GB2110363A - Pulse curve analyser - Google Patents
Pulse curve analyser Download PDFInfo
- Publication number
- GB2110363A GB2110363A GB08135517A GB8135517A GB2110363A GB 2110363 A GB2110363 A GB 2110363A GB 08135517 A GB08135517 A GB 08135517A GB 8135517 A GB8135517 A GB 8135517A GB 2110363 A GB2110363 A GB 2110363A
- Authority
- GB
- United Kingdom
- Prior art keywords
- waveform
- pulse
- output
- pulse curve
- time
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 230000000694 effects Effects 0.000 claims abstract description 10
- 230000008859 change Effects 0.000 claims abstract description 9
- 239000008280 blood Substances 0.000 claims abstract description 7
- 210000004369 blood Anatomy 0.000 claims abstract description 7
- 230000000541 pulsatile effect Effects 0.000 claims abstract description 5
- 230000008822 capillary blood flow Effects 0.000 claims description 3
- 230000000630 rising effect Effects 0.000 claims description 2
- 230000001052 transient effect Effects 0.000 claims description 2
- 210000001519 tissue Anatomy 0.000 description 7
- 230000004089 microcirculation Effects 0.000 description 6
- 238000005259 measurement Methods 0.000 description 5
- 230000004087 circulation Effects 0.000 description 4
- 230000010412 perfusion Effects 0.000 description 4
- 230000002829 reductive effect Effects 0.000 description 3
- 230000017531 blood circulation Effects 0.000 description 2
- 210000004204 blood vessel Anatomy 0.000 description 2
- 210000004400 mucous membrane Anatomy 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 1
- 210000002565 arteriole Anatomy 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 238000013211 curve analysis Methods 0.000 description 1
- 238000006392 deoxygenation reaction Methods 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 230000001575 pathological effect Effects 0.000 description 1
- 230000008288 physiological mechanism Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000001020 rhythmical effect Effects 0.000 description 1
- 210000000264 venule Anatomy 0.000 description 1
- 230000035899 viability Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
- G01R29/02—Measuring characteristics of individual pulses, e.g. deviation from pulse flatness, rise time or duration
- G01R29/027—Indicating that a pulse characteristic is either above or below a predetermined value or within or beyond a predetermined range of values
- G01R29/0276—Indicating that a pulse characteristic is either above or below a predetermined value or within or beyond a predetermined range of values the pulse characteristic being rise time
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
- A61B5/024—Detecting, measuring or recording pulse rate or heart rate
- A61B5/02416—Detecting, measuring or recording pulse rate or heart rate using photoplethysmograph signals, e.g. generated by infrared radiation
Abstract
A pulse curve analyser comprising a light-responsive transducer for sensing a patient's continuous physiological circulatory activity to produce a voltage waveform which is an analogue of said patient's body tissue pulsatile blood colour and/or density changes, means for processing said waveform to produce a signal proportional to the rate of change of the amplitude of said waveform and to produce thereby a signal representing the rise time (Tr) and/or the fall time (Tf) of each pulse cycle of said waveform as a function of the period (T) of said cycle, and means for displaying instantaneously the value of the function. <IMAGE>
Description
SPECIFICATION
Pulse curve analyser
This invention relates to electronic means for observing and/or measuring certain properties of the blood circulation in a living body.
Maintenance of life and viability of tissue cells depends on the physiological movement of blood in capillary circulation. The capillary circulation is contained by the small blood vessel network within which it is embraced between arterioles and venules. The capillary system is the interface between arterial and venous blood through all body tissue.#The small vessel circulation is commonly referred to as the micro-circulation.
The blood volume is contained by the microcirculation and the macro-circulation.
The macro-circulation includes the heart and blood vessels external to the micro-circulation.
Traditional parameters of E.C.G., B.P. etc. are directed at the macro-circulation.
Macrocirculatory parameters do not measure or reflect capillary activity or the effect of microcirculatory fluctuations.
