Heat Exchanger for Artificial Heart and Lung Devices

This invention relates to a heat exchanger for use with artificial heart and lung devices.

In the case of circulating the blood of a patient through an artificial heart and lung device in a surgical operation on his heart, the temperature of the blood generally tends to drop while it is circulated through the circuit outside the patient's body because the temperature in the operation room is lower than the body temperature thereof. In order to heat the blood to the body temperature again and return it to the patient's body, it is essential to provide a heat exchanger.

As for heat exchangers for use with artificial heart and lung devices, there have heretofore been employed two types. One type includes one length of a blood transport tube within a tubular shell, and the other type includes a spiral blood transport tube mounted within a tubular shell in which a heating medium is introduced to heat the blood. These devices are, however, disadvantageous in that since the surface area through which the blood can receive the heat from the heating medium is small, the heat exchanging efficiency obtainable thereby is low. In order to eliminate the above-mentioned disadvantage, the applicant of the present invention devised and filed a Japanese Utility Model Application No. 119,356/1947 in which a large number of elongated tubes are mounted in parallel within a tubular shell to improve the heat exchanger efficiency. This device can provide a high heat exchanging efficiency since the surface area through which the blood can receive the heat from the heating medium is large, and can be put satisfactorily into practical use. However, it has a room left to be improved, because it is not provided with means for removing air bubbles produced in the blood.

In artificial heart and lung devices, it is necessary to add some amount of oxygen to the blood passing therethrough by spraying oxygen to the blood. Therefore, the passage of the blood oversaturated with oxygen inside the heat exchanger allows the oxygen in the blood to expand by heating thereby producing oxygen bubbles. Conventional devices are disadvantageous in that since they are not provided with means for removing such air bubbles, it is absolutely necessary for a doctor to frequently remove the air bubbles to avoid complications resulting from the bubbles.

Therefore, the object of the present invention is to provide a heat exchanger for use with artificial heart and lung devices having an improved heat exchanging efficiency by providing a bubble remover for removing air bubbles produced in the blood during the operation.

The present invention is characterized in that a large number of elongated tubes through which the blood is allowed to flow are arranged in parallel within a tubular shell, and the space on the side of the outlet for receiving the blood is divided into an inner chamber and an outer chamber by a baffle plate so that the blood can first be accumulated in the inner chamber to remove air bubbles in the blood, and then circulated in outer chamber thereby enabling the blood free of air bubbles to be introduced into the patient's body.

The present invention is advantageous in that it can provide a high heat exchanging efficiency, and also oversaturated oxygen in the form of air bubbles in the blood can be substantially removed. Further, the present invention is advantageous in that it can provide a disposable heat exchanger of a simple arrangement in place of conventional devices which require considerable manpower for flushing, assembly operation and sterilization etc., for each repeated use.

Other objects, features and advantages of the present invention will be readily apparent from the following description taken in conjunction with the accompanying drawing.

FIG. 1 is a partially cut-away perspective view of the present invention.

FIG. 2 is a cross-section view of outlet side cap of the present invention.

In the drawing, reference numeral 2 denotes a tubular shell formed by a synthetic resin such as acrylic resin etc. It is preferable to form the tubular shell with a transparent synthetic resin, however, it is not limited thereto. The tubular shell may be made of a metal or glass etc.

Within the tubular shell 2, there are mounted in parallel a great number of elongated tubes 4 through which the blood is allowed to flow. The bundle, consisting of the elongated tubes 4 arranged in a parallel relationship with the tubular shell, is fixedly secured by a pair of fixing plates at both ends thereof. The elongated tubes 4 are preferably made of, for example, a metal such as stainless steel etc., however, they are now always limited thereto. A synthetic resin having a good workability and which does not react with the blood can also be used for the material to form the tubes 4.

Reference numeral 8 represents an inlet port for a heating medium, which flows inside the tubular shell 2 to heat the blood flowing within the elongated tubes 4 and then flows out through an outlet port 10. The pair of fixing plates 6 may be formed as integral parts of the tubular shell 2, or alternatively the two may be separately manufactured and then permitted to adhere as integral parts thereof to each other by means of an adhesive. In the embodiment shown in the drawing, the fixing plates 6 have screw threads on the upper peripheral surface thereof which are engageable with the screw threads on the inner surfaces of caps 12 and 14 located at both ends thereof. It is essential to ensure liquid-tightness between the fixing plates 6 and the caps 12 and 14 to prevent leakage of the blood therethrough. In order to maintain liquid-tightness, seal members such as "O" rings etc., may be interposed between the fixing plates and the caps though not shown in the drawing.

The cap 12 on the inlet side has an inlet port 16 for blood, and the cap 14 on the outlet side has an outlet port 18 and an air bubble remover 20. The cap 14 on the outlet side has an interior space which is divided by an annular baffle plate 22 into an inner chamber 24 and an outer chamber 26. A proper clearance 28 is provided between the annular baffle plate 22 and the fixing plate 6 so that the blood can flow from the inner chamber 24 into the outer chamber 26. Though not shown in the drawing, one end of a rubber tube is inserted in the air bubble remover 20, and the other end of which is closed.

Thus, the blood flows through the inlet port 16 into the elongated tubes 4. A heating medium is allowed to flow through the inlet port 8 into the tubular shell 2 so as to exchange the heat with blood within the elongated tubes 4, and then flows out through the outlet port 10. In a practical application, this heat exchanger is used with the air bubble remover 20 disposed in upright position. The blood flowing inside the elongated tubes 4 effects heat exchange with the heating medium flowing in the tubular shell, and then flows into the inner chamber 24 defined inside the cap 14 on the outlet side. The oversaturated oxygen in the blood forms air bubbles and passes through the air bubble remover 20 into a rubber tube not shown in the drawing, because the air bubble remover is located in the upright position. The oversaturated oxygen can thus be changed into air bubbles and removed from the blood flowing through the heat exchanger. Because of the other end of the rubber tube being closed as mentioned above, air bubbles will accumulate inside the rubber tube. As a result the blood is pushed downwards by the action of the accumulated air bubbles and is allowed to pass through the space 28 defined between the annular baffle plate 22 and the fixing plate 6 so that the blood free of air bubbles can flow from the inner chamber 24 into the outer chamber 26. The blood which flowed into the outer chamber 26 will flow out through the outlet port 18.

It is to be understood that the above description is by way of example only, and that the details for carrying the invention into effect may be varied without departing from the scope of the invention claimed.