Extraglottic Devices
Darren Braude
Erik G. Laurin
Leslie V. Simon
INTRODUCTION AND TERMINOLOGY
Extraglottic devices (EGDs) are inserted into the upper esophagus or hypopharynx, but not through the glottis, to provide a conduit for gas exchange—particularly in patients who are difficult or impossible to ventilate with a facemask. Those that sit above the larynx are termed supraglottic devices (SGDs) while those that sit posterior to the glottis in the upper esophagus are termed retroglottic devices (RGDs).
Historically, EGDs were used for elective procedures in fasted patients, but over time have evolved into a role in managing airway emergencies. These devices are usually placed blindly and may be used as primary (alternative) or secondary (rescue) airways. EGDs are generally easier to utilize than facemask ventilation or endotracheal intubation, and have also been shown to provide some degree of aspiration protection.1,2,3,4,5,6,7 In a cadaver model, seal pressures of seven different EGDs were variable but very substantial.8 In a small study of emergency medical services (EMS) patients specifically looking at aspiration rates, EGDs and endotracheal intubation were similar.5 Similarly, prehospital EGD use did not impact the rates of ventilator-associated pneumonia in hospitalized trauma patients.6 Two large studies showed that aspiration rates with the King Laryngeal Tube (King LT™) and i-gel® were similar to intubation in patients with cardiac arrest.1,7 In both prehospital and ED case series looking at use of induction followed by an SGD, aspiration rates were quite low.2,9
SGDs all have a single cuff that seals around and above the glottis. This cuff may be inflatable with air, self-pressurizing with air, or made of gel. The prototypical SGD is the Laryngeal Mask Airway but there are now multiple other SGDs available. Second-generation devices are those with a channel to facilitate gastric decompression, though there is great variability in what size gastric tube is accommodated. The LMA Fastrach™ is designed to facilitate blind intubation with high success rates.10 None of the other SGDs have shown such high success with blind intubation, but all devices except the LMA Supreme™ will facilitate endoscopic exchange. Like the King LT, SGDs have proven useful in the difficult and failed airway and are part of all major society guidelines.11,12,13,14
RGDs may have one (e.g., King Laryngeal Tube) or dual (e.g., Combitube™, EasyTube™) lumens but all have two balloons-one proximal to occlude the pharynx and one distal to occlude the espohagus—with fenestrations for gas exchange between the balloons. Dual lumens provide an option for ventilation in case of blind insertion into the trachea, but they add complexity for a very rare event and are becoming more uncommonly used. Inflated RGD balloons may lead to mucosal ischemic injury, especially when left in place for prolonged periods (>4 hours) or when the balloons are overinflated.15,16 The King LT has been shown to be useful in the difficult and failed airway.17 Intubation through the King LT is challenging and requires intermediate steps, though intubation around it is usually successful.18 There is a newer version of the Laryngeal Tube available in Europe, the iLTS-D that is intended to facilitate intubation.
Cuff leak pressure, which is the pressure within the airway up to which the device prevents air leakage, varies depending on the device and fit. RGDs typically have higher cuff leak pressures (up to 35 to 40 cm H2O) compared with SGDs (25 to 30 cm H2O). This tighter seal may be advantageous in patients with intrinsic high airway resistance requiring high peak airway pressures (e.g., asthma or obesity) or if glottic anatomy is distorted from hematoma, infection, or mass, requiring increased inflation pressure. These devices may also provide some tamponade effect for upper airway bleeding. There has been some concern from animal studies that RGDs exert more pressure on the carotid vessels than SGDs, but this has not been supported in human studies.19,20
For the purposes of airway management in the critically ill, the ideal EGD would be inexpensive, easy to use, available in adult and pediatric sizes, have a high first attempt success for oxygenation and
ventilation in a wide variety of clinical circumstances, allow gastric drainage, and serve as a conduit to the trachea for intubation. There are a number of products that meet these requirements, however, there is little research demonstrating clear superiority of one device over another. The choice of which EGD may come down to preference for specific features or convergence with other parts of the hospital or prehospital community. It is valuable to have consistency and familiarity across settings since critical care clinicians are as likely to manage an EGD placed by another provider as to place one themselves. Most devices used outside the OR settings are single use and inexpensive.
ventilation in a wide variety of clinical circumstances, allow gastric drainage, and serve as a conduit to the trachea for intubation. There are a number of products that meet these requirements, however, there is little research demonstrating clear superiority of one device over another. The choice of which EGD may come down to preference for specific features or convergence with other parts of the hospital or prehospital community. It is valuable to have consistency and familiarity across settings since critical care clinicians are as likely to manage an EGD placed by another provider as to place one themselves. Most devices used outside the OR settings are single use and inexpensive.
