Prehospital Airway Management

Key Points

Noninvasive ventilation (NIV) is widely used in the prehospital setting and may be considered in patients with altered mental status when closely attended.
Supine patients undergoing medication-facilitated airway management (MFAM) should be moved off the ground (e.g., to the stretcher) before intubation whenever possible.
Patients being intubated on the ground should have their positioning optimized, and video-assisted laryngoscopy (VAL) used whenever possible.
Strong consideration should be given to supraglottic airways (SGAs) for invasive airway management of entrapped patients.
Sedation-only intubation is not recommended.
For prehospital patients in cardiac arrest, either an SGA or tracheal intubation performed without stopping chest compressions is a reasonable option.

Overview of the Prehospital Care Environment and Structure

Different Types of Emergency Medical Service Systems and Providers

It is impossible to consider airway management in the out-of-hospital environment without understanding emergency medical service (EMS) systems and providers. EMS systems are generally designed to stabilize emergency conditions and facilitate rapid transport to an appropriate receiving hospital or to transport patients between hospitals. Although there are international and regional differences, prehospital care in the United States is commonly provided by professionals at the emergency medical responder (EMR) through paramedic levels. These caregivers may be cross-trained as firefighters or devoted entirely to medical care.

Interfacility transport of critically ill and injured patients is often performed by specialty teams, whether traveling by ground ambulance, airplane, or helicopter. In the United States, these teams are most commonly composed of paramedics and nurses, although respiratory therapists, advanced practice providers, and physicians may also be team members. In other countries, it is much more the norm for physicians to be integrally involved in critical care transport.

The amount of training required to achieve certification at each level of EMS licensure is highly variable from region to region and country to country. In the United States, it commonly takes 50 to 100 hours for an EMR, 150 to 200 hours for an emergency medical technician (EMT), 150 to 250 hours for an advanced EMT (AEMT), and 1000 to 1500 hours, possibly with an associate’s or bachelor’s degree, for a paramedic. The specific amount of time spent on airway training and the scope of practice of the certified or licensed practitioner are also highly variable. Typically, an EMR and EMT are limited to basic measures to remove a foreign body, providing supplemental oxygen, and performing bag-mask ventilation (BMV). Advanced EMTs can place supraglottic airway devices (SGAs), whereas paramedics can deliver noninvasive ventilation (NIV) and perform endotracheal intubation (ETI).

Many paramedics are also credentialed to perform percutaneous or surgical cricothyrotomies, and some may be able to perform medication-facilitated airway management (MFAM). EMS physicians are likely able to perform the broadest scope of prehospital airway management. The wide variability in scope of practice is noteworthy because some jurisdictions may allow EMTs to provide continuous positive airway pressure (CPAP) and place SGAs, whereas in others, paramedics neither intubate nor perform cricothyrotomies.

Unique Considerations

The prehospital setting presents unique challenges to all patient care, not the least of which is airway management. The patient’s disease process is often undifferentiated, resources and equipment may be more limited than in the hospital setting, and there may be issues of patient access, lighting, adverse weather, confined space, turbulence or road vibration, and safety of the provider. When these factors are taken in aggregate, it is unreasonable to expect that out-of-hospital airway management will look identical to in-hospital airway management. Physicians who are not specifically trained in out-of-hospital care or do not have substantial experience in this setting may be particularly challenged when trying to translate their hospital practice to this unique environment.

EMS is an American Board of Emergency Medicine (ABEM)-approved subspecialty, with board certification available to physicians after a minimum 1 year of fellowship that includes a substantial clinical prehospital care component. The subspecialty is open to physicians from any primary specialty although most EMS fellowships are restricted to graduates of emergency medicine residencies. EMS physicians in the United States primarily serve in administrative roles as medical directors although direct patient care by EMS physicians is seen in a few systems, bringing an advanced level of airway management practice and oversight. Internationally, direct patient care by physicians is much more common.

EMS Airway Education and Training

Initial Intubation Training

The best methods for teaching airway procedures have not been definitely established, but it is clear that a sufficient number of procedures are required to attain proficiency. Studies have shown that it takes about 15 intubations in the operating room (OR) to achieve a 90% chance of success on the next attempt, although it is likely that this is skewed because the supervising anesthesiologists and anesthetists probably selected easier cases for the students. Interestingly, even 30 intubations do not predict 90% success in the challenging prehospital environment.

