Patent GB-1437345-A (GB)
Title: Blood oxygenating unit for a blood oxygenator
IPC: A61M1/32
Filed: 1973-06-07
Abstract: 1437345 Blood oxygenating device R C BRUMFIELD 7 June 1973 27239/73 Heading ASR [Also in Division B1] A blood oxygenating unit for an extracorporeal blood oxygenator comprises a multiple tubular array with a number of small-base parallel tubes packed together with bores between 1/16 and 5/6 ins diameter and tube lengths between, 4 and 24 ins, the array having a base and a top, a blood-outlet and -inlet end, a blood-inlet chamber direotly communicating with the blood-inlet end of the array for delivering venous blood thereto, a gas inlet chamber connectable to an oxygenating gas supply the blood inlet chamber and the gas inlet chamber being separated by a manifold plate having gas injection apertures extending therethrough of an average diameter between 100 and 500 microns, the manifold plate being disposed to deliver oxygenating gas into the blood-inlet chamber and discharge bubbles into the blood therein, and a blood defoaming chamber disposed adjacent the top of the tube array. As shown in Fig. 1, a bundle 11 of small diameter tubes 10 is enclosed in a case 16 of circular cross-section, forming a defoaming chamber 29 at one end At the other end are formed a chamber 23 between the ends of tubes 10 and a perforated plate 21, and a chamber 24 between the perforated plate 21 and the closure 25 of the case 16. Blood enters the chamber 23 by inlets 26, and oxygenating gas enters chamber 24 by an inlet 27. The gas passing through the perforated plate 21 mixes with the blood to form a foam. As the foam passes along the tubes 10 to the defoaming chamber 29, oxygen is absorbed by the blood and carbon dioxide is given up. In a first modification, Fig. 4A, not shown, the tubes are of hexagonal, instead of circular, cross-section, and they are formed by extrusion in a block of plastics material. The perforated plate is replaced by a porous plate, and the case 16 covers only part of the tube assembly. In a -second modification, Fig. 4B, not shown, tubes are formed into a rectangular assembly, cemented together and surrounded by a square casing. Blood foam flows within and between the tubes. The turbulence of the oxygen-blood mixture is minimised, so that bubbles of oxygen are formed with slugs of blood between them. The diameter of the perforations in plate 21 may be up to 500 microns, whereas the porous plate may have the equivalent of apertures of 100 microus aperture. The components of the oxygenator may be made of a rigid plastics composition. In use, the oxygenator is primed with transfusion blood, plasma, saline solution etc and blood and gas are introduced by the inlets 26, 27. Blood flow is regulated at a value between 500 ml/min to 7500 ml/min, by varying the number of tubes in the assembly: for low flow rate there may be 95 tubes each having diameters of .10 to 20 inch. The gas flow rate may be 1 to 4 times the blood flow rate. The oxygenating gas may contain 98% oxygen and 2% carbon dioxide. Blood foam is separated in a defoaming chamber to produce gas-free blood. The blood can be regulated in temperature before return to the patient's body. By keeping the turbulence of the blood-oxygen mixture to a minimum, bubbles (72), Fig. 5A, not shown, are formed between slugs (71) of blood. The bubbles rise through the blood, which flows round each bubble as it rises in the tube (Fig. 5B; not shown).