Flow limitation, Minute vent and Tidal Volum

[Kristin]

Hi.
I use Sleepy Head, and every day I try to read my charts to better understand how I am doing. I have also received valuable advices from this forum. 
I have both Sleep Apnea and COPD, and based on what I have read: Flow Lim. Minute Ventilation and Tidal Volume is important to know sometihing about. So I have read some short explanations.

I think I understand what flow limitation is, and why I never Reach zero in that graph (COPD). Before I changed mode from Auto For Her to Autoset and started to use EPR the graph always went to 1 during the night. Now I am at 0.5-0.7, and it has made me feel much better. See http://www.apneaboard.com/forums/Thread-...d-pressure.  My question is what the "normal" numbers for Flow Lim are, and how I can make those figures as good as it gets. I am posting a overwiew.

My other question is about Minute Vent and Tidal Volum. What is, again, normal figures for a female, 159 cm and normal weight? What am I supposed to look for in these graphs, and what can they tell me? If I have understood correctly, these two graphs are associated with eachother, but I can't seem to get how. It might is due to language since English is not my main language.
Is there someone out there who can help me understand?

Another question: Do I have the best machine to treat the combination of Sleep Apnea and COPD?

I must admit that I find it exciting to learn about these machines and how they work. When I read on this forum I find so much knowledge about Sleep Apena, charts and how to read them, how optimize treatment, machines and how they work etc.

By the way: I live in a country where you get the machine and equipment for free when you are diagnosed with Sleep Apnea. After having read about how difficult these matteres can be in other countries I feel so grateful for not having to struggle to get a machine. I feel terrible thinking of how difficult it must be when you have to struggle when beeing so tired, and the head is full of fog. I am impressed by your ability to keep fighting. 

Thank you to everyone out there for helping, it means alot!

Kristin
(Sorry for my poor English, hope you understand)

[Walla Walla]

I think the basic concern comes down to your O2 level. If your Oxygen level is adequate than your tidal volume and minute vent are adequate. There is no hard and fast rule on what number is right for each person. You might want to buy a recording oximeter to monitor your O2 levels while you sleep.

Flow limitations, if they are not disturbing your sleep or dropping your O2 are not a huge concern. They can drive pressure up which can be controlled by capping the maximum pressure.

[Sleeprider]

Kristin, I have done quite a bit of work rewriting the Beginners Guide to Sleepyhead to answer questions like this http://www.apneaboard.com/wiki/index.php...SleepyHead This would be a great place to start understanding some of the details of your therapy. I also wrote the Flow Limitation Wiki http://www.apneaboard.com/wiki/index.php...Limitation

The summary graphs are not going to help us understand the dynamics of your flow limitation, tidal volume and other respiratory details. Averages and statistical percentiles are nothing more than statistics, and a breath by breath analysis of the respiratory rate and response to pressure and EPR is much more useful. The flow limitation statistics are really an index of the "roundness" of the inspiratory curve relative to the preceding 30 minutes or so. The index can be different for different individuals. I have seen severe flow limitation that was not graphed or flagged as flow limited, because the person never had any "normal" breathing. So the flow limit graph by itself is not so useful.

Tidal volume charts are available on the internet, but individual expiratory tidal volume will vary a lot. With COPD you probably have performed spirometry tests to measure your forced expiratory volume and other tests, and these are much more valuable in understanding your health than the tidal volume in Sleepyhead. Your tidal volume can be changed, and usually increased with ventilation pressure support in bilevel, or EPR (slight change) in CPAP. The Sleepyhead tidal volume is again more useful as a relative index to how your are responding to the therapy, and it will reflect problems in therapy if it is very low, or very high.

[Kristin]

I think the basic concern comes down to your O2 level. If your Oxygen level is adequate than your tidal volume and minute vent are adequate. There is no hard and fast rule on what is number is right for each person. You might want to buy a recording oximeter to monitor your O2 levels while you sleep.

-Thank you, Walla Walla. I might do that.

Flow limitations, if they are not disturbing your sleep or dropping your O2 are not a huge concern. They can drive pressure up which can be controlled by capping the maximum pressure.

