Airway management

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Nima Nasiri, M.D.[2]

Overview

Airway management is the process of ensuring that there is an open pathway between a patient’s lungs and the outside world, and the lungs are safe from aspiration. Airway loss is a major cause of preventable prehospital death in trauma patients. Trauma airway management is complicated because of associated pathology and suboptimal intubating conditions, and also because complete preintubation evaluation and planning is rarely possible. Furthermore, trauma patients are at increased risk for hypoxia, airway obstruction, hypoventilation, hypotension, and aspiration. To be skillful at the airway management, the provider must have knowledge of the important anatomical, physiological, and pathological features related to the airway as well as knowledge of the various tools and methods that have been developed for this purpose. They also should know the differences between the adult, pediatric and neonatal airways and well versed with other difficult airways as these differences could impact on the safe and effective control of the airway. Indications for intervening to secure the airway include respiratory failure (hypoxic or hypercapnic), apnea, a reduced level of consciousness (sometimes stated as Glasco Coma Scale less than or equal to 8), rapid change of mental status, airway injury or impending airway compromise, high risk for aspiration, or 'trauma to the box', which includes all penetrating injuries to the abdomen or chest cavity. Inadequate airway management may lead to a cardiovascular arrest and complicate subsequent life-saving interventions in the injured pa-tient[1]. Several airway control devices and techniques are available to assist prehospital providers in order to maintain ventilation and oxygenation. These include bag valve mask (BVM) ventilation, direct laryngoscopy with endotracheal intubation (ETI) and adjunct supraglottic airway devices such as the laryngeal mask airway.

Functional anatomy of the upper airway

For successful aproach to airway management, health care providers must have knowledge of important anatomical, physiological, and pathological features related to the airway as well as knowledge of the various equipments and methods that can be utilized for this purpose. Also the difference of airway management in adults, pediatrics and neonates is very critical.

• The upper airway is consists of the pharynx and nasal cavities, the larynx and trachea may be included, and the oral cavity provides an alternate air entry into the respiratory system.
• The nose is a bony and cartilage structure attached to the facial skeleton, and is divided into the two nasal cavities. The nose functions as a heater and humidifier of inspired gas, a voice resonator, and houses the olfactory receptors. The paranasal sinuses drain into the nasal cavities.
• An endotracheal tube may be passed through the nose into the trachea when necessary to protect the airway and achieve positive-pressure ventilation. The mouth opens posteriorly into the oropharynx and forms the entrance to the digestive tract as well as an alternate pathway for respiration. It is also involved in phonation.
• Orotracheal intubation can be used as an alternative to nasal intubation to achieve airway protection and ventilation when necessary; however, variations in upper airway anatomy may make this technique difficult. In supine unconscious persons, backward movement of the tongue and lower jaw may cause airway obstruction.
• The pharynx is a U-shaped fibromuscular tube extending from the base of the skull to the cricoid cartilage at the entrance to the esophagus. Anteriorly it opens into the nasal cavity, the mouth, and the larynx, which divide it into the naso-, oro-, and laryngopharynx, respectively. The pharynx thus forms a common aerodigestive tract and is intimately involved with the act of swallowing.
• The larynx consists of a framework of cartilages and fibroelastic membranes covered by a sheet of muscles and lined with mucous membrane. It evolved as a protective valve mechanism at the upper end of the lower airway necessitated by an unusual crossover between the airway and alimentary canal. It functions as an open valve in respiration, a partially closed valve in phonation, and as a closed valve protecting against aspiration during swallowing. The larynx extends from its oblique entrance formed by the aryepiglottic folds, the tip of the epiglottis, and the posterior commissure to the lower border of the cricoid cartilage and bulges posteriorly into the laryngopharynx.
• The trachea extends from the lower edge of the cricoid cartilage to the carina where it divides into the mainstem bronchi. It is formed by U-shaped cartilaginous rings anteriorly and is closed posteriorly by the trachealis muscle. A properly placed endotracheal tube should have its tip at about midtracheal level

upper airway systemstaff (2014). "Medical gallery of Blausen Medical 2014". WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436.

