Optics: measuring and testing – Blood analysis
Reexamination Certificate
2001-07-05
2004-10-19
Hannaher, Constantine (Department: 2878)
Optics: measuring and testing
Blood analysis
C356S339000, C356S401000, C356S614000
Reexamination Certificate
active
06806947
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus for detecting the presence of a fluid conduit and at least one characteristic of the contents of the fluid conduit, the apparatus being disposed on a control device, for example, for the extracorporeal treatment of blood, with a light source, the radiation of which is directed towards the conduit and through the conduit, and with an optical sensor for the radiation emitted by the light source that detects the radiation directed through the fluid conduit.
The apparatus according to the present invention is intended for use with control devices for dialysis, which are also termed monitors. In this case, the fluid conduit may be filled with blood, a rinsing liquid or air.
BACKGROUND OF THE INVENTION
A number of apparatus are known for the purpose of monitoring a fluid conduit or tube that is connected to a dialysis monitor. For example, air detectors are known which check the blood in the fluid conduit that is passed back to the patient for the presence of air or air bubbles. Furthermore, blood detectors are known that check the dialysate liquid passed back by the dialyzer for the presence of blood, and thus are able to determine the presence of a leak in the dialyzer membrane. As soon as these detectors determine air or blood in the fluid passed through the conduit, a control unit of the monitor connected with the detectors sets off an alarm to prevent endangering the patient. Moreover, an alarm is set off when a fluid conduit is absent, provided that these detectors are also designed to monitor the fluid conduit.
Normally, these known devices include a photoelectric section that is arranged such that it passes through the essentially transparent fluid conduit. For example, apparatus is known from German Patent No. 37 68 033 in which the infrared light from a source is transmitted using a waveguide to a tube or to a recess in a tube support that is intended to hold the tube. The light is transmitted through a second light section from the recess to a receiver. Depending on whether a tube is mounted or not, and whether it contains essentially transparent rinsing liquid or blood, a varying amount of light reaches the receiver. This sends a signal to an evaluating device or control unit, the signal that is dependent on the amount of received light thereby providing information about the condition of the tube or the contents of the tube. When no tube is present, the light reaches the receiver unfiltered or unattenuated, and the receiver then sends a high signal to the control unit. If a tube is mounted and filled with air or colorless fluid, for example rinsing fluid, the light reaches the receiver slightly filtered or attenuated, and the receiver then delivers a medium signal to the control unit. If the tube is filled with blood the light will be essentially completely attenuated, and at most a small amount of light will reach the receiver, which then supplies the control unit with a low level signal.
A disadvantage of this type of apparatus is that with certain tubes, as a result of their shape and composition, a lens effect can arise that distorts the results. In the worst case, this can lead to the same amount of light being transmitted to the receiver when a mounted tube is filled with colorless fluid as when a tube is not mounted. In both cases the receiver generates an identical signal, so that no differentiation is possible between the two states.
An apparatus is known from European Patent No. 0 467 805 in which the light source and receiver are each arranged to protrude such that they deform the tube. In this manner, the astigmatic focusing, the so-called lens effect, which otherwise results from the cylindrical geometry and focuses the light beam onto the receiver, is obviated. However, with this apparatus only the nature of the fluid present in the tube is determined with the photoelectric section, while the presence of the tube is determined using an electromechanical sensor. As a result of this supplementary electromechanical sensor, the apparatus is complicated and therefore costly, and at the same time it is unreliable due to the additional possibility of error.
Another apparatus is known from U.S. Pat. No. 5,644,402 which detects both the presence of a tube and also the characteristics of the fluid transported in the tube, with a photoelectric section. To this end, the light source, the receiver and a number of deflectors are disposed in a complicated geometric arrangement such that, depending on whether the tube is present, and on its content and the resulting differing refraction, the light beam either does not reach the receiver at all, or is once or twice diffracted. It is indeed possible to determine with a photoelectric section whether a tube is present and what characteristics the content has, and it is also possible to achieve greater sensitivity as a result of the partially longer light path. However, on the whole, this apparatus is very complex and therefore expensive. In addition, it is highly subject to failure and must be precisely adjusted to the tube in question in order to be able to provide accurate information.
In view of this background it is therefore an object of the present invention to provide an apparatus of the type described in the introduction with which a reliable investigation of the presence of a fluid conduit and also at least one characteristic of the content of the fluid conduit is possible with little expense, to improve the safety of the patient.
SUMMARY OF THE INVENTION
In accordance with the present invention, this and other objects have now been realized by the invention of apparatus for determining the presence of a fluid conduit at a predetermined location and at least one characteristic of the contents of the fluid conduit, the apparatus comprising a light source for generating radiated light in a direction towards the predetermined location, whereby when the fluid conduit is present at the predetermined location the radiated light passes in a direction through the fluid conduit, a first optical sensor for detecting the radiated light passing through the fluid conduit, and a second optical sensor for detecting the radiated light which is reflected by the fluid conduit. In a preferred embodiment, the apparatus is in combination with a control device. Preferably, the control device comprises a device for the extracorporeal treatment of blood.
In accordance with one embodiment of the apparatus of the present invention, the second optical sensor is integrally formed with the light source.
In accordance with another embodiment of the apparatus of the present invention, the apparatus includes a housing, and the light source, the first optical sensor and the second optical sensor are disposed in the housing. Preferably, the apparatus is in combination with a control device. In a preferred embodiment, the housing constitutes a portion of the control device.
In accordance with another embodiment of the apparatus of the present invention, the apparatus includes a first waveguide for transmitting the radiated light from the light source to the predetermined location and for transmitting the radiated light reflected by the conduit to the second optical sensor, and a second waveguide for transmitting the radiated light which passes through the fluid conduit to the first optical sensor. In a preferred embodiment, the apparatus is in combination with a control device. Preferably, the apparatus includes a housing, and the light source, the first optical sensor, and the second optical sensor are disposed in the housing, and the apparatus includes a fluid conduit holder for holding the fluid conduit at the predetermined location, the fluid conduit holder disposed on the housing, the first and second waveguides being integrated with the fluid conduit holder.
In accordance with another embodiment of the apparatus of the present invention, the first waveguide is disposed at a location adjacent to the fluid conduit whereby an air gap is created therebetween. In a preferred embodi
Ekdahl Olof
Wictor Per-Ola
Gambro AB
Hannaher Constantine
Lee Shun
Lerner David Littenberg Krumholz & Mentlik LLP
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