Magnetic-flap optical sensor

[0001] The present application claims priority benefit under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/716,486, filed Oct. 20, 2012, titled Magnetic-Flap Optical Sensor, hereby incorporated in its entirety by reference herein.

[0002] Noninvasive physiological monitoring systems for measuring constituents of circulating blood have advanced from basic pulse oximeters to monitors capable of measuring abnormal and total hemoglobin among other parameters. A basic pulse oximeter capable of measuring blood oxygen saturation typically includes an optical sensor, a monitor for processing sensor signals and displaying results and a cable electrically interconnecting the sensor and the monitor. A pulse oximetry sensor typically has a red wavelength light emitting diode (LED), an infrared (IR) wavelength LED and a photodiode detector. The LEDs and detector are attached to a patient tissue site, such as a finger. The cable transmits drive signals from the monitor to the LEDs, and the LEDs respond to the drive signals to transmit light into the tissue site. The detector generates a photoplethysmograph signal responsive to the emitted light after attenuation by pulsatile blood flow within the tissue site. The cable transmits the detector signal to the monitor, which processes the signal to provide a numerical readout of oxygen saturation (SpO₂) and pulse rate, along with an audible indication of the person's pulse. The photoplethysmograph waveform may also be displayed.

[0003] Conventional pulse oximetry assumes that arterial blood is the only pulsatile blood flow in the measurement site. During patient motion, venous blood also moves, which causes errors in conventional pulse oximetry. Advanced pulse oximetry processes the venous blood signal so as to report true arterial oxygen saturation and pulse rate under conditions of patient movement. Advanced pulse oximetry also functions under conditions of low perfusion (small signal amplitude), intense ambient light (artificial or sunlight) and electrosurgical instrument interference, which are scenarios where conventional pulse oximetry tends to fail.

[0004] Advanced pulse oximetry is described in at least U.S. Pat. Nos. 6,770,028; 6,658,276; 6,157,850; 6,002,952; 5,769,785 and 5,758,644, which are assigned to Masimo Corporation (“Masimo”) of Irvine, Calif. and are incorporated by reference in their entirety herein. Corresponding low noise optical sensors are disclosed in at least U.S. Pat. Nos. 6,985,764; 6,813,511; 6,792,300; 6,256,523; 6,088,607; 5,782,757 and 5,638,818, which are also assigned to Masimo and are also incorporated in their entirety by reference herein. Advanced pulse oximetry systems including Masimo SET® low noise optical sensors and read through motion pulse oximetry monitors for measuring SpO₂, pulse rate (PR) and perfusion index (PI) are available from Masimo. Optical sensors include any of Masimo LNOP®, LNCS®, SofTouch™ and Blue™ adhesive or fixed sensors. Pulse oximetry monitors include any of Masimo Rad-8®, Rad-5®, Rad®-5v or SatShare® monitors.

[0005] Advanced blood parameter measurement systems are described in at least U.S. Pat. No. 7,647,083, filed Mar. 1, 2006, titled Multiple Wavelength Sensor Equalization; U.S. Pat. No. 7,729,733, filed Mar. 1, 2006, titled Configurable Physiological Measurement System; U.S. Pat. No. 7,957,780, filed Mar. 1, 2006, titled Physiological Parameter Confidence Measure and U.S. Pat. No. 8,190,223, filed Mar. 1, 2006, titled Noninvasive Multi-Parameter Patient Monitor, all assigned to Cercacor Laboratories, Inc. (“Cercacor”) of Irvine, Calif. (formerly Masimo Laboratories, Inc.) and all incorporated in their entirety by reference herein. Advanced parameter sensors include U.S. Pat. No. 8,203,704, filed Aug. 3, 2009, titled Multi-Stream Sensor For Noninvasive Measurement of Blood Constituents and U.S. Pat. No. 8,233,955 filed Nov. 29, 2006, titled Optical Sensor Including Disposable and Reusable Elements, all assigned to Cercacor.

