How Obstructive Sleep Apnoea Is Diagnosed, Step by Step

Obstructive sleep apnoea is diagnosed in steps: a screening questionnaire to gauge how severe and disruptive the symptoms are, a thorough ENT examination that locates where the airway narrows, and a sleep study that counts how often breathing is reduced or stops during sleep. Drug-induced sleep endoscopy is added when surgery is being planned. Each step answers a different question, and together they decide the treatment.

Dr. Trisha Srivastava, Consultant, ENT, Artemis Hospitals, Gurugram, India, describes the clinician's task simply: when a patient comes in with snoring or disturbed sleep, analyse the patient, give them the questionnaire, understand how much the poor sleep is affecting their daily routine, and do a thorough ENT examination. Treatment options follow from what the examination finds. This article walks through that pathway, starting with the question every referring doctor faces: when does snoring need an assessment at all? For the underlying science of sleep and the causes of snoring, see the complete guide to the science behind snoring.

When does snoring need an assessment?

Snoring needs an assessment when it is chronic, not when it is occasional. Dr. Srivastava separates the two clearly. Snoring during a common cold or a sore throat, for a week or 15 days, is understandable and settles on its own. Snoring after an exhausting day is physiological. The concern is snoring that happens every night, with mouth breathing and tiredness the following day.

Signs that should prompt referral to an ENT specialist

Dr. Srivastava starts with the level of obstruction, and with symptoms the patient can notice without a partner's report:

• One nostril that is always blocked.
• A nose that clogs up whenever the person lies down to sleep.
• Unrefreshing sleep: the patient believes they slept well, but wakes with a headache or feels tired the next day.
• Chronic snoring, almost every night, with sleeping open-mouthed.
• Snoring so loud that family members complain about their own sleep.
• In a young adult, blood pressure that is still within the normal range but trending upwards.

The last point deserves emphasis for general practitioners. Dr. Srivastava's example is a patient of 28 or 29 whose blood pressure is creeping up while still technically normal. Such a patient can come for a routine ENT examination to rule out an underlying airway problem, because the metabolic and cardiovascular effects of poor sleep take years to appear.

The role of the general practitioner

GPs manage most common upper airway problems themselves, such as colds, and in Dr. Srivastava's words they do a great job of it. When a problem does not settle, they refer on. GP referrals make up probably 20 to 30% of her outpatient practice. The rest comes from patients referred by people she has already treated, from cross-referrals within the hospital, and from public awareness work.

Step 1: STOP-Bang and other screening questionnaires

The assessment begins when the patient walks in, with a questionnaire that shows how severe the problem is and how much the symptoms bother the patient the next day. Dr. Srivastava names three standard instruments.

STOP-Bang questionnaire. A screening tool for obstructive sleep apnoea built on eight yes-or-no items: Snoring, Tiredness, Observed apnoea, high blood Pressure, BMI over 35, Age over 50, Neck circumference over 40 cm and male Gender. A score of 0 to 2 indicates low risk, 3 to 4 intermediate risk and 5 to 8 high risk.

Epworth Sleepiness Scale. The patient rates the chance of dozing in eight everyday situations, such as sitting and reading or being a passenger in a car, on a scale of 0 to 3. The total ranges from 0 to 24, and a score above 10 indicates excessive daytime sleepiness.

Pittsburgh Sleep Quality Index. A broader questionnaire on sleep quality over the previous month, covering seven components such as sleep latency, duration and daytime dysfunction. A global score above 5 indicates poor sleep quality.

Questionnaires do not diagnose sleep apnoea. They establish how likely it is and how much the patient is affected, which guides how far and how fast the work-up should go.

Neck circumference: what counts as a thick neck

A thick neck appears in STOP-Bang and in Dr. Srivastava's own clinical scenarios, and doctors in the session asked what it means. Her answer is that a thick neck means fat around the neck, not muscle. During sleep, muscle tone falls; fat around the neck then makes the airway collapse and pushes the base of the tongue back over the epiglottis.

By the definition she uses for obstructive sleep apnoea, a neck circumference of more than 43 cm in men and more than 40 cm in women counts as a thick neck. Usually, a patient who is obese will also have a thick neck. A tape measure gives a quick, objective risk marker that any clinic can record.

Step 2: ENT examination with nasal endoscopy and laryngoscopy

The examination is where the cause is found. Dr. Srivastava advises that every snoring patient gets a thorough ENT examination with two key components.

