Optical power modulation

Optical power modulation {OPTICAL POWER MODULATION}

FIELD OF THE INVENTION The present invention relates to detecting vital signs, and more particularly to a device for measuring vital signs.

Blood pressure refers to the force applied by circulating blood on the walls of blood vessels and constitutes one of the major vital signs. Systolic blood pressure is the highest blood pressure in the arteries and occurs near the beginning of the cardiac cycle. The diastolic blood pressure is the diastolic blood pressure and is in the resting phase of the cardiac cycle. The mean pressure over the entire cardiac cycle is reported as mean arterial blood pressure. The pulse pressure reflects the difference between the measured maximum and minimum pressures.

Blood pressure can be measured invasively (by measuring it inside a blood vessel through the skin) or non-invasively. Invasive measures are generally limited to hospital settings. Non-invasive auscultation and vibration measurements are simpler and faster than invasive methods, have fewer complications, and are less unpleasant and less painful for the patient. Non-invasive assays are more commonly used for routine inspection and monitoring.

Auscultation usually uses a stethoscope and a blood pressure monitor. An inflatable cuff is placed around the upper arm at approximately the same vertical height as the heart and is pneumatically connected to a mercury sphygmomanometer or aneroid gauge. The mercury sphygmomanometer measures the height of the column of mercury, providing an absolute cuff pressure measurement without the need for calibration and thus subject to calibration errors and drifts affecting other pressure gauges. The cuff is inflated manually by repeatedly compressing the rubber bulb until the brachial artery is completely occluded. While listening with a stethoscope over the brachial artery on the distal side of the compressed cuff, the examiner slowly releases the pressure in the cuff. When blood is just starting to flow in the artery, the turbulence produces a "whooshing" or pounding sound (the first Korotkoff sound). The pressure at which this sound is first heard is the systolic blood pressure. The cuff pressure is further released until no sound is heard in the diastolic blood pressure (5th Korotkoff sound).

Vibration measurements are often used for continuous monitoring, and often to perform single measurements. The instrument is functionally similar to that of the stethoscope, but does not rely on the use of a stethoscope and the examiner's ear. Instead, the detection means is a pressure sensor that is pneumatically connected to the cuff and records (relatively small) oscillations in the cuff pressure synchronous with the arterial pressure waveform. The first oscillation of cuff pressure does not occur at systolic blood pressure, but does occur at cuff pressures substantially above systolic blood pressure. The cuff is initially inflated to a blood pressure that exceeds the systolic pressure. The cuff pressure is then gradually reduced. The values of systolic and diastolic blood pressure are calculated from the different oscillation amplitudes occurring at various cuff pressures by use of an algorithm. Algorithms used to calculate systolic and diastolic blood pressures often use experimentally obtained coefficients for the purpose of matching vibration measurement results as best as possible to results obtained using auscultation methods.

In some aspects, a vital sign measurement device includes a sensor fixation device, a sensor frame held by the sensor fixation device, a light sensing system held by the sensor frame, and an output unit. The sensor fixation device is configured to be positioned relative to an anatomical location of the patient in which the artery is located. The optical sensing system includes an optical waveguide, a light source device that supplies optical energy to the optical waveguide, and a photodetector that detects an amount of optical energy exiting the optical waveguide. The optical sensing system is configured to detect an arterial pulse from compression or bending of at least a portion of the optical waveguide, which results in a reduction in the amount of light exiting the second end of the optical waveguide. The output unit receives a signal indicative of the amount of light exiting the optical waveguide and generates a measure of the vital sign based at least in part on the received signal.

The vital sign measurement device works on the principle of optical power modulation, ie, an arterial pulse causes bending or compression of the optical waveguide resulting in a change in the amount of optical energy delivered to the second end of the optical waveguide. By monitoring the amount of light exiting the second end of the optical waveguide, data regarding the arterial pulse can be obtained and used to determine various vital signs. The light sensing system may be configured to detect an optical signal representative of the series of arterial pulses, and wherein the output unit generates a pulse waveform for each of the series of arterial pulses based on the amount of light energy exiting the second end of the optical waveguide. can be configured to determine. The optical sensing system may be configured to detect a pulsatile opening of an artery by compression or bending of the compressible optical waveguide resulting in a pulsatile decrease in the amount of detected light. The photo detector is optically coupled to the optical waveguide, such that the photo detector receives substantially all of the optical energy from the light source that does not escape from the side of the optical waveguide. The light source may include a coherent light source.

In some implementations, the sensor fixation device can be a cuff that includes an inflatable bladder within the cuff. An inflatable bladder may partially enclose a limb. The cuff may be made of a textile material. The cuff may be configured to apply pressure to the anatomical location, thereby compressing an artery in the anatomical location. For example, the cuff may apply pressure when the inflatable bladder is inflated. The sensor frame may be attached to the cuff at a location that does not coincide with any portion of the bladder. The sensor frame is held against the limb by its attachment to the cuff such that the pressure applied to the limb by the sensor frame is substantially equal to the pressure applied to the limb by the surrounding cuff when the inflatable bladder is inflated. .

In some implementations, the device may include a sensor pad within a sensor frame, which may be positioned adjacent to an anatomical location. The sensor pad may be configured to move as a result of the increased contact pressure generated by the expansion of the bladder. Movement of the sensor pad may result in compression or bending of the optical waveguide. In some implementations, the sensor pad may be positioned at a midpoint of the sensor fixation device. In other implementations, the sensor pad may be located in a distal location of the sensor fixation device. In some implementations, the sensor pad is such that pulsating tension of the sensor fixation device does not result in pulsatile movement of the sensor pad, while pulsating opening of an artery in the anatomical location causes pulsating movement of the sensor pad. can be configured. In some implementations, the maximum contact pressure applied to the sensor pad can result in a 20-80% reduction (eg, a 50-70% reduction) in the total amount of light exiting the optical waveguide.

In some implementations, the device can include a load spring that is attached to at least a portion of the sensor frame and also supports the sensor pad. The load spring may be configured to counteract at least a portion of the pressure applied to the sensor pad at the patient's anatomical location. The load spring may be configured to allow a desired displacement of the sensor pad at maximum pressure. In some implementations, the load spring may be configured to provide a maximum displacement of the sensor pad of 0.5 to 3 millimeters at maximum pressure.

In some implementations, the device may include a pressure sensor that detects pressure applied to an anatomical location. The output unit may receive a pressure input indicative of the pressure applied to the anatomical location from the pressure sensor. In some implementations, the output unit may generate a vital sign using the signal and pressure input indicative of the received optical signal.

In some embodiments, the anatomical location of the patient is the upper arm. A sensor frame is configured on the sensor fixation device so that the light sensing system is positioned to detect movement resulting from a pulse of the brachial artery resulting in compression or bending of at least a portion of the compressible optical waveguide. In some embodiments, the vital sign can be at least one of heart rate, arterial pulse waveform, systolic blood pressure, diastolic blood pressure, mean arterial blood pressure, pulse pressure, and arterial compliance.

