ASV & Encore Pro - a question - edited w ans.

[JDS74]

I track my therapy using Encore Pro and have noticed that on most nights the reported Tidal Volume value reported ends in 0. The ratio between the two types is about 2/3 with zero and 1/3 with a fraction.
For example, a number like 660, 750, etc. A few nights I get a numbers like 779.2 or 732.6

Given what is going on, I would expect most (more than 90%) of the numbers to look like the latter and not the former.
Is this a data error within Encore Pro or is it just reporting to the nearest 10 mL most of the time?

Just curious.

Edit: Here are the detailed numbers for the night with the 732.6 Tidal Volume:
CA - 3.6
OA - 0.0
H - 6.6
FL - 0.3
VS - 0.6
AHI- 10.2
PTB % 65.8
Breath Rate 14.4
Minute Vent - 11.1

[bwexler]

I think I am using the same machine PRS1 DS960TS ASV.
I don't know enough about tidal volume to even look at my own numbers yet.
I would be concerned about AHI over 10 and PTB under 70%.
My AHI is usually under 3 and often under 1.
My PTB is usually in the high 90% range with spikes down to 80% occasionally.
I would suggest you check your machine settings against your titration recommendations and then with your sleep doctor.
I would also look at your large leaks, that might be scewing all of your numbers.
I know my leaks have been more of an issue since I replaced my S9 Autoset with the ASV.

[JDS74]

Most nights my leak rate is pretty flat and averages around 35-40.
My settings are the same as they have been for the last six months.
My sleep doc thinks the PTB% numbers are interesting as does my neurologist (a former sleep doctor)
When I first started last fall, the PTB% were hovering around 90% but they seem to be drifting down.

My back up rate is set to auto and it seems to react to some instability in my breathing rate. I think that accounts for the variability in PTB% values.

[bwexler]

I am not sure the numbers you are looking at are even relevant since they are averages

My Tidal Volume Average in Encore was 400.0 so can see several values below from the SleepyHead 0.9.5 which now works with the 960 series machines and I recomend you try it.
Both Encore and SH show the graph which provides a more detailed view of what is happening.
Now that I have looked I still have no idea why Encore sometomes shows answers out to 1 decimal and other times rounds to the 10s position. I suspect a bug.

I would definitly run both programs and compare the data I was concerned with Like I did today. Most of the averages matched perectly the graphs seem to offer more detail in SH especial if you zoom in or adjust the peramiters of each graph, which you can not do with Encore.


Event Breakdown

Statistics
Channel Min Med 95% Max
EPAPExpiratory Pressure (cmH2O)
W-Avg: 7.03 6.60 6.90 7.80 8.00
IPAPInspiratory Pressure (cmH2O)
W-Avg: 9.01 8.00 8.70 10.90 15.50
PSPressure Support (cmH2O)
W-Avg: 1.98 0.90 1.70 4.00 8.60
Pat. Trig. BreathsPercentage of breaths triggered by patient (%)
W-Avg: 99.30 84.00 100.00 100.00 100.00
Minute Vent.Amount of air displaced per minute (L/min)
W-Avg: 6.63 6.00 6.00 8.00 12.00
Resp. RateRate of breaths per minute (Bpm)
W-Avg: 16.44 12.00 16.00 18.00 20.00
Leak RateRate of detected mask leakage (L/min)
W-Avg: 5.69 0.00 0.00 29.00 35.00
Total LeaksDetected mask leakage including natural Mask leakages (L/min)
W-Avg: 39.56 26.00 37.00 68.00 89.00
SnoreGraph displaying snore volume (??)
W-Avg: 0.04 0.00 0.00 0.00 3.00
Insp. TimeTime taken to breathe in (seconds)
W-Avg: 2.31 0.66 2.40 2.86 8.40
Exp. TimeTime taken to breathe out (seconds)
W-Avg: 1.23 0.26 1.06 2.12 4.52
Tidal VolumeAmount of air displaced per breath (L/min)
W-Avg: 401.61 330.00 380.00 540.00 760.00
Machine Settings

Pr. ReliefPressure Relief Bi-Flex x3
HumidifierHumidifier Setting x5

[JDS74]

Here is a more normal night's data for me.
Note that the Tidal Volume is "rounded" off to the nearest 10 mL instead of being more precise.
I does seem to be some sort of calculation error in Encore Pro.

Early on in my ASV use, my Tidal Volume averaged about 650 mL and now is hovering about 715 or so.
Since I have a basal atelectasis in one lung, I am speculating that the extended periods of ventilator mode with the pressure swinging between 10 cm H2O and 25 cm H20 with each breath could be having a similar effect to IPPB treatment.
Just supposition and I will take it up with my pulmonologist.

The leak line is typical for me. With an average pressure of about 15 cm H2O, my normal mask leak rate per Fisher-Paykel should be 43 L/min. Accounting for manufacturing variations my leak rate average of 38 L/min looks pretty good.

[shortcake]

Hi JDS74, it's been a while!

I notice the same thing about the rounding. Most (I'd say 75 - 90%) of nights will have tidal volumes such as 400, 420, 430, and then very rarely I'll get a 423.5. I've noticed that for MV and RR too (although it seems to round to the nearest whole number, i.e. RR was really 8.6 but Encore reports 9.) I wonder if on the days when tidal volume is "rounded", the others are also rounded, and vice versa, such that on the more "precise" days, all the figures would be a bit more precise (i.e. MV of 4.2 instead of 4.0 and RR of 8.6 instead of 9.0).

Do you upload your data every day? Maybe only the latest night has the more "precise" values while the older days get rounded? I really have no idea why it happens, but I definitely prefer the more "precise" data since I pay more attention to nights when my RR dips lower than 9.

[JDS74]

Hi shortcake,

I download every day. Just a little OCD about looking everyday.
I hate not having the wave data in case I want and look more closely at some event.

I did look at the question of precision following across variables and usually, but not all the time, precise days are precise everywhere. But sometimes not - unless it is just chance that the Tidal Volume happens to be precisely at a 10 mL number when the rest of them show to the 10th.

Do you notice that Hypopneas are all over the place? If I ignore hypopneas, my AHI is consistently below 2.0.
I also find that I feel much better when my PTB% stays above 90%.

This ASV thing is quite a ride.

[JDS74]

shortcake

I took a closer look at those nights with rounded Tidal Volume numbers that ended in other than 0 and found that the few I checked had split nights. I woke up in the night and turned the machine off for some reason so that the recording showed tow sessions. All of those I checked with fractional values were that way and all the ones "rounded off" were single sessions. so, perhaps each session is rounded and the final number is the calculated from the two different values. Say for example, the sessions were 2.2 and 4.1 hours with 640 mL for the first session and 650 mL for the second.
Then the calculation would be (2.2*640 + 4.1*650)/(2.2+4.1) or 656.8.

Encore Pro provides no mechanism for looking at Tidal Volume for part of a night so this is just speculation on how the software actually works.

Just an observation.

[JDS74]

I just did a new experiment. Having found that split nights correlated with fractional reporting, I turned my machine off this morning, waited just a little bit, turned in back on (auto on) and took 10 breaths and turned it back off.

Tidal volume reported at 780.7 - who would have thunk?

It looks as if any split in therapy during a single reporting period causes a slight change in the method of calculation and the rounding is eliminated.

For this short "extra" breathing period, the BPM is still rounded.
Tomorrow, I'll do a longer second session - perhaps a full minute to see it that has any effect.