Sleep Endoscopy

What Sleep Endoscopy Is and How It Works

Sleep endoscopy — known internationally as DISE (Drug-Induced Sleep Endoscopy) — is a diagnostic procedure in which the upper airway of a pharmacologically sedated patient is observed directly with the help of a thin, flexible endoscope. The aim is to determine clearly at which anatomical level the obstruction occurs in snoring and sleep apnoea, and by which mechanism it develops.

A standard examination and sleep studies (polysomnography) are performed while the patient is awake, or they measure sleep data; however, they cannot show how the relaxed muscles and soft tissues behave during the actual apnoea moment. Because the anatomical source of the obstruction (nose, soft palate, tongue base, hypopharynx, or more than one level) is not visible, some surgeries based only on this data fall short. Sleep endoscopy removes this blind spot, making targeted and accurate surgical planning possible.

The procedure is diagnostic, not surgical. Undergoing sleep endoscopy does not mean that surgery will be necessary; on the contrary, where appropriate, it prevents unnecessary or misdirected surgery.

When It Is Evaluated

Sleep endoscopy is not recommended for every patient with sleep apnoea. It primarily comes into consideration in the following situations:

• Patients who cannot tolerate a CPAP device — to plan a surgical alternative
• Patients with moderate to advanced sleep apnoea who require anatomical localisation before surgery
• Identifying the source of obstruction in cases of social snoring
• Suspicion of multi-level rather than single-level obstruction
• Patients who have previously undergone sleep apnoea surgery but whose complaints persist — to identify the reason for failure
• Atypical paediatric cases (adenoid tissue, craniofacial syndromes; paediatric DISE is performed under specific indications)
• Suitability assessment of patients who may be candidates for a mandibular advancement device (MAD)
• Observation of positional effects in cases of positional sleep apnoea

In patients with mild sleep apnoea who respond to standard treatment options, sleep endoscopy is not routine.

The decision on indication is based not on a single parameter but on a holistic assessment: polysomnography results, clinical complaints, anatomical examination, CPAP tolerance, and the patient’s treatment preferences are considered together. Just as sleep endoscopy is not a test recommended routinely for every patient, it is also not performed simply “just in case”; it is a targeted diagnostic tool planned to answer a clear clinical question.

Its Place in the Diagnostic Pathway and Preparation

Sleep endoscopy represents a specific step in the assessment chain for sleep disorders:

1. Clinical assessment: Snoring, daytime sleepiness, history of witnessed apnoea, BMI, neck circumference, anatomical examination
2. Polysomnography: Apnoea-hypopnoea index (AHI), oxygen saturation, sleep stages
3. Mallampati and Friedman assessment: Intraoral anatomical scoring
4. Sleep endoscopy: Targeted identification of the obstruction level
5. Treatment planning: CPAP, MAD, positional therapy, weight management, or targeted surgery

Standard preparation points before the procedure:

• Fasting for 6-8 hours (required for sedation)
• Adjustment of blood-thinning medications with the doctor’s approval
• Review of chronic medications
• Standard pre-anaesthetic investigations

Before the procedure, the overall picture is explained to the patient clearly; the safety of sedation, what will be observed, and how the results will be interpreted are clarified.

The Procedure

The procedure is carried out in an operating theatre or endoscopy unit under the supervision of an anaesthetist. Short-acting sedative drugs (usually propofol or dexmedetomidine) are administered intravenously. The patient is brought to a state of sleep close to natural sleep — this point is critical, because anaesthesia that is too deep can relax all the tissues and produce a “false positive” picture of obstruction.

Once the depth of sleep reaches an appropriate level, a thin, flexible endoscope is advanced through the nose and the upper airway is examined systematically. The regions typically evaluated are:

• Nose: Septum, turbinates, valve narrowing
• Velum (soft palate): Anteroposterior or concentric collapse pattern
• Oropharynx: Lateral wall narrowing, tonsil structure
• Tongue base: Backward collapse, hypertrophy of the tongue base
• Epiglottis (hypopharynx): Backward closure of the epiglottis

Obstruction patterns are recorded using the international VOTE classification (Velum, Oropharynx, Tongue, Epiglottis). For each level, the degree (partial/total) and the direction (anteroposterior/lateral/concentric) are determined.

