On a stormy night in the countryside, a 72-year-old male driver falls asleep at the wheel and strays into on-coming traffic. A transport truck trying to avoid him strikes his small car. The car is crushed and the driver is trapped inside. Emergency Medical Services (EMS) are activated. Basic life support (BLS) medics and fire fighters arrive on scene within 10 minutes. The patient is conscious with a Glasgow Coma Score of 13, BP 80/40 mm Hg, HR 100 bpm, RR 26 breaths per minute, and O₂ saturations of 82% prior to oxygen therapy.

What Level of Airway Management Can We Expect From Pre-Hospital Care Providers?

“A” is the cornerstone in the ABCs, which form the foundation of BLS training for all pre-hospital care providers. The type of training and skill sets varies significantly from country to country and the provider mix may be different from one jurisdiction to another within a country. For clarity, we will define four discrete levels of airway management provided in an EMS system. Each level assumes proficiency in the skills of the previous:

• 
  

  First aid providers or “First Responders”—trained to apply supplemental O₂ by face mask and perform artificial ventilation, typically bag-mask-ventilation (BMV), although in some jurisdictions extraglottic devices (EGDs) may be preferred at this level as first-line devices in place of BMV. Airway adjuncts at this level may include oral- and naso-pharyngeal airways.

  
  
• 
  

  BLS providers—more experienced with BMV, and these providers use EGDs, particularly Combitube™, King LT™, and Laryngeal Mask Airways (LMA) in some systems.

  
  
• 
  

  Advanced life support (ALS) providers—typically perform laryngoscopy (direct or indirect) and endotracheal intubation, with or without the use of facilitating drugs, such as sedative-hypnotics and neuromuscular blocking agents. Emergency cricothyrotomy training is often included at this level.

  
  
• 
  

  Critical care providers (e.g., typically Air Medical Transport or Critical Care Transport team members)—are permitted to perform rapid sequence intubation (RSI) using direct laryngoscope and usually other advanced airway techniques such as indirect laryngoscopy (e.g., video-laryngoscopy) and cricothyrotomy. In some jurisdictions (most notably Europe and Australia), teams include other health care professionals, including registered nurses and physicians, as members of these multidisciplinary teams.

How Are Airway Management Protocols and Equipment Determined in Pre-Hospital Care Systems?

In most North American systems, pre-hospital care providers perform delegated medical acts based on standardized medical protocols. In many European systems, physicians may be the usual pre-hospital care providers and, therefore, are less likely dependent on protocols. While protocols ought to reflect best clinical evidence, from a practical perspective they are often limited by cost, training, competency maintenance, and space constraints. Over the past several years, there has been a movement in some jurisdictions away from protocols, and more toward treatment guidelines, allowing advanced pre-hospital care providers to exercise clinical judgment when managing airways. These guidelines allow for more flexibility to achieve predefined physiologic goals pertaining to airway management, with less emphasis on technical imperatives formerly used as markers of successful (or unsuccessful) airway management. For example, modern guidelines define successful airway management as the maintenance of oxygenation and ventilation by various means, other than simply placing an endotracheal tube.

Protocols or guidelines approved by the medical director of the EMS system determine the equipment necessary in pre-hospital care practice. The type and range of equipment available for managing the difficult airway in the pre-hospital setting are usually limited when compared to in-hospital settings. Even basic equipment, such as the Endotracheal Tube Introducer (ETI; e.g., the Eschmann Tracheal Introducer, also known as the “gum-elastic bougie”),¹ laryngoscope blades, and endotracheal tubes (ETT) in an array of types and sizes, may be limited. Alternate intubating devices, such as the Intubating Laryngeal Mask Airway (ILMA or LMA-Fastrach™) or lightwands (e.g., Trachlight™), often are not available due to limitations in space, training opportunities, cost, resterilization, and issues of skills maintenance. Rescue devices, such as the esophageal–tracheal Combitube™, LMA, and the LMA-Unique™ (the disposable LMA), and the King LT are becoming more popular because they are relatively inexpensive, disposable, and are considered easier to use by pre-hospital care providers at varied levels of training.^2,3 However, extraglottic ventilation devices may not be appropriate in some clinical situations, particularly if adequate ventilation calls for an increase in peak airway pressure beyond the capabilities of a device to achieve an adequate seal, if the patient is sufficiently responsive to reject the device, or if protection against aspiration is preferred.⁴ Surgical airway management devices⁵ must be available in any system providing RSI. Critical Care EMS systems often differ from many ground systems because they carry more advanced equipment, such as the GlideScope™ video-laryngoscope, or other devices.

