United States Patent
`Herczfeld et al.
`
`us)
`
`(45)
`
`3,704,706
`
`Dec. 5, 1972
`
`[54] HEART RATE AND RESPIRATORY
`1/1966
`3,228,391
`Fitter et al. ......................128/2.05 T
`
`
`1/1966
`3,230,951
`. 128/2.05 P
`MONITOR
`Teschner....
`
`3,511,227=S/1970 JONSON ....4.-eerseeeeeeeeeereees 128/2.05 F
`{72]
`Inventors: Bonita Falkner Herezfeld; Peter R.
`Herezfeld, both of Philadelphia, Pa.;
`Richard D. Klafter, Willingboro,
`N.J.
`
`987,504
`
`3/1965 Great Britain ........scsee 128/2.05 P
`
`FOREIGN PATENTS OR APPLICATIONS
`
`{73] Assignee: Drexel University, Philadelphia, Pa.
`{22] Filed:
`Oct. 23, 1969
`
`(21] Appl. No.: 868,823
`
`Primary Examiner—Richard A. Gaudet
`Assistant Examiner—Kyle L. Howell
`Attorney—Paul and Paul
`
`[57]
`
`ABSTRACT
`
`Apparatus for detection of pulse repetition rate and
`oxygenation of blood flow, comprising a solid state
`probe having a narrow bandwidth light source housed
`to direct light upon a patient’s finger and a photode-
`tector housed for receiving reflected light from such
`finger, the output of the detector being connected to
`electronic circuitry for detecting pulse repetition rate
`of blood flow and for detecting signal level representa-
`tive of the degree of oxygenation of the patient’s
`6/1953 Liston... eee eeeseeeeeeeeeeee | 28/2 R
`2,640,389
`blood. The use of a low power narrow bandwidthlight
`9/1963
`Smith.........
`-128/2.05 P
`3,103,214
`source with a red emission characteristic permits
`
`3,123,066 3/1964—Brumley.......--.:.ccccccercerreereees 128/2R
`precise detection of the degree of oxygenation of the
`3,139,086
`6/1964
` Botschet al.
`128/2.05 P
`blood.
`3,152,587
`10/1964
`Ullrich et al....csscseessserees 128/2R
`3,167,658
`1/1965
`Richter ......-....sccceeeceeeee 128/2.05 P
`
`(52) WSC loccsscsccs: 128/2 R, 128/2.05 T, 128/2.05 P,
`356/41
`Tents Ch ccsesissscesosesnssnasseissonsateasssceacseens A61b 5/02
`(STD,
`{58} Field of Search ....128/2, 2.05 T, 2.05 V, 2.05 P,
`128/2.05 F; 356/39-42
`
`[56]
`
`References Cited
`
`UNITED STATES PATENTS
`
`
`
`2. Claims,4 DrawingFigures
`
`40
`
`
`PATIENT
`
`I
`
`BUFFER
`AMPLIFIER
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`30
`
`SCHMITT
`TRIGGER
`
`0001
`0001
`
`Apple Inc.
`AppleInc.
`APL1018
`APL1018
`U.S. Patent No. 8,923,941
`U.S. Patent No. 8,923,941
`
`FITBIT, Ex. 1018
`
`FITBIT, Ex. 1018
`
`

`

`PATENTED DEC 5 1972
`
`3,704,706
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`Ret
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`
`
`iSSS
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`SHEET 1 OF 2
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`TO AMPLIFIER &
`POWER SUPPLY
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`
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`|ZLAEXSSSSssss
`
`
`
`
`yTIS
`
`
`
`DEVICE
`
`MONITORING
`
`Fig. 3
`
`0002
`0002
`
`INVENTORS.
`BONITA FALKNER HERCZFELD
`PETER R. HERCZFELD
`RICHARD 0. KLAFTER
`
`BY We Lyboauk_
`
`' ATTORNEYS.
