`(10) Patent No.:
`US 6,771,994 B2
`
`Kiani et al.
`(45) Date of Patent:
`Aug. 3, 2004
`
`U5006771994B2
`
`(54) PULSE OXIMETER PROBE-OFF
`DETECTION SYSTEM
`
`(75)
`
`Inventors: Massi E. Kiani, Laguna Niguel, CA
`.
`-
`-
`-
`Sis.) Egghéllfigd K' D1ab,M1ss1on
`“940’
`
`5,635,700 A *
`5,758,644 A
`5,761,540 A *
`gagggaggg 2
`,
`,
`5,923,021 A *
`6,035,223 A *
`
`6/1997 Fazekas ................. 235/462.06
`6/1998 Diab et al.
`6/1998 White ........................... 396/4
`13133: Slag 6: ai~
`1a
`e a .
`............. 235/455
`7/1999 Dvorkis et al.
`3/2000 Baker, Jr.
`................... 600/323
`
`(73) Assignee: Masimo Corporation, Irvine, CA (US)
`
`FOREIGN PATENT DOCUMENTS
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U S C 154(1)) by 0 days
`'
`'
`'
`'
`
`DE
`EP
`EP
`GB
`
`197 28 902 A1
`0182 197 A2
`0315 040 A1
`2061 496 A
`
`11/1999
`5/1986
`10/1989
`5/1981
`
`(21) Appl. No.2 10/374,303
`
`* cited by examiner
`
`(22)
`
`(65)
`
`Filed:
`
`Feb. 24, 2003
`_
`_
`_
`Pr10r Publlcatlon Data
`US 2003/0139656 A1 Jul. 24, 2003
`
`Related US. Application Data
`.
`.
`.
`.
`.
`21365651011 OfPanixlIcansogzggb89/591081, filed 011 Jun- 16:
`, now a .
`0.
`,
`,
`.
`Provisional application No. 60/140,000, filed on Jun. 18,
`1999.
`
`(62)
`(60)
`
`7
`
`(51)
`Int. Cl.
`.................................................. A61B 5/00
`
`(52)
`..... 600/323; 600/344
`(58) Field of Search ................................. 600/309—310,
`600/322—324, 316, 344, 473, 476
`
`(56)
`
`References CitEd
`U.S. PATENT DOCUMENTS
`
`4,295,475 A
`4,331,161 A
`4,561,440 A
`4,603,700 A
`4,945,239 A *
`5,226,417 A
`5,370,114 A
`5,469,845 A
`5,503,148 A
`
`10/1981 Torzala
`5/1982 Patel
`12/1985 Kubo et al.
`8/1986 Nichols et al.
`7/1990 Wist et al.
`.................. 600/473
`7/1993 Swedlow et al.
`12/1994 Wong et al.
`11/1995 DeLonzor et al.
`4/1996 Pologe et al.
`
`202
`
`\
`
`220
`
`Primary Examiner—Mary Beth Jones
`Assistant Examiner—Matthew Kremer
`(74) Attorney, Agent, or Firm—Knobbe, Martens, Olson, &
`Bean LLP
`57
`
`ABSTRACT
`
`)
`(
`The present invention provides a number of improvements
`that can be incorporated into a pulse oximeter probe to detect
`.
`.
`When a probe has become (.hSIOdged from a patlent and/or to
`prevent a probe-off cond1tlon. A probe-off cond1tion occurs
`When the optical probe becomes partially or completely
`dislodged from the patient, but continues to detect an AC
`signal Within the operating region of the pulse oximeter. In
`one aspect, the present invention provides electrical contacts
`that contact the skin of a patient When the probe is properly
`attached. In another aspect, the present invention provides a
`number of louvers placed in front of the sensor’s photode-
`tector to filter out oblique light rays that do not originate
`from a point in front of the detector. Accordingly, if the
`emitter and photodetector are not properly aligned,
`the
`photodetector Will not produce a signal Within the valid
`operating range of the pulse oximeter. In accordance with a
`method of the present invention the pulse oximeter can
`sound an alarm or display a warning if it determines that the
`probe is not properly attached to the patient.
