Sleep apnea

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Saarah T. Alkhairy, M.D.

Sleep apnea was first described in literature in the 19th century. It was often misdiagnosed as either narcolepsy or skepticism. In 1981, Collin Sullivan invented the continuous positive airway pressure (CPAP) for the treatment of sleep apnea. Prior to its recognition as a unique disorder, sleep apnea was viewed as either a type of insomnia or an age-related phenomenon.

• In 1890, Silas Weir Mitchell, a neurologist and American toxicologist, described sleep apnea as respiratory failure in sleep because of the “failure of the chest and diaphragmatic movements” ^[1]
• During the second half of the 19th century, the clinical features of sleep apnea were thoroughly described:^[1]

• Airway obstructions
• Noisy snoring
• Nocturnal insomnia
• Excessive somnolence

• Medical literature describes early reports of those severely affected with sleep apnea with hypoxemia, hypercapnia, and congestive heart failure (CHF)
• Prior to its characterization as a unique disorder, sleep apnea was often diagnosed as either narcolepsy, insomnia, or skepticism^[1]

• In 1981, Colin Sullivan and associates in Sydney improved the management of obstructive sleep apnea with continuous positive airway pressure (CPAP) ^[2]
• By the late 1980s, CPAP was transformed from the bulky and noisy first models and became widely used, which lead to specialized clinics for diagnosis and treatment

• April 18th is Sleep Apnea Awareness Day in recognition of Colin Sullivan (Australian physician, professor, and inventor)
• Before sleep apnea was recognized as a separate sleep disorder, it was viewed as either a type of insomnia or an age-related phenomenon^[3]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Saarah T. Alkhairy, M.D.

There are three types of sleep apnea: obstructive, central, and mixed. The majority of patients have obstructive sleep apnea (OSA). Individuals of untreated sleep apnea stop breathing repeatedly during the night usually for a minute or longer, during their sleep. Most of the time, these individuals are unaware of these episodes because the episodes don’t trigger an awakening. Obstructive sleep apnea results from the narrowing or total blockage of the airway. In central sleep apnea, there is failure of the central nervous system to send appropriate signals to the muscles of respiration. These signals control the individual’s breathing. It is also possible for an individual to have a combination of these two types, referred to as mixed apnea.

Sleep apnea can be classified into three categories:

• The majority of the three forms
• It results from either the narrowing or total blockage of the respiratory airway which occurs when the soft tissue at the back of the throat collapses during sleep
• OSA may be classified into three classes based on the severity of the disease^[1]:

• The severity of the disease is assessed by the Apnea Hypopnea index (AHI), which combines apneas and hypopneas
• Apneas are defined as breathing pauses lasting 10 seconds
• Hypopneas are defined as events lasting 10 seconds in which there is continued breathing but ventilation is reduced by at least 50% from the previous baseline during sleep

• None/Minimal OSA: AHI < 5
• Mild OSA: AHI = 5-14: Patients may either be asymptomatic or may complain of sleepiness when they are sedentary. The daytime sleepiness often does not impair the patients’ quality of life.
• Moderate OSA: AHI = 15-29: Patients are usually symptomatic.
• Severe OSA: AHI ≥ 30: Patients’ symptoms are severe enough to interfere with daily activities. They may fall asleep during activities that require attention (e.g. driving)

• The brain is unable to send appropriate signals to the muscles that control breathing due to the instability of the respiratory center
• It is referred to as idiopathic central sleep apnea when an underlying etiology cannot be identified
• Cheyne-Stokes breathing is a subtype of breathing in central sleep apnea, which is defined as periodic breathing with recurrent episodes of apnea that alternate with episodes of rapid breathing

• In Cheyne-Stokes breathing, apnea episodes occur during sleep and during wakefulness

• Some individuals may have a combination of both types of sleep apnea
• Complex sleep apnea (CompSA), also called treatment-emergent central sleep apnea, is the emergence of central apneas during the administration of continuous positive airway pressure (CPAP) or bilevel positive airway pressure (BiPAP) treatment

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Saarah T. Alkhairy, M.D.

Sleep apnea may be commonly caused by a large neck/abodminal circumference (e.g. obese individuals), administration of medications, diseases that narrow the respiratory airways (e.g. enlarged adenoids, enlarged tonsils), diseases that affect the central nervous system (e.g. cerebrovascular accident, spinal cord injury), or infectious diseases (e.g. polio).

Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.

• Cerebrovascular accident
• Obesity hypoventilation syndrome
• Opioid overdose
• Post-polio syndrome
• Postoperative complication
• Spinal cord injury

• Common cold
• Diabetic neuropathy
• Enlarged adenoids
• Enlarged tonsils
• Hypothyroidism
• Obesity
• Opioid overdose
• Postoperative complication
• Sinusitis
• Tonsilitis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Saarah T. Alkhairy, M.D.

Sleep apnea must be differentiated from other diseases that cause loud snoring, fatigue, choking, coughing, and daytime sleepiness. To differentiate obstructive sleep apnea (OSA) and central sleep apnea, a polysomnogram should be performed. OSA will demonstrate evidence of thoracoabdominal effort, whereas central sleep apnea will not.

The table below summarizes the findings that differentiate sleep apnea from other conditions that cause loud snoring, fatigue, choking, coughing, and/or somnolence.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Saarah T. Alkhairy, M.D.

The true prevalence of sleep apnea is difficult to estimate because mild cases may remain undiagnosed, and the majority of patients only present following the development of clinical manifestations. Sleep apnea is a chronic disorder, and clinical manifestations often develop as the disease progresses. Accordingly, elderly patients are more commonly diagnosed with sleep apnea than younger adults. Male gender and African American race are associated with higher prevalence of sleep apnea compared with female gender and other ethnicities.

