Measuring and testing – Fluid pressure gauge – Mounting and connection
Reexamination Certificate
1999-03-30
2001-10-02
Oen, William (Department: 2855)
Measuring and testing
Fluid pressure gauge
Mounting and connection
Reexamination Certificate
active
06295877
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to cannulas used in surgical applications, and more particularly, to a cannula equipped with a pressure/flow rate transducer.
2. Description of Related Art
In medical applications and specifically in surgery, the list of uses for cannulas is exhaustive. One application involves the augmenting or supplementing of pulmonary blood flow through the beating heart during cardiosurgery by use of one or more cannulas involved in the intake and return of blood into the circulatory system. The cannulas interface between the patient's circulatory system and the mechanical pumps that power the augmentation procedure. Such an application is described in co-pending PCT Application no. PCT/US97/18674 entitled “Single Port Cardiac Support Apparatus”, filed Oct. 14, 1997 and incorporated herein by reference in its entirety.
When performing cardiac surgery cannulas are placed within the patient's blood stream and used for inflow and outflow of blood or other fluids. If the operator wishes to determine the rate of fluid flow, either a catheter with appropriate sensors must also be placed in the patient's blood stream, or other sensors such as an external ultrasonic sensor as disclosed in U.S. Pat. No. 5,179,862 are used. A shortcoming of ultrasonic systems such as that described in U.S. Pat. No. 5,179,862 is that they require significant monitoring. Ultrasonic sensors also require that tubing of a specific diameter be used, thereby adding to the cost and complexity of the surgical procedure. Additionally, ultrasonic sensors are expensive and non-disposable, thereby adding to the cost of the surgical procedure.
Another method to measure flow rate is through the use of a thermodilution catheter. Thermodilution catheters require the infusion of a solution, typically saline, of a known temperature, with a distally disposed thermistor measuring the temperature change to determine the flow rate. This method is also expensive, increasing the cost of the surgical procedure. A second problem with using flow-sensing catheters, such as thermodilution catheters, is that they require the operator to place more incisions within the patient. The catheters must be placed so that they do not interfere with the inflow or out flow of the cannula. Visual markers along the length of the cannula may also be used to determine location, the greater the number of markers the more accurate the placement at the expense of quick readings due to the greater number of markings.
SUMMARY OF THE INVENTION
The present invention overcomes the deficiencies of the prior art by providing a cannula assembly having one or more pressure transducers coupled to a main lumen thereof. In accordance with a first embodiment, the pressure transducers are attached to the substantially tubular wall defining the main lumen.
In accordance with a second embodiment, a partial occlusion is provided in the cannula to increase the pressure drop across the main lumen. In this manner transducer signal is increased, and an improved differential pressure measurement signal achieved.
In accordance with a third embodiment of the invention, one or more pressure transducers are used in conjunction with a pair of coaxial cannulas for measuring pressure.
In accordance with at fourth embodiment of the invention, a differential pressure transducer is used, the differential pressure transducer being mounted in a dedicated secondary lumen in communication with the first lumen.
In accordance with a fifth embodiment of the invention, the secondary lumen housing the differential pressure transducer is disposed across a knee formed in the cannula to augment pressure measurement. Partial occlusions may also be provided for this purpose.
In accordance with a sixth embodiment of the invention, the secondary lumen housing the differential pressure transducer is formed integrally with the tubular wall defining the main lumen.
In accordance with a seventh embodiment of the invention, a soft, flexible tapered tip is provided at the distal end of the cannula. Such a configuration allows for easier negotiation through the patient's body during surgical procedure.
In accordance with an eighth embodiment of the invention, an inflatable balloon is provided at the distal end of the cannula. The inflatable balloon aids in transporting the cannula to the desired destination.
In accordance with a ninth embodiment of the invention, a guide wire lumen is provided for supporting a guide wire in the cannula. The guide wire is used as a predecessor step in the insertion of the cannula.
In accordance with a tenth embodiment of the invention, a light guide is supported in the cannula. The light guide conveys light to a predetermined portion of the cannula to thereby aid in the visualization and location of the cannula during the surgical procedure.
The invention realizes various advantages over the prior art, including a reduction in the number of incisions that a surgeon must make in performing surgical procedures, along with a reduction in the amount of foreign material introduced into the patient's body, while providing safe, rapid, accurate and cost-effective fluid flow rate measurements.
REFERENCES:
patent: 4508535 (1985-04-01), Joh et al.
patent: 5435308 (1995-07-01), Gallup et al.
patent: 5755687 (1998-05-01), Donlon
patent: 5797948 (1998-08-01), Dunham
patent: 5814004 (1998-09-01), Tamari
patent: 0 280 225 (1998-08-01), None
Aboul-Hosn Walid N.
Kanz William R.
McCrystle Kelly J.
O'Connell Desmond P.
A-Med Systems, Inc.
Oen William
Stangler Jonathan
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