Abstract
The high peak flow velocity of the extremely effective pulsatile monoroller pump (MRP) recently described (Jpn J Artif Organs 17 (3): 1248-54, 1988) precludes its direct use in conjunction with commercially available membrane or hollow fiber type oxygenators. A new hybrid coaxial pump (DUAL PUMP) combining in-series a conventional biroller pump placed upstream the MRP has been developed to solve such shortcomings. The biroller pump propels the blood FROM or THROUGH ANY TYPE OF OXYGENATOR into a small bag type reservoir connected to the inlet side of the MRP. The diameter of both pump head raceways has been calculated so that the biroller pump flow is 10% to 20% higher (overflow) than the MRP flow. A simple mechanical flow mode selector externally placed around the tubings of the circuit between the pumps and the bag reservoir capable to convert the in-series arrangement of both pumps into two circuits in-parallel has been incorporated, thus allowing changing mode of perfusion (pulsatile to non-pulsatile or vice versa) instantaneously. The stroke volumes obtained in the mock circuitare dependent on the internal diameter (ID) of the tubing: a) 18mm ID=122-142ml, b) 15mm ID=80-90ml, c) 12mm ID=45-65ml, and d) 9mm ID=33-35ml. The lowest overflow is obtained with the best matching tube of 15mm ID for which the raceways were originally calculated, and considered to be the most adequate size for use in adults. The ideal pump head tube eleasticity to be used in the MRP is that offered by the MS-MERA PVC tubing.
