Low Oxygen Levels On VPAP

[airbusA346]

Hi,

Has anyone come across low oxygen levels while using a VPAP/non-invasive ventilator?

I've used my Contec CMS50I on three separate nights and get similar findings of my oxygen levels dropping throughout the night.

My VPAP is set to 26.0/9.0. Respiratory back up rate is 18. Spontaneous trigger breaths is 1%.

In the mornings I feel light headed/dizzy and spaced out.

I've already had a TOSCA study which showed my CO2 levels were OK on the VPAP, but my oxygen levels were all over the place.  The consultant said the average during that night was 92%.

   
   
   

[Sleeprider]

You are certainly well ventilated, and a low CO2 is consistent with your very high pressure support of 26/9 16-cm. We are getting into one of the most critical understandings of ventilation, which is "PEEP", or Positive End-Expiratory Pressure". In your case, that is the EPAP at 9.0 cm. PEEP controls oxygenation, which is different from ventilation from pressure support. Higher PEEP promotes better oxygenation by improving the exchange at the aveolar level. https://www.ncbi.nlm.nih.gov/books/NBK441904/ In addition to PEEP, we need to look at the efficacy of your ST VPAP treatment by looking at the machine data results for tidal volume and minute vent. Extremely high PS like you have will suppress the natural respiratory drive, so the machine is likely doing all the effort in your case. If you have the Sleepyhead data, feel free to post it.

Higher EPAP pressure should improve your SpO2 results, and considering your low CO2, the higher EPAP does not necessarily mean you need more IPAP or pressure support. Another option is obviously and oxygen bleed to your ST VPAP circuit. This is very easily added using an adapter and oxygen generator. I wrote this wiki earlier this year http://www.apneaboard.com/wiki/index.php...leed&go=Go

You have multiple potential solutions, and understanding the relationship of oxygenation and PEEP, and the ability to add an oxygen bleed to the positive pressure circuit are concepts you should research and discuss with your medical team.

[airbusA346]

You are certainly well ventilated, and a low CO2 is consistent with your very high pressure support of 26/9 16-cm.  We are getting into one of the most critical understandings of ventilation, which is "PEEP", or Positive End-Expiratory Pressure". In your case, that is the EPAP at 9.0 cm.  PEEP controls oxygenation, which is different from ventilation from pressure support. Higher PEEP promotes better oxygenation by improving the exchange at the aveolar level. https://www.ncbi.nlm.nih.gov/books/NBK441904/   In addition to PEEP, we need to look at the efficacy of your ST VPAP treatment by looking at the machine data results for tidal volume and minute vent.  Extremely high PS like you have will suppress the natural respiratory drive, so the machine is likely doing all the effort in your case.  If you have the Sleepyhead data, feel free to post it.

Higher EPAP pressure should improve your SpO2 results, and considering your low CO2, the higher EPAP does not necessarily mean you need more IPAP or pressure support.  Another option is obviously and oxygen bleed to your ST VPAP circuit. This is very easily added using an adapter and oxygen generator.  I wrote this wiki earlier this year http://www.apneaboard.com/wiki/index.php...leed&go=Go

You have multiple potential solutions, and understanding the relationship of oxygenation and PEEP, and the ability to add an oxygen bleed to the positive pressure circuit are concepts you should research and discuss with your medical team.

This is from last night (ResScan).

   

Spontaneous triggered breaths was 1% and s[spontaneous cycled breaths was 32%.

My CO2 during the TOSCA was 5.6.

I believe they want to maintain the big PS, because every time they have increased my IPAP they have increased the EPAP by the same amount.

[Sleeprider]

What I see in your resscan results are many places where tidal volume and minute vent are very low and suggest a possible obstruction.  Higher EPAP may keep the airway open, but I think you should perhaps consider whether a positional apnea may be occurring that would be better treated with a soft cervical collar.

If you don't already have it, the new version of Sleepyhead may work with your VPAP ST-A http://OSCAR Official Download Page ----> CLICK HERE ./testing/1.1.0/  I think being able to see the flow rate could be very helpful.

I believe they want to maintain the big PS, because every time they have increased my IPAP they have increased the EPAP by the same amount.