What Unique Environmental Considerations Do Pre-Hospital Care Providers Face When Managing the Airway?

The practitioner managing the airway is often confronted with an array of circumstances unique to the out-of-hospital environment, including:

• 
  

  A chaotic scene;

  
  
• 
  

  A dangerous scene (e.g., flood, fire, radiation, electrical wires down, toxic environment, assailant on the loose, etc.);

  
  
• 
  

  Access to the patient and the airway which may be challenging due to a variety of factors:

  
  
  
  
  • 
    

    an ongoing extrication;

    
    
  • 
    

    position of the patient (e.g., seated, upside down, etc.). In non-trauma airway management, positioning may also present a problem (e.g., intubation performed lying prone and leaning on the elbows). Even with the patient on a stretcher in an ambulance or helicopter, an optimal position for airway management may be difficult to achieve.

  
  
  
  
• 
  

  Other uncontrollable environmental conditions:

  
  
  
  
  • 
    

    darkness inhibits full airway assessment and obscures subtle nonverbal communication cues among providers;

    
    
  • 
    

    bright sunlight may present similar problems, especially when tracheal intubation (TI) is performed using a laryngoscope or a lightwand;

    
    
  • 
    

    extremes of weather may present problems for patients, practitioners, and equipment (e.g., freezing temperature effects on plastic and metal objects).

    
    
  • 
    

    an uncontrolled tactical environment, in which EMS may be deployed with police and be required to limit access to patients, or limit interventions performed in the various phases of tactical emergency casualty care;

    
    
  • 
    

    spectators, family, or friends of patients may require skilled handling.

  
  
  
  
• 
  

  Lack of other essential equipment for airway management, for example, suction;

  
  
• 
  

  Uncontrolled human behavior in the pre-hospital setting may further interfere with airway management decisions and procedures:

  
  
  
  
  • 
    

    distraught relatives challenging the focus of pre-hospital care providers;

    
    
  • 
    

    knowledgeable and skilled assistants may be unavailable;

    
    
  • 
    

    well-meaning first-aiders or bystander physicians may hamper efforts with inappropriately timed or out-of-context comments or actions.

  
  

Finally, management of an airway in the pre-hospital environment may have to be carried out amid the most adverse of surroundings and circumstances, for example, a crime scene, on a dance floor, in a stadium, etc.

Back to our case: ALS responders arrive on the scene 15 minutes later. The patient’s level of consciousness is decreasing and he remains hypotensive. BLS providers have skillfully assisted ventilations with the BMV while other skilled rescuers attempt to extricate the patient from the wreckage. The GCS is now 9, BP 80/40 mm Hg, HR 120 bpm, and O₂ saturation 88%.

What Are the Patient Factors That Influence Airway Management Decisions of a Pre-Hospital Care Provider?

There are three related elements governing airway management in the field environment: time, anatomy, and (patho-) physiology (i.e., the clinical state of the patient).

Time Factors: When Is It Better to Wait?

All emergency airway management situations share this feature. In other words, they are “context sensitive” (see Chapter 7). It is well appreciated that geographic proximity to a hospital or trauma center does not correlate with out-of-hospital time (e.g., extrication delays), and as such, the pre-hospital care provider must often differentiate between an “indication” for a given airway management technique, and the “need” to actually perform that intervention. Consider, for example, the following three cases:

• 
  

  A 40-year-old male with sudden collapse two blocks away from a hospital, GCS 6, with no cough or swallowing reflex, O₂ saturations of 99%, and normal airway anatomy;

  
  
• 
  

  The same 40-year-old male with sudden collapse, on a mountain side, 2 hours away from the nearest hospital, GCS 6, with no cough or swallowing reflex, O₂ saturations of 99%, normal airway anatomy, and the only means to extricate the patient is via Helicopter Emergency Medical Services (HEMS) response, or;

  
  
• 
  

  The same 40-year-old man in a house fire who has stridor, O₂ saturations of 70%, and evidence of upper airway burns.

