Apparatus and method for interfacing time-variant signals

• US 20030141916A1
• Filed: 01/30/2002
• Published: 07/31/2003
• Est. Priority Date: 01/30/2002
• Status: Active Grant

• Current Assignee: United States GTM Medical Devices
• Original Assignee: Take Action
• Inventors: Conero, Ronald S.
• Granted Patent: US 7,317,409 B2
• Time in Patent Office: Days
• US Class Current: 327/291
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/4839 combined with drug delivery
• CPC Class Codes: A61B 8/04 Measuring blood pressure
• CPC Class Codes: G01R 31/54 Testing for continuity
• CPC Class Codes: G16H 40/63 for local operation

Abstract

An improved apparatus and method for interfacing a time variant waveform between two hardware environments. In one aspect, the invention comprises a circuit for accurately simulating the output of one or more types of sensing device (e.g., passive bridge pressure transducer) for use with a plurality of different monitoring and/or analysis devices, thereby obviating the need for specialized interface circuitry adapted to each different monitor/analyzer. In one exemplary embodiment, the sensing device comprises a non-invasive blood pressure monitor (NIBPM), which universally interfaces with prior art patient monitors via the interface circuit of the invention. In a second aspect of the invention, an improved NIBPM device incorporating the interface circuit is disclosed. An improved disconnect circuit adapted to sense the status of the electrical connection between the sensing device and monitor is also described.

Claims

1. A circuit adapted to simulate one or more waveforms, comprising:

a digital-to-analog converter (DAC) receiving digital inputs from at least one sensing apparatus adapted to generate at least one time variant waveform, and producing an analog output signal related at least in part to said digital inputs; and

at least one amplifier operatively coupled to the output of said DAC, said at least one amplifier connected in a feedback loop with said DAC to form a floating current source;

wherein said at least one amplifier operates so as to satisfy a predetermined relationship between its output voltage and an applied excitation voltage.

2. The circuit of claim 1, wherein said DAC comprises a multiplying DAC, and said floating current source is bipolar.

3. The circuit of claim 1, wherein said circuit is operatively coupled to a monitoring device, and said analog output signal is further related at least in part to said excitation voltage generated by said monitor device.

4. The circuit of claim 1, wherein said circuit is adapted to interface with one or more of a plurality of different monitoring devices irrespective of the excitation generated by such monitoring device(s).

5. The circuit of claim 4, wherein said circuit is adapted to simulate waveforms having a frequency ranging from 0 Hz (DC) to 200 Hz.

6. The circuit of claim 4, wherein said at least one sensing apparatus comprises an NIBPM, and said circuit is adapted to simulate the output waveform produced by a passive bridge transducer when said passive bridge transducer is applied to measure the blood pressure of a living subject.

7. The circuit of claim 1, further comprising first and second resistors disposed relative to the output of said DAC and said at least one amplifier, the ratio of the resistance values of said first and second resistors determining the scale factor for said circuit.

8. The circuit of claim 3, further comprising at least one filter element disposed in said circuit and adapted to filter signals transferred between said monitoring device and said circuit.

9. The circuit of claim 8, wherein said at least one filter element comprises a choke coil.

10. The circuit of claim 3, further comprising an over-voltage protection element disposed in said circuit and adapted to mitigate voltage transients generated by said monitoring device.

11. The circuit of claim 1, further comprising a test circuit operatively coupled to said circuit adapted to simulate, said test circuit being configured to test the functionality of at least a portion of said circuit adapted to simulate.

12. The circuit of claim 11, wherein said test circuit is adapted to test the functionality during normal operation of said circuit adapted to simulate.

13. The circuit of claim 7, wherein at least one of said first and second resistors is adjustable, thereby rendering said scale factor adjustable.

14. A method for simulating a time-variant output signal from a first device using a second device, comprising:

providing a first device having at least one transfer function associated therewith;

providing said second device, said second device being adapted to sense at least one time-variant parameter and provide a representation based at least in part thereon;

providing an excitation voltage to said second device;

generating a representation of said time-variant parameter using said second device;

applying a transfer function to said representation, said transfer function being substantially similar to that for said first device; and

generating at least one output signal based at least in part on said representation and said transfer function, said at least one output signal being substantially similar to that produced by said first device.