`
`FITBIT, Ex. 1018
`
`FITBIT, Ex. 1018
`
`

`

`PATENTED GEC 5 1972
`
`3,704,706
`
`SHEET 2 OF 2
`
`
`
`
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`Fig. 4(a)
`NORMAL PROBE
`OUTPUT VOLTAGE
`
`Fig. 4(b)
`RESPIRATORY
`DISTRESS
`
`Fig . 4(c)
`SCHMITT
`TRIGGER
`
`Fig. 4(d)
`MULTIVIBRATOR
`
`INVENTORS.
`BONITA FALKNER HERCZFELD
`PETER R. HERCZFELD
`RICHARD D. KLAFTER
`
`BY Falrtewt.
`
`ATTORNEYS.
`
`0003
`0003
`
`FITBIT, Ex. 1018
`
`FITBIT, Ex. 1018
`
`

`

`1
`HEART RATE AND RESPIRATORY MONITOR
`
`BACKGROUND OF THE INVENTION
`
`A.Field of the Invention
`This invention lies in the field of heart rate monitors
`and, more particularly, solid state monitors for detec-
`tion of peripheral flow and oxygenation of blood in a
`newborninfantpatient.
`B. Description of the Prior Art
`The problem of accurately monitoring the heartbeat
`and of obtaining information regarding the flow of ox-
`ygenated blood in a newborn infant has long resisted
`the development of an economical
`instrument. The
`severity of the problem ts based on the medical con-
`sideration that an infant, and particularly a premature
`infant, when undergoing an exchange blood transfu-
`sion, sometimes suffers cardiac arrest which, if unde-
`tected for a relatively short period of time, may cause
`permanent brain damageor death. Further, physicians
`are vitally interested in obtaining information relating
`to respiratory arrest and the degree of oxygenation of
`the blood being circulated throughout the body during
`and after an exchangetransfusion.It is of particular im-
`portance to have information which discloses a partial
`cardiac arrest or a partial respiratory arrest, so that the
`physician can take swift action to alleviate and correct
`the situation. There is thus a requirement for continu-
`ous monitoring of both pulse repetition rate, a change
`in which often precedes cardiac arrest, and the level of
`oxygen in the blood, whichis an indication of respirato-
`ry distress.
`The prior art shows a number of heart monitoring
`devices. However, most of these devices are designed
`for clinical use on adults and are generally not suitable
`for use with newborn infants, Particularly, devices
`utilizing electrodes generally require that the elec-
`trodes be of a sufficient size to pick up the extremely
`small biopotential signals which are monitored, such
`large electrode sizes being unworkable for newborn in-
`fants. Furthermore,
`commercially available heart
`monitoring devices are extremely expensive, and pro-
`vide no information about the flow of oxygenated
`blood.
`Apparatus for the measurementof peripheral pulsa-
`tions has a numberofdistinct advantages over the elec-
`trocardiogram and other similar devices. First, it
`is
`known that it is possible for electrical activity of the
`heart to persist after the heart has actually stopped
`beating. Thus, a monitor designed to detect biopoten-
`tials could be late in detecting any cardiac arrest.
`Further,it is extremely difficult to place electrodes on
`infants in such a way as to avoid extraneous noise pick-
`up. And, perhaps most importantly, a monitor that only
`senses biopotentials cannot detect respiratory distress.
`Digital monitors, or
`transducers,
`for detecting
`peripheral pulsations, and utilizing a light source in
`combination with a detector, have been shown in the
`art. More particularly, the prior art discloses a digital
`transducer comprising a light source in combination
`with a photoelectric cell, with a red filter placed over
`the photoelectric cell. Since the photocell is responsive
`to light in the red region of the spectrum, arterial pulsa-
`tions which drive blood into the digit result in an in-
`creased redness and increased photocell response, thus
`giving an indication of the pulse repetition rate. How-
`ever, a bulb and filter combination is inefficient, most
`
`3,704,706
`
`3
`
`2
`of the radiated energy being outside of the red. Only by
`inclusion of a prohibitively expensive optical filter
`could sucha light andfilter combination producea nar-
`row band width on the orderof that provided bya laser.
