EMS Airway Management: Addressing Challenges in Adverse Conditions

Anatomy and Physiology

The airway comprises all anatomical spaces from the nares and oral aperture down to the end of the alveolar tree in the lungs. The airway includes the nose, mouth, pharynx, larynx, trachea, and bronchi—all of which are internally lined with mucous membranes. The vocal cords within the larynx serve as the transition point between the upper and lower airways.

Nose

The nose consists of the external nose and the nasal cavity. The external nose is the most superficial part, composed of cartilage and bone, and it extends posteriorly into the nasal cavity, which is divided into 2 halves by the nasal septum in the midline. Each half of the cavity is bordered by a roof (formed by the nasal, frontal, ethmoid, and sphenoid bones), a floor (formed by the palatine and maxilla bones), and the nasal septum (composed of the ethmoid and vomer bones, along with cartilage). The nose can serve as a conduit for delivering oxygen via a nasal cannula. Alternatively, tracheal tubes or nasopharyngeal airways may be passed through the nares.

Mouth

The mouth consists of the mouth cavity and the vestibule. The oral cavity is bounded anteriorly by the maxilla, mandible, and teeth; superiorly by the hard and soft palate; inferiorly by the mandible and anterior tongue; and posteriorly by the oropharyngeal isthmus. The vestibule is the space surrounding the oral cavity, located between the lips and cheeks on the outside, and the teeth and gums on the inside.

Pharynx

The pharynx is divided into 3 regions—the nasopharynx, oropharynx, and laryngopharynx—arranged from superior to inferior.

• Nasopharynx: The nasopharynx is located directly posterior to the nasal cavity, and it extends from the base of the skull and continues down to the soft palate. This region contains the adenoids (nasopharyngeal tonsils).
• Oropharynx: The oropharynx extends from the soft palate to the tip of the epiglottis, located behind the oropharyngeal isthmus. This region contains the palatine tonsils on either side.
• Laryngopharynx: The laryngopharynx extends from the epiglottis to the inferior border of the cricoid cartilage at the level of the sixth cervical vertebra. The prevertebral fascia and cervical vertebrae lie directly behind the pharynx along its entire length. The pharyngeal walls consist of multiple muscle layers with a complex neurovascular supply. Supraglottic devices, such as laryngeal mask airways, terminate at this level, resting at the epiglottis.

Larynx

The larynx is a complex structure composed of cartilages, ligaments, and muscles. The largest component at the front is the thyroid cartilage, which features a notch that forms the prominent "Adam’s apple." Directly below the thyroid cartilage is the ring-shaped cricoid cartilage. The narrow space between the thyroid and cricoid cartilages is bridged by the cricothyroid ligament. Additionally, the thyrohyoid ligament extends from the upper border of the thyroid cartilage to the hyoid bone, located deep in the neck.

Posterior to the thyroid cartilage lies the laryngeal cavity, which houses the upper (false) and lower (true) vocal cords. Effective airway management involves inserting an airway device below the vocal cords, ensuring a secure seal to protect the respiratory exchange zone in the lower airways from vomitus or other debris. This allows for goal-directed oxygenation and, if necessary, positive-pressure ventilation.

Indications

Airway management is commonly indicated in the prehospital setting, particularly when a patient is unable to maintain adequate oxygenation and ventilation or cannot protect their airway due to illness or injury. When selecting a primary method for advanced airway management, it is essential that circumstances allow time for proper visualization, suctioning, and gentle placement of the device. Hypoxia should be avoided, and a physiological “cushion” should provide apneic time without desaturation. Techniques to create this cushion, such as apneic oxygenation and nitrogen washout, should be explored separately.

If the primary method fails, a backup method should be implemented to promptly secure the airway, although without the benefit of a cushion to maintain oxygenation during the apneic period. Backup devices may include video or bougie-assisted laryngoscopy or a laryngeal mask airway. Rescue methods are used sequentially when previous methods fail or as the initial approach when the patient is critically ill, and further delays in oxygenation and ventilation could cause iatrogenic injury. The chosen rescue method should allow for rapid placement and be familiar to the practitioner.

Contraindications

Although adequate oxygenation and ventilation are essential for patient survival, there are no absolute contraindications to airway management. However, some techniques may have relative contraindications in certain clinical contexts. Advanced maneuvers, such as intubation, should only be performed by properly trained providers when the potential benefits in a given clinical context outweigh the risks. Airway manipulation should be minimized in certain scenarios where aggressive prehospital interventions could lead to sudden deterioration, such as in suspected epiglottitis in children, or when a patient has risk factors for difficult intubation and basic maneuvers are sufficient.

