Sleep apnea is a disorder defined as a pause of breathing while asleep. There are three types of sleep apnea.
• Obstructive Sleep Apnea (OSA) is the most common. This type of sleep apnea is caused by an obstruction which stops the flow of air to the nose and mouth.
• Central Sleep Apnea (CSA). This type of sleep apnea involves the region of the brain and nerves that regulate breathing do not function properly which causes breathing to be impaired.
• Mixed Sleep Apnea is not uncommon. The type of sleep apnea is a combination of Obstructive Sleep Apnea and Central Sleep Apnea. Each pause in the breathing while sleeping is called an apnea.
Central sleep apnea is when you repeatedly stop breathing during sleep because the brain temporarily stops sending signals to the muscles that control breathing.
People with CSA seldom snore.
Causes of CSA
Central sleep apnea often occurs in people who have certain medical conditions. For example, it can develop in persons who have life-threatening problems with the brainstem. The brainstem controls breathing. As a result, any disease or injury affecting this area may result in problems with normal breathing during sleep or when awake.
Conditions that can cause or lead to central sleep apnea include:
• Bulbar poliomyelitis
• Complications of cervical spine surgery
• Encephalitis affecting the brainstem
• Neurodegenerative illnesses such as Parkinson’s disease
• Radiation of the cervical spine
• Severe arthritis and degenerative changes in the cervical spine or the base of the skull
• Severe obesity
• Stroke affecting the brainstem
• Primary hypoventilation syndrome
• Use of certain medications such as narcotic-containing painkillers
Central sleep apnea due to a medical condition: The patient has a history of an underlying disorder other than heart failure or renal failure. Patients with stroke can have either classic CSB-CSA or central apneas without a crescendo-decrescendo pattern.
• Diabetes mellitus
• Parkinson disease
• Multiple system atrophy or Shy-Dragger syndrome
• Familial dysautonomia
• Postpolio syndrome
• Damage to medullary respiratory centers by tumor, infarction, or infection
• Arnold-Chiari malformation types I-III
• Cervical cordotomy
• Muscular dystrophy
• Myasthenia gravis
• Prader-Willi syndrome
• Idiopathic cardiomyopathy
• One form of central sleep apnea commonly occurs in people with congestive heart failure. Idiopathic central sleep apnea refers to apnea that is not associated with another disease.
Central sleep apnea is not the same as obstructive sleep apnea, which is due to a blockage in the airway.
Symptoms of CSA
Persons with central sleep apnea have episodes of disrupted breathing during sleep.
Other symptoms may include:
• Chronic fatigue
• Daytime sleepiness
• Morning headaches
• Restless sleep
Other symptoms may occur if the apnea is due to a neurological condition. Symptoms depend on the underlying disease and what parts of the nervous system it has affected, but may include:
• Difficulty swallowing
• Voice changes
• Weakness or numbness throughout the body
The health care provider will perform a physical exam. Tests will be done to diagnose an underlying medical condition. A sleep study (Polysomnogram-PSG) can confirm sleep apnea.
Other tests that may be done include:
• Lung function studies
• Thyroid function tests
• Kidney Function Tests
• Blood tests to rule our Muscular dystrophy, Myasthenia gravis etc.-CPK, Choline esterase
• Cardiologic evaluation
• MRI imaging study finding are also nonspecific and are characteristic of the underlying cause rather than helpful in diagnosing a specific central sleep apnea syndrome. Patients with stroke, CNS tumor, and Arnold-Chiari malformation may have characteristic findings on brain CT scan or MRI examination.
• Polysomnography (PSG) which is conducted by sleep specialist at a sleep clinic. The PSG monitors the brain waves, eye movement, muscle activity, and heart rhythm of the patient. A patient is said to have sleep apnea if the PSG test defines five or more episodes of apnea (pause in breathing) per hour. A couple of other tests are also useful in the diagnosis of sleep apnea. Oximetry screening can also be conducted. This is a screening method that monitors and records an individual’s blood oxygen level during sleep. Portable cardio respiratory testing is also an option. This is a test that is conducted at home to diagnosis sleep apnea.
Treatment of CSA
Up to 20% of central sleep apnea cases have been suggested to resolve spontaneously. If the patient is not symptomatic, observation may be the only appropriate step.
Several different treatments aimed at central sleep apnea include positive airway pressure, adaptive servo ventilation (ASV), oxygen, added dead space, carbon dioxide inhalation, and overdrive atrial pacing.
Oxygen, nasal CPAP, or bi-level positive airway pressure (Bi PAP) may be used for some types of central sleep apnea. Continuous positive airway pressure (CPAP) and bi-level positive airway pressure (BIPAP), especially with back-up rate, are other options, although adherence remains a problem. Adaptive servo ventilation (ASV) holds promise but has its own limitations.
Some types of central sleep apnea are treated with drugs that stimulate breathing.
Patients should avoid the use of any sedative medications.
If central sleep apnea is due to heart failure, the goal is to treat the heart failure itself.
Adaptive servo ventilation: ASV represents a relatively novel way of approaching treatment for central sleep apnea, especially CSB-CSA.
Medications for CSA
Due to the heterogeneity of the central sleep apnea syndromes, different medications have been used under different circumstances. No single medication can be considered a drug of choice. Several different medications aimed at improving central sleep apnea include acetazolamide, theophylline, and sedative-hypnotic agents.
• Acetazolamide (Diamox): Acetazolamide is a carbonic anhydrase inhibitor that causes bicarbaturia and metabolic acidosis, which presumably shifts the apneic threshold of PaCO2 to a lower level. It has been shown to be effective therapy in primary central sleep apnea and CSB in patients with heart failure and in the treatment of high-altitude periodic breathing.
• Theophylline: This agent has been studied in patients with heart failure and was found to be effective in attenuating CSB. It may also be effective for high-altitude periodic breathing.
• Sedative hypnotics: These agents have been used successfully in treating nonhypercapnic central sleep apnea. Temazepam and Zolpidem have been shown to be effective under these circumstances and are believed to work by consolidating the sleep pattern, thus minimizing the instability in ventilation induced by sleep-wake transitions. A case series showed Zolpidem reduced central apneas, and the overall apnea-hypopnea index, without worsening obstructive events.
Complex sleep apnea
Central sleep apnea may emerge during titration of CPAP in patients previously diagnosed with obstructive sleep apnea. This syndrome, termed complex sleep apnea, has become a controversial topic in the sleep literature and has been raised as a possible type of difficult-to-treat obstructive sleep apnea. As many as 6.5% of patients with obstructive sleep apnea may develop emergent or persistent central sleep apnea with CPAP treatment. CPAP emergent central sleep apnea is generally transitory and is eliminated after 8 weeks of CPAP therapy. Persistent CPAP-related central sleep apnea has been observed in approximately 1.5% of treated patients. Similarly, complex sleep apnea can occur following a Tracheostomy for obstructive sleep apnea. Central apneas have been found initially after a Tracheostomy, but after an extended period, central sleep apnea decreased on repeat PSG.
Depression and sleep apnea
Approximately one in five people who suffer from depression also suffer from sleep apnea, and people with sleep apnea are five times more likely to become depressed. Existing depression may also be worsened by sleep apnea. While it is not clear whether the apnea causes the depression or vice-versa, studies show that by treating sleep apnea symptoms, depression may be alleviated in some people.