Sometimes Waking Short of Breath while on BiPAP - EPAP, PS Settings?

[holden4th]

Recently I've been waking up at night with a feeling of being short of breath while using my BiPAP. This also happens during the day while prone when I lie down on my bed and read(no PAP). For those who've experienced this, it's not a nice sensation and almost seems to induce a sense of panic. Sitting up solves the issue. So does getting up, moving around for a while and may.be a cup of tea. I've taken the issue to my doctor but want to look at why it's happening with PAP therapy because it really shouldn't. This is what a BiPAP is designed for.

I decided to look at my BiPAP settings and made a couple of changes which might have helped as I've slept without this happening for the last two nights. But that doesn't mean it might not return. My feeling was that my EPAP Min was too high causing me to struggle a bit to exhale. I adjusted this down from 11.5 to 9.3. I also looked at PS which was set at 4.7 and took this down to 3.4 I also increased the Ti MAX setting from 2.7 to 3.2 in case this was triggering and early exhalation. Ti min stayed at 0.3

I did this in the middle of the night and my treatment immediately felt more comfortable and I slept without further interruption. This has made me wonder what the effect of these settings do. I know that Ti Max, if set too low, can try to trigger an early exhalation.

I know PS gives a lower pressure on exhalation but at what point does this let apneas and hypopneas happen. Can it cause centrals?

Can EPAP/IPAP differences create a lack of CO2 which may certainly explain my feeling of breathlessness as I may have stopped breathing until the CO2 response kicked in?

I've looked at my OSCAR charts and can't see any glaring issues.

An explanation of the effects of changing Ti, EPAP and PS levels would really help me and I suspect others as well.

[Gideon]

Napping without CPAP can cause your shortness of breath as you have the full force of your untreated apnea acting on you.

Generally an increase in EPAP will likely resolve your shortness of breath.

Do post your OSCAR charts so we can offer you specific advice.

Also an increase in pressure, pressure fluctuations or Increase in PS may, only may result in increased centrals.

[SevereApnea]

"I've taken the issue to my doctor but want to look at why it's happening with PAP therapy because it really shouldn't."

Sorry to hear you are having these problems. So: what did the doc say/do/suggest?

If you are feeling the same thing without the CPAP (you mentioned you had the same feeling lying prone reading) a little birdie in the back of my head asks: is this just CPAP related? Could this be non-CPAP related? Could there be 2 things going on here? Has he/she looked for a cause other than CPAP? Most Docs don't know much about CPAP. If you say this is CPAP related they will draw a blank and be so relieved to handball that back to you. 

I assume they have cleared you of medical conditions: heart failure (tea is a diuretic, you said you felt better after tea), diaphragmatic or hiatus hernia, reflux whatever else they look for. If it was me I would want some very clear answers to these issues before going down the rabbit hole of CPAP adjustments. 

As Gideon said, don't be shy to post some charts. 

[holden4th]

   

"I've taken the issue to my doctor but want to look at why it's happening with PAP therapy because it really shouldn't."

Sorry to hear you are having these problems. So: what did the doc say/do/suggest?

If you are feeling the same thing without the CPAP (you mentioned you had the same feeling lying prone reading) a little birdie in the back of my head asks: is this just CPAP related? Could this be non-CPAP related? Could there be 2 things going on here? Has he/she looked for a cause other than CPAP? Most Docs don't know much about CPAP. If you say this is CPAP related they will draw a blank and be so relieved to handball that back to you. 

I assume they have cleared you of medical conditions: heart failure (tea is a diuretic, you said you felt better after tea), diaphragmatic or hiatus hernia, reflux whatever else they look for. If it was me I would want some very clear answers to these issues before going down the rabbit hole of CPAP adjustments. 

As Gideon said, don't be shy to post some charts. 

OK, I have mitral valve regurgitation but the cardiologist said this should not cause shortness of breath. I've just had a chest CT scan done and all it found was some coronary artery calcification (which both my cardiologist and I know about) and the slight enlargement that comes with that. No obstructions of any sort. Back to my GP for further consultation.

Here is a chart from last night - you can see where I had to wake up.

[SevereApnea]

Good to hear you are having the medical issues managed concurrently and thanks for posting the chart of 29th Jan.

Nice low AHI! but you are still having disturbed sleep which we see often and confirms that low AHI does not automatically mean good restorative sleep.

You can see your Insp Times never approaches the Ti Max you have set so we can discount that.
You don't need to mess with the Ti Min.

