| From: | shadowrn@*********.com (Hahns Shin) |
|---|---|
| Subject: | Body Surface Area (was Re: Tatoo Magic) |
| Date: | Sat Jan 5 14:30:00 2002 |
skin surface area... we talk about percents. That's because there are HUGE
differences in skin surface area based on height, weight, and even race
(Asians tend to have less skin surface area due to their height and general
build, for example). A ball-park number would be "20 sq. feet or so" (This
is a quote from one of my anatomy textbooks, for an "average" human being,
though it fails the physical features of an average person) or about 18000
sq. cm (this is an estimation, not an accurate number). Of course, the
amount of this that is useable by tatoos would be reduced, especially based
on location.
There are several formulas for calculating Body Surface Area (used mostly by
anesthesiologists, oddly enough). The Mosteller is accepted in most places
and goes something like this:
BSA (m²) = ( [Ht (cm) · Wt (kg) ]/ 3600 )œ
In other words, take the height in centimeters, multiply it by the weight in
kilograms, divide by 3600, then take the square root of that number. Take a
5 foot 10 in, 150 pound individual, convert it to metric (177.8 cm, 68.2 kg)
and you get something along the lines of 1.8353 meters squared, or 18353 sq.
cm. This formula is from the New England Journal of Medicine, by the way.
As for actual limb coverage, the closest rule that I have is the "Rule of
9's" which states that each arm is 9 percent, each leg is double (18) that,
the front and back are 18 each, and the head is another 9 percent. The
remaining one percent is taken by the unmentionables, but it usually isn't
calculated on initial examination (just one percent, after all). This is
more a "guess-timation" of burn damage than anything else, but it may be
useful for those of you who want to estimate the actual sizes of tatoos (and
prevent munchkins in your group from going overboard). Incidently, I have a
source (plastic surgery textbook) that says the neck is 1/15 of the total
surface area.
Taking the Sixth World into account, you have to deal with the metahuman
races and tatooing some varying body shape (and therefore, skin) sizes. I
don't forsee any major differences in the body surface area coverage among
the various metahuman races (dwarves are shorter and heavier, in general,
and orcs are bigger and stronger, thus maintaining the body weight to body
surface area ratio). The main problem therefore is with Trolls, since they
have the dermal armor that may interfere with the tatooing process. My way
of dealing with this is simply stating that the "surface area" requirements
of the tatoos are merely guidelines, and that the clever artists can find
ways to "tatoo around" the bony calcified projections. The other application
of the above formulas and estimations would be in constructing custom body
suits and armor. Ruthenium polymer comes to mind.
Hahns Shin, MS II
Budding cybersurgeon
