Transmembrane Pressure (Tmp) - Fresenius Medical Care 2008T Operator's Manual

Chapter 4—Monitoring the Treatment

Transmembrane Pressure (TMP)

The transmembrane pressure (TMP) is equal to the venous pressure minus the dialysate
pressure measured in mm Hg. On the 2008T 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.
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.
Warning! After starting dialysis, determine whether a stable TMP has been obtained and
whether it corresponds to the ultrafiltration coefficient (KUF) of the dialyzer. TMP must be
closely monitored with the alarm limits. The TMP may not change substantially during UF
errors when high permeable dialyzers are in use. A fluctuating TMP, except in cases of
single-needle dialysis, may indicate a malfunction in the balancing system. A high TMP
may indicate a leak in the dialysate side of the system. Frequent Fill programs may indicate
air in the balancing system. Some, but not all, UF errors can be checked by measuring the
volumetric accuracy of the UF pump via the Fluid Sample Port using a graduated cylinder.
If the cause cannot be corrected quickly, discontinue treatment.
Note: The approximate expected TMP can be calculated from the dialyzer blood
ultrafiltration coefficient (KUF) and the UF rate:
TMP = (UF Rate)/(KUF)
Warning! When using highly permeable dialyzers, the dialysate side is frequently above
atmospheric pressure (because of the venous pressure and low TMP). Although uncommon,
any dialysate fluid leak from the dialysate side of the system will add to the intended
ultrafiltration rate. Observe the system for fluid leaks and discontinue treatment if you are
unable to correct any fluid leak quickly.
104 2008T Machine Operator's Manual P/N 490122 Rev N