`
`18 Claims, 15 Drawing Sheets
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`APPLE 1001
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`APPLE 1001
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`Aug. 3, 2004
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`Sheet 1 0f 15
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`PULSE OXIMETER
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`CONNECTOR
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`1710.1
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`PULSE OXIMETER
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`PROBE
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`OFF
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`DETECTOR
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`FIG.3B
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`PULSE OXIMETER
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`CONNECTOR
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`PROBE
`OFF
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`DETECTOR
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`732
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`202
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`FIG.3C
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`PULSE OXIMETER
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`CONNECTOR
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`PROBE
`OFF
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`DETECTOR»
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`Sheet 7 0f 15
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`PROBE
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`OFF
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`DETECTOR
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`PULSE OXIMETER
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`FIG. 3E
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`FIG.3F
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`Sheet 9 0f 15
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`PROBE
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`OFF
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`DETECTOR
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`PULSE OXIMETER
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`FIG.3G
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`FIG.3H
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`FIG.5C
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`603
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`604
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`CHECK CONTINUITY
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`BETWEEN SKIN
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`CONTACTS
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`CHECK FOR VALID
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`AC SIGNAL FROM
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`PHOTO DETECTOR
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`VALID SIGNAL
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`IG. 6
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`US 6,771,994 B2
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`1
`PULSE OXIMETER PROBE-OFF
`DETECTION SYSTEM
`
`REFERENCE TO RELATED APPLICATIONS
`
`The present application claims priority benefit under 35
`U.S.C. § 120 to, and is a divisional of, US. patent applica-
`tion Ser. No. 09/595,081, filed Jun. 16, 2000, now US. Pat.
`No. 6,526,300, entitled “Pulse Oximeter Probe-Off Detec-
`tion System,” which claims priority benefit under 35 U.S.C.
`§ 119(e) from US. Provisional Application No. 60/140,000,
`filed Jun. 18, 1999, entitled “Pulse Oximeter Probe-Off
`Detection System.” The present application also incorpo-
`rates the foregoing utility disclosure herein by reference.
`
`BACKGROUND OF THE INVENTION
`
`The present invention relates to optical probes that can be
`attached to the finger, toe, or appendage of a patient. More
`particularly,
`the present invention relates to devices and
`methods for identifying when a probe has become dislodged
`from a patient.
`
`DESCRIPTION OF THE RELATED ART
`
`Oximetry is the measurement of the oxygen status of
`blood. Early detection of low blood oxygen is critical in the
`medical field, for example in critical care and surgical
`applications, because an insufficient oxygen supply can
`result in brain damage and death in a matter of minutes.
`Pulse oximetry is a widely accepted noninvasive procedure
`for measuring the oxygen saturation level of arterial blood,
`an indicator of oxygen supply. A pulse oximetry system
`generally consists of a probe attached to a patient, a monitor,
`and a cable connecting the probe and monitor.
`Conventionally, a pulse oximetry probe has both red and
`infrared (IR) light-emitting diode (LED) emitters and a
`photodiode detector. The probe is typically attached to a
`patient’s finger or toe, or a very young patient’s foot. For a
`finger, the probe is configured so that the emitters project
`light through the fingernail, the arteries, vessels, capillaries,
`tissue and bone. The photodiode is positioned opposite the
`LED so as to detect the LED transmitted light as it emerges
`from the finger tissues.
`The pulse oximetry monitor (pulse oximeter) determines
`oxygen saturation by analyzing the differential absorption by
`arterial blood of the two wavelengths emitted by the probe.
