OBSTRUCTIVE SLEEP APNOEA

✓ Medically ReviewedDISEASEID: MDBT0181🚨 TRIAGE: ROUTINEICD-10: G47.3

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Definition

CLINICAL DEFINITION

Obstructive sleep apnoea (OSA) is a sleep-related breathing disorder characterised by recurrent episodes of partial or complete upper airway obstruction during sleep, leading to reduced or absent airflow (hypopnoea or apnoea) despite ongoing respiratory effort. These events typically result in oxygen desaturation, sleep fragmentation, and sympathetic nervous system activation.

IN PLAIN ENGLISH

Obstructive sleep apnoea is a condition where the upper airway repeatedly collapses or becomes blocked during sleep, causing breathing to stop or become very shallow. This leads to poor sleep quality, frequent awakenings, and drops in blood oxygen levels, often causing loud snoring and daytime sleepiness.

COMMON MISCONCEPTION / WHAT IT DOES NOT MEAN

Obstructive sleep apnoea is NOT central sleep apnoea, where breathing effort itself ceases due to a lack of respiratory drive from the brainstem. It is also distinct from primary snoring, which lacks the significant airflow limitation, oxygen desaturation, and sleep fragmentation seen in OSA.

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Word Breakdown

ob-, a-

=ob- (against/blocking) and a- (without)

pnoea

=breathing (from Greek 'pnoia')

Literal Meaning: Breathing cessation due to a physical blockage in the airway

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Abbreviations

OSA=Obstructive Sleep Apnoea — the standard clinical abbreviation

AHI=Apnoea-Hypopnoea Index — key metric for diagnosing and grading OSA severity

CPAP=Continuous Positive Airway Pressure — first-line treatment for moderate to severe OSA

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Category-Specific Context

As a disease, OSA exists on a spectrum of severity defined by the frequency of respiratory events (AHI) and the degree of associated hypoxaemia and sleep fragmentation. It is classified into mild, moderate, and severe categories, which guide management decisions and predict the risk of long-term cardiovascular and metabolic complications.

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Clinical Context & Usage

CLINICAL SETTINGS

Sleep ClinicRespiratory Medicine OPDGeneral PracticeCardiology ClinicOtolaryngology OPDPreoperative Assessment Clinic

USAGE & DOCUMENTATION NOTES

In clinical documentation, OSA severity is typically reported alongside the AHI (e.g., 'severe OSA with an AHI of 45 events/hour'). Notes often document the patient's adherence to positive airway pressure (PAP) therapy, measured in hours of use per night, and the presence of residual symptoms like daytime somnolence despite treatment.

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Primary Causes & Pathophysiology

PATHOPHYSIOLOGY

During sleep, particularly in the supine position and during REM sleep, there is a physiological reduction in upper airway muscle tone. In patients with OSA, anatomical factors such as obesity, retrognathia, macroglossia, or pharyngeal soft tissue hypertrophy narrow the upper airway. When the negative inspiratory pressure exceeds the dilating force of the pharyngeal muscles, the airway collapses, causing apnoea or hypopnoea. This leads to progressive hypercapnia and hypoxaemia, which stimulate chemoreceptors and trigger a cortical micro-arousal. The arousal restores airway muscle tone and re-establishes airflow, but fragments sleep architecture and causes a surge in sympathetic nervous system activity, contributing to systemic hypertension and endothelial dysfunction.

PRIMARY CAUSES

Obesity

Excess parapharyngeal fat deposition narrows the upper airway lumen and increases tissue collapsibility, while reduced lung volumes decrease tracheal traction on the pharynx.

Craniofacial abnormalities

Conditions such as retrognathia, micrognathia, or maxillary constriction reduce the bony enclosure of the upper airway, predisposing it to collapse during sleep.

Pharyngeal soft tissue hypertrophy

Enlarged tonsils, adenoids (especially in children), or an elongated soft palate and uvula physically obstruct the oropharyngeal airway.

Neuromuscular disorders

Conditions affecting bulbar muscle tone or coordination impair the compensatory dilation of the upper airway during inspiration.

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Drug-Induced Causes

💊 Central nervous system depressants (benzodiazepines, opioids, alcohol) ↗

Mechanism: Exacerbate upper airway collapsibility by further reducing genioglossus and pharyngeal dilator muscle tone during sleep, and blunt the arousal response to hypoxia and hypercapnia.

→ Avoid or minimise use, particularly before bedtime; screen for OSA before prescribing long-term opioids.

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Epidemiology

Prevalence:Affects approximately 4% of middle-aged men and 2% of middle-aged women in the general population, though prevalence estimates rise to over 20% when including mild, asymptomatic cases identified on population-based polysomnography. Prevalence increases significantly with age and obesity.

