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Complex or Treatment-Emergent Central Sleep Apnea Overview

Sleep apnea can be complex to understand. You might hear a lot of complicated words for the first time. You wonder what they mean. You feel lost and frustrated.

What is complex or treatment-emergent sleep apnea?

We’ll try to answer this for you as simply as possible.


Complex sleep apnea and treatment-emergent central sleep apnea are the same condition.

First, you need to know what obstructive sleep apnea is.

Obstructive sleep apnea happens when the upper airway or throat collapses when someone is asleep. It can trigger drops in the blood’s oxygen levels and it can cause the person to wake up during sleep. If the person experiences five or more obstructive events in one hour while asleep, it means that obstructive sleep apnea is present.

When obstructive sleep apnea is diagnosed, CPAP therapy is the most common treatment. CPAP provides a constant airflow through a mask. The air that’s provided by the CPAP machine helps the person’s breathing and there are no more obstructions. These changes are called central sleep apnea events. When they are happening, the condition is called central sleep apnea.

On one hand, CPAP treatment resolves the issues of obstructive sleep apnea.

On the other hand, CPAP treatment can cause central sleep apnea.

The central sleep apnea events must happen five times in one hour of sleeping to confirm the existence of central sleep apnea.

They need to constitute more than 50% of the total number of apnea and hypopnea events.

What this means is if you have 100 apnea events while you sleep with the CPAP machine on, and only 49 or fewer events are central sleep apnea events, you don’t have central sleep apnea.

As we’ve mentioned earlier, this condition is called central sleep apnea or complex sleep apnea.


Complex sleep apnea can be common when someone starts with CPAP treatment or bilevel therapy. It can happen in 2% to 20% of people when they start with the CPAP treatment. The key is that it can happen when someone starts with CPAP treatment, and this doesn’t mean that it will persist. The studies show that it persists with therapy in only 2% of the people.


We’ve discussed that CPAP therapy can cause complex sleep apnea.

However, there can be several contributions to the condition, and not all are because of CPAP therapy. Some people could be predisposed towards the condition as a result of instability in their control of breathing. It can happen to people who already have difficulties with maintaining sleep, like insomnia. In some cases, it appears to be triggered by low carbon dioxide levels. If someone has more severe sleep apnea from the beginning or has more central apnea events before they started CPAP treatment, these things can increase the risk.

It’s interesting to point out that it happens more to men than women.

Also, not only CPAP treatment can cause complex sleep apnea. Other treatments of sleep apnea can lead to complex sleep apnea, too. Some reports say that surgery and the use of an oral appliance caused complex sleep apnea. The pressures of PAP therapy can be problematic too if they are either too high or too low.

Effects and Treatment

All in all, complex sleep apnea usually resolves over time, but there are 2% of people in which persist and may have more consequences. Now, complex sleep apnea can be recognized to persist on a routine download of PAP compliance data.

Persistent complex sleep apnea together with a high residual AHI can cause continued sleep fragmentation and oxygen desaturation and this may lead to other health problems. If you want to resolve complex sleep apnea, you need to address the underlying causes one by one.

In a nutshell, complex sleep apnea usually resolves with time in 98% of cases as therapy continues. Depending on the case, you might not need to intervene in any way, just wait and watch the remaining events to resolve on their own.

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