You asked: 
"I know PS gives a lower pressure on exhalation but at what point does this let apneas and hypopneas happen."
Well with the Vauto you set the Min EPAP and the PS gets added to that. A lower PS will add less pressure to your Min EPAP. A higher PS will add more pressure to your Min EPAP. Once you lower the Min EPAP enough you can expect to see more OA.

Back to your chart. 

Arousals:
Apart from the frequent arousals and respiratory values nothing else jumps out at me.

There are no clear CA or OSA events prior to the arousals.
Only once at around 22:30 did the pressure start to rise a bit this may cause arousal in some people. Unless this is frequent you can ignore this.
Some snoring but does not seem to initiate or precede the  arousals.

Leaks:
Leak rates are under control: on two occasions they peaked a bit prior to waking, but can't say if this is cause of effect.
Low leak rates mean the minute ventilation and tidal volumes are less likely to be skewed down and more likely to be reliable and consistent.

FLs
Lovely flow limits, most would be happy with those values!

Respiratory values:
Your Med VT and 95% tidal volumes may be on the high side depending on your height and weight.
What does strike me is your high respiratory rates and high minute ventilation.
Again this would need to be correlated with your height, weight, lung functions.
It may be worth doing an online search for normal ranges for spontaneous breathing and also what the desired values are in ventilated patients.
We would have to defer to others with more experience in that area, but with a high Respiratory Rate I wonder if your work of breathing might be a factor in your arousals.

The only other thing that is noticeable to me is your short Exp Time of 2.28. Your I:E Ratio would be around 1.7. I think on this forum values of 2 - 3 are mentioned as better. Maybe do a search here on the forum for I:E ratios and see what you can find and how you can tweak these.
(At least we know the Vauto reads these better than the AirSense 10 Autoset series, not being fooled by cardiogenic oscillations.)

You mentioned you felt better after lowering your PS on your Vauto. Perhaps your PS is still too high for you and pushing your tidal volumes up a tad.

If it were me I would slowly reduce PS, keep an eye on FLs, take notes and see how I felt.
I would also go back 6 months and record the Insp Times vs Exp times and see what changed. At what stage did you make any changes to your Trigger and Cycle sensitivities? did these changes effect your Exp Times.

Bit of homework there for you!

Lastly if none of this pans out there be non sleep related issues at play.

[holden4th]

Good to hear you are having the medical issues managed concurrently and thanks for posting the chart of 29th Jan.

Nice low AHI! but you are still having disturbed sleep which we see often and confirms that low AHI does not automatically mean good restorative sleep.

You can see your Insp Times never approaches the Ti Max you have set so we can discount that.
You don't need to mess with the Ti Min.

You asked: 
"I know PS gives a lower pressure on exhalation but at what point does this let apneas and hypopneas happen."
Well with the Vauto you set the Min EPAP and the PS gets added to that. A lower PS will add less pressure to your Min EPAP. A higher PS will add more pressure to your Min EPAP. Once you lower the Min EPAP enough you can expect to see more OA.

Back to your chart. 

Arousals:
Apart from the frequent arousals and respiratory values nothing else jumps out at me.

There are no clear CA or OSA events prior to the arousals.
Only once at around 22:30 did the pressure start to rise a bit this may cause arousal in some people. Unless this is frequent you can ignore this.
Some snoring but does not seem to initiate or precede the  arousals.

Leaks:
Leak rates are under control: on two occasions they peaked a bit prior to waking, but can't say if this is cause of effect.
Low leak rates mean the minute ventilation and tidal volumes are less likely to be skewed down and more likely to be reliable and consistent.

FLs
Lovely flow limits, most would be happy with those values!

Respiratory values:
Your Med VT and 95% tidal volumes may be on the high side depending on your height and weight.
What does strike me is your high respiratory rates and high minute ventilation.
Again this would need to be correlated with your height, weight, lung functions.
It may be worth doing an online search for normal ranges for spontaneous breathing and also what the desired values are in ventilated patients.
We would have to defer to others with more experience in that area, but with a high Respiratory Rate I wonder if your work of breathing might be a factor in your arousals.

The only other thing that is noticeable to me is your short Exp Time of 2.28. Your I:E Ratio would be around 1.7. I think on this forum values of 2 - 3 are mentioned as better. Maybe do a search here on the forum for I:E ratios and see what you can find and how you can tweak these.
(At least we know the Vauto reads these better than the AirSense 10 Autoset series, not being fooled by cardiogenic oscillations.)

You mentioned you felt better after lowering your PS on your Vauto. Perhaps your PS is still too high for you and pushing your tidal volumes up a tad.

If it were me I would slowly reduce PS, keep an eye on FLs, take notes and see how I felt.
I would also go back 6 months and record the Insp Times vs Exp times and see what changed. At what stage did you make any changes to your Trigger and Cycle sensitivities? did these changes effect your Exp Times.

Bit of homework there for you!

Lastly if none of this pans out there be non sleep related issues at play.

Thank you for your detailed explanations and analysis of the chart I posted. There are others but they show a similar picture. Your response has raised a couple more questions for me. However, I'll do the obvious and lower the PS. It's currently at 3.6 so I'll take it down to 3.0. I've lived quite happily with a few OAs and hypopneas in the past so I'm not too concerned about that at the moment. I'll leave the EPAP min at 10.6 for the present and look at changing one parameter at a time. I've lowered the Ti Max to 2.9 - if it's not enough I'll know very quickly.

Despite doing some research I can't seem to find what I should do to lower the I:E ratio. In another thread it was suggested that I increase my  expiration time but I'm not sure how I would change any settings to make this happen. I imagine that to achieve either of those would be a similar tweak of settings.

One thing that did occur to me is the values for Trigger and Cycle. I have these set on Very High and High respectively. I believe that Trigger is what initiates a machine change at the end of exhalation. Cycle on the other hand is the opposite and responds to the beginning of exhalation and cycling back to EPAP. Could I have too high a sensitivity for Trigger and this is spontaneously initiating the beginning of IPAP too early and decreasing my exhalation time?

You also mentioned high respiratory rates and high minute ventilation. I'm assuming that you're saying that in the first instance my breathing rate is faster than it should be with the probability of less air going into my lungs? Does the high minute ventilation rate suggest that I am expelling more CO2 than would be normal? I know that importance of CO2 in triggering inhalation but is this an issue here?

One thing I will do when (not if) I wake up during the night will be the usual toilet stop and to calmly try and reinitiate XPAP. It will take a little bit of patience but it has worked for me in the past. Hopefully the change in PS will make this easier.

Finally, sleep is a pattern that you drop into and if that is a disturbed pattern it's what your body recognises and tends to repeat. From a psychological point of view you need to change that pattern.

I think I might have an answer for the breathlessness by day while prone. I like to read lying down and of course I'll nod off and get chin droop. It's very possible that when I do I'm experiencing OAs and as I'm not  fully asleep, stopping breathing wakes me up and leaves me with that really awful feeling. My soft cervical collar would prevent that during the night.

I'll report back next week and thanks for your insights as they are truly appreciated. I'll talk to my doctor about possible respiratory issues but I'm fairly sure that I don't have COPD.

[SevereApnea]

From the Clinician Manual page 5 and 6 (link HERE if you don't already have it) is that you could try one of two things to increase your Exp Time.

1. Lower your Ti Max as you are already doing. Like you said about calming your breathing before masking up. This is an important part of my sleep hygiene. Before hopping into bed, I sit bed-side and slow my breathing. Various ways to do this. Once in bed I will not mask up until my breathing has calmed down. In the past I have found my active waking breathing pattern fighting the Ti-Max on the machine. My Ti times during sleep are less than awake. So that certainly helps me. Same for when I go back to bed after a pit-stop. Good call on your part.

2. The Trigger Sensitivity of Very High will cut short your Exp Time and trigger an early increase of pressure, and may not be helping you. It is often recommended to increase the TS to help eliminate CA but possibly this be should be a last resort.
Increasing the Cycle Sensitivity to High will shorten the Insp time.

I don't understand the physiological outcomes of these, and stopped trying to second guess the effects on CO2 etc, there is no point unless we can actually measure that and we can't. I have played with them soon after getting my Vauto and generally found them very uncomfortable, especially if I have TS Low and Cycle set to High.

I guess what I am trying to say in a roundabout sort of a way is that maybe your TS and CS settings are driving your higher Respiratory rate, unless there are medical reasons for this.

All of these extra variable parameters can confuse the PAP treatment and add confounding variables which is why these machines are not prescribed in the first instance.

Some more discussion Over Here:

and More Over Here:

but I strongly suspect you have been over these already.

As you know individual comfort zones will be found by fine tuning the Min EPAP to minimize/eliminate OSA, the PS to help Flow Limitations and Hypopneas and balance OSA with CA, then finding what works best for you wrt TS and CS settings. 

