14
5 The Calculation Model ZH-L8 ADT
I Uwatec
®
Aladin
®
Pro Ultra
5.1 Description
The Aladin
®
Pro Ultra uses a new decompression
calculation model known as the ZH-L8 ADT. This
model uses eight compartments or “tissue“ groups
with nominal half time periods from 5 to 640 minu-
tes. This model differs considerably from other
models by its consideration of the following addi-
tional physiological processes:
1.Blood perfusion to the body‘s organs is not con-
stant. Skin and muscle tissues are in particular
subject to changes in blood perfusion, depending
on temperature. Changes in blood perfusion to
these organs change their nitrogen saturation
tolerance. The model used by the Aladin
®
Pro
Ultra takes these effects into account and thus
the “skin“ and “muscle“ compartments in the
Aladin
®
Pro Ultra show variable half-time periods
and saturation tolerances.
Decompression information is calculated accor-
ding to the diver‘s individual behaviour and
decrease in skin temperature. The decrease in
skin temperature is based upon the water tem-
perature and the dive time. By considering these
changes in saturation, the time that must be
spent at the surface prior to flying may be consi-
derably increased, depending upon the depth,
time, and temperature of a dive, as well as the
diver‘s behaviour during that dive.
2.The decompression model used by the Aladin
®
Pro Ultra considers nitrogen in both its dissolved
as well as its gaseous phase (microbubbles).
Formation of microbubbles is considered to be a
strong indicator of a high risk of decompression
sickness. The Aladin
®
Pro Ultra model calculates
the formation of microbubbles depending on
various assumed influences in arterial and venous
blood. In normal, slow ascents, microbubbles
form mainly in venous blood. During fast ascents,
microbubbles may also form in arterial blood and
in the body‘s tissues as well. If a particular dive
profile may result in the creation of microbubbles
according to the Aladin
®
Pro Ultra‘s model,
decreased bottom time and/or increased decom-
pression times as well as increased “no fly“ time
will be indicated.
• Microbubbles can form if the diver makes too
fast an ascent, ignores required decompression
stops, or makes repeated ascents during a dive
(yo-yo diving). These microbubbles can form in
arterial blood as well as in the body‘s tissues. If
these microbubbles partially impair circulation,
the rate of gas diffusion and saturation tolerance
for those tissues immediately surrounding this
area of impaired circulation are changed. If requi-
red decompression time will be adjusted in such
a way that already existing microbubbles will stop
growing. Increased decompression time will also
assist those local areas of impaired circulation to
