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3 The Calculation Model ZH-L8 ADT
I Uwatec
®
Aladin
®
Sport Plus
3.1 Description
The Aladin
®
Sport Plus 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 minutes. This
model differs considerably from other models by its consideration of the following additional physiological
processes:
1. Blood perfusion to the body‘s organs is not constant. Skin and muscle tissues are especially subject to
changes in blood perfusion, depending on temperature and work load. Changes in blood perfusion to
these organs change their nitrogen saturation tolerance. The model used by the Aladin
®
Sport Plus takes
these effects into account and thus the “skin“ and “muscle“ compartments in the Aladin
®
Sport Plus
show variable half-time periods and saturation tolerances. Decompression information is calculated
according to the workload and decrease in skin temperature. The decrease in skin temperature is based
upon the water temperature and the dive time. By considering these changes in saturation, the time
that must be spent at the surface prior to flying can be considerably lengthened, depending upon the
depth, time, and temperature of a dive, as well as the diver‘s work during that dive.
2. The decompression model used by the Aladin
®
Sport Plus 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
®
Sport Plus model calculates the formation of
microbubbels 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
®
Sport Plus‘s model, decreased bottom time and/or increased
decompression 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 required, no-stop time, decompression time and -depth 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 desaturate with less risk of decompression sickness.
