ResMed VPAP III ST Algorithm

rogelah wrote:Color me confused. The manual says the RR and VT are a 5 minute moving window. There is no graph for RR and VT just median, 95th percentile and max. MV has a detailed graph and is the product of RR and VT. My "gap" is 5 (19 - 14)? There are settings of low, med and hi for Cycle and Trigger but the manual says nothing about them.

Also, there does seem to be a difference in the IPAP at the beginning and ending of the night and I took into consideration the mask leak test at the start.

Is there anything to be gained from tweaking things like Rise Time, IPAPmin, IPAPmax, ???

rogelah wrote:Color me confused. The manual says the RR and VT are a 5 minute moving window. There is no graph for RR and VT just median, 95th percentile and max. MV has a detailed graph and is the product of RR and VT. My "gap" is 5 (19 - 14)? There are settings of low, med and hi for Cycle and Trigger but the manual says nothing about them.

Also, there does seem to be a difference in the IPAP at the beginning and ending of the night and I took into consideration the mask leak test at the start.

Is there anything to be gained from tweaking things like Rise Time, IPAPmin, IPAPmax, ???

rogelah wrote:I finally got 4 nights of a leak with a flat line at zero except at 3 or 4 hours into sleep I wake up with the machine giving me a very high rate of BPM, usually 40 or more BPM. Last night when I woke up and noticed the high rate I looked at the clock and started counting puffs from the machine. I quit at 50. No problem I thought, the machine must be broken (read that as perhaps the software has a bug.) I have a followup appointment today and I'll tell them my observation. I printed out the nights detailed graph and sure enough just before I woke up the rate was at a high of 52. More good news; when they see the detailed graphs showing these abrupt forays into the Mount Everest region of the graph they'll know what to do.

### Rogelah: The problem in this analysis is that the machine doesn't deliver that RR, it is following your breathing. It ONLY takes control when your RR drops below the backup rate. It is you that is hyperventilating. I hear what you are saying but I really doubt that the machine has gone haywire & is triggering/cycling at the speeds you mention. To do that the backup rate would have to be set at 40 or more which is not the case.

First I go to a clerk who hooks up my machine after looking for 5 minutes for the cable and then proceeds to print only summary data. I ask if she is going to print detailed data too and she says no, they only use summary data. I show her where to change to all available data and she tells me that she checked for detailed data and there was none. DUH, if you tell it summary only how does it know to look for detailed data? She says tell the PA and she'll tell the doctor.

So, I talk with the PA and she is looking at the summary data and tells me I'm getting good volume and that's all they care about. I ask her to get the clerk to dump the detailed data. She takes the machine and disappears but is back too quickly and no detailed data. She gets the doctor. I explain all over again about high BPM and he agrees that should not happen. I ask him to print the detailed data for the last 4 days and he ignores me and says he wants to hook me up to the machine. He does and then looks at the settings.

Bottom line, they don't believe me. I think they don't know how to print out the detailed data or are so used to flat straight lines that they think it's useless.

I asked him what I should do if the same thing happens tonight. Call him. The only change he made was to put IPAPmin on 250ms (was 300ms) and change trigger and cycle to MED from LOW. Does he think that will prevent the mountain climbing expedition?

I have a followup in 2 weeks and next time I will take my notebook with the detailed reports or better yet email them.

I tell them about the headaches and the PA tells me that my mask is too tight. She gives me new mask mounting instructions: turn on the machine, put on the mask and then tighten the straps. I tell her I don't mind the fit; she says I have red marks on my face and that causes the headaches I experience several hours after removing the mask. I believe I am a reasonable person but hours after I am off the machine. I wonder if they know what hypercapnia is. I had these headaches when I would wake in the morning before I got involved in SDB.

rogelah wrote:I know it wasn't me. I was having a problem trying to keep up and gave up. It was definitely the machine that was outputting puffs of air at a high rate. I can't breathe that fast when I am basically holding my breath while counting.

When I took several deep breaths it throttled back until I went back to my normal shallow breathing. Then it went back to a very high rate.

It was suggested that next time I turn it off and start over again.