[0006] Advanced blood parameter measurement systems include Masimo Rainbow® SET, which provides measurements in addition to SpO₂, such as total hemoglobin (SpHb™), oxygen content (SpOC™), methemoglobin (SpMet®), carboxyhemoglobin (SpCO®) and PVI®. Advanced blood parameter sensors include Masimo Rainbow® adhesive, ReSposable™ and fixed sensors. Advanced blood parameter monitors include Masimo Radical-7™, Rad87™ and Rad57™ monitors, all available from Masimo. Such advanced pulse oximeters, low noise sensors and advanced blood parameter measurement systems have gained rapid acceptance in a wide variety of medical applications, including surgical wards, intensive care and neonatal units, general wards, home care, physical training, and virtually all types of monitoring scenarios.

[0007] A magnetic-flap optical sensor is configured to attach to a tissue site so as to illuminate the tissue site with optical radiation and detect the optical radiation after attenuation by pulsatile blood flow within the tissue site. The sensor communicates with a physiological monitor so as to calculate parameters corresponding to constituents of the pulsatile blood flow. The sensor has top and bottom finger clip shells connected by a pivot pin and urged together by a spring. The shells retain pads that receive an inserted fingertip and position this tissue site with respect to emitters and detector(s) so as to allow the sensor processor to activate the emitters and receive a corresponding signal from the detector(s) indicative of a physiological characteristic of the tissue site. The emitters and detector(s) are retained between the shell and the pads. An active pulser is retained between the shell and the lower pad. Magnetic flaps extend from an upper one of the pads and are urged against the bottom shell, advantageously occluding blood flow out of the inserted fingertip and accentuating the active pulse induced signal accordingly.

[0008] One aspect of a magnetic-flap optical sensor is an emitter shell having an emitter. An emitter pad is at least partially disposed within the emitter shell. A detector shell has a detector. A detector pad is at least partially disposed within the detector shell. The emitter is configured to transmit optical radiation into fingertip tissue inserted between the emitter pad and detector pad. The detector is configured to receive optical radiation after attenuation by pulsatile blood flow within fingertip tissue so as to generate a detector signal. Flaps extend over side portions of at least one of the detector shell and the emitter shell. The flaps are configured to block external light from entering between the emitter pad and detector pad when fingertip tissue is inserted between the emitter pad and detector pad. An active pulser is disposed within the sensor so as to generate an artificial pulse within the fingertip tissue. The emitter shell and detector shell mechanically are urged together to create a first squeezing force on fingernail and finger pad portions of the fingertip. The flaps are further configured to create a second squeezing force on side portions of the fingertip. The first and second squeezing forces act to occlude blood flow from the fingertip tissue so as to accentuate the detector signal due to the artificial pulse.

[0009] In various embodiments, the magnetic-flap optical sensor further comprises shell magnets disposed on at least one of the shells and flap magnets disposed on the flaps. The shell magnets and flap magnets are urged together so that the flaps create the second squeezing force. The flaps extend from the emitter shell and the shell magnets are disposed on the detector shell. The shell magnets are disposed on side portions of the detector shell. The flap magnets are disposed on flap portions distal the emitter shell. The flap magnets are configured to have opposite north and south orientations from the shell magnets. Alternatively, magnets are disposed on at least one of the shells and metal strips are disposed on the flaps. The magnets and metal strips are urged together so that the flaps create the second squeezing force.

[0010] Another aspect of a magnetic-flap optical sensor disposes an emitter of optical radiation proximate a fingernail and a detector of optical radiation proximate a fingertip pad generally opposite the emitter. The fingertip pad is actively pulsed, and the fingertip is occluded so as to accentuate blood volume within the fingertip and accentuate an active pulse detector signal accordingly. In various embodiments, occlusion comprises compressing the fingertip between fingernail and finger pad with a sensor clip and further compressing the fingertip sides. Compressing the fingertip sides comprises disposing flaps along the finger tip sides so as to block ambient light from the detector and pressing the flaps against the fingertip sides. Pressing the flaps comprises disposing a first set of magnets on end portions of the flaps and disposing a second set of magnets on side portions of the sensor clip. The first set and second set of magnets are oriented so as to urge the flap ends against the sensor clip sides.

