Sleep Care

Complex Sleep Apnea

When the term “sleep apnea” is used, it is often referring to “obstructive sleep apnea” (OSA), a condition in which the airway collapses during sleep as the muscles and tissues relax. With the airway closed off, a person stops breathing and their oxygen levels typically start dropping until an arousal is triggered to resume normal breathing. While this is occurring, most people continue to breathe—although often a little more shallowly—from their chest and abdomen.

However, there is a second kind of sleep apnea—called “central sleep apnea” (CSA)—in which a person completely stops breathing: the airway is collapsed, and there is no breathing effort in the chest and abdomen. While it is a rare condition in the general pool of people suffering from sleep apnea, some risk factors have been identified: male, aged 65 years or older, and most significantly, a history of systolic heart failure. Central sleep apnea also tends to be more present at high altitudes due to greater carbon dioxide sensitivities.

Complex Sleep Apnea

When treating obstructive sleep apnea, the first line of treatment is often a Continuous Positive Airway Pressure (CPAP) titration, which is usually done in a sleep lab. During the night a sleep technician tests different air pressures to see which pressure adequately keeps the patient’s airway open in different stages of sleep and positions.

While the titration process often goes smoothly, some patients will exhibit an increase in central sleep apnea in response to different CPAP pressures. This condition is called “complex sleep apnea”. Clinical profiles for those likely to have complex sleep apnea are in between those for obstructive and central sleep apnea, although a history of heart failure is often present. It’s suspected that for patients with systolic heart failure, roughly 40-50% has complex sleep apnea. As a more general measure, in a study of over 1200 patients using CPAP following a diagnosis of OSA, 6.5% were found to have complex sleep apnea following initial CPAP use.

Auto SV: A Dynamic Treatment Approach

Since complex sleep apnea doesn’t show up until the application of CPAP, treating it can be difficult. Fortunately, advances in technology and the field of sleep medicine have produced Auto Servo-Ventilation (Auto SV), a mode of pressure support that patients with complex sleep apnea typically respond well to.

In a traditional CPAP set-up, a single pressure is delivered at a constant rate in an attempt to keep the airway open. For patients who have difficulty breathing with just the one pressure, a bilevel (BiPAP) mode can be used that uses a higher pressure when a person inhales, and a lower pressure when a person exhales. Because this set-up more closely mimics a person’s natural breathing, patients with hypoventilation or other breathing difficulties typically find it easier to use.

If complex sleep apnea emerges when using either CPAP or BiPAP, Auto SV is the next step. Rather than just one or two pressures, Auto SV uses a range of pressures that can change dynamically while a person’s asleep to ensure the air pressure is adequate without being too high or low. For example, rather than a constant CPAP pressure of 8 cm H2O, or a BIPAP pressure of 12/8 cm H2O (indicating an inhale pressure of 12 cm and an exhale pressure of 8 cm), an Auto SV could be programmed to 22/12/8 cm H2O, which would allow the machine to deliver a pressure anywhere from 12 to 22 cm during inhaling as needed, and a pressure of 8 cm when exhaling.

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The range in pressures allows the machine to respond to changes in a person’s breathing that can occur during the night, particularly when they are associated with other health conditions, such as heart failure.

In addition to being significantly more effective in treating complex sleep apnea than CPAP or BiPAP, studies evaluating Auto SV have found that in follow-up with patients, more than 80% were still using it successfully on a long-term basis and more than 70% found it improved their sleep quality and daytime sleepiness problems.


Gay, P.C. Journal of Clinical Sleep Medicine, 2008: vol. 4 (5): pp. 403-405

Javaheri, S. Journal of Clinical Sleep Medicine, 2009: vol. 5 (3): pp. 205-211

Morgenthaler, T.I. Sleep, 2006: vol. 29 (9): pp. 1203-1209



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