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Obstructive sleep apnea

Last updated: August 12, 2021

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Obstructive sleep apnea (OSA) is the most common sleep-related breathing disorder and is typically associated with obesity. It is characterized by obstruction of the upper airways due to the collapse of the pharyngeal muscles during sleep, which causes multiple episodes of interrupted breathing (apnea and hypopnea events), leading to alveolar hypoventilation. Severe daytime sleepiness due to sleep disruption is a common symptom. Partners of affected individuals commonly describe observing restless sleep and irregular snoring, gasping, or choking episodes. The diagnosis is based on polysomnography or home sleep apnea testing. Many patients develop hypertension secondary to OSA, the cardiovascular consequences of which can reduce life expectancy. First-line treatment consists of nightly continuous positive airway pressure (CPAP); alternatives include oral appliances and surgical interventions. Lifestyle changes such as weight loss, avoidance of precipitating factors (e.g., alcohol), and improvement of sleep hygiene are recommended.

  • Obstructive sleep apnea (OSA): a sleep-related breathing disorder in which airflow significantly decreases or ceases due to upper airway obstruction (typically in the oropharynx) [1][2]
  • Abnormal breathing events
    • Apnea: complete or nearly complete (≥ 90%) cessation of inspiratory airflow for ≥ 10 seconds [1][3]
    • Hypopnea: airflow reduction by ≥ 30% of the pre-event baseline for ≥ 10 seconds in combination with either desaturation by ≥ 3% or arousal from sleep [3][4][5]
    • Respiratory effort-related arousal (RERA): arousal from sleep due to increased respiratory effort or reduced airflow for ≥ 10 seconds without significant hypopnea or apnea [3]

References:[6][7]

Epidemiological data refers to the US, unless otherwise specified.

Obesity is the most important risk factor for OSA.

References:[8][9]

  • Typical symptoms [5]
    • Restless sleep with waking, gasping, or choking
    • Loud, irregular snoring with apneic episodes (third-party reports)
    • Excessive daytime sleepiness (e.g., patient falls asleep, microsleep while seated)
    • Morning headaches
  • Signs of complications, including:
    • Impaired cognitive function; (e.g., impaired concentration, memory loss) [4]
    • Depression [10]
    • Decreased libido [11]
    • Hypertension with increased pulse pressure [12]

Obstructive sleep apnea is one of the most common causes of secondary hypertension. [13]

General principles [4][5]

  • A detailed evaluation should include:
  • Standardized screening questionnaires may be used to assess risk for OSA in certain clinical settings (e.g., STOP-BANG for preoperative evaluation).
  • Sleep studies are required to confirm the diagnosis and determine the severity of OSA (e.g., using the apnoea-hypopnea index).

The diagnosis of obstructive sleep apnea requires sleep studies and should not be made based on clinical tools or questionnaires alone. [4]

STOP-BANG questionnaire: SSnoring loudly, T – feeling Tired or fatigued, OObserved apneas during sleep, P – high blood Pressure, BBMI > 35, AAge > 50 years, NNeck circumference > 40 cm, G – male Gender. [14]

Laboratory tests

Laboratory tests are not usually considered useful in the diagnosis of OSA but can help identify physiological consequences of OSA and detect associated conditions.

Sleep studies [4][5]

In-laboratory polysomnography (PSG)

  • Description: Physiologic variables are recorded during sleep to diagnose sleep-related disorders.
  • Indications
    • Patients with significant cardiovascular or respiratory disease
    • Suspicion of other types of sleep-related disorders
    • Circumstances precluding a home assessment [4]
    • Home sleep apnea testing is inconclusive or negative.
  • Findings
    • Apnea and hypopnea events
    • Oxygen desaturation
    • Respiratory effort-related arousal events, possibly causing sleep fragmentation
    • In some cases, signs of associated comorbidities (e.g., hypertension, cardiac arrhythmias) [5][17]
  • Important considerations
    • Consider repeated testing if the initial test is negative and clinical suspicion remains (first night effect). [4][5]
    • Consider split-night testing. [4]

In-laboratory polysomnography is the gold standard for the diagnosis of sleep-related breathing disorders and can also help identify other sleep-related conditions (e.g., seizures).

