PHYSIOLOGICAL MEASUREMENT DISPLAY SYSTEM

• US 3,872,455 A
• Filed: 11/13/1972
• Issued: 03/18/1975
• Est. Priority Date: 11/17/1971
• Status: Expired due to Term

• Current Assignee: Carl E. Herring, Charles H. Fuller
• Original Assignee: Carl E. Herring, Charles H. Fuller
• Inventors: Fuller, Charles H., Herring, Carl E.
• Primary Examiner(s): Habecker, Thomas B.
• Application Number:
  US05/306,253
• Time in Patent Office: 855 Days
• Field of Search: 340/347AD,206,207 128/2.1A 73/362AR 325/113 324/78D 343/842
• US Class Current: 340/870.05
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/0008 Temperature signals
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: G01K 1/024 for remote indication
• CPC Class Codes: H03K 3/30 using a transformer for feedback, e.g. blocking oscillator
• CPC Class Codes: Y10S 128/903 Radio telemetry

Abstract

A system for receiving and displaying data generated by a transmitter having an output pulse rate corresponding to a measured parameter is disclosed. A portable receiver is provided which includes means for detecting weak signals having a repetitive burst rate, means for locking onto the burst rate and producing a corresponding train of pulses, means for counting the number of pulses received during a predetermined time period and means for displaying a number related to the received pulse rate to provide a digital representation of the monitored parameter. The system further includes means for compensating for nonlinearities in the pulse rate of the received signals due to known non-linearities in the signal generator, and includes means for disabling the display in the event of an incomplete measurement, whereby accuracy of the display is assured. The receiver is particularly useful in combination with a physiological sensor-transmitter which produces signals having a pulse rate related to a measured parameter, such as temperature.

Claims

1. A system for transmitting and receiving signals corresponding to a physiological parameter of a subject, comprising:

a sensing element adapted to detect a desired physiological parameter of the subject;

a transmitter adapted to transmit radio frequency signals modulated in accordance with signals that correspond to the detected physiological parameter, and a receiver unit adapted to inductively receive said transmitted signals, said receiver unit including demodulator means for producing a train of pulses at a frequency corresponding to the frequency of modulation of said radio frequency siganls;

phase lock circuit means adapted to generate a range of frequencies that overlaps said frequency of modulation, said phase lock circuit means being connected to receive and compare the pulses developed at the output of said demodulator with said range of frequencies, whereby said phase lock circuit means locks onto, and thereafter generates output pulses at a rate corresponding to, said frequency of modulation; and

means responsive to said output pulses for measuring the burst rate of the received radio frequency signals to indicate the magnitude of said physiological parameter.

2. The system of claim 1, wherein said means responsive to said output pulses comprises:

a timer unit including a clock-pulse source, a timer counter, and means for feeding clock pulses from said clock pulse source to said timer counter;

means for producing a first predetermined number of auxiliary pulses during a first timer interval;

means controlled by said timer unit for gating said output pulses during a second timer interval;

accumulator means; and

means controlled by said gated pulses and by said auxiliary pulses for storing in said accumulator means a manifestation of a total-number representing the value of said parameter.

3. The system of claim 2, further including a device for displaying numbers in visible form, and means controlled by said accumulator means for operating said device to display invisible form numbers corresponding to the total number of pulses in said accumulator means.

4. The system of claim 2, further including means for modifying said second time interval to compensate for nonlinearities in the output characteristic of said transmitter.

5. The system of claim 4 wherein said means for modifying said second time interval comprises scanning means for feeding to said timer counter both said clock pulses and said output pulses to increase the counting rate of said timer counter.

6. The system of claim 5, further including gate means for preventing said output pulses from reaching said summing means during a predetermined portion of said second time interval.

7. A telemetering system for monitoring a physiological parameter of a plurality of spaced apart patients respectively, comprising:

a separate telemetering transmitter mounted on each of the different patients, each of said transmitters comprising a blocking oscillator adapted to generate carrier waves of about the same radio frequency at a burst rate that corresponds to the physiological condition of the patient on which said each transmitter is mounted, and a single telemetering receiver for receiving signals at the aforesaid radio frequencies, said receiver including a. a demodulator having a pulse-amplitude discrimination circuit whereby the strongest of the signals received from said transmitters are detected and signals from other transmitters are suppressed, and b. means responsive to the output of said demodulator for measuring the burst rate of the received signals to indicate the physiological parameter of the patient on which the corresponding transmitter is mounted without interference from signals of any other of said transmitters.

