The skills of airway management
RJ is a 34-year-old, 6ft, 100 kg, unhelmeted male operator of an ATV who was thrown from the vehicle. The flight crew arrived, completed their survey, placed the patient on the monitor, established a 20G peripheral IV, and hung normal saline. The patient’s GCS was 7, BP 104/50, pulse 128, respiratory rate 24, and oxygen saturation 94% on 15L NRB.
The patient’s airway was assessed using the LEMON method. Look externally – noting a possible fractured jaw. Evaluate using the 3-3-2 rule, noting that three fingers could not be placed in the mouth, three fingers could be placed from the angle of the jaw to the mentum, and two fingers could be placed from the thyroid cartilage to the bottom of the jaw. The Mandible was not receding. Obstruction was assessed using a modified Mallampati, which provided a clear view of the posterior oropharynx and uvula when the blood was suctioned. Lastly, the patient’s Neck mobility was limited by the cervical collar, which was removed and inline stabilization was held while providing a jaw thrust. Etomidate and succinylcholine were drawn up. Drug choices and dosing were verbalized aloud and confirmed using a challenge–response method and visual inspection by both crew members. A checklist was read aloud while the flight crew prepared for intubation. The BVM and O2 were checked, the suction device was functional, the IV patency confirmed, and the patient’s pulse oximetry, pulse, and BP were checked. Oxygen via nasal cannula at 6 LPM was placed on the patient to provide passive oxygenation. An 8.0 and 7.5 ETT were placed next to the patient. The 8.0 balloon was inspected and a stylet was lubricated and inserted. The video laryngoscope (VL) was turned on and was recording. A waveform capnograph was connected as was a commercial tube holder. A #5 King LTD-S was placed on the patient’s chest as a contingency.
The RSI medications were administered and the patient was oxygenated with a BVM. After fasciculation, the VL was placed while suctioning and the ETT was visualized to pass through the cords. The balloon was inflated and placement confirmed by EtCO2 and five-point auscultation. The tube was secured with a commercial tube holder and the patient was reassessed to ensure stable vitals. The patient was sedated and placed in restraints to preclude self-extubation.
Introduction
Airway management is one of the most essential interventions in the prehospital care of the critically ill or injured [1,2]. Many scientific efforts have highlighted the difficulty of endotracheal intubation (ETI) in the prehospital setting, the adverse events associated with the procedure, and the challenges in attaining and maintaining clinical proficiency. Other studies highlight the uncertain connections with improved patient outcomes [3]. These observations underscore that airway management is not simply a discrete procedure but a comprehensive strategy of care that requires close, system-level medical oversight. The most successful prehospital airway management programs incorporate multiple elements including training, skills verification, equipment selection, decision support, continuing education, and total quaility management.
The goal of this chapter is to describe the medical direction paradigms and considerations necessary for a high-quality airway management program. The practicing EMS physician must also be aware of these issues, and must be an expert in out-of-hospital airway management.
The challenges of airway management in the prehospital setting
Airway management in the prehospital setting comes with unique challenges. Prehospital airway management occurs in an uncontrolled environment where patients are severely ill, undifferentiated in presentation and medical history, and may be situated in awkward positions (e.g. on the floor, in a bed, or in the wreckage of a car). Prehospital providers, including EMS physicians, have fewer monitoring and pharmacological options than exist in the hospital. Unlike the hospital setting, there are very limited resources with respect to personnel and equipment. These factors significantly increase the complexity and difficulty of airway management and underscore the need for simple and efficient field approaches.
While the individual components may resemble techniques performed in the hospital, prehospital airway management often requires approaches different from the hospital setting. The medical director must be keenly aware of these distinctions and provide appropriate guidance. When it is the EMS physician who is managing the airway in the field, he or she must be aware of the differing resources and conditions from those in a hospital where the bulk of his or her experience might have been garnered.
Which airway, when, and how?
Successful prehospital airway management relies on the optimized combination of basic, advanced, and rescue airway interventions. Medical directors must choose strategies appropriate for the needs of their services based on available personnel, resources, and environment. An exclusive focus on any one management technique will limit the providers’ abilities to adapt to difficult situations and failed procedures.