Equipment

A wide variety of airway procedures and adjuncts are used, each requiring varying degrees of skill and offering benefits and risks in different clinical contexts. They include:

• Manual airway management maneuvers, such as the head-tilt-chin-lift method or jaw-thrust methods
• Oxygen devices, including high-flow nasal oxygen
• Insertion of oropharyngeal or nasopharyngeal airways
• Bag-valve-mask devices
• Supraglottic airways
• Continuous positive airway pressure devices and noninvasive ventilation
• Direct laryngoscopy with endotracheal intubation
• Nasal intubation
• Rapid sequence intubation with sedatives and paralytics
• Drug-assisted or facilitated intubation without paralytics
• Airway intubation adjuncts, such as bougies, stylets, or video laryngoscopes
• Front-of-neck access, such as needle cricothyrotomy or surgical cricothyrotomy [1]

Personnel

All personnel working in EMS should have basic knowledge of and training in airway management. Individuals responsible for performing advanced interventions, such as intubation, should receive adequate training, gain relevant experience, and participate in ongoing mentoring to maintain their skills. Advanced techniques generally require more than one trained responder, and these procedures should not be performed alone, whenever possible, due to the necessity to administer multiple interventions to patients simultaneously.

Preparation

Formulating a clear treatment plan is crucial, and the responding team should consider patient, personnel, and environmental factors.

• Patient factors: These factors include predictors of a difficult airway, such as facial trauma or vomitus, patient positioning, and physiological and psychological status. psychological status. Whenever possible, these factors should be optimized before proceeding.

• Personnel factors: These factors involve the relative training and experience of the available clinicians, the availability of backup, levels of fatigue and stress, and familiarity with the available equipment.

• Environmental factors: These factors include the time of day, ambient light, temperature, altitude, weather conditions, proximity to healthcare resources (including travel time to the nearest hospital), and the safety of the immediate environment, particularly in tactical or military settings. Monitoring airway adjunct balloon turgor is crucial due to atmospheric pressure changes during flight. Video laryngoscopy equipment may malfunction in extreme temperatures, so backup methods should be readily available in case of malfunction.

Technique or Treatment

Poor Ambient Light

Lighting in the prehospital environment is often suboptimal, which can hinder the proper preparation of airway equipment and impair communication and situational awareness among healthcare team members during the procedure. This can have significant implications for airway management, particularly intubation, which depends on direct visualization of tube placement. Conversely, excessive ambient light can also cause problems, as glare may blind the airway operator, especially when light sources are in the operator’s line of sight, such as during dusk or dawn when the sun is low.

In low-light settings, bystanders or team members can be assigned to position artificial light sources to illuminate the immediate area. Responders should also consider using head-mounted lamps for hands-free lighting. If excessive light interferes with airway management, bystanders and healthcare team members can help facilitate the procedure by using a sheet or tarpaulin to reduce glare. Video laryngoscopy, as opposed to direct laryngoscopy, may be beneficial, although video laryngoscope screens may be difficult to view in broad daylight compared to artificial indoor lighting conditions.[2]

Illumination of the airway during intubation typically depends on the light emitted from the laryngoscope. Batteries and light bulbs should be charged and checked in advance, and it is good practice to have a second laryngoscope readily available to address any last-minute equipment issues.

In the absence of a functioning light source, blind digital intubation, guided solely by the rescuer’s fingers, has been described.[3] A flexible, lighted stylet, which should transilluminate across the trachea if the tube is correctly positioned, may improve first-pass success.[4] However, digital intubation is unfamiliar to most clinicians and carries a significant risk of tube malposition and failure. A study evaluating the use of night vision goggles in tactical settings found that while this method enabled successful intubation, it required significantly more time.[5] In such cases, as a first-line option, it may be preferable to use alternative airway devices, such as supraglottic airways, that do not require direct visualization.

Atypical Patient Position

In the prehospital setting, patients are often found on the ground rather than on a waist-high surface that would be more ergonomic for responders. Additionally, patients are frequently not positioned in the optimal supine ramped position. Creating space around the patient, or, in extreme cases, using a snatch-and-grab strategy to move the patient to adjacent flat terrain for emergent airway management, is often desirable. However, this may not always be feasible due to entrapment or restricted access to the patient.

Various techniques can be used and may need to be tailored to specific circumstances. Basic techniques, such as the head-tilt-chin-lift, jaw-thrust, or the insertion of an oropharyngeal or nasopharyngeal airway, may be sufficient to improve the patient’s condition until better access is possible. Second-generation supraglottic airway devices have become more widely available over the last decade. These devices may provide a more secure airway and improved oxygenation in the obtunded patient, with the advantage of being inserted without requiring a direct line of sight to the patient's vocal cords. Insertion can be aided with small, judicious doses of sedative medication—a technique known as pharmacologically assisted laryngeal mask insertion (PALM).[6]

If tracheal intubation is deemed essential while the patient is on the ground, the responder can adopt various postures. When the patient is supine, the simplest approach is for the rescuer to lie prone, kneel, or sit at the patient's head. Alternatively, the responder can take a lateral decubitus position, which may be easier when lying on the left. This position allows greater freedom of movement for the responder’s right arm during tube insertion, whereas the left arm remains stabilized on the ground during laryngoscopy.[7][8]

For patients who may require intubation while in an upright position, such as those entrapped while sitting in a car, or where there is an absolute restriction of access at the patient’s head, it may be possible for the rescuer to adopt a face-to-face approach using inverse direct laryngoscopy. In this approach, the rescuer holds the laryngoscope upside down in the right hand, while the tracheal tube is held in the left. This technique may require the rescuer to straddle the patient.