The Stephens Tissue Perfusion Monitor or
STPM (the subject of my Australian Patent No.
465,302) samples and quantifies a signal from capillary circulation near skin surface to produce a measurement which is derived colorimetrically and non-invasively from micro-circulation in skin.
The measurement, the Tissue Perfusion Index (TPI), is able to follow microcirculatory fluctuations and so provides indication of stability or change in activity of pulsatile micro-circulation at capillary level relative to an absolute reference level (say, 500 mV).
However, blood flow is a rhythmic activity capable of precise mathematical representation of curve shape in a sequence of analogue pulse curves. Despite the value of such a parameter as the TPI, the existing Tissue Perfusion Monitor is not intended to distinguish between differently shaped curves having the same area beneath them.
An object of the present invention therefore is to provide further information based on the shape of a pulse curve. Analogue pulse curve signals from either micro- or macro-circulatory sources can be monitored accordingly, and their differences measured and compared. It is known that various factors influence pulsatile microcirculatory flow and in so doing alter the shape and/or amplitude of the curve. The measurement of these changes can add diagnostic information of value.
It is a further object of this invention to analyse and display parameters which relate to the shape of the pulse curve in terms of curve rise time "Tr" or curve fall time 'if" and to the "rise/fall ratio" of the curve and to the rise and fall times, "Tr" and 'if", relative to the pulse period "T".
It is yet another object of the invention to identify the positional presence of pressure wave effects such as the dichrotic notch in the basic curve cycle and to note significant inconsistencies and variations.
In one particular embodiment of the invention hereinafter described, continuous readouts are provided of the rise time "Tr" (m.sec.) and of the fall time "Tf" (m.sec.) and of the rise time of each pulse curve expressed in direct relation to the fall time, TFVTF, or of the rise or fall times expressed as a fraction of curve cycle period Tr/T or Tf/T. The data is correlated with the pulse rate to produce absolute parameters in milliseconds. In the case of the capillary the physiological mechanism involved in the analogue curve rise time is indicative of the time taken to "load" the capillary within the micro-circulation, a normal adult human digital skin loading time usually approximating 0.2 secs. with considerable variation of the fall time which corresponds to the reductive phase of the cycle.The considerable variation in fall time relates mostly to change in pulse rate, but can sometimes be due to pathological disturbances.
According to the invention therefore, a pulse curve analyser comprises, in combination, lightresponsive transducer means for sensing a patient's continuous physiological circulatory activity to produce a voltage waveform which is an analogue of said patient's body tissue pulsatile blood colour and/or density changes, means for processing said waveform to produce an output signal proportional to the time range of change of the amplitude of said waveform, and means for displaying quantitatively and instantaneously the rise time and/or the fall time representative of a transient cycle of said waveform as a function of the period of said cycle.
One particular embodiment of the invention defined in the preceding paragraph will now be described with reference to the accompanying drawings, in which.~ Figure 1 shows a mathematical representation of a pulse curve with its amplitude plotted against time,
Figures 2 to 5 show the circuit of a tissue perfusion monitor,
Figures 6 to 1 1 show the circuit of a pulse curve analyser wherein:
Figure 6 includes notch filter and input amplifier circuits,
Figure 7 includes a differentiator, a low pass filter and a Schmitt trigger,
Figures 8 and 10 include a
detector/multiplexer,
Figure 9 includes a digital display unit, and
Figure 1 1 represents a power supply unit.
Upon referring to the drawings it will be seen that a transducer is adapted to derive an electrical signal from a patient's body, for example, in a
manner similar to that described in the specification of my Australian Patent No.
465,302. Indeed, for convenience, this signal fed to the analogue curve analysis monitor may be taken from the pulse curve and pulse rate output terminals of the STPM.
