ventilation. The metal handle may be used to manipulate the device to achieve a seal to ensure adequate ventilation and oxygenation. The device should be gently rotated in the sagittal plane (commonly known as the “first” Chandy Maneuver) to establish optimally unobstructed ventilation.⁵¹

  
  
• 
  

  While a number of ETTs, including the Mallinckrodt Hi-Lo PVC tube^®, can be used for tracheal intubation, the dedicated wire-reinforced silicone-tipped ETT supplied with the ILMA has been shown to give the highest success rates.⁵² With the black vertical line on the tube facing the practitioner, insert the tube into the metal lumen of the ILMA until the horizontal black line on the tracheal tube meets the proximal end of the ILMA metal tube (see Figure 13–2). At this point, the tip of the silicone-tipped ETT is just emerging from beneath the epiglottic elevating bar. Resistance will be felt as the silicone-tipped ETT elevates this bar exiting the distal end of the ILMA, and entering the patient’s glottis.

  
  
• 
  

  Tracheal placement is confirmed in the usual manner. Manipulation of the ILMA by lifting the device from the posterior pharyngeal wall using the metal handle (the “second” Chandy maneuver) may enhance successful passage in the event of failure. This maneuver helps to prevent the silicone-tipped ETT from colliding with the arytenoids and minimizes the angle between the aperture of the ILMA and the glottis.⁵³

Some evidence suggests that the ILMA in situ produces sufficient pressure on the posterior hypopharyngeal wall to potentially compromise mucosal blood flow.⁵⁴ For this reason, except perhaps in an airway rescue or resuscitation situation, it is recommended that the device be withdrawn over the ETT. A stabilizing rod is provided with the ILMA to hold the ETT in position while the ILMA is withdrawn.

Many investigators have studied the effectiveness of the blind intubating technique through the ILMA. The reported mean (range) first-time and overall success rate is 73% (53–100) and 90% (44–100), respectively.⁵⁴ Several factors that decrease success rates of blind intubation through the ILMA technique have been identified: the use of a #3 ILMA, instead of#4 or #5 ILMA, for adult male patients; the application of cricoid pressure; lifting the ILMA handle; the use of a collar; and an inexperienced practitioner.

What Other Techniques Have Been Described to Enhance Success Rates for Tracheal Intubation Through the ILMA?

Several studies have been published evaluating the effectiveness of a laryngoscope to assist ILMA intubation. The overall success rate appears to be no better than the blind technique. Light-guided techniques employing a flexible lightwand (Trachlight^®) have also been investigated, and have demonstrated improved success rates.^55,56 Lightwand-guided intubation through the ILMA has a first-time and overall success rate of 84% and 99%, respectively.⁵⁴ Several researchers have shown high success rates with a lightwand-guided tracheal intubation through an ILMA.^57,58

Pandit et al.⁵⁹ found that bronchoscopic-guided intubation had a higher success rate (95%) through the ILMA than through the LMA (80%), although the time to intubation was longer with the FB-assisted technique, compared to the blind technique (74 seconds vs. 49 seconds). Overall, in a range of studies, FB-guided intubation through the ILMA has a first time and overall success rate of 87% and 96%, respectively. However, following a failed blind technique, flexible FB-guided intubation through the ILMA has a success rate of only 86%.⁵⁴

Agro et al.⁶⁰ reported the use of a shorter semi-rigid fiberoptic device, the Shikani Seeing Eye Stylet^® (Clarus Medical, Minneapolis, MN), to facilitate an ILMA intubation. Although tracheal intubation was successful, the investigators commented that the major limitation of the Shikani device was its inability to control the direction of the tip of the device.

Using the Patil Intubation Guide^® (Anesthesia Associates Inc., San Marcos, CA), a whistle diaphragm to detect breath sounds, Osborn⁶¹ successfully intubated the trachea through the ILMA under topical anesthesia in a patient with a recent cervical spine fusion. In 2005, a case series was published describing the successful use of the airway whistle with the ILMA in four patients with known difficult airways.⁶²

What Are the Indications for the ILMA?