In some implementations, a device can include a waveguide support structure having an inelastic support surface that supports at least a portion of the optical waveguide. The optical sensing system may be configured to generate a flexural deformation of the unsupported portion of the optical waveguide in response to the arterial pulse.

In some implementations, a device can include a flexible and incompressible support surface that supports the optical waveguide over substantially its entire length. For example, the waveguide support surface may be a flexible electronic circuit board. The waveguide may be bonded to the support surface with a flexible elastomeric adhesive. In some implementations, the light source device, photo detector, and/or associated electronic component may be mounted on the surface of the waveguide support surface. In some implementations, the waveguide support surface may include a support return element configured within the support surface to oppose the curvature of the support surface. In some implementations that include a sensor pad, the support return element may be configured to provide increasing contact pressure between the sensor pad and the optical waveguide as the sensor pad moves from the rest position to the position of maximum displacement. The optical waveguide may be configured such that the increasing contact pressure results in a decreasing amount of light exiting the second end of the optical waveguide.

In some aspects, a method of measuring a vital sign in a patient comprises delivering optical energy into a first end of the optical waveguide, detecting an amount of optical energy exiting a second end of the optical waveguide, and a second end of the optical waveguide. generating a measure of the vital sign based on the detected amount of light energy exiting the end. The optical waveguide is positioned with the sensor frame and the sensor frame is positioned relative to the anatomical location of the patient with the artery therein. The optical waveguide is positioned to compress or bend in response to the arterial pulse. The amount of light energy exiting the second end of the optical waveguide is detected using a photo detector held by the sensor frame. The photo detector generates a signal indicative of the amount of received light energy. The amount of light energy exiting the second end of the optical waveguide changes in response to the arterial pulse.

In some implementations, the sensor frame may be held by a sensor fixation device, and the method may further include applying pressure to the patient's anatomical location with the sensor fixation device. In some implementations, the method comprises varying the pressure applied to the anatomical location with the sensor fixation device over a period of time and from a change in the amount of light energy exiting the second end of the optical waveguide over the period of time. The method may further comprise determining a series of pulse characteristics for the arterial pulse over a period of time. The generated measure of vital signs may be based on a series of pulse characteristics over a period of time.

In some embodiments, the method may include obtaining a measured blood pressure measurement and then evaluating a second blood pressure measurement. Evaluating the second blood pressure measurement may be based on an initial pulse characteristic obtained at an initial time and subsequent pulse characteristics obtained at a later time used to evaluate the second blood pressure measurement. The initial time is closer to the time of the measured blood pressure assessment than at a later time. The generated measures of vital signs are based on the measured blood pressure measurements, the initial pulse characteristics, and the subsequent pulse characteristics. In some implementations, the initial and subsequent pulse characteristics may be pulse amplitudes.

In some aspects, a method of measuring a patient's blood pressure comprises applying a variable pressure to an anatomical location of the patient having an artery therein, detecting an arterial pulse waveform with an optical power modulated sensor, and applied and altered pressure and determining the systolic blood pressure and the diastolic blood pressure based on the detected arterial pulse waveform as a function of . The optical power modulated sensor includes an optical waveguide configured to compress or bend in response to an arterial pulse. Compression or bending of the optical waveguide results in a decrease in the amount of light transmitted to the end of the optical waveguide. The arterial pulse waveform is detected from the amount of light exiting the end of the optical waveguide.

In some aspects, a light motion sensing device may include a sensor frame defining an opening, a sensor pad disposed within the opening, a light sensing system configured to detect an amount of movement of the sensor pad within the sensor frame, and an output unit. The light sensing system includes an optical waveguide, a light source device, and a light detector. The optical waveguide is positioned within the sensor frame such that movement of the sensor pad results in bending or compression of the optical waveguide. The light source device supplies optical energy to the optical waveguide. The photo detector detects the amount of light energy exiting the optical waveguide. The output unit is configured to receive a signal indicative of an amount of light energy exiting the optical waveguide and generate a measure of the amount of movement of the sensor pad from the received signal.

In some aspects, a method of detecting a localized amount of displacement includes delivering optical energy into a first end of an optical waveguide, detecting an amount of optical energy exiting a second end of the optical waveguide, and generating a measure of the amount of downward displacement of the sensor pad based on the amount of light energy exiting the second end. The optical waveguide is positioned within a sensor frame that includes a sensor pad such that downward displacement of the sensor pad results in compression or bending of the optical waveguide. The amount of light energy exiting the optical waveguide is detected using a photodetector held by the sensor frame. The photo detector generates therefrom a signal indicative of the received light energy. A resulting measure of the amount of downward displacement of the sensor pad is generated using a signal indicative of light energy exiting the second end of the optical waveguide. The amount of light energy exiting the second end of the optical waveguide is reduced in response to downward displacement of the sensor pad.

In some aspects, an elastic waveguide for detecting arterial pulses includes a cladding having a flat surface and defining a lumen, and a core disposed within the lumen. The cladding comprises an elastomer having a Shore A hardness of 25 to 75. The core also includes an elastomer having a Shore A hardness of 25 to 75. The core has a refractive index greater than that of the cladding.

In some embodiments, the cladding can have a Shore A hardness of 45-55 and the core can have a Shore A hardness of 30-45. In some implementations, the waveguide can induce at least 10,000 modes (eg, at least 50,000 modes). In some embodiments, the core can have a refractive index of 1.43 to 1.50 (eg, 1.45 to 1.47) and the cladding can have a refractive index of 1.39 to 1.48 (eg, 1.39 to 1.41). In some implementations, the core can have a radius of at least 45 micrometers (eg, 150-200 micrometers).

In some embodiments, the optical waveguide can include an elastomer (eg, a siloxane elastomer). The elastomer may be selected from the group consisting of polysiloxanes, polyurethanes, polybutadiene rubbers, and combinations thereof.

The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects and advantages of the present invention will become apparent from the detailed description, drawings and claims.

1 shows an embodiment of a vital sign measurement device;

2A, 2B and 2C show various implementations of a vital sign measurement device positioned on the upper arm, and also show three different levels of cuff pressure versus arterial systolic blood pressure.

Fig. 3 shows a series of pulses during contraction of the cuff detected by a pressure sensor pneumatically coupled to the cuff compared to pulses obtained simultaneously detected by a light sensing system held by the sensor holding device;

Fig. 4 shows an implementation of a vital sign measurement device having a sensor holding device with an inflatable bladder;

5a, 5b and 5c show an implementation of a sensor frame comprising components of a light sensing system;

Fig. 6 shows an implementation of a light sensing system on a flexible incompressible waveguide support surface;

7A-7C show an embodiment of a light sensing system;

8a and 8b show how a compressed waveguide results in a reduction in the amount of transmitted light;

Figures 9a and 9b show how a bent waveguide results in a reduction in the amount of transmitted light;

10A-10D are cross-sectional views of different embodiments of a waveguide;

Fig. 11 shows pulsatile light transmission in a waveguide subjected to oscillatory strain due to arterial pulses;

12 depicts an implementation of an assay used to determine one or more vital signs by an output unit.

