Interpreting Sleep Study Results

I finally got a copy of my most recent (6 weeks ago) sleep study. I now have copies of all 3 and none of them make sense. I've seen some of the terms here and there, but have no idea what to make of them. How can I get comfortable with them? How do I know where the issues are and where there have been improvements?

The first thing you should check is to see if your oxygen saturation dropped below 90%.

The next question is why. Looking at your AHI index will give you some idea of what is going on. You are hoping for a value < 5.

Finally, you need to determine if you suffer from restless leg syndrome.

If your airway is obstructed enough to reduce the oxygen levels in your blood, you need some treatment to get your oxygen levels back up.

Post and the content and the good folks here will try to help you.

gregIN wrote:... I finally got a copy of my most recent (6 weeks ago) sleep study. I now have copies of all 3 and none of them make sense. ...

As noted, use Photobucket or another online source and we would be happy to try to explain what they mean.

Just a note about "none of them make sense". Most fields develop a vocabulary to help explain a specific situation. It's no different if it is cars or computer or cameras. If you don't know the vocabulary anything that uses that vocabulary becomes meaningless. Just ask my wife, who complains that when I went into my technical discussions for work, she could understand every third word or so. Oops! And here I thought I was being quite clear. I have no doubt the sleep lab that put together your sleep study report thought the same thing.

So, by posting the content here, we can help interpret the vocabulary and provide pointers to other resources to help you better understand the meaning behind the reports.

First of all, thank you for being so willing to help!

In December of '09:

At baseline, there were 15 obstructive apneas, 14 mixed apneas and 132 hypopneas. 168 events were seen with an apnea/hypopnea index of 76 per hour of sleep. Desaturations down to 81%.

At that point, they started CPAP at 5 cm water pressur and titrated up to 15 cm water pressure. Then BiPAP was started and titrated up to 20/16. When obstructive events declined, central events and RDI remained anywhere from 71-120 per hour. There were 19 periodic limb movements with an index of 3.

In January '10:

Used servoventilation. Recorded for 460 minutes of which 413 were total sleep time. Sleep efficiency was 92%.

There were 102 arousals for arousal index of 15 per hour, and 21 periodic limb movements with an index of 3 per hour.

Servoventilationtitration was started at an IPAP of 21 and EPAP of 11. This was titrated up to IPAP of 23 and EPAP of 13. There were continued hypopneas, but no apneas.

The mean saturation was in high 80s with a low of 83%

So, as of 10/25, the Auto SV pressure settings are:

Max Pressure: 30 cm H2O
Max EPAP: 17 cm H2O
Min EPAP: 8 cm H2O
Max PS: 15 cm H2O
Min PS: 0 cm H2O
Bi-FLEX 3
Rate: 12 BPM

Any help trying to figure all this out is greatly appreciated!

What machine and mask are you using Greg?

As much as the manufacturers want you to use servoventilation machines many, maybe even most, people with CPAP emergent centrals still do well after a few months on an APAP properly set. You were titrated to high pressures and this can be the cause of the centrals. Without knowing more it's impossible to guess whether you really needed such high pressure but we often see people "over titrated."

When your airway obstructs air flow, oxygen saturation falls. A primary goal of xPAP therapy is to keep your airway open. An excellent indicator of having an open airway is your oxygen saturation. The goal is to always stay above 90%.

Keep in mind that if the lungs and/or heart are damaged, you may not be able to maintain an O2 saturation above 90%. This is a discussion you need to have with a doctor.

If your oxygen desaturation is caused by airway obstruction, xPAP is supposed to remove this obstruction. With the obstruction removed, the oxygen saturation should increase.

The next step is to minimize arrousals. Some arrousals can be eliminated by blowing air up your nose, but most of the time there is more involved. For example restless legs can keep you from getting a good nights sleep, but that has nothing to do with oxygen saturation.

I think you need to address the obstruction issue first, then you can work out the other details. In 12/09 you desaturated down to 81%, in 1/10 you only went down to 83%. Improvement, but keep in mind that the goal is to limit the desaturation to 90%.When your airway obstructs air flow, oxygen saturation falls. A primary goal of xPAP therapy is to keep your airway open. An excellent indicator of having an open airway is your oxygen saturation. The goal is to always stay above 90%.

Keep in mind that if the lungs and/or heart are damaged, you may not be able to maintain an O2 saturation above 90%. This is a discussion you need to have with a doctor.

If your oxygen desaturation is caused by airway obstruction, xPAP is supposed to remove this obstruction. With the obstruction removed, the oxygen saturation should increase.

The next step is to minimize arousals. Some arousals can be eliminated by blowing air up your nose, but most of the time there is more involved. For example restless legs can keep you from getting a good nights sleep, but that has nothing to do with oxygen saturation.