`The pulse oximeter alternately activates the probe LED
`emitters and reads the resulting current generated by the
`photodiode detector. This current
`is proportional
`to the
`intensity of the detected light. The pulse oximeter calculates
`a ratio of detected red and infrared intensities, and an arterial
`oxygen saturation value is empirically determined based on
`the ratio obtained. The pulse oximeter contains circuitry for
`controlling the probe, processing the probe signals and
`displaying the patient’s oxygen saturation and pulse rate. A
`pulse oximeter is described in US. Pat. No. 5,632,272
`assigned to the assignee of the present invention.
`
`SUMMARY OF THE INVENTION
`
`The present invention provides a number of improve-
`ments that can be incorporated into a pulse oximeter probe
`to detect when a probe has become dislodged from a patient
`and/or to prevent a probe-off condition. A probe-off condi-
`tion occurs when the optical probe becomes partially or
`completely dislodged from the patient, but may continue to
`detect an AC signal within the operating region of the pulse
`oximeter.
`
`5
`
`10
`
`15
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`20
`
`2
`In one aspect, the present invention provides a number of
`electrical contacts that contact the skin of a patient when the
`probe is properly attached. The pulse oximeter can check the
`continuity through the contacts to determine whether the
`probe is properly attached. If the probe is not properly
`attached, the pulse oximeter can identify a probe-off condi-
`tion even though the oximeter measures an AC signal that
`appears like the probe is still attached.
`In another aspect, the present invention provides a num-
`ber of louvers placed in front of the probe’s photodetector to
`filter out oblique light rays that do not originate from a point
`in front of the detector. If the probe becomes dislodged, the
`emitter will not likely remain in front of the photodetector.
`If the emitter and photodetector are not properly aligned, the
`photodetector will not produce a signal within the valid
`operating range of the pulse oximeter. The louvers prevent
`light from an oblique angle from reaching the photodetector
`and creating a false signal that might be interpreted by the
`pulse oximeter as a physiological signal. Accordingly, the
`pulse oximeter can determine that a probe has become
`dislodged when the photodetector does not produce a valid
`signal. Furthermore, probe-off conditions can avoided since
`oblique light rays are not able to reach the photodetector to
`produce an apparently valid signal.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`Referring now to the drawings in which like reference
`numbers represent corresponding components throughout:
`FIG. 1 illustrates a schematic of one embodiment of a
`
`30
`
`pulse oximeter system;
`FIGS. 2A—B depict an optical probe and the attachment of
`the optical probe on the fingertip of an adult patient;
`FIG. 3A illustrates a schematic of a pulse oximeter system
`that incorporates electrical contacts to the skin of a patient,
`in accordance with one embodimet of the present invention;
`FIG. 3B illustrates a perspective view of an optical probe
`incorporating electrical contacts to the skin of a patient;
`FIG. 3C illustrates a schematic of one embodiment of a
`
`pulse oximeter system that incorporates electrical contacts to
`the skin of a patient;
`FIG. 3D illustrates a schematic of a preferred embodiment
`of a pulse oximeter system that incorporates a number of
`electrical contacts to the skin of a patient;
`FIG. 3E depicts a generalized schematic of a pulse
`oximeter that incorporates another embodiment of a contact
`on a pulse oximeter probe;
`FIG. 3F depicts a perspective view an optical probe
`incorporating the embodiment of FIG. 3E;
`FIG. 3G depicts a generalized schematic of a pulse
`oximeter system that incorporates another embodiment of a
`contact sensor in accordance with the present invention;
`FIG. 3H depicts a perspective view of an optical probe
`incorporating the contact sensor of FIG. 3G;
`FIG. 4 illustrates a probe that has become unfastened;
`FIG. 5A illustrates a probe wherein a number of louvers
`are placed in front of the detector assembly;
`FIG. 5B illustrates a properly attached probe wherein a
`number of louvers are placed in front of the detector
`assembly;
`FIG. 5C illustrates a top plan view of a preferred embodi-
`ment of a probe wherein a number of louvers are placed in
`front of the detector assembly
`FIG. 6 illustrates a flow chart of the method of detecting
`a dislodged probe.
