- Clinical science
Obstructive sleep apnea (OSA) is the most common breathing-related sleep disorder and is typically associated with obesity. It is characterized by obstruction of the upper airways due to the collapse of the pharyngeal muscles. OSA results in multiple episodes of interrupted breathing (apnea and hypopnea) during sleep, leading to alveolar hypoventilation. Patients generally suffer from severe daytime sleepiness and impaired cognitive function (e.g., deficits in attention and/or memory) as a result of sleep disruption. Their partners describe restless sleep associated with irregular snoring, gasping, or choking episodes. Diagnosis is based on the assessment of risk factors and polysomnography. Many patients with OSA (> 50%) are affected by secondary hypertension. The cardiovascular consequences of secondary hypertension reduce life expectancy. However, these effects can be counteracted with weight loss and nightly continuous positive airway pressure (CPAP). Other important aspects of management include avoidance of precipitating factors (e.g., alcohol) and improvement of sleep hygiene.
- Obstructive sleep apnea (OSA): breathing-related sleep disorder in which airflow significantly decreases or ceases because of upper airway obstruction (typically the oropharynx)
- Apnea: respiratory arrests of ≥ 10 seconds
- Hypopnea: reduction of airflow by ≥ 50% for ≥ 10 seconds in combination with reduction of blood oxygenation by ≥ 3% or EEG arousal
- Apnea-hypopnea index (AHI)
- Respiratory effort-related arousal (RERA): series of breaths (for 10 seconds or more) that lead to arousal due to increased respiratory effort
- Respiratory disturbance index (RDI) (hypopnea events + apnea events + respiratory effort-related arousal events)/hours of sleep
- Obstruction of the upper airways due to the collapse of the pharyngeal muscles during sleep
- Obesity, especially around the neck (short, wide “bull neck”)
- Structural abnormalities that impair respiratory flow: tonsillar hyperplasia, nasal septum deviation, enlarged uvula, tongue, or soft palate; nasal polyps; overbite with a small chin; hypertrophied pharyngeal muscles
- Alcohol consumption before sleep
- Intake of sedatives and/or beta-blockers before sleep
- Family history
Obesity is the most important risk factor for OSA.
- Obstruction of the upper airways → apnea → ↓ partial pressure of oxygen in arterial blood (PaO2), ↑ partial pressure of carbon dioxide in arterial blood (PaCO2, also known as hypercapnia)
- 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 during meetings or while watching TV)
- Impaired cognitive function; (e.g., impaired concentration, memory loss)
- Depression, decreased libido
- Initial assessment: standardized questionnaires and third-party reports; (interview sleeping partner regarding snoring and respiratory interruptions)
- Laboratory tests are not usually considered useful in the diagnosis of OSA, but may help identify underlying conditions or physiological consequences of OSA.
Polysomnography: first-line method
- Parameters measured in addition to those recorded by polygraphy:
- Classic findings
- Home sleep apnea testing
Central sleep apnea (CSA) (< 10%)
- Definition: Breathing-related sleep disorder characterized by episodic ventilation and respiratory effort caused by impaired respiratory center stimulation. Airway obstruction is absent.
- Etiology: idiopathic (primary CSA) or caused by an underlying disorder (secondary (CSA)
- Risk factors
- Pathophysiology: lack of stimulation to the respiratory center with patent upper airways → periodic lack of respiratory muscle innervation → interruption of thoracic and/or abdominal respiratory movements
- Morning headaches
- Repeated waking at night
- Daytime sleepiness
- Association with OSA is very common
- Treat underlying disorder (if present)
- Definition: : a breathing disorder that only affects morbidly obese individuals; ; frequently accompanied by OSA, it is characterized by diurnal hypercapnia
- Etiology: morbid obesity
- Risk factors: : identical to those of obesity
- Pathophysiology: ↑ production of CO2; + sleep disordered breathing (e.g., OSA) + failure of ventilatory compensatory mechanisms → alveolar hypoventilation
- Same symptoms as those of OSA
- Headaches and severe sleepiness
- Diagnostic criteria
- Weight loss
- Nasal intermittent positive pressure ventilation
The differential diagnoses listed here are not exhaustive.
Mild to moderate OSA (mild symptoms and < 20 apneic episodes)
Severe OSA (> 20 apneic episodes and alterations in arterial oxygen saturation)
- Resection of the uvula and redundant retrolingual, soft palate, and tonsillar tissue
- This procedure should only be considered as a supplementary treatment.
- Therapeutic option later in the course of severe OSAH. The intervention is very painful and involves temporary but potentially long term (partial) glossectomy trouble swallowing and speaking.
- Maxillomandibular advancement (MMA)(bimaxillary advancement): advancement of the maxilla and mandible by up to 2 cm, tightening of soft palate and base of the tongue ; highly effective, but complicated
- Bilevel positive airway pressure (BPAP)
- Continuous positive airway pressure (CPAP)
- Surgery (uvulopalatopharyngoplasty)
Nocturnal positive pressure therapy via CPAP is the therapy of choice in symptomatic OSA. The success of therapy is highly dependent on patient adherence and regular monitoring with sleep studies!
- Hypoxia-induced cardiac arrhythmia
- Pulmonary hypertension and cor pulmonale
- Global respiratory insufficiency
- Cardiac infarction, stroke, and sudden cardiac death
- Risk of accidents (e.g., car crashes, occupational accidents) due to microsleep
- Increased risk of developing vascular dementia
- Poor sleep leads to increased appetite and obesity.
We list the most important complications. The selection is not exhaustive.