Respiratory Effort Related Arousal (RERA)

does anybody know the difference between Respiratory Effort Related Arousal (RERA) and hypopnea? how much does RERA usually affect pulse rate?

I don't know the exact parameters but since no one has replied yet, I'll tell you what I know and if I'm wrong someone can say so.

My understanding is that a RERA is less 'severe'? 'noticeable'? than a hypopnea. A hypopnea is a flow limitation of >50% for >10 seconds isn't it? Well, a RERA is lower than one of those parameters I think. And it doesn't have to be associated with a desaturation event to be an interruption to sleep architecture and to create problems. My understanding is that desaturation stresses the cardiovascular system thereby increasing the heart rate. But even without increased heart rate, having several arousals from deeper sleep can lead to pronounced fatigue and other symptoms, and can in some cases be just as serious as OSA.

I think that breathing events are on a gradient and medicine tries to put them into 'steps'. Like other areas of medicine, sometimes it can be useful to think of how the body works, rather than the firm 'categories'. But that's just my sleep-deprived brain talking.

Bluesky....

Might we equate RERA with "flow limitations"?

There are various guidelines for hypopnoeas, but usually a hypopnoea is said to occur when there is a clear reduction (like between 50-80%) in breathing compared with baseline breathing. The event has to last for 10 seconds or greater and there can be an associated drop in oxygen saturation. A RERA is not quite just flow limitation; rather, it is a breathing sequence (also 10 secs or greater) that shows increasing respiratory effort with each breath, culminating in an arousal from sleep. Hope this helps.

You can only know if you have a RERA if you have an EEG recording, which unequivocally shows the arousal. Flow limitations, meanwhile, are detected and are part of the data from some data-capable CPAP machine (as well as the sleep lab equipment).

I am not sure if they equate exactly, because in one of my titration studies, the PSG tech noted "RERAs" in her notes happening at a certain time. Later, the hypnogram (an automated printout of sleep stages, 02 levels, heart rate and respiratory events) had "snoring" as what was happening in the time. BUT, during that time, there were MANY changes in sleep stage and even some awakenings, which made me think the situation was RERAs, but the automated scoring seemed to think they didn't meet the RERA criterion.

I think the point made about RERAs/flow limitations disrupting sleep and causing daytime fatigue and sleepiness is well-put. Some doctors seem to know this, others are oblivious. The guidelines for titration from the American Academy of Sleep Medicine say that you should be titrated for flow limitations. So make sure that is what is happening when you have your study and get your CPAP prescription.

Dreamtime wrote:There are various guidelines for hypopnoeas, but usually a hypopnoea is said to occur when there is a clear reduction (like between 50-80%) in breathing compared with baseline breathing. The event has to last for 10 seconds or greater and there can be an associated drop in oxygen saturation. A RERA is not quite just flow limitation; rather, it is a breathing sequence (also 10 secs or greater) that shows increasing respiratory effort with each breath, culminating in an arousal from sleep. Hope this helps.

Thanks, Dreamtime. I like your description of a "RERA."

For new readers... RERA = Respiratory Effort Related Arousal.

As I understand it (and I may be stating it wrong) with a RERA, the brain arouses the person (to breathe better) from whatever stage of sleep the person happens to be in when the limited air flow and increased effort to get more air is occurring -- the arousal happening before the O2 sat drops enough to call the event an hypopnea.

Arousals can happen without the person ever being aware of them at all....not having awakened long enough to be aware of being awake.

twasbrillig wrote:You can only know if you have a RERA if you have an EEG recording, which unequivocally shows the arousal.

Right. Plus flow and effort data I'd expect. The belts around chest and abdomen during a sleep study showing the "effort."

twasbrillig wrote:Flow limitations, meanwhile, are detected and are part of the data from some data-capable CPAP machine (as well as the sleep lab equipment).

Yes. To clarify that a bit, no plain CPAP machine that I know of tries to detect flow limitations, even if the plain CPAP is capable of detecting and recording apneas, hypopneas, and leaks ("full data", as we use the phrase on the message board.)

An Autopap (autotitrating "CPAP" machine) utilizes flow limitation data, so an autotitrating cpap machine operating in autotitrating mode, would indeed look for and detect flow limitations, as you say, twasbrillig. Even an autopap won't try to look for flow limitations or detect them if the autopap is being operated in CPAP mode rather than in autotitrating mode.