Fresenius Medical Care 2008K Operator's Manual page 99

drip chamber and transducer are connected via a pressure line that runs from the chamber to
venous pressure port (P
pressure and the pressure limits will be activated. If in the course of the treatment, as the
venous pressure increases, a clue to increasing viscosity from ultrafiltration, the alarm limits
will be automatically re-centered and then closed after one minute every 30 minutes during
the treatment. This is intended to keep the lower venous limit as tight as practical.
Increasing the blood pump rate will cause the alarm limits to spread in the appropriate
direction temporarily, i.e., a higher blood pump rate will increase the venous pressure.
Warning! The low venous pressure alarm may not occur with every disconnection or needle
dislodgement. Check all bloodlines for leaks after the treatment has started. Keep access
sites uncovered and monitored. Improper bloodline connections or needle dislodgements
can result in excessive blood loss, serious injury, and death. Machine alarms may not occur
in every blood loss situation.
Note: When the optical detector senses blood, the minimum the lower venous pressure limit
will be set to is + 9 mm Hg.
Transmembrane Pressure (TMP)
The transmembrane pressure (TMP) is equal to the venous pressure minus the dialysate
pressure measured in mm Hg. On the 2008K hemodialysis machine, the TMP is normally
negative. Because the machine uses a closed, volumetric ultrafiltration system, the TMP is
monitored primarily for detecting large shifts in pressure. In certain situations involving
high-flux dialyzers, high blood-flow rate, or low UF rate, the TMP may approach 0 mm Hg.
2008K Hemodialysis Machine Operator's Manual Rev P
) located on the front of the module.
Ven.
The venous pressure is represented in the same way as the arterial pressure,
with the pressure digitally displayed in mm Hg above a corresponding bar
graph. In the bar graph, under normal conditions, the pressure is represented by
a green horizontal bar between yellow bars representing the upper and lower
alarm limits. During alarm conditions, when the pressure rises or falls outside
the alarm window, the venous pressure bar changes from green to red. When
alarm sounds and the blood pump stops, venous line clamp closes, and a
warning message appears in the Status Box.
The alarm limits are set with a time delay for stabilization. Adjusting the blood
pump rate will cause the alarm limits to spread and stabilize before new limits
are established.
For 100 asymmetric limits, one minute after the alarm limits are centered the
lower limit will close to within 20 mm Hg to 35 mm Hg of the actual venous
After a time delay for stabilization, the alarm limits are automatically set at ±60
mm Hg for conventional dialyzers, and ±40 mm Hg for high flux dialyzers. The
alarm window automatically adapts for gradual increases in TMP caused by
increasing blood viscosity resulting from ultrafiltration.
Chapter 4—Monitoring the Treatment
99