Basic airway interventions
Basic airway interventions include measures to provide supplemental oxygen and/or ventilation without the use of an advanced invasive airway device. Basic airway interventions are used by providers of all skill levels. While they lack protection from aspiration (and in fact may increase aspiration risk through inadvertent gastric insufflation), they are the essential foundation of any successful airway management program. Providers of all levels – even practitioners who perform more advanced airway interventions – must master basic airway techniques. Practitioners will rely on basic airway intervention skills when advanced airway interventions fail.
The medical director may define conditions for which basic airway management is the preferred technique. These situations may include scenarios with short transport times where the time and risk necessary to perform advanced airway maneuvers outweigh the benefits of a secure airway. Another example is pediatric respiratory arrest, where most providers are more experienced with bag-valve-mask ventilation than endotracheal intubation.
Endotracheal intubation
Endotracheal intubation is the most widely recognized method of invasive airway management and has been performed by paramedics in the United States for over 25 years [4–7]. ETI has many theoretical advantages, including isolation of the airway from secretions or gastric contents and the provision of a direct conduit to the trachea without separate airway opening maneuvers. However, equipoise exists with respect to the clinical benefit of ETI in the prehospital environment.
Endotracheal intubation is associated with several risks, including failed intubation, unrecognized esophageal intubation, hypoxia, hypotension, bradycardia, aspiration, and airway trauma. Many of the risks of ETI can be mitigated through proper training and equipment. However, prehospital systems are often unable to make the substantial investments necessary to ensure a high degree of safety in the procedure. Medical directors who choose ETI as a method of airway management must be prepared to properly educate and train their providers, ensuring that they have the decision-making and psychomotor skills necessary to perform the procedure. This must include a minimum of didactic training on the indications, contraindications, and techniques for endotracheal intubation, and simulated and live intubations in supervised environments.
The medical director must determine how best to provide suitable training to providers performing ETI. Strategies may include mandatory minimums for yearly ETI experience supplemented by simulation and supervised experience in the operating room (OR) or emergency department (ED). In order to concentrate limited field experiences, it may be necessary to restrict the skill to a few selected providers. A commitment to continuous quality improvement is also necessary, requiring rigorous review of all airway cases. Direct observation in the field or through video review is often desirable. Quantitative assessment of ETI should include not only procedural success rates but also physiological measurements. ETI attempts should be confirmed by end-tidal carbon dioxide (EtCO2) and monitored for vital sign abnormalities including hypoxia, hypotension, and bradycardia. When available, quality assurance should also include time to intubation and review of video images [8].
Several adjunctive techniques are available to facilitate ETI, each with distinct advantages and disadvantages. For example, the tracheal introducer or gum elastic bougie has been widely described as a device either for blind intubation or as an adjunct for difficult intubation. While use of such devices may improve intubation success, the medical director must consider their added complexity as well as the need for additional training and skills maintenance. The latter point deserves emphasis. Each newly acquired tool intended to improve the likelihood of successful or optimal airway management also increases the burden or obligation to maintain skills regarding its use. This reality is too easily overlooked in the enthusiasm to deploy something new which is perceived to make circumstances easier.
Does prehospital ETI improve survival?
Few studies link prehospital ETI to improved patient survival. Gausche et al. performed the only randomized, controlled trial of prehospital ETI, finding no differences in survival or neurological outcome between children receiving ETI and those receiving bag-valve-mask (BVM) ventilation [9]. Davis et al. evaluated patient survival after paramedic rapid sequence intubation (RSI) for traumatic brain injury, associating prehospital RSI with an increased risk of death compared with matched historical controls [10]. A variety of other studies encompassing a range of different patient subsets observed equivocal or worsened outcomes associated with prehospital ETI [3,11]. While most cases of prehospital ETI occur for patients in cardiac arrest, there have been only observational analyses of this subset. This is primarily due to the large sample sizes (>10,000 patients) that would be required to detect survival differences or equivalence in this population. Thus, while ETI is common prehospital practice, its survival benefit remains unproven.
