When a connecting tube of a blood pump or a humor circulating circuit and a tube such as a cannula mounted on a circulatory system organ are connected in order to pour blood or humor substitution fluid in the circulatory system organ, it is necessary to carefully connect the tubes so as not to allow bubbles to remain within the tubes. If the bubbles are contained in blood, a blockade of blood capillaries or the like occurs, resulting in an extremely dangerous condition for a living body.
As one means for connecting two tubes filled with blood or the like to eliminate bubbles therein, there is a method for connecting the tubes while pouring the humor substitution fluid or physiological saline solution to connected ends of two tubes. In accordance with this method, a tube such as a cannula mounted on a blood vessel is supported with a connected end directed upwardly, blood is moved up to the interior of the tube by blood pressure, and thereafter, the tube is clamped below a liquid level of blood. Then, the humor substitution fluid is filled from the clamped portion to the upper connected end, and the tube is sufficiently commoved to completely discharge bubbles adhered to tube walls from the interior of the tube. Similarly, the connecting tube of the blood pump is also filled with the humor substituion fluid to completely discharge bubbles, two tubes are made to come closer to each other with connected ends thereof directed upwardly, and the connected end of one tube is inserted into the connected end of the other tube within the flowing-down humor substitution fluid while a large quantity of the humor substitution fluid to said portions which are formed to come closer to each other to connect two tubes.
In the above-described connecting method, even if bubbles are carefully discharged by commotion, air tends to be entrained into liquids since connecting of tubes is carried out within the flowing-down liquid and a part of the air is drawn into the tubes and formed into bubbles. Thus, there was a disadvantage in that the bubbles remain within the tubes despite the fact that connecting of tubes was carried out with effort.
In view of the foregoing, a connecting method has been used in which a connecting tube provided with branch tubes is used to connect two tubes, and bubbles within the tubes after connection are guided into the branch tubes for discharge. In this method, a cannula from which bubbles within the liquid have been discharged and a connecting tube are connected by insertion with the branch tubes directed upwardly, the connecting tube is curved in the form of a mountain to bring the branch tubes to the highest position, the two connected tubes are commoved to upwardly move the bubbles up to the branch tubes to completely remove the bubbles within the connected tubes, and thereafter, root portions of the branch tubes are clamped.
This method making use of the branch tubes carries out the discharge of bubbles after the tubes have been connected and therefore can positively prevent the bubbles from being retained as compared with the method of connecting tubes after removal of bubbles. However, vestiges remain on side walls of portions where the branch tubes were present and thrombus tends to occur on said vestiges. Therefore, there involves a disadvantage that in case of transfusion of blood, heparin has to be contained in blood.
As the result of a series of studies on means and apparatus for connecting two tubes which can positively remove bubbles within the tubes and which can prevent re-generation of bubbles when the tubes are connected and remain on vestiges on side walls of the tubes connected, the present inventors have found that a method can be used in which two tubes are connected within the liquid in order to facilitate connection of the tubes with bubbles being eliminated completely and positively.