In the first patient above, the decision to intubate immediately will depend on the anatomical assessment and time considerations. For example, if the transport time to a hospital is very short, it might be reasonable to wait (i.e., oxygenate and ventilate with BMV, protect with suction) until arrival at the ED where more resources are available. Training must emphasize that airway management means gas exchange and it does not always require intubation. We must avoid the trap of the “technical imperative”—just because it can be done, it should be done. In fact, there is growing evidence that in certain situations pre-hospital intubation may not necessarily improve outcome and may be detrimental.^6,7

On the other hand, in the second patient, despite stable physiology and no predictors of difficult anatomy, due to prolonged out-of-hospital time and the anticipation of aeromedical evacuation with limited access to the patient, it would be reasonable to take the time on scene to place an advanced airway for protection during flight and until arrival at a receiving hospital.

Likewise, in the third patient, with predicted difficult laryngoscopy and anticipated progression of airway edema, time is critical. A quick decision must be made and the provider must confidently follow the Emergency Difficult Airway Algorithm (Figures 2.10 and 2.13 in Chapter 2).

Anatomic Factors: How to Predict Difficulties in Different Airway Management Techniques?

The airway assessment is essentially an attempt to predict difficult direct and indirect laryngoscopy and intubation, difficult BMV, difficult EGD placement, and difficult cricothyrotomy based on an examination of external anatomic features (see sections “Difficult BMV: MOANS,” “Difficult DL Intubation: LEMON,” “Difficult VL intubation: CRANE,” “Difficult Use of an EGD: RODS,” “Difficult Cricothyrotomy: SHORT” in Chapter 1). While recognizing that it may not be possible to assess the airway of some patients (e.g., unresponsive patients), this evaluation is as crucial a component of pre-hospital airway management as it is in hospital. It permits the airway practitioner to make appropriate airway management plans (Plans A, B, and C) that are most likely to be successful.

The patient with acceptable oxygen saturations and a short transport time, with or without predictors of difficult laryngoscopy and intubation, might be better served by a rapid transport to the nearest ED with more resources. This reflects context-specific decision balancing technical abilities (i.e., I can intubate) with physiologic goals (i.e., the patient is oxygenating and ventilating adequately), but also takes into consideration the poor predictive value of some of our airway assessment tools. In other words, though one may have predictors of easy direct laryngoscopy, once C-spine precautions are put in place, the patient may in fact be difficult to intubate through standard means. Should clinical or time considerations preclude rapid transport for in-hospital airway management, the Emergency Difficult Airway Algorithm directs one to weigh carefully whether RSI, sedation, or awake intubation would be most appropriate. If any of these is unsuccessful, one should move promptly to the Failed Airway Algorithm (Figure 2.11 in Chapter 2). Situations in which difficulty is predicted and airway management is urgently indicated may be better handled by an early call through dispatch for scene backup.

Most pre-hospital ALS and critical care providers are familiar with the necessity for an airway evaluation prior to each intubation, particularly if medications are to be administered to facilitate the procedure. However, this may be limited to predictors of difficult laryngoscopy and intubation rather than difficulty in other airway techniques (see Chapter 1), such as video-laryngoscopy, EGDs, difficult BMV, and difficult surgical airway.

Clinical Factors: How Do the Clinical Condition and Presumed Diagnosis Affect Airway Management Decisions?

There are two clinical considerations in managing a difficult airway in the field setting: the indication for intubation and the underlying pathophysiology.

Indications for endotracheal intubation in the pre-hospital environment are similar to those in any other emergency.⁸

1. 
   

   failure to maintain adequate oxygenation;

   
   
2. 
   

   failure to maintain adequate ventilation (CO₂ removal);

   
   
3. 
   

   failure to protect the airway;

   
   
4. 
   

   the need for neuromuscular blockade;

   
   
5. 
   

   the anticipated clinical course;

   
   
6. 
   

   uncompensated shock.