There is extensive debate regarding whether or not live intubations are essential for initial airway training. For a variety of issues, including learner saturation, fewer intubation procedures in the surgical environment, and concerns about liability, fewer supervised live intubations in the OR are available. As a result, many EMS students are trained largely on manikins and simulators. The US Committee on Accreditation of Educational Programs for the Emergency Medical Services Professions (CoAEMSP) recommends a combination of a minimum of 50 “airway encounters” across all age ranges with 100% success in their last 20 attempts at airway management. CoAEMSP states that airway management “may be accomplished using any combination of live patients, high definition fidelity simulations, low fidelity simulations, or cadaver labs.” Although discouraged, it is possible for a paramedic student to complete initial training without a single live intubation. On the other hand, the province of Alberta, Canada, requires 30 intubations of which 20 have to be supervised in the OR. Overall, we believe there is great value in spending time in the OR with an experienced anesthesia practitioner, but not just for intubations. There is equal or greater value, in our opinion, to supervised BMV and SGA placement, as well as the academic discussions that often ensue.

Skill Retention

Initial training is only half the battle. Once working, opportunities for intubation skill maintenance are often limited because of the increased use of NIV and SGAs, as well as the increased number of providers deployed to EMS. Patient survival has been correlated to the number of intubations that the treating paramedic had performed in the previous 5 years. As a result, many agencies set requirements for a minimum number of encounters and success, often relying on low-fidelity simulation. The Committee on Accreditation of Medical Transport Systems (CAMTS) requires three adult, pediatric, and infant intubations per quarter, or a total of 36 intubations per year, all of which may be simulated. Despite this mandate, a number of studies have shown relatively poor first-pass success by nonphysician EMS providers in both the air medical and ground environments utilizing rapid sequence intubatin (RSI), as well as ground-based environments primarily intubating patients in cardiac arrest. This suggests that the CAMTS standards may be insufficient to maintain competence in these challenging settings. It is incumbent on each provider, agency, and system to set its own standards to ensure patient safety and optimize success. Anesthesia providers are strongly encouraged to help provide initial and ongoing learning opportunities in the OR for EMS providers in their catchment areas.

Quality Assurance and Improvement

Whatever the levels of training or particular skills employed within an EMS system, medical directors, educators, and administrators should monitor performance and look for opportunities for improvement. Historically, the most common airway metric has been overall intubation success rate, but this may not be the best measure of quality. Take this scenario: System A has a 99% overall success rate but only a 40% first-pass success rate, and 20% of cases become hypoxic or require three or more attempts, whereas system B has an 80% first-pass success rate with an overall success rate of 90% and no hypoxia by moving to an SGA after two failed attempts. By the classic metric of overall intubation success, system A has better performance than system B, yet many would argue that system B is practicing better prehospital medicine.

Because true outcome data are often hard to obtain, EMS systems that perform MFAM should at a minimum be measuring known surrogate markers of outcome in patients with head injury, such as hypoxemia, hypotension, and hyperventilation. One proposed quality assurance metric is Definitive Airway Sans Hypoxia/Hypotension on First Attempt (DASH-1A). This metric requires the collection of objective data from monitors that record data points every few seconds. One landmark study from San Diego demonstrated very high rates of desaturation when such data collection methods were used. An aggressive continuous quality improvement program in a large air medical system has been shown to improve first-pass success and minimize complications.

Of course, focusing on intubation excludes the much larger population of patients managed with basic life support (BLS) maneuvers. One method to “level the playing field” in quality assurance is direct subjective observation of patient care in the field by medical directors, EMS physicians, and supervisors.

Airway Management Issues by Specific Clinical Situation

Cardiac Arrest

In the majority of advanced life support (ALS) EMS systems worldwide, MFAM is not authorized and invasive airway management is primarily performed during out-of-hospital cardiac arrest (OHCA) resuscitation. Some systems exclusively utilize SGAs because of low intubation success rates in this patient population, and to avoid lengthy interruptions in chest compressions. Other systems and experts strongly believe intubation is better for OHCA management and that high first-pass success rates can be still be favorable, especially with the use of video-assisted laryngoscopy (VAL).

Two large studies now shed light on this issue. A multicenter US trial cluster randomized over 3000 patients in OHCA to airway management with either tracheal intubation or a laryngeal tube. First-pass success was 51.6% with intubation and 90.3% for the laryngeal tube. Survival at 72 hours and neurologic status at discharge were both improved in those patients managed with a laryngeal tube. Another multicenter trial in the UK cluster randomized almost 9300 patients with OHCA to airway management with either tracheal intubation or an i _- gel, an SGA. Airway management was successful within two attempts (first attempt not reported) for 79% of intubations and 87.4% of SGAs. Favorable functional outcomes were not different between the two groups at 30 days. Interestingly, aspiration rates were not different between patients managed with an SGA or intubation in either of these trials, suggesting that many patients had aspirated prior to airway management and/or that SGAs do provide some aspiration protection. Taken together, these two large studies support SGAs as primary airways in OHCA, especially if intubation success rates are comparable. Systems that can obtain higher first-pass success rates despite the challenges of airway management in OHCA, including patients positioned on the floor with ongoing chest compressions, may wish to continue that practice. The AHA ACLS updates from 2019 indicate that either approach is acceptable with a 2a level of evidence.

