I Introduction

Prehospital airway management ranges from the use of basic airway maneuvers in the management of the unresponsive patient to the need for a surgical airway (i.e., cricothyrotomy) in the “cannot intubate, cannot ventilate” (CICV) situation. Because transport time from the scene of an emergency is often delayed by distance, traffic conditions, and victim extrication, skilled providers can be assets to the most seriously ill or injured patients. However, the scope of practice for emergency medical services (EMS) providers throughout North America varies broadly. In some systems, airway management is provided exclusively by basic emergency medical technicians (EMTs) who are not trained in endotracheal intubation, cricothyrotomy, or extraglottic airway devices, leaving the airway uncontrolled and susceptible to gastric inflation and aspiration induced by bag-mask ventilation, which produces a difficult airway or complete airway obstruction that may be impossible to resolve. Other systems use highly trained paramedics and allow the use of medication-assisted intubation and a variety of airway devices, which opens the door to potential clinical errors and complications such as airway trauma, misplaced tubes, and unrecognized esophageal intubation.

The variability in EMS systems throughout North America is dictated by several factors, including historical system design, state laws, system size, volunteer versus paid provider status, physicians’ preferences, and economic issues. For example, in large urban systems, a lack of high-quality medical direction and monitoring may make medication-assisted intubation difficult to successfully implement and sustain. In rural systems, the frequency of intubation may be low, making it difficult to acquire and maintain the necessary skill levels. Prehospital intubation can be challenging compared with the in-hospital environment. EMS providers work in a variety of conditions that complicate the task of airway management, ventilation, and oxygenation. Extreme weather, enclosed working spaces (e.g., cars, small rooms, hallways), bystander distractions, and a variety of other challenging situations face the EMT and paramedic.¹

Some aspects of an EMS system design are essential for maximizing provider competency. The frequency with which any provider performs advanced airway management is critical for maintaining skill competency.^2,³ Some systems have reported very low rates of intubation, especially for pediatric patients.⁴^–⁶ How can competency be maintained when providers intubate three or four times per year?^2,⁷^–⁹ Should they intubate when the frequency is so low? System medical directors must answer these questions when designing, evaluating, or refining an EMS system. Physicians must be artful in selecting airway strategies, training providers, monitoring interventions, and maintaining quality.⁷

II History of Airway Management by Emergency Medical Services

Before the 1950s, prehospital airway management was provided by relatively unskilled providers in most EMS systems throughout the United States. Progressive systems of the time provided bag-mask ventilation with an oropharyngeal or nasopharyngeal airway. In some cases, training was limited to basic first aid without training in airway adjuncts.¹⁰^–¹²

In the 1960s, the quality of prehospital care came into focus with publication of Accidental Death and Disability: The Neglected Disease of Modern Society by the National Research Council and development of a national standards curriculum for EMTs that defined minimal training and equipment.¹³ Standards included training in the use of basic equipment such as bag-mask ventilation, oropharyngeal and nasopharyngeal airways, and suction.

In the late 1960s, the concept of advanced-level care was introduced first in Northern Ireland under the leadership of Dr. Frank Pantridge and subsequently implemented in several cities in the United States, including New York, Miami, Seattle, and Pittsburgh. In these systems, paramedics were trained to provide endotracheal intubation in the field along with other advanced life support interventions. Most programs included training in the operating room under the supervision of an anesthesiologist. This innovation was helpful for victims of respiratory and cardiac arrest who were unresponsive. However, there were still challenges for patients with respiratory failure, shock, or other premorbid conditions who were responsive but in need of definitive airway management. In the absence of sedation and rapid-sequence intubation (RSI) protocols, intubation for these conditions was often performed by employing brutane—the use of force to assist in performing a medical procedure, such as intubating the trachea.

In the 1970s, some paramedic systems began to use neuromuscular blocking drugs to manage patients’ airways with great success. These programs provided significant medical oversight that included monitoring successful outcomes and complications associated with endotracheal intubations.¹⁴ System medical directors had concerns about the use of medication-assisted intubation, including the issue of increased time at the scene by paramedics and complications such as unrecognized esophageal intubation.¹⁵^–¹⁷

Drug-assisted intubation is a relatively new idea that is used on a limited basis in EMS systems in North America. Because success rates for drug-assisted endotracheal intubation vary greatly among EMS groups, it is not routinely recommended.^8,⁹ However, the National Association of EMS Physicians has developed guidelines for implementing drug-assisted intubation programs that include provider training, patient selection, use of standardized protocols and resources for storage and delivery of medications, training in verification and monitoring of end-tidal carbon dioxide, a continuous quality improvement program, and research on a system level to verify effectiveness of the program.¹⁸