8. The telemetering system of claim 7, wherein said means for measuring the burst rate of said received signals comprises:

an accumulator for storing a total-number in digital form;

auxiliary means for producing a set of digital signals that are at least partially dependent on the value of said parameter at a zero burst rate;

a timer unit, including a clock pulse source, and a timer counter;

starter means for initiating operation of output counter, said timer unit, and said auxiliary means;

means controlled by said starter means for feeding pulses from said clock pulse source to said timer counter whereby a timing operation is initiated;

means controlled by said starter means for feeding said set of digital pulses to said accumulator;

means controlled by said timer unit for feeding pulses corresponding to said burst rate to said accumulator; and

means controlled by said timer unit when the number of clock pulses fed to the timer counter has reached a predetErmined count for discontinuing the feeding of further pulses to said accumulator.

9. The telemetering system of claim 8, further including means for modifying said timer unit whereby the time elapsed for reaching said predetermined count is varied in accordance with said burst rate.

10. The telemetering system of claim 9, wherein said means for modifying said timer unit includes means for feeding said pulses corresponding to said burst rate to said timer counter.

11. The telemetering system of claim 10, wherein said means for discontinuing the feeding of further pulses to said accumulator comprises blanking means for disabling said clock pulse source.

12. The telemetering system of claim 11, further including display means responsive to the total number of pulses in said accumulator to display a digital representation of the physiological parameter of the transmitter signals being received.

13. The telemetering system of claim 7, further including phase lock means responsive to the output of said demodulator for producing a stable square wave pulse train having a repetition rate equal to the average repetition rate of said demodulator output.

14. The telemetering system of claim 7, wherein said means for measuring the burst rate of the received signals includes compensating means for correcting for nonlinearities in the burst rates of the signals generated by said transmitters.

15. The telemetering system of claim 14, wherein said compensating means utilizes the burst rate of the received signal for correcting for said nonlinearities.

16. In a system for measuring the burst rate of a train of bursts of radio frequency signals;

a receiver tuned to receive such radio frequency signals;

a demodulator operated by said receiver for producing a train of pulses at a frequency corresponding to the burst rate;

pulse shaping means including a phase lock circuit adapted to sweep over a range of frequencies that overlaps the burst rate, said phase lock circuit being connected to receive the pulses developed by said demodulator whereby said phase lock circuit generates output pulses at a rate corresponding to said burst rate;

measuring means responsive to said output pulses for producing a signal that depends on the burst rate of the received radio frequency signals.

17. A system as defined in claim 16 wherein said output pulses are rectangular and wherein said measuring means comprises a pulse counter and time-gated means for operating said pulse counter to measure the number of pulses applied to it in a predetermined time interval.

18. The system of claim 17, further including locking means responsive to the generation by said phase lock circuit of said output pulses to enable said measuring means, whereby said measuring means is capable of measuring said burst rate only when a phase lock exists between said output pulses and said pulses developed by said demodulator.

19. The system of claim 18, wherein said measuring means includes a timing counter;

clock means for driving said counter;

accumulator means; and

first gate means controlled by said timing counter for applying said output pulses to said accumulator means over a period of time.

20. The system of claim 19 wherein said measuring means further includes second gate means controlled by said timing counter for applying said output pulses to drive said timing counter to vary said period of time in proportion to said burst rate.

21. The system of claim 20, wherein said measuring means further includes third gate means controlled by said timing counter for applying said output pulses to said timing counter over only a portion of said period of time.

22. The system of claim 21, wherein said measuring means further includes fourth gating means for applying to said accumulator means a fixed number of auxiliary pulses, whereby the total number of output pulses and auxiliary pulses applied to said accumulator means represents said burst rate.

23. In a teLemetering system for monitoring the variable physiological conditions of a plurality of living subjects that are spaced apart by a predetermined minimum distance, separate telemetering transmitters mounted on the respective subjects to generate carrier wave signals of about the same radio frequency with the carrier wave signals being emitted in bursts from each transmitter at an audio frequency that corresponds to the value of the physiological condition of the said respective subjects, said carrier wave signals having a length much greater than said minimum distance;

the power of each transmitter being such that the signal-to-noise ratio thereof is less than 1 unit beyond said minimum distance;

a single telemetering receiver for receiving carrier wave signals at the aforesaid radio frequencies simultaneously from a plurality of said transmitters; and

means connected to said receiver for selectively generating pulses that correspond to bursts of the strongest of said carrier wave signals, and means responsive to said pulses for measuring said burst rate to indicate the physiological condition of the subject from which said strongest of said carrier wave signals is received.