15. The method of claim 14, wherein the act of sensing at least one time-variant parameter comprises sensing a pressure waveform from the blood vessel of a living subject.

16. The method of claim 15, wherein the act of sensing is performed non-invasively.

17. The method of claim 15, wherein said first device comprises a passive bridge element, and the act of generating a representation comprises generating a binary digital representation.

18. The method of claim 17, wherein the act of applying a transfer function comprises:

receiving said binary digital representation at a digital-to-analog converter (DAC);

converting said binary digital representation to an analog representation;

amplifying said analog representation tp produce an amplified signal, said amplified signal being provided to said DAC in a feedback loop and forming a floating current source; and

producing a predetermined relationship between said amplified signal and an excitation signal applied to said second device.

19. The method of claim 16, further comprising buffering said excitation signal.

20. The method of claim 14, further comprising detecting the electrical connection between said second device and an externally applied excitation signal by detecting the presence of a specified impedance value.

21. The method of claim 14, further comprising detecting the electrical connection between said second device and an externally applied excitation signal by detecting the presence of a voltage at a predetermined terminal of the device supplying said excitation signal.

22. A method of determining the status of electrical connection between a monitoring device and a sensing device, wherein said monitoring device provides an excitation signal to said sensing device during operation, comprising:

detecting the presence of the excitation signal provided by said monitoring device;

buffering said excitation signal to produce a buffered excitation signal; and

analyzing said buffered excitation signal to identify variations therein indicative of said status of electrical connection.

23. The method of claim 22, wherein the act of analyzing comprises applying at least one transfer function to said buffered excitation signal.

24. The method of claim 23, wherein the act of applying comprises applying a window comparator transfer function.

25. The method of claim 22, wherein the act of analyzing comprises specifying a time constant adapted to compensate for zero-crossing waveforms or other short-duration voltage transients.

26. Apparatus, comprising:

sensing apparatus adapted to sense at least one waveform, and generate a binary digital representation related thereto; and

an interface circuit operatively coupled to said sensing apparatus, said interface circuit being adapted to applying a transfer function to said digital representation, and generate at least one output signal, said at least one output signal based at least in part on said binary digital representation and said transfer function, said at least one output signal being substantially similar to that produced by a passive bridge device.

27. The apparatus of claim 26, wherein said sensing device comprises a non-invasive blood pressure monitor.

28. The apparatus of claim 27, wherein said binary digital representation comprises data representative of blood pressure obtained from the blood vessel of a living subject.

29. The apparatus of claim 28, wherein said binary digital representation is derived at least in part by calculating time frequency distributions for said at least one waveform.

30. The apparatus of claim 28, wherein said binary digital representation is derived by:

(i) measuring a first parameter from said blood vessel;

(ii) compressing said blood vessel;

(iii) measuring a second parameter from said blood vessel during said act of compressing;

(iv) deriving a calibration function based at least in part on said second parameter; and

(v) calibrating the first parameter using said calibration function.

31. The apparatus of claim 30, wherein said first parameter comprises pressure within said blood vessel, and said second parameter comprises blood flow kinetic energy.

32. The apparatus of claim 26, further comprising a wireless communications interface, said wireless interface being adapted for the communication of data between said sensing apparatus and said interface circuit.

33. The apparatus of claim 26, further comprising a wireless communications interface, said wireless interface being adapted for the communication of data between said apparatus and a monitoring device.

34. The apparatus of claim 32, wherein said wireless interface utilizes radio frequency energy to communicate said data.

35. The apparatus of claim 34, wherein said radio frequency energy is disposed substantially within the ISM band.

36. The apparatus of claim 34, wherein said wireless interface comprises a spread spectrum device.

37. Apparatus for monitoring a time-variant waveform, comprising:

a non-invasive blood pressure sensing device, said device being configured to produce at least a binary digital representation related to said time variant waveform;

interface circuitry in data communication with said sensing device, said interface circuitry being adapted to condition said at least binary digital representation according to at least one transfer function, and produce an analog representation thereof,

a monitoring device, in communication with at least said interface circuitry, adapted to utilize said analog signal for the monitoring of said waveform.

