The object of the invention is to provide an instrument for converting a physiological pulse rate into a corresponding linear output voltage. The instrument which accurately measures the rate of an unknown rectangular pulse wave over an extended range of values comprises a phase-locked loop including a phase comparator, a filtering network, and a voltage-controlled oscillator, arranged in cascade. The phase comparator has a first input responsive to the pulse wave and a second input responsive to the output signal of the voltage-controlled oscillator. The comparator 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 accepts an output from the filtering network and provides an amplified output DC signal to a utilization device for providing a measurement of the rate of the pulse wave

Cooper, Tommy G.

English

NASA Technical Reports Server

United States Patent 1191 [ill Patent Number: 4,936,309 
&Per [45] Date of Patent: Jun. 26, 1990 
OTHER PUBLICATIONS 
Technical Specifications for 4046, RCA Databook, 
Primaly Examiner-Kyle L. Howell 
Assistant Examiner-John C. Hanley 
Attorney, Agent, or Firm-Russell E. Schlorff; John R. 
Manning; =ward K. Fein 
[54] DUAL PHYSIOLOGICAL tGATE 
MEASUREMENT INSTRUMENT 
[75] Inventor: Tommy G. Cooper, Houston, Tex. 1980, pp. 176-181. 
[73] Assignee: The United States of America as 
represented by the Administrator, 
National Aeronautics and Space 
Administrr tion, Washington, D.C, 
[21] Appl. No.: 183,475 
[22] Filed: Apr. 15,1988 
Related US. Application Data 
[63] Continuation of Ser. No. 585,627, Mar. 7, 1984, aban- 
doned, which is a continuation of Ser. No. 394,343, Jul. 
1, 1982, abandoned. 
[51] Int. (3.5 ............................................ A61B 5/0205 
[52] US. ci. .................................... 128/671; 128/689; 
128/706; 128/716; 331/1 R; 331/17; 331/25 
[58] Field of Search ............... 128/687, 689, 706, 671, 
128/716; 324/78; 331/1 A, 1 R, 17,25 
1561 References Cited 
U.S. PATENT DOCUMENTS 
4,182,315 1/1980 Vas et al. ............................ 128/687 
4,414,504 11/1983 Kennedy ........................... 324/78 R 
4,256,008 3/1981 Ryon ................................. 324/78 R 
[571 ABSTRACT 
The object of the invention is to provide an instrument 
for converting a physiological pulse rate into a corre- 
sponding linear output voltage. 
The instrument (1) which accurately measures the rate 
of an unknown rectangular pulse wave (9) over an ex- 
tended 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 depen- 
dent 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 provid- 
ing a measurement of the rate of the pulse wave. 
2 Claims, 2 Drawing Sheets 
ZOK 
I 
. I  I 
o-- 
HEART p-1 HEART 
https://ntrs.nasa.gov/search.jsp?R=19910005396 2020-03-24T06:42:58+00:00Z
U.S. Patent J U ~ .  26,1990 Sheet 1 of 2 4,936,309 
FIG. I. 
PPL 8 - I 
7 
5 ) 6 32 16 
- RE'SP v c o  I RATE 
LOOP 
FILTER 
15 14 . 
- 2 -- DIVIDER - - 
5' 6' . 16' 32' 
14' 13' 
n - HEART LOOP Av c o  ,r 
0 '7 RATE F I LTER 
15' 
H. R. 
FIG. 2, 
I O  
a 
VOLTS 
6 
4 
2 
40 80 120 160 180 
-BEATS PER MINUTE-  
U m S m  Patent J U ~ .  26,1990 Sheet 2 of 2 4,936,309 
- ' \  - M 
Y 
0 
4,936,309 
c) 1 
DUAL PHYSIOLOGICAL RATE MEASUREMENT 
INSTRUMENT 
ORIGIN OF THE INVENTION 5 
The invention described herein was made in the per- 
formance of work under a NASA contract and is sub- 
ject to the provisions of Section 305 of the National 
Aeronautics and Space Act of 1958, Public Law 85-568 
(72 Stat. 435; USC 2457). 
This application is a continuation of application Ser. 
No. 585,627, filed 3/7/84 abandoned which is a continu- 
ation of Ser. No. 394,343, filed 7/01/82 abandoned. 
