Breathing pattern identification, Flow limitations and posture

[Sleeprider]

A number of Resmed machines had defective "pneumatic blocks" or blower motors. They made noises like a dying calf. There are videos, sound clips and posts I could probably find. The best solution would be essentially renewal of the device by a replacement of the motor with pressure calibration and zero run-hours done by Supplier #28. A cheaper option is a $100 motor replacement from Alibaba. The noise does not necessarily mean the performance is impaired, but it is sure irritating and may be the reason this machine was sold. The thing that has me perplexed is, the noise should be consistent between users.

[StuartC]

Sorry, I forgot to reply about the noise last time.  No, it should not make a noise.  Check that the air outlet at the back is properly pushed in.  Check that the humidifier tank is properly pushed in.  Check your hose and mask for leaks, especially at connection points.  If it is a new hose, check the hose for leaks.  Almost a silly thought but check the filter on the inlet too.  Otherwise refer back to the supplier.

[StuartC]

When I first started on iVAPS, it pushed my PS too high, which led to high tidal volumes and suppressed RR.  I felt terrible, but from the high volumes, I think, not the mandatory triggering of insiration.

I am a bit short of time now, and for the next few days, so I have not looked at all of your charts.  Not sure what is behind the low Spont. Triggering but low Spont. cycle will be because you reduced Ti max.  Others may disagree bit I would be inclined to increase that, initially at least, not decrease it.  Focus on trigger before cycle.

S mode operates the same way as CPAP mode with EPR.  In CPAP mode, pressure= IPAP, EPAP = pressure  - EPR.  The only possible reason for ST at this stage could be to provide protection against suppression of RR if PS was set high enough to suppress RR, as happened to me.  This is unlikely with PS at 4.  Even if you did use ST, you would set backup rate low (10 or lower) with iBR off so that it does not interfere except in an abnormal situation.

One idea, which is something I did when I first got my Lumis, is to set it in S mode the same way as his current machine, i.e. IPAP = pressure and EPAP = pressure - EPR.  That allows you to concentrate on time / trigger settings first and then to adjust pressures later.

[SingleH]

Thanks for the dying calf description that hit the nail on the head and I found some videos of the exact noise. Ive gone back to the supplier.
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[url=https://www.youtube.com/watch?v=Pp_xMg3sHlg]https://www.youtube.com/watch?v=Pp_xMg3sHlg


I made a short audio recording of the noise. You can hear at times the uneven sound during his inhalation phase, which doesnt happen with me. I get the dying calf noise, but with a smooth "whining up" and "whining down" I believe this is a reflection of the non linear action of the his rib cage muscles expanding and contracting the chest cavity. About half way through you can also hear the time between the inhalations getting longer and longer before going back to a more regular pace.

https://we.tl/t-mWlFDO2hiv

When I switched to iVAPS the sound of the wailing was more linear, but it was also at lower pressures.

For the next S mode trial I will reduce the pressure settings as Stuart C said and see if I can just get him comfortable and with stable breathing on that mode.

[SingleH]

I noticed the PS went high on the first sessions on IVAPS, so on the second one I reduced that down to the max of 8 and min of 4.

I reset the data and let him do a night on iVAPS, spont trig was 97% and spont cycle was 74%. 7 hrs sleep, Events 3, AHI 2.8.

Wont have any useful info to report back for a few days now anyway until I visit next time.

[Sleeprider]

Based on the sound recording, Resmed normally warrants the repair or replacement of these machines. Good luck.

[SingleH]

Based on the sound recording, Resmed normally warrants the repair or replacement of these machines.  Good luck.

Thanks for the advice. From what I read its just a noise issue but the machine still works fine technically speaking?

I was able to carry out another set of tests today during the day. I used only S mode as per your suggestion and focused on stabilising the erratic breathing behaviour that was going on last week. 

I started off with a lower EPAP and IPAP as trailed last week on S mode of 12 and 6. I used all the same other except for reducing the Ti Min down to 0.5 as you suggested.

I also calculated his respiration rate at rest laying on his back without assistance and that came back around 19-20 although he had a bit of cough and was breathing a little faster than normal.

It was better than last week but still a number of periods where his breathing was erratic and he was taking rapid and short inhalations back to back. The rhythm of his breathing was not that steady and he would have periods of rapid breathing.

With the machine running I tried adjusting the rise time and ti max separately. I first followed the Resmed and NHS titration guide which suggest short rise times for restrictive disorders. This resulted in his breathing becoming more erratic. I then went in the opposite direction and increased it from 300ms to 500ms.  This stabilised the breathing pattern more. I also increase the TiMax. This also seemed to help things become more rhythmical.

Looking at his physical chest movement I could see he still had a bit of a dip mid inspiration. The next step was to increase the EPAP to bring it to 4 below IPAP. Again that seemed to make a visible improvement in his breathing pattern, however the physical mid dip inspiration seemed to be present.

I then started to increase the pressure to see if this would perhaps provide some physical improvement in the chest movement and it did although not completely. IPAP 15 and EPAP 11 seemed to give the best result in this respect and his breathing sounded the most rhythmical however the machine is getting pretty noisy due to the dying calf effect. I noted his respiration rate improved and was about 17 and much more stable. His minute vent was also more stable.