`
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`US 6,771,994 B2
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`3
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`To compute peripheral arterial oxygen saturation, denoted
`SpaOz, pulse oximetry relies on the differential light absorp-
`tion of oxygenated hemoglobin, HbOz, and deoxygenated
`hemoglobin, Hb. This differential absorption is measured at
`the red and infrared wavelengths of the probe. In addition,
`pulse oximetry relies on the pulsatile nature of arterial blood
`to differentiate hemoglobin absorption from absorption of
`other constituents in the surrounding tissues. Light absorp-
`tion between systole and diastole varies due to the blood
`volume change from the inflow and outflow of arterial blood
`at a peripheral tissue site. The tissue site might also comprise
`skin, muscle, bone, venous blood, fat, pigment, etc., each of
`which absorbs light. Blood oxygen saturation measurements
`are based upon a ratio of the time-varying or AC portion of
`the detected red and infrared signals with respect to the
`time-invariant or DC portion. This AC/DC ratio normalizes
`the signals and accounts for variations in light pathlengths
`through the measured tissue.
`As reproduced in FIG. 1, a schematic of one embodiment
`of a pulse oximeter system 100 is disclosed in US. Pat. No.
`5,758,644 (the ’644 patent), assigned to the assignee of the
`present application and incorporated herein by reference.
`The system 100 comprises a pulse oximeter 140, which is
`attached through a connector 142 to a probe 110. The probe
`110 comprises a first LED 112, a second LED 114 and a
`photodetector 116. The first and second LEDs 112 and 114
`are connected back-to-back and share a common electrical
`
`connection 118. The photodetector 116 has its own electrical
`connection 122. Each of the LEDs 112 and 114 and the
`
`photodetector 116 are connected at their outputs to a com-
`mon ground electrical connection 130. The two LEDs 112
`and 114 are preferably configured to produce different
`wavelengths of light, which pass through the flesh of a
`patient to be detected by the photodetector 116. The oxime-
`ter 140 can select the LED to be driven by applying either
`a positive or negative voltage to the connection 118. A
`coding resistor 132 has a resistance that can measured by the
`pulse oximeter 140 to determine the particular characteris-
`tics of the probe 110. The coding resistor 132 is coupled in
`parallel with the first LED 112 or the second LED 114. The
`resistor 132 can be used to indicate the operating wavelength
`of the first and second LEDs 112 and 114, or to indicate the
`type of probe. In order to read the coding resistor 132, the
`pulse oximeter 140 drives the first LED 112/coding resistor
`132 combination at a level that is low enough that the LED
`draws insignificant current. At this level, significantly all of
`the current flows through the coding resistor 132 and the
`pulse oximeter 140 can determine the value of the resistor in
`accordance with Ohm’s law. By configuring the coding
`resistor 132 in parallel with one of the LEDs 112, 114, the
`added expense of an additional lead connecting the pulse
`oximeter 140 to the probe 110 can be saved.
`One embodiment of a disposable probe for use with pulse
`oximetry systems is disclosed in US. Pat. No. 5,782,757,
`assigned to the assignee of the present application and
`incorporated herein by reference. FIGS. 2A—B depict the
`optical probe 202 and the attachment of the optical probe
`202 on the fingertip 250 of an adult patient. The disposable
`optical probe 202 is designed to fit comfortably onto a
`patient’s fingertip. As illustrated in FIG. 2A, the probe 202
`includes a central portion 204, a pair of adhesive flanges 205
`extending from the central portion 204, a connector portion
`210 situated between the flanges 205, and a pair of smaller
`adhesive flaps 215 extending from the central portion 204 on
`
`4
`the end of the optical probe 202 opposite from a connector
`tab 210. The probe 202 further includes an emitter aperture
`220 with a number of emitters (e.g., a light-emitting diodes)
`positioned within the central portion 204 close to the con-
`nector portion 210, and a detector aperture 230 which allows
`light to pass through the detector aperture 230 to a detector
`assembly 235. An adult fingertip 250 is shown in phantom
`in FIG. 2A to illustrate the position at which the fingertip 250
`is placed when the probe 202 is to be fastened onto the
`fingertip 250 for use. Although not depicted specifically in
`FIGS. 2A—2B, the probe 202 is typically fabricated from
`multiple layers.
