The present invention relates generally to sensor and guide wire assemblies, in which a sensor element is mounted at the distal end of a guide wire for intravascular measurements of physiological variables in a living body, and particularly to the mounting arrangement of the sensor element, and more particularly to a jacket in which the sensor element is disposed, according to the preamble of the independent claim.
In many medical procedures, various physiological conditions present within a body cavity need to be monitored. These physiological conditions are typically physical in nature—such as pressure, temperature, rate-of-fluid flow, and provide the physician or medical technician with critical information as to the status of a patient's condition.
One device that is widely used to monitor conditions is the blood pressure sensor. A blood pressure sensor senses the magnitude of a patient's blood pressure, and converts it into a representative electrical signal that is transmitted to the exterior of the patient.
For most applications it is required that the sensor is electrically energized. Some means of signal and energy transmission is thus required, and most commonly extremely thin electrical cables, sometimes called microcables, are provided inside a guide wire, which itself is provided in the form of a tube, which often has an outer diameter in the order of 0.35 mm, and oftentimes is made of steel.
In order to increase the bending strength of the tubular guide wire, a core wire is positioned inside the tube. The core wire also helps to improve “pushability” and “torquability” of the guide wire. The mentioned electrical cables are e.g. positioned in the space between the inner lumen wall and the core wire.
Sensor and guide wire assemblies in which a sensor is mounted at the distal end of a guide wire are known. In U.S. Patent Re. 35,648, which is assigned to the present assignee, an example of such a sensor and guide wire assembly is disclosed, where a sensor guide comprises a sensor element, an electronic unit, a signal transmitting cable connecting the sensor element to the electronic unit, a flexible tube having the cable and the sensor element disposed therein, a solid metal wire, and a coil attached to the distal end of the solid wire. The sensor element comprises a pressure sensitive device, typically a membrane, with piezoresistive elements connected in a Wheatstone bridge-type of arrangement mounted thereon.
As is disclosed in, for example, U.S. Pat. No. 6,167,763, which also is assigned to the present assignee, the sensor element can be arranged inside a short tube (usually referred to as a sleeve or jacket), which protects the sensor element and comprises an aperture through which the pressure sensitive device is in contact with the ambient medium. The U.S. Pat. No. 6,167,763 further illustrates that a first coil may be attached to the distal end of the jacket and that a similar second coil may be attached to the proximal end of the jacket. The solid metal wire—which, as also mentioned above, in the art usually is referred to as the core wire—extends through the interior of the jacket and may be provided with an enlarged diameter portion adapted for mounting of the sensor element.
U.S. Pat. No. 7,222,539 discloses a jacket, wherein a sensor element and a core wire are provided in separate compartments. Another example of a sensor guide wire comprising a sensor enclosed by a sensor housing is disclosed in WO 2006/037082 A2.
In WO 03094693 A2, a pressure-measuring apparatus is disclosed, the pressure-measuring apparatus comprises a sensor transducer adapted to be incorporated in a catheter.
DE 2420610 A1, discloses a sensor for measuring pressure, the sensor is adapted to be incorporated in a catheter. The sensor is enclosed by a protecting tube.
U.S. Pat. No. 6,019,728 A1, discloses a catheter including a catheter tube to be inserted into a body. A plurality of sensing portions are arranged in the catheter tube. Two pressure communication holes are provided in the wall of the catheter tube to communicate the ambient pressure of the tube into the interior of the tube.
In US 2007088220 A1 an implantable medical device including a physiological sensor is disclosed. The sensor is embedded in a mesh structure of a stent-like structure.
In US 20050187487 A1 and US 20060211946 A1, further examples of catheters provided with sensors are disclosed.
U.S. Pat. No. 6,162,182 A, discloses a cannula usable to remove blood from a patient during surgery.
Generally, a sensor and guide wire assembly comprises a sensor element in the form of an elongated, essentially rectangular chip with a pressure sensitive member in the form of a membrane provided thereon. The sensor chip is arranged inside a jacket, which besides the sensor chip also accommodates a portion of a core wire and at least one electrical lead connected to the sensor element. A first coil may be attached to the distal end of the jacket, and optionally a second coil may be attached to the proximal end of the jacket. The first and second coils may be attached to the respective end of the jacket, e.g. by gluing, or alternatively soldering.
Although sensor and guide wire assemblies comprising a jacket designed according to the techniques presented by the present assignee in practise have proven to work very well, there are continuously ongoing efforts to improve the performance and functionality of the sensor and guide wire assemblies.