The ILMA alone does not prevent the aspiration of gastric contents, and may produce hypopharyngeal mucosal ischemia if it is left in place for a prolonged duration. Therefore, its role in routine airway management may be limited. However, when used as a temporizing measure, it is a highly effective device in the emergency environment, as an adjunct to a failed or difficult BMV, and as a rescue device in the failed airway. Brain has suggested that the ILMA may not be indicated when the patient is anticipated to be an easy intubation (easy DL), but may be of considerable benefit when the glottis is high and anterior (difficult DL). Furthermore, studies have confirmed earlier findings that ventilation and intubation through the LMA Fastrach^® can be successfully achieved in obese patients.^63,64

With respect to Emergency Medical Services (EMS) and prehospital care, the importance of early and effective airway control is universally acknowledged. Tracheal intubation under DL is associated with a number of practical problems in pre-hospital trauma, and there is evidence to suggest that the ILMA may play an important role in the pre-hospital setting, in securing the airway of trauma patients with a head injury.^65,66

Gercek et al.⁶⁷ compared the degree of cervical spine movement of three common methods of tracheal intubation in patients with c-spine injuries (DL, ILMA, and FB) using real-time, three-dimensional ultrasonography in healthy elective surgical patients with manual in-line immobilization. They showed that manual in-line immobilization reduced the cervical spine range of motion during different intubation procedures to a limited extent: the least diminution (i.e., the greatest c-spine movement) occurred with DL (with an overall flexion/extension range of 17.57 degrees), versus significantly less c-spine movement with ILMA use (overall flexion/extension range of 4.60 degrees) and FB use (overall flexion/extension range of 3.61 degrees—oral, 5.88 degrees—nasal). Furthermore, the mean (± SD) total time required for intubation was shortest for the ILMA (16.5 ± 9.76 seconds), followed by DL (27.25 ± 8.56 seconds), and the longest for both FB techniques (oral: 52.91 ± 56.27 seconds, nasal: 82.32 ± 54.06 seconds).

The prime role of the ILMA lies in managing the airway of patients with a difficult or a failed airway. From a retrospective study involving 254 patients with difficult airways, including patients with C/L Grade 4 views, immobilized cervical spines, stereotactic frames, or airways distorted by surgery or radiation therapy, the clinical experience with the ILMA (both elective and emergency use) has been largely positive.^53,68

The Difficult Airway Society (United Kingdom) guidelines for management of the unanticipated difficult tracheal intubation in the non-obstetric adult patient without upper airway obstruction include the ILMA.^10,69

What Is the PLMA? How Does It Differ from the LMA?

The PLMA^® (Teleflex^®, Morrisville, NC [Figure 13–3]) is a “second-generation” laryngeal mask airway that incorporates several modifications to the LMA:

• 
  

  An esophageal conduit is incorporated to provide access to the esophagus and the gastrointestinal tract to minimize the risk of aspiration. This incorporated conduit renders a “dual tube” look to the device.

  
  
• 
  

  A second cuff on the “dorsal” aspect of the PLMA is intended to enhance the seal characteristics of the device.

  
  
• 
  

  The PLMA lacks mask aperture bars, and (like the ILMA) has a deeper bowl which makes the migration of the epiglottis into the distal lumen of the device less likely.

  
  
• 
  

  The PLMA also has a flexible wire-reinforced airway tube to improve flexibility and minimize kinking, and a bite-block to reduce the danger of bite-induced airway obstruction, or tube damage.

The drainage conduit traverses the bowl of the cuff on its way to the upper esophagus, in an effort to reduce the risk of gastric insufflation when positive pressure is applied to the airway. Standard gastric tubes (≤18 French [Fr] gauge) can be accommodated by the conduit to facilitate gastric decompression. An accessory vent under the drain tube is intended to prevent the pooling of secretions and can act as an accessory ventilation port.⁷⁰

Employing moderate force to advance the laryngeal cuff forward into the periglottic tissues may improve the airway seal. The dual tube arrangement seems to reduce the incidence of accidental device rotation during anesthesia. This feature enhances the ability to secure the device in position giving greater confidence for use in longer procedures.