Diagnostic nasal endoscopy

Diagnostic nasal endoscopy examines the inside of the nose with a thin camera, the endoscope, which shows the nasal cavity in detail. The examiner checks for:

• A deviated nasal septum.
• Turbinate hypertrophy (enlarged ridges on the side walls of the nose).
• A polypoidal mass in the nose.

Examination of the oral cavity complements this. In her first clinical scenario, the oral examination showed a bulky tongue and a bulky palate, findings that point to obstruction at the retropalatal and tongue-base levels.

Awake video laryngoscopy

Dr. Srivastava regards video laryngoscopy as a very good tool for assessing the dynamics of the upper airway, and her centre performs it. It is done with the patient awake. A flexible fibre-optic scope is introduced through the nose and passed down to examine, in sequence:

1. The nose.
2. The nasopharynx.
3. The retropalatal area.
4. The posterior part of the tongue.
5. The vocal cords.

The examination shows how compromised the airway is and which critical areas need to be targeted. It turns a vague complaint of snoring into a map of the obstruction.

Step 3: the sleep study, from Level 1 to Level 4

A sleep study measures what actually happens during sleep: how many apnoeas and hypopnoeas occur, how far oxygen saturation falls, and whether the events are obstructive or central. Sleep studies are graded into levels by how much they record and where they are done.

Level 1: in-hospital polysomnography. Polysomnography is an overnight recording of breathing, oxygen levels, heart rhythm and sleep stages. The patient is admitted and connected to a range of monitors. The study counts episodes of apnoea and hypopnoea and shows whether they are all obstructive or whether some are central apnoeas (pauses caused by the brain not signalling to breathe, rather than by a blocked airway). It is the most complete study.

Level 2: unattended full polysomnography. The same full set of recordings as Level 1, but without a technician present through the night.

Level 3: home sleep study. In Dr. Srivastava's practice, a technician visits the patient's home and connects a smaller set of monitors. A Level 3 study typically records airflow, breathing effort, oxygen saturation and heart rate. It is more convenient, and it has a practical advantage: many patients, because of anxiety, cannot sleep well in hospital, so a hospital study may not give good results.

Level 4: limited monitoring. Level 4 devices record only one or two signals, most often oxygen saturation. Consumer smartwatches that track heart rate and oxygen levels overnight give basic information, such as a spike in heart rate or a fall in oxygen saturation, but they do not provide the detail of a formal study and are not diagnostic.

Reading the result: AHI and sleep apnoea severity

The key output of a sleep study is the apnoea-hypopnoea index (AHI), the average number of apnoeas and hypopnoeas per hour of sleep. In adults, an AHI of 5 to 14 indicates mild obstructive sleep apnoea, 15 to 29 moderate, and 30 or more severe. Oxygen saturation is read alongside it. Dr. Srivastava describes patients with very severe disease whose saturation falls into the 70s and even the 60s during sleep.

Step 4: drug-induced sleep endoscopy (DISE)

DISE examines the airway under sedation that reproduces the muscle relaxation of sleep. It shows how and where the airway collapses during sleep, which an awake examination cannot fully show.

At Dr. Srivastava's institute, DISE is performed in the operating theatre immediately before planned surgery. The team evaluates the retropalatal area and uses the findings to decide what type of palatoplasty the patient needs. This places DISE as a surgical planning tool rather than a screening test: it refines the operation once the decision to operate has been made.

How the diagnosis of obstructive sleep apnoea shapes treatment

The point of this staged pathway is to tailor treatment. A patient whose examination shows a badly deviated septum needs a different plan from a patient with a thick neck and no structural block, and both differ from a child with large tonsils and adenoids. Severity on the sleep study, the level of obstruction on examination and the patient's own preferences together determine whether the plan centres on lifestyle change, a positive airway pressure machine, surgery or a combination.

Those options, including the practical differences between CPAP and BiPAP and the surgical procedures for each level of the airway, are covered in CPAP vs BiPAP: how to choose the right airway therapy. Doctors' questions from the session, including the referral threshold and the definition of a thick neck, are answered in the Live Discussion.

Dr. Srivastava's summary for patients is the practical test: if snoring is occasional, or limited to days of exhaustion, there is little to worry about. If it is chronic, loud enough to disturb the family, or followed by tired, unproductive days, it is time for an ENT assessment and, where indicated, a sleep study.