`FIG. 2B illustrates the probe 202 fastened onto the
`fingertip 250. As shown in FIG. 2B, the probe 202 folds to
`conform to the very end of the fingertip. The adhesive flaps
`205 fold downward (in the illustration of FIG. 2B) to wrap
`around the fingertip 250 while the adhesive flaps 215 fold
`upward (in the illustration of FIG. 2B) about a portion of the
`circumference of the fingertip 250 to provide support. As
`shown in FIG. 2B, when the probe 202 is folded about the
`fingertip 250,
`the emitters located within the probe are
`spaced opposite the detector assembly 235 such that light
`from the emitters passes through the emitter aperture 220,
`through the finger 250 and is incident upon the detector
`assembly 235 through the detector aperture 230.
`FIG. 2B depicts a receiving connector portion 260 which
`engages with contacts 252 on the connector 210 to provide
`an electrical connection between the optical probe 202 and
`the pulse oximeter 140. Once the optical probe 202 is
`securely fastened to the fingertip 250 and the connector 210
`provides an electrical connection between the optical probe
`202 and digital signal processing circuitry, signals are
`detected from the detector 235 and transmitted to the pro-
`cessing circuitry via the connector 260.
`A probe-off condition occurs when the optical probe
`becomes partially or completely dislodged from the patient,
`but continues to detect an AC signal within the operating
`region of the pulse oximeter. Probe-off errors are serious
`because the pulse oximeter may display a normal saturation
`when,
`in fact,
`the probe is not properly attached to the
`patient, potentially leading to missed desaturation events.
`Failure to detect a probe-off condition is the result of the
`probe detector receiving light directly from the emitters
`without transmission through the patient’s tissue.
`As illustrated in the schematic of FIG. 3A, a first aspect
`of the present invention involves an optical probe 202 which
`incorporates a number of electrical contacts 341 and 342 that
`make contact to the skin of the patient when the probe 202
`is properly secured. In order to detect a probe-off condition,
`a probe-off detector module 138 of the pulse oximeter 140
`periodically applies a voltage across the contacts 341 and
`342 or drives a current. A non-zero current indicates that the
`
`patient’s skin 344 has closed the circuit between the contacts
`341 and 342 and the probe 202 is properly secured. If the
`probe becomes dislodged, the patient’s skin 344 is no longer
`be in contact with the contacts 341 and 342, resulting in an
`open circuit.
`FIG. 3B illustrates one preferred embodiment of an opti-
`cal probe 202 incorporating one embodiment of the present
`invention. The present embodiment incorporates a first elec-
`trical contact 341 and a second electrical contact 342 in the
`
`surface 306 of the central portion 204 of the probe 202. The
`electrical contacts 341 and 342 are positioned in a location
`such that contact to a finger or flesh portion of the patient is
`ensured when the probe 202 is properly attached. In the
`illustrated embodiment, the contacts 341 and 342 are located
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`US 6,771,994 B2
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`5
`proximate the detector aperture 203. In another embodiment,
`contacts 341 and 342 are on opposite sides of the detector
`aperture 203. The optical probe 202 also has an emitter
`aperture 220 through which light of at least two wavelengths
`passes from LEDs.
`As illustrated in the schematic diagram of FIG. 3C, the
`pulse oximeter system 100 of FIG. 1 can be modified to
`incorporate the first aspect of the present
`invention by
`extending an additional lead 324 through the connector 142
`to the probe 202. The additional lead can be connected to
`one contact 341 while the second contact 342 can be wired
`
`to the common ground lead 130.