TECHNICAL FIELD 
The invention relates to an instrument whose basic 
function is to convert one or a pair of physiological 
pulse rates to one or a pair of corresponding linear 
output voltages suitable for monitoring or recording 20 
Purpo=* 
When measuring basic physiological phenomena, 
such as heart beat rate or breath cycle rate, it is essential 
that the instrument have a fast response time, g" 
linearity, and stability over its full operating range. It IS 25 
also desirable that the circuit employs relatively inex- 
pensive and readily available digital and analog inte- 
grated circuits. In addition, the circuitry must be reli- 
able and retain its accuracy over wide changes in envi- 
15 
L 
the light in the blood stream to indicate the t a g  of 
blood pulses. 
DISCLOSURE OF THE INVENTION 
It is a specific object of the present invention to pro- 
vide an instrument capable of measuring simultaneously 
or separately the heart beat rate (HR) and the respira- 
tory cycle rate (RESP) of the same subject. The instru- 
ment is fast responsive, relatively inexpensive, and uti- 
lizes a digital integrated circuit (IC) COSMOS PLL 
that is commercially available and is particularly suit- 
able for making bio-medical measurements. 
This PLL features a phase comparator consisting of a 
digital, positive edge-controlled memory network 
which permits the PLL to be locked in phase and fre- 
quency over the full, relatively-large, operating fre- 
quency range of its VCO. 
BRIEF DESCRIPTION OF DRAWINGS 
The details of the invention will be described in con- 
FIG. 1 is a block diagram of the instrument; 
FIG. 2 is a graph showing the linearity between the 
instrument's output voltage and the input pulse rate; and 
FIG. 3 is a preferred detailed circuit diagram. 
BEST MODE FOR CARRYING OUT THE 
INVENTION 
nection with the accompanying drawings, in which: 
, Referring to the drawing, there is shown a dual mea- ronmental conditions, such a~ are encountered in porn- 30 surement instrument 1, constructed in accordance with 
ble instruments used in remote locations or under space the invention, which two channels 2 and 3, 
flight conditions. each having a phase comparator (PC) 4, a voltage-con- 
trolled oscillator (VCO) 5, a loop filter (LF) 6, and a BACKGROUND ART 
frequency divider 7, all cascaded around a phase-lock 
for measuring PhYsiological rates. u*s. pat. No* After lengthy experimental investigations, it was de- 
4,066,069 relates to a system for detecting differemes termined that by using a PLL and properly selecting the 
between a Pre-rmorded* normal, reference Pulse wave parameters of the components added to the PLL, it is 
Obtained from an electrocardiogram (EcG) and a mea- possible to convert physiological pulse rates under opti- 
sured ECG pulse wave from the same subject. A phase- mum linearity and response time. 
lock (PLL) is used to synchronize the rate of the Instrument 1 receives a pair of rectangular wave 
reference ECG wave with the rate of the measured signals 9, 9 which are derived from a pneumogram and 
ECG wave to Obtain a comparison between theme S F -  cardiogram, respectively. These rectangular wave sig 
cifically, in this patented system a reference heart beat 45 rials are of constant amplitude but they can vary in 
Numerous techniques have been used and proposed 35 loop ~ L L )  8. 
signal is recirculated for comparison with an actual 
heart beat signal. First and second voltages are pro- 
duced having amplitudes respectively representing the 
rate of the reference heart beat and the rate of the actual 
heart beat. A voltagecontrolled millator (VCO) pro- 
duces a signal output having a frequency dependent 
upon the difference between the first and second volt- 
ages. This VCO output signal is used to synchronize the 
reference heart beat signal with the actual heart beat 
signal. 
U.S. Pat. No. 4,202,340 shows a circuit for monitor- 
ing heart activity. The circuit utilizes a sensed cardiac 
parameter indicative of the operation of the heart being 
monitored and generates a probability density function 
from the sensed parameter. The probability density 
function is analyzed and its shape is compared with the 
shape of a probability density function indicative of 
normal cardiac function. The differences in shape are 
used to indicate abnormal cardiac function of the heart 
being monitored. 
U.S. Pat. No. 4,063,551 is concerned with sensing 
blood pulses by emitting an infrared light toward a 
frequency or pulse rate. 
Signal 9 represents the respiration cycle rate of a 
subject, and signal 9 represents his heart beat rate. 
Signal 9 is converted in channel 2, and signal 9 is con- 
Signal 9 is applied to one input 10 of the PC 4. The 
output of divider 7 is applied to the other input 11 of PC 
4. 
The function of PC 4 is to compare the phases and 
55 frequencies of the rectangular wave signals appearing at 
its input terminals 10 and 11 and to produce at its output 
terminal 12 an output signal having a DC voltage indic- 
ative of their phase and frequency error or deviation. 