How Is the PLMA Placed?

The technique of insertion of the PLMA is similar to that of the LMA. While there is no randomized controlled study comparing the placement technique of the PLMA, with or without a muscle relaxant, it has been shown that successful placement of the PLMA requires deeper anesthesia when compared with the LMA.^71,72

Three insertion techniques for the PLMA have been advocated:

• 
  

  The Introducer Assisted Insertion Technique: Prior to its placement, the PLMA is loaded onto an introducer by placing the distal end of a metal introducer in an “insertion strap” on the PLMA (Figure 13–4). The airway tube is folded around the introducer and “fitted” into a proximal matching slot. The head and neck of the patient should be placed in a sniffing position. Following the placement of the PLMA, the introducer is removed as the PLMA is held in position.

  
  
• 
  

  The Digital Technique: Similar to the LMA, the digital technique involves the placement of the index finger under the insertion strap during the insertion of the PLMA. Rotating the PLMA 90 degrees in the mouth until resistance is felt at the hypopharynx was found to be more successful and associated with a decrease in blood staining on the device, and in the incidence of sore throat.⁷³

  
  
• 
  

  The Tracheal Introducer-guided Insertion Technique: This is probably the most reliable technique to optimally place the tip of the PLMA cuff in the hypopharynx.⁷⁴ A well-lubricated tracheal introducer (e.g., an ETI) is placed into the esophagus under direct vision with a laryngoscope. The PLMA is guided into position by placing the tracheal introducer through the esophageal conduit. While this technique enjoys a high success rate, it is time consuming, and probably more stimulating and traumatic.

In a study by Eschertzhuber et al.,⁷⁵ these three insertion techniques were compared in patients with simulated difficult laryngoscopy using a rigid neck collar. Insertion was more frequently successful with the ETI technique at the first attempt (ETI—100%, digital—64%, Introducer Assisted Technique—61%). The time taken for successful placement was similar among groups on the first attempt. However, it was shorter for the ETI technique after three attempts (ETI—31 ± 8 s, digital 49 ± 28 seconds, Introducer Assisted Technique 54 ± 37 seconds).

Proper placement of the PLMA can be confirmed by a number of techniques. Air leak through the drainage tube at low airway pressures suggests malposition of the PLMA. Although 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.⁷⁶ Three other tests have been suggested to check the patency of the drainage tube, including: passing a gastric tube though the drainage tube; passing a FB through the drainage tube; and performing a suprasternal notch tap while observing a soap bubble, or lubricant, at the proximal end of the drainage tube.⁷⁷

What Are the Advantages of the PLMA^®, Compared to the LMA^®?

In principle, the PLMA would be expected to reduce the aspiration risk when compared to the LMA. Laboratory (and cadaver) evidences are supportive of the theoretical efficacy of the PLMA.⁷⁸ However, clinical evidence is lacking, largely because the incidence of aspiration of gastric contents with the LMA is so low (0.02%), and a randomized controlled clinical trial with a large patient population is needed. Aspiration of gastric contents has been reported with the PLMA, and malposition of the PLMA has been identified as a cause of the aspiration.⁷⁹

The design of the PLMA cuff significantly improves airway seal when compared to the LMA. The larger, softer, wedge-shaped PLMA cuff enables the anterior cuff to better adapt to the shape of the pharynx.⁷⁸ Most believe that pressure exerted on the pharyngeal mucosa by the cuffs of LMAs is the cause of sore throat seen with the device. Compared to the LMA, PLMA intra-cuff pressures are lower and airway seal pressure higher for any given intracuff volume.⁸⁰ Moreover, pressure exerted on the hypopharyngeal mucosa has been found to be below that considered critical for mucosal perfusion.