`A schematic diagram of another embodiment of the
`present invention is illustrated in FIG. 3D. The contacts 341
`and 342 can be installed in line within the path of the coding
`resistor 132. When the patient’s skin 344 is in contact with
`the contacts 341 and 342, the circuit through the coding
`resistor 132 will be closed; when the patient’s skin 344 is not
`in contact with the contacts 341 and 342, the circuit through
`the coding resistor 132 will be open. The skin 344 will have
`some finite resistance between the contacts 341 and 342 that
`
`will affect the measured resistance of the coding resistor. As
`the contacts 341 and 342 are installed in series with the
`
`coding resistor 132, any resistance across the contacts 341
`and 342 will be added to the resistance of the coding resistor
`132 when the pulse oximeter 140 attempts to measure the
`resistance of the coding resistor 132. The resistance of the
`skin 344 can effectively be ignored in the measurement of
`the coding resistor 132, however, by choosing the value of
`the coding resistor 132 to be substantially larger than the
`resistance of a patient’s skin 344 between the contacts 341
`and 342. Alternatively,
`the acceptable resistance for the
`coding resistor can be specified as in a range that includes
`the likely added resistance of the skin in the circuit. In the
`present configuration, the probe-off detector module 138 of
`the pulse oximeter 140 can verify that the optical probe 202
`is properly secured simultaneously with checking the resis-
`tance of the coding resistor 132. An open circuit indicates
`that
`the probe has become dislodged, whereas a valid
`resistance of a coding resistor 132 indicates a proper attach-
`ment of the probe 202. If the probe has become dislodged,
`the pulse oximeter 140 can sound an alarm, display a
`warning message, or both.
`The pulse oximeter 140 is particularly vulnerable to
`probe-off errors when operating at its highest sensitivity,
`where even small
`induced variations in light directly
`detected from the emitters have sufficient signal strength to
`be processed as a physiological signal.
`In a probe-off
`condition, a detector AC signal can be induced by slight
`changes in the direct light path between the emitters and the
`detector. For example, small amounts of patient motion,
`such as chest movement from breathing, can induce a
`probe-off AC signal. As another example, “creep” in the
`probe configuration, such as a folded probe gradually return-
`ing to its original unfolded shape after becoming dislodged
`can also induce a probe-off AC signal.
`FIGS. 3E and 3F depict a generalized embodiment of the
`present invention with the same features as described in 3A
`and 3B, except that the electrical contacts 341, 342 are
`replaced with a contact sensor 343. The electrical contacts
`341 and 342 comprise a specialized case of a contact sensor
`343 where skin is involved. The contact sensor 343 may also
`comprise a piezoelectric sensor, a conductive contact sensor,
`or any other contact sensors which detect the contact of the
`tissue material.
`
`FIGS. 3G and 3H depict yet another embodiment of the
`electrical contact based contact sensor of FIGS. 3A and 3B.
`
`6
`FIG. 3G depicts a schematic form with a pulse oximeter 140
`and a probe off detector module. FIG. 3H depicts a perspec-
`tive view of the optical pulse oximeter probe haveing optical
`emitters and at
`least one detector. However,
`in this
`embodiment, electrical contact 341A and electrical contact
`342 are positioned opposite each other. The electrical con-
`tact 341A is positioned near the emitter aperture 220, so as
`to contact the portion of the tissue material near the emitter
`220. The electrical contact 342 is positioned near the detec-
`tor aperture 203. Similarly, other contact sensors could be
`positioned, one near the emitter aperture 220 and one near
`the detector aperture 203.
`In one embodiment the electrical contacts 341, 342, 341A
`are metallic. In another embodiment, these contacts com-
`prise conductive adhesive, or gel based contacts.
`FIG. 4 illustrates a probe 202 that has become unfastened.
`The illustrated probe 202 is shown in a partially unfolded
`shape that provides an oblique path 410 from the emitter
`aperture 220 to the detector assembly 235. As a patient
`moves, or as the probe 202 unfolds, rays of light travelling
`along the oblique light path 410 may generate an AC signal
`that could be interpreted by the pulse oximeter 140 as a
`physiological signal.
