Surgery – Diagnostic testing – Measuring or detecting nonradioactive constituent of body...
Reexamination Certificate
2002-03-18
2004-08-03
Jones, Mary Beth (Department: 3736)
Surgery
Diagnostic testing
Measuring or detecting nonradioactive constituent of body...
C600S365000, C600S373000
Reexamination Certificate
active
06770030
ABSTRACT:
The invention relates to a device for carrying out in-vivo measurements of quantities in living organisms, comprising a catheter-like tube that accommodates, in a removable manner, a needle that is provided for inserting the tube in the organism; at least one opening in the wall of the tube; and a sensor for detecting the quantity to be measured in the interior of the tube.
It is frequently necessary in many areas in the field of medicine and in comparable fields to measure in a repeated or continuous manner concentrations or compositions of body fluids primarily for the purpose of being able to detect disorders of the homeostasis and to be able to treat such disorders, if necessary. For example, diabetes mellitus is a disorder of the metabolism that is reflected by various symptoms, whereby it is possible to control the concentration of the blood glucose by a therapy with insulin. Although this therapy with insulin substantially promotes the well-being of the patient, it is not possible to prevent late complications such as, for example premature blindness, heart and kidney failure, or neuropathies in most cases, but only to delay such complications. One of the most important causes for the late consequences of this disease is the not optimal coordination of the insulin injections with the blood glucose. Therefore, so as to be able to adapt the insulin injections to the needs of the body as required, the glucose concentration has to be measured repeatedly (or continuously) in a precise manner.
All kinds of different methods have been proposed for measuring the glucose in the organism, including blood sugar-measuring devices; non-invasive measuring methods; indirect determination of the glucose via other body parameters; or measurement of the glucose in body fluids other than the blood, for example in the sputum, in the perspiration, or in the urine. Because of the problems encountered when measurements are taken in such fluids, quantification of the glucose in the fluid of the tissue, which is closely connected with the plasma glucose, has been increasingly given more attention in the last few years. Problems arising in the blood such as, for example coagulation, the risk of infection, or protein loading, are highly reduced in this connection if they cannot be avoided, to begin with.
Various possibilities for measuring the glucose in the fluid of the tissue in a continuously manner have been proposed as well:
(1) Minimally invasive sampling methods such as the open micro-perfusion technique, the micro-dialysis, or the ultra-filtration technique.
(2) Sensors that are directly inserted in the tissue; or
(3) Techniques by which the tissue fluid is collected through the skin (the so-called suction technique, inverse iontophoresis).
In addition to the open micro-perfusion method and micro-dialysis, sensors that are directly inserted in the tissue have been found to be particularly well-suited for a continuous measuring system.
In connection with the open micro-perfusion technique and micro-dialysis, perfusion of a catheter inserted in the tissue is carried out with a rinsing liquid that, in connection with the open micro-perfusion method, mixes with the fluid of the tissue, whereas in connection with micro-dialysis, an exchange takes place via a membrane. This membrane, on the one hand, permits that the exchange of molecules between the tissue fluid and the rinsing liquid can be controlled in a selective manner; on the other hand, this property is altered by the deposits of endogenous substances (predominantly of proteins, but also of cells). Such deposits go hand in hand with a change in the transport properties of the molecules via the membrane, which is reflected by a diminished concentration of the molecules in the rinsing liquid. This drawback can be circumvented by macroscopic perforations in connection with the open micro-perfusion technique.
The equilibration between the fluid of the tissue and the rinsing liquid is a function of the exchange area and the flow rate of the rinsing liquid. If the flow rate is infinite, complete equilibration between the two liquids takes place. Because of the low flow rate, two decisive drawbacks ensue for the measurement of the substances in the rinsing liquid: firstly, the amount of fluid collected per unit of time is very small, and secondly, the delay caused by the length of the hose (system delay) will increase accordingly.
A higher flow rate is frequently selected for that reason in order to make more liquid available more rapidly. The drawback of this mode of operation consists in the not-complete mixing of the two liquids, which, if possible, has to be compensated by measuring other parameters. This causes additional requirements that the measuring technique needs to satisfy, which is found to be difficult particularly in connection with on-line measurements.
In addition to the sampling methods, which permit an ex-vivo measurement (sensor is located outside of the body), proposals already exist for in-vivo measurements, whereby the sensor is directly inserted in the tissue. In addition to the higher requirements the sensor needs to meet with respect to bio-compatibility, mechanical stability and size, it is necessary to pay attention to the problem posed by the calibration of the sensor. Although the sensors exhibit very good in-vivo characteristics, characteristics are observed that are changed in vivo. In order to take such changes into account, different starting points exist: a frequently employed starting point is the calibration of the sensor value against one or more blood values, whereby it is implicated that, in the case of a glucose measurement, the concentration of the glucose in the fluid of the tissue is equal to the concentration in the blood. So as to be able to render this a correct statement, the concentration of the glucose has to be in a state of equilibrium between the blood and the fluid of the tissue because a shift in terms of time exists between these two compartments. In addition to the painful stress affecting the person involved, calibrating changes “away” (for example infections in the tissue, encapsulation of the sensor) constitutes a substantial shortcoming of this measurement.
So as to avoid the drawbacks of the sampling methods (time delay), incomplete equilibration, a membrane disposed in between) and the implanted sensor (no calibration possibility, mechanical stability), a sensor (e.g. a glucose, lactate or glutamate sensor) can be inserted in a specially shaped catheter or general a tube or hose, and inserted in the tissue with the help of such a catheter or tube or hose); compare, for example U.S. Pat. No. 5,299,571 A, or U.S. Pat. No. 5,568,806 A. The catheter has a macroscopic opening, so that an exchange can take place between the fluid of the tissue and the sensor. After the sensor has been inserted in the respective tissue with the help of a setting needle present in a lumen, said setting needle is removed from the catheter. The setting needle or the associated lumen take up a mayor portion of the cross section of the catheter, and the sensor is arranged in a fixed manner in the lumen located adjacent to the lumen receiving the setting needle. The aforementioned opening in the catheter tube is located adjacent to the sensor. Suitable conduits lead from said sensor to the outside in order to permit a connection to an electronic measuring system. The manufacture of the catheter tube requires relatively much expenditure because of the two special lumens, whereby, furthermore, a relatively large cross section, notably the one receiving the setting needle, cannot be used for carrying out the measurement and has to be viewed as a lost volume.
Other types of catheter systems have already been proposed—compare, for example U.S. Pat. No. 5,779,665 A; U.S. Pat. No. 5,586,553 A; or U.S. Pat. No. 5,390,671 A, whereby the setting needle is present there outside of the catheter tube, approximately parallel with said catheter tube (U.S. Pat. No. 5,779,665 A), or with inclusion of the catheter tube. This en
Pieber Thomas
Schaupp Lukas
Collard & Roe P.C.
Jones Mary Beth
Kremer Matthew
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