Perhaps the greatest limitation of the use of the LMA in small children is that the seal is often inadequate for PPV, even at high intracuff pressures. This does not appear to be as significant a limitation when the PLMA is used in these patients. Multiple studies comparing PLMA and LMA in children showed that first time insertions of PLMA were more successful, had less gastric insufflation, and produced a better seal to allow for PPV compared to the LMA.^81–88

What Are the Disadvantages of the PLMA^®?

It is generally felt that the PLMA is more difficult to place than the LMA. The success rate for first time PLMA insertion is lower than the first time insertion success rate for the LMA (average success rate of 85% with a range from 81% to 100% for the PLMA vs. average success rate of 93% with a range of 89% to 100% for LMA).⁷⁸ It is possible that the insertion difficulty may, in part, be related to the larger, deeper, and softer cuff of the PLMA. It has been suggested that 20 to 30 insertions of the PLMA are required before competency is achieved.⁷⁸

What Are the Potential Clinical Uses of the PLMA?

The improved airway seal characteristics and touted lower risk of gastric aspiration with the PLMA, compared to the LMA, has expanded its applicability to surgical procedures that would not have been considered safe had an LMA been employed. These procedures include laparoscopy,⁸⁹ open abdominal surgery, surgery in patients with obesity, and in patients with gastroesophageal reflux.⁷⁸ A study by Hohlreider et al.⁹⁰ demonstrated less postoperative nausea, vomiting, airway morbidity, and analgesic requirements for the PLMA than the tracheal tube in females undergoing breast and gynecological surgery.

The PLMA has been used to provide ventilation and oxygenation in patients with a history of difficult laryngoscopic intubation.⁹¹ A number of investigators reported the successful use of the PLMA to rescue a failed airway in obstetrical patients after a failed intubation.^92–95

What Is the LMA Supreme^® and What Is Its Clinical Utility Compared the PLMA^®?

The LMA Supreme^® (Teleflex^®, Morrisville, NC) is a disposable, latex free, LMA device with a drainage tube (Figure 13–6). It was designed to combine the desirable features of both the Intubating LMA (ease of insertion, because of the rigid anatomically shaped airway tube made of medical grade polyvinyl chloride) and the PLMA^® (higher seal pressures and gastric access).⁹⁶ The cuff of the LMA Supreme (LMAS) is designed to provide higher seal pressures than the LMA-Classic^® or Unique^®. In an early clinical study involving 70 patients, Ali et al.⁹⁷ reported that the LMAS is superior to the LMA Classic because of its ease of insertion, with low cuff pressure and high oropharyngeal leakage pressure. However, several clinical studies comparing the LMAS and PLMA reported conflicting findings.^96,98,99 While both Verghese and Ramaswamy⁹⁶ and Hosten’s et al.⁹⁸ studies reported that both LMAS and PLMA had similar leak pressures, Lee et al.⁹⁹ found that the oropharyngeal leak pressure and the maximum achievable tidal volume are lower with the LMAS than with the PLMA. However, there was no difference in the efficacy in ventilation and safety between the LMAS and PLMA in these studies.

Because of the ease and speed of successful insertion, higher glottic seal pressures, and ability to access gastric contents, Verghese and Ramaswamy⁹⁶ suggested that the LMAS may have a role in airway management in CPR, and in the “cannot-intubate, cannot-ventilate” (more recently called “cannot-intubate, cannot oxygenate”⁹) scenario, the ASA Practice Guidelines recommended for the LMA Classic.^6,7,100

What Is the LMAP? How Does It Differ from the LMA Proseal^®?

The LMA Protector™ is a newly introduced single use, silicone second-generation EGD (Figure 13–7).¹⁰¹ Similar to the LMA Proseal^®, the LMAP provides access to, and functional separation of, the respiratory and digestive tracts. The LMAP has two separate proximal drainage ports (a male suction port and a female drainage ports), which have drainage channels that run distally into a chamber behind the cuff bowl. The chamber then narrows distally into the opening located at the tip of the cuff which communicates closely with the upper esophageal sphincter. While a suction tube may be attached to the male suction port, a well-lubricated gastric tube may be passed through the female drainage port to the stomach. The manufacturer claimed that the drainage channel can be used as a monitor of correct positioning of the device following insertion, as well as providing continuous monitoring of mask displacement during use.

