Cheyne Stokes respiration (CSR) has not been widely studied as sleep apnea, although there is a strong relationship between them.
Heart failure patients can be awakened just as they are falling asleep by a Cheyne-Stokes respiration, a form of central sleep apnea in which a series of increasingly deep breaths is followed by a brief cessation of breathing.
Cheyne Stokes respiration, also known as agonal respiration, is an unique breathing pattern usually characterized by three phases:
In this video you'll see a live demonstration of agonal respiration:
In the fourth century b.c., regarding a very ill person with fever,sweats, and black urine, Hippocrates described a pattern of breathing in which "the respiration throughout was like that of a man correcting himself, and rare and large."
Presumably he had observed Cheyne-Stokes breathing, which was described more graphically by William Stokes two millennia later (in 1854) as follows:
The symptom in question (previously described by Dr.Cheyne) consists in the occurrence of a series of inspirating, increasing to a maximum, and then declining in force and length, until a state of apparent apnea is established.
In this condition the patient may remain for such a length of time as to make his attendants believe that he is dead, when a low inspiration, followed by one more decided, marks the commencement of a new ascending and descending series of inspirations.
Hypoxia - this may be due to low arterial partial pressure of oxygen (PO2) in patient's blood. The partial pressure should be over 90%, but the most healthy adults show a value over 95%.
This type of agonal respiration occurs in NREM sleep which becomes fragmented because of frequent arousals. The duration of stages 3 and 4 NREM sleep is also reduced.
Reduction in lung volumes - this reduces the body stores of oxygen and makes hypoxia more marked during any transient apnea.
Cardiac problems - patients with heart problems, and especially with severe heart failure, have consistently been found to have highly fragmented sleep, with frequent arousals and sleep changes.
A recent study has shown that at least 21% of patients with congestive heart failure complained of excessive daytime somnolence and 48% of patients complained of being awake more than 30 minutes during the course of the night.
Additionally, studies indicate that 30% to 60% of patients with heart failure suffer from sleep breathing disorders, including Cheyne Stokes respiration with central sleep apnea.
Cerebral cortical dysfunction - agonal respiration is common in disorders of the cerebral hemispheres which reduce the inhibition of the respiratory centers so that reflex responses become accentuated.
This may be the reason for an increased prevalence of agonal respiration in the elderly.
A patient with CSR have frequent arousals from sleep, especially in stages 1 and 2 NREM sleep. These may be detected as awakenings and insomnia, and if they are sufficiently frequent may result in excessive daytime sleepiness.
These frequent arousals are associated with an increase in sympathetic activity during sleep. At this time, the patient can have a tachycardia, an increase in cardiac output, a rise in blood pressure and an increase in the cerebral blood flow.
If the patient's airway closes during agonal respiration, there may be snoring sounds usually when the upper airway closes towards the end of the apneic episode. This combination is also known as mixed sleep apnea.