Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
1998-03-25
2002-05-28
Kennedy, Sharon (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S100010
Reexamination Certificate
active
06394977
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates to a pressure monitoring device for measuring the pressure that is generated during inflation of a balloon-tipped catheter and the duration of such inflation. More particularly, the present invention relates to a pressure monitoring device having a pressure transducer, a signal converter, and a display device that are substantially encased in a sterilizable housing for repeated use.
2. Relevant Technology
In recent years, balloon-tipped catheters have become increasingly useful in various medical procedures. For example, balloon-tipped catheters have been used to reduce the intrusiveness of medical procedures in various fields of medicine, such as urology, gynecology, cardiology, and the like. Particularly in the treatment of coronary artery disease, the use of balloon-tipped catheters and their associated fluid pressurization systems has become widespread.
Coronary artery disease is the narrowing of the arteries that feed oxygen-rich blood to the heart. The heart needs adequate amounts of oxygen to continually and efficiently pump blood throughout the body. When arteries leading to the heart become narrowed and constricted due to coronary artery disease, several problems can develop. A person with coronary artery disease can experience angina, which is characterized by chest pain or pressure that radiates to the arm or jaw and is caused by a lack of oxygen-rich blood to the heart muscle. If untreated, coronary artery disease can lead to or contribute to heart failure and death.
In recent years, coronary angioplasty has become a common and accepted alternative to the vastly more intrusive coronary bypass surgery. Coronary bypass surgery involves surgical access to the heart, placing the patient on an extracorporeal blood oxygenation system so that the heart can be stopped for surgery, and then surgically attaching one or more passageways by which blood can bypass a clogged coronary artery, all under general anesthesia. Coronary angioplasty, which can be performed using a local anesthetic, involves running a dilation catheter (a catheter having an inflatable balloon near the end) to the diseased artery and then inflating the balloon in order to compress plaque within the artery, thereby obtaining increased blood flow to the heart. Compared to coronary bypass surgery, coronary angioplasty is less intrusive and traumatic, typically involves less risk to the patient, and significantly reduces the patient's discomfort and recovery time.
During inflation of the balloon during angioplasty, no blood can flow through the artery that is being mechanically dilated. The disruption of blood flow must be limited in duration to about 20 to 60 seconds, so as to avoid tissue damage due to oxygen deprivation. Hence, it is important to carefully monitor the inflation pressure and duration to ensure that blood flow is restored before tissue damage can occur. In most cases, it is not possible to adequately dilate a diseased artery in a single inflation. In cases where it is necessary to undertake multiple inflations in the same artery, it is important to allow sufficient time between successive inflations so that the tissues fed by the diseased artery can become fully oxygenated before blood flow is disrupted again. At the same time, a successful angioplasty procedure requires that the dilation of the artery be conducted for a significant period of time.
In addition to monitoring in real time the inflation pressure and duration, it is also important for the physician performing the angioplasty to have access to historical information regarding the duration and intensity of past inflations and deflations. Accordingly, various devices and gauges have been developed for monitoring inflation and deflation of balloon tipped catheters during angioplasty. All pressure gauges for measuring pressure within a syringe generally have at least two primary components: a pressure sensing unit and a display unit. The pressure sensing unit is positioned to be in fluid communication with the syringe often by being mounted directly thereon. The display unit typically comprises a dial, a liquid crystal display, a graphical device, or another visible system that displays the magnitude of the fluid pressure that is detected by the pressure sensing unit. The pressure sensing unit is connected with the display unit electrically, mechanically, or by other means by which information may be transmitted.
One common pressure gauge is configured with the pressure sensing unit positioned on the syringe, while the display unit is located perhaps several feet away from the syringe. Typically, electrical cables connect the pressure sensing unit with the display unit. It has been found that use of such pressure gauges can be somewhat awkward, since the physician who operates the syringe must repeatedly alternate his or her attention from the syringe to a the display unit or must receive inflation information second-hand from an assistant who monitors the display unit. In addition, the cables and relatively bulky display unit may cause the operating area to become cluttered.
The problems associated with physical separation of the display unit and the pressure sensing unit have been addressed by using integrated pressure gauges in which the pressure sensing unit and the display unit are combined in a self-contained device. Such integrated gauges are generally attached directly to the syringe. Accordingly, an integrated gauge may be more convenient to use, because the operating physician can more exclusively concentrate on the syringe area during the medical procedure. Because integrated gauges are positioned on the syringe in communication with the catheter fluid and relatively near the patient, such gauges must be sterilized for reuse or disposed after the medical procedure. In practice, disposable gauges are often prohibitively expensive, and sterilizable gauges are therefore generally preferred.
Liquid crystal displays (LCD's) and other mechanisms conventionally used for displaying information measured by digital systems cannot withstand the high temperatures used during sterilization procedures. In addition, a self-contained power supply has not been available in the past that can suitably be used in an integrated pressure gauge and that can withstand sterilization temperatures. While light-emitting diodes (LED's) would generally be able to withstand sterilization temperatures, their use in a self-contained pressure gauge would be undesirable due to their high energy requirements, which would quickly deplete self-contained energy supplies. Thus, due to the impracticability of using commercially available display devices that can be used with digital pressure gauges, conventional sterilizable integrated pressure gauges have been exclusively analog and mechanical since analog displays consume little or no energy and have no parts that are destroyed by heat sterilization processes.
Integrated mechanical pressure gauges have a sensor diaphragm that may be placed in fluid communication with the syringe, so as to be physically displaced in response to generated fluid pressure. The distance of displacement of the diaphragm is typically proportional to the magnitude of the fluid pressure. The diaphragm may be mechanically connected to a C-shaped flexible metal member, such as a brass or bourdon tube, that is used to mechanically convert the linear displacement of the diaphragm into rotational displacement of a spindle and a pointer across a graduated numerical dial. In this manner, the dial mechanically displays the magnitude of the fluid pressure within the syringe. The integrated pressure gauge is generally removably attached to the syringe such that the gauge may be placed in an autoclave or otherwise sterilized for reuse after each medical procedure.
Sterilizable integrated mechanical pressure gauges of the prior art have experienced a number of problems, however. For instance, the many moving parts within mechanical gauges are rel
Stout Thomas D.
Taylor Steven R.
Kennedy Sharon
Merit Medical Systems Inc.
Workman & Nydegger & Seeley
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