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, unanticipated difficulty during ventilation and intubation. Additionally, trauma patients are at increased risk of airway obstruction, aspiration, hypoxia and hypotension, and other unstable vital 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 and management of the airway. Some of the indications for managing the airway in patients include respiratory failure, altered sensorium(Glasgow 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 the airway by 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 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 cartilaginous structure attached to the facial skeleton and is divided into the two nasal cavities. The nose functions as a heater and humidifier of inspired air, it is also helps 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 the condition of the patient and difficulty 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 swallowing. The larynx extends from its entrance which is formed by the aryepiglottic folds, to the lower border of the cricoid cartilage till the tip of the epiglottis, and bulges posteriorly into the laryngopharynx.
• The trachea is formed by U-shaped cartilaginous rings in anterior and trachealis muscle in posterior, it extends from the lower edge of the cricoid cartilage to the carina where it divides into the mainstem bronchus. In order to place endotracheal tube in proper way, tip of the tube should be at mid tracheal 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 ventilation and oxygenation.

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 airway management 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 difficult airway. 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 patient's survival and depends on first responders skills and quick assessment and decision. These crucial steps requires techniques which are used universally in order to manage patient's airway. Following are initial evaluation 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 in 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 and anesthetic induction provides patients with improved oxygenation and increases the time to hypoxemia.
• Bag-mask ventilation is a basic essential technique when endotracheal tube intubation is difficult, it assists for rapid ventilation and oxygenation in patients.
• Bag-mask ventilation can be achieved by a single practitioner alone or side by side with a second care provider in an emergency room or an operating room
• Bag mask ventilation can also be utilized as a pressure support during spontaneous respiration in patients with decreased tidal volumes and insufficient ventilation, very similar to the use of CPAP or BiPAP to assist patients who are spontaneously breathing but are not adequately ventilating or oxygenating.

• 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 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 advantages include:

• They act as a niche between bag and mask ventilation and endotracheal intubation.
• 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.

• Endotracheal intubation: It is the gold standard for definitive airway management in the prehospital setting, and also hospital 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 is named after the Indian-born American anesthesiologist 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 the airway and predicting the difficult intubation.
• 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.

• Cormack-Lehane grading on Direct laryngoscopy: This grading is used to predict the difficulty in intubation based on the structures visualised on laryngoscopy. The grade 2 was subdivided into 2a and 2b in the modified Cormack-Lehane classification.
• Modified Cormack-Lehane classification:
  • Class 1:Full view of glottis is visible.
  • Class 2a:Partial view of glottis is visible.
  • Class 2b:Only posterior extremity of glottis or only arytenoid cartilages are seen.
  • Class 3:Only epiglottis ,but not glottis is seen.
  • Class 4:Neither of the glottis or epiglottis are seen.

• Rapid sequence intubation:

• Rapid sequence intubation (RSI) is a technique used for endotracheal intubation when the patient is at high risk of aspiration. For RSI to be performed, it requires two persons, first patient's lungs are preoxygenated with bag and mask . One person applies constant pressure on the cricoid cartilage, occluding the esophagus. Sedative-hypnotic or an induction agent and a muscle relaxant is administered and patient's trachea is intubated, and cricoid pressure is released after the cuff is inflated. Traditionally, thiopentone sodium and succinylcholine were used for RSI, and it had an advantage that patient's airway will be relaxed and paralysed, facilitating the [[intubation] and if any unanticipated difficulty occurs, these drugs were short acting and the effect weans off quickly. 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.

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 the Airway in Patients with Trauma

• Airway management includes maintaining a patent airway by bag and mask ventilation, using oroapharyngeal ornasopharyngealairways, endotracheal intubation and also management of the airway during extubation and after extubation.

Difficult airway

• Difficult airway includes problems encountered during bag and mask ventilation, like holding of face mask applying positive pressure ventilation, problems with laryngoscopy and intubation.

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 process 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.
• 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.

Approach to airway management of a patient with Maxillo-Facial Injury

Airway management of patients with maxillofacial trauma is challenging and vital because it's directly affecting the patient's survival. Endotracheal intubation is the gold standard procedure to secure the airway in trauma patients, however, in these patients passage of endotracheal tube may not be possible because the oral cavity, pharynx, and larynx may be filled with blood, secretions, soft tissue, and bone fragments. Another reason for this is that the risk of aspiration and regurgitation is high in these patients.

• In such circumstances, there are numerous airway devices are available to rescue patients with maxillofacial injuries, some of these devices include:
  • Flexible fiberoptic bronchoscopy (FOB), enable an indirect view of vocal cords.
  • Laryngeal mask airway (LMA) may be inserted blindly since it does not require a view of the vocal cords. Another option for securing the airway in these patients is to pass the endotracheal tube after placing an LMA for them.
• Final option for establishing the airway in patients with maxillofacial injury is surgery by cricothyroidotomy.
  • Cricothyroidotomy also known as cricothyrotomy is a procedure done by trained health care providers, they make a small incision through the skin and cricoid membrane which lies between the thyroid and cricoid cartilages, followed by inserting a tracheostomy tube to open alternative way of ventilation and oxygenation in the emergency situation which uses of endotracheal intubation is almost impossible or difficult and time-consuming.
  • Indication for cricothyroidotomy include:
    • Inability to secure airway through an endotracheal tube
    • Major trauma to facial muscles, pharynx, larynx.
    • Congenital deformities and upper airway stenosis.

• Contraindications for cricothyroidotomy:
  • Age, in pediatrics younger than 12 years old needle cricothyrotomy is indicated because of less potential damage to the larynx and surrounding structures.
  • Massive trauma to the larynx or cricoid cartilage
  • Inability to identify surface landmarks due to obesity, cervical trauma.
  • When orotracheal and nasotracheal intubation are viable options
  • Airway obstruction distal to subglottic airway, e.g. tracheal stenosis
  • Laryngeal cancer: Other than for an extreme airway emergency, cricothyroidotomy must be avoided to not to seed the soft tissue of the neck with cancer cells
  • Coagulopathy (other than emergency situation)

• Complications of cricothyroidotomy:
  • Esophageal perforation if the blade penetrates too deeply.
  • Subcutaneous emphysema
  • Rupture of vital vessels such as a carotid artery, excessive bleeding, and hemorrhage.

• Indications of definitive airway management in patients with maxillofacial injury:
  • Absent spontaneous breathing
  • Comatose patients(Glasgow coma score < 9)
  • Airway injury or obstruction
  • Persistent oxygen saturation below 90%
  • High risk for aspiration
  • Systemic shock(Systolic Blood Pressure<80mmHg)
  • "Cannot intubate, cannot ventilate" situations

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 anesthetic deaths
• Failure in airway management techniques

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Related Chapters

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

References

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