`In addition to being more cumbersome,
`the device
`necessarily has a heating problem, which makesit par-
`ticularly undesirable for use with infants. Further, the
`device detects only volume of blood flow, and cannot
`distinguish between blood volume and degree of ox-
`ygenation.
`
`SUMMARYOF THE INVENTION
`
`The primary object of this invention is to provide ap-
`Paratus for the detection of oxygenated blood flow
`whichis simple, efficient, lightweight, inexpensive and
`effective for the purpose and which overcomesthedis-
`advantagesof the priorart.
`It is a further object of this invention to provide a
`heart rate monitor comprising a solid state optical
`probe which is suitable for use on premature infants,
`and which senses peripheral pulsations ofthe heart.
`It is a further object of this invention to provide ap-
`paratus which monitors both heart pulse rate and ox-
`ygenation of blood flow.
`Accordingly, this invention provides apparatus com-
`prising a solid state laser as a source of light in com-
`bination with a solid state photodetector, forming an
`optical probe suitable for sensing peripheral pulsations
`of the heart. Thesolid state laser is a very small and ex-
`tremély efficient light source emitting microwatts of
`power in a narrow band width having peak emission oc-
`curring in the red range of the optical spectrum. The
`laser directs a low energy beam oflight at the capilla-
`Ties of a finger, the blood flowing within reflecting in-
`cident red light which is detected by a photodetector
`housed adjacent to the laser and having a response
`curve suitable for detection throughout the emission
`spectrum of the laser. The electrical output of the
`probe is transmitted to processing apparatus having
`pulse detection circuitry to determine the pulse repeti-
`tion rate, as well as DC level detection circuitry to
`determine the relative oxygen content of the blood.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`30
`
`40
`
`FIG. 1 shows a schematic diagram of the probe hous-
`ing and its elements in relation to a patient’s finger.
`FIG. 2 shows a schematic diagram of an alternate
`construction of the probe housing.
`FIG. 3 shows
`a block diagram of electronic
`processingcircuitry which is connected to the probe.
`FIG. 4 shows a representation of waveforms
`5 produced by the probe and electronic processing cir-
`cuitry.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`Referring now to the drawings, FIG. 1 shows a sche-
`matic diagram of the probe andits elements. The probe
`20 is placed on the patient’s finger by conventional
`strapping or tape and aligned such that the light source
`21 directs incident light, indicated by arrows marked
`“I,” at the patient’s finger. The detector 22 is placed
`adjacentto light source 21 anddisposed in orderto col-
`lect reflected light, indicated by arrows marked “R,”
`
`2211
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`0004
`0004
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`FITBIT, Ex. 1018
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`FITBIT, Ex. 1018
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`3,704,706
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`3
`from the patient’s finger. The light source 21 and
`photodetector 22, combined with housing 23, form the
`probe 20, which has typical overall dimensions of 4
`inch X 4 inch X % inch. Thelight source 21 is suitably
`a gallium arsenide solid state laser whichitself is one-
`tenth inch in diameter and 0.15 inch in length, having
`typically 25 microwatts of power being emitted in a
`narrow band width with the peak emission occurring at
`6,700 angstrom, i.e., in the red range of the color spec-
`trum. Such a typical gallium arsenide laser is commer-
`cially available. See, for instance, Monsanto model
`MVIOA. The photodetector 22is required to have high
`sensitivity through the frequencies of the emission
`spectrum of the laser. A suitable photodetector is the
`Motorola MRD210 50 volt NPNsilicon photodetector.
`This detector is approximately 0.06 inch in diameter
`and a maximum of 0.118 inch in height, which dimen-
`sions permit incorporation into the % inch x % inch X
`% inch probe device. A photodetector having frequen-
`cy selectivity matching the laser characteristics would
`further increase theselectivity of the probe.
