Hello Guest, Welcome to Apnea Board !
As a guest, you are limited to certain areas of the board and there are some features you can't use.
To post a message, you must create a free account using a valid email address.

or Create an Account


New Posts   Today's Posts

[Equipment] Credibility of Contec 50F results vs "Pro" units?
#1
Credibility of Contec 50F results vs "Pro" units?
I got a Contec 50F almost 3 week ago (the version with the single connector for both probe and computer cable).
I find it comfortable enough , and it has been giving me OK results, and OK to download data (with a few annoyances like typing in the user details every time). 

There are a few glitches, where it will give values of 127% O2 and pulse 255 for a few seconds (!), but if those are edited out, the results seem plausible.

For various reasons, I want to take the results to my NHS hospital sleep clinic.

My experience with some health professionals is that they may sneer at the accuracy of the kit.  I'm not too concerned about the absolute accuracy, more the credibility in picking up the frequency and intensity of oxygen level dip events.

I think the kit they used loaned to me last time for their data logging was a Konica-Minolta Pulsox PO-300i.
I note this has ten-times the Oxygen resolution (0.1% vs the Contec 1%), but the same logging interval (1 second).

The one data set they took indicates rather more spike-dips than the Contec results show; there was no overlap between the two bits of kit, so I couldn't cross-calibrate.

I do note their software eliminated the biggest Pulsox recorded dip (which indicated a massive single drop to 70%), so they plainly did not believe the instrument log at that point), but their report does highlight other spikes down 84%.
The mean and median analysed almost identically as 96.6% 

The 20 days of Contec data has never shown such dips; the worst was down to 91% for 9 seconds in the whole time.
A typical mean is 97.3%

Given the above, how would you react if the Contec data were dismissed as poor/irrelevant compared to the Pulsox PO-300i data?
Post Reply Post Reply






Donate to Apnea Board  
#2
RE: Credibility of Contec 50F results vs "Pro" units?
My opinion only. I believe the Contec Data meets my requirements for checking O2 levels during the night. The fact that the readings you had with the Contec compared to the Pulsox on different days doesn't mean that they both weren't reading correctly at the time. If the probe gets knocked around on either device you can get a false reading. But over all I'm sure the Contec gives solid data.
Download SleepyHead
Organize your Sleepyhead Charts
Posting Charts
Beginner's Guide to SleepyHead
Mask Primer
5
Advisory Members serve as an "Advisory Committee" to help shape Apnea Board's rules & policies.

Membership in the Advisory Members group does not imply medical expertise or qualification for advising Sleep Apnea patients concerning their treatment.



Post Reply Post Reply
#3
RE: Credibility of Contec 50F results vs "Pro" units?
Thanks for that, Walla Walla. 
Measurements using both at the same time would be ideal, obviously.
Anyone know if there is anything inherent about the way the Pulsox works that would enable it to see transients that the Contec doesn't/can't pick up?
Post Reply Post Reply
#4
RE: Credibility of Contec 50F results vs "Pro" units?
One possibility is that the Pulsox uses a higher sampling rate - I don't know what each one uses. Actually, your query sent me off on Google for quite a while. I came across a family of chips from Maxim - the MAX3010x series - which can sample at from 50 samples/sec up to 3.2K s/s. So Maxim must see some benefit to the higher rates.
Another possibility is that the Pulsox programmers put more effort into their data analysis routines; certainly Contec didn't put much into their user software...
Post Reply Post Reply






Donate to Apnea Board  
#5
RE: Credibility of Contec 50F results vs "Pro" units?
Thanks for the input, pholynyk. 
Pulsox may use a higher sampling rate, but their data output rate is identical to the Contec @ 1 data point/sec, as I said in the OP. 
The Contec must sample at a higher rate, else it would not be able to display the pulse trace that it does, or be able to identify the pulse BPM in anyway accurately (presumably by peak to peak identification).  
A sample rate of the order of at least 1 kHz would be needed for that.
The Pulsox must be as fast, but would much faster be useful ?

Software is quite another matter. I am using a spreadsheet looking at the .csv file the Contec puts out (1 Hz data point log). But any oxygen level dips faster than one second total duration are not relevant anyway, are they?

There may also be something to account for sensor noise, which could be as basic as just using putting a damping element to smooth out any noise.
Is both the pulse trace and the O2 level derived from the same sensor output? 
If so, the Contec must be adequate to detect relevant transients.

Looking at the much larger peak excursions of the single (poor scan of paper copy) trace I have for the Pulsox, I do wonder if the unit that was used was more questionable than the Contec. 
It was an NHS multi-multi use unit deployed in dozens uncontrolled environments; but as a very expensive "pro" unit it should be able to cope with such ? 
And it probably gets regular re-calibration at horrendous UK taxpayer expense.

Obviously the data was from different nights, but the nature of the dips recorded by the Pulsox are very different to anything recorded by the Contec; that is why I raise the thread.
Post Reply Post Reply
#6
RE: Credibility of Contec 50F results vs "Pro" units?
I have used the CMS-50F, the DynaMed Paramedic unit, and the ResMed Oximetry Kit with the NONIN 3013LP Pulse Oximeter. They all record about the same. I have ruled out some of the outrageous spikes and dips as sensor noise or data drop-outs. I appear to hold my breath when I roll over or stretch in the morning.

I have a heart arrhythmia (PVCs) which precludes accurate measurement of my heart rate with all three units as the algorithm does not correctly account for R-R wave measurements when throwing PVCs. The oxygen data is within 1% of each observation. My HR is indicated at about 30 BPM which my doctor assures me is impossible as anything lower than 40 would trigger pace-making in my implanted defibrillator.