24. The system of claim 23, wherein said means for selectively generating pulses comprises:

a demodulator having an automatic gain control circuit for producing at its output detected pulses corresponding to the bursts of received radio frequency signals; and

a phase lock unit responsive to said detected pulses for producing a stream of pulses at the output thereof at a rate corresponding to the burst rate of said received carrier wave signals, said phase lock unit including an oscillator and means for sweeping the frequency of oscillation from a high value above said burst rate to a low value below said burst rate, and means controlled by said detected pulses for locking the frequency of oscillation to the burst rate of said strongest of said carrier wave signals.

25. The system of claim 24, wherein said means responsive to said pulses for measuring said burst rate comprises:

a timer unit;

an accumulator;

gate means controlled by said timer unit for feeding said stream of pulses to said accumulator for a predetermined period of time;

starter means for initiating operation of said receiver, said accumulator, and said timer unit;

means controlled by said starter means to initiate operation of said receiver unit and to delay the initiation of operation of said timer unit and said accumulator for a period of time sufficient to permit said phase lock unit to be locked with the received bursts of radio-frequency signals at said burst rate.

26. In a system for representing the value of a parameter that is a function of the pulse rate of a stream of input pulses which function is characterized by an intercept A at the 0 pulse rate, said system having input means for receiving such a stream of input pulses and a digital output counter for storing a manifestation of a total-number in digital form, the improvement that comprises:

a timer unit including a clock pulse source, a timer counter, and means for feeding clock pulses from said clock pulse source to said timer counter;

means controlled by said timer unit for gating input pulses during a first timer interval;

auxiliary means for producing an auxiliary digital signal that is at least partially dependent on the value of said intercept A;

means controlled by said gated pulses and by said auxiliary digital signal for storing in said output counter a manifestation of a total-number representing the value of said parameter.

27. In a system as defined in claim 26, a device for displaying numbers in visible form, and means controlled by received pulses for operating said device to display numbers stored in said output counter only when the total-number stored exceeds a predetermined amount.

28. The system of claim 27, wherein said timer unit includes a Clock pulse source, a timer counter for counting clock pulses from said clock pulse source and a decoder adapted to detect when the number of clock pulses counted has reached a value corresponding to the value of said parameter;

starter means for initiating operation of said output counter, said time means, and said auxiliary means; and

means controlled jointly by said decoder means and by said auxiliary means for storing in said digital output counter a manifestation of a total-number corresponding to the value of said parameter.

29. In a system for representing the value of a parameter that is a function of the pulse rate of a stream of pulses over a limited range of pulse rates and which function is characterized by an intercept A at 0 pulse rate, the improvement that comprises:

an output counter for storing a total-number in digital form;

auxiliary means for producing a set of digital signals that are at least partially dependent on the value of said intercept;

input means for receiving such a stream of pulses;

a timer unit, including a clock pulse source, and a timer counter;

starter means for initiating operation of said output counter, said timer unit, and said auxiliary means;

means controlled by said starter means for feeding pulses from said clock pulse source to said timer counter whereby a timing operation is initiated;

means controlled by said starter means for feeding input pulses to said output counter; and

means controlled by said timer unit when the number of clock pulses fed to the timer counter has reached a count corresponding to a determined time period for discontinuing the feeding of further input pulses to said output counter.

30. In a system for representing the value of a physiological parameter which involves the detection of the value of said parameter and the transmission of radio frequency signals from a transmitter in a stream of bursts at a burst rate that is a function of the detected value of the physiological parameter which function is characterized by an intercept A at 0 pulse rate:

a radio-frequency receiver unit including means for receiving said bursts of radio-frequency signals and for converting the bursts of received signals into a stream of pulses that have a frequency proportional to the burst rate of said radio-frequency signals;

means for producing an auxiliary digital signal representing a number corresponding to said intercept A;

means for gating pulses in said stream during a selected time interval proportional to said burst rate;

an output counter; and

means controlled by said auxiliary digital signal and said gated pulses for storing in said output counter a digital manifestation of the sum of said numbers, thereby representing the value of said physiological parameter.