`The probe housing 23 may be fabricated from a
`piece of metal, suitably brass, having parallel recesses
`or holes 25 drilled within it to accommodate the laser
`and photodetector
`respectively,
`the holes being
`oriented perpendicular to the probe’s surface whichis
`placed against the finger. Between recesses 25is an in-
`sulating member 26 which optically isolates
`the
`recesses,
`thereby optically isolating the laser and
`photodetector. Alternately, the probe housing may be
`made from an epitaxial plastic, as shown in FIG, 2. A
`front portion 27 of a clear nonhardening plastic may be
`added, thereby encapsulating the laser and photodetec-
`tor without significantly impeding light transmission. A
`power supply 39 provides power for the laser and the
`photodetector, as well
`as
`the electronic circuitry
`described hereinbelow.
`in operation, the probe is placed uponthe patient’s
`finger such that blood which is flowing in the capillaries
`of the fingerreflects incident red light. The intensity of
`the reflected light is proportional both to the amountof
`blood flowing in the finger and to the freshness of the
`blood, i.e., the degree to which it is oxygenated. For
`each heartbeat, fresh blood is pumpedinto the capilla-
`ries, thereby causing a periodic increase and decrease
`in the reflected light intensity. Under normal condi-
`tions then, a periodic waveform such as shownin FIG.
`4a will be detected, which waveform represents both
`volume and color of
`the circulating blood. The
`waveform has an AC component corresponding to the
`heart pulsations, and a DC component which will be
`directly proportional to the redness, or oxygenation, of
`the blood. In the event ofpartial cardiac arrest, the pul-
`sations vary in frequency, which condition can be easily
`detected. When a respiratory distress occurs, the heart
`continues to pump blood, but it is relatively unox-
`ygenated blood with a characteristic bluish hue. Since
`the probeis relatively insensitive in the blue region of
`the light spectrum, such a respiratory distress is im-
`mediately manifested by a probe signal of diminished
`amplitude, as shown in FIG. 4b. By contrast, in the par-
`tial cardiac arrest condition, the pulse repetition rate
`will change, while the amplitude and DC level will
`remain essentially the same. To distinguish the respira-
`tory distress condition from the partial cardiac arrest
`
`20
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`condition, the DC component of the signal, or the
`peak-to-peak value, is monitored. Thus, by distinguish-
`ing pulse repetition rate and DC level, the two cases
`can be separately diagnosed.
`Referring now to FIG. 3, a block diagram of the heart
`rate and respiratory monitor is shown. The signal
`developedby the probe 20, as shownin FIG. 4a, is cou-
`pled into electronic circuitry 40 for
`information
`processing. The signal is first fed through a conven-
`tional solid state DC amplifier 25 which amplifies the
`total signal. The output of amplifier 25 is parallel cou-
`pled to a conventional Schmitt Trigger circuit 26 and to
`a detector 29. The Schmitt Trigger 26 is a bistable elec-
`tronic device which, when driven by the pulsating
`signal, will switch between two stable states,
`thus
`producing a squarewave output as shown in FIG. 4c.
`Such squarewave may suitably be differentiated and
`applied to a conventional mono-stable multivibrator
`27, which multivibrator will produce a pulse train out-
`put having suitable pulse widths, and having a pulse
`repetition rate equal to that of the probe waveform.
`Such a mono-stable output is shown in FIG. 4d. This
`output, then, can be coupled to a conventional driver
`circuit 31, such as an emitter follower, which in turn
`drives a suitable monitoring device 28, such as a beep
`tone generatoror oscillograph.
`Still referring to FIG, 3, the output of amplifier 25 is
`also fed into a detector 29, suitably a conventional! DC
`detector. The output of detector 29 is coupled,
`preferably through a buffer amplifier 30, to a suitable
`volt meter 32 which would indicate the magnitude of
`the detected DC voltage. The volt meter 32 can be
`suitably equipped with a reference needle, which nee-
`dle can be set at a lowerlimit, such that when the DC
`level drops to such lowerlimit, the meter would sound
`an alarm signal, notifying a physician. By checking the
`pulse rate output, the physician could immediately
`determine whether the drop in DC level was due to a
`respiratory or cardiac cause.
