Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-01-24
2001-11-27
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S469000
Reexamination Certificate
active
06322513
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a catheter to be introduced into blood vessels and consisting of a substantially tubular instrument with at least one infusion or suction channel having at least one opening in the end area.
BACKGROUND OF THE INVENTION
By means of such catheters liquids can be injected into body cavities, e.g. blood vessels or samples can be taken from body cavities. Such catheters are also used during operations, particularly in operations where the patient is in a semi-sitting position, for the prevention and treatment of air embolisms. Air embolisms can occur when venous vessels are opened and a negative venous pressure prevails as a result of heavy blood loss, e.g. during transplants. Thereby air can be sucked into the central venous system and an accumulation of larger air volumes can occur, blocking the blood flow to the heart.
For the aspiration of such air from the central venous system, the catheter which has at least one opening, is placed in the upper vena cava at the entrance to the right atrium. When a catheter with several lateral openings is used, the point of the catheter is placed rather in the upper half of the right atrium. Through the opening or openings of the catheter, the air which may have entered the central venous system during an operation is aspirated, thereby preventing an air embolism. The disadvantage is that in order to prevent air embolisms such catheters have to be precisely placed, but their placement is not simple because the position of the catheter cannot be exactly determined from the outside.
Besides in addition to the catheter a further instrument is required, in order to detect the air which may possibly have entered the central venous system and to aspirate it by means of the catheter.
Provided that transesophagial echocardiography is used, a flexible tube with an ultrasound device at its end can be introduced into the patient's esophagus. The disadvantage of this method is that the required equipment is very expensive and that the patient has to be monitored by an additional physician not only during the operation, but also for several hours afterwards. So far this method has proven to be very costly.
In another procedure for detecting air embolisms a Doppler probe is affixed from the outside on the body of the patient in the cardiac area. The measuring results obtained this way are partially quite inaccurate since the distance between the Doppler probe affixed to the skin and the heart is large, and the resulting measuring results can be influenced by the hemostatic devices used in the operative tract, such as electrocautery. Furthermore the Doppler probe has to be very precisely placed. With patients with lung enlargement, for instance as the result of bronchitis or asthma, this procedure cannot be used at all.
OBJECT OF THE INVENTION
It is the object of the invention to indicate a catheter, particularly for the prevention and therapy of air embolisms, which avoids the aforementioned drawbacks.
SUMMARY OF THE INVENTION
This object is achieved by providing the catheter with at least one measuring device for the detection of gases in liquids. By integrating the measuring device into the catheter, the catheter can be used not only for the aspiration of air when the catheter is used for the prevention and treatment of air embolisms during operations, but also for the detection of air in liquids, such as blood. Besides the placement of the catheter is facilitated due to the integrated measuring device. Since the catheter with the measuring device is directly flushed by the liquid to be monitored, and thereby is in immediate contact with the liquid to be monitored, disturbances such as occur during conventional procedures are reduced to a minimum. Since only the measuring device or devices are integrated in the catheter, while the other components required for aspiration and injection, such as control or suction devices are arranged outside the catheter, such catheters have very small diameters.
Suitably the measuring device can be an ultrasound probe, consisting at least of one receiver and a transmitter arranged at an angle to one another. In another embodiment a measuring device radiating in several, particularly circular, directions can be provided. However it is also possible to have a combination of measuring devices offset from one another and one circularly radiating measuring device. Such probes make use of the so-called “Doppler effect”, wherein the frequency change between the waves radiated from the receiver and reflected by the liquid or air bubbles, and the waves received by the receiver is established. For instance if an air bubble existing in the blood vessel flows along the ultrasound probe, the frequency of the waves reflected by the air bubble changes. This frequency change is then signalled acoustically or optically, so that the air bubble can be aspirated through the catheter openings.
In order to insure that the measuring device is reusable and does not come into direct contact with the blood when the catheter is introduced in a blood vessel, at least one insertion channel closed at its end can be provided. For this purpose the measuring device is slipped into the closed-end insertion channel, so that a contact with the liquid to be monitored is avoided. The catheter equipped this way with the measuring device is then introduced into the blood vessel.
In another embodiment of the invention, on both sides of the infusion or suction channel, closed insertion channels can be provided. Several measuring devices can be offset with respect to one another. This insures that, due to the overlapping angles of radiation, the entire vessel volume is monitored, so that air bubbles in any area of the vessel volume can be detected.
It is possible to provide the catheter with end-side and/or lateral openings for the aspiration of the detected air bubbles.
In a particularly advantageous embodiment of the invention, the measuring device or devices are arranged at a distance from the catheter end, and the catheter has lateral openings at least between the measuring devices. The catheter can be placed in such a manner that the measuring devices are located in the area entering the right atrium, so that the part of the catheter with the openings is placed in the atrium. To the extent that air bubbles are detected by the measuring devices in the blood flowing from the blood vessel via the right atrium to the heart, these air bubbles can be directly aspirated via the catheter openings following in the flow direction.
REFERENCES:
patent: 4354502 (1982-10-01), Colley et al.
patent: 5025778 (1991-06-01), Silverstein et al.
patent: 5456251 (1995-10-01), Fiddian-Green
patent: 6001069 (1999-12-01), Tachibana et al.
patent: 6059731 (2000-05-01), Seward et al.
patent: 1 510 682 (1978-05-01), None
Dubno Herbert
Imam Ali M.
Lateef Marvin M.
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