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I Introduction
I
3 Calculation Model ZH-L8 ADT
3.1 Description
The Model ZH-L8 ADT (8 compartments with a nomi-
nal half-time periods from 5 to 640 minutes) differs
considerably from other models by the consideration
of additional physiological processes:
1. Blood perfusion of the organs is not constant. Skin
and in particular muscles are subject to
considerable changes of blood perfusion
depending on temperature and workload. A
change in blood perfusion also causes a change
of the saturation tolerance. The model takes these
effects into account. Therefore, skin and muscle
compartments show variable half-time periods and
saturation tolerances.
The necessary decompression times are calculated
according to the workload and the decreasing skin
temperature. The decrease of skin temperature is
estimated based on the water temperature and
the dive time. At the surface, the diver’s physical
performance is lower than during the dive. By
considering the differences in physical performance
the no fly time becomes considerably longer.
2. The model considers inert gas not only in the
dissolved state, but also in the gaseous phase
(microbubbles). Formation of microbubbles is
calculated with allowance for the different influen-
ces in arterial and venous blood. With normal
ascents gas bubbles mainly form in venous blood,
with fast ascents also in arterial blood and on
ignoring decompression stops in the tissues. As
the model calculates microbubbles, those physiolo-
gical processes are reconstructed which actually
occur.
The bubbles on the venous side of the circulation
are carried into the lungs where they change the
arterial nitrogen pressure. This influences mainly
repetitive dives, dives with very long decompression
times and the no fly time.
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