In practice, many patients may have more than one indication for endotracheal intubation.

Underlying Pathophysiology: The indications for intubation among various EMS systems may differ. The most common indication (up to two-thirds of all intubations) in a typical ground EMS system is cardiac arrest.⁹ The remainder tend to be split evenly among respiratory failure (asthma, chronic obstructive lung disease, congestive heart failure, pulmonary embolism, pneumonia, anaphylaxis), non-trauma CNS conditions (coma, intracranial bleed/stroke, seizure, overdose), trauma (head injury, chest injury, neck injury, blood loss causing shock), and shock states (sepsis, cardiogenic, hypovolemic).

Helicopter EMS (HEMS) (also called rotorcraft Air Medical Transport [AMT]) rarely responds to primary cardiac arrest calls. These critical care teams are trained to manage patients who may require more advanced airway procedures, or those with more complex pathophysiology.

In certain circumstances, a patient may have an indication for intubation but circumstances, such as predicted difficult airway and a short transport time to the ED, may sanction BMV and suction until intubation is possible. The weighing of “risk versus benefit” is illustrated in the example above (40-year-old man with a collapse and a short transport time vs. long transport time, vs. burn with time-sensitive pressures). Even in the face of an accepted indication for intubation, the potential benefits of pre-hospital intubation must be weighed within the context of the environment, time, anatomy, and pathophysiology.

What Alternatives Do Pre-Hospital Providers Have in Managing a Difficult Airway?

Effective BMV technique (including two-handed mask hold requiring two providers if available or necessary) is essential to the pre-hospital care provider, particularly when the airway could be difficult and the transport time relatively brief.

Despite considerable controversy in the literature, the gold standard for definitive airway control remains the correct intratracheal placement of a cuffed ETT. According to the “Recommended Guidelines for Uniform Reporting of Data from Out-Of-Hospital Airway Management,”¹⁰ there are four methods by which this can be achieved: direct oral laryngoscopy and intubation, nasotracheal intubation, TI via an oral rescue techniques (e.g., intubating LMA), and surgical rescue techniques (transtracheal jet ventilation and cricothyrotomy). These four methods may each be modified by five variables:

• 
  

  oral approach—no facilitating sedative drugs or paralytics;

  
  
• 
  

  nasal approach—no facilitating sedative drugs or paralytics;

  
  
• 
  

  sedation-facilitated intubation—without the use of paralytics;

  
  
• 
  

  RSI—with the use of paralytics and induction agents;

  
  
• 
  

  other intubation techniques (e.g., digital, lightwand, etc.).

The actual number of options available to a given EMS system is driven by evidence-guided, rationale-based medical oversight, and limited by local culture, protocols, training, and equipment.

There is ample evidence that endotracheal intubation is not a benign intervention in the hands of inexperienced personnel.^11–13 Newer airway devices such as the LMA, King LT™, and the Combitube™ have been introduced and validated in the pre-hospital care setting.^4,14–20 These devices may be employed in two ways: as an alternative to endotracheal intubation in the cardiac arrest (or deeply comatose) patient by all level of providers^4,15,19,21 or as a rescue device in the setting of failed intubation by ALS or critical care providers.^14,16

An emerging alternative to endotracheal intubation in the respiratory failure patient is pre-hospital noninvasive positive pressure ventilation (NIPPV). Several case series have shown continuous positive airway pressure (CPAP) or bi-level ventilation (BiPAP) to be feasible and potentially beneficial in the pre-hospital setting.^22–24 Current evidence supports the use of CPAP in the pre-hospital setting for high-pressure pulmonary edema (i.e., CHF).²⁵ Pre-hospital critical care teams will often also use BiPAP in hypercapneic respiratory failure (e.g., secondary to COPD).²⁶ Furthermore, based on case series and physiological principles, BiPAP can be used as a denitrogenation technique by critical care paramedics prior to transitioning to endotracheal intubation and formal mechanical ventilation.^27,28

What Are the Challenges in Terminology Associated With Pre-Hospital Airway Management?

