Optical power modulation

ES 2 396 258 T3

DESCRIPTION

Optical power modulation

Technical field

This invention relates to the detection of vital signs, and more particularly to a device for measuring vital signs.

Background

Blood pressure refers to the force exerted by circulating blood on the walls of blood vessels and is one of the main vital signs. Systolic pressure is the peak pressure in the arteries, which occurs near the start of the cardiac cycle. Diastolic pressure is the lowest pressure in the cardiac cycle. The average pressure throughout the cardiac cycle is reported as the mean arterial pressure. Differential pressure reflects the difference between the maximum and minimum measured pressures.

Blood pressures can be measured invasively (by penetrating the skin and measuring inside the blood vessels) or non-invasively. The first is usually restricted to a hospital setting. Non-invasive auscultatory and oscillometric methods are simpler and faster than invasive methods, have fewer complications, and are less unpleasant and painful for the patient. Non-invasive measurement methods are most commonly used for routine examinations and monitoring.

The auscultation method usually uses a stethoscope and a sphygmomanometer. 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 manometer or aneroid manometer. The mercury manometer measures the height of a column of mercury, providing an absolute cuff pressure measurement without the need for calibration and therefore is not subject to errors or deviations from the calibration that affects other gauges. The cuff is inflated manually by repeatedly squeezing a rubber bulb until the brachial artery is completely occluded. While listening with the stethoscope over the brachial artery distal to the pressure cuff, the examiner slowly releases pressure on the cuff. When blood begins to flow only in the artery, the turbulent flow creates a “hiss” or pulsating noise (first Korotkoff noise). The pressure heard in this first sound is the systolic blood pressure. The cuff pressure is released until the noise (fifth Korotkoff noise) is heard, at diastolic blood pressure.

Oscilometric methods are sometimes used for continuous monitoring and sometimes for a single measurement. The equipment is functionally similar to that of the auscultation method but is not based on the use of a stethoscope and the examiner's ear. Instead, the sensing means is a pressure sensor that is pneumatically connected to the cuff and records the (relatively small) oscillations in cuff pressure that are synchronous with the blood pressure waveform. The first oscillation in cuff pressure does not occur at systolic pressure, but at cuff pressure substantially above systolic pressure. The cuff is initially inflated to a pressure in excess of systolic blood pressure. The cuff pressure is then gradually reduced. The systolic and diastolic pressure values ​​are calculated from the different amplitudes of oscillation that occur at various cuff pressures using an algorithm. The algorithms used to calculate systolic and diastolic pressures often use experimentally derived coefficients intended to match oscillometric results with results obtained using the auscultation method, as well as possible.

Hong et al. has presented in "Fiber-optic transducer for blood pressure measurements", published in the Proceedings of the 10^to lEEE International Conference on Engineering Medicine & Biology Society, pages 810 and 811A, 1988, a new type of fiber optic pressure transducer for biomedical application. It consists of two parts: a pressure sensing membrane and a fiber optic displacement transducer that relies on the loss of light intensity caused by angular misalignment between two fibers. The change in light intensity is recorded by a photodiode. The pressure transducer is recorded by a photodiode. The pressure transducer has been evaluated for static and dynamic pressure measurements. Not only does it have the proper linearity and frequency response, safety, and small size, but it can also be an attractive device for the development of multi-site pressure sensing catheters. Another prior art device is known from

Gagnadre, Electronic letters, 15.10.1998, vol. 34, No. 21.

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Summary

The present invention relates to an optical motion detection device according to claim 1. Preferred embodiments are described in dependent claims 2 to 15.

In some aspects, a device for measuring vital signs includes a sensor fixture, a sensor frame supported by the sensor fixture, an optical detection system supported by the sensor frame, and an output unit. The sensor attachment device is adapted to be positioned against an anatomical location of a subject, within which there is an artery. The optical detection system includes an optical waveguide, an optical source device for supplying optical energy to the optical waveguide, and an optical detector for detecting an amount of optical energy exiting the optical waveguide. The optical sensing system is adapted to detect an arterial pulse from compression or bending of at least a portion of the optical waveguide, resulting in the reduction of the amount of optical energy exiting the second end of the the optical waveguide. The output unit is configured to receive a signal indicating the amount of light exiting the optical waveguide and generates a vital signs measurement based on at least part of the received signal.

The device for measuring vital signs operates on the principle of optical power modulation, namely that an arterial pulse can cause bending or compression of an optical waveguide to result in a change in an amount of optical energy transmitted to the second end. optical waveguide. By monitoring the amount of light coming out of the second end of the optical waveguide, data regarding the arterial pulse can be obtained and used to determine various vital signs. The optical detection system can be configured to detect optical signals representative of a series of arterial pulses and the output unit can be adapted to determine a pulse waveform for each of the series of arterial pulses based on the amount of optical energy exiting the second end of the optical waveguide. The optical sensing system can be adapted to detect the pulsatile opening of the artery by compressing and bending the understandable optical waveguide resulting in a pulsatile reduction in a detected amount of light. The optical detector can be optically coupled to the optical waveguide such that the optical detector receives substantially all of the optical energy from the optical source that does not escape from the sides of the optical waveguide. The optical source can include a coherent light source.

In some implementations, the sensor attachment device can be a cuff that includes an inflatable bladder within the cuff. The inflatable bladder can partially surround the limb. The cuff can be made of a cloth material. The cuff can be adapted to apply pressure to the anatomical location and thus compresses an artery within the anatomical location. For example, the cuff can apply pressure when the inflatable bladder is inflated. The sensor frame can be attached to the cuff in a location that is not coincident with any part of the bladder. The sensor frame can be held in opposition to the limb by adhering it 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.

The device includes a sensor pad within the sensor frame, which can be located adjacent to the anatomical location. The sensor pad can be configured such that it moves as a result of increased contact pressure caused by inflation of the bladder. Movement of the sensor pad results in compression or bending of the optical waveguide. In some implementations, the sensor pad can be located at a midpoint of the sensor attachment. In other implementations, the sensor pad can be located at a distal location of the sensor attachment. In some implementations, the sensor pad can be configured such that pulsatile tensioning of the sensor fixation device does not produce pulsatile movement of the sensor pad, while pulsatile opening of the artery within the anatomical location produces movement. pulsating sensor pad. In some implementations, a maximum contact pressure applied to the sensor pad can cause a 20-80% reduction (for example, a 50-70% reduction) in the total amount of light exiting the optical waveguide .

