Obstructive Sleep Apnea

Sleepy
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Diagnosis and reasoning

This middle aged man has presented with chronic fatigue and excessive daytime sleepiness, in conjunction with excessive snoring. Examination shows the presence of centripetal obesity, a significant neck circumference, and an elongated uvula which tends to obstruct the pharynx. When considered together, this constellation of clinical findings is strongly suggestive of obstructive sleep apnea (OSA); snoring is in particular a cardinal feature of the disease. However, it is important to appreciate that the snoring may just be a confounding symptom, and that this presentation might be due to another etiology - particularly hypothyroidism, or anemia. However, his full blood count is unremarkable, while a thyroid profile turns out to be normal. The definitive diagnosis of OSA requires demonstration of sleep-apneic episodes via polysomnography (PSA). Note that this is an expensive investigation with limited availability; thus the presence of daytime sleepiness should always be objectively demonstrated beforehand. The Epworth Sleepiness Scale is a good instrument in this regard; the patient is presented with 8 common day to day situations (watching TV, driving, etc) and asked to assign a score between 0 to 4, based on his or her probability of falling asleep during that situation. A score of 10 or more is considered sleepy, and a score over 18 very sleepy. Thus, this patient's score of 10 qualifies as objective evidence of daytime sleepiness; subsequently, PSA confirms the presence of multiple sleep-apneic episodes coinciding with the snoring, clinching the diagnosis. Note that the apnea-hypopnea index of 32 here indicates that severe sleep apnea is present. Patients with OSA are at risk of pulmonary hypertension and right heart failure; thus, a screening echocardiogram in this regard is essential, but is fortunately normal. Note also that he has features of metabolic syndrome such as obesity, an elevated waist circumference and hypertension - thus it is important to determine if diabetes or dyslipidemia is present, and manage him as appropriate. He should be encouraged to lose weight as this will result in lesser, lighter snoring and a diminished incidence of apnea and hypopnea during sleep Given the severity of the sleep apnea, continuous positive airway pressure (CPAP) therapy at night may also prove to be of benefit. Note that PSAs should be performed both before and after CPAP, to determine if objective improvement is present. Thyroxine therapy and a high protein diet are not indicated in his management.


Discussion

Obstructive sleep apnea (OSA) is a growing health concern, affecting up to 5% of middle aged men and women in the general population. The disease is linked to recurrent episodes of partial or complete pharyngeal collapse during sleep, resulting in increased effort of breathing, with diminished airflow. Important risk factors for OSA include obesity or excessive weight gain (fatty tissue in the throat tissue narrows and blocks the airway when the muscles relax), age (due to loss of muscle mass and tone in the upper airway), gender (men tend to have narrower airways than women), irregular sleep hours, anatomic abnormalities (such as nasal obstruction, enlarged tongue, elongated soft palate, large tonsils and adenoids), use of alcohol and sedatives (which relax the musculature), smoking (which causes inflammation and swelling of the upper airway), and severe gastroesophageal reflux disease. The four main symptoms of OSA are daytime sleepiness, frequent nocturnal microarousals, morning asthenia and severe snoring. Other known clinical features include motor incoordination and fatigability, irritability, morning headache, dryness in the mouth and pharynx, memory loss, sexual dysfunction and nocturnal symptoms such as apneas or pauses in breath, interruption of sleep or restless sleep, and somniloquy. Note that hypertension is known to be associated with OSA; it may also be a consequence of the disease. Polysomnography (PSA) is the gold standard for the diagnosis of sleep disorders; during this, the sleeping patient is observed for oxygen saturation, amount of oral and nasal airflow, degree of respiratory effort, electrocardiographic indices, body position, and overall body movement. PSA is usually performed in a sleep laboratory; or at times in the patient's home, where they are connected to monitors and observed in their natural sleep environment. Findings characteristic of PSA include episodes of desaturation coinciding with snoring and apnea, along with fragmentation of sleep, predominance of the superficial phases of sleep, and reduction of deep sleep and the REM phase. In addition, PSA allows calculation of the apnea-hypopnea index (AHI), via which OSA can be categorized as mild, moderate, or severe: - Mild: AHI of 5 to 14, oxygen saturation level of at least 86%, and minimal daytime disability. - Moderate: AHI of 15 to 30 or an oxygen saturation level of 80% to 85% and clinically significant dysfunction at work or socially because of daytime somnolence and loss of concentration - Severe: AHI of >30 or an oxygen saturation level of <7 9% and incapacitation caused by the sleep disorder. The treatment of OSA can range from relatively simple conservative measures to continuous positive airway pressure (CPAP) and surgery. Lifestyle and behavioral modifications should be recommended to all patients; these include better sleep hygiene; avoidance of caffeine and alcohol at night, and narcotics during the day; weight reduction; and sleeping on the side, propping the head up at night, or sewing a tennis ball into the back of the pajamas (to prevent the patient from rolling onto his or her back while sleeping). In patients with mild sleep apnea, dental appliances or oral mandibular advancement devices that prevent the tongue from blocking the throat and/or advance the lower jaw forward may be considered. Patients with moderate and severe sleep apnea should receive CPAP therapy; this requires the patient to wear a mask over the nose during sleep, and the pressure is adjusted to keep the airway open at night While CPAP is a highly effective modality of management, resulting in quick improvement, poor patient compliance is often an issue. Where CPAP therapy is not well tolerated by the patient surgical procedures such as uvulopalatopharyngoplasty, mandibular or maxillary advancement, nasal surgery, hyoid advancement, tongue advancement, or tongue base reduction may be considered. Tracheostomy should be reserved for patients with severe OSA in whom all other medical and surgical treatment modalities fail. Note that if left untreated, the sleep deprivation and lack of oxygen caused by OSA increase the risk of hypertension, ventricular dysfunction, pulmonary hypertension, arrhythmias, stroke and ischemic heart disease.


Take home messages

  1. The cardinal symptoms of OSA are daytime sleepiness, frequent nocturnal microarousals, morning asthenia, and severe snoring.
  2. The Epworth Sleepiness Scale is a useful tool for objectively quantifying the degree of sleepiness.
  3. Patients with OSA are at increased risk of cardiac and cerebrovascular sequelae and should be screened in this respect.
  4. Lifestyle and behavioural modifications are effective in many patients; severe cases may require nocturnal CPAP therapy.

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