ALADIN ALADIN AIR Z, Operating Manual, Page: 12 / 86

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3 Calculation Model ZH-L8 ADT
I Uwatec ® Aladin ® Air Z
3.1 Description
The Aladin
®
Air Z uses a 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 dif-
fers considerably from other models by its consideration of the following additional physiological proces-
ses:
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
®
Air Z takes these
effects into account and thus the “skin“ and “muscle“ compartments in the Aladin
®
Air Z show varia-
ble half-time periods and saturation tolerances. Decompression information is calculated according to
the diver‘s individual 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, depend- ing upon
the depth, time, and tem- perature of a dive, as well as the diver‘s workload during that dive.
2.The decompression model used by the Aladin
®
Air Z 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
®
Air Z model calculates the formation of microbubbels
depending on various assumed influences in arterial and venous blood. In normal, slow ascents, micro-
bubbles 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
®
Air Z‘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, both decompression time and RBT will be adjusted in such a way that already exi-
sting microbubbles will stop growing. Increased decompression time will also assist those local areas of
impaired circulation to desaturate with less risk of decompression sickness.