Under static conditions, the phase and frequency error 
60 between the signals appearing at the two input terminals 
10 and 11 is substantially zero which is taken as the 
reference condition. Under dynamic conditions, the 
instantaneous phase and frequency error between the 
two signals appearing on inputs 10 and 11 fluctuates, 
65 and the output of PC 4 on its output terminal 12 is a 
rectangular wave signal having a DC component and 
an AC component. The DC component is proportional 
50 verted in channel 3. 
blood ;esse1 and monitoring the relativeabsorbtion of to the ph& and frequency error or deviationfrom 0'. 
4,936,309 
3 4 
Due to the action of the PLL 8, the two input rectan- terminal 12 which is linear over a relatively large range 
gular waves appearing on inputs 10 and 11 are forced to (greater than 10 to 1) of pulse rates, as shown in FIG. 2. 
be in phase and to have the same frequency. As a conse- The output signal from terminal 12 is applied to a 
quence, the voltage on output terminal 12 of PC 4 is compensating lead-lag RC network 19 consisting of a 
proportional to the input phase and frequency error to 5 resistor 20 connected in series with a resistor 21 and a 
the PC 4 within the full range of instrument 1. capacitor 22. The junction between resistor 21 and ca- 
In sum, in the absence of an input signal 9, the DC pacitor 22 is connected to the positive input terminal 13 
voltage at output terminal 12 is substantially zero. When of an operational amplifier 16 having a negative feed- 
signal 9 advances in frequency, then the corresponding back resistor 23 between its Output terminal 24 and its 
phase and frequency error is substantially 10 negative input terminal 25. An offset network 26 con- 
neously detected by p c  4 to provide a DC component sisting Of a potentiometer 27 is connected between - 5  
to its output terminal 12 having an amplitude which is 
linearly related to the magnitude of this phase error. 
ne detected signal from the pc 4 appearing at terminal 
12 is applied to the loop filter (LF) 6. 
Essentially, the function of LF 6 is to pass there- 
volts and +5  volts. The amount of offset is controlled 
by a resistor 28 which is connected between potentiom- 
eter 27 and terminal 25. A portion of the amplified 
15 signal from amplifier 16 is obtained from the output of a 
potentiometer 29 connected between output terminal 24 
29 provides a DC voltage to a utilization device 32, 
such as a meter Or 
The DC voltage at terminal 31 is a linear translation 
10. The lead lag network 19 provides to its terminal 13 receives a signal which is a filtered output which is proportional to the rate being 
monitored. Network 19 also optimizes the response time 
is to change the frequency 25 and shape of the signal provided at output terminal 12 of 
chip 180 
through to its fmt output 13 only the DC component and Found 30. The output terminal 31 Of potentiometer 
which appears at the output 12 from the pc 49 
blocking as much as possible the AC component, and to 
the dynamic conditions necessary for proper 20 
phase and frequency tracking by the PLL 8. The second Of the respiratory rate signal to input 
Output l4 from the LF 
applied to the VCO 5. 
The function Of vco 
and phase of the signal appearing at its output terminal 
l5 by a ma&ude and in a direction so a to control the operating 
the phase and frequency error ori&al'Y responsive "Of frequency of the VCO 5 on the IC chip 18. Since the 
the creation Of the DC component at Output l2 frequency ofthe incoming signal 9 is relatively low, it is 
from pc 4' The frequency Of the signal appearing at 30 divided by ten in divider 7 to allow the VCO 5 On the 
si& by ten which all0ws vco to Operate at a much preferably an IC chip 1% sold commercially under No. 
higher frequency- Divider 7 is connected between term 4518. As a consequence, resistor 33 and capacitor 3 can 
Resistor 33 and capacitor 
terminal 15 is relatively low. Divider 7 divides this chip 18 to operate at a higher frequency. Divider is 
minals 11 and 15. have relatively low values which reduce their cost, 
instantaneously the incoming pulse wave 9 into an intel- It is important that amplifier 6 have a relatively high 
ligence DC voltage having deviations Which are Sub- input impedance, say larger than ten times the sum of 
stantially proportional to the frequency deviations of the impedances of resistors 20 and 21. 
signal 9 (FIG. 2). It follows that the signal at terminal 13 me output signal at terminal 31 is linear Over at least 
represents the desired intelligence signal. 40 a ten-to-one range (FIG. 2). Suck linearity over such a 
The intelligence Signal Can be taken directly from wide range was heretofore obtainable only by the use of 
terminal 13 but Preferably it h f i t  amplified by an relatively complex and expensive circuits. 