(PS: sometimes when I lower my Min EPAP too far, say around 6 cmw, the expiration seems to go on forever, the chest sort of empties out/collapses in an uncomfortable way, so I prefer some airway/alveolar splinting at around 6.8 - 7 cmw but that's just me. At present I have sort of reached a steady state with comfort and would love to experiment more but am hesitant in case I upset the apple-cart in a manner of speaking).

Wishing you all the best and looking forward to hearing about your progress and adding to the valuable info on this board.

[holden4th]

Thank you! This is great information and something I can take on board. Last night was terrible and today I felt like I'd had no PAP treatment at all. I said I wasn't going to tweak too many things but the TS and CS are obviously wrong so not changing them would make no sense. I've dropped the TS to LOW and left the CS on HIGH. This is the only other change I'll make for the next few days just to see what happens.

So currently I have:

Max IPAP 25
Min EPAP 10.0 (I've had it lower in the past)
PS 3.0
Ti MAX 2.0
Ti MIN 0.3
Trigger LOW
Cycle HIGH

You mentioned a I:E ratio of 1.7 as being quite good. I'll have to do the maths to make that work and Maths is not my strong point.

The clinicians manual provided info I'd never come across before. Checking back through OSCAR for the last few years, including going into the data from my first BiPAP (which was a Respironics), my breathing rate seems to be steady around 16 bpm. The manual seems to suggest a Ti MAX setting between 1.3 and 2.0 and that would probably be on the higher side. At this point I'll leave it to see what happens with my other setting changes. If the expiration rate changes then surely my bpm would be less?

The discussions you posted made for very interesting reading. Once again, thank you for what you are providing me. I'll come back to this at the weekend and would appreciate your continuing contributions.

[holden4th]

Interesting night last night with an AHI of around 8.5. More importantly, a big increase in OAs and the appearance of a number of CAs which I rarely get. There were numerous Hs as well which I'm assuming that the machine dealt with before they became OAs.

I reread SevereApnea's posts and had a look at all the parameters. Yes, the change to a lower TS certainly did increase my expiration but by too much I would say. While the Median was 2.7 seconds the 95% was 5.2 and the max was 7.66 which surely is far too long. I tried exhaling continuously for 7.6 seconds and it became an effort. To try and combat this I've raised the Trigger to MED. I suppose I could have lowered the Cycle but thought I'd try this way first. While I didn't want to change anything for a few days I didn't see that I had an option.

Also interesting was my pressure. I lowered the Min EPAP to 10 and this seems to have brought the Median EPAP down to 11.2 a few points lower than what I've been experiencing I ran around 14.2 IPAP for much of the night.

Other points to note. Some of my arousals occurred after OAs.

So that's the only change I'll make and we'll see what happens - especially with CAs and OAs. My Max Exp time will also be noted.

The one plus was that breathing through the mask felt very comfortable.

[Geer1]

Trigger from very high to low is a big change. Higher trigger sometimes helps with centrals so my guess is that low is too low hence the increase in centrals. The centrals are a warning that you have manipulated the settings out of a comfortable range.

Low trigger and high cycle are both trying to force a short inhale but the reality is your spontaneous breathing will drive respiration and fight the machine (with centrals and all sorts of stuff) if you use settings that put the pressure out of sync with spontaneous breathing. You want to use the timing controls to try and match spontaneous breathing not force your spontaneous breathing to change. Trying to force breathing is never the goal unless you have a neuromuscular or hypoventilation issue which I assume you don't.

When working on these timing control settings two graphs are important, flow rate and mask pressure. For trigger sensitivity what you want to see is that pressure increases are being initiated when you take main inhalation and not prematurely during the end of your exhalation. If trigger is too high you will start seeing pressure increase before exhalation has finished and it will often start appearing as two pressure waves per breath (one falsely triggered early and then a second one triggered at inhale). My recommendation is to check if your old very high trigger was causing this and if so slowly adjust it down until that stops happening (in other words try high then normal, don't jump straight to low).

Cycle doesn't seem to clearly cause issues in the same way although many people find it uncomfortable on higher settings because it stops early trying to force you to stop inhaling. I believe it is mostly a comfort setting but if you are seeing pressure drop and flow rate continuing on it is an indicator your cycle sensitivity is too high. Most prefer normal or low rather than the high you are trying to use to force you to exhale.

Similarly you shouldn't need Timin or Timax unless you have medical issues that require it. 0.3 Timin and 2 Timax are fine and shouldn't ever really come into play (most inhalations are 1-1.5 seconds).