Patient temperature repeating system and method

• US 20040252750A1
• Filed: 06/12/2003
• Published: 12/16/2004
• Est. Priority Date: 06/12/2003
• Status: Active Grant

• Current Assignee: Medivance Incorporated (Becton, Dickinson & Co)
• Original Assignee: Medivance Incorporated (Becton, Dickinson & Co)
• Inventors: Carson, Gary A., Proctor, Robert W., Gruszecki, Gary A.
• Granted Patent: US 6,921,198 B2
• Time in Patent Office: Days
• US Class Current: 374/185
• CPC Class Codes: G01K 1/026 arrangements for monitoring a plurality of temperatures, e.g. by multiplexing
• CPC Class Codes: G01K 13/20 Clinical contact thermometers for use with humans or animals

Abstract

A patient temperature repeating system and a method of repeating patient temperature information from a resistive-type patient temperature sensor allow one or more medical instruments to utilize a single patient temperature sensor. In one embodiment, the patient temperature repeating system (10) includes input and output connectors (12, 14), a microprocessor (20), optical isolators (22), a coarse digital potentiometer (24) in parallel with a fine digital potentiometer (26), a current sense resistor (28), amplifiers (30A, 30B), analog-to-digital converters (32A, 32B), a filter (34), fuses (36), a non-volatile memory device (38), and a relay (40). In operation, the microprocessor (20) reads the resistance level of a resistive-type patient temperature sensor (16) connected to the input connector (12) and provides the appropriate control signals through the optical isolators (22) to the coarse and fine digital potentiometers (24, 26) in order to set the resistance seen by a medical device (18) connected to the output connector (14) to match that of the patient temperature sensor (16).

Claims

1. A patient temperature repeating system for repeating a resistance level from a patient temperature sensor that varies its resistance level in accordance with patient temperature whereby the resistance level of the patient temperature sensor is accessible by at least one medical instrument without connecting the patient temperature sensor directly with the medical instrument, said system comprising:

an input connector configured for connection of the patient temperature sensor thereto;

an output connector configured for connection of at least one medical instrument thereto;

a variable resistance device controllable to provide a variable resistance level to said output connector; and

a controller operable to obtain the resistance level provided by a patient temperature sensor connected to said input connector, said controller being further operable to control said variable resistance device to establish the resistance level provided by said variable resistance device to said output connector in accordance with the resistance level obtained from the patient temperature sensor.

2. The system of claim 1 wherein the patient temperature sensor comprises a thermistor.

3. The system of claim 1 wherein the patient temperature sensor comprises a resistive temperature device.

4. The system of claim 1 wherein said variable resistance device comprises at least one potentiometer.

5. The system of claim 4 wherein said variable resistance device comprises at least one coarse digital potentiometer in parallel with at least one fine digital potentiometer.

6. The system of claim 5 wherein said coarse potentiometer is controllable to provide a resistance level of between 100 and 10K ohms in 39 ohm increments and said fine potentiometer is controllable to provide a resistance level of between 100 and 10K ohms in 9.8 ohm increments.

7. The system of claim 1 wherein said variable resistance device comprises at least one field effect transistor, said controller being operable to control a gate-source voltage of said field effect transistor to vary a drain-source resistance level of said field effect transistor.

8. The system of claim 1 wherein said variable resistance device comprises a network of fixed resistors and analog switches, wherein closing different combinations of said switches provides different resistance levels.

9. The system of claim 1 wherein said variable resistance device comprises a network of fixed resistors and relays, wherein operating different combinations of said relays provides different resistance levels.

10. The system of claim 1 wherein said variable resistance device comprises an analog potentiometer coupled with a servo motor, said controller being operable to operate said servo motor to control a resistance level of said analog potentiometer.

11. The system of claim 1 further comprising:

at least one device operable to disconnect said variable resistance device from said output connector.

12. The system of claim 11 wherein said at least one device operable to disconnect said variable resistance device from said output connector comprises one of a relay and an analog switch.

13. The system of claim 1 wherein said controller comprises a microprocessor.

14. The system of claim 13 further comprising:

a memory configurable to store information retrievable by said microprocessor for use in controlling said variable resistance device.

15. The system of claim 14 further comprising:

at least one feedback loop providing information to said microprocessor relating to the resistance level provided by said variable resistance device.

16. The system of claim 15 wherein said feedback loop comprises a first amplifier in series with a first analog-to-digital converter and a second amplifier in series with a second analog-to-digital converter, said first amplifier amplifying a voltage level across said variable resistance device and said second amplifier amplifying a current through said variable resistance device.

17. The system of claim 15 wherein said feedback loop comprises parallel first and second amplifiers in series with an analog multiplexer and an analog-to-digital converter, said first amplifier amplifying a voltage level across said variable resistance device and said second amplifier amplifying a current through said variable resistance device.

18. The system of claim 15 wherein said feedback loop comprises parallel first and second amplifiers in series with a hybrid analog-to-digital converter including multiplexing functionality, said first amplifier amplifying a voltage level across said variable resistance device and said second amplifier amplifying a current through said variable resistance device.

19. The system of claim 15 wherein said input connector and said microprocessor are electrically isolated from said variable resistance device, said output connector, and said feedback loop, and wherein said microprocessor is electrically isolated from said input connector.