It has an anatomically shaped airway tube similar to that of the LMA Unique^®. Therefore, unlike the LMA Proseal^®, the LMA Protector'” provides easy insertion without the need for digital or introducer tool guidance as discussed above. It also has a built-in bite block to minimize the risk of the airway tube occlusion in the event of biting.

What Is the Clinical Utility of the LMAP?

Since it shares many characteristics of the LMA Proseal^® and LMA Unique^®, the clinical applications of the LMAP would likely be similar to these two second-generation EGDs. However, at the time of writing this chapter, there is no information available regarding its effectiveness and safety in providing ventilation and oxygenation in patients. Furthermore, there is also no information available regarding the suitability for tracheal intubation via the LMAP.

What Is CBT and How Does It Differ from the LMA?

The CBT (Tyco-Healthcare-Kendall-Sheridan, Mansfield, MA [Figure 13–8]) is an easily inserted and highly efficacious EGD. It is specified in the ASA Difficult Airway Algorithm as a primary rescue device in CICO situations.^6,7,100 It also has been used successfully during CPR and in trauma patients.^102–108

The CBT is a double-lumen airway, one of which is open at both ends, as with a normal ETT. The other consists of an open proximal lumen and a distal blocked lumen, which resembles an esophageal obturator airway. The device has two balloons designed to trap the glottis between them. An oropharyngeal balloon is designed to be positioned just behind the posterior part of the hard palate. Once inflated, this balloon presses the base of the tongue in a ventro-caudal direction and the soft palate in a dorso-cranial direction, sealing the oral and nasal airways from behind. Another smaller cuff seals the esophagus once inflated. Perforations between the two balloons in the distally blocked lumen permit the egress of air or oxygen when PPV is applied to a proximal port. Two circumferential rings printed on the proximal end of the tube indicate that the device has been inserted to the proper depth when the upper teeth or alveolar ridges are situated between these two marks. The CBT is available in two sizes: the CBT 37F SA (Small Adult), to be used in patients 4 to 6 feet in height (approximately 120−180 cm); and the CBT 41F, for patients taller than 6 feet (approximately >180 cm).

How Is the CBT Inserted?

Insertion is facilitated by bending the CBT between the balloons for a few seconds before insertion to mimic the curvature of the pharynx. It is made more pliable if heated to body temperature, perhaps attenuating its blunt trauma potential. Placement of the CBT is most readily performed with the patient’s head placed in a neutral position,¹⁰⁷ although some practitioners prefer slight extension or flexion. The classical sniffing position is usually not helpful. In the fully awake patient, sedation and topical anesthesia are necessary to ensure that the patient does not react to the insertion. To elevate the tongue and epiglottis, a jaw lift is performed by grasping the lower jaw with the thumb and forefinger. The CBT is inserted blindly along the surface of the tongue with initial gentle downward, curved, dorso-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 edentulous patients. After insertion, the oropharyngeal balloon of the CBT 37F is inflated with 85 mL of air through a blue pilot balloon. The corresponding filling volume for the CBT 41F is 100 mL. Then, the distal balloon is inflated with approximately 10 mL of air.

With blind insertion, the CBT is successfully placed in the esophagus in more than 95% of cases. Ventilation is achieved via the longer blue connector (No. 1), leading to the blocked lumen that contains perforations at the level of the larynx, between the two balloons. The trachea is effectively ventilated because the nose, mouth, and esophagus are sealed by the two balloons. The second “tracheoesophageal” lumen of the CBT can be used for decompression of the esophagus and stomach, thereby minimizing the risk of aspiration.

Auscultation of breath sounds over the chest, the absence of gastric insufflation, end-tidal CO₂ detection, and esophageal detection devices can all assist in the confirmation of correct positioning.^109,110

Should the CBT enter the trachea on blind insertion, it can function like a standard ETT and there will be no need for inflation of the pharyngeal cuff. Ventilation can be achieved through the shorter, unobstructed clear tube (No. 2) leading to the tracheal lumen.

