Surgery – Diagnostic testing – Measuring or detecting nonradioactive constituent of body...
Reexamination Certificate
1999-04-09
2002-12-24
Winakur, Eric F. (Department: 3736)
Surgery
Diagnostic testing
Measuring or detecting nonradioactive constituent of body...
C600S323000, C600S322000
Reexamination Certificate
active
06497659
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to medical instruments, and more particularly, to a system for identifying a cable transmitting a signal from a sensor to an electronic instrument.
BACKGROUND OF THE INVENTION
Modem medical practice employs a wide variety of sensors for monitoring the condition of a patient during treatment, especially when the patient is undergoing a complex procedure such as surgery. For example, the patient's pulse rate, blood pressure, or the level of oxygen or carbon dioxide in the patient's blood may be monitored continuously by a sensor during a medical procedure.
A typical sensor is connected to an electronic instrument by a cable which transmits a signal from the sensor to the instrument to be processed and displayed on a continuous basis. For example, a conventional system for retrieving, processing, and displaying a signal from a sensor is shown in
FIG. 1. A
sensor
10
is connected to a cable
12
at a sensor terminal, and a connector
14
is attached adjacent to a signal terminal of the cable
12
. The signal terminal may extend through the connector
14
or it may rest in a junction in the connector
14
which itself may transfer the signal. The cable
12
includes a signal conduit between the sensor terminal and the signal terminal which may be an electrically conductive material or an arrangement of optical fibers. The connector
14
is received by a receptacle
16
in an electronic instrument
18
such that the signal terminal and auxiliary terminals in the connector
14
are placed in electrical contact with circuitry inside the instrument
18
. The connector
14
and the receptacle
16
may be joined by any suitable mechanical connection. The instrument
18
includes a display
19
for displaying a processed representation of the signal. The display
19
may be a tape display or a cathode ray tube or some other means of providing information. The system shown in
FIG. 1
operates in the following manner. The sensor
10
generates a signal in response to a stimulus from a patient which is applied to the sensor terminal of the cable
12
. The signal may be electrical or optical in nature. The signal is transferred by the signal conduit to the signal terminal of the cable
12
, and then to the circuitry in the instrument
18
through the connector
14
and the receptacle
16
. The signal is processed in the instrument
18
and presented in the display
19
according to methods appropriate for the particular signal.
As medical technology has improved, the number of sensors used to monitor a patient undergoing a procedure has increased substantially. Modem operating rooms are crisscrossed by cables, each cable transmitting a signal from an individual sensor which is monitoring a parameter of the patient. Each cable is attached to its own instrument which is adapted to process and display the signal provided by the cable and its sensor. It is of critical importance that the cables and sensors be matched correctly with their corresponding instruments. If two cables were to be accidentally switched to the wrong instruments then the information displayed by those instruments would be meaningless and potentially misleading. The chances for an incorrect connection increase in an emergency when there is little time to carefully consider each connection.
Another problem with medical monitors connect to a sensor is that various operating features or modes may be operational with some sensors but not operational with other sensors. In the past, these operating features or modes were often manually selected to correspond to the particular sensor connected to the monitor. However, manual selection of operating features or modes can be time-consuming, which is particularly disadvantageous in a medical emergency where time may be critical. Furthermore, manual selection of operating features or modes to correspond to a particular sensor is prone to errors because the wrong operating feature or mode may be selected for a particular sensor. For example, unique noise and artifact rejecting algorithms for use in a pulse oximetry monitor are disclosed in U.S. Pat. No. 5,687,722, 5,662,105, and 5,588,427 to Tien et al., all of which are incorporated herein by reference. In may not be necessary to use these noise and artifact rejecting features with some sensors, but it may be necessary to use these features with other sensors that are more sensitive to noise and artifact. If a noise and artifact sensitive sensor is connected to the monitor, but the operator mistakenly believes a less sensitive sensor is connected to the monitor, the operator may not enable the noise and artifact rejection features. Under these circumstances, the pulse oximetry monitor may fail to provide accurate indications of the oxygen saturation of a patient's blood.
The standardized production of cables increases the potential for an improper cable connection. Standardized cable designs lower manufacturing costs, but have the disadvantage that each cable has the same appearance, the same tactile characteristics, and the same terminal arrangements. When standardized cables are used for each sensor in an operating room, the absence of distinguishing features increases the likelihood that two or more cables will be connected to the wrong instruments.
A need exists for a system for distinguishing cables from each other in a medical environment such that the cables may be quickly and accurately connected to the proper instruments. Furthermore, it is desirable to prevent an instrument from processing and displaying a signal from the wrong sensor.
SUMMARY OF THE INVENTION
In accordance with the present invention, a system for identifying a cable transmitting a signal from a sensor to an electronic instrument is provided which permits a rapid identification of the cable. The cable includes an elongated signal conduit extending between a sensor terminal adapted to be connected to the sensor and a signal terminal. A connector is attached to the signal conduit adjacent to the signal terminal, and is attachable to the instrument to permit signal communication between the instrument and the sensor. A reactance element such as a capacitor or an inductor is coupled between two or more terminals of the connector which are coupled to the instrument. The reactance element as well as other cable identification components, may be packaged in the sensor, the sensor cable, and/or an adapter cable coupling the sensor to the instrument, as well as in connectors for those components. In one embodiment, the instrument includes a measurement circuit adapted to measure characteristics of the reactance element. In another embodiment, the instrument includes a microprocessor coupled to exchange signals with the measurement circuit. The microprocessor may also be coupled to the signal terminal to receive the signal from the sensor, and to generate information as a function of the signal. Various operating features or modes may be selected in the electronic instrument depending upon the nature of the cable and/or sensor connected to the cable, as determined by the characteristics of the reactance element.
In another embodiment, a method is provided for identifying a cable having a reactance element such as a capacitor or an inductor. A first voltage is provided to the reactance element, and a second voltage in the reactance element is monitored to detect a rate of change of the second voltage. The rate of change of the second voltage is compared to a predetermined rate and the cable is identified based on the comparison. In another embodiment, the reactance element is coupled to a bridge circuit and an alternating current signal is applied to the bridge circuit. An identification signal is generated when characteristics of the reactance element match predetermined characteristics.
REFERENCES:
patent: 4059797 (1977-11-01), Gay
patent: 4856530 (1989-08-01), Vandervelden
patent: 5184059 (1993-02-01), Patino et al.
patent: 5654712 (1997-08-01), Cheng
patent: 5660567 (1997-08-01), Nierlich
Dorsey & Whitney LLP
Kremer Matthew
Spacelabs Medical, Inc.
Winakur Eric F.
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