Like reference numbers in the various drawings indicate like elements.

As shown in FIG. 1 , the vital sign measurement device may include a sensor holding device 102 , a sensor frame 200 holding the light sensing system, and an output unit 106 . The output from the light sensing system in the sensor frame 200 may be used to determine, for example, a patient's blood pressure, and in particular a measure of vital signs such as systolic and diastolic measurements of the patient's blood pressure.

The sensor fixation device 102 holds the sensor frame 200 and attaches it to the patient's anatomical location 112 having an artery 118 therein. 1 , for example, the anatomical location 112 is the upper arm of a human patient. The sensor frame 200 may be positioned such that the light sensing system 104 detects movement corresponding to an arterial pulse when the sensor frame 200 is positioned relative to the patient's anatomical location 112 . In this way, the sensor fixation device 102 detects an arterial pulse with the light sensing system when the sensor fixation device 102 applies pressure on the patient's upper arm 112 that is below systolic blood pressure, but detects an arterial pulse when it is above systolic blood pressure. ) it is possible not to detect arterial pulses. Accordingly, the systolic blood pressure may be determined as the pressure applied to the anatomical location 112 when the first arterial pulse is detected by the light sensing system as the pressure decreases from the pressure above the systolic pressure. Alternatively, the systolic blood pressure may be determined as the final pressure at which the arterial pulse is observed by the light sensing system as the pressure increases to a pressure above the systolic pressure. Moreover, the vital sign measurement device may measure the relative intensity of one or more arterial pulses and/or detect a pulse waveform when the sensor fixation device applies a pressure below the systolic blood pressure of the patient's arm, from these measurements to the patient. A number of different vital sign measures can be determined, including systolic and diastolic blood pressure measurements. For example, the diastolic blood pressure may be determined based on a predetermined pulse waveform characteristic such as a ratio of pulse amplitudes and/or a shape of a pulse waveform between arterial pulses.

The optical sensing system 104 uses what may be referred to as optical power modulation to detect and measure arterial pulses. An exemplary light sensing system implementing this optical power modulation method supplies light energy to an optical waveguide 212 held by a sensor frame 200 , a first end of the optical waveguide 212 , with particular reference to FIG. 5C . a light source 202 positioned to cause the light source 202 , and a photo detector 240 positioned to detect an amount of light energy applied to a second opposite end of the optical waveguide 212 . The output unit 106 is connected for receiving a signal, such as an electrical signal, for example from a light sensing system, in particular from a photo detector 240 , for example as shown in FIG. 1 , wherein the signal is a light It indicates the amount of light at a given point in time that is applied to the second opposite end of the optical waveguide detected by the detector 240 . From the received signal, the output unit 106 generates a measure of the vital sign. The optical sensing system 104 acts on or responsive to the arterial pulse by compression or bending of at least a portion of the optical waveguide 212 of the sensing system, which reduces the amount of optical energy applied to the optical waveguide, and thus to the optical detector. resulting in a decrease in the amount of light energy received by the

By way of example, the vital signs may include heart rate, arterial pulse waveforms, systolic blood pressure measurements, diastolic blood pressure measurements, mean arterial blood pressure measurements, pulse pressure measurements, and/or measurements of arterial elasticity. In some embodiments, the vital sign may be determined from the timing of the arterial pulse, the amplitude and/or magnitude of the arterial pulse, and/or from the arterial pulse waveform. In some implementations, the vital signs may be determined from output received from the light sensing system 104 , while in other implementations the vital signs may be determined in combination with other data (eg, data regarding pressure within the pneumatic cuff). It can be determined from the output. In the former case, the heart rate may be determined from the output received from the light sensing system 104 only. Vital sign measurements of the present invention may be taken at any extremity location including, but not limited to, the upper arm, the waist region, the legs, and the toes.

<u>sensor holding device</u>

The sensor fixation device is configured to hold and position the sensor frame 200 or a portion thereof adjacent the anatomical location 112 of the patient such that the light sensing system 104 within the sensor frame 200 can detect the arterial pulse. It can be any structure that allows The sensor fixation device may hold the sensor frame 200 adjacent the patient's anatomical location 112 at a predetermined sensor fixation pressure or an adjustable sensor fixation pressure. For example, the sensor fixation device may be an adhesive band or cuff (eg, an elastic cuff or an inflatable cuff).

As shown in FIG. 4 , the sensor fixation device 102 may be an inflatable cuff 120 having an inflatable bladder 122 . For example, the sensor fixation device 102 may be an assembly comprising a cuff comprising a textile material configured to surround or circumscribe an anatomical location (eg, a limb) of a patient. The inflatable bladder 122 may be positioned within the cuff to partially enclose or enclose the limb. As such, the sensor fixation device 102 is configured to apply pressure to the limb when inflated, thereby compressing the arteries in the limb.

In general, the cuffed sensor fixation device 102 for use in the systems and methods described herein may be of a type that completely or partially encloses a limb, or may be of a specific type including the waist above the radial artery. It may also be of the type that applies pressure locally, which may be advantageous at an anatomical location. The bladder 122 in this device 102 may be pneumatically connected to the pump 124 via a hose 116 , as in the case of FIG. 4 . In some embodiments as shown in FIG. 4 , the pneumatic inflatable cuff is inflated (eg, via pump 124 ) and deflated (eg, via valve 126 ) to the patient's The pressure applied to the body part 112 may be adjusted. In some implementations, the system may include an inflation controller 452 such as included within the output unit 106 as shown in FIG. 12 to control inflation and deflation of the cuff. In other implementations, the inflation controller may be included as a separate controller unit for controlling the operation of the vital sign measurement device.

As such, various types of sensor fixation devices may be applied to various different parts of a patient's body. The sensor fixation device may be dimensioned and arranged for placement in an anatomical location of the patient's body adjacent to the patient's predetermined artery. 1 and 2A-2C , the sensor fixation device 102 is positioned on the upper arm (above the patient's elbow) so that the light sensing system in the sensor frame 200 pulses the arterial pulse in the brachial artery 118 . It is possible to detect a movement corresponding to . The sensor fixation device may also be configured for placement over the waist to enable a light sensing system within the sensor frame to sense movement corresponding to an arterial pulse within the nodule artery. The sensor fixation device may also be positioned on a leg (eg, an ankle to detect a pulse in an artery), neck, or any other part of the body where an arterial pulse may be detected.