amplifier 16, The heart beat circuit in channel 3 and the respiratory 
A Circuit diaFam of a Preferred embodiment 0% in- cycle circuit in channel 2 are substantially identical, 
strument 1 is slmwn in HG. 3 9  wherein the same refer- 45 except that the respiratory circuit is required to operate 
erne Characters as in FIG. 1 are used whenever possible over a lower frequency range. Hence, no description of 
for the same parts. the heart beat circuit in channel 3 is herein provided, 
The impedance Pneumogram (IpG) and electrocar- and similar components are designated with the same 
diagram (EcG) which are sensed via electrodes con- reference characters followed by a prime ('). 
nected to the subject being monitored produce signals 50 The maximum: rates for the respiration and heart 
which, after they are amplified, filtered and detected, signals were 64 breaths per minute and 255 beats per 
are the desired rectangular wave Signals 9,9' that repre- minute, which correspond to VCO frequencies of 10.7 
sent the respiratory cycle rate of the subject and the and 42.5 Hz, respectively. The values of the compo- 
heart beat rate, respectively. The Specific techniques nents in the circuit are given on the drawing. These 
employed in sensing the IPG and ECG for producing 55 values can be obtained experimentally, with the aid of 
signals 9 and 9' form no part of this invention and in tables, and with the manufacturer's specifications for IC 
themselves are well known in the bio-medical art. chips 18. 
Signal 9 is applied to the input terminal 10 of a CMOS I claim: 
NO. 4046 IC PLL chip 18 produced by RCA, Motorola 1. A portable physiological rate measurement instru- 
and others. This chip utilizes low power and detects the 60 ment for accurately measuring the rate of an unknown 
positive edges of the incoming pulses 9. Chip 18 is digi- pulse wave over an extended range of rate values, said 
tal and includes a positive-edge triggered PC 4 and a pulse wave having a frequency in the range of 0-4.25 
VCO 5 which perform the functions previously de- hertz, said instrument comprising: a low powered 
scribed in connection with FIG. 1. Chip 18 is character- phase-locked loop including a phase comparator, a fil- 
ized by producing a substantially zero DC voltage at its 65 tering network, a voltage-controlled oscillator and a 
output terminal 12 when signal 9 is removed from input frequency divider arranged in series; said phase com- 
terminal 10, by having a relatively fast response time, parator having a first input responsive to said unknown 
and by developing an output DC voltage at output pulse wave and a second input responsive to the output 
Thus, the PLL 8 tranSlates substantially hearly and 35 increase thermal stability and reduce noise. 
4,936,309 
5 6 
signal of said frequency divider; said phase comparator nected to the input of the voltage controlled oscillator, 
providing an output signal dependent on the difference and a second resistor having a first end connected to the 
in phase and frequency between the signals appearing second and so the first resistor and a second end con- 
on said first and second inputs, said output signal having nected to one end of a capacitor, said capacitor having 
a DC component and an AC component, said phase- 5 another end connected to a voltage reference point; and 
locked loop including an integrated digital chip (443%) a high-input impedance amplifier, the impedance being 
which consists of a positive-edge triggered phase com- at least ten times the s u m  of the resistors of the lead-lag 
parator and a voltagecontrolled oscillator and is char- network, said amplifier having an input connected to 
acterized by producing at the output of the phase com- the second end of said second resistor the amplifier 
parator a signal having a substantially zero amplitude 10 being configured to provide flexible'gain and offset 
when no pulse wave is applied to the first input of the adjustment for calibration, said amplifier having an 
phase comparator; said filter comprising an R-C net- output connected to a utilization device which measures 
work attached to the integrated digital chip to control the instantaneous rate of said pulse wave. 
the operating frequency of the voltage controlled oscil- 2. The instrument set forth in claim 1 in which there 
lator, said filter being constructed and arranged to re- 15 are two phase-locked loops, one for measuring respira- 
spond to a pulse train up to a frequency of 4.25 hertz; tory rate and the other for measuring heart rate, the two 
said network comprising a lead-lag RC network consist- phase-locked loops sharing a frequency divider com- 
ing of a first resistor having a first end connected to the prising IC chip No. 4518. 
- 
output of the phase comparator and a second end con- * * * * *  
20 
25 
30 
35 
40 
45 
50 
55 
60 
65 


Dual physiological rate measurement instrument

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