Age Group:Most commonly diagnosed in middle-aged and older adults (40–70 years). In children, it typically peaks between 2 and 8 years of age, primarily driven by adenotonsillar hypertrophy.

Sex Predilection:Male

Geographic Distribution:Globally distributed, but prevalence correlates strongly with regional obesity rates. Craniofacial phenotypes in certain Asian populations result in a higher prevalence of OSA at lower body mass indices compared to Western populations.

Red Flags & Triage ★

TRIAGE LEVEL

🚨 ROUTINE

DO NOT MISS — LIFE-THREATENING PRESENTATIONS

Obesity Hypoventilation Syndrome (OHS) — in obese patients with OSA, check awake daytime PaCO2; missing OHS alters ventilatory support requirements and carries higher mortality.
Acromegaly or Hypothyroidism — consider screening in patients with refractory OSA or characteristic physical features, as treating the underlying endocrine disorder can resolve the airway obstruction.

URGENT EVALUATION TRIGGERS

Witnessed prolonged apnoeas with severe cyanosis or gasping — requires prompt respiratory evaluation.
Excessive daytime sleepiness causing near-misses or motor vehicle accidents — requires immediate driving restriction and urgent sleep study.
New-onset right heart failure or severe pulmonary hypertension in the context of untreated OSA — requires urgent cardiopulmonary assessment.

Contraindications & Precautions

CONTRAINDICATIONS

Central sleep apnoea or hypoventilation syndromes — CPAP without backup ventilation may be insufficient or inappropriate for pure central events.
Severe bullous lung disease or recurrent pneumothorax — positive airway pressure may increase the risk of barotrauma.
Copious respiratory secretions or impaired airway protection — increased risk of aspiration with positive pressure therapy.

SPECIAL PRECAUTIONS

Claustrophobia or mask intolerance — requires gradual desensitisation
alternative mask interfaces
or consideration of oral appliances.
Concurrent use of CNS depressants — requires close monitoring as these may worsen apnoea severity and blunt the arousal response.
Perioperative period — patients with OSA are highly sensitive to opioids and anaesthetics; require enhanced postoperative respiratory monitoring and early reinstitution of PAP therapy.

Complications

DOWNSTREAM CLINICAL COMPLICATIONS

Systemic hypertension — recurrent nocturnal hypoxaemia and sympathetic surges lead to sustained daytime blood pressure elevation.
Cardiovascular disease — increased risk of coronary artery disease
heart failure
atrial fibrillation
and stroke due to endothelial dysfunction and oxidative stress.
Metabolic syndrome and type 2 diabetes mellitus — intermittent hypoxia and sleep fragmentation promote insulin resistance.
Neurocognitive impairment and mood disorders — chronic sleep fragmentation leads to excessive daytime sleepiness
poor concentration
memory deficits
and increased risk of depression.
Motor vehicle accidents — excessive daytime somnolence significantly increases the risk of occupational and driving accidents.

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Reference Ranges

NORMAL RANGEApnoea-Hypopnoea Index (AHI) < 5 events per hour is considered normal in adults.

CRITICAL (PANIC) VALUEAHI ≥ 30 events per hour indicates severe OSA, which carries a high risk of cardiovascular complications and requires prompt initiation of therapy.

UNIT OF MEASUREMENTEvents per hour (for AHI and Respiratory Disturbance Index)

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Confused With (LASA & DDx) ★

LEXICAL (LASA) — SIMILAR NAMES

Central Sleep Apnoea

Both are sleep-related breathing disorders, but central sleep apnoea involves a lack of respiratory effort from the brainstem, whereas OSA involves physical airway obstruction despite ongoing effort.

Obesity Hypoventilation Syndrome

Often coexists with OSA, but OHS is defined by awake daytime hypercapnia (PaCO2 > 45 mmHg) in an obese patient, not just sleep-disordered breathing.

CLINICAL DIFFERENTIAL DIAGNOSES (DDx)

Central Sleep Apnoea

Key Distinguishing Feature: Polysomnography shows absent respiratory effort during apnoeic events, unlike the continued or increased effort seen in OSA.

Primary Snoring

Key Distinguishing Feature: Loud snoring without significant airflow limitation, oxygen desaturation, or cortical arousals on polysomnography (AHI < 5).

Narcolepsy

Key Distinguishing Feature: Excessive daytime sleepiness and cataplexy driven by hypocretin deficiency, confirmed by multiple sleep latency testing (MSLT) showing early REM onset, rather than upper airway obstruction.

Nocturnal Asthma or COPD

Key Distinguishing Feature: Awakenings due to bronchospasm, wheezing, and cough, responsive to bronchodilators, rather than mechanical airway collapse.

