Welcome to today's lesson, where we will discuss Obstructive Sleep Apnea (OSA) and other breathing-related sleep disorders. These medical issues interfere with sleep and affect quality of life. In this post, we will highlight the key points concerning these disorders. This lesson will be less detailed than some, concentrating mainly on assessment, since the management of these conditions is typically handled by other medical specialties or psychiatrists with a fellowship in sleep medicine. OSA is the most common breathing-related sleep disorder, and thus will occupy the bulk of this lesson.
Today's Content Level: Beginner, Intermediate

Introduction to Breathing-Related Sleep Disorders 1
•Sleep-related breathing impairments include apnea (absence of airflow) and hypopnea (reduction in airflow).
•Impairments are often due to airway obstruction but can also result from central (brainstem) changes, metabolic factors, or heart failure.
Each event is classified as central, obstructive, or mixed. In DSM-5-TR, breathing-related sleep disorders include:
Obstructive Sleep Apnea (OSA)
Central Sleep Apnea (CSA)
Sleep-Related Hypoventilation
•Definition: Repeated episodes of upper airway collapse and resultant cessation of breathing during sleep. Episodes last ≥ 10 seconds with decreased oxygen saturation, transient arousals, and sleep fragmentation. OSA is the most common breathing-related sleep disorder.
Assessment:
STOP-BANG Questionnaire: Utilized as a screening tool to identify individuals at risk for OSA. Snoring loudly; Tired during daytime; Observed apneas or choking/gasping during sleep; Pressure (high blood pressure); BMI >35; Age >50; Neck circumference >17" (men), >16" (women); Gender (male > female, but increases post-menopause). A score ≥ 3 suggests high likelihood of OSA and warrants further evaluation.
Obesity is the primary risk factor for OSA. In addition to the STOP-BANG risk factors, consider OSA in patients with maxillary-mandibular retrognathia (abnormal position of the mandible) or micrognathia (small mandible), genetic disorders that affect connective tissue laxity (e.g., Marfan syndrome), or that reduce upper airway patency (e.g., Down's syndrome).
Epworth Sleepiness Scale: Validated self-administered questionnaire designed to assess general level of daytime sleepiness. Positive scores may be an indicator of various sleep disorders, including OSA. See full scale here.
Mallampati score: Scoring system to evaluate the visibility of oropharyngeal structures when a patient opens their mouth and protrudes their tongue. Primarily used to assess the ease of intubation in patients undergoing anesthesia, however is also used in OSA assessments as it demonstrates the potential for airway obstruction during sleep. See more details here.
Polysomnography (PSG): Refer patients for a PSG ("sleep study") if OSA is suspected. Patients spend a night in the sleep laboratory, where they are connected to a number of sensors that provide objective data related to brain activity, eye movements, heart rhythm, breathing patterns, oxygen saturation, and leg movements.
Diagnostic Criteria: Polysomnography is required for the diagnosis of OSA. Must meet either criterion 1 or 2.
≥5 obstructive events (apneas or hypopneas) per hour. Must also include either of the following symptom clusters.
Nighttime symptoms: snoring, snorting, gasping, or breathing pauses.
Daytime symptoms: excessive fatigue or unrefreshing sleep not better explained by another medical condition or sleep disorder.
≥15 obstructive events (apneas or hypopneas) per hour regardless of symptoms.
Severity level is baed on the Apnea-Hypopnea Index (AHI). Mild is 5-15, Moderate is 15-30, and severe is > 30.
Complications
Individuals with OSA are at higher risk for developing the following:
Metabolic Syndrome: abdominal obesity (large waist circumference), HTN, insulin resistance, high blood sugar, high triglycerides, low HDL cholesterol.
Cardiovascular: HTN, atrial fibrillation and other arrhythmias, coronary heart disease, heart failure, stroke.
Neuropsychiatric: depression, irritability, cognitive impairment (memory and concentration issues), dementia.
Miscellaneous: morning headaches, sexual problems, daytime fatigue.
Treatment
Lifestyle: Weight loss and other lifestyle changes such as avoidance of alcohol/sedatives or quitting smoking can have a significant reduction in severity of symptoms. A 10% reduction in weight can lead to a 26% decrease in the AHI.
Continuous Positive Airway Pressure (CPAP): CPAP therapy is the first-line treatment for moderate to severe OSA. The CPAP machine consists of a motor, a hose, and a mask, which can come in various designs to accommodate individual comfort and preferences. The CPAP machine delivers a constant stream of air to keep the airway open, thus preventing airway collapses that lead to apnea or hypopnea and fragmented sleep. Patient compliance is a major problem, with adherence around 50%.
Oral Appliances: Dental devices such as mandibular advancement devices can be used in mild cases.
Positional Devices: Positional devices for OSA can help some patients with predominantly positional OSA. Examples include specialized pillows, wearable belts, and specialized mattresses designed to promote side sleeping or prevent other positions that exacerbate obstruction.
Surgery: Upper airway surgical interventions/implants may be indicated in severe or refractory cases.
•Definition: Repeated episodes of apnea due to impaired respiratory drive from the brain.
Key Difference from OSA:
OSA: respiratory drive is constant, but is impeded by airway obstruction or collapse.
CSA: breathing stops due to lack of respiratory drive from the central nervous system. If there is also airway obstruction, this would be considered mixed.
Subtypes:
Cheyne-Stokes respiration oscillations between apnea and hyperpnea that can occur in stroke, heart failure, and renal failure.
Opioid-induced respiratory depression.
Idiopathic (rare).
Treatment
Optimize underlying condition (e.g., stroke or heart failure management).
CPAP/BiPAP: For symptomatic cases.
•Definition: Sleep-related hypoventilation is characterized by abnormally elevated levels of carbon dioxide (CO₂) during sleep due to inadequate ventilation. This leads to hypoxemia (low blood oxygen) and hypercapnia (high blood CO₂). Polysomnography shows episodes of decreased respiration associated with elevated CO₂ (>45 mmHg) during sleep.
Key Difference from OSA
OSA: respiratory drive is sufficient, but is impeded by airway obstruction or collapse.
Hypoventilation: ventilatory drive or muscle function is insufficient, resulting in sustained CO₂ retention. It is not related to episodic airway collapse.
Subtypes
Idiopathic sleep-related hypoventilation is rare. More commonly, it is related to progressive respiratory impairment secondary to another disorder. These include:
Obesity Hypoventilation Syndrome (OHS): Occurs in individuals with BMI ≥ 30 + hypoventilation. It often overlaps with OSA (Pickwickian syndrome = OSA + OHS). Results from impaired respiratory mechanics and blunted ventilatory response to CO₂.
Congenital Central Hypoventilation Syndrome (CCHS): Rare genetic disorder affecting autonomic control of breathing (PHOX2B mutation). Patients hypoventilate primarily during sleep, sometimes while awake.
Neuromuscular or Chest Wall Disorders: Reduced ventilatory muscle strength (e.g., ALS, muscular dystrophy).
Chronic Lung Disease-Related Hypoventilation: Severe COPD or interstitial lung disease leading to impaired gas exchange.
Treatment
Lifestyle: Weight loss and other lifestyle changes such as avoidance of alcohol/sedatives or quitting smoking can have a significant reduction in severity of symptoms, depending on underlying diagnosis.
Optimize underlying condition (e.g., underlying lung disease or neuromuscular conditions)
BiPAP or CPAP: Provides support for ventilation and reduces CO₂ retention. CPAP is useful for OHS when OSA is also present (Pickwickian syndrome).
Conclusion
•Nice work! We are close to finishing the section on sleep disorders.
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