20. The system of claim 19 wherein the electrical isolation is provided by at least one optical isolator.

21. The system of claim 19 wherein the electrical isolation is provided by at least one transformer.

22. The system of claim 13 wherein said microprocessor is operable to periodically obtain the resistance level provided by the temperature sensor to said input connector and to periodically establish the resistance level provided by said variable resistance device to said output connector in accordance with the resistance level periodically obtained from the patient temperature sensor.

23. The system of claim 22 wherein said microprocessor periodically obtains the resistance level of the patient temperature sensor and periodically establishes the resistance level of said variable resistance device at least once per every second.

24. The system of claim 1 wherein said controller comprises one of an FPGA, an EPROM, and a flash memory.

25. The system of claim 1 wherein said variable resistance device and said controller are operable to provide a resistance level to said output connector that is within an acceptable tolerance level of the resistance level of the patient temperature sensor.

26. The system of claim 25 wherein the acceptable tolerance level varies from +/−

4.5 ohms at a patient temperature of 42°

C. to +/−

21 ohms at a patient temperature of 10°

C.

27. The system of claim 1 wherein said output connector is configured for simultaneous connection of multiple medical instruments thereto.

28. A method of repeating a resistance level from a patient temperature sensor that varies its resistance level in accordance with patient temperature whereby the resistance level of the patient temperature sensor is accessible by at least one medical instrument without connecting the patient temperature sensor directly with the medical instrument, said method comprising the steps of:

monitoring the resistance level of the patient temperature sensor;

generating a control signal based on the monitored resistance level;

transmitting the control signal to a variable resistance device; and

establishing a setting of the variable resistance device in response to the control signal to provide an output resistance level to the medical instrument which corresponds with the monitored resistance level.

29. The method of claim 28 wherein said steps of monitoring, generating, transmitting and establishing are performed on a periodic basis.

30. The method of claim 28 wherein said steps of monitoring, generating, transmitting and establishing are performed on a continuous basis.

31. The method of claim 28 wherein the variable resistance device comprises a coarse potentiometer in parallel with a fine potentiometer, and wherein, in said step of generating, the control signal is configured to provide for at least one of establishing the setting of the coarse potentiometer and establishing the setting of the fine potentiometer.

32. The method of claim 31 wherein, in said step of generating, the control signal includes a first portion for establishing the setting of the coarse potentiometer and a second portion for establishing the setting of the fine potentiometer.

33. The method of claim 32 wherein said step of generating the control signal includes the step of:

retrieving stored settings for the coarse and fine potentiometers associated with the monitored resistance level.

34. The method of claim 33 further comprising:

performing a calibration process to derive a plurality of settings for the coarse and fine potentiometers associated with a plurality of different monitored resistance levels; and

storing the settings for later retrieval.

35. The method of claim 34 wherein the calibration process is performed for patient temperatures within a predetermined temperature range.

36. The method of claim 34 wherein said step of performing the calibration process includes the steps of:

generating at least one test signal based on a predetermined resistance level;

transmitting the test signal to the variable resistance device to establish an initial setting for the variable resistance device;

monitoring the resistance level of the variable resistive device; and

adjusting the setting of the variable resistance device to identify a final setting for the variable resistance device wherein the variable resistance device provides a resistance level that is within an acceptable tolerance range of the predetermined resistance level.

37. The method of claim 36 wherein said step of monitoring the resistance level of the variable resistive device comprises looping the output resistance level back into an input, and obtaining the resistance level of the variable resistive device from the input.

38. The method of claim 36 wherein, in said step of adjusting the setting of the variable resistance device to identify a final setting for the variable resistance device, the acceptable tolerance range varies from +/−

4.5 ohms at a patient temperature of 42°

C. to +/−

21 ohms at a patient temperature of 10°

C.

39. The method of claim 28 further comprising the step of:

generating a feedback signal from the variable resistance device which is employable for use in said step of generating a control signal.

40. The method of claim 39 further comprising:

generating an alert signal based on said feedback signal.

41. A system for repeating a resistance level from a patient temperature sensor that varies its resistance level in accordance with patient temperature whereby the resistance level of the patient temperature sensor is accessible by at least one medical instrument without connecting the patient temperature sensor directly with the medical instrument, said system comprising:

input means for connecting the patient temperature sensor thereto;

output means for connecting at least one medical instrument thereto;

variable resistance means for providing a variable resistance level to said output means; and

control means for obtaining the resistance level provided by a patient temperature sensor connected to said input means and establishing the resistance level provided by said variable resistance means to said output means in accordance with the resistance level obtained from the patient temperature sensor.

42. The system of claim 41 wherein said input means comprise a plug connector.

43. The system of claim 41 wherein said output means comprise a plug connector.

44. The system of claim 41 wherein said variable resistance means comprise at least one potentiometer.

45. The system of claim 44 wherein said variable resistance means comprises a coarse potentiometer in parallel with a fine potentiometer.

46. The system of claim 41 wherein said variable resistance means comprise at least one field effect transistor, and wherein said control means are operable to control a gate-source voltage of said field effect transistor to vary a drain-source resistance level of said field effect transistor.

47. The system of claim 41 wherein said variable resistance means comprise a network of fixed resistors and analog switches, wherein closing different combinations of said switches provides different resistance levels.

48. The system of claim 41 wherein said variable resistance means comprise a network of fixed resistors and relays, wherein operating different combinations of said relays provides different resistance levels.

49. The system of claim 41 wherein said control means comprise at least one of a microprocessor, an FPGA, an EPROM, and a flash memory.