Do adverse events occur during prehospital ETI?
Recent studies have drawn attention to previously unrecognized adverse events associated with prehospital ETI. Successful prehospital airway management programs have placed strong emphasis on minimizing these and other adverse events. Many of these adverse events have been detected only through the advent of monitoring technology and rigorous airway management review.
Katz and Falk described 108 paramedic-placed endotracheal tubes brought to an Orlando trauma center, finding that the tube was misplaced in 25% of the cases [12]. Other studies have identified lower but not insignificant incidences of endotracheal tube misplacement [13,14]. Other efforts describe the frequency of endotracheal tube dislodgment during prehospital care [15]. Use of continuous EtCO2 has reduced the incidence of the unrecognized misplaced endotracheal tube.
Dunford et al. examined a subset of patients receiving prehospital RSI and found that a considerable portion experienced iatrogenic oxygen desaturation or bradycardia during intubation attempts [16]. Hypoxia and bradycardia may be prevented by continuous monitoring of pulse oximetry with the provision of oxygen and supplemental ventilation during any period of hypoxia. Episodes of hypoxia can be mitigated using apneic oxygenation through a high-flow nasal cannula applied during the endotracheal intubation attempt.
Prehospital ETI can also interact or interfere with other important resuscitation tasks. For example, Davis et al. linked post-RSI hyperventilation with worsened TBI outcomes [17]. Aufderhiede et al. showed that hyperventilation after successful ETI of cardiac arrest patients can compromise coronary perfusion during cardiopulmonary resuscitation (CPR) chest compressions [18,19]. Studies on human simulators suggest that conventional ETI efforts may increase CPR “hands-off” or no-flow time (pauses in CPR to facilitate endotracheal intubation) compared with other airway devices [20]. Models of high-performance CPR now teach providers to defer airway management in favor of providing uninterrupted compressions.
Should emergency medical technicians perform ETI?
The prior national EMT curriculum included ETI as an optional module [21]. However, the ability of EMTs to acquire and maintain clinical ETI skills remains unclear. Two independent studies of EMT ETI found suboptimal success rates (<50%) [22,23]. Most medical directors are not comfortable with EMTs performing ETI. However, several series describe the ability of basic EMTs to use supraglottic airways (SGA) (e.g. Combitube) [24–26]. The current National EMS Education Standards do not list either ETI or SGA as EMT skills; SGAs are listed for advanced EMTs.
Should EMS providers limit the number of ETI attempts?
While many prehospital EMS personnel define an ETI “attempt” as an effort to insert the endotracheal tube, national consensus guidelines suggest that an ETI “attempt” should be defined as an insertion of the laryngoscope blade, to maintain consistency with other airway management definitions used in other medical disciplines. Selected studies indicate that a substantial portion of prehospital ETI require multiple attempts [27]. Evaluations of inhospital ETI efforts suggest that more than one ETI attempt is associated with an increased risk of developing cardiac arrest [28]. Some EMS agencies use a “three attempts and out” rule, limiting intubation efforts to no more than three attempts. Given the low probability of success following the second attempt, medical directors may choose to limit providers to two attempts, followed by immediate use of a supraglottic rescue airway.
Drug-facilitated intubation
Drug-facilitated intubation (DFI) is the use of intravenous sedative and/or neuromuscular blocking agents to facilitate ETI of patients with intact protective airway reflexes [29]. The most common forms of DFI include RSI, also termed “neuromuscular blockade-assisted intubation,” and sedation-assisted intubation. Most medical directors regard DFI as an advanced technique that should be reserved for only the most qualified practitioners. The National Association of EMS Physicians has published national consensus standards for drug-facilitated intubation [29].
Rapid sequence intubation denotes the use of a neuromuscular blocking (paralytic) agent combined with a sedative or induction agent to facilitate ETI. The key challenge of RSI is that administered paralytic agents will result in rapid and complete loss of airway reflexes. EMS personnel (including EMS physicians) performing prehospital RSI must possess exceptional ETI skills. The consequence of failed RSI may be a patient who cannot be intubated nor ventilated, with ensuing cardiac arrest from hypoxia.