As I said, PS increases ventilation, but EPAP increases oxygenation.  Your ResScan charts show your tidal volume is often over 1000 mL and minute vent is between 15-20 L/min when things are going well. The problem is it drops off significantly suggesting apnea. Individual events like we see at 02:20 and 02:40 appear to be individual events, but the cluster at 07:00 and 08:30 look like susteained obstruction from positional apnea (chin tucking). 

Just as PEEP controls oxygenation, it is EPAP that prevents obstructive apnea. Your pressure support will work as long as your airway is open, but these charts suggest that you continue to have obstructive events where ventilation is not possible. Higher EPAP addresses two concerns, keeping the airway patent and improved oxygenation.  Your need for PS may be variable if you are using ST-A (AVAPS) mode. So far I have no background of your medical condition(s) that require you to use ST-A and I don't know the settings of your machine other than EPAP, IPAP and BPM.  Knowing the mode, and whether there is a minimum and maximum IPAP as well as other settings would be helpful.  Also, your machine is capable of dynamic pressure support and targeting aveolar ventilation, and it does not appear those capabilities are being used, rather your "consultants" are using a dumb fixed pressure scheme and may or may not understand the best approach...certainly your results suggest this.  Why aren't you on supplemental oxygen?

[airbusA346]

What I see in your resscan results are many places where tidal volume and minute vent are very low and suggest a possible obstruction.  Higher EPAP may keep the airway open, but I think you should perhaps consider whether a positional apnea may be occurring that would be better treated with a soft cervical collar.

If you don't already have it, the new version of Sleepyhead may work with your VPAP ST-A http://OSCAR Official Download Page ----> CLICK HERE ./testing/1.1.0/  I think being able to see the flow rate could be very helpful.

I believe they want to maintain the big PS, because every time they have increased my IPAP they have increased the EPAP by the same amount.

As I said, PS increases ventilation, but EPAP increases oxygenation.  Your ResScan charts show your tidal volume is often over 1000 mL and minute vent is between 15-20 L/min when things are going well. The problem is it drops off significantly suggesting apnea. Individual events like we see at 02:20 and 02:40 appear to be individual events, but the cluster at 07:00 and 08:30 look like susteained obstruction from positional apnea (chin tucking). 

Just as PEEP controls oxygenation, it is EPAP that prevents obstructive apnea. Your pressure support will work as long as your airway is open, but these charts suggest that you continue to have obstructive events where ventilation is not possible. Higher EPAP addresses two concerns, keeping the airway patent and improved oxygenation.  Your need for PS may be variable if you are using ST-A (AVAPS) mode. So far I have no background of your medical condition(s) that require you to use ST-A and I don't know the settings of your machine other than EPAP, IPAP and BPM.  Knowing the mode, and whether there is a minimum and maximum IPAP as well as other settings would be helpful.  Also, your machine is capable of dynamic pressure support and targeting aveolar ventilation, and it does not appear those capabilities are being used, rather your "consultants" are using a dumb fixed pressure scheme and may or may not understand the best approach...certainly your results suggest this.  Why aren't you on supplemental oxygen?

I personally wouldn't want to start wearing a collar  

Flow Rate for last night.

   

My VPAP doesn't have AVAPS.  According to the clinical manual it has CPAP, S, ST, T, and PAC modes.  I'm using ST.  There's no min and max IPAP.  It is a fixed IPAP and EPAP.  From comparing the Lumis 100 VPAP ST and ST-A, the A appears to stand for 'Alarms'.


When I was switched from APAP to VPAP for noctural hypoventilation I don't think oxygen levels were an issue back in March.  With me reporting the light headedness/dizzy/spaced out feeling to them a few months ago.  I went in for an overnight TOSCA in November to make sure the VPAP was controlling the CO2 levels, which they were satisfied it was (average level was 5.6).  They noticed my oxygen levels were all over the place with the average oxygen level over the whole night equalling 92% (they didn't say how low it went etc).  They increased the IPAP and EPAP by 1 hoping it would improve things, which it didn't and I found it started to cause bloating etc, so I reduced the pressure back down to 26/9.  They sent me one of their own oximeters last week, which they should get back tomorrow for the consultant to look at.