`As illustrated in the cross section of FIG. 5A, a number of
`louvers 502 are placed in front of the detector assembly 235
`within the detector aperture 203 in accordance with a second
`aspect of the present invention. The louvers 502 block light
`rays travelling along an oblique path 410 (i.e., light that does
`not originate from in front of the detector assembly 235). As
`illustrated in FIG. 5B, if the probe 202 is properly attached,
`the emitter aperture 220 will be directly in front of the
`detector assembly 235 and light rays will pass directly
`through the louvers 502 along a direct path 510.
`FIG. 5C illustrates a top plan view of a preferred embodi-
`ment of this aspect of the present invention. The detector
`aperture 203 is formed in a plastic body 504 having slots 506
`to hold the louvers 502 in place across the detector aperture
`203. In a preferred embodiment of the present aspect, the
`louvers 502 can be created from commercially available
`“3M Light Control Film.”
`The louvers 502 of the present aspect advantageously
`provide a separate or improved method for the pulse oxime-
`ter 140 to determine when a probe has become dislodged
`through monitoring the signal produced by the photodetector
`116. If the probe 202 becomes improperly secured,
`the
`emitter aperture will likely move from its proper location
`directly above the detector assembly 235, which will cause
`any oblique light rays to be blocked by the louvers 502. With
`no light rays reaching the detector assembly 235, the detec-
`tor will produce no signal. The probe-off detector 138 of the
`pulse oximeter 140 can detect the lack of signal and sound
`an alarm. The louvers 502 also advantageously block
`oblique light rays that might create a false signal that could
`be interpreted by the pulse oximeter 140 to be a physiologi-
`cal signal. Accordingly, the louvers 502 reduce or eliminate
`the possibility of a probe-off condition. The louvers 502 may
`be used alone or in combination with the contacts described
`herein.
`
`FIG. 6 illustrates one embodiment of a method 600 by
`which a pulse oximeter 140 detects a dislodged probe and/or
`a probe-off condition. At a step 604, the probe off detector
`module 138 checks for continuity between the skin contacts
`341 and 342. If, at a step 608, there is continuity between the
`contacts 341 and 342, the oximeter 140 passes control to a
`step 612. If, on the other hand, there is no continuity at the
`step 608, the oximeter 140 passes control to a step 620. At
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`US 6,771,994 B2
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`7
`step 620 the oximeter 140 sounds an alarm to alert a
`condition necessitating attention. At the step 612, the oxime-
`ter 140 checks for a valid AC signal from the photodetector.
`If, at a step 616, there is a valid signal, the oximeter 140
`passes control back to the step 604 to start the cycle over
`again. If, on the other hand, there is no valid AC signal at the
`step 616 the oximeter sounds an alarm at
`the step 620.
`Accordingly,
`the pulse oximeter checks for and detects
`dislodgment of a probe and/or a probe-off condition.
`While certain exemplary preferred embodiments have
`been described and shown in the accompanying drawings, it
`is to be understood that such embodiments are merely
`illustrative of and not restrictive on the broad invention.
`Further, it is to be understood that this invention shall not be
`limited to the specific construction and arrangements shown
`and described since various modifications or changes may
`occur without departing from the spirit and scope of the
`invention as claimed. It is intended that the scope of the
`invention be limited not by this detailed description but by
`the claims appended hereto.
`What is claimed is:
`
`1. A pulse oximetry probe comprising:
`a flexible probe body configured to contact the skin of a
`patient on opposing surfaces of a body member of the
`patient when the probe body is properly affixed to the
`patient;
`light emitting diodes incorporated into the probe body;
`a light sensitive detector which detects light from a first
`direction originally emitted by the light emitting
`diodes, wherein the light comprises at least first and
`second wavelengths and has been transmitted through
`body tissue carrying pulsing blood; and
`at least one structure positioned approximately parallel to
`the first direction and is configured to filter out light
`from reaching the light sensitive detector from a direc-
`tion substantially different from the first direction.