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Clinical Pearls

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The Epworth Sleepiness Scale (ESS) is a useful screening tool for subjective daytime somnolence, but a normal score does not rule out severe OSA, as some patients adapt to chronic sleep fragmentation and under-report sleepiness.

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Home Sleep Apnoea Testing (HSAT) is highly specific but less sensitive than in-lab polysomnography; a negative HSAT in a patient with high clinical suspicion must be followed by an in-laboratory study.

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Weight loss of 10–15% in obese patients with OSA can significantly reduce the AHI and, in some mild-to-moderate cases, lead to disease remission, making lifestyle intervention a critical adjunct to device therapy.

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Patients with OSA are highly sensitive to the respiratory depressant effects of opioids and benzodiazepines; perioperative protocols should minimise these agents and ensure early postoperative reinstitution of CPAP.

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Example Usage & SOAP

CLINICAL SENTENCE

"The patient is a 52-year-old male with a BMI of 34 kg/m² referred for evaluation of loud snoring, witnessed apnoeas, and an Epworth Sleepiness Scale score of 16, highly suggestive of moderate-to-severe obstructive sleep apnoea."

IN A SOAP NOTE

S: 48yo M presents with 2-year history of loud snoring, witnessed choking episodes during sleep, and unrefreshing sleep. Reports falling asleep while driving. ESS score 18. O: BMI 32 kg/m². Neck circumference 44 cm. Mallampati score III. Tonsils 1+ (not enlarged). BP 148/92 mmHg. A: High pre-test probability for moderate-to-severe obstructive sleep apnoea. Concurrent poorly controlled hypertension likely secondary to untreated OSA. P: 1. Order home sleep apnoea test (HSAT). 2. Advise strict avoidance of alcohol and sedatives before bedtime. 3. Counsel on weight loss and sleep hygiene. 4. Review HSAT results in 2 weeks to discuss CPAP initiation.

DIFFERENTIAL DIAGNOSIS CONTEXT

Differential for excessive daytime sleepiness and snoring: (1) Obstructive Sleep Apnoea — confirmed by AHI ≥ 5 on polysomnography with respiratory effort; (2) Central Sleep Apnoea — absent respiratory effort during events, often associated with heart failure or opioid use; (3) Obesity Hypoventilation Syndrome — awake PaCO2 > 45 mmHg; (4) Narcolepsy — positive MSLT with sleep onset REM periods; (5) Hypothyroidism — elevated TSH, associated with macroglossia.

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Classifications & Scoring

GRADING SYSTEM

Apnoea-Hypopnoea Index (AHI) Severity Grading

Classifies OSA severity in adults based on the number of apnoeas and hypopnoeas per hour of sleep: Mild (5–14.9 events/hour), Moderate (15–29.9 events/hour), Severe (≥ 30 events/hour).

SCORING TOOL

Epworth Sleepiness Scale (ESS)

An 8-item self-administered questionnaire assessing the likelihood of dozing off in various everyday situations. Scores range from 0 to 24; a score > 10 indicates excessive daytime sleepiness.

SCORING TOOL

STOP-BANG Questionnaire

A screening tool for OSA risk assessing Snoring, Tiredness, Observed apnoea, Pressure (hypertension), BMI > 35, Age > 50, Neck circumference > 40cm, and Gender (male). Scores ≥ 3 indicate high risk.

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Prognosis

SHORT-TERM OUTCOME

With effective treatment such as CPAP or mandibular advancement devices, symptoms like snoring and daytime sleepiness typically resolve within weeks, and neurocognitive function improves rapidly.

LONG-TERM PROGNOSIS

Untreated moderate-to-severe OSA is associated with increased long-term cardiovascular mortality. Consistent adherence to CPAP therapy significantly reduces the risk of fatal and non-fatal cardiovascular events and improves overall survival.

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References & Coding

ICD-10 DIAGNOSTIC CODE

G47.3

LITERATURE CITATIONS & GUIDELINES

[1]Epstein LJ, Kristo D, Strollo PJ Jr, et al. Clinical guideline for the evaluation, management and long-term care of obstructive sleep apnea in adults. J Clin Sleep Med. 2009;5(3):263-276.

[2]Qaseem A, Dallas P, Owens DK, et al. Management of obstructive sleep apnea in adults: a clinical practice guideline from the American College of Physicians. Ann Intern Med. 2013;159(7):471-483.

[3]Gottlieb DJ, Punjabi NM. Diagnosis and Management of Obstructive Sleep Apnea: A Review. JAMA. 2020;323(14):1389-1400.

MEDICAL DISCLAIMER — This content is intended for educational purposes and qualified healthcare professionals only. Always refer to current clinical diagnostic criteria, institutional protocols, and official guidelines. Medobo is not responsible for clinical decisions made based on this content.