Sleep apnea: Clinical sciences

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Introduction0:00–1:24

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.

Stable Patient1:24–2:21

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.

Suspect sleep apnea2:21–3:26

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.

Alternative diagnosis/Obstructive sleep apnea3:26–3:52

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.

Obstructive sleep apnea due to obesity3:52–5:03

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!On the other hand, if your physical examination reveals enlarged tonsils, uvula, or tongue, diagnose obstructive sleep apnea due to oropharyngeal crowding.

Obstructive sleep apnea due to oropharyngeal crowding5:03–5:24

Again, start CPAP and consider consulting your surgery team for possible uvulopalatoplasty or tonsillectomy. Let’s go back one last time!

Obstructive sleep apnea due to nasal allergies5:24–6:26

If your patient reports nasal congestion and sneezing, and their physical examination reveals red, swollen nasal mucosa, or even nasal polyps, diagnose obstructive sleep apnea due to nasal allergies.
Treatment again includes CPAP, but also allergy management! Now, here’s a clinical pearl to keep in mind!
While sleep apnea and narcolepsy can both cause excessive daytime sleepiness, you can differentiate them using history findings and polysomnography results.
In addition to excessive daytime sleepiness, patients with narcolepsy can have hallucinations; sleep paralysis; and cataplexy, which is a condition characterized by episodes of daytime muscle weakness that are typically preceded by intense emotions, such as fear or excitement.
Additionally, polysomnography can show abnormal sleep cycles, but will not show a significant number of apneic episodes.Now let’s go back to polysomnography.
If polysomnography reveals the apnea-hypopnea index of 5 or greater; 5 or more central apneic episodes per hour; and more than half of the apneic episodes are central in origin, diagnose central sleep apnea.

Central sleep apnea6:26–6:48

Alright, once you diagnose central sleep apnea, your next step is to assess the underlying cause. Sometimes your patient will have a history of heart failure or neurologic disease, such as a prior stroke; and a physical exam will reveal Cheyne Stokes breathing, which is when respirations cycle between apnea and breathing that becomes progressively deep and rapid.In this case, diagnose central sleep apnea due to an underlying medical condition, such as heart failure or neurologic disease.

Central sleep apnea due to an underlying condition6:48–8:06

Next, treat the underlying cause and put the patient on CPAP because, in conditions associated with chronic hypoxia, like heart failure, individuals tend to hyperventilate, which drives down their pCO2.
These lower pCO2 levels are inadequate to stimulate the respiratory center, resulting in episodes of apnea. In this scenario, CPAP creates adequate pressures to maintain airway patency, even in the absence of spontaneous respiratory efforts, but, at the same time, it supplements oxygen to improve the baseline hypoxia.
Finally, supplemental nighttime oxygen may also be helpful in some patients who have significant oxygen desaturation during apneic episodes.Okay, let’s assess for another cause.

Medication-induced Central Sleep Apnea8:06–9:16

If your patient has a history of using medications known to cause central respiratory depression, such as opioids or benzodiazepines, diagnose medication-induced central sleep apnea.
Treatment consists of reducing the dose of the causative medication or prescribing an alternative, if possible; and starting CPAP.
Again, you can consider supplemental nighttime oxygen!Now, here’s another clinical pearl! Some patients may refuse CPAP therapy, not tolerate it well, or fail to improve despite strict adherence.
For these individuals, you can consider alternative treatment options, such as oral appliances, like mandibular advancement and tongue retaining devices.
In some cases, implantable nerve stimulators can be used to target the phrenic nerve, stimulating diaphragm contraction to induce respiration in patients with central sleep apnea.
Similarly, the implantable nerve stimulator can stimulate the hypoglossal nerve and contraction of oropharyngeal muscles, thereby creating a larger airway in patients with obstructive sleep apnea.Okay, let’s go back one last time!

Primary (Idiopathic) Central Sleep Apnea9:16–10:24

If history reveals no underlying medical condition and there are no medications associated with central respiratory depression, diagnose primary or idiopathic central sleep apnea.
In this case, treatment primarily consists of CPAP, but you can also consider supplemental nighttime oxygen and respiratory stimulants, like acetazolamide.
Acetazolamide is a carbonic anhydrase inhibitor that lowers blood pH, subsequently triggering the respiratory center to increase respiratory drive, potentially decreasing the number of central apneic episodes.
Here’s one last high-yield fact! It is possible for individuals to have both central and obstructive sleep apnea.
For example, a patient with heart failure may have central sleep apnea due to resting hypoxia, as well as obstructive sleep apnea due to obesity.
In this case, treatment involves CPAP to address both types of sleep apnea, while optimizing control of the underlying heart failure and encouraging weight loss.Alright, as a quick recap… If you suspect sleep apnea, your first step is to order polysomnography.

Review10:24–11:27

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.
The most important causes include obesity, oropharyngeal crowding, and nasal allergies. On the other hand, if the polysomnography reveals the apnea-hypopnea index of 5 or greater; 5 or more central apneic episodes per hour; and more than half of the apneic episodes are central in origin, diagnose central sleep apnea.
The most important causes include chronic conditions like congestive heart failure, as well as sedative medications. If no underlying condition is identified, you are dealing with primary, or idiopathic central sleep apnea.
In all cases, the management primarily relies on continuous positive airway pressure, or CPAP! the primary relies on continuous positive airway
Sleep apnea: Clinical Sciences: Video and Causes | Osmosis