Design and validation of a diaphragm pump for pediatric CRRT during ECMO.

PURPOSE: Children requiring artificial heart-lung support through extracorporeal membrane oxygenation (ECMO) are at increased risk of developing acute kidney injury (AKI). Continuous renal replacement therapy (CRRT) is the preferred method of treatment in pediatric AKI patients. CRRT devices are noted to provide inaccurate fluid balance (FB) when operated under low flow rates seen in children. We present the design and validation of a novel pump concept to provide accurate pediatric CRRT during ECMO.

METHODS: A diaphragm pump was prototyped with a working stroke volume (SV) of 7 mL. Fluid transport occurs by periodic expansion and contraction of a flexible membrane due to pressure fluctuations of hydraulic fluid contained below its surface. Comparison of intravenous (IV) pumps to the diaphragm pump was conducted in vitro across the range of pressures observed during CRRT in ECMO. The pump was integrated into a CRRT circuit parallel with ECMO and FB accuracy was evaluated.

RESULTS: The pump design improved efficiency of fluid transport, with flow rate errors as low as 
1-5 ml/hr as compared to IV pumps (15-50 ml/hr). The SV of IV pumps increased with source pressure in a nearly linear manner compared to the minimal variation produced by the diaphragm pump. Inclusion of the diaphragm pump in a conventional CRRT circuit with ECMO improved the FB accuracy.

CONCLUSIONS: A novel diaphragm pump concept has been presented for providing CRRT during ECMO in the pediatric population. Improvement of the pump accuracy compared to currently used CRRT pumps was demonstrated via in vitro testing.