ZH-L8 ADT Calculation Model
The Monitor 3 Air uses a new calculation model known as the ZH-L8 ADT. This model uses eight compartments or "tissue" groups with half-times ranging from 5 to 640 minutes. This calculation model is based on the most current research conducted by the late Dr. A.A. Buhlmann. Most computer decompression models only take into account time and depth; the Monitor 3 Air model also factors in other physiological factors, including tempera- ture, breathing rate and workload.
Workload and Temperature
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 workload. Changes in blood perfusion to these organs change their nitrogen saturation tolerance. The ZH-L8 ADT model takes these effects into account and thus the "skin" and "muscle" compartments in the Monitor 3 Air have variable half-time periods and saturation tolerances.
Decompression information is calculated according to the diver's individual workload and decrease in skin tempera- ture. 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
Section 6: Reference
surface prior to flying can be considerably lengthened, depending on the depth, time, and temperature of a dive, as well as the diver's workload during that dive.
Microbubble Formation
The ZH-L8 ADT model considers nitrogen in both its dissolved and gaseous phase (microbubbles). Formation of microbubbles is considered to be a strong indicator of a high risk of decompression sickness. The model calculates the formation of microbubbles depending on various assumed influences in arterial and venous blood. During normal, slow ascents, microbubbles form mainly in venous blood. During fast ascents, microbubbles may also form in arterial blood and the body's tissues. If a particular dive profile results in the formation of microbubbles, decreased bottom time and/or increased decompression times, and increased wait-to-fly times, will be indicated.
Microbubbles can form if the diver makes a fast ascent, ignores decompression stops, or makes repeated ascents during a dive (yo-yo diving). These microbubbles can form in arterial blood and body tissues. If these microbubbles partially impair circulation, the rate of gas diffusion and saturation tolerance of surrounding tissues are changed. If required, both decompression time and remaining bottom time will be adjusted in such a way that already existing microbubbles will stop growing. Increased decompression
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