In some cases, positional manoeuvres, a jaw thrust, and a mandibular advancement manoeuvre are performed to observe which approach may be beneficial. The procedure takes 20-40 minutes; the patient wakes a short while after the sedation is stopped.

Video recording throughout the procedure is the standard approach. The recording is then examined in detail and, if necessary, discussed with a multidisciplinary team (sleep specialist, anaesthetist, ENT surgeon). The video recording is also an effective tool in discussion with the patient: when the patient sees with their own eyes how their obstruction occurs, adherence to the treatment plan increases markedly. This visualisation turns an abstract diagnosis into a concrete picture.

Interpreting the Results and Their Effect on the Treatment Plan

Sleep endoscopy is not a result in itself but a decision-support tool. The data obtained guide the following decisions:

• Single-level obstruction: Targeted single surgery (e.g. soft palate operation, tongue base ablation, tonsillectomy)
• Multi-level obstruction: A staged or combined approach, with prioritisation of non-surgical methods in some cases
• Concentric palatal collapse: A contraindication for hypoglossal nerve stimulation — it is not suitable in these patients
• Marked opening with the mandibular advancement manoeuvre: A patient profile that may be a candidate for a MAD (intraoral appliance)
• Marked positional effect: Adding positional therapy (avoiding supine sleep)
• Predominantly nasal obstruction: The contribution of septoplasty / turbinate surgery to the treatment plan

The result report includes the levels observed, the collapse patterns, and the responses to manoeuvres. The doctor interprets this data together with the polysomnography results, the patient’s history of CPAP use, BMI, and expectations.

After the procedure, the patient is observed in the clinic for a few hours; operating heavy machinery, driving, and making important decisions are not recommended on the same day. A return to normal activity the following day is usually possible.

Risks and Points to Consider

Sleep endoscopy is a procedure performed in the presence of an anaesthetist, with rare serious complications. Nevertheless, the points to consider are as follows:

• Risks of sedation: Respiratory depression, changes in blood pressure — anaesthetic monitoring is standard
• Temporary throat irritation, mild nosebleed related to the passage of the endoscope, short-lived
• Drug reactions: Rare; any history of allergy is assessed beforehand
• Risk of aspiration: Compliance with the required fasting period is decisive
• Variability in interpretation: The procedure requires experience; adherence to standard protocols increases the reliability of the result

In cases of uncontrolled cardiac disease, advanced lung disease, or a high anaesthetic risk, the procedure is either planned under different conditions or the risk-benefit balance is reassessed.

Comparison with Other Sleep Diagnostic Methods

Sleep endoscopy does not replace other diagnostic methods — it complements them:

• Polysomnography (PSG): Measures the presence and severity of apnoea. It provides an AHI value but does not show the location of the obstruction. It is the fundamental test for diagnosis.
• Home sleep apnoea test (HSAT): A simplified version of PSG. It is sufficient in certain cases but provides no anatomical information.
• Cephalometry / 3D imaging: Provides static anatomical data but does not show the dynamic obstruction during sleep.
• Müller manoeuvre: Assessment of the upper airway under negative pressure in the awake patient. Once commonly used, it has largely given way to DISE as the latter has become more widespread.
• Sleep endoscopy (DISE): Shows the location and mechanism of dynamic obstruction during sleep. On its own, it does not diagnose apnoea.

In a complete sleep apnoea assessment, polysomnography and sleep endoscopy complement each other: the former for diagnosis, the latter for surgical planning.

When to Consult a Specialist

Complaints such as loud snoring, pauses in breathing at night, morning headache, excessive daytime sleepiness, problems with attention and memory, and uncontrolled blood pressure require assessment for sleep apnoea. At this point, the priority is an examination by a sleep-specialist ENT physician and polysomnography.

In patients who cannot tolerate a CPAP device, who have previously undergone sleep apnoea surgery without benefit, or who are seeking a surgical alternative, sleep endoscopy is a critical step in mapping out the treatment plan. The need for and timing of this test are determined according to the individual’s clinical picture.

It is important to remember that sleep apnoea is a chronic health problem. Untreated sleep apnoea is associated not only with daytime sleepiness but, in the long term, with an increased risk of cardiovascular disease, metabolic imbalance, loss of cognitive performance, and a marked decline in overall quality of life. For this reason, the attitude of “I can manage for now, there is no need” is risky for long-term health. Accurate diagnosis and targeted treatment are the foundation of both quality of life and long-term health prospects.