Video laryngoscopy may facilitate this process, with one study showing significant differences in success when using different designs of video laryngoscopes.[9] However, given that most responders have limited experience with the unnatural ergonomics of face-to-face intubation, relying on other techniques to improve oxygenation and ventilation may be preferable until extrication or better patient access is possible for conventional laryngoscopy.

Obesity

Obesity is associated with a significantly increased risk of airway complications.[10] Increased soft tissue mass leads to increased body weight, and the volume of soft tissue can distort the airway in a patient with obesity when positioned supine, making visualization of vital structures more difficult. Additionally, the increased pressure on the diaphragm from the obese abdomen prevents normal diaphragmatic excursion. This effect is markedly exacerbated when the patient is supine, thereby leading to lower tidal volumes in spontaneously breathing patients, faster desaturation once sedated or paralyzed, and more difficult bag-valve-mask ventilation.

The increased pressure required to bag these patients can sometimes cause gastric inflation, which in turn exerts additional upward pressure on the diaphragm. This may create a dangerous downward spiral. Desaturation occurs more rapidly in patients with obesity due to compromised airway mechanics, increased metabolic demands and oxygen consumption, and underlying conditions that contribute to hypoxia. Patient positioning and preparation are crucial for effective airway management in bariatric patients. Manual airway manipulation, such as the jaw thrust or insertion of an oropharyngeal or nasopharyngeal airway, may help alleviate airway obstruction related to excess soft tissue. Practitioners should ensure proper alignment of the airway axis by positioning the patient so that the earlobe is aligned with the sternal notch in the horizontal plane.

Minimal Backup and Limited Equipment

The number of trained clinicians at a prehospital incident is typically lower than in a hospital setting, and skilled backup is often not immediately available. As advanced airway interventions are complex, the procedure is dependent on a well-trained team of skilled healthcare providers. If sufficient personnel are absent, the priority must be to maintain oxygenation and ventilation, even if this requires using only basic adjuncts and techniques.[11] In tactical or military settings, it may be necessary to implement basic interventions at the site of illness or injury, delaying definitive airway management until the patient can be moved to a safer location.

The use of standardized equipment sets and protocolized checklists can reduce error rates by minimizing unnecessary decision-making during an incident, thus freeing up cognitive "bandwidth."[12] The increasing availability and reduced cost of handheld telecommunications with internet connectivity have made telemedicine more feasible. Some studies have explored real-time video transmission during airway management, allowing senior clinicians at remote locations to assist with the decision-making process.[13]

Complications

The vast majority of patients do not have anatomically difficult airways. However, in emergency settings, particularly in the prehospital environment, even patients with structurally normal airways may present with "physiologically difficult" airways due to inadequate preoxygenation and serious intercurrent illness. Additionally, "situationally difficult" airways may arise due to factors such as limited skilled assistance, time pressures, poor patient positioning, or other adverse conditions.[14]

Complications of airway management can include aspiration, esophageal intubation, hypoxia, and physiological derangement.[10] Before performing advanced procedures such as intubation, EMS clinicians should proactively develop a clear plan for troubleshooting any potential complications that may arise. This may involve removing the device and replacing it with another or following a failed airway algorithm, which may include proceeding to front-of-neck access.

Clinical Significance

Airway management is not a benign procedure. Retrospective and observational studies have demonstrated that complications related to airway management occur more frequently when tracheal intubation is considered difficult.[15] In recent decades, evidence has become more equivocal regarding whether prehospital tracheal intubation significantly benefits many clinical conditions when weighed against the potential harm from airway complications.[16] Critical decision-making, which involves restricting advanced airway management when a patient’s condition or comorbidities are unfavorable, may be associated with lower rates of adverse outcomes.[17]

Enhancing Healthcare Team Outcomes

Several interprofessional healthcare teams, along with organizational and environmental factors, influence airway management. These factors have been identified in level 5 evidence from the human factors literature and include time and resource limitations, teamwork and communication, equipment location and storage, experience and learning, insufficient backup planning, and equipment preparation.[18]

Developing robust protocols, along with strong clinical governance and ongoing medical oversight, is essential for EMS organizations to consistently deliver safe and reliable airway management.[16] Focused team-based simulation training may have a role, particularly for adverse airway management scenarios that rarely occur in everyday practice.[19]