Increasing attention is being paid to the many aspects of pre-hospital airway management. Research, discussion, education, innovation in both devices and approaches have expanded. It is quite apparent that one approach does not fit all clinical situations in the ideal in-hospital environment, so it is folly to assume that it is any less complex in the pre-hospital setting in which there are more variables to consider. The clinical choices involved in airway management in the field setting may well be limited by personnel training, the realities of maintaining competence, and the devices and drugs available to field personnel. Using “patient outcome,” rather than procedural outcome as the measure of success of airway management, one can begin to construct some useful definitions.

Inaccurate use of terms in three different risk/benefit clinical issues often make the selection of the best airway management method to proceed with in any clinical situation difficult. The three spectrums of risk/benefit are:

1. 
   

   Pharmacology: which drug or combination of drugs should be administered;

   
   
2. 
   

   Procedure/equipment: what procedure/equipment to use to facilitate the placement of a device;

   
   
3. 
   

   Device: what device is most appropriate to oxygenate/ventilate the patient.

These confusions often lead to incorrect comparisons in research studies. If these three components are carefully separated from each other, it becomes apparent that interpretation of the results of a study comparing RSI versus EGDs as part of a Rapid Sequence Airway is difficult.²⁹ The exact terminology eventually used is less important than the need to achieve consensus and consistency. However, separating these three decision points will be imperative, recognizing that the initial decision or plan may change with evolving clinical situations.

The most obvious use of vague terminology is in the area of the pharmacology of airway management. Many drugs and combinations of drugs can be used in facilitating pre-hospital airway procedures, particularly in what has been called “Rapid Sequence Intubation,”³⁰ “Rapid Sequence Airway,”²⁹ “Drug-Facilitated Intubation,”³¹ “Drug-Assisted Intubation,”³² “Deep Sedation versus Awake Intubation,”³³ and others. For simplicity, these variations can be grouped into three categories:

1. 
   

   Rapid Sequence, in which paralysis is preceded by an induction agent appropriate to the clinical state of the patient and the situation;

   
   
2. 
   

   Sedation, in which the intent is to provide sedation, analgesia, or both;

   
   
3. 
   

   Awake, in which topical anesthesia of the upper airway allows for lower sedative dose.

It might be said that clinically the difference between 2 and 3 above is “qualitative”; but the intent, and therefore the use of drugs, is clearly different. A lack of understanding of these differences can be both educationally confusing and clinically catastrophic. The use of deep sedation in the patient with a difficult airway without backup plans and essential equipment can lead to apnea, aspiration, profound physiologic disturbances, a failed airway and ultimately, poor patient outcomes.

Should TI Even be Performed in the Field?

Both in and out of the hospital, inappropriate ventilation and inadequate oxygenation have been identified as primary contributors to preventable morbidity and mortality. It would seem reasonable, then, to assume that endotracheal intubation should be the gold standard in pre-hospital airway management. However, there has been considerable controversy as to whether patients requiring endotracheal intubation should have TI performed in the field or deferred until arrival at hospital. There are several issues that arise from this controversy:

• 
  

  Trauma victims—There continues to be skepticism as to whether the intubation of trauma victims in the field improves survival. During the 1980s, it was generally felt that invasive airway management was ineffective in improving survival in urban environments but might be effective in longer transport environments.³⁴ Studies published during the 1990s gave conflicting results.^35–40 It might, at the very least, be anticipated that endotracheal intubation would be advantageous in patients with severe head injury. Early studies provided no clear direction^7,41–46 and a recent large trauma registry study found that pre-hospital intubation was associated with adverse outcomes after severe traumatic brain injury (TBI).⁷ However, covariate adjustment in the same study suggests that management of the airway by an air medical team may improve outcomes. Unfortunately, as Zink and Maio⁴⁷ pointed out in an accompanying editorial, this is a retrospective association rather than a causation study. Importantly, these TBI studies raise questions about the downstream effects of drug choices, drug dosages, the physiology of transitioning from negative pressure-spontaneous ventilation to positive pressure ventilation, the type of positive pressure ventilation employed, and positive end-expiratory pressure (PEEP) among other things.