I still think it is the machine. It already had 691 hours on it when I got it. The case does not fit tight where the h2i adapter fits against the blower; it is a little bit loose and there is bruise on the case as if it were dropped.

As for not going that high, I agree with you until it gets to the 3 or 4 hour mark (my guess is heat related) and then it goes up immediately (as viewed on the review screen). The instantaneous (or almost so) rise from around 12 to 15 BPM to 42 or 46 or like last night 52, leads me to believe mechanical failure. If I were the cause, it would be more random based upon my body's response to the therapy.

Because of the design of the machine, it can only go to those RR numbers if triggered spontaneously (a leak may skew the triggering) or if falling below RR backup rate. So if you aren't triggering it something else is & that is a mystery. But, as mentioned, I have charts showing my Vpap III (S & S/T) doing what you describe. I always accepted it was me doing it.

Another thing I noticed since I got the leaks under control is that the AHI components, AI and HI trade places from one day to the next. One day AI is high and HI low and the next HI is high and AI is low. One night there are several clusters spaced evenly over the night and the next, one cluster about 30 minutes after I was asleep and then one or two at the end and one night a couple in the middle third.

I am inclined to think that your condition is the likely culprit here & also tends to lean me a bit towards thinking it is linked to the high RR you are experiencing.

The only thing that is consistent is the inconsistency.

I am a biological entity with an out of whack breathing algorithm, hooked to a robot programmed to deliver air at a rate of 19 cm on inhale and drop to 14 cm to allow CO2 to exit. The robot is measuring my BPM spontaneously and if it falls below 15 it then nudges me with puffs of air at a rate of 15 BPM to hopefully get me back to 15 BPM. It has other parameters to tell it how long to wait for me to begin inhaling and another to tell how long I should be in inhalation. One to determine how quickly it should go from exhale to inhale and a set to determine how gently it should transition for inhale to exhale and exhale to inhale.

That is a good summary of the intention of the Vpap III S/T. But the 'puffs' of air may not be an accurate description, what I think you are describing is the effect rather than the action. By this I mean that the switch from epap to ipap (when you drop below RR backup rate) feels like a puff but is in fact a mechanical shift from 14CMs to 19CMs & at a particular speed (rise time) for the duration of a breathing cycle and as divided up by the I:E ratio. 15 BPM means one full breath is 60/15 or 4 secs. The I:E ratio then splits this into the inhale vs exhale phases that the machine will stick to. The feeling of the speed of rise might make it feel like a puff. ASV machines *DO* put out distinctly short 'puffs' of air & we have discussed possible reasons for that some months back. Bilevels normally don't & the Vpap III S/T & Bipap S/T are normal Bilevels. But if you think about 40 BPM that is one breathing cycle each 1.5 secs with Ipap as a smaller proportion (see I:E ratio setting). Yes I guess that does feel like a puff, BUT, the triggering & cycling when above backup rate, are user driven & not machine driven in a machine where T (timed) is active.

Have I got those correct?

dsm wrote: I am wondering if the hyperventilation shown (when RR goes above say 25) is the cause of the highish tidal flow numbers.

Patients with neuromuscular disorders have rapid shallow breathing secondary to severe muscle weakness or abnormal motor neuron function. The central respiratory drive is maintained in patients with neuromuscular disorders. Thus, hypoventilation is secondary to respiratory muscle weakness.

Weak respiratory muscles can lead to nocturnal hypoventilation

Because ventilatory therapies for people with weak muscles are different than those used for obstructive apneas, it’s important that your physician is highly skilled at analyzing test results

Bach questions the usefulness of polysomnograms for people with muscle diseases because the test “interprets all abnormalities as central or obstructive apneas rather than muscle weakness,” he says — especially when read by physicians unfamiliar with neuromuscular disease.

In muscle diseases, the BiPAP “span,” or difference between the inhalation and exhalation airflow pressures, is typically high to provide greater assistance to the inspiratory muscles and little or no resistance during exhalation.

Resmed's VPAP III S/T web page wrote: IPAP Min ensures sufficient inspiratory time for patients who may cycle to EPAP too early. IPAP Min helps prevent premature cycling to EPAP and allows more consistent delivery of tidal and minute volumes, particularly for restrictive lung disease patients (eg, those with neuromuscular weakness, chest wall deformity, etc.)