Although it is rare, ventilation may be impossible through either the proximal or distal lumen. This usually signifies that the CBT has been placed too deeply, with the obturator lumen positioned in the esophagus and the oropharyngeal balloon obstructing the entrance to the larynx. After deflation of the balloons, the CBT should be withdrawn approximately 2.0 to 3.0 cm. While the CBT may be inserted blindly, the use of a laryngoscope is recommended whenever possible.

What Are the Advantages of the CBT, Compared to the LMA?

The CBT was designed primarily for use in CPR,^104,105 even by nonmedical personnel. It has been demonstrated to permit effective ventilation during routine surgery, as well as in the ICU.¹⁰³ Most believe that the principal role of the CBT is in emergency airway control when tracheal intubation is not immediately possible.^111–114 The CBT may be kept in situ for up to 8 hours and allows controlled mechanical ventilation at inflating pressures as high as 50 cm H₂O (see aspiration potential below). The CBT can be replaced by deflation of the oropharyngeal balloon and insertion of an ETT either under DL, or by indirect view using a FB placed anterior, or lateral to the CBT.

Several case reports describe the successful use of the CBT in cases of unanticipated difficult airways.^115–117 Thus, it is not surprising that the ASA task force on difficult airway management lists the CBT, along with the LMA and transtracheal jet ventilation, as CICO (formerly called CICV) rescue methods.^6,7,100 Consequently, the CBT should be part of a portable kit for the management of difficult airways.

A major advantage of the CBT over conventional tracheal intubation is that the device can be inserted with the head and neck in a neutral position. Additionally, it requires only modest mouth opening for insertion, and its tubular profile permits insertion in situations that cannot be negotiated by more bulky devices. The CBT can be inserted from a variety of angles, making it useful in awkward environments (e.g., a patient who is trapped in a vehicle). The CBT may be of special benefit in patients with massive bleeding or regurgitation, when visualization of the vocal cords is impossible. While protection from aspiration is not absolute, the CBT may be more effective than the LMA Classic^® in this regard, due to much higher sealing pressures.¹¹⁸

What Are the Disadvantages of the CBT?

The CBT was not designed to replace other devices for routine surgery. While the esophageal cuff offers some protection against the reflux of gastric contents into the periglottic area, the level of protection against aspiration does not approach that of a cuffed ETT.

The suctioning of tracheal secretions is very difficult when the CBT is in the esophageal position. To address the issue of secretions and suctioning, Krafft et al.¹¹⁹ proposed a modification in the CBT, in which the two anterior, proximal perforations of the CBT are replaced by a single, larger, ellipsoid-shaped hole that allows for fiberoptic access of the trachea, tracheal suctioning, and tube exchange over a guide wire. It should be noted that FBs (e.g., Storz, Tuttlingen, Germany) with a small outer diameter (3.0 mm OD) allow passage through the unmodified pharyngeal perforations.

Contraindications to the use of the CBT include: an intact gag reflex, airway obstruction by foreign bodies, tumors, or swelling, the presence of known esophageal disease, and the prior ingestion of caustic substances.

Complications associated with the use of CBT have been reported.^120,121 In a retrospective study of 1139 patients requiring resuscitation using the CBT, four cases of subcutaneous emphysema, pneumomediastinum, and pneumoperitoneum associated with the CBT during prehospital management were reported.¹²¹ The reason for these complications appeared to be hyperinflation of the distal balloon (20−40 mL), although external chest compression and continuous PPV may also have been factors. Other rare complications include transient cranial nerve dysfunction,¹²² esophageal rupture,¹²³ and tongue engorgement.¹²⁴

What Are the Potential Clinical Uses of the CBT?