As shown in FIGS. 2A-2C , the sensor frame 200 is on the proximal side (as shown in FIG. 2A ) relative to the midpoint of the sensor fixation device 102 . It may be located at the midpoint (as shown in FIGS. 2B and 2C ), or distal to the midpoint of the sensor fixation device 102 (not shown). The placement of the sensor frame 200 relative to the pressure-applying device, and more specifically the sensing portion (eg, sensor pad) of the sensor frame 200 may affect the data obtained. In an embodiment where the sensor fixation device 102 applies pressure to an anatomical location as shown in FIGS. 2A-2C , the location of the sensing portion of the sensing frame 200 within the sensor fixation device 102 depends on the obtained data. can affect In some embodiments, the pressure applied to an artery located below the surface of the anatomical location may be non-uniform. For example, while the pressure-applying body placement device 102 may apply a uniform pressure, the pressure delivered through a layer of tissue may result in non-uniform pressure against an artery located at a distance below the surface. In some embodiments, the pressure applied by the inflatable cuff to an artery located at a distance under the skin may be maximum at the cuff midline and small at the cuff edge. The position of the sensor frame 200 relative to the sensor fixation device 102 may be fixed to optimize sensitivity to selected characteristics of the arterial pulse. In some implementations, the sensor frame 200 and a sensing portion (eg, a sensor pad) of the sensor frame 200 are positioned at the midline 134 of the cuff, such that when the cuff pressure exceeds the systolic blood pressure, the cuff It may not respond to pulsatile dilation of the arterial segment below the proximal portion, allowing precise determination of systolic blood pressure when the middle section of the arterial segment is opened.

In other implementations not shown, the sensor frame 200 and a sensing portion (eg, a sensor pad) of the sensor frame 200 are positioned adjacent to the distal edge of the cuff, particularly the pulsation at that location. It can respond to changes in arterial dimensions. Thus, a unique characteristic of the arterial pulse waveform in diastolic blood pressure at the distal location can be identified, and the effect of arterial elasticity in the more distal artery can be detected. Outward flexion of the skin at the midline 134 of the cuff and also distal to the midline 134 occurs during systolic pressure when the cuff pressure is below systolic blood pressure. At cuff pressures above systolic blood pressure, arterial oscillations are limited to the proximal region of the cuff as described above.

In some implementations not shown, the device can include a second pressure applying device separate from the sensor holding device holding the sensor frame with the light sensing system. The second pressure applying device is disposed relative to the second anatomical location of the patient at a proximal to the anatomical location of the sensor fixation device to enable detection of an arterial pulse by the light sensing system at a location distal to and separate from the pressure applying device. can be configured to allow. Accordingly, the light sensing system may detect the arterial pulse waveform at a location distal to and spaced from the point of arterial occlusion, thus allowing detection of unique features of the arterial waveform. The second pressure applying device may be an inflatable cuff. In some implementations, both the pressure applying device and the second fixation device can be an inflatable cuff.

2A shows a second fixation device 102 imparting to the arm a pressure in excess of the arterial systolic blood pressure of the brachial artery sufficient to create a minimal arterial opening below the leading edge of the second fixation device 102 upon contraction of the heart. is showing The amount of pressure applied to the second fixation device 102 will pulsate slightly due to arterial dilatation at the leading edge during the arterial pulse. No arterial patency occurs upon positioning of the sensor frame 200 , and thus the light sensing system 104 within the sensor frame 200 does not generate a pulsatile signal. However, the pulsatile signal is more pronounced when the sensor frame 200 is positioned at a position proximal to the midline of the sensor fixation device 102 than when the sensor frame is positioned in the middle of the sensor fixation device 102 . It will generate high pressure.

FIG. 2B shows the sensor fixation device 102 , which applies a pressure that slightly exceeds the arterial systolic blood pressure, such that the arterial opening 118 expands almost to the midline of the sensor fixation device 102 upon cardiac contraction. The oscillation of the pressure imparted to the sensor fixation device 102 during the arterial pulse pressure will be much greater than in the case of FIG. 2A as the arterial dilation occurs over nearly half of the segment positioned within the sensor fixation device. Nevertheless, no arterial patency occurs at the midline of the sensor fixation device 102 , and thus the light sensing system 104 in the sensor frame 200 does not generate a pulsatile signal.

FIG. 2C shows the sensor fixation device 102 , which applies a pressure below arterial systolic blood pressure, causing the entire arterial segment 118 to momentarily open upon systole. The oscillations of the pressure applied to the sensor fixation device 102 during the arterial pulse will be much larger in amplitude. Arterial opening at a location below the sensor frame 200 allows the light sensing system 104 to record a pulsatile signal.

The upper portion of Figure 3 shows the sensor immobilization device applied by a series of arterial pulses when the pressure exerted by the sensor immobilization device 102 is reduced from a pressure above the patient's systolic blood pressure to a pressure below the patient's diastolic blood pressure ( 102) is shown in the sensed pressure pulse. The lower portion of FIG. 3 shows the light with the sensor frame at the midline of the sensor fixation device 102 when the pressure exerted by the sensor fixation device is reduced from a pressure above the patient's systolic blood pressure to a pressure below the patient's diastolic blood pressure. The pulses determined from the sensing system are shown. As shown, the light sensing system within the sensor frame does not detect any pulses until the applied pressure is below systolic blood pressure. This may allow an accurate determination of systolic blood pressure, and the waveform detected by the light sensing system may allow calculation of other vital signs.

4 shows an embodiment of a sensor holding device 102 . The sensor fixation device may be an inflatable cuff 120 having an inflatable bladder 122 . The cuff may comprise a textile material configured to surround a limb of a patient. The inflatable bladder 122 may enclose a limb partially, but not completely, and may be configured to apply pressure to the limb when inflated, thereby compressing arteries within the limb. The inflatable cuff 120 may be wound around the patient's upper arm and configured to hold the sensor frame 200 in place to apply the same pressure to the extremities. A light sensing system may be positioned within the sensor frame 200 to detect arterial pulses from the brachial artery. The cuff 120 includes a hook and loop fastener 132 (eg, Velcro) that may be used to secure the cuff 120 around a patient's limb.<img file="KR20090115744A_D0001.tif" />] or other fastening devices. The cuff 120 may be wrapped around the patient's limb, and the bladder 122 may be inflated to apply pressure to the limb. The bladder 122 may be connected to the pump 124 by a hose 116 . The bladder 122 may also be attached to a valve 126 that may control retraction of the bladder 122 . The pressure in the bladder 122 may be measured with a pressure transducer 128 . Pressure transducer 128 may be positioned within the bladder as shown, or may be pneumatically coupled to bladder 122 (eg, via hose 116 ).

The components of the light sensing system may be packaged within a sensor frame 200 (eg, a housing) located at a midpoint 134 of the cuff 120 . The sensor frame 200 may be attached to the cuff at locations that do not coincide with portions of the bladder. The sensor frame 200 can be positioned oppositely on the cuff so that when the inflatable bladder 122 is inflated the pressure applied to the extremity by the sensor frame is substantially equal to the pressure applied to the extremity by the surrounding cuff fabric. have. For example, the upper surface of the sensor frame 200 may be approximately the same height as the inner surface of the cuff. The sensor frame 200 may be positioned on the cuff 120 to enable the light sensing system 104 to detect pulses in the artery as the cuff 120 is wrapped around an anatomical location of the patient.

<u>output unit</u>

4 and 12 , the output unit represents the amount of light energy (eg, light) exiting the second end of the optical waveguide, and thus the signal detected by the photodetector 240 ( for example, an electrical signal). These signals may be transmitted via electrical wires 108 . In some implementations, the output unit 106 may also receive other data. For example, as shown in FIG. 4 , the wire 108 transmits data in the form of a signal (eg, an electrical signal) from the pressure transducer in the bladder 122 to the output unit 106 to the output unit. (106) may allow determining the amount of pressure applied to the anatomical location of the patient. In some implementations, the output unit 106 may receive data regarding the amount of light energy received by the photo detector from the photo sensing system via wireless transmission.

1 , 4 and 12 , the vital sign measurement device may include a display unit 114 that displays one or more vital signs (eg, heart rate, systolic blood pressure, and diastolic blood pressure). As shown in FIG. 4 , the output unit 106 may be packaged into a display unit 114 . In some implementations not shown, the output unit may be within the sensor frame, within another portion of the cuff assembly, and may be remotely located in communication with the light sensing system via wireless transmission. The wire may transmit data from the output unit 106 to the display device 114 (eg, via an electrical signal). In another implementation, the output unit 106 may transmit vital sign measurements via wireless transmission.

In some implementations, the output unit may include an alert system that generates a human detectable signal when the vital sign measurement generated by the output unit meets a predetermined criterion. For example, the output unit may be configured to generate a visual or audible alert to alert the user that the detected vital sign is outside a predetermined range.

The output unit 106 may perform a number of data processing steps, calculations or evaluation functions, some of which are described below. The output unit 106 is capable of extracting life from the signal from the light sensing system with or without other data (eg, data regarding the pressure applied to the anatomical location by the inflatable cuff as shown in FIG. 4 ). A processor for determining the indication may be included.

<u>sensor frame</u>

5A , 5B and 5C , the light sensing system 104 may be contained within a sensing frame 200 (eg, a housing). The function of the sensor frame 200 is to maintain pressure against the skin and to deliver mechanical impulses of arterial pulses to the light sensing system 104 without delivering pneumatic cuff pressure pulses. The function of the light sensing system 104 is to generate a signal indicative of an arterial pulse.

The sensor frame 200 may be positioned relative to the anatomical location (eg, against the patient's skin) to sense an arterial pulse by movement of a sensor pad 232 , which may be positioned adjacent to the anatomical location. . The sensor pad 232 may be configured to move as a result of the increased contact pressure generated by the expansion of the bladder. Movement of the sensor pad 232 may result in compression or bending of the optical waveguide 212 . The sensor frame 200 may also include a load spring 234 attached to the sensor pad 232 to counteract the force applied to the sensor pad 232 by the patient's anatomical location. The load spring 234 may also be attached to at least a portion of the sensor frame 200 . The sensor frame 200 holds the optical waveguide 212 against a force applied to the optical waveguide 212 by a sensor pad 232 and/or a flexible and incompressible waveguide support surface 233 upon which the waveguide rests. a structure for supporting the waveguide, such as a waveguide support structure 235 for supporting it. The sensor frame 200 may also include a wire 108 that transmits data from the photo detector 240 to the output unit 106 . In some implementations not shown, the sensor frame 200 may include an output unit, and may include wires that transmit data from the output unit to an external source (eg, a display). In some implementations, the sensor frame 200 is 0.7 to 1.3 inches (17.8 to 33.0 mm) (eg, about 1 inch (25.4 mm)) wide, 1.5 to 2.2 inches (38.1 to 55.9 mm) [eg, For example, it may have a length of about 1.7 inches (43.2 mm), and a thickness of 0.3 to 0.9 inches (7.6 to 22.9 mm) (eg, about 0.6 inches (15.2 mm)).

As shown in FIGS. 5A , 5B and 5C , a sensor pad 232 configured to be positioned relative to a patient's anatomical location may be attached to the load spring 234 . The sensor pad 232 may extend to the outside of the sensor frame 200 when it is in a relaxed state. For example, the sensor pad 232 may extend outside of the sensor frame 200 by at least 0.1 inches (2.54 mm) (eg, 0.1 to 0.3 inches (2.54 to 7.6 mm)). As shown, the sensor pad 232 extends from the sensor housing 200 by 0.161 inches (4.1 mm). The sensor pad 232 may have any shape. The sensor pad 232 may have a diameter of at least 0.3 inches (7.6 mm), such as 0.3 to 0.8 inches (7.6 mm to 20.3 mm) (eg, about 0.6 inches (15.2 mm)). In some implementations, for example, as shown in FIG. 5C , the sensor pad 232 may be attached to the spring 234 by a hinge 236 that allows for forward and backward motion of the sensor pad 232 . In some implementations, as shown in FIG. 5C , the sensor pad 232 may have a beveled top surface. The sensor pad 232 may be attached or otherwise positioned to cause compression or bending of the optical waveguide of the light sensing system 104 . As shown in FIG. 5C , the sensor pad 232 may include a pressing portion 238 configured to generate localized compression of the optical waveguide 212 . A sensor pad 232 may also be positioned within a cutout 252 . The spacing between the cutout 252 and the sensor pad 232 may affect the amount of movement of the sensor pad 232 allowed by the sensor housing 200 due to the arterial pulse. The spacing between the cutout 252 and the sensor pad 232 may be about 0.1 inches (2.54 mm).

Wire 108 may transmit data from photo detector 240 to output unit 106 as described above. In some implementations not shown, the output unit may be contained within the sensor frame, and the wire may transmit vital sign data to a device external to the housing. In some implementations not shown, the light sensing system 104 may transmit data from the sensor frame 200 by wireless transmission.

The load spring 234 may counteract the force applied to the sensor pad 232 from the arterial pulse and return the sensor pad to its initial state after the arterial pulse. Thus, the load spring 234 may limit the amount of compressive and flexural deformation of the waveguide due to the arterial pulse. The load spring 234 may be selected such that the light transmission factor is most sensitive to waveguide deformation within the useful range of cuff pressure. The combination of the load spring 234 with the sensor frame 200 and other features of the light sensing system 104 may provide a reaction force such that an applied pressure of 150 mmHg displaces the sensor pad by at least 1 mm from the resting state. will do In some implementations, the sensor frame 200 and light sensing system 104 may be configured such that an applied pressure of 150 mmHg will displace the sensor pad by at least 2 mm from the resting state. In some implementations, the load spring 234 may be configured to provide a maximum displacement of the sensor pad of 0.5 to 3 millimeters at maximum pressure (eg, 0.8 to 1.5 millimeters at maximum pressure). In some implementations, the sensor frame 200 and the light sensing system 104 are at a height such that an applied pressure of 80 to 150 mmHg (eg, 100 to 130 mmHg) is approximately equal to the top surface of the sensor frame 200 . and may be configured to provide an upper surface of the sensor pad on the . In some implementations, the sensor pad 232 is the sensor frame 200 when positioned relative to the anatomical location of the patient by the occlusion device 102 with the occlusion device providing pressure in excess of the systolic blood pressure to the anatomical location. ) can be at about the same height as In some implementations, the upper surface of the sensor frame 200 may be approximately flush with the inner surface of the sensor fixation device (eg, an inflatable cuff).

The sensor frame 200 includes a flexible and incompressible waveguide support surface 233 and/or an inelastic waveguide support structure that supports the waveguide 212 of the light sensing system 104 against a force applied by the sensor pad 232 . 235) may also include a waveguide support structure. The waveguide support surface 233 may have a flexible and incompressible support surface and may extend along the entire length of the optical waveguide 212 . In some implementations, as shown in FIG. 6 , the waveguide support 233 can have a support return element 237 configured within the support surface and configured to oppose the curvature of the support surface. For example, the support return element 237 in the waveguide support 233 may be a member having a high memory, such as a steel spring, capable of returning the waveguide to its undeformed position after each pulsating deformation. The support return element 237 may be configured to provide an increasing contact pressure between the sensor pad and the optical waveguide as the sensor pad moves from the rest position to the maximum displacement position, the optical waveguide such that the increasing contact pressure is applied to the optical waveguide. is configured to generate a decreasing amount of light exiting the In some implementations, the support return element 237 may act in conjunction with the load spring 234 to achieve increasing contact pressure. In some implementations, the waveguide support surface 233 may be a flexible electronic circuit board to which the waveguide is bonded with a flexible elastomeric adhesive. As shown in FIG. 6 , the waveguide support surface 233 may also support and support the light source 202 and/or the light detector 240 . In some implementations, other associated electronic components may be mounted on the waveguide support surface 233 .

The waveguide support structure 235 is inelastic. In some implementations, as shown in FIG. 7A , the waveguide support structure 235 supports the portion of the waveguide 212 that is acted upon by the sensor pad 232 (eg, substantially over its entire length). can support Accordingly, the waveguide 212 may be compressed between the waveguide support 235 and the pressing portion 238 . 8A and 8B described below illustrate how compression of the waveguide 212 can result in a reduction in the amount of light delivered to the photodetector 240 . In other implementations, as shown in FIGS. 7B and 7C , the waveguide support structure 235 can support a portion of the waveguide that is spaced apart from the portion of the waveguide that is acted upon by the sensor pad 232 . In other implementations, movement of the sensor pad 232 may result in bending of the waveguide 212 . 7B shows an embodiment where the sensor pad acts directly on the waveguide resulting in bending of the optical waveguide 212 . 7C shows an embodiment in which the pressurizing portion 238 presses against a localized portion of the waveguide. This may result in some compression in combination with some bending of the waveguide in the adjacent region. 9A and 9B, described below, illustrate how bending of the waveguide 212 can result in a reduction in the amount of light delivered to the photodetector 240 .

The light sensing system 104 within the sensor frame 200 may act as a motion sensing system (eg, a motion sensing system configured to detect localized motion associated with an arterial pulse). The light sensing system 104 within the sensor frame 200 may detect motion corresponding to an arterial pulse rather than just the pressure applied to the sensor pad 232 when the sensor fixation device is positioned relative to the patient's anatomical location. For example, a surface pressure sensor (eg, a piezoelectric pressure sensor) may detect a change in pressure due to an arterial pulse even when the pressure applied to the anatomical location by the occlusion device 102 exceeds the systolic blood pressure. can At high cuff pressure (above systolic blood pressure), the artery proximal to the occlusion device 102 (e.g., an inflatable cuff) can impart a pulsating impulse to an anatomical location that passes through the tissue, This causes a pulsating pressure increase in the occlusion device 102 . This effect causes a pulsatile tension in the occlusion device 102, which is intrinsically "incompressible" and the artery is continuously occluded within the region below the pressure sensor, even if there is no cuff contraction. will be detected by a surface pressure sensor attached to the inner surface of the The positive signal of the pressure applied by the occlusion device (i.e. cuff bladder pressure sensor) and the surface pressure sensor indicates that the effect of the opening of the artery causing blood flow to occur is less than the effect of the pulsating impulse on the cuff as described above. Therefore, it may similarly be higher and lower than systolic blood pressure. In contrast, a light sensing system within the sensor frame acting as a motion sensor may have little response due to cuff tension at high cuff pressures and may prevent detection of motion during arterial pulses at pressures above systolic blood pressure. . Thus, the use of a light sensing system in the sensor frame as a motion sensor can indicate systolic blood pressure more accurately than a pressure sensor. Moreover, no individual accurate blood pressure measurement is required for calibration or establishment of baseline.

optical power<u> Light sensing system using modulation</u>

5C , 6 and 7A-7C , the light sensing system 104 may include a light source 202 , an optical waveguide 212 , and a photo detector 240 . As described above, the light sensing system 104 may be held by a sensor frame 200 (eg, a housing) held by the sensor holding device 102 . The light source 202 may be optically coupled to the optical waveguide 212 , such that light energy (eg, light wave 218 ) may travel from the light source 202 into a first end of the optical waveguide 212 . . In some implementations, an LED may be used as the light source 202 . The photodetector 240 may receive light energy indicative of an opposing second end of the optical waveguide 212 and generate a signal indicative of the amount of light received. In some implementations, the light detector 240 receives substantially all of the light representing the second end of the optical waveguide 212 . In some implementations, the photodetector 240 may be a PIN diode photodetector, a CCD (charge coupled device) detector, or a CMOS (tribotype metal oxide semiconductor) detector.

<u>optical waveguide</u>

The optical waveguide 212 may be an optical fiber or any liquid, gel, or solid that transmits light waves by internal reflection or refraction. The optical waveguide 212 may comprise an elongate optically transparent material, generally referred to as a "core" 215 , surrounded by a low index material, generally referred to as a "cladding" 217 . The core 215 has a low refractive index (N) of the cladding 217 .<sb>1</sb>) for a relatively high refractive index (N<sb>2</sb>) can have The difference between the core and cladding refractive indices defines the numerical aperture (NA) of the waveguide according to the following relationship.

