What is the difference between central sleep apnea and obstructive sleep apnea?
In this lesson, we explain the differences between central sleep apnea and obstructive sleep apnea, symptoms, diagnosis, treatment, and obesity hypoventilation syndrome. Sleep apnea is defined as a disorder of breathing in which you stop breathing for >10 seconds, at least 5x an hour during sleep. There are two main types of sleep apnea: central sleep apnea and obstructive sleep apnea.
Sleep Apnea: >10 seconds cessation of breathing during sleep . This causes disruption of sleep. Patients with sleep apnea (both obstructive and central sleep apnea) present with daytime somnolence, which means they are often sleepy in the morning.
Hypoxia means low oxygen in your blood. This causes your kidneys to release EPO to produce more new red blood cells. Erythropoiesis is increased. Some patients with sleep apnea have high hematocrit levels.
During the day: Normal PaO2
At night: Hypoxia (Low PaO2)
Common symptoms of Sleep Apnea: Pulmonary hypertension, atrial fibrillation, sudden death
Differences in Causes of Obstructive Sleep Apnea vs Central Sleep APnea
Obstructive sleep apnea is usually caused by an organ structure or tissues physically obstructing the airway. This is generally soft tissue collapse in the pharynx. In adults, this may be excess parapharyngeal tissue, or in children, adenotonsillar hypertrophy. The tissue are constricted and leads to the tongue falling back too.
Central sleep apnea is caused by CNS injury/toxicity, Heart failure, or overdose/side effects of opioids.
Differences of Associated Disease/Symptoms: Obstructive Sleep Apnea vs Central Sleep Apnea.
Obstructive sleep apnea is associated with obesity, daytime sleepiness, and loud snoring.
Central Sleep apnea is associated with Cheynes-Stokes respiration.
Diagnosis of Central Sleep Apnea and Obstructive Sleep Apnea
Sleep apnea in general is diagnosed through a sleep study or polysomonography. Measuring sleep cycle, sleep apnea moments, your eye movements, O2 level, Heart rate, respiratory rate.
In central sleep apnea, there is also an association with Cheyne-Stokes respiration or cyclic breathing. In Cheyne-Stokes, there are oscillations between apnea and hyperpnea because the patient’s body has delayed detection or response to changes in PaCO2. This causes the patient to breathe rapidly (hyperventilate) –> causes carbon dioxide in blood levels to drop too fast –> brain responds by stop breathing which causes apnea –> but then carbon dioxide in blood levels rise too fast –> triggers brain to restart breathing fast (hyperpnea) (hyperventilate) –> PaCO2 becomes low again–> and so on the cycle repeats.
Cycles of Cheyne-stokes respiration can last from 30 seconds to 2 minutes.
Can Cheyne-Stokes breathing occur while awake?
Yes, Cheyne-stokes breathing can occur when awake or during sleep for central sleep apnea patients. It is more common to occur during sleep.
Mnemonic for Central Sleep Apnea
CCC= CENTRAL SLEEP APNEA
C= congestive heart failure
Differences in Treatment: Obstructive Sleep Apnea vs Central Sleep Apnea
Obstructive sleep apnea treatment is weight loss, CPAP (positive airway pressure), and surgery if needed to remove the excess tissue obstructing airway.
Central sleep apnea treatment is usually just positive airway pressure.
What is obesity hypoventilation syndrome for sleep apnea?
An easy way to understand what obesity hypoventilation syndrome is to break down the meaning of its words. Obesity –> patients with this syndrome are obese with a BMI greater than or equal to 30 kg/m^2. These patients have trouble breathing deeply enough, so they hypoventilate. During hypoventilation, PaCO2 increases, while PaO2 decreases. In other words, oxygen blood levels are low, and carbon dioxide levels in blood are high.
When awake: PaCO2 increases
When asleep: PaCO2 is still high, increases but PaO2 is low
Obesity hypoventilation syndrome is also known as Pickwickian syndrome. How is obesity hypoventilation syndrome related to sleep apnea? Patients with obesity hypoventilation syndrome have problems breathing not only while awake but also while asleep. Sleep apnea is a symptom of OHS or Pickwickian syndrome. Please note that not all patients with sleep apnea have obesity hypoventilation syndrome. However, obesity is the strongest risk factor for obstructive sleep apnea.
USMLE Test your knowledge: Sleep Apnea Practice Questions
- Cheynes Stokes Breathing in which type of Sleep Apnea fails to detect what changes?
A. Obstructive sleep apnea, PaCO2
B. Central sleep apnea, PaCO2
C. Obstructive sleep apnea, PaO2
D. Central sleep apnea, PaO2
Answer: B. Central sleep apnea, PaCO2
2. Patients with sleep apnea can experience which one systemically:
Hypertension or Hypotension
3. What do you see in the Cheynes-Stoke respiration when pCO2 is high and what type of sleep apnea is associated with this?
A. Hyperventilation, Obstructive sleep apnea
B. Hypoventilation, Obesity hypoventilation apnea
C. Hypoventilation, Central sleep apnea
D. Hyperventilation, Central sleep apnea
Answer: D. Hyperventilation, Central sleep apnea
4. Which disease is known for normal PaO2 in daytime (awake), but which disease is known for high PaCO2 in daytime?
A. Obesity hypoventilation syndrome, Sleep Apnea
B. Obstructive Sleep Apnea, Central Sleep Apnea
C. Sleep Apnea, Obesity hypoventilation syndrome
D. Central Sleep Apnea, Obstructive Sleep Apnea
E. None of the above
Answer: C. Sleep Apnea, Obesity Hypoventilation syndrome
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