The device includes a charging spring attached to at least a portion of the sensor frame and also supports the sensor pad. The charging spring is configured to counteract at least some of the pressure exerted against the sensor pad at the anatomical location of a subject. The charging spring is adapted to allow desirable displacement of the sensor pad at maximum pressure. In some implementations, the charging spring can be adapted to provide a maximum sensor pad displacement between 0.5 and 3 millimeters at maximum pressure.

In some implementations, the device may include a pressure sensor to detect a pressure applied to the anatomical location. The output unit can receive a pressure input indicating the pressure applied to the anatomical location from the pressure sensor. In some implementations, the output unit can generate the vital signs using the indicator signal from the received optical signal and the pressure input.

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In some implementations, the subject's anatomical location is an upper arm. The sensor frame can be configured over the sensor fixation device such that the optical sensing system is positioned to detect movement due to a pulse from a brachial artery that results in compression or flexion of at least a portion of the brachial artery. the compressible optical waveguide. In some implementations, the vital signs can be at least one of a heart rate, a blood pressure waveform, a systolic blood pressure, a diastolic blood pressure, an average arterial blood pressure, a differential pressure, and an arterial elasticity. .

In some implementations, the device may include a guide wave support structure that has a non-ductile surface to support at least a portion of the optical wave guide. The optical sensing system can be adapted to cause flexural deformation in an unsupported portion of the optical waveguide in response to an arterial pulse.

In some implementations, the device may include an incompressible flexible support surface that supports the optical waveguide over substantially its entire length. For example, the waveguide support surface can be a flexible electronic circuit board. The waveguide can be attached to the supporting surface with a flexible elastomer adhesive. In some implementations, the optical source device, the optical detector, and / or associated electronic components can be mounted on the surface of the waveguide support surface. In some implementations, the waveguide support surface may include a support return member that is configured within the support surface and adapted to resist flexing of the support surface. In some implementations that include a sensor pad, the support return member can be adapted to provide increased contact pressure between the sensor pad and the optical waveguide when the sensor pad is moved from a resting position to a maximum shift position. The optical waveguide can be tailored such that increased contact pressure causes a reduced amount of light to exit the second end of the optical waveguide.

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

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

In some implementations, the cladding may have a Shore A durometer between 45 and 55 and the core may have a Shore A hardness between 30 and 45. In some implementations, the waveguide may be capable of guiding at least 10,000 modes ( for example, at least 50,000 modes). In some implementations, the core can have a refractive index between 1.43 and 1.50 (for example, between 1.45 and 1.47) and the cladding can have a refractive index between 1.39 and 1.48 (for example, between 1.39 and 1.41). In some implementations, the core can have a radius of at least 45 microns (eg, between 150 and 200 microns).

In some implementations, the optical waveguide can include an elastomer (eg, a siloxane elastomer). The elastomer can be selected from the group consisting of polysiloxane, polyurethane, polybutadiene rubber, and combinations thereof.

Details of one or more implementations of the invention are set forth in the accompanying drawings and description below. Other features, objects, and advantages of the invention will be apparent from the description, drawings, and claims.

DESCRIPTION OF DRAWINGS

Figure 1 represents an implementation of the device to measure vital signs

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Figures 2A, 2B, and 2C depict various implementations of the vital sign device positioned on an upper arm, and show three different levels of cuff pressure that are related to systolic blood pressure.

Figure 3 represents a series of pulses during deflation of a cuff detected by a pressure sensor pneumatically coupled to the cuff compared to pulses obtained simultaneously detected by an optical detection system supported by a sensor fixation device. .

Figure 4 depicts an implementation of a device for measuring vital signs having a sensor attachment device with an inflatable bladder.

Figures 5A, 5B, and 5C depict an implementation of a sensor frame containing the components of an optical detection system.

Figure 6 depicts an implementation of the optical detection system on a flexible, incompressible waveguide support surface.

Figures 7A-7C depict implementations of optical detection systems.

Figures 8A and 8B depict how a compressed waveguide results in a reduction in the amount of transmitted light.

Figures 9A and 9B depict how a bent waveguide results in a reduction in the amount of transmitted light.

Figures 10A-10D are cross sectional views of different waveguide implementations.

Figure 11 represents the transmission of pulsatile light in a waveguide subjected to oscillation deformation due to an arterial pulse.

Figure 12 depicts an implementation of an analytical method used to determine one or more vital signs by the output unit.

Reference symbols in the various drawings indicate the same items.

DETAILED DESCRIPTION

As shown in Figure 1, a device for measuring vital signs may include a sensor attachment device 102, a sensor frame 200 that supports an optical detection system, and an output unit 106. An output from the optical sensing system in the sensor frame 200 can be used to determine the measurement of a vital sign, eg, blood pressure of a patient, and specifically systolic and diastolic measurements for the blood pressure of the patient.

Sensor attachment device 102 supports sensor frame 200 and engages against an anatomical location of a subject 112, within which is an artery 118. In Figure 1, for example, anatomical location 112 is an upper arm. of a human patient. Sensor frame 200 can be positioned such that optical detection system 104 detects motion that corresponds to an arterial pulse when sensor frame 200 is positioned against anatomical location 112 of the subject. In this way it is possible to detect arterial pulses with the optical sensing system when the sensor fixation device 102 exerts a pressure on the subject's arm 112 that is at or below systolic pressure, but does not detect the arterial pulses when the sensor clamp 102 is above systolic pressure. Accordingly, the systolic pressure can be determined as the pressure applied to the anatomical location 112 when the first arterial pulse is detected by the optical sensing system, as a pressure is reduced from a pressure that exceeds the systolic pressure. Alternatively, the systolic pressure can be determined as the last pressure at which an arterial pulse is observed by the optical sensing system, since the pressure increases to a pressure that exceeds the systolic pressure. Additionally, the vital signs device can measure the relative strength of one or more arterial pulses, and / or detect a pulse waveform, when the sensor attachment device exerts a pressure less than systolic pressure on the arm of the patient. patient, and from those measurements, determines a number of different vital sign measurements including systolic and diastolic pressure measurements for the subject. For example, diastolic pressure can be determined based on predetermined pulse waveform characteristics, such as a ratio of pulse amplitudes and / or the shape of the pulse waveform between arterial pulses.

