Surgery – Diagnostic testing – Measuring or detecting nonradioactive constituent of body...
Reexamination Certificate
1990-09-21
2001-10-02
Winakur, Eric F. (Department: 3736)
Surgery
Diagnostic testing
Measuring or detecting nonradioactive constituent of body...
C600S339000, C600S310000, C600S322000, C600S342000
Reexamination Certificate
active
06298253
ABSTRACT:
This invention relates to a method and device for measuring the absorption of radiation in a portion of tissue) using in particular a sensor device which comprises two sensor areas for transilluminating a portion of tissue wherein said sensor areas are connected to a measuring instrument and with one of them being conceived as radiation emitter and the other being conceived as radiation sensor.
When monitoring physiological or biochemical data about biological tissue, the aim of a continuous registration of data is to determine such data directly and as precisely as possible.
When preparing and/or surveying childbirth it is desirable to survey the physical condition of the fetus continuously and to have data at hand which allow an assessment of the present state of the child and in particular of fetal oxygen supply.
Up to now a current method of surveying the fetus is to monitor its heart rate continuously, either by a fetal electrocardiogram or by registering movements which are synchronous with the heartbeat by means of ultrasound. However, changes of the fetal heart rate—even when judged in correlation with uterine contractions—are not very reliable indicators of fetal well-being.
The prior art also offers the possibility of continuously measuring fetal partial pressure of O
2
and CO
2
. Although these parameters are interesting from a clinical point of view, the employed measuring techniques involve considerable theoretical and practical disadvantages which do not allow their routine use:
Apart from the fact that such transcutaneous measurements often do not present the necessary precision and reproducibility, a further disadvantage is that the diameter of the probes is relatively large. This does not allow their introduction until the orifice of the uterus is already relatively wide open. A further disadvantage is the necessity of visual control when attaching the probes to the fetal skin and with it the fact that a “vaginal adjustment” is required for both their positioning and control. Another disadvantage with this measuring method is that the skin needs a rather considerable warming-up in order to obtain a hyperemia. During prolonged measuring periods this warming-up may involve skin damage.
A further possibility of the prior art is to measure oxygen saturation of the blood optically and transcutaneously by transilluminating a portion of tissue. With this method, appropriately chosen radiation wavelengths allow determination of the percentage of hemoglobin carrying O
2
. This kind of measurement requires a measuring device which can be placed around part of the body for transilluminating the same. The prior art applies such measuring devices on a finger or an ear-lobe.
Patent Application No. EP-A2-135 840 describes a measuring device which allows measurement of the oxygen level of fetal blood by introducing a sensor carrier into the vagina. The loose end of the sensor carrier is provided with a sensor device suitable for placement on the fetus. Measurement is made by reflection from the fetal tissue, with the sensor device being placed on the surface of the fetal body, e.g. somewhere on the head. A disadvantage of this measuring device is the fact that there is no true optical transillumination of the tissue. There is only a reflection which is effected by a light emitter which emits light onto the surface of the fetal tissue. As the light receiver is mainly placed beside the light emitter, i.e. also outside the tissue in question, essentially there is no real transillumination of or transmission through the tissue.
Patent Application No. GB-A-2 155 618 describes a measuring device which is also simply placed on the surface of the fetal body, just as the measuring device described in Patent Application No. EP-A1-247 777.
The objective of this invention is to provide a method and a device of the kind already described at the beginning of this document and to allow a precise monitoring of data with biological tissue. The method and device distinguish themselves at the same time by their simple construction and reliable practicability.
As described in this invention, the objective is met by means of at least one sensor area which is or can be introduced into the tissue for transilluminating the same.
The device and the method of this invention offer a number of considerable advantages. In accordance with this invention at least one sensor area is invasively stuck into the tissue. This guarantees that the tissue is adequately transilluminated and that the obtained absorption of radiation is such as to furnish the required parameters. The tissue is hardly impaired by the measurement, and blood-perfusion, for example, is not disturbed.
The disclosed invention thus offers a particularly precise way of determining or monitoring oxygen saturation or oxygen supply of the tissue. For example, the disclosed invention is suitable, as will be described hereinafter, for monitoring a child during birth. The disclosed invention can, however, also be applied for monitoring the oxygen supply of experimental tumors in the field of cancer research, the oxygen supply of the heart in the field of infarct research, or the oxygen supply of persons exposed to extraordinary ambient conditions, as is, e.g., the case with high-performance athletes or people working in rooms with a reduced oxygen level and an associated risk of suffocation. In the latter application, a signalling or warning device can be connected to the device of the disclosed invention.
Furthermore, the method and device of this invention make it possible to monitor the blood-perfusion of organs and skin lobes in a particularly simple way, for example intra- or post-operatively, for example after transplantations, plastic surgery, vessel- and bypass operations. As already mentioned, another possibility is the application for perinatal monitoring.
With this invention, at least one sensor area is stuck invasively. Possible embodiments of this invention allow an invasive sticking of either the radiation-emitting or the radiation-receiving sensor area alone or of both sensor areas.
The disclosed invention preferably uses the pulsatile share of absorption as a parameter since with this pulsatile share a particularly simple determination of influences originating from blood-perfusion is possible.
In a particularly advantageous embodiment of this invention the radiation for transilluminating the tissue is selected within a wavelength range between 0.1 and 20 &mgr;m.
This advantageous embodiment of this invention provides that radiation wavelengths (at least 2) for determination of hemoglobin fractions are selected so as to allow, for example, deducting values for sHb, sHbO
2
, sHbCO), sHbCO
2
, sHbS, sMet-Hb, sHbF, etc.
For attaching the sensor device on the tissue, it may be convenient to mount the same on an oblong sensor carrier which can, for example, be introduced into the vagina.
In order to guarantee the safe emission and sensing of the radiation and to avoid any electrical interference, the use of an optical fiber may be particularly suitable for emitting and/or sensing radiation. In such a case, the radiation source can either be placed on the sensor device or in a remote pertinent measuring instrument.
This invention also includes the possibility of placing the radiation source(s) directly on the surface of the tissue so that no optical fiber is required for at least one sensor area. The transmitted radiation can be registered by means of an electro-optical converter directly on the surface of the tissue or in the measuring device if an optical fiber is used.
Another possibility is to stick electro-optical converters into the tissue invasively. In a particularly advantageous configuration of this invention both the radiation emitter and the radiation sensor can be arranged on a single-piece sensor carrier, for example on a needle. It is, however, also possible to place the radiation emitter or the radiation sensor on a separate puncture-element carrier. The type and choice of the respective light sources or light sensors ca
Pendorf & Cutliff
Winakur Eric F.
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