`2. The pulse oximetry probe of claim 1, wherein the
`structure comprises one or more louvers.
`3. The pulse oximetry probe of claim 1, wherein the
`structure comprises a plurality of louvers.
`4. The pulse oximetry probe of claim 1, further compris-
`ing a coding resistor.
`5. The pulse oximetry probe of claim 1, further compris-
`ing an circuit configured to contact at least a portion of the
`body tissue.
`6. The pulse oximetry probe of claim 1, wherein the
`flexible probe body comprises a reusable optical probe.
`7. The pulse oximetry probe of claim 1, wherein the
`flexible probe body comprises a disposable optical probe.
`8. The pulse oximetry probe of claim 1, wherein the
`flexible probe body comprises reusable and disposable por-
`tions of an optical probe.
`9. A pulse oximeter for processing signals received from
`an optical probe, the pulse oximeter comprising:
`an input for receiving at least first and second intensity
`signals from a light-sensitive detector which detects
`
`8
`light of at least first and second wavelengths transmit-
`ted through body tissue carrying pulsing blood; and
`a signal processor which determines a probe-off condition
`when at
`least one of the first and second intensity
`signals is substantially attenuated.
`10. The pulse oximeter of claim 9, wherein the attenuation
`is caused by improper application an optical probe to the
`body tissue.
`11. The pulse oximeter of claim 9, further comprising an
`audio alarm indicating when the probe-off condition is
`determined.
`
`12. The pulse oximeter of claim 9, further comprising an
`visual alarm indicating when the probe-off condition is
`determined.
`
`13. The pulse oximeter of claim 9, further comprising a
`coding resistor.
`14. The pulse oximeter of claim 9, further comprising an
`circuit configured to contact at least a portion of the body
`tissue.
`
`15. A sensor which generates at least first and second
`intensity signals from a light-sensitive detector which
`detects light of at least first and second wavelengths trans-
`mitted through body tissue carrying pulsing blood;
`the
`sensor comprising:
`at least one light emission device;
`a light sensitive detector; and
`a plurality of louvers positioned over the light sensitive
`detector to accept
`light from the at
`least one light
`emission device originating from a general direction of
`the at least one light emission device and then trans-
`mitting through body tissue carrying pulsing blood,
`wherein the louvers accept the light when the sensor is
`properly applied to tissue of a patient.
`16. A method of processing one or more signals to detect
`a condition of improper positioning of an optical probe, the
`method comprising:
`expecting to receive at least first and second intensity
`signals from a light-sensitive detector which detects
`light of at least first and second wavelengths transmit-
`ted through body tissue carrying pulsing blood;
`blocking light originating from an angle oblique to a
`proximate relationship between the detector and a light
`source; and
`receiving one of an un-interpretable signal or signal other
`than the expected first and second intensity signals
`because the light is blocked; and
`indicating a probe off condition.
`17. The method of claim 16, wherein the indicating
`comprises at least one of an audible or visual alarm.
`18. The method of claim 16, wherein blocking light
`comprises positioning a plurality of louvers between the
`light source and the light-sensitive detector.
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`UNITED STATES PATENT AND TRADEMARK OFFICE
`
`CERTIFICATE OF CORRECTION
`
`PATENT NO.
`APPLICATION NO.
`
`: 6,771,994 B2
`: 10/374303
`
`DATED
`INVENTOR(S)
`
`: August 3, 2004
`: Massi E. Kiani
`
`Page 1 of 1
`
`It is certified that error appears in the above-identified patent and that said Letters Patent is
`hereby corrected as shown below:
`
`At column 2, line 36, delete “embodimet” and insert -- embodiment --, therefore.
`
`At column 6, line 3, delete “haveing” and insert -- having --, therefore.
`
`Signed and Sealed this
`
`Seventeenth Day of July, 2007
`
`m WADE,”
`
`JON W. DUDAS
`Director ofthe United States Patent and Trademark Oflice
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