• The true prevalence of sleep apnea is difficult to estimate because mild cases may remain undiagnosed, and the majority of patients only present following the development of clinical manifestations.

• In the general population, sleep apnea prevalence is estimated to range from 3,000 to 7,000 per 100,000 individuals^[1]

• Sleep apnea is a chronic disorder, and clinical manifestations often develop as the disease progresses. Accordingly, elderly patients are more commonly diagnosed with sleep apnea than younger adults.
• Compared with younger adults, the prevalence of sleep apnea is 2 to 3 greater among individuals older than 60-65 years of age^[2]

• Sleep apnea is more common among males
• The male:female ratio ranges between 2:1 to 3:1^[3]
• The prevalence of sleep apnea is approximately 3,000-7,000 per 100,000 for adult men and 2,000-5,000 per 100,000 for adult women^[4]
• The increased prevalence among males may be attributable to the larger neck circumference and a longer pharyngeal airway

• Compared with Caucasian and Asian race, African-American race is associated with a 2-3 fold increased risk of obstructive sleep apnea^[5]

• Sleep apnea due to craniofacial factors is more frequently observed among Chinese patients than among Caucasians.^[6]

• The predilection of central sleep apnea based on race is unknown.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Saarah T. Alkhairy, M.D.

The most common risk factor for the development of sleep apnea is large neck circumference. Other risk factors of sleep apnea include smoking, alcohol, sedatives, tranquilizers, males, a positive family history, certain ethnic backgrounds such as African Americans, and individuals over 60-65 years. Continuous positive airway pressure (CPAP) is a risk factor for complex sleep apnea (also known as mixed sleep apnea).

The table below lists the risk factors for sleep apnea:

• Obesity^[1]

• Obesity is the most common risk factor for OSA

• Pregnancy

• Diabetes^[2]

• Polycystic ovary syndrome

• Hypertension^[2]

• Facial deformities

• Hypothyroidism

• Esophageal reflux

• Enlarged tonsils or adenoids

• Chronic respiratory tract conditions such as:

• Asthma

• Allergies

• Chronic bronchitis

• Chronic obstructive pulmonary disease

• Bulbar poliomyelitis

• Encephalitis

• Neurodegenerative diseases

• Stroke

• Problems after cervical spine surgery

• Primary hypoventilation syndrome

• Brain tumors
• Down syndrome

Prolonged continuous positive airway pressure (CPAP) is a risk factor for complex sleep apnea (also known as mixed sleep apnea) because patients with obstructive sleep apnea may develop central sleep apnea.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Saarah T. Alkhairy, M.D.

Clinical practice guidelines by the United States Preventive Services Task Force^[1] address screening and do not recommend screening.

However, commercial drivers, operators of heavy equipment, pilots, and other occupations at risk of diurnal sleepiness should be screened by history and physical exam using standardizes questionnaires.

• Commercial drivers, operators of heavy equipment, pilots, and other populations at risk from diurnal sleepiness should with be screened with a history and physical exam

• If OSA is suspected, a sleep study should be performed

• For patients with obstructive sleep apnea, screening questionnaires may be useful for preoperative and high risk patients

• Asks about the presence of loud snoring, apneas, excessive daytime sleepiness, and hypertension
• STOP BANG questionnaire combines the STOP questionnaire questions and adds BMI age, and neck circumference (increased sensitivity but decreased specificity compared to STOP questionnaire)
• A score of three or higher has a sensitivity and specificity of 84 and 56 percent for the diagnosis of OSA using an AHI threshold of >5 events per hour, and a sensitivity and specificity of 93 and 43 percent for an AHI >15 ^[2]
• To view the STOP BANG questionnaire, click here

• A four-item questionnaire that incorporates neck circumference, hypertension, habitual snoring, and nocturnal gasping or choking to generate a score ranging from 0 to 100
• Scores greater than 15 result in a probability of OSA (defined as an AHI >10 events per hour) of 25 to 50 percent^[3]

• The Berlin questionnaire consists of 10 items relating to snoring, nonrestorative sleep, sleepiness while driving, apneas during sleep, hypertension and BMI
• The results categorize patients as having a high or low risk for OSA
• A high risk score is associated with a sensitivity and specificity of 80 and 46 percent when OSA is defined as an AHI ≥5 events per hour, and 91 and 37 percent when OSA is defined as an AHI ≥15 events per hour^[4]
• To view the Berlin questionnaire, click here

There are no current screening guidelines for central sleep apnea.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Saarah T. Alkhairy, M.D.

Sleep apnea can begin with loud snoring and eventually lead to serious complications. Common symptoms include somnolence, depression, and headaches. More serious complications include cardiovascular diseases, stroke, and hypertension. If sleep apnea is adequately treated, the prognosis is very good. If it is left untreated, patients can develop serious complications and have a poor prognosis.

• Sleep apnea is a progressive disease. Snoring is the earliest manifestation of sleep apnea.^[1]
• Snoring in sleep apnea is often mild at first, but it often progresses as the disease becomes more severe.

• Sleep apnea with heavy snoring is associated with prolonged apneas, followed by choking and gasping^[1]
• As a result, patients develop daytime clinical manifestations, namely somnolence, depression, headaches, and impotence
• If left untreated, sleep apnea may be associated with the development of serious complications, such as hypertension, coronary artery disease, stroke, CHF, and atrial fibrillation

Untreated sleep apnea is associated with the development of the following complications:

• Depression
• Hypertension
• Coronary artery disease
• Stroke
• CHF
• Atrial fibrillation
• Failure to thrive among small children

• If adequately treated, the prognosis of sleep apnea is generally very good
• Sleep apnea during surgery and anesthesia is associated with poor prognosis
• Opioid-induced central sleep apnea is associated with poor prognosis^[2]

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