I have Cerebral Palsy, Right Sided Hemiplegia, Hydrocephalus, Scoliosis, OSA (Mild) and Noctural Hypoventilation.  I was born 11 weeks early and suffered respiratory distress syndrome.

[airbusA346]

I don't know why I'm not on additional oxygen, and I'm not sure if that will be their next course of action, but I have thought that it might be needed before I've done my own oximeter tests, because it has felt like the VPAP hasn't been enough, due to still feeling pretty tired/fatigued and un-refreshed.

I have been pushing them to also recognise that I feel breathless and suffer from low oxygen levels during the day too. When I used my oximeter (CMS50I which is worn on the wrist) the other day while driving, my oxygen levels were in the 70-80%.

[Sleeprider]

Your medical conditions are consistent with using ST and ST-A approaches to resolve hypoventilation.  The problem is that the constant use of high pressure support suppresses spontaneous breathing, as evident from your 1% spontaneous trigger rate. The ST uses a brute-force pressure support to cause breaths to be supported, and this is most appropriate for restrictive lung diseases (COPD).  On the other hand, you have a neuromuscular weakness that needs supplemental pressure support part of the time.  The ST-A includes an algorithm called iVAPS which is a volume assured pressure support scheme with much more intelligence than ST mode offers with fixed IPAP/IPAP. Below I have attached a basic explanation of iVAPS, the iVAPS titration protocol, and you can compare it to the ST titration protocol (dumb bilevel with backup).  This link and image explains the capabilities of your machine, and the second link is the titration protocol with more details on application and setting the pressures. 

In my opinion, your "consultant" is not playing with a full deck and has no idea how to get the most out of the machine you have been dispensed. Furthermore, your oxygen levels do not unambiguously point to a need for supplemental oxygen, and that is the simplest of all solutions to implement. I realize your options in the UK are limited, but you deserve a bit more expertise.

https://www.resmed.com/us/en/healthcare-...0-sta.html 
https://www.resmed.com/us/dam/documents/...er_eng.pdf

[airbusA346]

Your medical conditions are consistent with using ST and ST-A approaches to resolve hypoventilation.  The problem is that the constant use of high pressure support suppresses spontaneous breathing, as evident from your 1% spontaneous trigger rate. The ST uses a brute-force pressure support to cause breaths to be supported, and this is most appropriate for restrictive lung diseases (COPD).  On the other hand, you have a neuromuscular weakness that needs supplemental pressure support part of the time.  The ST-A includes an algorithm called iVAPS which is a volume assured pressure support scheme with much more intelligence than ST mode offers with fixed IPAP/IPAP. Below I have attached a basic explanation of iVAPS, the iVAPS titration protocol, and you can compare it to the ST titration protocol (dumb bilevel with backup).  This link and image explains the capabilities of your machine, and the second link is the titration protocol with more details on application and setting the pressures. 

In my opinion, your "consultant" is not playing with a full deck and has no idea how to get the most out of the machine you have been dispensed. Furthermore, your oxygen levels do not unambiguously point to a need for supplemental oxygen, and that is the simplest of all solutions to implement. I realize your options in the UK are limited, but you deserve a bit more expertise.

https://www.resmed.com/us/en/healthcare-...0-sta.html 
https://www.resmed.com/us/dam/documents/...er_eng.pdf

Just had a look in the Clinical menu... there's no iVPAPS on the Lumis 100 VPAP ST-A.  It is mentioned on the Lumis 150 VPAP ST-A on the Resmed site though.

[Sleeprider]

I'm not up on the international models...too bad, and still a better solution. Make sure you get an oxygen bleed adapter and generator. Until your consultant sorts things out it will at least help.

[airbusA346]

I'm not up on the international models...too bad, and still a better solution.  Make sure you get an oxygen bleed adapter and generator. Until your consultant sorts things out it will at least help.

It would cost me a minimum of £600 to do that (buy a used concentrator) and probably £1000+ for a new one.

Hopefully I won't have to to wait long, because the hospital should get the oximeter back tomorrow and the technician said they are working tomorrow so will make the results available to the consultant asap.  It would be nice if they came up with some solution before the New Year seen as the rapid response team are supposed to be dealing with it.