[0011] In various embodiments, metal strips are disposed on end portions of the flaps, magnets are disposed on side portions of the sensor clip, and the metal strips and the magnets are proximately located so as to urge the flap ends against the sensor clip sides. Alternatively, magnets are disposed on end portions of the flaps, metal strips are disposed on side portions of the sensor clip, and the magnets and the metal strips are proximately located so as to urge the flap ends against the sensor clip sides. The magnets may be disposed on a detector shell portion of sensor clip.

[0012] A further aspect of a magnetic-flap optical sensor comprises a sensor clip means for retaining a fingertip relative to a emitter and a detector and for partially occluding blood flow so as to retain a blood volume within the fingertip. A flap means is for blocking light and for further occluding blood flow. An active pulse means is for creating an artificial pulse within the retained blood volume. The flap means may comprise a magnetic means for securing the flap means to the sensor clip means. The magnetic means may comprise a first rare-earth magnet disposed in a first orientation in the flap means. The magnetic means may also comprise a second rare-earth magnet disposed in a second orientation in the clip means. The magnetic means may comprise a metal strip disposed in the clip means. The magnetic means may also comprise a metal strip disposed in the flap means and a rare-earth magnet disposed in the clip means.

[0019] FIG. 1 illustrates a noninvasive physiological monitoring assembly 100 having a magnetic flap optical sensor 20 in communications with a multi-parameter monitor 10. The magnetic flap optical sensor 20 is configured to illuminate a fingertip 30 with multiple wavelength optical radiation and detect the optical radiation after attenuation by pulsatile blood flow within the fingertip 30. In an embodiment, the sensor 20 has a reusable finger clip 22 that removably and reusably attaches to the fingertip 30 and a sensor cable 24 that communicates with the monitor 10. Advantageously, the finger clip 22 has magnetic flaps 26 that occlude blood flow within the fingertip 30 so as to accentuate pulsatile blood flow in response to an mechanically-generated “active” pulse. In particular, the magnetic flaps 26 capture a higher blood volume within the fingertip 30 resulting in a larger pulsatile optical signal in response to the active pulse. Magnetic flap fingertip occlusion is described in further detail with respect to FIGS. 2A-C, below. Optical illumination and active pulsation of the fingertip is described in further detail with respect to FIGS. 2D-E, below. A magnetic flap optical sensor 300 embodiment is described in further detail with respect to FIGS. 3-5, below.

[0020] FIGS. 2A-E illustrate magnetic flap fingertip occlusion for accentuating an active pulse and a corresponding optical illumination of a fingertip tissue site, detection of the optical illumination after attenuation by pulsatile blood flow with the tissue site, and active pulsation of the tissue site. As shown in FIG. 2A, a fingertip 30 is initially disposed within a finger clip sensor 200 in a fully open position 201. In particular, the fingertip 30 is positioned between sensor halves 210, 220. Magnetic flaps 240 extend from the sensor upper half 210 along the sides of the fingertip 30. The magnetic flaps 240 have flap magnets 250 disposed proximate the flap ends. Clip magnets 260 are disposed along the sides of the sensor lower half 220.

[0021] As shown in FIG. 2B, releasing finger pressure from the finger clip sensor 200 moves the finger clip sensor 200 to a partially closed position 202. In particular, the upper half 210 and lower half 220 are urged together by a connecting spring and clamp down on the fingertip 30, which creates a clip force 5 that partially occludes the blood flow. The partially closed position 202 also brings the flap magnets 250 proximate the clip magnets 260. Mutual attraction of these magnets 250, 260 moves the finger clip sensor 200 to a fully closed position 203 (FIG. 2C).

[0022] As shown in FIG. 2C, once the finger clip sensor 200 is in the fully closed position 203, opposite facing poles of the flap magnets 250 and the clip magnets 260 urge the flaps 240 against the sides of the fingertip 30. This creates a flap force 6 that advantageously further occludes the blood flow beyond that of the clip force 5 (FIG. 2B).