Agencies performing RSI must use monitors capable of continuous physiological monitoring, including cardiac rhythm, heart rate, blood pressure, pulse oximetry, and waveform capnography. These measures are important to warn of physiological decompensation such as oxygen desaturation and bradycardia. Finally, there must be a plan and appropriate preparation for those times when RSI fails, including a rescue airway.
Many medical directors believe that intensive continuing training is essential for maintaining a prehospital RSI program. Some medical directors require that paramedics perform at least 12 ETIs annually, either on prehospital or in-hospital (ED or OR) patients [30]. Others have integrated human simulator-based training to provide exposure to difficult airway scenarios [31]. The requirement for live ETI training remains controversial, with some proponents citing the value of live airway experience and opponents citing the absence of supporting data [29].
Experts recommend restricting RSI to EMS agencies with the highest standards of clinical airway management practice, including a comprehensive commitment to airway management quality. Colloquially speaking, “RSI is not just about the drugs.” As with ETI, medical directors and providers considering RSI must place an emphasis on clinical decision making, not just procedural technique [29].
A modification of RSI is rapid sequence airway (RSA), which replaces ETI with placement of a SGA [32]. RSI is difficult because of the need to rapidly accomplish tracheal intubation after the administration of paralytics. The appeal of RSA is that SGA insertion is simpler and contains fewer pitfalls than ETI. This approach is theoretically safer than traditional RSI. RSA case reports using the Combitube and King LT have demonstrated the feasibility of this approach. In a simulation study, when compared to RSI, Southard demonstrated that RSA reduced time to airway placement and reduced hypoxia episodes [33]. When examined in an air medical system, however, no difference was detected between the two techniques [34]. While other anecdotal reports exist, RSA has not been described in larger scientific series. However, in systems using traditional RSI, RSA may provide an important alternative option in the face of an anticipated or encountered airway management difficulty.
Sedation-assisted intubation is a common approach that uses a sedative agent only, without concurrent neuromuscular blocking agents Most medical directors discourage this technique. The anesthesia community has promoted sedation-assisted intubation as being safer than RSI, citing that patients receiving only sedatives may retain adequate native reflexes to preserve airway patency in the event of unsuccessful ETI efforts. However, it is not clear if this principle can be generalized to the prehospital setting. Prehospital EMS personnel often do not possess the laryngoscopy skills of anesthesiologists, and the environments are at opposite ends of the spectrum in terms of optimal control.
Adverse events associated with RSI (e.g. iatrogenic oxygen desaturation and bradycardia) may be at least as likely with sedation-assisted ETI [16,17]. Sedation-assisted intubation with etomidate has been demonstrated to have lower success rates when compared to RSI [40]. While etomidate results in more profound sedation than benzodiazepines, a formal comparison of etomidate with midazolam for prehospital sedation-assisted intubation identified similar ETI success rates [37].
Many EMS systems use other combinations of slow-onset benzodiazepines and opiates to facilitate endotracheal intubation, such as combinations of diazepam, morphine, or other agents. This practice is particularly unsafe since the single or combination use of these agents has a rather slow onset and unpredictable sedative effects, as well as strong potential for causing hypotension. From a medical oversight point of view, the system-level measures necessary to ensure airway management quality with sedation-assisted intubation are essentially equal to those required for RSI programs.
Video laryngoscopy
Video laryngoscopy is increasingly being adopted for use in training and difficult airway scenarios in both the OR and ED [41–44]. Prehospital application of this tool has resulted in improved laryngscopic view, increased intubation success, and decreased time to tracheal intubation [45,46]. However, these devices, while useful, are not a replacement for basic intubation training and skills. In addition, practitioners must be familiar with the skills particular to the device. Complications associated with video laryngoscopy are similar to those for traditional intubation, including multiple intubation attempts and airway perforation [47].
