Sleep apnea: Clinical sciences

Sleep apnea is a condition characterized by episodes of either the reduction or cessation of inspiratory airflow during sleep, commonly resulting in recurrent nighttime hypoxemia. Untreated sleep apnea over time may lead to the development of complications, such as hypertension, heart disease, atrial fibrillation, stroke, diabetes, and sudden death.

Sleep apnea can be classified as obstructive sleep apnea or OSA, and central sleep apnea or CSA.

In OSA, respiratory effort is present but apnea occurs due to collapse of the patient’s upper airway, which is especially common in obesity, conditions associated with oropharyngeal crowding, and nasal allergies.

On the other hand, in CSA, apneic episodes occur due to a lack of spontaneous respiratory effort, associated with alterations in central respiratory drive. This is typically seen in patients with heart failure, neurologic diseases, and sedating medications.

Finally, if no underlying condition is associated with central sleep apnea, we are talking about primary, or idiopathic central sleep apnea.

If your patient presents with a chief concern suggesting sleep apnea, the first step is to obtain a focused history and physical exam. Your patient may report either excessive daytime sleepiness or fatigue.

They may also report loud snoring and morning headaches, as well as nighttime breathing disturbances, such as frequent awakenings, pauses in breathing, choking, or gasping. Also, history findings might include some underlying chronic conditions, like hypertension, or heart failure.

On the flip side, physical examination typically reveals a neck circumference of greater than 16 inches in biologically female individuals and 17 inches in biologically male individuals. Other important physical exam findings include central obesity and enlarged oropharyngeal structures, such as the tonsils, uvula, or tongue.

If your patient presents with these signs and symptoms, you should suspect sleep apnea, so your next step is to order polysomnography, or PSG for short. Polysomnography, also known as a sleep study, measures a patient’s stages of sleep; oxygen saturation; respiratory effort; and the apnea-hypopnea index, or AHI for short, which is the average number of apneas plus hypopneas per hour of sleep.

Now, apnea is defined as the absence of airflow for at least 10 seconds; while hypopnea refers to an airflow reduction greater than or equal to 50% that’s associated with at least a 4% reduction in oxygen saturation.

Now, here’s a clinical pearl to keep in mind! Instead of a traditional overnight stay in a sleep laboratory, the patient can also go with home sleep apnea testing, or HSAT. However, if the home test is negative and your suspicion is still high, you should obtain formal sleep testing in a sleep laboratory.

If the apnea-hypopnea index is less than 5, you can rule out sleep apnea and consider an alternative diagnosis.

On the flip side, if the polysomnography reveals an apnea-hypopnea index of 5 or greater; fewer than 5 central apneic episodes per hour; and less than half of the apneic episodes are central in origin, diagnose obstructive sleep apnea.

Now, once you diagnose obstructive sleep apnea, your next step is to assess the underlying cause. If your patient has a body mass index greater than 30, diagnose obstructive sleep apnea due to obesity. But, even though the most common body mass index in patients with obstructive sleep apnea is greater than 30, this condition can also be seen in individuals with body mass indexes of 18 to 25. Now, the treatment is primarily based on continuous positive airway pressure, or CPAP for short. Continuous positive airway pressure devices consist of a tight-fitting facemask attached to a portable, programmable machine by a flexible plastic hose. The positive pressure administered during both inspiration and expiration prevents the collapse of the oropharyngeal airway, resulting in a decrease in apneic and hypopneic events. In addition to CPAP, don’t forget to encourage lifestyle modifications, primarily weight loss, but also smoking cessation, and avoiding alcohol 4 to 6 hours before bedtime. Finally, you can consult the surgery team for bariatric surgery as well!