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Optical detection system 104 employs what may be referred to as an optical power modulation method to detect and measure arterial pulses. An exemplary optical detection system that implements such an optical power modulation method, referring in particular to Figure 5C, includes an optical waveguide 212 supported by sensor frame 200, an optical source 202 positioned to deliver optical energy to a first end of optical waveguide 212, and an optical detector 240 positioned to detect an amount of optical energy exiting from an opposite second end of optical waveguide 212. An output unit 106, for example as shown in Figure 1, is connected in order to receive a signal, for example an electrical signal, from the optical detection system, and in particular from the optical detector 240, wherein the signal is indicative of an amount of light at a given point as it exits the second, opposite end of the optical waveguide that is detected by optical detector 240. From that received signal, the output unit 106 generates a vital signs measurement. Optical sensing system 104 is actuated, or responds to, an arterial pulse by virtue of compression or bending of at least a portion of optical waveguide 212 of the sensing system, resulting in a reduction in the amount of optical energy exiting the optical waveguide and accordingly a reduction in the amount of optical energy received by the optical detector.

By way of example, a vital sign may include a heart rate, a blood pressure waveform, a systolic blood pressure measurement, a diastolic blood pressure measurement, an average arterial blood pressure measurement, a differential pressure measurement, and / or a measurement of arterial elasticity. In some implementations, vital signs can be determined from arterial pulse timing, the amplitude and / or magnitude of arterial pulses, and / or arterial pulse waveforms. In some implementations, vital signs can be determined from the output received only from the optical detection system 104, while in other implementations vital signs can be determined from that output in combination with other data (for example, the data regarding pressure inside a pneumatic sleeve). As an example of the above case, a heart rate can be determined from only the output received from the optical detection system 104. The present vital sign measurements can be taken at any extremity location, including but not limited to the upper arm, wrist area, legs, and fingers. Sensor fixing device

The sensor attachment device can be any structure adapted to support and position a sensor frame 200 or a portion thereof adjacent to an anatomical location of a subject 112 such that the optical detection system 104 within the sensor frame 200 can detect an arterial pulse. The sensor fixation device can hold the sensor frame 200 adjacent to an anatomical location of a subject 112 at a predetermined sensor fixation pressure or an adjustable sensor fixation pressure. For example, the sensor attachment device can be an adhesive bandage or sleeve (eg, an elastic sleeve or an adjustable sleeve).

As shown in Figure 4, a sensor attachment device 102 may be an adjustable cuff 120 having an inflatable bladder 122. For example, the sensor attachment device 102 may be an assembly that includes a sleeve comprising a material. fabric that is configured to encircle or encircle an anatomical location (for example, a limb) of a subject. Inflatable bladder 122 can be located within the cuff to partially encircle or encircle a limb. As such, the sensor attachment device 102 is adapted to apply pressure to the limb when inflated and thereby compress an artery within the limb.

Generally, a sleeve type sensor fixation device 102 for use in the presently described systems and methods may be of a type that either partially or completely surrounds the limb, or it may be of a type that applies pressure locally as it can be advantageous at certain anatomical sites, including the wrist over the radial artery. The bladder 122 in such a device 102 can be pneumatically connected to a pump 124 via a hose 116, as is the case in Figure 4. In some implementations such as those shown in Figure 4, a cuff can be inflated pneumatically adjustable (eg, through a pump 124) and deflated (eg, through a valve 126) to adjust the pressure applied to a portion of a subject's body 112. In some implementations, a system may include an inflation controller 452, as included in the output unit 106 as shown in Figure 12, to control inflation and deflation of the cuff. In other implementations, an inflated controller may be included as a separate controller unit to control the operation of the vital sign device.

As such, various forms of a sensor attachment device can be applied to different portions of a subject's body. The sensor attachment device can be calibrated and arranged for placement in an anatomical location on a subject's body adjacent to a predetermined artery of the subject. As shown in Figures 1 and 2A-2C, the sensor attachment device 102 can be located on an upper arm (above a subject's elbow) such that the optical detection system within the sensor frame 200 it can detect the movement that corresponds to an arterial pulse in the brachial artery 118. The sensor fixation device can also be adapted for placement on the wrist such that the optical sensing system in the sensor frame can detect movement that corresponds to an arterial pulse in the radial artery. The device

The sensor attachment ES 2 396 258 T3 can also be placed on a leg (eg, at the ankle to detect pulses in an artery), the neck, or any other part of the body where an arterial pulse can be detected.

As shown in Figures 2A-2C, sensor frame 200 can be located near the midpoint of sensor fixture 102 (as shown in Figure 2A), at the midpoint of sensor fixture 102 (as shown in Figures 2B and 2C), or distal to the midpoint of sensor attachment device 102 (not shown). The placement of the sensor frame 200, and more specifically the sensing portion (eg, a sensor pad) of the sensor frame 200, with respect to a pressure-imparting device can impact the data obtained. In implementations where the sensor fixation device 102 applies pressure to the anatomical location, as shown in Figures 2A-2C, the position of the sensing portion of the detection frame 200 within the sensor fixation device 102 can impart can impart the data obtained. In some implementations, a pressure applied to an artery that lies below the surface of an anatomical location may be non-uniform. For example, although a pressure-imparting delivery device 102 can apply uniform pressure, the pressure transmitted through the tissue layers can result in non-uniform pressure against an artery lying some distance below the surface. In some implementations, the pressure applied to an artery lying some distance below the skin by an adjustable cuff may be greater at the midline of the cuff and less at the margins of the cuff. The location of the sensor frame 200 related to the sensor fixation device 102 can be set to optimize the sensitivity for selecting the characteristics of the arterial pulse. In some implementations, the sensor frame 200 and the sensing portion (eg, the sensor pad) of the sensor frame 200 can be located in the midline 134 of the cuff in such a way that it is not sensitive to pulsatile magnification of the arterial segment under the proximal part of the cuff when the cuff pressure exceeds the systolic pressure, thus allowing an accurate determination of the systolic pressure when the midsection of the arterial segment is opened.

In other implementations, not shown, the sensor frame 200 and the sensing portion (eg, a sensor pad) of the sensor frame 200 can be located near the distal margin of the sleeve in such a way that it is specifically sensitive to pulsatile arterial dimension changes at that location. Accordingly, the unique characteristics of the arterial pulse waveform can be identified in the diastolic pressure in a distal position, and the effects of arterial elasticity in the more distal arteries can be detected. Outward flexing of the skin at the midline 134 of the cuff, and also distal to the midline 134, occurs during systole when the cuff pressure is below the systolic pressure. At cuff pressures that exceed systolic blood pressure, arterial oscillations are limited to the proximal area of ​​the cuff, as discussed above.

In some implementations, not shown, the device may include a second pressure-imparting device from the sensor attachment device that holds the sensor frame having the optical detection system. The second pressure-imparting device can be adapted to be positioned against a second anatomical location of a subject proximal to the anatomical location of the sensor attachment device to allow detection of arterial pulse by the optical sensing system in a distal and separate position. pressure-imparting device. Accordingly, the optical detection system can detect an arterial pressure waveform at a position spaced and distal to the point of arterial occlusion, and thus allow detection of unique features of an arterial waveform. The second pressure-imparting device can be an adjustable cuff. In some implementations, the pressure-imparting device and the sensor attachment device may be adjustable sleeves.

Figure 2A depicts a sensor fixation device 102 that imparts a pressure on the arm that exceeds the arterial systolic pressure of the brachial artery enough to result in minimal artery opening under the leading edge of the sensor fixation device 102 at systole. The amount of pressure imparted against the sensor attachment device 102 will pulse slightly due to arterial expansion at the leading edge during an arterial pulse. Arterial opening does not occur at the positioning of the sensor frame 200, and therefore the optical sensing system 104 in the sensor frame 200 does not produce a pulsatile signal. However, a pulsatile signal will occur at a higher pressure if the sensor frame 200 is located near the midpoint of the sensor fixture 102 than if it is located at the midpoint of the sensor fixture 102.

Figure 2B depicts a sensor fixation device 102 that imparts a pressure that slightly exceeds arterial systolic pressure, such that arterial aperture 118 extends near the midpoint of sensor fixation device 102 in systole. The oscillation in pressure imparted during the sensor clamp 102 during an arterial differential pressure would be greater than in the case of Figure 2A, when the arterial expansion occurs over almost half of the segment located within the sensor clamp. . However, arterial opening does not occur at the midpoint of the sensor attachment device 102, and therefore the optical detection system 104 on the sensor frame 200 does not produce a pulsatile signal.

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Figure 2C depicts a sensor attachment device 102 that imparts a pressure below arterial systolic pressure such that the entire artery segment 118 momentarily opens at systole. Oscillations in pressure imparted against sensor clamp 102 during an arterial pulse will be even greater in amplitude. Arterial aperture at the location under sensor frame 200 causes optical sensing system 104 to register a pulsatile signal.

The upper portion of Figure 3 depicts the pressure pulses detected in a sensor clamp 102 imparted by the series of arterial pulses as the pressure imparted by the sensor clamp 102 is reduced from a pressure that exceeds blood pressure. a subject's systolic pressure at a pressure below a subject's diastolic blood pressure. The lower portion of Figure 3 represents pulses determined from the optical sensing system with the sensor frame at the midpoint of a sensor clamp 102 as the pressure imparted by the sensor clamp is reduced from from a pressure that exceeds the systolic blood pressure of a subject to a pressure below the diastolic blood pressure of a subject. As shown, the optical sensing system within the sensor frame does not detect any pulse until the imparted pressure is at or below systolic blood pressure. This can allow an accurate determination of systolic blood pressure and the waveform detected by the optical sensing system can allow calculation of other vital signs.

Figure 4 depicts an implementation of a sensor attachment device 102. The sensor attachment device may be an adjustable cuff 120 having an inflatable bladder 122. The cuff may include a fabric material configured around a limb of a subject. . The inflatable bladder 122 can partially, but not completely, surround the limb, and can be adapted to apply pressure to the limb when it is inflated and thereby compresses an artery within the limb. Adjustable cuff 120 can be adapted to wrap around a subject's upper arm and hold sensor frame 200 in position to apply equal pressure to the limb. An optical detection system can be located within sensor frame 200 to detect arterial pulses from the brachial artery. The cuff 120 may include hook and loop fasteners 132 (eg, Velcro®) or other fastening devices, which can be used to secure the cuff 120 around a limb of a subject. Cuff 120 can be wrapped around a limb of the subject and bladder 122 can be inflated to impart pressure on the limb. The bladder 122 can be connected to a pump 124 by a hose 116. The bladder 122 can also be attached to a valve 126 that can control deflation of the bladder 122. The pressure in the bladder 122 can be measured with a pressure transducer. 128. The pressure transducer 128 can be located in the bladder, as shown, or it can be pneumatically connected to the bladder 122 (eg, through hose 116).

The components of the optical sensing system can be packaged within the sensor frame 200 (eg, a housing) located at the midpoint 134 of the sleeve 120. The sensor frame 200 can be attached to the sleeve in a non-matching location. with the bladder part. The sensor frame 200 may be opposed on 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 fabric when the inflatable bladder 122 is inflated. For example, the top surface of the sensor frame 200 may be approximately flush with an internal surface of the sleeve. Sensor frame 200 can be located on cuff 120 such that optical sensing system 104 can detect a pulse from an artery when cuff 120 wraps around an anatomical location of a patient.

Output unit

As shown in Figures 4 and 12, the output unit receives signals (eg electrical signals) representative of an amount of optical energy (eg light) exiting the second end of the optical waveguide and is detected thus by the optical detector 240. These signals can be transmitted through electrical cables 108. In some implementations, the output unit 106 can also receive other data. For example, as shown in Figure 4, cables 108 can transmit data in the form of signals (eg, electrical signals) from a pressure transducer in the bladder 122 of a cuff 120 to the output unit 106 for allowing the output unit 106 to determine an amount of pressure applied to an anatomical location of a patient. In some implementations, the output unit 106 can receive data regarding the amount of optical energy received by an optical detector from the optical detection system via wireless transmission.

As shown in Figures 1, 4, and 12, the vital sign measuring device may include a display unit 114 to display one or more vital signs (eg, heart rate, systolic pressure, and diastolic pressure). As shown in Figure 4, the output unit 106 can be packaged with the display unit 114. In some implementations, not shown, the output unit may be within the sensor frame, it may be in another portion of the sleeve assembly, or it may be remotely located and in communication with the optical sensing system via wireless transmissions. Cables can transmit data (eg, via electrical signals) from output unit 106 to display device 114. In others

In implementations, the output unit 106 can transmit vital sign measurements via wireless transmission.

In some implementations, the output unit may include an alarm system to produce a human detectable signal when a vital signs measurement generated by the output unit meets predetermined criteria. For example, the output unit can be adapted to create a visual or audio alarm to alert a user that vital signs are outside of a predetermined range.

The output unit 106 may perform a number of data processing steps, calculations, or estimation functions, some of which are discussed below. Output unit 106 may include a processor for determining vital signs from signals from the optical sensing system with or without other data (eg, data regarding a pressure applied to an anatomical location by an adjustable cuff as shown. shown in Figure 4).

Sensor Frame

As shown in Figures 5A, 5B, and 5C, an optical detection system 104 may be contained within a detection frame 200 (eg, a housing). The function of the sensor frame 200 is to maintain pressure against the skin and transmit the mechanical pulse of the arterial pulses to the optical sensing system 104 without transmitting the pneumatic cuff pressure pulse. The function of the optical detection system 104 is to generate a signal representative of the arterial pulse.

Sensor frame 200 can be positioned against an anatomical location (eg, against a subject's skin) to detect arterial pulses by movement of sensor pad 232, which can be positioned adjacent to the anatomical location. Sensor pad 232 can be configured such that it moves as a result of increased contact pressure caused by inflation of the bladder. Movement of sensor pad 232 can result in compression or flexing of optical waveguide 212. Sensor frame 200 can also include a load spring 234 attached to sensor pad 232 to count the force applied to the sensor pad 232 by the anatomical location of the subject. Charge spring 234 can also adhere to at least a portion of sensor frame 200. Sensor frame 200 may also include structures to support the waveguide, such as an incompressible, flexible waveguide support surface 233 after the waveguide rests, and / or a non-ductile waveguide support structure. guide 235 to support optical waveguide 212 against forces applied to optical waveguide 212 by sensor pad 232. Sensor frame 200 may also include cables 108 for transmitting data from optical detector 240 to output unit 106. In some implementations, not shown, sensor frame 200 may include an output unit and may include cables that transmit data. from the output unit to an external source (for example, a display). In some implementations, the sensor frame 200 can be between 0.7 and 1.3 inches wide (for example, approximately 1 inch), a length between 1.5 and 2.2 inches (for example, approximately 1.7 inches), and a thickness between 0.3 and 0.9 inches (for example, about 0.6 inches).

As shown in Figures 5A, 5B, and 5C, a sensor pad 232 adapted for placement against an anatomical location of a subject can be attached to a load spring 234. The sensor pad 232 can extend outside of the frame frame. sensor 200 when in a relaxed state. For example, the sensor pad 232 can extend outside the sensor frame 200 by at least 0.1 inch (eg, between 0.1 and 0.3 inches). As shown, sensor pad 232 extends out from sensor housing 200 by 0.161 inch. Sensor pad 232 can be of any shape. The sensor pad 232 may have a diameter of at least 0.3 inches, for example between 0.3 and 0.8 inches (for example, about 0.6 inches). In some implementations, for example as shown in Figure 5C, the sensor pad 232 may be attached to the spring 234 by a hinge 236 that allows reciprocating movement of the sensor pad 232. In some implementations, as shown in In Figure 5C, the sensor pad 232 may have a sloped top surface. Sensor pad 232 may be adhered to or otherwise positioned to cause compression or flexing of optical waveguide 212 of optical detection system 104. As shown in Figure 5c, sensor pad 232 may include a portion pressure gauge 238 adapted to cause localized compression of optical waveguide 212. Sensor pad 232 may also be positioned within cutout 252. The spacing between cutout 252 and sensor pad 232 can impart the amount of movement of sensor pad 232 allowed by sensor housing 200 due to arterial pulses. The gap between cutout 252 and sensor pad 232 can be approximately 0.1 inch.

Cables 108 can transmit data from optical detector 240 to output unit 106, as discussed above. In some implementations, not shown, the output unit can be included within the sensor frame and cables can transmit vital sign data to devices outside of the housing. In

In some implementations, not shown, the optical detection system 104 can transmit data from the sensor frame 200 via wireless transmission.

Charging spring 234 can count a force applied to sensor pad 232 from an arterial pulse and returns the sensor pad to an initial state after the arterial pulse. The biasing spring 234 can thus limit the amount of compression and flexural deformation of the waveguide due to an arterial pulse. The charging spring 234 can be selected such that the optical transmission factor is more sensitive to waveguide deformation within the useful range of sleeve pressures. The combination of the charging spring 234 and other features of the sensor frame 200 and the optical sensing system 104 can provide forces to counteract such that an applied pressure of mm Hg will displace the sensor pad by at least 1 mm from a idle state. In some implementations, sensor frame 200 and optical sensing system 104 can be tailored such that an applied pressure of 150mmHg will displace the sensor pad by at least 2mm from the idle state. In some implementations, the charging spring 234 can be adapted to provide a maximum sensor pad displacement between 0.5 and 3 millimeters at maximum pressure (eg, between 0.8 and 1.5 millimeters at maximum pressure). In some implementations, the sensor frame 200 and optical sensing system 104 can be tailored such that an applied pressure of between 80 and 150 mmHg (for example, between 100 and 130 mmHg) can cause an upper surface of the pad sensor is approximately flush with a top surface of sensor frame 200. In some implementations, the sensor pad 232 may be nearly flush with the sensor frame 200 when positioned against the anatomical location of a patient by the occlusion device 102 with the occlusion device providing pressure to the anatomical location that exceeds systolic pressure. In some implementations, the top surface of the sensor frame 200 may be approximately flush with an internal surface of the sensor fixture (eg, the adjustable sleeve).

Sensor frame 200 may also include waveguide support structures, such as incompressible flexible waveguide support surface 233 and / or a non-ductile guide wave support structure 235 to support waveguide 212. of the optical sensing system 104 against the force applied by the sensor pad 232. Waveguide support surface 233 can have an incompressible flexible support surface and can extend the entire length of optical waveguide 212. In some implementations, as shown in Figure 6, the support Waveguide 233 may have a support return member 237 configured within the support surface and adapted to oppose flexing of the support surface. For example, return support member 237 within waveguide support 233 may be a high memory member, such as a steel spring, that can return the waveguide to its undeformed position following each pulsatile deformation. . The support return member 237 can be adapted to provide increased contact pressure between the sensor pad and the optical waveguide when the sensor pad is moved from a rest position to a maximum displacement position, with the guide optical waveguide tailored such that said increased contact pressure causes a reduced amount of light to exit the optical waveguide. In some implementations, the support return element 237 may work with the biasing spring 234 to carry out the increased contact pressure. In some implementations, the waveguide support surface 233 may have a flexible electronic circuit board, to which the waveguide is attached with a flexible elastomer adhesive. As shown in Figure 6, the waveguide support surface 233 may also support and carry the optical source 202 and / or the optical detector 240. In some implementations, other associated electronic components can be mounted on the support surface. waveguide 233.

The guide wave support structure 235 is not ductile. In some implementations, as shown in Figure 7A, the waveguide support structure 235 may support the portion of the waveguide 212 that is driven by the sensor pad 232 (eg, over substantially its entire length). Accordingly, the waveguide 212 can be compressed between the waveguide holder 235 and the pressure portion 238. Figures 8A and 8B, discussed below, depict how compression of waveguide 212 can result in a reduction in the amount of light transmitted to optical detector 240. In other implementations, as shown in Figures 7B and 7C, the Waveguide support structure 235 may support a portion of the waveguide spaced from the portion of the waveguide that is actuated by sensor pad 232. In some implementations, movement of the sensor pad 232 may result in flexing of the waveguide 212. Figure 7B depicts an implementation where the sensing pad acts directly against the waveguide to result in flexing of the guide. optical waveguide 212. Figure 7C depicts an implementation where a pressure portion 238 is pressed against a located portion of the waveguide. This can result in some compression combined with some bending of the waveguide in an adjacent region. Figures 9A, and 9B, discussed below, depict how bending of waveguide 212 can result in a reduction in the amount of light transmitted to optical detector 240.

Optical detection system 104 within sensor frame 200 may act as a motion detection system (eg, a motion detection system adapted to detect localized motion associated with an arterial pulse). The optical detection system 104 within the sensor frame 200 can detect

ES 2 396 258 T3 the movement that corresponds to an arterial pulse when the sensor fixation device is positioned against the anatomical location of the subject, rather than simply pressure applied to the sensor pad 232. For example, a surface pressure sensor (for example, a piezoresistive type pressure sensor) can detect changes in pressure due to an arterial pulse even when the pressure applied to the anatomical location by the occlusion device 102 exceeds the pressure. systolic. At high cuff pressure (above systolic pressure) the artery near the occlusion device 102 (for example, an adjustable cuff) can impart a pulsatile impact to the anatomical location delivered through the tissue, causing an increase in pressure. pulsatile within the occlusion device 102. This effect causes a pulsatile tensioning of the occlusion device 102, which could be detected by a surface pressure sensor adhered to the inner surface of the occlusion device 102, despite the fact that there is no contraction of the cuff due to the tissue being essentially "Incompressible" and the artery is continuously occluded in the area below the pressure sensor. A signal of an amount of pressure applied by the occlusion device (i.e., a cuff bladder pressure sensor) and the surface pressure sensor will be similar above and below systolic pressure because the effect of the opening of the artery allows blood flow is smaller than the effect of the pulsatile impact for the cuff described above. In contrast, an optical sensing system within a sensor frame that acts as a motion sensor may have little or no response due to cuff tensioning at high cuff pressures and avoid detection of motion during arterial pulses at high pressure pressures. above systolic pressure. Accordingly, the use of an optical sensing system within a sensor frame such as a motion sensor can more accurately indicate systolic blood pressure than a pressure sensor. Additionally, no separate accurate blood pressure measurement is needed for calibration or setting a reference point.

Optical Detection System using Optical Power Modulation

As shown in Figures 5C, 6, and 7A-7C, the optical detection system 104 may include an optical source 202, an optical waveguide 212, and an optical detector 240. As discussed above, the optical detection system 104 may be supported by a sensor frame 200 (eg, a housing) supported by the sensor attachment device 102. Optical source 202 can be optically coupled to optical waveguide 212 such that optical energy (eg, light waves 218) travels from optical source 202 at a first end of optical waveguide 212. In some implementations, an LED can be used as the optical source 202. An optical detector 240 receives the optical energy exiting a second opposite end of the optical waveguide 212 and can generate a signal indicating the amount of light received. In some implementations, optical detector 240 receives substantially all of the light that exits the second end of optical waveguide 212. In some implementations, optical detector 240 may be a PIN diode photodetector, a CCD (Charge Coupled Device) detector. ), or a CMOS (Complementary Metal Oxide Semiconductor) detector.

Optical Wave Guide

Optical waveguide 212 can be an optical fiber or any liquid, gel, or solid that transmits light waves by internal reflection or refraction. An optical waveguide 212 may include a length of optically transparent material, commonly referred to as the "core" 215, that is surrounded by a material of lower refractive index, commonly referred to as the "cladding" 217. The core 215 may have a relatively high refractive index (N₂), with respect to the minor refractive index (Ni) of cladding 217. The difference between the core and the refractive cladding indices defines the numerical aperture (NA) of the waveguide, according to the relationship:

2 1/2

NA = (N, -N₍ )

It is the NA and the critical angle (9 _c) of a waveguide governing the confinement of light within the core of the waveguide. If the angle of incidence of a ray of light at the core / cladding interface with respect to a vector normal to the interface is less than the critical angle (_c), then the beam is not reflected internally but will escape from the core and be lost. Without₂ is very close to Ni (that is, NA—> 0), the critical angle will approach 90 degrees, and almost all light escapes within a short waveguide period. Without₂ and Nor are they different enough in value, a large portion of the light will remain confined. Optical energy (e.g. 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 β_c). The critical angle (8_C) can be calculated using the following equation:

= arcsin (Ni / Nz)

ES 2 396 258 T3

Another characteristic of an optical fiber or optical waveguide is the number of modes that are excitable. In an optical waveguide, 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 and external speckled mode pattern of an optical fiber. On a single mode fiber, only one intensity peak is allowed. In multi-mode fibers, a large number of intensity peaks can occur anywhere along the waveguide. In any waveguide with a circular cross section, the "zero order" mode is formed by light propagating along the waveguide axis (assuming a perfectly straight waveguide). The so-called "higher order modes" are formed by light that is not started in the axial direction, but at some angle to the axis. These modes are driven by the difference in refractive index between the core and the cladding and each of them will generally have less intensity than the zero order mode. When a stage index waveguide flexes at some location, the low-order and zero-order modes become higher-order modes because they are no longer held at or near the center line. In order for light to occupy the higher order modes in a waveguide, either the light source must be composed in part of light rays that are at a nonzero angle relative to the axis (but still within the numerical aperture of the waveguide), or else the waveguide must be rolled or flexed. In general, some higher order modes will exist in a waveguide that is illuminated by a collimated light source, and conversely a large number of higher order modes will exist in a waveguide that is illuminated by a light source. divergent.

As can be seen from the Figures. 8A, 8B, 9A and 9B, compression and / or bending of a waveguide preferentially removes the higher order modes, and has a relatively minor effect on the lower order modes. The sensitivity of the optical system for small compressions and / or small amounts of bending depends on the availability of a sufficient number of excited waveguide modes. For example, in a case of only five excited modes, theoretically only five different levels of transmission optical power loss could be detected, which would produce a fairly coarse relationship between deformation and the amount of optics detected by the optical detector of the system. optical detection. On the other hand, if there are 10,000 excited modes, the relationship between the deformation and the detected optical energy could be more finely determined and relatively small deformation changes can be detected. Accordingly, in some implementations, the optical source can provide a divergent beam of an NA that is approximately equal to or greater than that of the waveguide. If the light source NA is larger than the waveguide NA, the result is that the portion of light emitted at the largest angle of the axis escapes into the cladding immediately. The optical waveguide can also be formed in such a way that it is capable of guiding at least 10,000 modes (eg, greater than 50,000 modes). The number of possible modes in a stage index waveguide is provided by:

N = V²/ 2 where V is the normalized frequency. The normalized frequency (V) is calculated as follows:

V = 2ππ · ΝΑ / λ, where a is the radius of the nucleus of the optical waveguide, NA is the numerical aperture of the waveguide, as discussed above, and λ is the wavelength of light. The most practical light sources have a wavelength (λ) of between 0.7 to 0.85 microns. Therefore the product of a and NA must be on the order of 40 microns to satisfy the criteria for 50,000 modes. The practical range of NA is approximately 0.2 to 0.4. Consistent with the above, a waveguide having a NA of 0.4 would need to have a minimum of a 100 micron core radius to allow 50,000 modes, and a minimum radius of about 45 microns to allow 10,000 modes. In some implementations, the waveguide core 215 has a radius of at least 45 microns (eg, between 150 and 200 microns). The optimal size depends in part also on the actual deformation encountered by the waveguide (which is instead dependent on the waveguide Durometer, the mechanical pressure currently applied to the waveguide, and the amount of flexure of the waveguide). wave). In some implementations, the waveguide may have a soft elastomer core with a Shore A durometer between 45 and 55, a NA between 0.35 and 0.4 (corresponding to a core refractive index of 1.46 and a refractive cladding index of 1.41) , and a core radius of 150-200 microns. This design can produce a 50-70% transmission loss at a short waveguide length (2-4 cm) when the bending strain is 520 degrees over a 1-2 cm length and / or where the core it is compressed by 5-50%.

An NA of 0.2-0.4 can be achieved by having a refractive index difference between core and cladding of 2-4% in common optical grade materials. In light transmission applications, light is introduced at one end of a waveguide. If the waveguide is straight, the total internal reflection will cause the confinement of all the incoming light that is within the NA of the waveguide, and the loss of light will be minimal. If a waveguide is not straight, but has a certain curvature, part of the light undergoes total internal reflection until it reaches a curve, where the core / cladding interface is less than the critical angle (8_C) and leaks into the coating. Similarly, if a waveguide is compressed, some of the light is subjected to

ES 2 396 258 T3 total internal reflection until a compressed area is reached, where the core / cladding interface is reached less than the critical angle (0_C) and leaks into the coating. Variable transmission losses due to pulsatile bending or compression can be measured with an optical detector 240 (e.g., a photosensor) at the optical waveguide output and used to characterize the pulsatile force acting on the waveguide. .

Like that shown in Figures 8A, 8B, 9A, and 9B, an optical waveguide 212 causes internal reflection of optical waves 218 within the core of optical waveguide 212. However, compression, as shown in Figure 8B, or bending, as shown in Figure 9B, of the optical waveguide 212 results in a loss of optical energy because compression or bending of the waveguide Optics 212 results in additional light waves (such as light waves 263) reaching the interface between core 215 and cladding 217 at angles less than the critical angle (0c). As shown in Figures 8A and 8B, compression of the optical waveguide 212 results in a reduction in transmitted optical energy 261, due to loss of optical energy 263. As shown in Figures 9A and 9B, the bending of the optical waveguide 212 results in a reduction in the transmitted optical energy 261, due to the loss of optical energy 263.

Optical waveguide 212 can be flexible and / or compressible. In some implementations, the optical waveguide 212 can include an elastomer. For example, core 215, cladding 217, or a combination thereof can include an elastomer. Conventional glass and plastic fiber optics exhibit bending losses, but are generally non-deformable to a significant degree by mechanical compression. Compatible waveguides, however, can be manufactured using softer materials. In contrast to glass waveguides, such compatible waveguides can be easily deformed by small compressive forces. Examples of suitable elastomers include polysiloxane, polyurethane, and polybutadiene rubber. In some implementations, core 215 and liner 217 include a siloxane elastomer. For example, the optical waveguide may have a coating 217 composed of silicone elastomer and a core 215 composed of a second silicone elastomer of different refractive index. In some implementations, the coating elastomer may be a material that does not inhibit the cure of the core material. For example, the clad elastomer may have addition cure chemistry and the core elastomer may have platinum cure chemistry.

The coating 217 can be optically transparent or it can have a translucent appearance. Core 215 can be optically transparent. In some embodiments, the coating can have a refractive index between 1.39 and 1.48 (eg, between 1.39 and 1.41). In some embodiments, core 215 can have a refractive index between 1.43 and 1.50 (eg, between 1.45 and 1.47). The coating can have a Shore A durometer between 25 and 75 (eg, between 45 and 55). Core 215 can have a Shore A durometer of between 25 and 75 (eg, between 30 and 45).

Optical waveguide 212 can have a number of configurations. As shown in Figure 10A, liner 217 may have a circular cross-sectional shape. In some implementations, the liner may have a broad, flat bearing surface along its length that may serve as an adhesive bonding surface for adhesion of the optical waveguide 212 to a flexible surface, for example, a board. flexible circuit board used to support the optical waveguide within the optical detection system. For example, the wide, flat bearing surface can be attached to a waveguide support surface using a flexible elastomer adhesive. Figures 10B-10D show cross sections of examples of optical waveguides 212 having a wide, flat bearing surface 271.

The coating 217 of the optical waveguide 212 can be formed by an extrusion process. In some implementations, core 215 and cladding 217 can be formed in a co-extrusion process. In some implementations, liner 217 may be extruded in a first process to produce a constant cross-sectional shape that defines a hollow lumen. The core 215 can then be made by filling the lumen of the cladding 217 with a core material. For example, an extrusion process can be used to make any of the cross sectional shapes of the liner shown in Figures 10A-10D. In some implementations, the centerline location of the core can be configured to match the location of the output beam from the optical source 202, then the optical source 202 and optical waveguide 212 are mounted on the flexible waveguide bracket. 235, thereby facilitating ease of optical alignment of optical waveguide 212 to optical source 202.

Analytical methods

The optical detector 240 of an optical detection system 104 can generate an electrical signal 420 that indicates the amount of light received. The electrical signal 420 can be a function of time. The electrical optical detector signal 420 is analyzed to determine a number of vital signs. Output unit 106 can determine the amplitude and / or magnitude of each arterial pulse to determine one or more vital signs. In some implementations, the amplitudes and / or magnitudes for a series of arterial pulses can be determined to determine one or more vital signs. In some implementations, the time interval between pulses can be

ES 2 396 258 T3 measure during a series of arterial pulses sensed and used to determine heart rate. For example, Figure 11 demonstrates the transmission of pulsatile light in a waveguide undergoing oscillation deformation due to an arterial pulse. Some vital sign measurements, such as a heart rate, do not require input are relative to pressure applied to the anatomical location by, for example, a pneumatic cuff.

Blood pressure, for example, can be measured by placing the cuff (eg, as shown in Figure 4) on a patient's arm; by inflating the cuff to a pressure of at least 10 mmHg greater than the patient's systolic pressure; gradually deflate the cuff pressure to a pressure of at least 10 mmHg below the diastolic pressure; recording arterial pulse waveforms produced by optical detection system 104; analyzing the waveforms to determine one or more characteristics that correspond to the systolic pressure; further analyzing the waveforms to determine one or more characteristics that correspond to diastolic pressure; fully deflate the cuff; and display systolic and diastolic pressure. In some implementations, waveforms can be recorded during cuff inflation and deflation and both waveforms are used to determine systolic and / or diastolic pressure.

By observing the arterial waveform formed through this process, various vital signs can be determined and / or estimated, such as systolic pressure, diastolic pressure, and average blood pressure. In some implementations, the method of measuring blood pressure may include analyzing the arterial pulse waveforms by measuring the amplitudes of the sequence of waveforms recorded during deflation of the cuff; determining the cuff pressure at which the pulse waveform amplitude is significantly greater than the waveform amplitude of the preceding pulse that occurs at higher cuff pressure during deflation of the cuff; and visualize that pressure as the systolic pressure.

Systolic pressure can be determined in a number of ways based on data received from optical sensing system 104 and from data from sensor fixture 102. In some implementations, systolic pressure can be determined from pressure in which the pulse waveform amplitude is significantly less than the preceding pulse waveform amplitude that occurs at lower cuff pressure during cuff inflation. In some implementations, diastolic pressure can be determined during cuff deflation to cuff pressure where the pulse waveform is indicative of the pulsatile action of the arterial segment under the sensor. More specifically, diastolic pressure can be determined where the pulse waveform first indicates that the artery does not close completely at some point during the cardiac cycle. Different waveform analysis methods are also possible. A patient's systolic blood pressure can also be continuously monitored by measuring the baseline systolic pressure by one of the methods described above and then pressurizing the cuff to a constant pressure and then continuously monitoring the waveform. The constant pressure can be determined by the previously measured blood pressure reading (eg, peak blood pressure). A first measured arterial pulse width can then be used as a reference pulse width and subsequent pulse widths can be compared to the reference pulse width to estimate changes in blood pressure. In some implementations, the morphology of the pulse waves can be determined by pulsing, while the cuff is held at constant pressure. Pulse wave morphology can be continuously measured and is used to monitor blood pressure changes from a set point value.

In some implementations, such as shown in Figure 12, the output unit 106 can determine vital signs by one or more of the techniques described above. For example, output unit 106 may determine an amplitude, magnitude, and / or waveform of one or more arterial pulses in a waveform generator 436. In some implementations, the output unit 106 may include a systolic pressure calculator 442 to determine a systolic pressure for a subject based on a given amplitude, magnitude, and / or waveform and a pressure applied to the subject, which can be detected. (for example, a pressure sensed in an adjustable cuff by a pressure sensor). In some implementations, the output unit 106 may include a diastolic pressure calculator 444 to determine a diastolic pressure for a subject based on a given amplitude, magnitude, and / or waveform and a pressure applied to the subject, which can be detected. (eg, a pressure sensed in an adjustable cuff by a pressure sensor 128). In some implementations, a heart rate calculator 446 can determine a heart rate from either a particular arterial pulse waveform from the optical signal or from pressures sensed in a cuff adjustable by a pressure sensor 128.

The output unit 106 shown in Figure 12 also includes a pressure sensor 128 pneumatically connected to a bladder in the cuff, which transmits data regarding the pressure in the cuff as a function of time to the analog digital converter. 435. In some implementations, the output unit 106 can generate a pulse waveform as a function of cuff pressure. The output unit 106 shown in Figure 12 also includes an inflation controller 452, which can control the inflation and deflation means of the cuff to control the operation of the device. In some implementations, the unit of

ES 2 396 258 T3 outlet 106 can dynamically adjust the inflation and deflation of the cuff based on the characteristics of the detected arterial pulse.

A number of implementations have been described. However, it will be understood that various modifications can be made without departing from the scope of the invention. In accordance with the foregoing, other implementations are within the scope of the following claims.