Home sleep apnea testing (HSAT)

  • Description: an ambulatory screening method for sleep-related breathing disorders that assesses ventilation and oxygenation parameters but not sleep stages or arousal events
  • Indications
    • Patients with a high pretest probability for OSA and no significant comorbidities
    • In-laboratory testing is not feasible.
  • Findings: cardiorespiratory findings similar to those in PSG

Due to its lower sensitivity, HSAT cannot be used to rule out the diagnosis of OSA. [4]

Interpretation of sleep study findings [1][4]

Scores

Scores are calculated based on sleep study findings and are then used to diagnose OSA and determine its severity.

  • Apnea-hypopnea index (AHI): number of apneas plus hypopneas per hour of sleep
  • Respiratory disturbance index (RDI): number of apneas plus hypopneas plus RERAs per hour of sleep [18]
  • Respiratory event index (REI): number of apneas plus hypopneas with desaturation of ≥ 4% per hour of recorded time

Diagnostic criteria for OSA [4][19]

Depending on the type of sleep study used, different scores can be calculated. Any of them can be used to diagnose OSA.

  • AHI/RDI/REI ≥ 5 in patients with symptoms of OSA and/or associated comorbidities
  • OR AHI/RDI/REI ≥ 15 in patients without symptoms

Classification of OSA by severity [20]

Severity is graded by the number of sleep-related obstructive breathing events, most commonly using the AHI.

  • AHI 5–15: mild OSA
  • AHI 16–30: moderate OSA
  • AHI > 30: severe OSA

Central sleep apnea (CSA) syndromes [21][22]

Types of CSA [21][22]
Nonhypercapnic CSA Hypercapnic CSA
Etiology
Pathophysiology
  • Reduced central ventilatory drive or reduced ventilation due to underlying disease → ↑ hypoventilation during sleep due to loss of wakeful breathing drive apnea → ↑ PaCO2 → arousal and increased ventilation → ↓ PaCO2 hypoventilation → cycle repeats [23]
  • Clinical features [21]
  • Diagnostics
  • Treatment
    • Optimize treatment of the underlying condition.
    • Ventilation support
      • Recommended in certain forms of CSA, e.g., forms related to heart failure or idiopathic CSA
      • Options include CPAP, BPAP, and Adaptive Servo-Ventilation (ASV). [22][25]
    • Further treatment may be considered based on the underlying cause. [22]

The 3 C’s of Central sleep apnea are Congestive heart failure, CNS trauma or toxicity, and Cheyne-Stokes breathing.

Obesity hypoventilation syndrome (Pickwickian syndrome) [26][27]

Patients presenting with respiratory failure due to OHS are frequently misdiagnosed with COPD. [27]

The differential diagnoses listed here are not exhaustive.

Approach [20][30][31]

  • Treat all patients with diagnosed OSA.
  • First-line treatment: positive airway pressure (PAP)
  • Consider alternative treatment in patients who are unable to tolerate or decline PAP: [1][32][33]
    • Oral appliances
    • Upper airway modifications
    • Positional therapy
  • Supportive care should include management of risk factors, e.g., weight loss and sleep hygiene.

Nocturnal positive pressure therapy is the therapy of choice in OSA. The success of therapy is highly dependent on patient adherence.

Positive airway pressure (PAP)

  • Description: Pressure is used to pneumatically splint collapsible airways open to reduce the frequency of respiratory events. [17]
  • Types
    • Preferred modalities: Continuous PAP (CPAP) or auto-adjusting PAP (APAP)
    • Bilevel PAP (BPAP)
  • Procedure
    • Should be used over the entire sleep period [30]
    • Initial titration can be done using in-laboratory or APAP devices. [30]
    • Minimum starting pressures

Encourage inpatients to continue using PAP during their admission, if possible, as sudden discontinuation is associated with recurrence of OSA symptoms. [34][35]

Alternative treatment options [1][20]

Conservative treatment

Conservative treatment options are usually only appropriate for mild to moderate disease.

  • Oral appliances [32][36]
    • Devices are worn during sleep to maintain mandibular advancement and prevent airway collapse.
    • Custom-fitted titratable devices are preferred.
  • Positional therapy: : devices to keep patients in a lateral as opposed to supine sleeping position [37]

Upper airway modification [33]

  • Description: surgical dilatation of the upper airway or neurostimulation of upper airway muscles
  • Approach: single-stage, multilevel, or stepwise surgery
  • Procedures

Supportive treatment [1]

References:[43][44][45][46][47]

We list the most important complications. The selection is not exhaustive.

  • The mortality rate is higher in patients with severe OSA who do not receive adequate treatment.
  • CPAP ventilation can significantly lower the risk of mortality in OSA.
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