The effects of the structural design of blood purification equipment influenced the amount of bubbles generated of bicarbonate replenisher for hemofiltration

Abstract

Carbon dioxide bubbles are generated in the dialysis circuit when continuous renal replacement therapy (CRRT) is performed using a bicarbonate replenisher for hemofiltration. It is reported that this results in a lowering of the liquid surface level in the venous chamber in ACH-Σ^® (hereinafter, Σ) manufactured by Asahi Kasei Medical Co., Ltd. Therefore, we investigated how the difference in the structural design of the blood purification equipment might affect the amount of bubbles generated in the circuit. Method: We changed the normal circuit (N Circuit) of Σ and created a circuit in which the heater located near the inlet of the fluid replacement pump was bypassed (K-B Circuit) and another in which the scale of the fluid replacement pump was bypassed (J-B Circuit). After performing CHF for 2 hours using the N, K-B and J-B circuits with the fluid replacement flow rate set at 1 L/hr, we measured the amount of bubbles generated in the circuits and collected in the trap chamber. We also measured the inlet pressure of the fluid replacement pump of each circuit. Results: A significantly smaller amount of bubbles was generated in the J-B circuit as compared to that in the N and K-B circuits. The inlet pressure of the fluid replacement pump in the J-B circuit was significantly higher than that in the N and K-B circuits. Conclusion: The results of our investigation suggested that lowering of the inlet pressure of the fluid replacement pump might increase in the amount of bubbles generated in the circuit.