Alternative airway devices have been used in prehospital care since the advent of prehospital advanced life support. Devices include the esophageal obturator, gastric tube airway, esophageal-tracheal Combitube, and King laryngeal tube (LT) airway. Many studies have demonstrated their relative effectiveness compared with bag-mask ventilation and endotracheal intubation (ETI) ventilation.¹⁹^–²¹

III Prehospital Care of Airway Patients

Prehospital care of airway patients addresses the spectrum of clinical conditions faced in emergency departments, critical care units, and operating rooms. In the ideal world, providers would be prepared to deal with airway management and ventilation for all possible conditions, but the scope of practice and provider skill levels vary in North America. In other parts of the world, where physicians staff EMS vehicles, skill levels may be more uniform. At the entry level of emergency medical response (EMT-Basic), forced positive pressure with bag-mask ventilation and rapid transport may be the only options available. ETI has been considered the gold standard for definitive airway management, but the diverse skill levels found in prehospital care and the use of extraglottic airway devices in EMS have challenged this idea. High rates of unrecognized esophageal or hypopharyngeal placement or dislodgement have raised concerns about ETI as a default strategy for EMS providers.^16,¹⁷

A Basic Airway Management

Most EMS providers are equipped to manage the patient who is unresponsive or in respiratory or cardiac arrest. Since the late 1960s, EMT-Basic training has included the use of oropharyngeal and nasopharyngeal airways, bag-mask ventilation, and suctioning. Training has emphasized appropriate mask seal, controlled volumes and inspiratory times, and the avoidance of hyperventilation in cardiac arrest and shock states.^11,²²^–²⁴

Complete airway obstruction by acute epiglottitis, foreign bodies, laryngeal-tracheal trauma, airway hematomas, and numerous other conditions is a challenge in hospitals staffed by highly skilled airway managers and particularly in the prehospital environment, where the necessary tools and skills may not be available. In these unfavorable settings, rapid transport to surgical intervention may be the only practical option. In rural environments where transport times are prolonged, upper airway obstruction is more likely to be a fatal condition.

B Extraglottic Airway Devices

Use of the King LT as a primary and alternative airway device has been an effective prehospital airway strategy.^17,^25,²⁶ Because alternative airway devices do not provide definitive protection against aspiration, they typically are used temporarily until ETI can be achieved in the field or in the emergency department. In one case report, the King LT resulted in tongue engorgement when left in place for approximately 3 hours.²⁷

The double-lumen esophageal-tracheal Combitube is an alternative airway device commonly used in EMS. It has been used by Basic and Advanced EMTs as a primary airway device and by paramedics as a rescue device. Effectiveness of the Combitube has varied among studies in prehospital care. Cady and colleagues found it had no effect on patient outcomes compared with ETI.²⁸ In a study of prehospital physicians, the Combitube was superior to ETI in the management of cardiopulmonary arrest.²⁹ When the King LT and Combitube were compared in a study of EMS providers, nurses, and physicians, the King LT was inserted faster and preferred by 96% of the participants.³⁰

For patients with acute respiratory distress and acute pulmonary edema, continuous positive airway pressure (CPAP) has significantly improved outcomes and reduced the need for intubation in prehospital care.³¹ CPAP has also proved to be cost-effective in the prehospital environment.³²

Some studies have shown increased morbidity rates with prehospital intubation. Others have demonstrated no increase in mortality rates despite significant errors such as esophageal intubation, dislodgement, or failed ETI.³³ A study of patients with acute respiratory distress showed a decrease in mortality rates when advanced interventions such as ETI were used in the prehospital environment.³³

Some investigators think that ETI should not be standard operating procedure for EMS systems. Variables cited as key factors in determining whether a given EMS system should use ETI include low case exposure and inadequate operating room training for paramedics and paramedic students. However, it has been shown that if a minimum number of intubations is used as the criterion to permit ETI in the field, the overall numbers of ETI performed in the field decrease because fewer providers meet the minimum number needed to permit continued performance of the skill.² Additionally, supraglottic devices have demonstrated equivalency to ETI in many studies, and many advocate using alternative strategies for ensuring the success rates for intubations, such as simulation and cadaver training.^21,^34,³⁵ When time in the operating room is made available to paramedics, it can be a significant training adjunct for clinical practice.

The U.S. National Highway Traffic Safety Administration (NHTSA) requires only five intubations to be eligible for paramedic certification.²²^–²⁴ This level is well below the recommended level of 35 ETIs for emergency medicine residents. Anesthesiology residents must perform between 45 and 60 ETIs to achieve at least a 90% success rate in the controlled setting of the operating room.³⁶ Wang and colleagues calculated the learning curves for paramedic students performing ETI and found that at 20 to 25 ETIs in live subjects must be performed to achieve success rates of at least 90%.² This finding argues that paramedics with only five ETIs during training may have little skill in performing intubations.

Medical oversight is a critical part of any EMS airway program. Direction by physicians has enhanced the cognitive (though not the technical) skills of paramedics and improved patient selection.⁷

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