38. The apparatus of claim 37, wherein said sensing device is adapted to sense at least one blood pressure waveform, and said monitor is adapted to either analyze or display information representative of said blood pressure waveform.

39. The apparatus of claim 37, wherein said at least one transfer function substantially replicates that of a passive bridge transducer.

40. The apparatus of claim 38, wherein said at least one transfer function substantially replicates that of a passive bridge transducer.

41. A method of providing treatment to a living subject, comprising;

obtaining data from said subject using a sensing device;

generating a first signal based at least in part on said obtained data;

conditioning said first signal using a conditioning circuit to produce a second signal;

providing said second signal to a monitoring device, said monitoring device producing a representation of a desired parameter; and

providing treatment to said living subject based on said parametric representation.

42. The method of claim 41, wherein said act of conditioning comprises applying a transfer function to said first signal to produce said second signal, said second signal substantially simulating that produced by a passive bridge device compatible with said monitoring device.

43. The method of claim 42, wherein said act of conditioning further comprises conditioning said first signal based at least in part on an excitation signal provided by said monitoring device.

44. The method of claim 42, further comprising:

detecting an excitation signal provided by said monitoring device, said excitation signal being substantially unique to said monitoring device; and

conditioning said first signal based at least in part on said excitation signal;

wherein said second signal is specifically configured for operation with said monitoring device.

45. A circuit adapted to simulate one or more waveforms, comprising:

data conversion means adapted for receiving digital inputs from at least one sensing apparatus, said digital inputs relating to at least one time variant waveform, and converting said digital inputs into an analog output signal; and

means for amplifying said analog output signal, said means for amplifying being connected in a feedback loop with said data conversion means to form a floating current source;

wherein said means for amplifying operates so as to satisfy a predetermined relationship between its output voltage and an applied excitation voltage.

46. A method for simulating a time-variant output signal from a first sensing means using a second sensing means, comprising the steps of:

providing said second sensing means, said second sensing means being adapted for sensing at least one time-variant parameter and providing a representation based at least in part thereon;

providing an excitation voltage to said second sensing means for exciting same;

generating a representation of said time-variant parameter using said second sensing means;

applying a transfer function to said representation for conditioning of said representation, said transfer function being substantially similar to that for said first sensing means; and

generating at least one output signal for use by a monitoring device, said at least one output signal being based at least in part on said representation and said transfer function, and being substantially similar to that produced by said first sensing means.

47. Apparatus, comprising:

first means for sensing at least one waveform, said means for sensing further being adapted to generate a binary digital representation related to said at least one waveform; and

interface means operatively coupled to said first means for sensing, said interface means being adapted to applying a transfer function to said binary digital representation, and generate at least one output signal, said at least one output signal based at least in part on said binary digital representation and said transfer function, said at least one output signal being substantially similar to that produced by a second means for sensing.

48. Apparatus for interfacing a sensing device to a monitoring device, comprising:

a first data interface in data communication with said sensing device;

an interface circuit in data communication with said first data interface; and

a second data interface in data communication with said monitoring device;

wherein said interface circuit is adapted to receive first data generated by said sensing device, said data relating at least in part to a time-variant waveform sensed by said sensing device, and condition said first data so as to produce second data, said second data being adapted for use by said monitoring device.

49. The apparatus of claim 48, wherein said interface circuit is further adapted to condition said first data such that said second data is compatible with said monitoring device regardless of the type of said monitoring device.

50. The apparatus of claim 48, wherein said interface circuit is further adapted to condition said first data such that said apparatus, and said second data produced thereby, is compatible with a plurality of different monitoring device types.

51. The apparatus of claim 48, wherein said first data interface comprises at least one electrical connector mounted on at least one electrical conductor.

52. The apparatus of claim 48, wherein said first data interface comprises a wireless data link.