Preoperative airway assessment is the systematic anatomical and physiological examination of a patient’s airway before any anesthetic procedure. Its primary goal is to identify potential intubation difficulties in advance, prevent complications, and formulate a safe anesthesia plan. In anesthetic practice, an “unanticipated difficult airway” is considered one of the most dangerous scenarios; preoperative assessment is the principal tool for eliminating that element of surprise.

Why Is It So Important?

Evidence shows that a significant proportion of anesthesia-related deaths and serious complications are associated with failed airway management. An unanticipated difficult airway can lead to life-threatening emergencies such as “can’t intubate, can’t oxygenate” (CICO). Preoperative assessment must therefore be regarded not merely as a technical protocol, but as the cornerstone of patient safety.

Components of the Assessment

1. History Taking

Previous anesthetic experiences: If the patient has previously undergone anesthesia, it is essential to establish whether any difficulty was encountered with airway management at that time. A documented history of difficult intubation is critically important information.

Family history: Certain anatomical features are hereditary; a family history of difficult intubation may signal increased risk.

Current complaints: Symptoms such as snoring, sleep apnea, dysphagia, hoarseness, restricted neck movement, or jaw pain may indicate underlying airway problems.

Systemic diseases: Rheumatoid arthritis (with cervical involvement), ankylosing spondylitis, acromegaly, obesity, diabetes (limited joint mobility syndrome), thyroid disorders, and head and neck cancers are among the leading conditions that increase the risk of a difficult airway.

Previous head and neck surgery or radiotherapy: These can cause soft tissue fibrosis and restricted movement, making intubation more challenging.

2. Physical Examination

This constitutes the most critical component of preoperative airway assessment. Multiple anatomical parameters are evaluated in combination.

Mallampati Classification

The patient is asked to open the mouth fully and protrude the tongue. Structures are then classified based on what is visible.

• Class I: Soft palate, uvula, fauces, and tonsils are fully visible. No intubation difficulty is anticipated.
• Class II: Soft palate, uvula, and fauces are visible; tonsils are not.
• Class III: Only the soft palate and base of the uvula are visible.
• Class IV: Only the hard palate is visible. The risk of difficult intubation is high.

Mouth Opening (Interincisal Distance)

The distance between the upper and lower incisor teeth. A value of ≥ 3 cm (approximately three finger-breadths) is considered normal. Below 3 cm, laryngoscopy becomes significantly more challenging.

Thyromental Distance

The distance from the tip of the chin to the upper border of the thyroid cartilage with the head in full extension. A normal value is ≥ 6–6.5 cm. A short thyromental distance indicates that visualization of the anterior laryngeal structures during laryngoscopy will be difficult.

Sternomental Distance

The distance from the tip of the chin to the sternal notch with the head in full extension. A normal value is ≥ 12.5 cm. This measurement is particularly valuable in patients with restricted neck mobility.

Neck Mobility

Assessment of head flexion and extension. Normal extension is approximately 80°. Rheumatoid arthritis, ankylosing spondylitis, and prior cervical surgery can restrict neck mobility and adversely affect the laryngoscopy angle.

Upper Lip Bite Test (ULBT)

The patient is asked to bite the upper lip with the lower incisors.

• Class I: Lower teeth cover the upper lip mucosa — favorable prognosis.
• Class II: Lower teeth reach the upper lip but cannot cover the mucosa.
• Class III: Lower teeth cannot reach the upper lip — high risk of difficult intubation.

Neck Circumference and Obesity

In patients with a neck circumference ≥ 40 cm, the risk of a difficult airway increases markedly. Obese patients also have reduced oxygen reserves and a lower tolerance for apneic periods.

Mandibular Anatomy and Micrognathia

A small or receding jaw (micrognathia or retrognathia) makes it difficult to displace the tongue anteriorly during laryngoscopy, reducing glottic visibility.

Dental Status

Loose, broken, or protruding teeth pose a risk during laryngoscopy. If the patient has dentures, it must be planned whether these should be removed prior to the procedure.

3. Predictive Scoring Systems

When a single parameter is insufficient, combined scoring systems are employed.

The LEMON Score

A practical assessment tool developed to predict a difficult airway.

• L — Look externally: Visual cues such as facial trauma, short neck, large tongue, or beard.
• E — Evaluate the 3-3-2 rule: Mouth opening ≥ 3 finger-breadths, hyoid-to-chin distance ≥ 3 finger-breadths, thyroid-to-mouth floor distance ≥ 2 finger-breadths.
• M — Mallampati: Class III or IV signals increased risk.
• O — Obstruction: Airway obstruction due to a mass, abscess, or foreign body.
• N — Neck mobility: Restricted neck movement.

The Wilson Risk Score

Evaluates five parameters: weight, head and neck movement, jaw movement, retrognathia, and protruding teeth. A total score of ≥ 2 is considered indicative of high risk for difficult intubation.

4. Advanced Investigations

When standard physical examination is insufficient, additional investigations may be required.

Direct or indirect laryngoscopy: In the presence of hoarseness, dysphagia, or a suspected airway mass, preoperative laryngoscopy can be performed to assess vocal cord mobility and airway anatomy.

Cervical radiography and CT: In patients with neck masses, tracheal deviation, or cervical pathology, imaging clarifies the relevant structures.

Sleep apnea evaluation: The STOP-BANG questionnaire is used to screen for obstructive sleep apnea. In high-risk patients, airway safety planning must extend into the postoperative period as well.

5. Aspiration Risk Assessment

This forms an inseparable component of airway assessment.

Conditions carrying high aspiration risk: Recent food intake within the past 6–8 hours (full stomach), gastroesophageal reflux disease, pregnancy (particularly from the second trimester onward), obesity, diabetic gastroparesis, bowel obstruction, and emergency surgical situations.

In these patients, RSI and a rapid airway security plan must be formulated.

6. Preoperative Planning and Documentation

The purpose of the entire assessment is to produce a concrete anesthesia plan. This plan should address the following questions.

Will standard induction be applied, or is a modified approach required? If a difficult airway is anticipated, will awake fiberoptic intubation be planned? What backup plans (Plan A, Plan B, Plan C) will be prepared? Is the difficult airway trolley with all necessary equipment ready? Will assistance from a second anesthesiologist or an ENT surgeon be required?

All of this information must be documented in the anesthesia note and shared with the operating room team. A “difficult airway” entry is also extremely valuable for future encounters and should be recorded in all of the patient’s medical records.

The Difficult Airway Algorithm

When preoperative assessment reveals a high likelihood of difficult intubation, the anesthesiologist must have a structured plan in place before induction even begins. Guidelines from the American Society of Anesthesiologists (ASA) and the Difficult Airway Society (DAS) outline stepwise algorithms covering awake intubation strategies, video laryngoscopy, supraglottic rescue devices, and emergency surgical airway access. Preoperative assessment is what determines which branch of this algorithm will be followed — making it not an afterthought, but the very foundation of safe anesthetic care.

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This content is intended for informational purposes only. Please consult the relevant specialist for all clinical decisions.