Critical care clinicians may place EGDs themselves or may be called to assist with managing patients with a device already in place. Therefore, it is necessary to be familiar with a wide range of devices and comfortable with their insertion, assessment, troubleshooting, management, and exchange.
INDICATIONS FOR AN EGD
The indications for these devices have expanded over the past several decades and now include potential for the following:
Primary Airway
Whenever facemask ventilation is indicated but challenging (presuming gag reflex absent).
Cardiac arrest airway management in pediatric and adult patients. EGDs are easily inserted and minimize interruptions during CPR with less training required, making them an attractive management strategy during cardiac arrest. EGDs have shown similar to improved outcomes when compared to endotracheal intubation in two large prospective randomized prehospital trials.1,7 As a result of these trials, many EMS systems and some hospitals have adopted an EGD-based initial airway strategy for cardiac arrest.
For Rapid Sequence Airway (RSA) which is an approach to medication-facilitated airway management utilizing the preparation and pharmacology of RSI, including an induction agent and paralytic, with the planned first-line use of an extraglottic airway.21 RSA has been evaluated in both prehospital and ED case series.2,9,21
As a conduit to facilitate tracheal intubation. This is especially true when intubation is predicted to be difficult but EGD placement will maintain oxygenation and ventilation. In these cases, quickly placing an EGD can minimize apnea time and possibly avert disaster. Depending on the clinical scenario this may require medication facilitation. Endoscopic intubation can then proceed through the EGD via a swivel adapter while continuing ventilation and oxygenation.
Secondary Airway
When mask ventilation proves difficult after an unsuccessful intubation attempt, especially if the operator wants to use the EGD to facilitate recruitment, gastric decompression, and/or intubation.
In a “can’t intubate, can’t oxygenate” failed airway situation, while simultaneously preparing for cricothyrotomy. There is evidence for this strategy dating back to the 1990s.
CONTRAINDICATIONS FOR USE
There are no absolute contraindications for EGD use during airway emergencies. Reluctance to attempt EGD placement when relative contraindications are present is a common pitfall.
Relative contraindications for EGD use include:
Requirement for high airway pressures (obstructive lung disease, obesity, etc.)
High risk for aspiration (blood or emesis in the mouth)
Distal airway swelling, obstruction, or distortion
Intact gag reflex
Specific relative contraindications for RGDs include:
Potential esophageal disease such as strictures, varices, or caustic ingestions due to the risk of mucosal perforation
INSERTING A SUPRAGLOTTIC DEVICE
Of the many SGDs currently available, the only ones that are both designed as a conduit for intubation and have a gastric tube channel are the Intersurgical i-gel, Cookgas airQ Blocker and airQ3, Ambu Aura-Gain, and LMA Protector. The technique for insertion and establishing successful ventilations is similar for each of these devices.
General Technique for SGD Use (
Video 22.1)
Video 22.1)Video 22.1. Supraglottic Airway Device Insertion
Select the appropriate size device. SGD sizing is generally based on ideal body weight, though some manufacturers recommend actual body weight. SGDs intended for emergency use come with clear weight ranges listed on the packaging and the device itself.
Prepare the device for insertion
Cuff: for devices with an inflatable cuff, traditional manufacturer recommendations have called for complete deflation prior to insertion (Fig. 22.1). Recent experience with the newer devices suggests that insertion without adding or subtracting the air that comes in the device is often more effective and helps prevent the tip from flipping back. Air can then be added if necessary, though they tend to seal better with less rather than more air volume. The i-gel and air-Q sp (self-pressurizing) models do not require inflation or deflation.
Figure 22.1: Correct method of deflating the LMA Cuff.
(From Laurin EG, Simon LV, Braude DA. Extraglottic devices. In: Brown CA III. The Walls Manual of Emergency Airway Management. 6th ed. 2023:124-140. Figure 13.8.)
Lubrication: if the mouth is dry, a water-based lubricant applied to the posterior surface of the cuff and ventilation tube will facilitate rapid atraumatic insertion. Keep lubricant out of the bowl of the cuff.
Prepare the patient for insertion
Muscle relaxation: if the patient is not already obtunded due to clinical condition or previous administration of induction and paralytic agents from failed intubation attempts, consider the use of RSI medications to facilitate muscle relaxation and attenuation of the gag reflex.
Positioning: when not contraindicated by concerns for cervical spine injury, placement in the sniffing position or head extension is ideal. A jaw thrust is usually helpful as well.
