CABLE TERMINATION STATUS
BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to methods of and/or apparatus for detecting the status of a cable termination and has been devised particularly but not solely for use in detecting the status of the connection between a patient and one or more cables from a patient monitoring system such as those monitoring systems used in the healthcare industry.
In medical patient monitoring systems requiring attachment of electrical cables to the body of a patent, it can be of considerable advantage to know if such cables are correctly terminated. A detached cable may not be immediately obvious resulting in time wasting fault diagnosis or a possible life threatening situation. For example, careful control of a physical characteristic such as body temperature is often required for patients such as new-born babies (infants) in hospital environments. Once such way of controlling an infant's body temperature is to place the infant in a warmer. The warmer maintains the body temperature of an infant and radiates heat selectively when or as required to maintain the body temperature of the infant at a desired level. The infant's body temperature is measured by the warmer control circuitry using an electric cable having a temperature probe attached to an external surface of the infants body.
It is important that the cable is correctly terminated, that is, that the temperature probe is in secure contact with the infant's body in order that an accurate measurement of the infant's body temperature may be made. It would clearly be advantageous if the warmer control sound an audible alarm 35 or show a visible alarm if the temperature probe was not securely connected to the infants body. This is especially important since at present a visual inspection is used to determine if a cable is connected to a patient and this is not always sufficient for the user to determine whether the probe 40 is in fact securely connected.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide methods 45 of and/or apparatus for detecting the status of a cable termination which will at least go some way toward overcoming the above disadvantages or which will at least provide the public with a useful choice.
Accordingly, in one aspect, the invention consists in 50 temperature measuring apparatus for measuring a patient's body temperature in a medical environment including a temperature probe having a temperature sensor. The apparatus also including an electric cable containing conductors and having a proximal end and a distal end to which the 55 temperature probe is attached. The temperature probe in use being attached to the patient. An electrically conductive portion of the temperature sensor is adapted to be placed on the patient's body and is in electrical connection with a conductor in the electric cable. There existing a thermal 60 connection of a measurable quality between the temperature sensor and the patient, and means for determining the quality of the thermal connection. The means for determining the quality of the thermal connection comprising pulse generating means having an output connected at the proximal end 65 of the electric cable for generating a pulse of electrical energy on the electric cable which is propagated along the
electric cable towards a load comprising the patient in thermal contact with the temperature probe. Some of the energy of the pulse being reflected by the load as reflected propagating electrical waves having at least one physical characteristic between the proximal and distal ends of the electric cable and some of the energy being absorbed by the load. Signal detection means for detecting the at least one physical characteristic of the reflected propagating electrical waves in response to the pulse are also provided. The reflected propagating electrical waves having a measurable duration and amplitude. The temperature sensor providing a signal indicative of the patient's body temperature to the conductor in the electric cable. Comparing means compare the at least one physical characteristic of the reflected propagating electrical waves with a predetermined signal characteristic to thereby provide an indication of the quality of the thermal connection.
In a second aspect the invention consists in a method of measuring a patient's body temperature in a medical environment with a temperature probe having a temperature probe in use attached to the patient. An electric cable is provided having a proximal end and a distal end to which the temperature probe is attached. There existing a thermal connection of a measurable quality between the temperature sensor and the patient. The method also including detecting the quality of the thermal connection, the method comprising the steps of periodically generating a pulse of electrical energy and applying the pulse to the proximal end the electric cable. Then detecting a characteristic of reflections resulting from the pulse interacting with a load, comprising the patient in thermal connection with the temperature probe, and the proximal end of the electric cable, the reflections having a measurable duration and amplitude. The providing the distal end of the cable with a signal indicative of the temperature sensed by the temperature sensor. Finally comparing the characteristic with a predetermined signal characteristic to determine the quality of the thermal connection.
The invention consists in the foregoing and also envisages constructions of which the following gives examples only.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 and 2 are diagrammatic elevational views of a section through a probe for use with the present invention, and
FIG. 3 is a simplified circuit diagram of the apparatus used in accordance with the present invention, and
FIG. 4 is a graph of amplitude vs time for a waveform produced by the circuitry shown in FIG. 3.
Referring to FIG. 1 a temperature probe is shown generally referenced 1 having a cup constructed from an electrically conductive material such as metal and having a thermally conductive paste 3 therein in which one or more temperature sensors are disposed. The first and second thermosensors 4 and 5 are electrically connected to electronic control circuitry generally referenced 6 by a cable having conductors 7 and 8 and a common conductor 9. The thermosensors are connected to common conductor 9 at point 10 and this common connection is also electrically connected to the metal cup 2 by soldering or clamping for example at point 11.
Referring to FIG. 2, the probe cup of FIG. 1 is again shown only in this probe the connection between the com