Where a specified transducer such as above
indicated is applied to the surface of mucous membrane or skin, a signal is derived as follows:- Light from a light source within the transducer assembly becomes modulated by changes in activity of capillary blood circulation, and the so modulated light then falls on a detector which creates a wave form signal. The resulting waveform signal passes to the notch filter, which is used to remove interference at power frequencies from induction or optical pick up. Said filter has a standard twin T circuit, tuned appropriately to, say, 50 Hz or 60 Hz.
R10 is used to trim the filter to the centre frequency of any interference. The signal then passes to U1 which is an operational amplifier set up with adjustable gain over the range 25-65 dB. The output of this stage is buffered by U2 and passes to the host STPM to provide a CRO display, located either in the STPM or elsewhere.
The output of U1 also passes to U3 which acts to differentiate the pulse curve. Thus the output of
U3 is proportional to the time rate of change of input voltage. U4 functions as a 2-pole low pass filter with linear phase. When properly offset (via
R34) the output of U4 will be negative when the pulse curve voltage is rising, and positive when the pulse curve voltage is falling. The magnitude of this differential voltage is proportional to both the magnitude of the input voltage and its time rate of change.
The Schmitt trigger US will square up the output of U4, which then passes to the twin detector/filters consisting of U6, R37-44 and C9-1 2. The output of these two detectors is proportional to the fractional rise time (across
R40) and the fractional fall time (across R44).
These outputs are fractional to the pulse period, and are thus complementary.
The multiplexer consisting of US and U9 is used to apply the chosen set of inputs to U7, which is a true ratio-metric voltmeter integrated circuit. The values of fractional rise and fall times are displayed by placing the output of the appropriate detector on the signal input of the digital voltmeter, with a standard voltage from
R48 on the reference inputs.
Actual curve rise times and curve fall times in milliseconds are displayed by placing the appropriate detector output on the voltmeter signal input, and a voltage proportional to the pulse rate, obtained from the host STPM (via R45,
R46) on the reference input.
Alternatively, if needed, the ratio of rise time to fall time can be displayed by placing the rise time detector output on the signal input, and the fall time detector on the reference input.
The calculated output is read numerically in this instance from an LCD readout driven by U7.
The product of '7" the pulse period and "Tr/T" can be displayed as an index in milliseconds of micro-circulatory loading time. Again, the product of 'T" and "Tf/T" can be displayed as an index in milliseconds of the reductive phase Tf.
Indeed, the information may be presented in several different formats, viz:~ (a) Rise time in milliseconds (Tr)
(b) Fall time in milliseconds (Tf).
(c) Rise time as a fraction of pulse period (Tr/T).
(d) Fall time as a fraction of pulse period (Tf/T).
(e) Rise time divided by fall time, as a fraction (Tr/Tf).
If desired, the readings for Tr/T and Tf/T or Tr/Tf may be selected by a multi-position switch, using the arrangement indicated in Figure 10. Thus, with Tr/Tf (i.e. rise time to fall time ratio), when the rise time changes, a small increase in rise time in comparison with the relative reduction in the fall time discriminates change more sensitively than where the denominator is constant as in Tr/T orTf/T.
The invention demonstrates that physiologically significant variations in rise time to fall time ratio readings do not necessarily correlate with TPI readings derived in common from a patient.
In conclusion therefore, it will be seen that a pulse curve analyser, constructed in accordance with the invention, provides information, from a pulse curve, which can be displayed in the form of precise measurements not available from a pulse monitor or even the sophisticated STPM. The
CRO, although a convenient adjunct which may well be used to provide an auxiliary display of curve shapes, does not provide absolute measurements as does the pulse curve analyser, either in digital or analogue form as desired.
Thus, summarising, the pulse curve analyser is designed to extract information from a voltage waveform coming from a transducer, which may be optical, on the surface of skin or mucous membrane. In the case of activity of capillary blood circulation, information as to the phase of capillary blood loading and deoxygenation (reductive phase) appears in this voltage waveform. This waveform has a base frequency equivalent to the pulse, i.e. heart, rate of the patient.