I think you need to address the obstruction issue first, then you can work out the other details. In 12/09 you desaturated down to 81%, in 1/10 you only went down to 83%. Improvement, but keep in mind that the goal is to limit the desaturation to 90%.

Greetings Greg! Welcome to the forum. You might want to register as a user of the forum. One thing that will help is that it will help others know the type of equipment that you have. See the following link on how to register your equipment:

wiki/index.php/Registering_Equipment_in_User_Profile

To others, based on the information provided, Greg is using a Respironics BiPAP Auto SV Advanced unit:

So, as of 10/25, the Auto SV pressure settings are:

Max Pressure: 30 cm H2O << The advanced unit can go upto 30cm H2O >>
Max EPAP: 17 cm H2O
Min EPAP: 8 cm H2O
Max PS: 15 cm H2O
Min PS: 0 cm H2O
Bi-FLEX 3
Rate: 12 BPM

Now, let's see if I can help you better understand your sleep study...

gregIN wrote:... In December of '09:

At baseline, there were 15 obstructive apneas, 14 mixed apneas and 132 hypopneas. 168 events were seen with an apnea/hypopnea index of 76 per hour of sleep. Desaturations down to 81%.

At that point, they started CPAP at 5 cm water pressur and titrated up to 15 cm water pressure. Then BiPAP was started and titrated up to 20/16. When obstructive events declined, central events and RDI remained anywhere from 71-120 per hour. There were 19 periodic limb movements with an index of 3. ...

You had a split night study. That is they initially just measured you sleeping without any xPAP device. That is without a CPAP or BiPAP or ASV unit. They do this to prove that you have obstructive and/or central sleep apnea. If the test shows you have no problem, then they would not prescribe an xPAP device. An xPAP device is any device that provides Positive Airway Pressure to help you breathe while sleeping.

The Desaturation indicates that your body was being starved for oxygen during these apnea events. Traditionally, anything lower than 87% require oxygen. Of course the Positive Airway Pressure therapy helps keep your airway open and helps eliminate the need for supplemental oxygen.

About half way through the sleep study they put a CPAP unit on you and tried to see if they could eliminate the apnea events. They reached 15cm H2O. "cm H2O" is centimeters H2O. That is the amount of positive airway pressure that would raise a column of water about 6.25 inches higher than normal. This is the scale that is used to measure the air pressure used in respiratory medicine.

Once they reached 15cm H2O with CPAP, the changed the therapy mode to BiPAP. CPAP is Continuous Positive Airway Pressure ... BiPAP is BiLevel Positive Airway Pressure. BiPAP provides two different pressures. When you breathe in it uses a higher pressure. When you exhale it uses a lower pressure. These are in inspiration and expiration pressures. The two different pressures make it much easier to breathe with higher pressures and help reduce central apneas that may arise with one continuous pressure.

They gradually increased the pressure to 20cm H20 for the inspiration pressure and 16cm H2O for the expiration pressure. That pressure would raise a column of water about 8 1/3 inches when you inhale and about 6 2/3 inches when you exhale.

Even with BiPAP at that pressure, you continued to have central sleep apnea events. Your respiratory disturbance index (RDI) was at 71 to 120 per hour with BiPAP. That is the act of breathing seemed to disturb your sleep.

However, most insurance companies (and doctors) insist that you first try CPAP and/or BiPAP therapy before moving to something else. Why? Sometimes it takes time for your body to adjust and then the problems with sleep decrease. Not always. But it happens enough of the time that doctors want to try the simplest therapy possible before moving to Adaptive Servo-Ventilation (ASV) therapy.

But obviously it did not solve your problems, since you were back for a titration using ASV (adapative servo-ventilation) therapy. Why would they do that? Remember those central sleep apnea events? Well, neither CPAP nor BiPAP tend to be very effective at treating central sleep apnea. That was why Resmed pioneered adaptive servo-ventilation (ASV). After I review your sleep study, I will provide a little bit of a background on central sleep apnea and ASV. I will also point you to some articles that you might want to read to better understand both.

gregIN wrote:... In January '10:

Used servoventilation. Recorded for 460 minutes of which 413 were total sleep time. Sleep efficiency was 92%.

There were 102 arousals for arousal index of 15 per hour, and 21 periodic limb movements with an index of 3 per hour.

Servoventilationtitration was started at an IPAP of 21 and EPAP of 11. This was titrated up to IPAP of 23 and EPAP of 13. There were continued hypopneas, but no apneas.

The mean saturation was in high 80s with a low of 83%

...

As noted, they titrated you using ASV therapy. "Titration" comes from a chemical term meaning making a slow, measured addition of a compound until the expected chemical reaction occurs. Essentially with xPAP devices, it is a slow, measured addition of pressure or changes to parameters until the sleep problems are effectively managed.

They recorded you for 460 minutes (about 7.5 hours). During that time you slept 413 minutes (almost 7 hours). Your sleep efficiency was 92%, which indicates you can get to sleep fairly easily and stay asleep.

You had 102 arousals (about 15 per hour). This means that while asleep your body had an intrusion of an alpha wave (common during wakefulness). You didn't awaken. But it tends to disturb the normal progression of sleep. If you were in deep sleep you would have roused a lighter stage of sleep. Too many of these can make your feel very tired.

On thing that can also interfere with your sleep is periodic limb movements. Periodic limb movement disorder (PLMD) can also cause arousals. In this case you only had about 3 per hour, which is not all that much.

The titration of the adaptive servo-ventilation therapy started at an IPAP (Inspiration Positive Airway Pressure) of 21cm H2O and EPAP (Expiration Positive Airway Pressure) of 11cm H2O. They ended up at IPAP of 23 and EPAP of 13. That eliminated all apnea events, although the hyponea (low airflow) events continued.

gregIN wrote:... So, as of 10/25, the Auto SV pressure settings are:

Max Pressure: 30 cm H2O
Max EPAP: 17 cm H2O
Min EPAP: 8 cm H2O
Max PS: 15 cm H2O
Min PS: 0 cm H2O
Bi-FLEX 3
Rate: 12 BPM
...

The maximum pressure the ASV can go is to 30cm H2O. A little more on that in a bit.

The maximum EPAP value is 17cm H2O. That is you won't have to exhale against more than 17cm H2O. But it can go as low as 8cm H2O (less than 1/2 the highest exhalation pressure).

The machine then adds pressure to this for the inhalation pressure. It can range from 0cm H2O (the same as exhalation) all the way up to 15cm H2O over the exhalation pressure. Your machine will auto-titrate to try to provide the least pressure needed to allow you to breathe well. If you obstruct or snore, it may increase the pressures until it is eliminated.

The Bi-FLEX setting helps make it easier to breathe with the machine. Think of it as rounding off the inhalation and exhalation pressures. A sudden change tends to disturb most people, and Respironics uses this technology to cause less disturbance when the pressure changes.

The "Rate" indicates that you must breathe at least 12 times per minute (breaths per minute). Or once every 5 seconds. If you fail to breathe in that amount of time, it will shift to inhalation pressure.

Now a little bit about ASV technology and the reason behind it. Central sleep apnea as well as other issues such as periodic breathing and Cheyne-Stokes Respiration (a type of periodic breathing) occurs due to poor regulation of breathing by your body. Essentially it is an undershoot, overshoot pattern. That is, for whatever reason your body does not properly recognize that the CO2 levels have increased in your body. Respiration tends to slow until it stops. This is the undershoot side of the cycle. Eventually your CO2 builds up to the point the body recognizes it must compensate by breathing faster. And suddenly the body starts breathing again. In fact, it tends to overshoot and hyperventilate a little. Obviously this is the overshoot side of the cycle. This increased breathing rate causes the body to blow off more CO2 than needed, which depresses the drive to breathe. And the cycle starts over again. Over and over.

Resmed, the manufacturer that first developed the therapy, speculated that if they could help sustain the breathing during a central apnea it would help break this cycle. So, when a central sleep apnea occurs the machine jacks the pressure up quite high (upto 30cm H2O in your case) to try to sustain normal respiration. That's the adaptive servo-ventilation side of it. It's not straight ventilation. But it adapts to meet your needs.

Resmed found during clinical trials that it is indeed VERY effective.

Now a little homework for you. Here is an article that explains the causes and therapy for Central Sleep Apnea:

Central Sleep Apnea: Pathophysiology and Treatment
http://chestjournal.chestpubs.org/conte ... l.pdf+html

Here is an article that explains how effective ASV therapy is in treating Central Sleep Apnea:

Efficacy of Adaptive Servoventilation in Treatment of Complex and Central Sleep Apnea Syndromes
http://chestjournal.chestpubs.org/conte ... l.pdf+html

Sorry for the very long post. But I hope it helps you better understand your sleep studies and your situation.

Thanks, everyone, for the input. I think I need to do more studying on the whole sleep apnea thing!

I know it must feel overwhelming. In fact, in two years you went from nothing to an ASV unit. Ouch! Most people literally take years to reach a diagnosis that requires an ASV unit. So, most of us have had the chance to question and learn.

But it's good to see you registered!! Feel free to ask questions. Not just about the sleep studies. Ask about your mask. Ask about using a humidifier with the ASV unit. Ask about living with xPAP therapy.

There are not a "lot" of ASV users in the forum (but there are more in this forum than any other I have found). But there is a WEALTH of experience and insight into living with xPAP therapy. Your doctor and DME really don't know what it is like - unless they use xPAP therapy themselves. The experience you find here can make a world of difference for you and others.

Best wishes and hopefully many happy dreams!