Fibreoptic Endoscopic Evaluation of Swallowing (FEES): Clinical Indications and Procedure

Fibreoptic endoscopic evaluation of swallowing (FEES) is one of the two gold-standard instrumental assessments for dysphagia, alongside videofluoroscopic swallowing study (VFSS). FEES allows direct visualisation of the hypopharynx, larynx, and vocal folds during swallowing using a thin, flexible nasendoscope passed through the nose. It provides information that no bedside evaluation can match, and is increasingly available in a wide range of clinical settings — including, in Hong Kong, community elderly care centres and hospital wards.

This article follows ASHA Practice Portal guidance on adult dysphagia and NICE CG162.

What FEES Can and Cannot See

What FEES Shows

FEES provides a superior-view endoscopic image of:

• Laryngeal anatomy: true and false vocal folds, arytenoids, epiglottis, aryepiglottic folds
• Vocal fold mobility: detects unilateral or bilateral vocal fold paresis from RLN injury, Parkinson’s disease, tumour
• Pharyngeal and laryngeal secretion management: pooling saliva in the valleculae or pyriform sinuses; this is a powerful indicator of swallowing dysfunction even before food bolus testing
• Epiglottic structure and mobility: post-radiotherapy stiffness, partial epiglottectomy changes
• Pre-swallow pharyngeal residue: food or liquid in the pharynx before the swallow is triggered
• Post-swallow residue: pyriform sinus residue, vallecular residue after swallowing
• Penetration and aspiration (after the swallow moment): direct visualisation of food or liquid entering the laryngeal vestibule or subglottis after the swallow
• Response to penetration/aspiration: does the patient cough? clear the material? or remain unaware (silent aspiration)?
• The effect of therapeutic strategies: chin tuck, head rotation, double swallow — all can be tested directly

What FEES Cannot Show

FEES has one fundamental limitation: during the peak of the swallow, the pharyngeal walls close around the nasendoscope tip, creating a “white-out” period of approximately 0.3–0.8 seconds. Aspiration that occurs precisely during this window — within the swallow — may not be captured. This is why VFSS (which has no white-out period) remains complementary to FEES in some clinical scenarios.

FEES also does not visualise the oral preparatory phase or the upper oesophageal sphincter opening.

Indications for FEES

FEES is clinically indicated whenever instrumental swallowing assessment is needed and:

1. Radiation exposure is a concern — FEES has no radiation; particularly important in young patients, pregnant women, and those with recent high radiation exposure (radiotherapy)
2. The patient is medically unstable or cannot be transported to a radiology suite — FEES can be performed at the bedside, in the ICU, in a care home clinic room, or in the patient’s home
3. Structural laryngeal assessment is needed — FEES provides unsurpassed visualisation of vocal fold movement, mucosal integrity, and laryngeal anatomy; VFSS does not provide this
4. Secretion management needs to be assessed — saliva pooling in the pyriform sinuses is directly visible on FEES
5. The patient is post-tracheostomy — FEES can be performed with the tracheostomy tube in situ; cuff deflation and speaking valve trials can be assessed in the same session
6. Repeated assessments are needed over time — FEES is lower cost and more logistically accessible for serial reassessment than VFSS

In Hong Kong, FEES is now available in most public hospital ENT departments, many rehabilitation units, and an increasing number of HKCSS-affiliated community elderly care centres.

The FEES Procedure: What to Expect

Preparation

• Topical anaesthesia is applied to the more patent nasal passage (typically lidocaine spray or gel)
• The patient is seated upright in their usual feeding position
• No swallowing preparation is required beyond explanation and consent
• Food and liquid boluses are prepared in advance using IDDSI-standardised consistencies; food may be coloured with green food dye to enhance visualisation against the pink laryngeal mucosa

During the Procedure

1. The nasendoscope (typically 3.4–4 mm diameter) is passed through the nose, through the nasopharynx, and positioned in the oropharynx at the level where the epiglottis and laryngeal structures are visible
2. Initial observation of anatomy at rest — vocal fold mobility, secretion pooling, mucosal condition
3. Trial swallows begin with the safest predicted consistency and progress to thinner liquids and solid foods as indicated:
   • IDDSI Level 3 (Moderately Thick) liquid — typically the starting point for high-risk patients
   • IDDSI Level 2 (Mildly Thick) liquid
   • IDDSI Level 0 thin liquid — 5 mL bolus initially
   • Semisolid (IDDSI Level 4 Puréed)
   • Solid food if oral phase is adequate
4. Therapeutic strategies are trialled (chin tuck, head rotation, double swallow) and their effect on residue and aspiration directly observed
5. The procedure is recorded to video for analysis and record

Duration

A typical FEES takes 20–40 minutes including preparation, bolus trials and post-procedure discussion. More complex cases (tracheostomy decannulation assessment, multiple therapeutic strategies) may take longer.

Tolerability

Most patients tolerate FEES well. Passage of the scope may cause mild nasal discomfort. Patients are not required to be nil by mouth beforehand and can eat normally immediately after.

Interpretation: The Penetration-Aspiration Scale

FEES findings for swallowing safety are commonly rated using the Penetration-Aspiration Scale (PAS) (Rosenbek et al., 1996):

PAS 8 represents silent aspiration — the highest-risk finding, which cannot be detected without instrumental assessment.

FEES in Hong Kong: Prof. Karen Chan and HKU

Prof. Karen Chan’s HKU Swallowing Research Lab has been a leading centre for FEES research and training in Hong Kong and the Asia-Pacific region. The Lab has published normative FEES data on Chinese populations, adapted FEES protocols for common Hong Kong food textures (dim sum, rice congee, tofu), and trained SLTs across Hong Kong public hospital clusters in FEES technique and interpretation.

For information on when to request FEES, see When to Refer to a Speech and Language Therapist.

References

1. American Speech-Language-Hearing Association. Adult Dysphagia Practice Portal. https://www.asha.org/practice-portal/clinical-topics/adult-dysphagia/
2. National Institute for Health and Care Excellence. Stroke Rehabilitation in Adults (CG162). https://www.nice.org.uk/guidance/cg162
3. IDDSI. The IDDSI Framework. https://www.iddsi.org/framework
4. Logemann JA, et al. (2015). Disorders of deglutition. Handbook of Clinical Neurology, 129, 465–487. PMID: 26315994