A major surgery commonly is carried out under general anesthesia. At this time, in order not to induce the respiratory arrest, maintenance of the airway is carried out by inserting a tracheal catheter into the oral cavity of a patient. In such a case, in order to suppress the production of saliva, a drug such as atropine sulfate generally is administered. In order to suck and remove the saliva or sputum that is nevertheless produced, a suction catheter often is used. Furthermore, in an open-heart surgery or an abdominal operation, the suction catheter is useful for sucking and draining (and in certain cases, reusing) a body fluid such as blood or effusion, etc. coming out from an affected site such as a wound site.
However, a conventional suction catheter had some disadvantages in use as follows.
First, when a body fluid is sucked and removed while bringing a suction catheter into contact with an affected site, the tip of the catheter sucks upon the living tissue due to a “sucking phenomenon” and cannot be detached therefrom frequently. In such a case, conventionally, by pinching the suction catheter by the finger to close it or by bending the suction catheter, the suction force is weakened to thus eliminate the sucking phenomenon. However, when the catheter has a small diameter or a large wall thickness, a bore thereof cannot be closed sufficiently by the finger, and so the suction phenomenon cannot be eliminated sufficiently in many cases. In such cases, by bending the catheter, the bore is closed. However, in this method, an operator has to use both hands, thus making the work inconvenient.
Therefore, a suction catheter provided with a side hole serving as a ventilating port at a base end of the catheter has been devised. In this suction catheter in use, during suction, an operator closes the side hole by the finger, and opens the side hole when the sucking phenomenon occurs. Thereby, the negative pressure is released, thus eliminating the sucking phenomenon. However, with this catheter, since sputum, blood, or the like, is attached to the finger used for closing the side hole during suction, it is not sanitary. Besides this, a suction catheter provided with connector having a complicated for weakening the suction force has been devised, but it is expensive and hard to be commercialized.
Furthermore, JP 5 (1993)-51351U discloses a suction connector in which a ventilation port is filled with a cylindrical filter made of a synthetic resin, which allows gases to pass through but does not allow liquid to pass through. This structure is intended to obtain a function of preventing liquid from scattering by the filter. However, with this suction connector, a sufficient amount of suction cannot be secured. Furthermore, in the case where the regulation of the suction speed and the suction amount is carried out frequently or over a long time, contaminant enters into the filter mesh along the longitudinal direction thereof, so as to prevent the ventilation of gas in the direction from the ventilating port to the fluid passage. Consequently, the reduction of the suction force by releasing a negative pressure may be insufficient.
As mentioned above, in the conventional configuration, it has not been possible to obtain a suction catheter having both functions of releasing a negative pressure and preventing liquid from scattering that are balanced to a practically sufficient extent; having a simple structure; and being cheap. Moreover, in order to obtain the sufficient function of releasing a negative pressure, it is necessary to broaden a cross-section of the ventilating passage and a suction regulating aperture, that is, an opening end of the ventilating passage. However, if the cross-section of the ventilating passage and a suction regulating aperture are broadened, the scattering amount is increased, thus making it difficult to provide a suction catheter with both functions.