arp@uwvax.UUCP (Andrew Pleszkun) (08/23/85)
What follows is some information on both DAN (Divers Alert Network)
and the current Decompression meters.
DAN was founded in 1980 to serve as a central emergency network
for dive accidents. Its primary task is as a nationwide
communications network to help divers and their physicians arrange
consultation, transportation, and treatment anywhere in the US.
The emergency number (24 hrs per day) is 1 - (919) 684-8111 and
is staffed at the Duke Medical Center in Durham, NC.
Originally supported by NOAA grants, in 1983, DAN became a self-supported
(by memberships and donation) organization when it lost funding via
Reganomics. DAN in recent years has in fact also served as a
dive accident reseach tool, by collecting sport diving accident statistics.
It also received thousands of calls from divers asking questions
about medical conditions and diving, dive first aid, etc.
For this, a non-emergency number was established which operates
9am - 5pm (eastern time) - 1 - (919) 684-2948.
Membership dues are $15 ($10 renewal) for which one receives the
newsletter Alert Diver, and the DAN Manual - an excellent dive
injury signs, symptoms, first aid, treatment manual.
To join send $15 to DAN
Box 3823
Duke Univ. Medical Center
Durham, NC 27710
Decompression Meters - and Dive Tables
One of the consultant on the development of the Edge by Orca Ind.
was Karl Huggins from the Michigan Sea Grant Program, U of M.
Was follows is some of the details of computer work done by Mr. Huggins
and staff associated with the US Navy Dive Tables.
The US Navy modeled the tissue nitrogen absoption and removal in the body
by an exponential equation. The Navy modeled 6 tissue groups with
nitrogen absorption half-times of 5, 10, 20, 40, 80, and 120 minutes,
with saturation limits (M0 values) of 102, 85, 67.5, 54.5, 47.5, and
43 respectively (These are the new M0 values as determined by Karl Huggins).
The total tissue pressure Pt is expressed by the equation:
Pt = P0 + (Pa - P0)(1 - e ** (-.693t/T.5)
where P0 is initial tissue pressure
Pa is ambient partial pressure of nitrogen
T.5 is the Tissue group, half-time.
It is these equations (6) and the corresponding limits (M0) that the
Navy used to calculate the no-decompression limits. One of the
problems with the tables is that for repetitive dives, the group
designations are only based on the 120 minute tissue group.
To the Edge, the Edge has the above (safer M0 values) and equations
and constantly is calulating the pressures in all six tissue groups.
It also calculates the decompression time from this. It "allows"
one to make multi-level dive at a continuous depth range.
The DECO-Brain, as I understand used the Swiss Navy Dive tables
as its basis which is much more conservative the the US Navy Tables.
For a copy of Karl Huggins report send $0.40 to
Michigan Sea Grant College Program
Publications Office
2200 Bonisteel Blvd.
The Univ. of Michigan
Ann Arbor, MI 48109
The report number is MICHU-SG-81-205
It includes a new more conservative no-decompression table.
All views expressed are my own.
I am a YMCA Instructor.