Airway Assessment

Anatomy and Physiology

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

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

A systematic pre-intubation airway assessment can be accomplished via several simple, quick methods.

Mouth opening can be assessed at the bedside using fingerbreadths. With the mouth open, the mandibular opening in adults should be at least 4 centimeters or 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. A small mandible increases the likelihood of tongue obstruction impairing visualization of anatomical structures during intubation. Similarly, a large mandible can elongate the oral axis 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 identify anatomy that may make intubation more challenging. A higher Mallampati score is associated with higher intubation failure rates due to poor visualization of the glottis.

Mallampati Classification

The Mallampati classification relates the size of the tongue to the visualization of the oral cavity. The more the tongue obstructs the view of the pharyngeal structures, the more difficult the airway might be.[4][5] 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

Neck Mobility

Mobility of the neck also plays a role in airway assessment. The ideal position for intubation is the "sniffing position." The sniffing position requires neck flexion to 35 degrees and head extension to 15 degrees. Neck immobility interferes with aligning the pharyngeal, oral, and laryngeal axes. 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, atlantooccipital extension may be assessed. If there is a concern about cervical spine injury, cervical alignment must be maintained during intubation, which may lead to difficult intubation.

Upper Lip Bite Test

Patients can be asked to protrude the lower jaw or bite their upper lip. The upper lip bite test assesses the ability to place the lower incisors over the 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 the lower teeth

Indications

Patients in respiratory distress or failure are at increased risk of requiring airway management. Therefore, airway assessment and evaluation for signs of respiratory distress or failure are essential. Patients with hypoventilation and hypoxia can present with altered mental status; patients may be anxious, confused, or obtunded. Patients in respiratory distress may have increased work of breathing characterized by dyspnea, tachypnea, hyperpnea or hypopnea, accessory muscle use, and cyanosis.

Contraindications

There are no true contraindications to airway assessment.

Equipment

Choosing the appropriate airway device is vital to effective airway management.

Facemask ventilation is a basic airway technique that provides oxygenation to the patient before placing an airway device. Noninvasive positive-pressure ventilation provides positive-pressure airway support without using an endotracheal tube. Patients can be placed on a continuous positive airway pressure (CPAP) device or a bilevel positive airway pressure (BIPAP) device. Patients ideal for noninvasive positive-pressure ventilation are cooperative, can protect their airway, and have intact ventilatory efforts. However, noninvasive positive-pressure ventilation should be used cautiously in hypovolemic hypotensive patients; the positive pressure may cause clinical decline. In addition, if the patient has agonal or absent respiratory effort, an impaired or absent gag reflex, altered mental status, severe maxillofacial trauma, a 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 inserted into the oropharynx and ventilate from above the glottis. The most common type of supraglottic device is the laryngeal mask airway (LMA). A supraglottic device may be considered in difficult mask ventilation or intubation cases, and a rescue device or conduit for intubation is needed.

Endotracheal tubes are devices inserted through the nose or mouth to provide oxygenation and ventilation. The distal end of the tube is located at the mid-trachea.

Technique or Treatment

Airway assessment is essential in medical practice, ensuring the safety of patients undergoing surgery, trauma care, or treatment in critical care settings. Several techniques and methods have been proposed and refined over the years, offering clinicians an array of tools for this vital task.[4]

One fundamental approach in airway assessment is the predictive physical examination. Predictors like the Mallampati score, thyromental distance, sternomental distance, and neck mobility have proven helpful in identifying potentially difficult airways.[6][7][8] However, these techniques have their limitations and are not infallible. They primarily rely on the experience and judgment of the clinician, and their predictive value varies widely.

The continued evolution of technology has ushered in a new era of airway assessment techniques. Ultrasound, for instance, has emerged as a promising tool for assessing the airway. It offers noninvasive, real-time imaging of the airway anatomy, which is particularly useful for predicting difficult intubations.[9] In addition, the adoption of video laryngoscopy has improved direct visualization of the airway, thus enhancing intubation success rates.[10]

Artificial intelligence (AI) and machine learning (ML) have found use in airway assessment. ML algorithms can integrate multiple patient variables, offering more accurate predictions than traditional assessment methods.[11] However, these advancements are still in their infancy, and more research is needed to fully establish their clinical applications and effectiveness. Awake transnasal flexible videoendoscopy has also been shown to improve preoperative airway risk stratification.[12]

Clinical Significance

Airway assessment tools can help predict the difficulty or ease of intubation. 

The multidimensional nature of airway assessment requires an individualized approach for each patient. Factors such as patient position, situational urgency, available resources, and skills and experience of the healthcare practitioner all contribute to selecting the most suitable assessment technique.[13] 

In conclusion, airway assessment requires clinical judgment, physical examination, and innovative technology. While traditional methods play a vital role, newer techniques such as ultrasound and video laryngoscopy, alongside AI-driven methods, may offer improved accuracy and efficiency. Embracing these advancements while acknowledging their current limitations will be vital to enhancing patient safety and outcomes in the future.

Enhancing Healthcare Team Outcomes

The first and most critical aspect in treating any illness is having a patent airway. All healthcare workers should know the basics of airway management; the patient is doomed without an airway. Most patients are evaluated by anesthesiologists and anesthesia nurses for their airway prior to any elective surgery. However, sometimes, patients are admitted through the emergency department or after surgery and run into airway problems. The best recommendation is to first consult with an anesthesiologist on airway management. If a healthcare worker has never intubated a patient, call the anesthesiologist first rather than jeopardize the patient's life.[14][15][16]

Skills

In today's healthcare environment, knowledge of airway assessment is essential. This also implies collaboration between interprofessional and multidisciplinary teams. The choice of airway management in patients should consider multiple factors, including the patient's preferences, the surgeon's input, and the expertise of the anesthesiologists to ensure safe airway management. Adhering to established guidelines and protocols is recommended to facilitate appropriate and effective airway management.

Strategy

It is most appropriate and ideal to maintain continuous closed-loop communication between all members of the perioperative care team regarding the need, technique, and potential management issues associated with airway assessment.

Ethics

Obtaining thorough and comprehensive informed consent from patients or their authorized decision makers is crucial before administering anesthesia and conducting an airway assessment. All team members should feel empowered to voice any concerns during the process, fostering buy-in from all stakeholders and facilitating early identification and resolution of any issues that may arise. This collaborative approach enhances patient safety and ensures a comprehensive review of the procedure.

Responsibilities

All team members have a duty to communicate their concerns, responsibilities, and activities with all other team members both contemporaneously and as indicated throughout the perioperative period based on their professional discretion.

Interprofessional Communication

All team members should respect the free flow of information and concerns among team members without allowing or producing an environment of hostility.

Care Coordination

All team members have a responsibility to avoid disrupting the work performed by other team members and to refrain from actions or inaction that may create additional issues or increase the workload for their colleagues. By maintaining a collaborative and supportive approach, team members can work together effectively, ensuring smooth workflow and minimizing any unnecessary burden on their fellow team members. This commitment to teamwork and mutual respect ultimately contributes to the delivery of high-quality patient care. [Level 1]