According to the prior art, the jacket is provided with an aperture or window, through which the pressure sensitive part (typically a membrane) of the sensor element is in communication with a surrounding medium, e.g. blood. Now, it has—for the first time—been recognized that the dimensions of the aperture, the sensor element and the interior of the jacket in combination with the particular mounting arrangement of the sensor element are such that air present within the jacket and/or adhering to the surface of the jacket or sensor element has a tendency to be entrapped within the jacket and/or forming an air bubble covering the aperture in the jacket. In other words, the ambient fluid (e.g. blood) does not wet the sensor element and the membrane completely, which affects the signal quality of the device.
An object of the present invention is therefore to provide a sensor and guide wire assembly comprising an improved jacket, with which the above-mentioned wetting problem is eliminated or at least minimized.
The above-mentioned object is achieved by the present invention according to the independent claim.
Preferred embodiments are set forth in the dependent claims.
Thus, by providing a jacket with multiple holes an improved wetting can be achieved, which ensures a more reliable and stable sensor output.
The sensor guide wire for intravascular measurements of at least one physiological, or other, variable in a living body, in accordance with the present invention, comprises a sensor element arranged in a jacket in a sensor region of said sensor guide wire, a core wire extending at least partly along the length of said sensor guide wire, at least one electrical lead connected to said sensor element, wherein said jacket is tubular and provided with a jacket wall, and further comprises a first opening arranged in said jacket wall, said jacket is further provided with proximal and distal end openings, and wherein a core wire is adapted to extend through said jacket via said proximal and distal end openings, and wherein the sensor guide wire has an outer diameter of approximately 0.35 mm, and wherein said jacket further comprises at least a second opening arranged in said jacket wall.
a illustrates a sensor guide wire and a jacket according to a second embodiment of the present invention.
b illustrates the jacket according to the second embodiment, also shown in
a shows a sensor guide wire and a jacket according to a fifth embodiment of the present invention.
b illustrates the jacket from above according to the fifth embodiment, also shown in
For better understanding of the context in which the present invention is going to be used, a sensor and guide wire assembly 1 of a conventional design is illustrated in
Although not shown in
To solve the problems outlined above, the present inventors suggest a sensor and guide wire comprising a jacket 20 with multiple openings, which allows for complete or at least improved wetting of the sensor element 18 and membrane. In contrast to the previously known jackets, which have only a first opening, through which first opening a membrane senses e.g. the surrounding pressure, and end openings, through which a core wire extends, the jacket 20 comprises further at least a second opening 23.
In
According to a preferred embodiment of the present invention, and as also shown in
In
b also illustrates the jacket 20 according to the second embodiment of the present invention. The jacket 20 has a first opening 22 and a second opening 23 arranged at the opposite side of the jacket 20 in relation to the first opening 22. In addition, the jacket 20 is provided with yet further five openings denoted 33, 34, 35, 36 and 37. Thus, according to the second embodiment of the present invention the jacket 20 is provided with seven openings 22, 23, 33, 34, 35, 36, 37 distributed at the jacket wall 21 all around the jacket 20.
In
a shows the sensor guide wire 24 and the jacket 20 according to a fifth preferred embodiment of the present invention. The jacket 20 is provided with proximal and distal end openings 29, 30 and a core wire 26 extends through said jacket 20 via the proximal and distal end openings 29, 30. Further, the jacket 20 is provided with a first 22, a second 23, a third 33, and a fourth opening 34, which openings are arranged in pairs on opposite sides of the jacket 20. According to this preferred embodiment, the openings 22, 23, 33, 34 are asymmetrical. The first and the fourth openings 22, 34 (not shown in
b illustrates the jacket 20 from above according to the fifth embodiment of the present invention.
According to another embodiment of the present invention , the openings 22, 23, 33, 34 arranged in pairs on opposite sides of the jacket 20 may be slightly displaced in relation to each other along the longitudinal axis 31.
In
It should be noted that previous embodiments are applicable, regarding the number of openings and how they are arranged, in a jacket provided with a mesh-like wall.
The present invention is not limited to the above-described preferred embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the invention, which is defined by the appending claims.
Number | Date | Country | Kind |
---|---|---|---|
1050717-6 | Jun 2010 | SE | national |
61359954 | Jun 2010 | US | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/EP2011/060008 | 6/16/2011 | WO | 00 | 12/21/2012 |