`It
`is to be understood that detector 29 could, al-
`ternately, be a peak-to-peak detector of conventional
`circuitry, and be connected to a peak-to-peak volt
`meter which would indicate the magnitude of the de-
`tected voltage pulses in the signal from probe 20.
`Either the DC level or the peak-to- peak information,
`when compared with the pulse repetition rate, would
`be sufficient
`to enable the physician to distinguish
`between cardiacarrest and respiratory distress.
`From the foregoing,it is seen that this invention pro-
`vides an extremely efficient and suitably smal] device
`for monitoring blood flow characteristics of an infant.
`The choice of a laser which produces approximately 25
`microwatts makes possible a very cool and efficient
`device. Further, by using a narrow beam laser, it is
`possible to produce a device which is very sensitive to
`changesin blood color. By contrast, apparatus utilizing
`white light in combination with a red filter, in addition
`to being inefficient and generating heat which would be
`prohibitive in clinical uses with infants, producesa rela-
`tively broad range ofred light. Consequently, relatively
`large changes in oxygen content musttake place before
`detection by a white light and filter combination,
`whereas extremely small changes can be detected with
`the frequencyselective laser probe of this invention.
`
`2212
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`FITBIT, Ex. 1018
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`FITBIT, Ex. 1018
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`

`

`3,704,706
`
`b.
`
`5
`It is to be noted that equivalent narrow beam light
`sources including light-emitting diodes, whether the
`light is coherent or not may be utilized in place oflasers
`in the practice ofthis invention.It is further noted that
`while specific electronic circuitry for processing the
`probe signal has been discussed in this specification, a
`wide variety of pulse repetition rate and level detection
`circuits can be used.
`Weclaim:
`1, Heart rate and respiratory monitor apparatus for
`detecting pulse repetition rate and oxygenation of
`blood flow in a patient, comprising:
`a. a probe housing having first and secondlight trans-
`mitting faces;
`a low power solid state laser red light source, hav-
`ing narrow bandwidth emission characteristics,
`positioned in said probe housing to emit red light
`throughsaid first face;
`:
`. semiconductor photodetector means for detecting
`red light reflected thereon, said photodetector
`means positioned in said housing to receive light
`throughsaid secondface of said housing, such that
`when said faces of said probe housing are posi-
`tioned contiguous to a periphery of a patient, in-
`cident light from said red light sourceis reflected
`from such periphery and received by said photode-
`tector means;
`d. electronic processing means connected to said
`photodetector means having pulse repetition rate
`circuitry and first output means coupled thereto
`for monitoring said patient’s pulse repetition rate,
`and signal level detection circuitry and second out-
`
`6
`put means coupled thereto for monitoring the
`degree of oxygenationof said patient’s blood; and
`@, a power source connected to and supplying energy
`to said red light source, said photodetector means,
`and said electronic processing means.
`2. Heart rate and respiratory apparatus for detecting
`the pulse repetition rate and degree of oxygenation of
`blood flowing in a peripheral portion of a patient, com-
`prising:
`a. narrow bandwidth red lightmeansfor transmitting
`incidentred light upon said peripheral portion and
`detecting red light reflected therefrom;
`b. a probe housing means for housing said red light
`means such that, when positioned contiguous to
`said periphery, some of said incident
`light
`is
`reflected from the blood flowing in said periphery
`andreceived bysaid reflecting means; and
`c. electronic processing means connected to said de-
`tecting means for transforming said reflected red
`light
`into an electrical signal representing said
`reflected red light, and including pulse repetition
`rate circuitry for monitoring said patient's pulse
`repetition rate, and signal level detection circuitry
`for monitoring the degree of oxygenation of said
`patient’s blood, said red light means including a
`narrow bandwidth solid state laser mounted within
`said probe housing means to direct incident red
`light
`to said periphery, and a semiconductor
`photodetector mounted in said probe housing
`means to receive red light reflected from said
`periphery. * ae *
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`5
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`0006
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`106009
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`0187
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`FITBIT, Ex. 1018
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`FITBIT, Ex. 1018
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