Dual physiological rate measurement instrument

• US 4,936,309 A
• Filed: 04/15/1988
• Issued: 06/26/1990
• Est. Priority Date: 03/07/1984
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: The United States of America As Represented By The Secretary of Agriculture
• Inventors: Cooper, Tommy G.
• Primary Examiner(s): Howell, Kyle L.
• Assistant Examiner(s): Hanley, John C.
• Application Number:
  US07/183,475
• Time in Patent Office: 802 Days
• Field of Search: 128/687, 128/689, 128/706, 128/671, 128/716, 324/78, 331/1 A, 331/1 R, 331/17, 331/25
• US Class Current: 600/484
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00

Abstract

The object of the invention is to provide an instrument for converting a physiological pulse rate into a corresponding linear output voltage.

The instrument (1) which accurately measures the rate of an unknown rectangular pulse wave (9) over an extended range of values, comprises a phase-locked loop (8) including a phase comparator (4), a filtering network (6), and a voltage-controlled oscillator (5), arranged in cascade. The phase comparator has a first input (10) responsive to the pulse wave and a second input (11) responsive to the output signal of the voltage-controlled oscillator. The comparator (4) provides a signal dependent on the difference in phase and frequency between the signals appearing on the first and second inputs. A high-input impedance amplifier (16) accepts an output from the filtering network and provides an amplified output DC signal to a utilization device (16) for providing a measurement of the rate of the pulse wave.

Claims

1. A portable physiological rate measurement instrument for accurately measuring the rate of an unknown pulse wave over an extended range of rate values, said pulse wave having a frequency in the range of 0-4.25 hertz, said instrument comprising:

a low powered phase-locked loop including a phase comparator, a filtering network, a voltage-controlled oscillator and a frequency divider arranged in series;

said phase comparator having a first input responsive to said unknown pulse wave and a second input responsive to the output signal of said frequency divider;

said phase comparator providing an output signal dependent on the difference in phase and frequency between the signals appearing on said first and second inputs, said output signal having a DC component and an AC component, said phase-locked loop including an integrated digital chip (4046) which consists of a positive-edge triggered phase comparator and a voltage-controlled oscillator and is characterized by producing at the output of the phase comparator a signal having a substantially zero amplitude when no pulse wave is applied to the first input of the phase comparator;

said filter comprising an R-C network attached to the integrated digital chip to control the operating frequency of the voltage controlled oscillator, said filter being constructed and arranged to respond to a pulse train up to a frequency of 4.25 hertz;

said network comprising a lead-lag RC network consisting of a first resistor having a first end connected to the output of the phase comparator and a second end connected to the input of the voltage controlled oscillator, and a second resistor having a first end connected to the second and so the first resistor and a second end connected to one end of a capacitor, said capacitor having another end connected to a voltage reference point; and

a high-input impedance amplifier, the impedance being at least ten times the sum of the resistors of the lead-lag network, said amplifier having an input connected to the second end of said second resistor the amplifier being configured to provide flexible gain and offset adjustment for calibration, said amplifier having an output connected to a utilization device which measures the instantaneous rate of said pulse wave.

2. The instrument set forth in claim 1 in which there are two phase-locked loops, one for measuring respiratory rate and the other for measuring heart rate, the two phase-locked loops sharing a frequency divider comprising IC chip No. 4518.