  
  
• 
  

  Cardiac Arrest—In cardiac arrest patients, the issue of efficacy of ETT remains unresolved.^48–52 To further add to the controversy, a study involving out-of-hospital cardiac arrest victims showed that patients who received CPR with only chest compressions had comparable survival outcome compared to those who received chest compression and mouth-to-mouth ventilation.⁵³ A large prospective study to determine the incremented benefit of introducing ALS (including intubation) to a previously optimized system did not show a mortality benefit in cardiac arrest patients.⁵⁴ Furthermore, other observational studies have reported signals that advanced airway management is an independent predictor of worse neurological recovery after out-of-hospital cardiac arrest.⁵⁵

  
  
• 
  

  Children—Early studies in children showed that TI by paramedics was associated with higher failure and complication rates than that in adults.⁵⁶ Results of subsequent studies have confirmed these early findings.^6,36,57–60 The only prospective trial to investigate the effectiveness of ground paramedic in performing TI in children showed that there was no increase in survival following TI as compared to that in the group treated with BMV.⁶ This same study revealed concerns about TI displacement and inability to recognize this catastrophic complication.⁶ Many authorities maintain that these latter studies reflect inadequate training of paramedical personnel in TI of children. Furthermore, the literature does not resolve whether the field intubation of children with head injuries improves their outcome.^61,62 In the final analysis, the emergency intubation of children is an uncommon and anxiety-provoking event for most paramedics. Both of these factors are likely to increase performance stress and failure rates, compared to the intubation of adults.

Recent studies have presented data and formed conclusions that challenge the basic, time-honored dogma of EMS airway management and question the best approach to the compromised airway in the pre-hospital environment. Furthermore, the development of other airway adjuncts (e.g., Combitube™, King LT™, LMA™, and CPAP) coupled with a reemphasis on standard BMV has changed the priority for pre-hospital endotracheal intubation and is a clear sign of maturity and success of the EMS.

It is becoming clear that airway management training and maintenance-of-competency programs are vital, as they will affect both the psychomotor skill development, psychomotor skill decay, and context-specific decision making that reflects current best practice. Other issues such as equipment availability, the air versus ground environment, and the logistics associated with rural as opposed to urban critical care transport/EMS suggest that a single, rigid approach to EMS airway management is inappropriate and cannot be supported.

Now to our case: ALS medics are unsuccessful in obtaining a definitive airway. Two IVs have been placed and a normal saline (NS) bolus administered. The patient has just been extricated (30 minutes later), boarded, and collared. The critical care crew has just landed at the scene. The patient now has a GCS of 7, a clenched jaw, BP 90/60 mm Hg, HR 120 bpm, and an O₂ saturation of 90% with assisted BMV with oxygen supplement.

Pre-Hospital RSI—What Does the Evidence Show?

The HEMS crew on the scene has the training and capability to perform an RSI on appropriate patients as part of their clinical mandate. This includes the use of an induction agent, followed in rapid sequence by a neuromuscular blocking agent and vasoactive agents (e.g., phenylephrine), in order to optimize intubating conditions and peri-intubation physiology, in order to increase the chances of successful endotracheal intubation and smooth transition to positive pressure ventilation.³⁰

Until recently, the evidence in the EMS literature has not supported the use of RSI. Several recent, well-designed studies of ground systems have consistently shown suboptimal outcomes, or no difference in outcome, in patients suffering acute severe TBI in whom RSI is used to facilitate endotracheal intubation.^6,7,12,41,63 Head injury was deliberately chosen in these studies because prior reports have suggested that optimal oxygenation and ventilation of these patients improve outcomes. Therefore, it was assumed that successful endotracheal intubation would demonstrate a benefit.⁶⁴ A case-control study of pre-hospital RSI of the severely head injured patients in 2003 identified increased mortality and morbidity in the RSI group when compared to patients who had TI performed in the ED following transport without RSI.⁶³ Though this study had methodological limitations that preclude generalizing their findings to all EMS systems that use RSI, an important message was the reemphasis on protecting physiologic goals during airway management (i.e., SpO₂, ET CO₂, etc. by any means), and de-emphasizing technical goals (i.e., achieving TI).