Insert the device. Open the mouth as wide as possible and direct the SGD along the hard palate and advance over the back of the tongue, allowing the natural curvature of the SGD to follow the curvature of the pharynx and hypopharynx until it seats in position (Figs. 22.2, 22.3, 22.4, 22.5 to 22.6). The older, more flexible SGDs often require placement of a finger into the mouth at the cuff-tube junction (Fig. 22.2), though this is typically no longer necessary with the new SGDs with stiffer ventilation tubes.
Figure 22.2: Correct position of the fingers for LMA Insertion.
(From Laurin EG, Simon LV, Braude DA. Extraglottic devices. In: Brown CA III. The Walls Manual of Emergency Airway Management. 6th ed. 2023:124-140. Figure 13.9.)
Figure 22.3: Starting insertion position for the LMA Classic and LMA Unique.
(From Laurin EG, Simon LV, Braude DA. Extraglottic devices. In: Brown CA III. The Walls Manual of Emergency Airway Management. 6th ed. 2023:124-140. Figure 13.10.)
Figure 22.4: Insert the LMA to the limit of your finger length.
(From Laurin EG, Simon LV, Braude DA. Extraglottic devices. In: Brown CA III. The Walls Manual of Emergency Airway Management. 6th ed. 2023:124-140. Figure 13.11.)
Figure 22.5: Complete the insertion by pushing the LMA in the remainder of the way with your other hand.
(From Laurin EG, Simon LV, Braude DA. Extraglottic devices. In: Brown CA III. The Walls Manual of Emergency Airway Management. 6th ed. 2023:124-140. Figure 13.12.)
Figure 22.6: Inflate the collar of the LMA.
(From Laurin EG, Simon LV, Braude DA. Extraglottic devices. In: Brown CA III. The Walls Manual of Emergency Airway Management. 6th ed. 2023:124-140. Figure 13.13.)
Postplacement management
Visually assess that the SGD was sized correctly and seated appropriately. Adjust or reinsert alternative size as indicated.
Assess ventilation using waveform capnography, looking at chest rise, and listening/feeling for air leaks at the mouth.
If ventilation is completely obstructed, the primary concern is that the tip of the cuff has flipped over or the epiglottis was flexed down toward the feet. Withdraw the SGD several centimeters with the cuff inflated, reinsert to the correct depth, and re-evaluate.
If there is an air leak present and an inflatable cuff, add small volumes of air keeping track of the maximum cuff volumes which are usually indicated clearly on the SGD sidewall. Keep in mind that overinflation can also result in an air leak.
Confirm proper function, secure the device, and continue ventilation.
Complications and Limitations
The incidence of difficult ventilation or major airway adverse events with SGDs is quite low and is thought to be significantly less than standard tracheal intubation or bag-mask ventilation.22 The SGD may fail to provide a seal sufficient to permit adequate ventilation and prevent gastric insufflation. This may be an inherent limitation of SGDs or due to incorrect sizing, inappropriate cuff volume, or attributed to the sensitivity of the seal to head and neck position.23 Although SGDs may not offer total protection from the aspiration of regurgitated gastric contents, they do provide a remarkable amount of protection as discussed in the previous section.
INSERTING A RETROGLOTTIC DEVICE
In common practice, RGDs are inserted blindly, but the recommendation for the Combitube is to use direct visualization for placement when the equipment and expertise exist.22 This likely translates to the Laryngeal Tube as well and may mitigate some of the common issues encountered with RGDs during insertion, particularly trauma to the posterior pharynx.
Insertion Technique—Assuming No Visualization (
Video 22.2)
Video 22.2)Video 22.2. Retroglottic Airway Device Insertion
Choose the correct size device based on patient weight (pediatrics) or height (adults).
Assemble supplies.
Test cuff and then deflate.
Apply lubricant if mucous membranes are dry.
Place patient in neutral or sniffing position.
Perform a jaw lift with the nondominant hand.
Place the LT into the mouth at an approximately 45-degree angle to midline.
Advance the tube into the pharynx while rotating to midline.
Gently and smoothly advance until the color-coded bag connector flange is aligned with the incisors unless resistance is encountered.
The balloons should be inflated through the single port with the recommended amount of air for that size device. A size 4 King-LT (the most used size) requires 60 mL of air.
Ventilation is then attempted while the device is slowly withdrawn, monitoring carefully until unrestricted ventilation and chest rise are noted along with capnography and equal lung sounds. It is common for clinicians to stop withdrawal when the very first sign of ventilation is noted, which may leave the distal ventilation outlets too deep such that they may be delivering air to the stomach and not the lungs. We suggest withdrawing about 1 cm or 2 cm (less for smaller pediatric sizes and more for large adult sizes) past the point when ventilation first occurs and halting when ventilation becomes most prominent and easy to accomplish. This ensures all ventilation is directed to the lungs.Related posts:
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