-SWS wrote:Here are brief descriptions of Ti max and Ti min:
http://www.resmed.com/us/products/vpap_ ... s&sec=true

Note that Resmed sometimes refers to Ti max as IPAP max. And Resmed sometimes refers to Ti min as IPAP min.

But in that description, Resmed calls for the Ti min parameter ("IPAP min") to help with neuromuscular disease. Specifically, lengthening Ti min can help offset hypoventilation's rapid, shallow breathing cycles associated with neuromuscular disease.

Resmed's VPAP III S/T web page wrote: IPAP Min ensures sufficient inspiratory time for patients who may cycle to EPAP too early. IPAP Min helps prevent premature cycling to EPAP and allows more consistent delivery of tidal and minute volumes, particularly for restrictive lung disease patients (eg, those with neuromuscular weakness, chest wall deformity, etc.)

VPAP II Setup Manual wrote:Set-Up for Different Disease States:

Restrictive Lung Disorders (eg. chest wall deformity, neuromuscular diseases)

Setting TiControl's IPAP Min Time:
1) Measure respiratory rate during ventilation and at rest (see "Measuring Respiratory Rate" on page 59).
2) Refer to the column entitled Restrictive IPAP Min in "TiControl: IPAP Min and IPAP Max time Calculation Guide" on page 58.
3) Set IPAP Min to the value that corresponds to the resting respiratory rate from step 1.
4) If the patient complains that inspiratory time is too long or too short, verify the respiratory rate and IPAP Min setting
-or-
adjust the IPAP Min setting until the patient feels the inspiratory time is slightly too long.
5) Reduce the IPAP Min setting by 0.2 to 0.3 second from the setting in the previous step.


Setting TiControl's IPAP Max Time:
1) Measure respiratory rate during ventilation and at rest (see "Measuring Respiratory Rate" on page 59).
2) Refer to the column entitled Restrictive IPAP Max in "TiControl: IPAP Min and IPAP Max time Calculation Guide" on page 58.
3) Set IPAP Max to the value that corresponds to the resting respiratory rate from step 1.
4) If the patient complains that inspiratory time is too short, verify the respiratory rate and IPAP Max setting.



(my note: below are the table columns relevant to Restrictive disease)

Respiratory Frequency (BPM) / IPAP Max / IPAP Min:
------------------------------------------------------------------
30 / 1.0 / 0.5
29 / 1.0 / 0.5
28 / 1.1 / 0.5
27 / 1.1 / 0.6
26 / 1.2 / 0.6
25 / 1.2 / 0.6
24 / 1.3 / 0.6
23 / 1.3 / 0.7
22 / 1.4 / 0.7
21 / 1.4 / 0.7
20 / 1.5 / 0.8
19 / 1.6 / 0.8
18 / 1.7 / 0.8
17 / 1.8 / 0.9
16 / 1.9 / 0.9
15 / 2.0 / 1.0
14 / 2.1 / 1.1
13 / 2.3 / 1.2
12 / 2.5 / 1.3




Measuring Respiratory Rate:

Respiratory rate should be calculated with the patient ventilated and at rest when possible.

Measure the patient's resting respiratory rate during assisted ventilation. If you think the patient's respiratory rate will decrease during sleep and you are unable to measure it, then estimate the nocturnal respiratory rate and use this figure to determine the IPAP Max and IPAP Min setting. Refer to the section above that most appropriately matches the patient's condition. In some instances, recommended settings may need to be fine-tuned based on patient feedback and/or ongoing clinical assessment.

IPAP:19.0, EPAP:14.0, RR:15, RT:300ms, IPAPmax:2.0s, MAX I:E:1:2, IPAPmin:0.10s

-SWS wrote:Rogelah, is that just a typo regarding the IPAPmin decimal in your tag line?

IPAP:19.0, EPAP:14.0, RR:15, RT:300ms, IPAPmax:2.0s, MAX I:E:1:2, IPAPmin:0.10s

Resmed's recommended range for IPAP min targeting restrictive disease is 0.5s to 1.3s. Again, good luck with your upcoming doctor visit.