These studies also serve to refute suggestions that SGAs impair blood flow to the brain as seen in a swine managed with SGAs (LT, LMA-Flexible) compared to ETI during induced cardiac arrest. This assertion was countered by a case series of 17 perfusing patients undergoing neck imaging while ventilated with various SGAs. Two blinded neuroradiologists were unable to detect any evidence of mechanical carotid compression in any of these patients, suggesting that there are important differences in swine and human anatomy. Offsetting these concerns is the greater interruption of CPR often inherent with ETI compared with SGA placement.

Interestingly, there is evidence for improved outcomes for OHCA patients managed with BMV over any type of invasive airway ; however, a randomized controlled trial (RCT) was inconclusive. These results are potentially confounded by those patients who had return of spontaneous circulation very early and resumed spontaneous breathing, a group of patients with excellent prognosis. Two studies, however, have also found improved outcomes for patients who underwent BMV after failed intubation or SGA insertion. ^, This may reflect something inherently detrimental from invasive airways, or it may be that it is simply easier to overventilate with an invasive airway compared to BMV. There is not yet enough evidence to abandon invasive airway management altogether, but we should definitely focus on strategies to avoid overventilation and subsequent impairment of venous return and cardiac output.

Trauma

Critically injured patients often present with secretions, blood, or vomit in their airway; hypoxemia; and/or cervical spine injury, making airway management exceedingly complex and difficult. Initial focus should, therefore, be on basic measures, such as positioning, suctioning, oxygen administration, and BMV. Concerns for cervical spine injury should not preclude allowing patients to sit upright, if best for the airway. A surgical airway should be considered immediately for patients who have catastrophic injuries that preclude airway management via the mouth or when the patient has trismus and providers do not have access to MFAM.

MFAM practitioners may consider RSI or rapid sequence airway (RSA; see “Rapid Sequence Airway”) for severely injured patients who are not moribund, if it does not create substantial delays. Median prehospital scene times of 42 and 68 minutes have been reported, which raises the question of whether such delays are preventable and/or justifiable. ^, Results from prehospital studies of MFAM in patients with severe traumatic brain injury are very mixed, ranging from worse outcomes to improved outcomes, as compared with BLS management. Only one RCT has been performed, which reported improved outcomes with RSI, but these results have recently been questioned. Outcomes seem to be most closely tied to severity of injury and management of ventilation and hypoxemia on hospital arrival than on a specific mode of positive-pressure ventilation (PPV). ^, In patients with severe head injury, the emphasis must be on avoiding hypoxemia, hyperventilation, and hypotension regardless of how the airway is managed. There is no compelling evidence to support more widespread use of MFAM in this patient population.

It is worth noting that trauma patients who will tolerate invasive airway management without medications are usually in cardiac arrest or a moribund peri-arrest state. These patients generally have poor outcomes regardless of airway management and should be transported without delay, if resuscitation and transport are indicated. ^,

Pediatric Intubation

The weight of evidence, including RCTs, indicates that out-of-hospital intubation of the pediatric patient does not improve survival in cardiac arrest when compared with BMV, although prehospital pediatric intubation has not been adequately compared with SGAs. Some EMS jurisdictions, such as Los Angeles and Orange counties in California and the entire state of New Mexico, have restricted pediatric intubation by paramedics.

Reasons why pediatric intubation may be particularly challenging in this setting include anatomic differences that are unfamiliar to providers, the added stress involved with critical pediatric patients, and limited provider exposure to these procedures during initial training and ongoing clinical practice. In air medical transport, only 5% of intubation cases may be for patients 14 years of age or younger. A ground-based RSI study in a large metropolitan area with a population over 2 million reported only 299 prehospital intubation cases in 6.3 years; their first-pass success was 66% overall, 53% for infants, and 56% for children in cardiac arrest. This region reports that, on average, paramedic students perform six pediatric intubations during training, which we suspect far exceeds the national average. Another ground-based pediatric RSI study from Australia reports much higher success rates, but only 109 procedures were performed over 9 years despite a population of over 6 million and an outcome benefit could not be determined. Evidence suggests that physician-based prehospital teams have higher success rates and fewer complications when performing prehospital pediatric intubations, although such teams are uncommon in the United States.

Given the infrequent need for this procedure, the difficulty maintaining competence, and the excellent pediatric SGAs now available, it is reasonable for systems and medical directors to withhold pediatric intubation pending further research. Systems that continue to perform pediatric intubation, and particularly pediatric MFAM, should carefully track their success rates, complications, and outcomes and create processes to ensure the safety of this vulnerable population.

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