Recommendations for evaluation of airway

The basic approach in airway management in the emergency setting includes:

• Protection from aspiration and pneumonia related to that.
• Providing adequate oxygenation and ventilation.

Following are steps that must be considered prior to conducting airway management, these include:

• History: An airway history should be conducted whenever it is possible, before airway management in all patients to detect medical, surgical, and anesthetic factors that may indicate the presence of a difficult airway. Detailed review of previous anesthetic records, if available, may provide useful information about airway management.

• Physical Examination: An airway physical examination should be conducted before the initiation of airway management. The goal of physical examination is to detect physical characteristics that may indicate the presence of a difficult airway because an unsuccessful upper airway mangaement is associated with increase in mortality and morbidity.

• Additional Evaluation. Additional evaluation may be indicated in some patients to characterize the likelihood or nature of the anticipated airway difficulty. Certain diagnostic tests (e.g., radiography, computed tomography scans, fluoroscopy) can identify a variety of acquired or congenital features in patients with difficult airways

Techniques for airway management

• The decision about whether an airway intervention is required or not is crucial for patients survival and depends on first responders skills and qucik assessment and decision. These crucial steps requires techniques which is used universally in order to manage patient's airway, followings are initial evaluation and methods which had been developed to assist patient's ventilation and keep the airway patent, these techniques include:
• Spontaneous breathing: When a provider is confronted with an awake patient having a patent airway. Assistance for spontaneous ventilation can be performed through the placement of a nasal or oral airway. Oxygenation can be improved with the supplementation of oxygen via nasal cannula, simple face mask, or nonrebreather face mask. Unfortunately, the maximally achieved FiO2 is often over estimated by care providers and hypoventilation resulting in hypercapnia cannot be normalized with increase oxygen supply.

• Mouth-to-Mouth ventilation: Mouth-to-mouth or mouth-to-nose ventilation is still a recognized management technique for prehospital airway management. However, this modality has fallen out of favor recently with the increasing support of “hands-only” CPR. Proper face masks should be utilized if they are available.

• Bag-mask ventilation: It is a standard initial approach to airway management in the prehospital and hospital settings.
• Proper preoxygenation prior to intubation provides patients with improved oxygenation and increases time to hypoxemia.
• BMV can be applied as a sole practitioner or in conjunction with a second care provider.
• BMV can also occur during spontaneous respirations as a pressure support method for patients with depressed tidal volumes and inadequate ventilation.
• This is similar to the use of CPAP or BiPAP to assist patients who are spontaneously breathing but are not adequately oxygenating or ventilating.

• Oropharyngeal and nasopharyngeal airways:
• This is used as an adjunct device for spontaneous or assisted ventilation.
• Oropharyngeal and nasopharyngeal airways are frequently utilized by prehospital care providers to improve oxygenation and ventilation.
• These devices are frequently used to temporize until a more definitive airway is obtained, and there are several circumstances that prohibit their placement (severe head or facial injuries).

• Supraglottic airway devices: Supraglottic airway (SGA) device placement is very useful to keep the airways open, it has advantages in comparison with Endotracheal tube intubation, or other methods these are include:
  • Requires less training than ETI.
  • It is less invasive than ETI.
  • For care providers not sufficiently trained in ETI these devices can offer better ventilation during transport than BMV alone.
  • SGAs can be used as a backup tool for failed intubation in accordance with the difficult airway algorithm by the American Society of Anesthesiology (ASA).

• Endotracheal intubation: It is the gold standard for definitive airway management in the prehospital setting. ETI advantages are include:
  • It allows for positive pressure ventilation, positive end-expiratory pressure (PEEP), positive pressure recruitment maneuvers, and protection from aspiration.
    • Mallampati Classification for Assessment of Upper Airway Anatomical Balance: It's named after the Indian-born American anaesthesiologist Seshagiri Mallampati, is used to predict the ease of endotracheal intubation. The test comprises a visual assessment of the distance from the tongue base to the roof of the mouth, and therefore the amount of space in which there is to work. It is an indirect way of assessing how difficult an intubation will be.
    • Modified Mallampati Scoring:
    • Class I: Soft palate, uvula, fauces, pillars visible.
    • Class II: Soft palate, major part of uvula, fauces visible.
    • Class III: Soft palate, base of uvula visible.
    • Class IV: Only hard palate visible.