<img file="KR20090115744A_D0002.tif" />

The NA of the waveguide and the critical angle θc govern the confinement of light within the core of the waveguide. If the angle of incidence of the ray at the core/cladding interface with respect to the vector perpendicular to the interface is less than the critical angle θc, the ray will not be internally reflected and will escape the core and be lost. N<sb>2</sb>go N<sb>1</sb>very close to (ie, NA0), the critical angle will reach 90 degrees, and almost all the light will escape within the short length of the waveguide. N<sb>2</sb> and N<sb>1</sb>With these sufficiently different values, most of the light will remain confined. Light energy (eg, light) is lost from the optical waveguide when the light wave reaches the interface between the two materials (core 215 and cladding 217 ) at an angle less than the critical angle θc. The critical angle θc may be calculated by the following equation.

<img file="KR20090115744A_D0003.tif" />

Another characteristic of an optical fiber or optical waveguide is the number of excitable modes. In optical waveguides, the term "mode" refers to a specific intensity pattern in a plane transverse to the optical waveguide axis. There is a close relationship between the internal mode pattern of the optical fiber and the external speckle pattern. In single mode fiber, only one intensity peak is allowed. In multimode fiber, multiple intensity peaks can occur at any location along the waveguide. In any waveguide with a circular cross section, a "zero order" mode is formed by light propagating along the waveguide axis (assuming a perfectly straight waveguide). The so-called "higher order" mode is formed by light that is not transmitted axially but is transmitted at an angle to the axis. These modes are driven by the refractive index difference between the core and the cladding, each of which will generally have a lower intensity than in the zero order mode. When the step index waveguide is bent at a given location, the lower order and zero order modes become higher order modes because they no longer reside at or near the centerline. In order for light to occupy a higher order mode within the waveguide, the light source must be partially composed of rays at a non-zero angle to the axis (but still within the numerical aperture of the waveguide), or otherwise the waveguide must be wound or bent. In general, a few higher order modes may exist in a waveguide illuminated by a collimated light source, and conversely a number of higher order modes will exist in a waveguide illuminated by a diverged light source.

As can be seen in Figures 8a, 8b, 9a and 9b, compression and/or bending of the waveguide preferably eliminates higher order modes and has relatively little effect on lower order modes. The sensitivity of an optical system to small compressions and/or small amounts of bending depends on the availability of a sufficient number of excited waveguide modes. For example, in the case of only five excited modes, theoretically only five different levels of optical power transfer loss can be detected, which is a relatively rough estimate between the amount of light detected by the photodetector of the photo-sensing system and the strain. will create a relationship. On the other hand, if there are 10,000 excited modes, the relationship between the strain and the detected light energy can be determined much more finely, and a relatively small strain change can be detected. Thus, in some implementations, the light source can provide a branched beam of NA that is approximately equal to or greater than the NA of the waveguide. If the light source NA is greater than the waveguide NA, the result is that the portion of the emitted light at the angle of the maximum axis immediately escapes into the cladding. The optical waveguide may also be formed to be capable of conducting at least 10,000 modes (eg, more than 50,000 modes). The number of possible modes in a stepped refractive index waveguide is given by the equation

<img file="KR20090115744A_D0004.tif" />

Here, V is the normalized frequency. The normalized frequency V is calculated as follows.

<img file="KR20090115744A_D0005.tif" />

where a is the radius of the core of the optical waveguide, NA is the numerical aperture of the waveguide as described above, and λ is the wavelength of light. The most practical light sources have a wavelength (λ) between 0.7 and 0.85 micrometers. Therefore, the product of a and NA must be on the order of 40 micrometers to satisfy the criterion for 50,000 modes. A practical range for NA is approximately 0.2 to 0.4. Thus, a waveguide with a NA of 0.4 would need to have a minimum core radius of 100 micrometers to allow for 50,000 modes and a minimum radius of about 45 micrometers to allow for 10,000 modes. In some implementations, the waveguide core 215 has a radius of at least 45 micrometers (eg, 150-200 micrometers). The optimal size also depends, in part, on the actual strain experienced by the waveguide (which in turn depends on the waveguide hardness, the mechanical pressure actually applied to the waveguide and the amount of bending of the waveguide). In some embodiments, the waveguide may have a Shore A hardness between 45 and 55, a NA of 0.35 to 0.4 (corresponding to a core refractive index of 1.46 and a cladding refractive index of 1.41) and a core radius of 150 to 200 microns. This design has a transmission loss of 5 to 70% of the short length (2 to 4 cm) of the waveguide when the flexural strain is 5 to 20 degrees over a length of 1 to 2 cm and/or when the core is compressed by 5 to 50%. can create

NAs of 0.2 to 0.4 can be achieved by having a refractive index difference between the core and cladding of 2 to 4% in common optical grade materials. In light transmission applications, light is introduced into one end of a waveguide. If the waveguide were straight, total internal reflection would result in the confinement of all input light within the NA of the waveguide, and the loss of light would be minimal. If the waveguide is not straight but has a certain curvature, some of the light will experience total internal reflection until it reaches the bend, where it reaches the core/cladding interface below the critical angle θc and escapes into the cladding. Similarly, if the waveguide is compressed, some of the light will experience total internal reflection until it reaches the compressed region, where it reaches the core/cladding interface below the critical angle θc and escapes into the cladding. The variable transmission loss due to pulsatile curvature or compression can be measured with a photodetector 240 (eg, a photosensor) in the optical waveguide and used to characterize the pulsating force acting on the waveguide.

As shown in FIGS. 8A , 8B , 9A and 9B , the optical waveguide 212 generates internal reflection of the optical wave 218 within the core of the optical waveguide 212 . However, the compression or bending of the optical waveguide 212 (as shown in FIG. 8B ) or bending (as shown in FIG. 9B ) is an angle at which the compression or bending of the optical waveguide 212 is less than the critical angle θc. This results in a loss of light energy as it results in an additional light wave (such as light wave 263 ) that causes it to reach the interface between the furnace core 215 and the cladding 217 . As shown in FIGS. 8A and 8B , the compression of the optical waveguide 212 results in a decrease in the transmitted optical energy 261 due to the lost optical energy 263 . As shown in FIGS. 9A and 9B , bending of optical waveguide 212 results in a decrease in transmitted optical energy 261 due to lost optical energy 263 .

Optical waveguide 212 may be flexible and/or incompressible. In some embodiments, the optical waveguide 212 may include an elastomer. For example, the core 215 , the cladding 217 , or a combination thereof may include an elastomer. Ordinary glass and plastic optical fibers exhibit bending losses, but generally cannot be deformed to a significant extent by mechanical compression. However, elastic waveguides can be fabricated using softer materials. In contrast to glass waveguides, these elastic waveguides can be easily deformed by a small compressive force. Examples of suitable elastomers include polysiloxanes, polyurethanes, and polybutadiene rubbers. In some embodiments, both the core 215 and the cladding 217 include a siloxane elastomer. For example, the optical waveguide may have a cladding 217 comprised of a silicone elastomer and a core 215 comprised of a second silicone elastomer of a different refractive index. In some embodiments, the cladding elastomer can be a material that does not inhibit curing of the core material. For example, the cladding elastomer may have an additional curing chemistry and the core elastomer may have a platinum curing chemistry.