[0023] As shown in FIGS. 2D-E, in the fully closed position 203, LEDs 270 (not illustrated above) illuminate the tissue site 30 with multiple wavelength optical radiation 272. Pulsatile blood flow within the tissue site attenuates the optical radiation 276, which is sensed by one or more detectors 280 (not shown above). The attenuating pulsatile blood flow is arterial blood flow and artificially pulsed blood flow responsive to an active pulse 218, such as a motor-driven mechanical pulser that variably presses against the fleshy pad 32 of the fingertip 30.

[0024] FIGS. 3-5 illustrate a magnetic-flap optical sensor finger clip 300 embodiment that accommodates a person's fingertip 30 (FIG. 1). As shown in FIGS. 3A-B, the sensor 300 has an emitter section 310 that is pivotably connected to a detector section 320. Clip grips 330 are disposed at the sensor front and are compressed to open the sensor 300 so as to present a finger space 340 at the sensor back for insertion of a fingertip 30 (FIG. 1). The clip grips 330 are released so as to enclose the fingertip 30 within the sensor, as described with respect to FIGS. 2A-C, above. The emitter section 310 houses multiple wavelength LED emitters 270 (FIG. 2D) and the detector section 320 houses one or more photodiode detectors 280 (FIG. 2D). Extending from either side of the emitter section 310 are magnetic flaps 350 that both block ambient light from the enclosed fingertip and occlude blood flow in the fingertip, as described with respect to FIGS. 2A-C, above.

[0025] FIG. 4 further illustrates the sensor 300 having an emitter section 310 that is pivotably connected with a detector section 320 around hinge pins 460. The emitter section 310 has a heat sink 410, an emitter shell 420 and an emitter pad 430. The detection section 320 has a detector shell 440 and a detector pad 450. Together, a top grip 422 and a bottom grip 442 form the clip grips 330 (FIGS. 3A-B). The emitter pad 430 attaches to the emitter shell 420 and has a pair of magnetic flaps 350 extending toward and along each side of the detector shell 440. The magnetic flaps 350 are constructed of a semi-rigid material. A pair of imbedded top magnets 470 are disposed distal the emitter shell 420. The detector shell 480 has a pair of bottom magnets 480 disposed on the sides of the detector shell 440 so as to generally align with the top magnets 470 in a clip closed position. The shells 420, 440 pivot around the hinge pins 460, which are inserted through pin apertures 424, 444 and capture a hinge spring (not shown) that urges the sensor 300 to a closed position. A bend relief 460 is captured between the emitter shell 420 and emitter pad 430 and receives a sensor cable 24 (FIG. 1).

[0026] FIGS. 5A-C illustrate various magnet placement embodiments. As shown in FIG. 5A, in a first embodiment 501, magnets 470, 480 are placed with outer-facing south poles (S) so that inner-facing flap magnet north poles (N) are attracted to outer-facing shell magnet south poles (S). As shown in FIG. 5B, in a second embodiment 502, magnets 470, 480 are placed with outer-facing north poles (N) so that inner-facing flap magnet south poles (S) are attracted to outer-facing shell magnet north poles (N). As shown in FIG. 5C, in a third embodiment 503, magnets 470, 480 are placed with mixed-facing poles so that mixed-facing flap magnet poles are attracted to oppositely-facing shell magnet poles. In other embodiments (not shown), some of the magnets 470, 480 are replaced with metal bars so that the remaining magnets 470, 480 are attracted to the metal bars. In an embodiment, the magnetics 470, 480 are rare-earth magnets. A reusable, active-pulsed, finger clip optical sensor is disclosed in U.S. patent application Ser. No. 13/473,477, titled Personal Health Device, assigned to Cercacor Laboratories, Inc., Irvine, Calif., and hereby incorporated in its entirety by reference herein.

[0027] A magnetic-flap optical sensor has been disclosed in detail in connection with various embodiments. These embodiments are disclosed by way of examples only and are not to limit the scope of the claims that follow. One of ordinary skill in art will appreciate many variations and modifications.