Small solute clearance is mostly dependent on the blood and dialysate flow rates. It has long been known that the flow rate produced by the type of peristaltic pump used in the blood circuit is influenced by the inlet pressure to the pump. As the pressure decreases, the pump segment of the tubing exhibits incomplete elastic recoil resulting in a decrease in the cross-sectional area of the pump segment. Since the blood flow rate displayed by dialysis machines is determined by the number of pump revolutions and stroke volume, which is the product of the length and cross sectional area of the pump segment, actual blood flow rates may be substantially lower than displayed blood flow rates. This discrepancy can lead to underdelivery of the dialysis prescription. Two approaches have been taken to address this problem. Some dialysis machines now display blood flow rates corrected for the pressure at the pump inlet using a software algorhythm. A new blood tubing set that is less pressure sensitive has been introduced. The pump segment of this tubing set is more elastic and undergoes more complete recoil than traditional tubing set.
No comments:
Post a Comment