Scubapro-uwatec SMART MICROBUBBLE User Manual

MICROBUBBLE MANAGEMENT

Smart

ADAPTIVE COMPUTERS

UWATEC dive computers have long included the Bühlmann
ZH-L8 ADT mathematical model that allows the computer
to adapt to actual diver behaviors and environmental
conditions. The name of the model was derived from ZH ­Zurich where the model was developed, L8 refers to the
number of body tissue groups that the model considers and
ADT is short for ‘adaptive’.

With an adaptive model, if a diver exceeds the prescribed
ascent rate, works too hard, or is exposed to really cold
water, the dive computer may ask the diver to complete a
compensation decompression stop. Another advantage of
the adaptive model is that it allows UWATEC dive
computers to more accurately predict the remaining gas
requirements on deep dives and it provides more accurate
monitoring of the CNS loading for Nitrox divers.

UWATEC has now proven that divers who conduct repetitive
dives even within the standard no decompression limits
produce microbubbles. Microbubbles may be a precondition
for the formation of larger bubbles that can lead to
decompression illness. Microbubbles usually present no visible
symptoms to the diver, but may cause permanent damage.
Divers with a PFO (Patent Foramen Ovale - a hole between
the two chambers of the heart) are particularly susceptible.

With two additional letters, the Bühlmann adaptive model
has been expanded to be called the ZH-L8 ADT MB. This
stands for microbubble, because the UWATEC Smart can
be programmed for microbubble suppression.

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SMART MICROBUBBLE MANAGEMENT

Smart PRO Wrist

Smart PRO
Console

Smart COM

On deeper dives, divers need to carry sufficient gas reserves
to ascend and complete any necessary decompression stops.

The Smart COM displays a Remaining Bottom Time field,
which is an estimate of the time remaining at the current depth
until an ascent must be commenced. Once the ascent
commences, the Smart COM has already included a prediction
of the gas reserves necessary to ascend at the prescribed
ascent rate and complete the necessary decompression stops.
The baseline for the RBT is the “tank reserve value” which can
be set via Smart TRAK in 50 PSI increments between 300 and
1750 PSI. An RBT of 0 means that if an ascent is commenced
at that time and carried out at the correct ascent rate,
respecting all decompression stops, the diver will be on the
surface with approximately the tank reserve left in the tank.

The calculation is based on the diver’s current rate of gas
consumption, temperature and the current tank pressure
and starts 1.5 minutes after the start of a dive. It is updated
every 4 seconds. The computer accurately modifies the
Remaining Bottom Time according to variations in the
diver’s rate of breathing. If the diver is experiencing heavy
exertion, then the RBT is reduced. If the diver is relaxed,
then the RBT is extended.

The accuracy of this calculation is due to the pressure
sensor’s ability to accurately measure a single breath of air.
The accuracy is further enhanced because it considers the
ambient temperature and air pressure is affected by ambient
temperature variations. This is particularly useful for a diver
who is diving through thermoclines.

After a dive, the data from the Smart COM can be
downloaded to Personal Computer with the Smart TRAK
software that is included with the Smart COM. The actual
rate of breathing is displayed in cft/min, as is the workload
level. Also displayed is microbubble buildup and temperature.

At the conclusion of a dive the Smart COM displays the
“differential pressure”. This value represents the gas that is
consumed during the dive. Also displayed are any warnings
that may have occurred throughout the dive, in this
example both RBT and Workload warnings are displayed.

GAS CONSUMPTION

• Displays tank pressure - psi (bar)

• Remaining dive time at current depth (RBT)

• User adjustable tank reserve warning

•

Low air warning

• Quantity of air used

• RBT is less than 3 alarm

• RBT less than 0 alarm

The Smart COM displays the cylinder pressure, calculates and displays the
Remaining Bottom Time (RBT), and warns when RBT is less than 3 minutes.

The Smart COM considers the effect that exertion has on the decompression
schedule. When the lung symbol appears the diver should relax the breathing rate.

Earlier mathematical models assumed a mean workload
output of 50W. With the ZH-L8 ADT MB model, even at
level 0, if workload is increased to 85W then on a 50ft
(15m) dive the ascent time is increased from 30 to 60 mins.

W ORKLOAD

With the Smart TRAK software that is supplied with the
Smart COM, the sensitivity of the workload setting can be
set by the diver according to their own level of fitness.

Some dive computer models assume an average workload
throughout the dive. However, an unfit diver, for example,
who is working hard at depth will breathe more heavily.

Even fit divers sometimes find themselves working hard in
situations such as swimming against a current or removing
an anchor that is stuck under a rock.

In such high workload circumstances the diver can absorb
more nitrogen, particularly in the muscle tissue groups.
This additional uptake of nitrogen, in turn, is exposing the
diver to a greater risk of microbubble formation and the
possibility of decompression sickness.

The Smart COM understands that different divers have
different levels of fitness and different levels of exertion on
different dives. The Smart COM can actually influence a
diver who is working hard, to reduce the level of exertion,
by relaxing and breathing more slowly.

The Smart COM can do this because it is accurately
monitoring the diver’s rate of air consumption and changes
in the rate of air consumption.

If a diver persists in working hard at depth the Smart COM
may ask the diver to complete an additional
decompression stop.

With Smart TRAK the sensitivity of the breathing rate
warning is adjustable according to the diver’s level of fitness.

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SMART MICROBUBBLE MANAGEMENT

• High breathing rate alarm (High Air Consumption)

•

Adaptive decompression model Bühlmann ZH-L8
ADT MB

• CNS clock is adjusted by O

2

uptake according to

workload

• User adjustable air workload warning

• Workload is displayed in Smart TRAK