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. Airway management complications are common, especially in trauma patients because of associated pathology, lack of complete evaluation before intubation. Additionally, trauma patients are at increased risk of airway obstruction, aspiration, hypoxia and hypotension, and vital sign instability. The providers must have skillset related to working with a variety of tools and techniques used in airway management and knowledge of the important anatomical, physiological, and pathological features related to the airway. They also should know the differences between the adult versus pediatric and neonatal airways as these anatomical and physiological differences are critical, impactful on patients lives and knowing these leads to effective control of the airway. Some of the indications for managing the airway in patients include respiratory failure, a reduced level of consciousness (Glasco Coma Scale less than or equal to 8), rapid deterioration of mental status, airway injury or compromise, injuries causing a high risk for aspiration, which includes all penetrating injuries to the abdomen or chest wall. Inadequate airway management may lead to cardiovascular arrest and compromise life-saving interventions in a trauma patient. Several airway control devices and techniques are available to assist healthcare 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

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

For a successful approach 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 equipment and methods that can be utilized for this purpose. Also, the difference between 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, it is also helping in phonation and vocal resonation and houses the olfactory receptors. The paranasal sinuses drain into the nasal cavities.
• An endotracheal tube passes through the nose or mouth into the trachea to protect the airway and achieve positive-pressure ventilation. The mouth opens posteriorly into the oropharynx and becomes part of the gastrointestinal system, helps the digestion and also plays a role 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 maintain ventilation; but depending upon position of patient who is arriving and difficulty that is due to anatomical shape of upper airway, this route may not be doable, for instance in supine unconscious persons, the backward movement of the tongue and lower jaw may cause airway obstruction and performing orotracheal intubation may not be the optimal way of managing airway.
• The pharynx is a membrane-lined cavity behind the mouth and nose, extends from the base of the skull to the cricoid cartilage at the level of sixth cervical vertebrae which is an 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 is involved with the act of swallowing.
• The larynx consists of cartilages and fibro-elastic membranes covered by a sheet of muscles and mucous membrane. It functions as an open valve in respiration, helps in phonation, and protects 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

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. A 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. Spontaneous ventilation can be assisted through the placement of a nasal or oral airway. Oxygenation can be improved by giving oxygen via nasal cannula, simple face mask, or nonrebreather face mask. Unfortunately, the maximally achieved FiO2 is often overestimated 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 a useful management technique, however, because of the risk of infection transmission it is recommended by American heart association that health care providers do "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 the time to hypoxemia.
• BMV is basic essential technique when endotracheal tube intubation is difficult, it assists for rapid oxygenation and ventilation in patients.
• BMV can be applied by a sole practitioner or in conjunction with a second care provider in an operating room.
• BMV can also be done 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.
• It can offer better ventilation during transport than bag-mask ventilation alone.
  • Supraglottic airway devices can be used as an alternative tool in cases of failed intubation.

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)

• Endotracheal intubation: It is the gold standard for definitive airway management in the prehospital setting, 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 assess the distance from the tongue base to the roof of the mouth visually. It is an indirect way of assessing how difficult intubation will be.
• Modified Mallampati Scoring:
  • Class I: Soft palate, uvula, fauces, pillars visible.
  • Class II: Soft palate, a major part of the uvula, fauces visible.
  • Class III: Soft palate, the base of uvula visible.
  • Class IV: Only hard palate visible.

• Rapid sequence intubation versus no-medication intubation:

• Use of pharmacological muscle relaxant eases the intubation process by relaxing muscles in the pharynx. Rapid sequence intubation (RSI) techniques incorporate pharmacologic muscle relaxation and are utilized by anesthesiologists and emergency medicine physicians. However, the disadvantage of these techniques is the elimination of a patient's ability to breathe spontaneously if the intubation fails. There is a debate that optimal intubating conditions should be achieved first before trying to attempt intubation in the prehospital setting. Time is an important factor and critical in prehospital airway management of patients, due to trauma, cardiac arrest, hypoxemia, or aspiration risk. Administration of the neuromuscular blocking agent is associated with a reduction in time from rapid sequence intubation administration to the end of intubation attempt.

Management of the Airway in Patients with Specific Injury

Suspected Spinal Cord Injury

• In patients with suspected trauma, extreme caution must be taken in aligning the head and neck. The cervical spine must be maintained in a neutral mid-line position, the exception to this is physical resistance.
• Neck Maneuvers During Airway Management:
  • Immobilizing patient's neck by using sandbag-collar-tape on hardboard in a pre-hospital care setting.
  • Applying pressure on cricoid with anterior half of hard cervical collar removed and another hand behind the posterior cervical collar.
  • Manual in-line stabilization is the technique of choice in any suspected cervical spine injury, during endotracheal intubation. In this technique, 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, even after manual in-line stabilization.

• Jaw thrust is the only basic airway opening maneuver appropriate for any patient with a suspected cervical spine injury. This method is used when head-tilt/chin-lift can be potentially dangerous to use on a patient who may have a cervical spine injury. In jaw-thrust maneuver, first care provider lifts the hyoid bone and tongue away from the posterior pharyngeal wall by pulling the mandible forward, displacing the tongue anteriorly.
• 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.
• In order to minimize the risk of hypoxic damage from airway obstruction in an unconscious patient, proper positioning is done by placing patients in the lateral side with log rolling technique.

Complications of airway management

Airway management complications are common, these complications usually occur in intensive care units and emergency departments, summary of airway management related complactions include:

• Patient harm/death associated with suboptimal care
• Hypoxia is the most common cause of airway-related deaths
• Obesity
• Pulmonary aspiration remains the leading cause of airway-related anaesthetic deaths
• Failure in airway management techniques

Related Chapters

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

References

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