and seals around the perilaryngeal structure. There is no balloon to inflate. To insert the i‐gel, first lubricate the cuff and then advance the device along the posterior pharynx until resistance is encountered. At this time, the lip line on the i‐gel should align with the lips. It is then secured using a proprietary strap. A study of over 9,000 out‐of‐hospital cardiac arrest patients showed similar outcomes between individuals treated with i‐gel compared to intubation, suggesting a role as primary airway device in this setting [48]. Sizes are available for patients from 2 to >90 kg.
Figure 3.7 i‐gel.
Laryngeal tube
The LT is a SGA that consists of a single lumen tube (Figure 3.8). A single insufflation port simultaneously inflates two balloon cuffs. The LT design is supposed to facilitate more consistent placement in the esophagus than its predecessor, the esophageal‐tracheal Combitube®. Insertion of the LT airway is very similar to that of the Combitube. The rescuer inserts the LT blindly into the patient’s mouth, positioning the smaller distal balloon in the esophagus and the larger proximal balloon in the oropharynx. After balloon cuff inflation, the rescuer may need to withdraw the tube slightly to seal the balloon against the oropharyngeal structures.
Disposable versions of the device exist for prehospital application. There is also a version with an esophageal port permitting concurrent placement of an orogastric tube. Complications, while infrequent, can include laryngospasm, vasovagal asystole, and glottic hematoma [49]. In addition to three different adult sizes, pediatric sizes of the LT are also available. Given the simplicity of its design, the LT can be rapidly placed by EMS clinicians with a range of skills in a variety of clinical settings. In a randomized controlled trial of 3,000 adult out‐of‐hospital cardiac arrests, a strategy of initial LT use was associated with improved adult out‐of‐hospital cardiac arrest outcomes compared with a strategy of initial ETI [46, 49].
Figure 3.8 LT airway.
Laryngeal Mask Airway (LMA)
The LMA is an SGA originally designed for use in the operating room (Figure 3.9) [50]. The distal tip of the airway contains a spade‐shaped balloon designed to seal around the vocal cord structures. The rescuer inserts the device blindly through the oropharynx, positioning the cuff around the laryngeal structures. Inflation of the cuff facilitates proper sealing of the device.
Limited studies describe LMA use by EMS personnel [51]. Prehospital use in the United States remains relatively limited, possibly due to concerns of the device’s inability to prevent aspiration and its potential for inadvertent dislodgement. A variation is the LMA Fastrach, or Intubating LMA, which is designed to facilitate insertion of an endotracheal tube. Disposable versions of both the LMA and the LMA Fastrach currently exist. Pediatric sizes are available.
Other supraglottic airways
The Combitube is a double‐lumen tube with a distal and a proximal balloon similar in design to the LT [52]. If the distal part is correctly positioned in the esophagus (the most common position), insufflation through the longer, blue‐colored lumen will deliver oxygen indirectly to the trachea through holes in the blue‐colored tube at the level of the vocal cords. If the distal part is positioned in the trachea, insufflation through the shorter, white‐colored tube will deliver oxygen directly to the trachea. Although once common, Combitubes are infrequently used in contemporary EMS practice due to associated complications, including oropharyngeal bleeding, esophageal perforation, and aspiration pneumonitis [53].
Other airway devices no longer used in contemporary prehospital EMS practice include the esophageal obturator airway, esophageal gastric tube airway, and pharyngotracheal lumen airway. Other SGAs currently available include the cuffed oropharyngeal airway and the Cobra perilaryngeal airway (Engineered Medical Systems, Indianapolis, Indiana), among others.
Figure 3.9 Laryngeal Mask Airway.
Surgical airways
Surgical airways involve the placement of an airway directly into the trachea through an incision in the neck. The primary prehospital surgical airway techniques include cricothyroidotomy and transtracheal jet ventilation (TTJV). EMS personnel typically use surgical airways in the event of failed endotracheal intubation efforts or when significant facial trauma precludes conventional intubation techniques.
Cricothyroidotomy
Cricothyroidotomy involves exposure and incision of the cricothyroid membrane (directly inferior to the thyroid cartilage) and direct insertion of a tracheostomy or endotracheal tube into the trachea (Figure 3.10). In the classic “open technique,” the operator identifies the thyroid and cricoid cartilages, uses a scalpel to place a longitudinal midline incision over the spaces between them, transversely incises the cricothyroid membrane, and places a tracheostomy tube or 6.0 endotracheal tube through the opening and into the trachea. Some clinicians prefer a transverse incision through the skin, although this approach may heighten the risk of inadvertent thyroid vessel laceration.
An alternate approach uses commercially packaged Seldinger‐type devices. For example, the Pertrach™ kit consists of a needle, wire, dilator, and cannula. The rescuer makes a small skin incision and inserts a needle/dilator combination through the cricothyroid membrane, subsequently using the dilator to spread the tissues. The rescuer can then feed the tracheal tube over the guidewire and into the trachea.
Limited data describe the complications associated with prehospital cricothyroidotomy [54–57]. EMS medical directors question the role of cricothyroidotomy in the field, citing the difficulty of the procedure and its infrequency, with associated need to maintain appropriate competencies [58].
Transtracheal jet ventilation
TTJV, occasionally referred to as “needle cricothyroidotomy,” involves the insufflation of high‐pressure oxygen via a large‐bore intravenous type catheter (16 gauge or larger) inserted through the cricothyroid membrane. This technique requires 50 psi oxygen equipment capable of delivering oxygen at >50 L/min through a catheter. This is equivalent to “wall” oxygen pressure. TTJV cannot successfully be performed using conventional BVM equipment or a standard 25 L/min flow meter.
While TTJV has many theoretical limitations, the clinical implications remain unclear. For example, because TTJV primarily facilitates oxygenation, most clinicians assume that the technique can be used only for a short time. However, extensive data underscore the utility of the technique for prolonged periods [59, 60]. A 16‐gauge catheter with a flow rate >50 L/min and a ventilatory rate of 20 breaths/min can deliver a tidal volume of 950 mL [61, 62]. Aspiration is also a concern, but only limited data clinically quantify this problem [63]. EMS personnel may also use a properly placed jet ventilation catheter to help convert to an open cricothyroidotomy.