The other observation I noted is when the PS range is bigger the tidal volume is lower and when the PS range is smaller the Tidal volume is a bit larger.
When his tidal volume was lower, his respiration rate was more erratic and higher. When his respiration rate was more stable and slower his tidal volume was a bit higher.

Due to the noise issue, I left the machine on the following settings which he was comfortable with:

S mode
IPAP 13
EPAP 9.0
Ti Max 3.0s
Ti Min 0.5s
Rise Time 500ms
Trigger Very High
Cycle Low

The main issue I observed on is the ridged/rippled top of the respiration wave remained. On iVAPS I noticed much more of the smooth rounded top and also in the earlier part of the s mode trial, while his breathing was more erratic and I had a larger pressure support gap, there seemed to be a few more rounded tops with 12/7 vs 13/9. On IVAPS it was around IPAP 15/16 to EPAP 6/7.

I have attached minute vent and resp rate below.

           

[Sleeprider]

Well the difference in inspiration efficiency is pretty obvious. there is still a snore or flow limit at the peak, but at least there is only one peak. As you increased pressures, the tidal volume also increased (flow per breath), but the minute vent remained fairly constant, so what we see is the respiratory demand is being met at lower breaths per minute as tidal volume becomes more efficient at higher pressure and pressure support. Beyond that, I can't make a lot of conclusions, but this seems far better than where we started. Spontaneous respiration remains in control, and the need for a backup rate is not indicated with these results.

I want to say, you have been very patient with our need for trial and error experimentation to find a solution. I know it's not easy but you're showing a lot of discipline and method in this madness. This actually puts you well ahead of many professionals in the sleep disordered breathing profession. I'm sure you have realized by now that your advocacy and work has been making a big difference in the health and well-being of your dad.

[SingleH]

Thanks for the kind words Sleeprider. 

I understand that trial and error is needed with these kind of things, but of course panic sets in when you see things go wrong. Having the thorough and very detailed advice on this forum from yourself and other members made all the difference. I've learnt a huge amount in a very short time with all information and guidance provided. I can well imagine that some sleep professionals simply wouldnt go into the detail required either due to the time required or cost to the client.

My last comment regarding the peaks, he didnt snore at any point during the trial and I am fairly convinced that the peak that remain is caused by the remaining brief physical dip his chest makes just as he reaches the peak of his inspiration but before exhalation. I was sitting at eye level watching his chest move and was adjusting the settings to attain a steady motion in his chest as he inhaled and exhaled. That was when I ended up going in the wrong direction and tried to achieve this by using a shorter rise time. It did the job in expanding his chest quicker but he also became erratic. Going in the opposite direction with longer rise time, Ti Max and incrementally higher pressures resulted in a smoother movement of his chest. On the final settings I could still see he had his temporary dip but it was drastically reduced. 

I noticed for brief periods during the previous iVAPS trial as the machine was adapting, that the waveform peak smoothed out and got the rounded domes around a pressure of IPAP 15.5-16 and EPAP of 8.5-9. I didnt try these settings yet in S mode due to the calf noise, but I will do. I'm wondering if those higher pressures were "inflating away" the last bit of dip his chest makes and I will observe that in my next test.

I still have not fully grapsed Pressure support so my question is, is 4cm optimal for some reason vs a larger gap and if so is it better to have 16/12 as oppose to 16/9. What I read was that pressure support is directly proportional to tidal volume: As pressure support increases, tidal volume should increase, and vice versa, but in the trials I saw larger pressure support range resulted in small tidal volumes and when I reduced it to 4, his tidal volume inceased.

Anyway today I will be able to have a look at a full nights sleep but I think its clear as to the benefit of Bilevel for him and on that basis I am going to look at purchasing an Aircuve 10 VAuto from second wind if I cant get one locally.

    [attachment=55174]

[Sleeprider]

The almost standard use of 4 cm PS has come from titration protocols that normally start at that pressure, and the simple fact it works for most healthy people. I use 4 cm PS and used to experience more CA events above that. Many of our members use much higher pressure support to treat specific problems related to airway or pulmonary resistance. Your dad is not using bilevel for mere comfort and has an idiopathic (unknown) anomaly in his inspiration that results in a start/stop effect that CPAP cannot resolve. Higher PS is not a surprise, and the need to sync inspiration time with his asynchronous breathing pattern is a unique challenge. We commonly see a need for a PS between 8.0 and 10.0 to resolve central apnea, COPD or neuromuscular disorders, and help a patient obtain a complete breath. At that level, the positive air pressure is mostly replacing any spontaneous effort. It is common sense that an individual with an on/off spontaneous inspiratory effort may require that level of PS. Your efforts through observation and changes seem to be quite effective. He now has a normal inspiratory wave that merely appears flow-limited from time to time, but inspiration is now continuous and I have to presume more comfortable. That comfort feedback is important. The answer to your question then is a PS of around 4.0 is appropriate and most comfortable for individuals with good spontaneous inspiratory effort, and higher PS is generally reserved for pulmonary, neuromuscular or central issues where ventilatory support is needed.