• Rapid sequence intubation versus no-medication intubation

Pharmacologic muscle paralysis relaxes the pharyngeal and facial musculature and results in improved intubation conditions. Rapid sequence intubation (RSI) techniques incorporate pharmacologic muscle relaxation and are utilized by anesthesiologists and emergency medicine physicians. However, one drawback to these techniques is the elimination of a patient's ability to breathe spontaneously if the intubation fails. Yet many providers conversely argue that optimal intubating conditions should be achieved prior to attempted intubation in the prehospital setting. The reason for this is that prehospital airway intervention is frequently time sensitive due to trauma, cardiac arrest, hypoxemia, or aspiration risk.

Photograph of an anesthesiologist using the Glidescope video laryngoscope to intubate the trachea of a morbidly obese elderly person with challenging airway anatomy(DiverDave (talk)) created this work entirely by myself. (Original uploaded on en.wikipedia)

Management of airway in patients with suspected spinal cord injury

• In patients with suspected trauma, extreme caution must be taken in aligning the head and neck.In these circumstances the cervical spine must be maintained in a neutral mid-line position unless it is physically difficult to do so or resistance is encountered during any attempt at realignment.
• Manual in-line stabilization is the technique of choice in any trauma patient, with the head grasped firmly at the mastoid processes and the occiput.
• Traction should be avoided as it may distract the cervical spine and cause more neurological damage.
• Jaw thrust is the only basic airway opening manoeuvre appropriate for any patient with suspected cervical spine injury.
• Suction and use of forceps under direct vision using a laryngoscope with the head and neck maintained in the neutral position are the best methods of removing foreign material from the mouth and pharynx but back blows and abdominal or chest thrusts are acceptable only in extreme conditions.
• The risk of hypoxic damage from airway obstruction in an unconscious breathing victim is likely to outweigh the risk of cervical spine injury in the vast majority of cases and such patients should be placed in the lateral position using a log rolling technique with a minimum of four attendants.
• The rescuer controlling the head and neck with manual in-line stabilization should be in command of the rotation procedure. When turned, the lower limb should not be flexed unless a thoracolumbar injury is not suspected. Movement of the arms is not recommended.

Manual Methods

Head Tilt/ Chin Lift

The simplest way of ensuring an open airway in an unconscious patient is to use a head tilt chin lift technique, thereby lifting the tongue from the back of the throat. This is taught on most first aid courses as the standard way of clearing an airway.

Jaw Thrust

• The jaw thrust is a technique used on patients with a suspected spinal injury and is used on a supine patient.
• The practitioner uses their thumbs to physically push the posterior (back) aspects of the mandible upwards - only possible on a patient with a GCS < 8 (although patients with a GCS higher than this should also be maintaining their own patent airway).
• When the mandible is displaced forward, it pulls the tongue forward and prevents it from occluding (blocking) the entrance to the trachea, helping to ensure a patent (secure) airway.

ILCOR no longer advocates use of the jaw thrust by lay rescuers, even for spinal injured victims, although health care professionals still maintain the technique for specific applications. Instead, lay rescuers are advised to use the same head-tilt for all victims.

Removal of Vomit and Regurgitation

• In the case of a patient who vomits or has other secretions in the airway, these techniques will not be enough.
• Suitably trained clinicians may elect to use suction to clean out the airway, although this may not always be possible.
• An unconscious patient who is regurgitating stomach contents should be turned into the recovery position when there is no suction equipment available, as this allows (to a certain extent) the drainage of fluids out of the mouth instead of down the trachea.

Related Chapters

• Intubation
• Endotracheal Tube
• Laryngeal Mask Airway
• Oropharyngeal Airway
• Nasopharyngeal Airway
• Ventilation
• Cricothyrotomy
• Tracheotomy

References

Emergency Medical Responder (Second Canadian Version). Brady. 2006. pp. 92–97. ISBN 0-13-127824-X.