The cladding 217 may have an optically transparent or translucent appearance. The core 215 may be optically transparent. In some embodiments, the cladding can have a refractive index of 1.39 to 1.48 (eg, 1.39 to 1.41). In some implementations, the core 215 may have a refractive index of 1.43 to 1.50 (eg, 1.45 to 1.47). The cladding may have a Shore A hardness of 25 to 75 (eg, 45 to 55). Core 215 may have a Shore A hardness of 25-75 (eg, 30-45).

The optical waveguide 212 may have a number of shapes. As shown in FIG. 10A , the cladding 217 may have a circular cross-sectional shape. In some implementations, the cladding may serve as an adhesive bonding surface for adhesion of the optical waveguide 212 to a flexible surface, such as a flexible circuit board used to support the optical waveguide in a light sensing system, for example. It may have a flat extended support surface along its length. For example, the flat extended support surface may be bonded to the waveguide support surface by a flexible elastomeric adhesive. 10B-10D show cross-sections of an example of an optical waveguide 212 having a flat expanded support surface 271 .

The cladding 217 of the optical waveguide 212 may be formed by an extrusion process. In some implementations, the core 215 and the cladding 217 may be formed in a coextrusion process. In some implementations, the cladding 217 may be extruded in a first process to create a uniform cross-sectional shape forming a hollow lumen. The core 215 may then be formed by filling the lumen of the cladding 217 with a core material. For example, the extrusion process can be used to form any of the cladding cross-sectional shapes shown in FIGS. 10A-10D . In some implementations, the position of the core centerline is set to match the position of the exit beam of the light source 202 after the light source 202 and the optical waveguide 212 are mounted on the flexible waveguide support 235 , such that the light source may facilitate easy optical alignment of the optical waveguide 212 with respect to 202 .

<u>method</u>

The photo detector 240 of the photo sensing system 104 may generate an electrical signal 420 indicative of the amount of light received. Electrical signal 420 may be a function of time. Electrical photodetector signal 420 is analyzed to determine a number of vital signs. The output unit 106 may determine the amplitude and/or magnitude of each arterial pulse to determine one or more vital signs. In some embodiments, amplitudes and/or magnitudes for a series of arterial pulses may be determined to determine one or more vital signs. In some implementations, the time interval between pulses may be measured during a series of detected arterial pulses and used to determine heart rate. For example, FIG. 11 illustrates pulsatile light propagation in a waveguide that is subjected to oscillatory strain due to arterial pulses. Some vital sign measurements, such as heart rate, do not require input regarding the pressure applied to the anatomical location by, for example, a pneumatic cuff.

Blood pressure can be measured, for example, by placing the cuff on the patient's arm (eg, as shown in FIG. 4 ), inflating the cuff to a pressure at least 10 mmHg above the patient's systolic blood pressure, and at least 10 mmHg above the diastolic blood pressure. Gradually deflate the cuff pressure to a lower pressure, record the arterial pulse waveform generated by the light sensing system 104, analyze the waveform to determine one or more characteristics corresponding to systolic blood pressure, and further analyze the waveform to determine diastolic It can be measured by determining one or more characteristics corresponding to blood pressure, fully deflating the cuff, and indicating systolic and diastolic blood pressure. In some embodiments, waveforms may be recorded during both inflation and deflation of the cuff, and both waveforms may be used to determine systolic and/or diastolic blood pressure.

By observing the arterial waveform formed through this process, various vital signs such as systolic blood pressure, diastolic blood pressure and mean arterial blood pressure can be determined and/or assessed. In some embodiments, the method of measuring blood pressure comprises analyzing an arterial pulse waveform by measuring the amplitude of a sequence of waveforms recorded during cuff deflation, wherein the pulse waveform amplitude is the waveform amplitude of a preceding pulse occurring at a higher cuff pressure during cuff deflation. determining a slightly higher cuff pressure, and expressing that pressure as systolic blood pressure.

The systolic blood pressure may be determined in a number of ways based on data received from the optical system 104 and from data from the sensor fixation device 102 . In some implementations, the systolic blood pressure may be determined at a cuff pressure where the pulse waveform amplitude is slightly lower than the waveform amplitude of a preceding pulse occurring at a lower cuff pressure during inflation of the cuff. In some implementations, the diastolic blood pressure may be determined during contraction of the cuff at cuff pressure where the pulse waveform indicates a pulsatile action of the arterial segment below the sensor. More specifically, diastolic blood pressure can be determined if the pulse waveform first indicates that the artery is not completely occluded at any time during the cardiac cycle. Different methods of waveform analysis are also possible. The patient's systolic blood pressure may also be continuously monitored by measuring the baseline systolic blood pressure by one of the methods described above, then compressing the cuff to a constant pressure, and then continuously monitoring the waveform. The continuous pressure may be determined by a pre-measured blood pressure reading (eg, peak arterial pressure). Next, the first measured arterial pulse amplitude may be used as a reference pulse amplitude, and subsequent pulse amplitudes may be compared with this reference pulse amplitude to evaluate changes in blood pressure. In some implementations, a pulse waveform shape can be determined for a pulse while the cuff is held at a constant pressure. This waveform shape can be measured continuously and used to monitor changes in blood pressure relative to baseline values.

In some implementations, such as that shown in FIG. 12 , the output unit 106 may determine a vital sign by one or more of the techniques described above. For example, the output unit 106 may determine the amplitude, magnitude, and/or waveform of one or more arterial pulses within the waveform generator 436 . In some implementations, the output unit 106 is configured to be configured based on a determined amplitude, magnitude, and/or waveform and a pressure applied to the patient that may be detected (eg, a pressure detected within the inflatable cuff by a pressure sensor). and a systolic blood pressure calculator 442 for determining a systolic blood pressure for the patient. In some implementations, the output unit 106 has a determined amplitude, magnitude, and/or waveform and a pressure applied to the patient that can be detected (eg, the pressure detected within the inflatable cuff by the pressure sensor 128 ). and a diastolic blood pressure calculator 444 for determining a diastolic blood pressure for the patient based on the In some implementations, heart rate calculator 446 can determine a heart rate from a determined arterial pulse waveform from an optical signal or from pressure detected within the inflatable cuff by pressure sensor 128 .

The output unit 106 shown in FIG. 12 also includes a pressure sensor 128 pneumatically connected to the bladder in the cuff, which converts data regarding the pressure in the cuff as a function of time to an analog-to-digital converter 435 . send to In some implementations, the output unit 106 can generate a pulse waveform as a function of cuff pressure. The output unit 106 shown in FIG. 12 also includes an inflation controller 452, which may control the means for inflation and deflation of the cuff to control operation of the device. In some implementations, the output unit 106 may dynamically adjust the inflation and deflation of the cuff based on the detected arterial pulse characteristics.

A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the present invention. Accordingly, other implementations are within the scope of the following claims.