- I think I did that last night! So it is ok that pressure reaches the max pressure as long as it is due to flowlimitation? If it is no bother for you, would you be so kind to take a look at my last post in the other thread: Trouble with leaks and pressure? One of the thumbnails is from last night. I hope it is ok to ask.

Kristin

[Kristin]

Kristin, I have done quite a bit of work rewriting the Beginners Guide to Sleepyhead to answer questions like this http://www.apneaboard.com/wiki/index.php...SleepyHead  This would be a great place to start understanding some of the details of your therapy.  I also wrote the Flow Limitation Wiki http://www.apneaboard.com/wiki/index.php...Limitation

Thank you, Sleeprider. I will do that.

Kristin

[Walla Walla]

I think the basic concern comes down to your O2 level. If your Oxygen level is adequate than your tidal volume and minute vent are adequate. There is no hard and fast rule on what is number is right for each person. You might want to buy a recording oximeter to monitor your O2 levels while you sleep.

-Thank you, Walla Walla. I might do that.

Flow limitations, if they are not disturbing your sleep or dropping your O2 are not a huge concern. They can drive pressure up which can be controlled by capping the maximum pressure.

- I think I did that last night! So it is ok that pressure reaches the max pressure as long as it is due to flowlimitation? If it is no bother for you, would you be so kind to take a look at my last post in the other thread: Trouble with leaks and pressure? One of the thumbnails is from last night. I hope it is ok to ask.

Kristin

I'd probably set the maximum pressure to 15cm and see how that goes.

[ardenum]

In COPD theres a subtype called CO2 retainers. With suplemental O2 you're even more at risk of retaining CO2. 

In normal people a higher CO2 levels stimulate breathing. In CO2 retainer subtype, the lungs have trouble removing CO2 from blood. Your brain essentially becomes less sensitive to CO2 rises and in this subtype the body relies more on low O2 to trigger breathing. When you get supplemental oxygen you trick the body into less breathing which makes your CO2 rise even more. It's a vicious cycle

Lethargy/sleepiness is a common side effect. Untreated however leads to coma.

So just O2% isnt enough you need to at least do a venous and arterial blood gas analysis. If your arterial gas levels are in range but your venous aren't its a sign you aren't eliminating enough CO2, your bicarbonate will also rise in this case. I'm mentioning venous gases being important because doctors usually ignore it if arterial levels are fine. It's not. It's a sign things arent going in the right direction.

The change in the setting might have allowed you to remove more CO2 then usual, hence you feel much better.

Its of utmost importance to do blood gas analysis of both venous and arterial blood and if possible an overnight study with a capnograph next to a O2%sat finger machine.

I'm sure a major hospital or clinic in Norway has a setup like that.

[Kristin]

Walla Walla-Again: thank you for your help!

Kristin

[Kristin]

In COPD theres a subtype called CO2 retainers. With suplemental O2 you're even more at risk of retaining CO2. 

In normal people a higher CO2 levels stimulate breathing. In CO2 retainer subtype, the lungs have trouble removing CO2 from blood. Your brain essentially becomes less sensitive to CO2 rises and in this subtype the body relies more on low O2 to trigger breathing. When you get supplemental oxygen you trick the body into less breathing which makes your CO2 rise even more. It's a vicious cycle

Lethargy/sleepiness is a common side effect. Untreated however leads to coma.

- Crowtor: this is very interesting. I did not know this.

So just O2% isnt enough you need to at least do a venous and arterial blood gas analysis. If your arterial gas levels are in range but your venous aren't its a sign you aren't eliminating enough CO2, your bicarbonate will also rise in this case. I'm mentioning venous gases being important because doctors usually ignore it if arterial levels are fine. It's not. It's a sign things arent going in the right direction.

- I have taken an arterial blood gas analysis, but no venous… I will definiatly follow that up.


The change in the setting might have allowed you to remove more CO2 then usual, hence you feel much better.

Its of utmost importance to do blood gas analysis of both venous and arterial blood and if possible an overnight study with a capnograph next to a O2%sat finger machine.

I'm sure a major hospital or clinic in Norway has a setup like that.

- I hope so. This was all new to me.
Thank you so much for telling me!

Kristin