I would not be so concerned about the accuracy of the device, but any extended periods of low oxygenation below 90%. I would also check my red blood cell counts, Hematocrit, and Hemoglobin -- along with Iron -- to see if low oxygen was triggering polycythemia ( the production of red blood cells to compensate for night-time desat events.)

Your discussion should not be about accuracy or comparability -- but the "what if" the data is right, how it can be confirmed, and if supplemental oxygen is indicated. How do you feel? Are you still tired? Is your machine correct for your type of condition or do you need to upgrade to a BI-PAP or ASV?

Because this is the NHS, I am not sure that they have the time or will make an effort to sort your situation unless you push the issue.

Best of luck.
"The object in life is not to be on the side of the majority, but to escape finding oneself in the ranks of the insane." -- Marcus Aurelius
Post Reply Post Reply
#7
RE: Credibility of Contec 50F results vs "Pro" units?
(11-25-2017, 02:15 AM)srlevine1 Wrote: I have used the CMS-50F, the DynaMed Paramedic unit, and the ResMed Oximetry Kit with the NONIN 3013LP Pulse Oximeter. They all record about the same. I have ruled out some of the outrageous spikes and dips as sensor noise or data drop-outs. 
...
The oxygen data is within 1% of each observation. My HR is indicated at about 30 BPM which my doctor assures me is impossible as anything lower than 40 would trigger pace-making in my implanted defibrillator.
Thanks for the helpful input.
It tallies with some other info I found:

From:
pulmolink Commercial Link Removed.

... pretty much all Fingertip Pulse Oximeters on the market, whether "budget" or "top-of-the-range", have an accuracy usually quoted by the manufacturers as + or - 2%. In our own independent testing, it is extremely rare for them to differ by more than 1% 

So there is some evidence from professional suppliers that the results from units like the Contec 50F are sufficiently credible for assessing the degree of apnea.






-----
Moderator Action: Link Removed

To maintain our status as an educational organization, the only commercial links allowed in this forum are to CPAP-related manufacturer websites.  This is stated in the Apnea Board Rules with details given in the Commercial Links Policy section.

-----
Post Reply Post Reply






Donate to Apnea Board  
#8
RE: Credibility of Contec 50F results vs "Pro" units?
(11-25-2017, 02:15 AM)srlevine1 Wrote: a) I would not be so concerned about the accuracy of the device, but any extended periods of low oxygenation below 90%.
...
b) Your discussion should not be about accuracy or comparability -- but the "what if" the data is right, how it can be confirmed, and if supplemental oxygen is indicated. How do you feel? Are you still tired?

c) Because this is the NHS, I am not sure that they have the time or will make an effort to sort your situation unless you push the issue.

Taking those three points:
a), agreed, as I said in my OP:
I'm not too concerned about the absolute accuracy, more the credibility in picking up the frequency and intensity of oxygen level dip events.
With the Contec, I haven't had any periods below 90%, with or without CPAP.  I won't go into why here, but my diagnosis was made in a period of artifice arising from a condition that forced me into an abnormal sleeping position.
It has now been addressed, and I believe the CPAP kit now has little effect and has become the main cause of any nightly disturbance.

b&c) It is those reasons that I have bought the Contec and want to take a load more data to them than the single oximetry set they have for me on one night with the Pulsox.  
My experience has been that they seem little interested in how I feel, just looking at AHI numbers etc reported by the software over a pre-set average time of 6 months.
That meant the data was being averaged before and after my health issue was addressed.  When I pointed this out, I was told by the operative that she "wasn't there to analyse data" - despite what she was doing - averaging over a misleading timescale (6 month average=poor). 
I believe a 1 month average would show that there is no longer a significant problem, I believe.

I'm just anticipating that they may dismiss the Contec data as derived from a low-cost "user" unit, and seek a bit of "armour" should that turn out to be the case.
Post Reply Post Reply
#9
RE: Credibility of Contec 50F results vs "Pro" units?
(11-25-2017, 01:48 AM)windbag Wrote: The Contec must sample at a higher rate, else it would not be able to display the pulse trace that it does, or be able to identify the pulse BPM in anyway accurately (presumably by peak to peak identification).  
A sample rate of the order of at least 1 kHz would be needed for that.
The Pulsox must be as fast, but would much faster be useful ?

I plainly did not have a full brain plugged in when I wrote that. Oh-jeez
A 50 Hz sampling rate would suffice for a pulse up to about 300bpm (allowing 10 points/full pulse waveform), so less onerous than I implied.

But they do both output data log points once per second.
Post Reply Post Reply


Possibly Related Threads...
Thread Author Replies Views Last Post
  New to cpap - struggling to have good results Stex999 3 115 07-26-2021, 04:50 PM
Last Post: Stex999
  How do you use a buckwheat pillow to get the best results? Rcgop 19 942 07-23-2021, 09:00 PM
Last Post: jtech1
  Confusing Sleep Study Results vmarshmellow 19 389 07-21-2021, 11:03 PM
Last Post: SarcasticDave94
  I am thinking of stopping CPAP to see if I get better results. S.L. Ping Beauty 2 145 06-28-2021, 01:15 AM
Last Post: cathyf
  New member - OSCAR results from first full night bkersey129 5 231 06-14-2021, 11:20 AM
Last Post: bkersey129
  [CPAP] First time with APAP, requesting help with interpreting the results deep303 5 248 05-28-2021, 12:40 AM
Last Post: Melman
  Home Sleep Study - Help understanding results dyno890 5 332 05-14-2021, 02:47 PM
Last Post: sheepless


New Posts   Today's Posts






About Apnea Board

Apnea Board is an educational web site designed to empower Sleep Apnea patients.