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.
Figure 3.10 Cricothyroidotomy.
Confirmation of airway placement
After ETI, verification of endotracheal tube placement is essential [64]. Tube placement verification is particularly important given the uncontrolled nature of the prehospital environment and the risks of unrecognized tube dislodgement or misplacement [65–68]. Because of the amount of patient movement during prehospital care, EMS personnel must frequently, and preferably continuously, verify correct tube positioning. In addition to visualizing the endotracheal tube passing through the vocal cords into the trachea, endotracheal tube placement should be confirmed using multiple techniques.
Auscultation is the most common method for verifying endotracheal tube placement. The rescuer auscultates both lung fields to verify the presence of breath sounds, and auscultates the epigastrium to verify the absence of gastric sounds. It is possible to be misled by transmitted sounds, however.
Some low‐tech innovations have been helpful in the past. The esophageal intubation detector consists of a Toomey syringe with a special adaptor for the endotracheal tube. The esophageal detector device is a large, bulb‐type device (Figure 3.11). Both of these devices are based on the concept that the esophagus will collapse, producing resistance to a vacuum, while the trachea will not collapse and will therefore not produce any resistance as the bulb or plunger produces suction.
Figure 3.11 Esophageal detector device.
The most important technique for verifying endotracheal tube placement is detection of exhaled, or end‐tidal, carbon dioxide. There are currently three types of devices used for detecting end‐tidal carbon dioxide: 1) colorimetric end‐tidal carbon dioxide detector, 2) digital capnometer, and 3) waveform end‐tidal capnography.
Figure 3.12 Colorimetric carbon dioxide detector.
The colorimetric end‐tidal carbon dioxide detector uses a chemically treated paper detector that changes color from purple to yellow when exposed to carbon dioxide (Figure 3.12). If the paper color remains purple, this suggests esophageal tube placement. Designed for single use, these devices can be used for only a limited duration (<2 hours). Exposure to liquid (for example, vomitus or blood) may render these devices nonfunctional.
Digital end‐tidal carbon dioxide capnometry samples exhaled gases, measuring and displaying the carbon dioxide level. A positive carbon dioxide level connotes correct endotracheal tube placement.
Waveform end‐tidal capnography is similar to digital capnometry, except that the exhaled carbon dioxide level is depicted continuously in graphical form (Figure
