Airway, Assessment

Article Author:
MIchelle Mouri
Article Editor:
Richard Whitten
Updated:
2/23/2018 8:36:33 AM
PubMed Link:
Airway, Assessment

Introduction

Airway assessment in a patient requiring airway management should be done quickly and efficiently. Indications for initiating airway support include failure to oxygenate, ventilate, and maintain airway patency. The first step in successful airway management is assessing the airway. The two categories for airway management include noninvasive and invasive. Noninvasive airway management includes passive oxygenation, bag-valve-mask ventilation, supraglottic airways, and noninvasive positive-pressure ventilation. Invasive airways include endotracheal intubation, cricothyroidotomy, and tracheostomy.

A patient in need of airway management needs to be assessed for a difficult airway. A difficult airway is one where the patient will be hard to mask ventilate, or intubation is likely to fail. A failed airway is defined as three unsuccessful attempts at intubation by an experienced practitioner.

An airway history from the patient will aid in determining if there has been a previous airway problem. Many disease states have been associated with a difficult airway. Pulmonary problems such as asthma, pneumonia, and chronic obstructive pulmonary disease may affect oxygenation and ventilation.

Anatomy

Assessing potential difficulties for bag-valve-mask ventilation and laryngoscopy should be completed before any attempt at intubation.

Factors that increase the risk of a difficult bag-valve-mask ventilation include facial hair, obesity, being edentulous, advanced age, and history of snoring. These features can be identified with a first glance assessment by the practitioner. Dentition should also be assessed, and dentures should be removed for intubation. However, dentures may need to be left in place for noninvasive airway management.

There a few simple and quick methods the practitioner can use to systematically evaluate the airway before intubation.

Mouth opening can be assessed by using fingerbreadths. The patient can be asked to open his or her mouth quickly at the bedside. The mandibular opening should be at least 4 centimeters in adults, which is approximately three to four fingerbreadths. The distance between the mentum and the hyoid bone can also be measured and should be three to four fingerbreadths. If the patient has a small mandible, they are more likely to have a tongue obstruction which can impair the view when intubating. A large mandible can also attribute to a difficult airway by elongating the oral axis and impairing visualization of the vocal cords.

The patient can also be asked to open their mouth while sitting upright to assess the extent to which the tongue prevents the visualization of the posterior pharynx. The Mallampati classification system helps the practitioner identify anatomy that may make intubation more challenging. A higher Mallampati score is associated with higher intubation failure rates as a result of poor visualization of the glottis.

Mallampati Classification

The Mallampati classification involves the size of the tongue in relation to the oral cavity. The more the tongue obstructs the view of the pharyngeal structure, the more difficult the airway might be. The classification includes four views:

  • Class I: the entire palatal arch, including the bilateral faucial pillars, are visible down to their base
  • Class II: the upper part of the faucial pillars and most of the uvula are visible
  • Class III: only the hard and soft palates are visible
  • Class IV: only the hard palate is visible

The patient's neck mobility plays a role in airway assessment as well. The ideal position for intubation is the "sniffing position." The sniffing position requires flexion of the neck to 35 degrees and head extension to 15 degrees. Neck immobility interferes with the ability to align the pharyngeal axis, oral axis, and laryngeal axis. Neck mobility can be impeded by a cervical collar or structural changes including a fracture, dislocation, or arthritis. If there is no concern for a cervical spine injury, the atlanto-occipital extension may be assessed. If there is a concern about cervical spine injury, cervical alignment must be maintained during intubation, which may lead to a difficult intubation.

Patients can be asked to protrude the lower jaw or bite their upper lip. The upper lip bite test assesses the patient's ability to place their lower incisors over their upper lip. This acts as a predictor of the ability to subluxate the mandible during laryngoscopy. The grading system is as follows:

  • Grade 1: the patient can fully cover the upper lip with the lower incisors
  • Grade 2: the patient can partially cover the upper lip with the lower incisors
  • Grade 3: the patient cannot reach the upper lip with lower teeth

Indications

Evaluating the patient for signs of respiratory failure is essential. Patients with hypoventilation and hypoxia can present with altered mental status. These patients may be anxious, confused, or obtunded. Patients with respiratory distress may have increased work of breathing. Signs of increased work of breathing include dyspnea, tachypnea, hyperpnea or hypopnea, accessory muscle use, and cyanosis.

If a patient is in respiratory distress, they need to be evaluated for a challenging airway.

Equipment

Choosing the appropriate airway device is important in patient airway management. Facemask ventilation is a basic airway technique that provides oxygenation to the patient prior to placement of an airway device. Noninvasive positive-pressure ventilation provides positive pressure airway support without the use of an endotracheal tube. Patients can be placed on a continuous positive airway pressure (CPAP) device or a bilevel positive airway pressure (BIPAP) device. The patient who is ideal for noninvasive positive-pressure ventilation is cooperative and can protect their airway with intact ventilatory efforts. Use with caution in hypotensive patients due to volume depletion, as it can be worsened due to the positive pressure.

If the patient has agonal or absent respiratory effort, impaired or absent gag reflex, altered mental status, severe maxillofacial trauma, basilar skull fracture, life-threatening epistaxis, or bullous lung disease, CPAP or BIPAP is not appropriate, and the patient should be endotracheally intubated.

Supraglottic airways are devices that are inserted into the oropharynx and ventilate the patient above the glottis. The most common type of supraglottic device is the laryngeal mask airway (LMA). A supraglottic device may be considered in a patient whom intubation and mask ventilation is difficult, and it is needed as a rescue device or as a conduit for intubation.

Endotracheal tubes are devices inserted through the nose or mouth to provide oxygenation and ventilation. The distal end sits mid-trachea.

Clinical Significance

Assessment tools can help predict the difficulty or ease of intubation.