31. A system as defined in claim 30, said receiver unit including a demodulator having an automatic gain control circuit for producing at its output detected pulses corresponding to the bursts of received radio frequency signals;

a phase lock unit responsive to said detected pulses for producing said stream of pulses at the output thereof, said phase lock unit including an oscillator and means for sweeping the frequency of oscillation from a high value above said burst rate to a low value below said burst rate, and means controlled by said detected pulses for locking the frequency of oscillation to the burst rate;

starting means for initiating operation of said receiver unit, said output counter, said means for gating, and said means for producing an auxiliary digital signal; and

means controlled by said starting means to delay the initiation of operation of said means for gating and said output counter for a period of time sufficient to permit said phase lock unit to be locked with the received bursts of radio frequency signals at said burst rate.

32. In a system as defined in claim 31, a device for visibly digital numbers in visible form;

and means for operating said device to display the total number stored in said output counter only when the total number stored exceeds a predetermined amount.

33. A system for transmitting and receiving signals corresponding to a physiological parameter of a subject, comprising:

a sensing element adapted to detect the value of said physiological parameter;

a transmitter controlled by said sensing element to produce a modulated radio frequency magnetic field, said magnetic field being modulated in accordance with the value of the detected parameter;

a receiver including antenna means for inductively receiving within the extreme-near-field region of said transmitter said modulated radio frequency magnetic field;

electrostatic shield means for said antenna for reducing electrostatic radiation to and from said receiver without substantially reducing the reception of said magnetic field;

phase lock means within said receiver and responsive to the modulation of said magnetic field for detecting the average rate of a repetitive component of said modulation and rejecting noise caused by interfering magnetic fields; and

means responsive to said average rate for determining the value of said parameter.

34. The system of claim 33, wherein said means for determining the value of said parameter includes:

means producing output pulses at said average rate;

means accumulating a predetermined number of count pulses during a first time period and a variable number of count pulses during a second time period; and

means responsive to said output pulses for varying said second time period in accordance with said average rate to compensate for nonlinearities in the relationship between said modulation and the value of said detected parameter, whereby the value of said parameter may be accurately determined by the total number of count pulses accumulated during said first and second time periods.

35. The system of claim 33, wherein said means for determining the value of said parameter includes counter means responsive to said average rate for producing count pulses at a rate which corresponds to said average rate, and accumulator means receiving and accumulating pulses produced at said average rate for a period of time defined by a predetermined number of said count pulses, said period of time varying in accordance with said average rate to compensate for nonlinearities in the relationship between the modulation of said transmitted magnetic field and the measured value of said parameter, whereby the value of said parameter is accurately determined.

36. The system of claim 33, wherein said transmitter includes antenna means for inductively transmitting said modulated radio frequency magnetic field, and electrostatic shield means for said transmitter antenna to reduce electrostatic radiation to and from said transmitter without substantially reducing the magnetic inductive transmission to the receiver.

37. The system of claim 36, wherein said transmitter antenna includes a tubular core of carbonyl iron and an antenna winding wound on said core, said transmitting antenna electrostatic shield encircling said winding and covering one end of said core.

38. The system of claim 36, wherein said transmitter comprises a blocking oscillator responsive to changes in said sensing element to emit bursts of radio frequency signals at a rate substantially propositional to said measured parameter, said means for determing the value of said parameter compensating for nonlinearities in the change of said burst rate with changes in said measured parameter.

39. A system for transmitting and receiving signals corresponding to a physiological parameter of a subject, comprising:

sensing means responsive to the value of said parameter;

transmitter means controlled by said sensing means for producing a varying magnetic field modulated in accordance with the value of said parameter;

receiveR means responsive to said modulated magnetic field;

means connected to said receiver means producing output pulses at a rate corresponding to a repetitive component of said modulated magnetic field;

means accumulating said output pulses over a predetermined period of time; and

means for varying said predetermined period of time in accordance with said rate to compensate for nonlinearities in the generation and transmission of said rate.

40. The system of claim 39, wherein said means producing output pulses includes means detecting the average rate of said repetitive component of said modulated magnetic field, whereby interfering magnetic fields are rejected by said receiver, and producing said output pulses at said average rate.

41. The system of claim 40, wherein said means for detecting the average rate of the repetitive component of a received modulated magnetic field comprises a phase lock circuit which locks onto, and thereafter generates output pulses at, a rate corresponding to the modulation of said magnetic field.

42. The system of claim 41, wherein said transmitted magnetic field is burst modulated at a rate which is substantially proportional to the value of said parameter, and wherein said output pulses are generated at a rate corresponding to the average rate of said burst modulation.