Mailing List Archive Mailing List Archive
Frank, Just some nitpicking - 1) You stated: >Fast forward to Buhlman: Buhlman decides that Haldane (and lots of >post-Haldane work, especially Workman) is not quite right; he seeks a >better and more general model. Buhlman begins from first principles, >looking at determining 1/2 times and permitted saturation levels for >different real body tissue types (blood, skin, joints, etc). Buhlman >also revises the original model to accomodate two coefficients per >halftime (compartment) which control the accepted supersaturation >(Workman's M-values, generalized from Haldane's 1.58, are replaced now >with pairs of coeffs). In the beginning, Buhlman uses his >tissue-derrived coeffs. But as his model development progresses, he >switches to determining the half times (compartments) and >corresponding coeff pairs via empirical studies involving human divers >in a wet chamber. >So, looking at the outcome of Buhlamn's research, what do we have in >the way of a model? > - Gas uptake and elimination are exponential. > - Gas elimination is at a different rate than absorption. > - Coeffs for He are different than N2. > - Acceptable saturation levels are now dependant on two > coeffs, in a slightly more complex formula. > - Half times are different, with much longer half times on the > long end. Please read the work of Buhlmann. Gas elimination and and absorbtion is modeled exactly the same (mirror images) in an exponential manner. The US Navy model (Haldanian) also utilizes 2 factors, both the "M" value and the "delta-M" values, much like Buhlmann does. >So fast forward again, this time to DCIEM. UDT (commissioned by >DCIEM) undertakes building a new, safer deco model to generate a large variety of tables. UDT only markets the DCIEM tables. They were not the developers of the DCIEM tables. The DCIEM tables evolved from work done by Kidd and Stubbs back in the early years trying to develop a mechanical diver carried decom computer. They came up with the concept of 4 compartments, linked in a serial manner. This (with much tweaking) produced a diver carried computer that produced decompression profiles that were acceptable in risk and rate of DCI. The latest DCIEM tables were computer generated by a modern version of the Kidds-Stubbs model, still utilizing 4 compartments linked in a serial manner. The main advantage of the DCIEM tables is that they were extensive doppler tested (on human subjects) in a cold, high workload environment. Serial gas movement is probably a component in gas uptake and elimination (tissue to tissue interchange/exchange), but the fact remains, that arterial blood is delivered to the tissues in a parallel fashion (and this is probably the major route of in gassing and outgassing). Hate to rain on your interesting and lengthy post, but it would be best if you would do a little extra research before making some of your statements. John Submariner Research, Ltd. (johncrea@de*.co*)
Navigate by Author:
[Previous]
[Next]
[Author Search Index]
Navigate by Subject:
[Previous]
[Next]
[Subject Search Index]
[Send Reply] [Send Message with New Topic]
[Search Selection] [Mailing List Home] [Home]