Prehospital airway management: Intubation, devices, and controversies

Introduction

Prehospital trauma airway management is probably the biggest challenge faced by emergency medical services (EMS) providers. These professionals must acquire and maintain essential skills to adequately manage airway problems at the scene and during transport of trauma victims to trauma centers.

Options for airway management have different levels of invasiveness and complexity with different technologies and required levels of expertise. Emergency airway management in trauma patients is also associated with a significant complication rate, reaching 13% in one series. Endotracheal intubation is the definitive method of emergency airway management. However, to acquire such a skill requires significant training and practice. Although the emergency medical technician (EMT)-basic curriculum contains an advanced airway module, the low frequency of these procedures makes it difficult for these professionals to maintain proficiency. In Europe and Australasia, there is increasing use of prehospital physicians with advanced airway skills, who have had a reported success rate in intubation of 98.8% versus 91.7% for nonphysicians. In most U.S. trauma systems, paramedics and flight nurses are the only professionals performing rapid sequence intubation (RSI). Therefore, there is a need for simpler ways to maintain a patent airway by all EMTs, until the patient is delivered to a hospital. Several devices are now available and have been used by prehospital personnel when endotracheal intubation is not practical or possible. These alternate methods include bag-valve-mask with oral and nasopharyngeal airways, or supraglottic airways such as the laryngeal mask airway (LMA), the esophageal-tracheal double lumen tube and “Combitube” and the laryngeal tube or “laryngeal-tracheal airway” or “King” airway. There are also devices that may increase the likelihood of success for EMT-performed RSI, such as the Eschmann Tracheal Tube Introducer or “bougie” and video laryngoscopes. In some jurisdictions and in situations such as Tactical Combat Casualty Care in the military, or Tactical Emergency Casualty Care for civilian tactical EMS, or in austere environments, EMTs may be trained in some types of surgical airways such as open or needle cricothyroidotomy.

In this chapter, the indications for airway management in the prehospital arena; the different modalities, devices, and techniques; the recognition of a difficult airway; and the associated pitfalls will be discussed.

Diagnosis

Assessing the airway

Obstruction of the airway in a trauma patient may occur rapidly or insidiously, may be partial or complete, and may be progressive or intermittent. Assessment of the airway is a basic EMT skill. Management of the airway takes precedence over all other civilian prehospital interventions, as loss of the airway will result in an unsalvageable patient. The airway is assessed by looking for signs of direct airway trauma such as maxillofacial, neck, or laryngeal trauma. The mouth is examined for foreign objects such as loose teeth, blood, or vomitus. Soot, singed nasal hairs, and carbonaceous sputum suggest thermal trauma to the airway, which may cause swelling and progressive airway obstruction. Anatomical features such as a small jaw, prominent or missing teeth, increased body mass index, reduced neck range of motion, or a beard may indicate there will be increased difficulty in controlling the airway. Listening carefully to the patient who is able to talk yields information about the patency and quality of the airway—the patient who can speak normally provides some reassurance the airway is patent and mentation is normal. Patients who are confused or agitated may have TBI, intoxication, hypoxia, or hypocarbia and may have or progress to airway obstruction. Abnormal sounds such as stridor, gurgling, wheezing, or snoring may be associated with partial or impending airway obstruction. Palpation of the neck can reveal crepitus from subcutaneous air due to direct airway trauma, loose cartilage from laryngeal fracture, or hematomas that can compress the airway.

Initial airway maintenance techniques include the chin-lift or jaw-thrust maneuvers, done while maintaining cervical spine immobilization in the suspected blunt trauma patient. These can both open an airway and reveal whether the airway is being obstructed by the tongue falling back to obstruct the airway in a supine patient. Oropharyngeal airways can be inserted in unconscious patients to ensure a patent upper airway. Tolerance of an oropharyngeal airway usually indicates the patient will require a definitive airway at the trauma center. The majority of unconscious trauma patients are managed with an oropharyngeal airway combined with the bag-valve-mask. Conscious and some semiconscious patients will not tolerate an oropharyngeal airway but will tolerate a nasopharyngeal airway. Trauma patients need supplemental oxygen, and providing a good seal with the face mask to allow 100% oxygen delivery can be difficult in patients with facial hair, a large face, small chin, or obesity. It may require the effort of two or three prehospital personnel to maintain a face mask seal, bag the patient, and maintain in-line cervical spine immobilization. In patients in which bag-valve-mask and oral or nasal airway do not provide adequate oxygenation and ventilation, or when transportation precludes optimal use of the bag-valve-mask, a supraglottic or definitive airway may be required.

Assessment of the airway for difficulty of intubation can be performed using the LEMON assessment ( Table 1 ). The first step is to Look for characteristics that are known to cause difficult intubation or ventilation such as small chin, protruding teeth, or large face. Next the patient is Evaluated using the 3-3-2 Rule, which indicates that the distance between the patient’s open incisor teeth should be at least 3 fingerbreadths, the distance between hyoid bone and the chin should be 3 fingerbreadths, and the distance between the thyroid notch and for the mouth should be at least 2 fingerbreadths. Third, the Mallampati classification is used to assess the oropharynx and conscious patients ( Fig. 1 ). Fourth, look for evidence of Obstruction , including visible and audible signs of conditions that will make laryngoscopy and ventilation difficult, such as direct trauma or burns. Finally, Neck mobility is assessed. In blunt trauma patient wearing a cervical spine collar, it can be anticipated that there will be no permitted neck movement and intubation will be more difficult.

Gaither et al. studied difficult airway predictors in a retrospective cohort of patients that required intubation in the emergency department after failed prehospital attempts or nonattempts. They found that the presence of airway edema was associated with the highest likelihood of failure or nonattempts in the field. Airway edema was followed by airway blood, facial trauma, large tongue, short neck, cervical spine immobilization, vomit, obesity, and a short mandible in decreasing order of airway management difficulty. These effects were also additive, and the likelihood of failure to intubate increased significantly when multiple predictors were present. The study authors suggested an acronym, BE FAST ( Blood , Emesis , Facial trauma, Airway edema, Spinal immobilization or short neck, and large Tongue ), to identify common difficult airway predictors, all of which can also be identified with the use of LEMON described above.

Identifying a difficult airway prevents patient deterioration or death. Alternative devices and strategies should be used when the diagnosis of a difficult airway is made. These include the supraglottic airways such as the LMA, Combitube, or King airway. RSI using paralytics in a patient with a difficult airway in a resource-poor environment can result in a “failed airway” and a “can’t intubate, can’t ventilate” scenario, which may require a surgical airway or may even be impossible to salvage with subsequent death of the patient. It should be remembered that many of the redundancies and backups available in hospitals (additional, experienced personnel, and advanced devices) are not available in the prehospital environment.

Management