Good to know ..... the End Tidal stuff is unchanged.
Matt,
I just cannot believe that he has emphatically written this. It is an absolute crock as proved by even a cursory read of the material he has put in the public domain himself.
I just had another read of the end tidal monitoring thread on RBW where the relevant action starts here:
http://www.rebreatherworld.com/dive...sion-co2-monitoring-split-another-apoc-7.html
It is much more of a comedy than I remember it... easily at the level of the calibration thread that Mr fish linked to, but you need to know a bit of respiratory physiology to see through the rubbish that was posted. Actually, in retrospect, just like in the calibration thread you can see the point where the lights go on and the back-peddling starts, and then it dies. That will be when they went off and started work on the new method which was rolled out a couple of years later.
That thread, in combination with other information appearing in various places provides clear proof of a change in the method. For example, after I (and others) pointed out that the attempt to measure end tidal CO2 directly at the end of the exhale hose could be confounded by mixing of dead space gas and alveolar gas in the exhale hose there are
pages of posts by Alex telling me that I didn't understand dead space, and suggesting that
dead space was not an issue in what he was trying to do (go and have a look for yourselves). Here is one of many potential examples:
Alex Deas on RBW said:
even the plots that Paul published show that the this gas that comes from the deadspace in the mouthpiece is concentrated around the start of exhale and there is little average of that gas over the cycle - the minima in his plots are nice and sharp. The temporal spreading of that (dead space) gas in a short rebreather hose is well under 0.5s, so does not have any significant effect on the peak CO2
Several years later in his fault study report he described a completely new technique for estimating end tidal CO2 from his end-of-hose sensor readings. That description was preceded by this statement:
Alex Deas in the Fault Study Report said:
The Deep Life CO2 monitor in the OR rebreather is controversial and currently unique because it measures Volume Weighted Average Exhaled CO2 and then applies a correction for the effect of the dead space, which is done by determining a tidal volume using a novel method
Hang on, in the first statement he said that
dead space didn't "have any significant effect on the peak CO2", and now two years later they are correcting for it. How can these two statements be reconciled against the claim that nothing has changed? Not to mention the fact that (as I have pointed out before) he provided descriptions of two completely different techniques two years apart. I see they are now trying to sell that difference as one being a more detailed version of the other, but apart from it being
obvious that they are completely different, there is a mass of evidence that this is just a fabrication... such as the fact that Alex stridently argued dead space didn't affect his technique, but then he corrected for it (see above).
The end tidal CO2 measurement algorithm has changed all right. The only thing that hasn't changed is the hubris that prevents admission of an oversight and the fact that an attempt has been made to fix it. I personally think that of itself is a big concern.
I will finish by reiterating what I have always said: I hope that accurate end tidal CO2 monitoring has been nailed.... it absolutely has to be if you are going to base autobailout on it. So far we have seen no proof of that. I will be looking forward to thoroughly testing the system if and when it is released.
Simon M
thus from my consciousness sometime ago but returning to thus post is just sad beyond words. The same posts and PDFs repeated verbatim for years on end. Brad seems to have only one post to make the rest is word salad.