Dialysis Procedure

Procedure

Calibration Procedure

Before starting the experiment, it is first necessary to calibrate each of the four flow meters used in the process. There are flow meters for the flow inlet and outlet of the shell and lumen side. Before beginning, first be sure there is enough liquid for both the lumen and shell side calibration. The lumen side can use either pure water, or pre-made NaCl solution for the calibration. The shell side (dialysate), uses water as a feed. Be sure the dialysate tank is about 75% full and the NaCl tank is about 50% full to be sure there will be enough feed for the calibration.

Once both tanks are filled, the system may be plugged in. The shell and lumen side feeds are controlled by two pumps, respectively. The calibration will first be carried out on the lumen side. Before turning on the pump, be sure to manually plug the shell side outlet located in the back of the unit. This must be done in order to accurately calibrate the flow meters. If both outlets are left open, some liquid mass will leach through the lumen membrane and be unaccounted for. By plugging the opposing outlet, all liquid is forced to flow through one side.

Once the shell side outlet is plugged, the lumen side pump may be turned on and set to 1100. Let the system reach steady state by monitoring both the lumen side inlet and outlet flow meters and waiting for them to stabilize. Once the system is stable, position a graduated cylinder near the outlet of the lumen side located in the back of the unit. Coordinating with other group members, simultaneously begin a stopwatch, position the lumen side outlet into the graduated cylinder, and record the inlet and outlet flow rates read on the two flow meters. Collect the lumen side liquid for 30 seconds. Record the amount of liquid collected. Repeat this process again to obtain two data points for the same pump setting. Repeat the data collection for pump settings of 900, 700, 500, and 300.

Next, the shell side flow meters can be calibrated. Turn off the lumen side pump and be sure to plug the lumen side outlet before starting. Follow the exact procedure as above to calibrate the shell side flow meters, this time collecting liquid from the shell side outlet. Create a calibration curve of all four flow meters by plotting the average flow meter reading vs the average calculated flow rate for each pump setting. A trend line, equation, and R2 value may then be added to each calibration curve.

There are conductivity meters used in this experiments, but they were previously calibrated to give the following calibration equations:

Lumen in: C = 0.9325 × σ

Lumen out: C = 1.0684 × σ

Shell in: C = n/a

Shell out C = 1.0096 × σ

Where C is the concentration of NaCl in g/L and σ is the conductivity meter’s reading in mS/cm.

Experimental Procedure:

Before starting the experiment, make sure there will be enough NaCl solution and water dialysate for the entire duration of the experiment. Once it is verified that there is enough of both liquids, the system may now be plugged in.

In order to gather data points over a wide range of flow rates, the lumen side flow rate will be held constant while the shell side will vary flow rates. Afterwards, the lumen side will be changed to a new constant flowrate and the shell side will again vary flow rates.

To begin the experiment, set the lumen side’s pump to 1100 and the shell side’s pump to 1100. Once the system has reached steady state (all flow meters are stable), record the values of every meter (the flow rate and conductivity of lumen in, lumen out, shell in, and shell out). Wait about a minute and record each of the meters’ readings again for a total of two data points per flow rate. Next, keeping the lumen side’s pump speed still at 1100, reduce the shell side pump to 900. Repeat the above procedure and record all of the meter readings. Repeat the entire process again, still keeping the lumen side’s pump constant at 1100, but reducing the shell side’s pump speed to 700, 500, and 300.

Next, the lumen side’s pump speed may be reduced to 900 and held constant while the shell side again is varied from 1100, 900, 700, 500, and 300, repeating the above procedure for each flow rate.

The entire experiment above will then be repeated for lumen side pump speeds of 700, 500, and 300 to obtain every combination of flow rates for both the lumen and shell side.

Once all data is collected, the two pumps may be shut off and the unit may be unplugged. Any mess made during the experiment should be cleaned up before leaving the lab.