The CBT is an easy-to-use, rapidly inserted emergency airway device that has performed satisfactorily in many circumstances. It is accepted as a primary rescue device in CICO situations, as well as for CPR, and in trauma patients. The CBT has been recommended in the Practice Guidelines for Management of the Difficult Airway of the ASA.^6,7,100 It has also been recommended in the “Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiac Care” of the AHA. In 2000, the CBT was upgraded by the AHA as a class IIa device. Furthermore, the CBT may provide an element of protection in patients at risk for aspiration, and it may be of benefit for patients in whom manipulation of the cervical spine is hazardous or impossible. Successfully placed, the device is capable of facilitating adequate ventilation and oxygenation, and in most instances is as effective as endotracheal intubation.¹⁰⁶

What Is the LT and How Does It Differ from the LMA?

The laryngeal tube airway^® (VBM Medizintechnik, Sulz am Neckar, Germany [Figure 13–9]), also known as the King LT Airway^® in North America, is an EGD that was introduced to the European market in 1999.¹²⁵ It is similar in appearance and function to the CBT, and is available in three configurations (see below). The fundamental configuration of the LT is a silicone airway tube with ventilation outlet perforations lying between two cuffs, pharyngeal and esophageal. As opposed to the CBT, the LT has a single pilot balloon connected to both cuffs, and a single 15-mm standard male adapter. The airway tube is short and “J” shaped with an average diameter of 1.5 cm leading to a blind tip. The device requires a mouth opening of at least 23 mm for its insertion. After device placement, the proximal cuff should lie in the hypopharynx and the distal cuff in the upper esophagus. Both cuffs are high volume low pressure in design to establish an adequate seal, while minimizing the risk for ischemic mucosal damage. Two ventilation outlets are located between the two cuffs, in the anterior aspect of the tube. The proximal outlet is “protected” by a “V”-shaped deflection in the pharyngeal cuff, such that when with the cuff is inflated, soft tissue is deflected from this opening, helping to maintain a patency. There are two side holes near the distal outlet.

Even though the two cuffs are supplied by a single inflation pilot balloon apparatus, the design of the inflation system allows the pharyngeal cuff to fill first, stabilizing the position of the tube.¹²⁵ Once the pharyngeal cuff has molded to the anatomy of the patient, the esophageal cuff inflates. The amount of air for cuff inflation is specific to tube size and is indicated on a syringe that is included in the package. Six sizes, suitable for neonates up to large adults, are available.¹²⁶ Safe inflation of the dual cuffs may be enhanced with the aid of a cuff pressure gauge and ought to be limited to 60 cm H₂O. In a recent report, an overinflation of the LT in a difficult pre-hospital airway management of a patient with Down syndrome resulted in a clinical misdiagnosis of Ludwig’s angina in the Emergency Department, necessitating an emergency tracheotomy.¹²⁷

There are several versions of the laryngeal tube: standard laryngeal tube^®, disposable laryngeal tube^® (LT-D), laryngeal tube-Suction II^® (LTS), and disposable laryngeal tube-Suction II^® (LTS-D).¹²⁶ Similar to the PLMA, the LTS-D has two lumens: one for ventilation and the other serves as a conduit to the esophagus and stomach.

How Is a LT Inserted?

An appropriately sized LT should be selected based on the patient’s weight and height. Prior to insertion, the cuffs should be completely deflated and well lubricated. The device should be inserted with the patient’s head and neck in a “sniffing” position.¹²⁶ The head is extended on the neck with the non-dominant hand, to open the mouth. The LT is then inserted blindly in the midline, with the tip pressed against the hard palate, and then advanced along the palate into the hypopharynx until resistance is felt, at which point a proximal horizontal black line should be aligned with the front teeth. The device is usually easily inserted with insertion times comparable to those reported for the LMA.¹²⁸

The device provides a patent airway in the majority of patients following the first insertion attempt and success does not require extensive training.^129,130 Indicators of correct placement include end-tidal carbon dioxide detection, auscultation of bilateral breath sounds, absence of gastric insufflation, and adequate chest movement. Capnographic waveform analysis may be of particular use in confirming proper position of the LT. A brief period of PPV may also confirm proper alignment of the LT and the absence of obstruction.