on the display makes it easier to observe changes in the exhaled carbon dioxide level. This also enables measurement of ventilation rate.
There are two primary designs for capnometers and waveform capnography: sidestream and mainstream [69]. Sidestream devices draw a sample of the exhaled gases from a port attached to the endotracheal tube. For mainstream capnography the sensor is placed in the gas delivery line near the endotracheal tube. In general, with sidestream devices there is a short (<1 second) delay between gas sampling and display of a carbon dioxide level. In contrast, in‐line devices provide instant carbon dioxide readings. The sensor for an in‐line device is placed near the endotracheal tube. The sensors for newer in‐line devices are light, compact, and less bulky and awkward than their predecessors. Sidestream devices may be more prone to condensation. EMS personnel may use sidestream devices with a nasal cannula in spontaneously breathing patients, broadening their potential application.
Waveform end‐tidal capnography is the most accurate tracheal tube placement verification and monitoring technique. However, waveform capnographers are expensive (over $3,000 per unit). Multiparameter cardiac monitors have options for integrated capnography. In situations with low perfusion (e.g., cardiopulmonary arrest) there may be inadequate circulation of carbon dioxide to the lungs. In these situations, carbon dioxide detectors may incorrectly indicate a misplaced endotracheal tube
Figure 3.13 Waveform carbon dioxide detector.
An essential consideration is that prehospital patients undergo considerable movement during field care, which may heighten the risk for tube dislodgement. Many EMS medical directors have emphasized the need for frequent reverification or continuous monitoring of endotracheal tube placement, especially after each patient movement; for example, after moving the patient onto the stretcher or loading into an ambulance. Only capnometers and waveform capnography are currently capable of providing continuous tube placement information. Whenever it is available, continuous waveform capnography should be standard all intubated patients.
While some clinicians rely on fogging of the endotracheal tube to indicate its correct placement, a well‐executed animal study demonstrated the inaccuracy of this technique [70]. Ultrasonography has been proposed as a method for confirming endotracheal tube placement, but this technique has not been tested in large series in the prehospital setting [71].
Methods for securing endotracheal tubes and supraglottic airways
EMS personnel must adequately secure the endotracheal tube or supraglottic airway to prevent device dislodgement. The most common method for securing the endotracheal tube is the use of adhesive tape wrapped around the neck and the endotracheal tube (Lillehei method) [72]. Another method uses umbilical twill tape, which is a flat, woven cloth tape designed for tying off umbilical cords after childbirth. Some EMS personnel use intravenous or oxygen tubing to tie the endotracheal tube in place. A variety of commercial tube holders also exist, typically consisting of a plastic bite block strapped to the patient’s face using Velcro tape and a plastic strap or screw clamp to hold the endotracheal tube in place. Current ACLS guidelines recommend the use of commercial tube holders. However, one cadaver study found that conventional adhesive taping of the endotracheal tube surpassed most commercial tube holders [72]. The one exception was the Thomas Tube Holder™ (Laerdal Medical, Inc., Stavanger, Norway), which performed better than taping. Only limited prehospital clinical data describe the effectiveness of endotracheal tube securing methods at preventing tube dislodgement [73]. There are also no data describing the effectiveness of spinal or cervical immobilization devices at preventing tube dislodgment.
Some EMS personnel manually hold the endotracheal tube in place without using tape or other tube security methods. We do not recommend this method, as anecdotal reports have associated this technique with inadvertent tube dislodgement. In addition, the force required to dislodge many devices is increased substantially by securing them in place [74]. Because of the theoretical risk of tube dislodgement with flexion‐extension or lateral rotation of the head, some EMS clinicians also apply a cervical collar.
EMS personnel should also secure supraglottic airway devices such as the i‐gel, LT airway, and LMA. The manufacturers recommend conventional taping methods for securing these airways (LT airway and LMA) or the use of a proprietary holder (i‐gel). We have observed that some commercial tube holders are not designed for supraglottic airways (which have wider outer diameters than endotracheal tubes) and do not adequately hold these devices in place.
Drug‐facilitated intubation
Drug‐facilitated intubation is the use of intravenous sedative and/or neuromuscular blocking agents to facilitate ETI of patients with intact protective airway reflexes [75].
Rapid sequence intubation
Rapid sequence intubation (RSI) denotes the use of a neuromuscular blocking (paralytic) agent combined with a sedative or induction agent to facilitate ETI of a patient with intact protective reflexes. The salient goals of RSI are to facilitate rapid sedation and paralysis of the patient and insertion of the endotracheal tube while effecting minimum physiological disturbances (heart rate, blood pressure, intracerebral pressure, etc.). Current prehospital RSI practices closely parallel emergency department practices. The general clinical indications for prehospital RSI include the need for airway and ventilatory control in patients with intact protective airway reflexes: for example, victims of traumatic brain injury.
RSI technique
The main elements of prehospital RSI include:
Insertion of an intravenous line.
Attachment of continuous monitors (electrocardiogram, blood pressure, and pulse oximetry).
Preoxygenation of the patient (nonrebreather mask or BVM ventilation).
Rapid administration of pretreatment, sedative/induction, and neuromuscular blocking agents.
Performance of laryngoscopy and tube placement.
Verification of tube placement and securing of the endotracheal tube.
Pretreatment agents may be administered prior to attempting RSI, for example, intravenous lidocaine to attenuate the intracerebral pressure response to laryngoscopy. Because there are only limited data supporting the effectiveness of pretreatment regimens, protocols often exclude the use of these agents during prehospital RSI.
Sedation
A wide range of sedative/induction and neuromuscular blocking agents exist. The most popular sedative/induction agent for RSI is etomidate. Most clinicians favor this agent because of its minimal effect upon blood pressure, heart rate, and intracerebral pressure. The typical induction dose for etomidate is 0.3 mg/kg intravenously (20 mg in a typical 70‐kg patient). Some studies have raised concern regarding the clinical consequences of adrenal suppression resulting from etomidate administration [76, 77]. Limited data describe the link between etomidate’s adrenocortical suppression and patient outcomes [77].
Another commonly used agent for sedation/induction is midazolam 0.1 mg/kg. However, because midazolam and other benzodiazepines may cause clinically significant hypotension, and because many prehospital patients requiring RSI have significant hemodynamic compromise, many