Claims (5)
1. A pulse curve analyser comprising, in combination light-responsive transducer means for sensing a patient's continuous physiological
circulatory activity to produce a voltage waveform
which is an analogue of said patient's body tissue
pulsatile blood colour and/or density changes,
means for processing said waveform to produce
an output signal proportional to the time rate of
change of the amplitude of said waveform, and
means for displaying quantitatively and
instantaneously the rise time and/or the fall time
representative of a transient cycle of said waveform as a function of the period of said cycle.
2. A pulse curve analyser as claimed in Claim
1, wherein said transducer means responds to
light modulated by changes in capillary blood
circulation activity.
3. A pulse curve analyser as claimed in Claim
1, wherein said means for processing includes a
circuit wherein the output of said transducer
means is fed to a notch filter, the output of which
is fed to an operational amplifier whose output is buffered and then passed to a differentiator which in turn feeds a low pass filter having linear phase, the latter being offset whereby its output voltage is negative when said voltage waveform is rising, and positive when said voltage waveform is falling, and has a magnitude which is proportional to both the amplitude of said voltage waveform and its time rate of change.
4. A pulse curve analyser as claimed in Claim 3, wherein the voltage output of said low pass filter is squared by a Schmitt trigger and then passed to twin detectors the respective outputs of which are proportional to the fractional rise time and fractional fall time of said voltage waveform with reference to a pulse cycle thereof, said lastmentioned outputs being applied by a multiplexer to chosen sets of inputs of a ratiometric voltmeter integrated circuit whereby the values of said times are displayed.
5. A pulse curve analyser substantially as described herein with reference to the accompanying drawings.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB08135517A GB2110363A (en) | 1981-11-25 | 1981-11-25 | Pulse curve analyser |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB08135517A GB2110363A (en) | 1981-11-25 | 1981-11-25 | Pulse curve analyser |
Publications (1)
Publication Number | Publication Date |
---|---|
GB2110363A true GB2110363A (en) | 1983-06-15 |
Family
ID=10526134
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB08135517A Withdrawn GB2110363A (en) | 1981-11-25 | 1981-11-25 | Pulse curve analyser |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB2110363A (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0226631A1 (en) * | 1985-05-31 | 1987-07-01 | Coulter Electronics | Method and apparatus for editing particle produced electrical pulses. |
EP0270798A1 (en) * | 1986-11-07 | 1988-06-15 | Siemens Aktiengesellschaft | Apparatus for selective signal counting |
EP0480726A2 (en) * | 1990-10-12 | 1992-04-15 | Westinghouse Electric Corporation | Pulse analysis system and method |
GB2356251A (en) * | 1999-11-12 | 2001-05-16 | Micro Medical Ltd | Determining the stiffness of arteries in a person |
-
1981
- 1981-11-25 GB GB08135517A patent/GB2110363A/en not_active Withdrawn
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0226631A1 (en) * | 1985-05-31 | 1987-07-01 | Coulter Electronics | Method and apparatus for editing particle produced electrical pulses. |
EP0226631A4 (en) * | 1985-05-31 | 1990-03-27 | Coulter Electronics | Method and apparatus for editing particle produced electrical pulses. |
EP0270798A1 (en) * | 1986-11-07 | 1988-06-15 | Siemens Aktiengesellschaft | Apparatus for selective signal counting |
EP0480726A2 (en) * | 1990-10-12 | 1992-04-15 | Westinghouse Electric Corporation | Pulse analysis system and method |
EP0480726A3 (en) * | 1990-10-12 | 1992-08-26 | Westinghouse Electric Corporation | Pulse analysis system and method |
GB2356251A (en) * | 1999-11-12 | 2001-05-16 | Micro Medical Ltd | Determining the stiffness of arteries in a person |
GB2356251B (en) * | 1999-11-12 | 2003-09-24 | Micro Medical Ltd | Apparatus for determining the stiffness of arteries in a person |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |