WO2020176214A1

WO2020176214A1 - Finger cuff device with non-volume clamp, non-plethysmography pressure measurement method for continuous non-invasive blood pressure measurement

Info

Publication number: WO2020176214A1
Application number: PCT/US2020/016971
Authority: WO
Inventors: Jeong Soo Lee; Ernest William HEFLIN; Andrew Victor BARAJAS
Original assignee: Edwards Lifesciences Corporation
Priority date: 2019-02-26
Filing date: 2020-02-06
Publication date: 2020-09-03

Abstract

Disclosed is a finger cuff device to measure a patient's blood pressure from an artery of the patient's finger. The finger cuff device comprises: a finger cuff including a cavity to receive the patient's finger, the finger cuff extending around the patient's finger, and a bladder included in the finger cuff, in which, the bladder contains a fluid to apply a constant pressure to the patient's finger; and pressure sensor. The pressure sensor is in fluid communication with the fluid of the bladder and is used to measure the pressure applied to the bladder by the patient's artery to measure the arterial blood pressure of the finger.

Description

FINGER CUFF DEVICE WITH NON- VOLUME CLAMP, NONPLETHYSMOGRAPHY PRESSURE MEASURMENT METHOD FOR CONTINUOUS NON-INVASIVE BLOOD PRESSURE MEASUREMENT

BACKGROUND

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 62/810,767 filed February 26th, 2019, which is incorporated by reference herein in its entirety.

Field

[0002] Embodiments of the invention relate generally to continuous non-invasive blood pressure measurement. More particularly, embodiments relate to a finger cuff device to be used in measuring a patient’s blood pressure with a non-volume clamp, non

plethysmography pressure measurement method.

Relevant Background

[0003] Absolute non-invasive blood pressure measurements are typically performed using external cuffs that apply pressure to one or more arteries and the response of the arteries is observed to determine the blood pressure. Auscultatory and oscillometric blood pressure cuffs use this technique to obtain discrete (non-continuous) blood pressure (BP) measurements. The volume clamp method with a finger cuff uses related techniques to obtain continuous BP measurements.

[0004] Much work is being done to develop“cuff-less” BP measurement techniques that do not require applying an external force to the arteries or require very low forces. Pulse wave analysis (PWA) techniques that obtain an arterial“pulsatility” waveform, extract amplitude and timing features, and track changes in those features over time that correlate with changes in BP over time are a successful class of cuff-less BP measurements - but they are unable to obtain absolute BP values from which to track changes. Examples of PWA techniques include CSEM photoplethysmography techniques.

[0005] Non-invasive blood pressure measurements typically fall into two categories: a discrete but absolute blood pressure measurement, such as, a brachial cuff measurement performed by the auscultatory or oscillometric methods, and, tracking of relative changes in blood pressure values, such as the techniques by CSEM. Known methods of performing absolute blood pressure measurements on a patient require the application of pressure to some part of the patient’s body, such as the upper arm and/or finger, in a way that at least partially occludes blood flow. The occlusion of blood flow requires there to be times when pressure is not applied in order to allow blood to flow to tissues under and downstream from the occlusion location.

[0006] One example of non-invasively measuring blood pressure is utilizing a finger cuff with the volume clamping technique in which pressure is applied to a patient’s finger in such a manner that arterial pressure may be balanced by a time varying pressure to maintain a constant arterial volume. In a properly fitted and calibrated system, the applied time varying pressure is similar to the arterial blood pressure in the finger. The applied time varying pressure may be measured to provide a reading of the patient’s arterial blood pressure.

[0007] This may be accomplished by a finger cuff that is arranged or wrapped around a finger of a patient. The finger cuff may include an infrared light source, an infrared sensor, and an inflatable bladder. The infrared light may be sent through the finger in which a finger artery is present. The infrared sensor picks up the infrared light and the amount of infrared light registered by the sensor may be inversely proportional to the artery diameter and indicative of the pressure in the artery. Therefore, the finger cuff provides optical signals and an optical system.

[0008] In the finger cuff implementation, by inflating the bladder in the finger cuff, a pressure is exerted on the finger artery. If the pressure is high enough, it will compress the artery and the amount of light registered by the sensor will increase. The amount of pressure necessary in the inflatable bladder to compress the artery is dependent on the blood pressure. By controlling the pressure of the inflatable bladder such that the diameter of the finger artery is kept constant, the blood pressure may be monitored in very precise detail as the pressure in the inflatable bladder is directly linked to the blood pressure. In a typical present-day finger cuff implementation, a volume clamp system is used with the finger cuff. The volume clamp system typically includes a pressure generating system and a regulating system that includes: a pump, a valve, and a pressure sensor in a closed loop feedback system that is used in the measurement of the arterial volume. To accurately measure blood pressure, the feedback loop provides sufficient pressure generating and releasing capabilities to match the pressure oscillations of the patient’s blood pressure. [0009] The current issues that have to do with non-invasive blood pressure measurement devices out on the market today have to deal with accuracy, and the

restrictiveness of the design of how these systems are often implemented.

[0010] Currently, even with the most advanced continuous non-invasive devices that are currently on the market, they still rely on the method of volume clamping which is the method of continuous measuring blood pressure through the pressurization of the finger.

Even though volume clamping allows for accurate measurement and tracking of blood pressure through the finger using plethysmography, there is a large period, where even this method, can become extremely inaccurate due to the volume clamping process. Also, the act of volume clamping can affect the measurement itself artificially, putting it at risk of being inaccurate from the beginning due to certain patient populations and instances. This type of measurement is also very sensitive to movement making it difficult for this type of continuous blood pressure monitoring to move out of the OR/Critical Care sector of healthcare. Volume clamping also requires hardware and implementation that causes complications in the manufacturing and everyday use of those types of products (e.g., specially designed pressure measurement instrumentation circuits, sensors, highly controlled and accurate pump mechanisms, expensive material costs, etc.).

[0011] Further, other methods of continuous non-invasive blood pressure

measurement are simply inaccurate or too discrete for much health value in comparison to measurements that use volume clamping. And even though these methods may be used outside of the OR/Critical Care sector, these methods are not as accurate as the volume clamp method.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is a diagram of an example of a finger cuff device according to an optional example.

[0013] FIG. 2 is a block diagram of a portion of the finger cuff device shown in FIG. 1, according to an optional example.

[0014] FIG. 3 is a flow diagram of a process of measuring blood pressure according to an optional example.

[0015] FIGs. 4A and 4B are charts comparing pressure signals and pleth signals.

[0016] FIG. 5 is a chart illustrating the application of constant pressure such that high blood pressure with low pulsatility is more easily measurable according to an optional example. DETAILED DESCRIPTION

[0017] Various optional examples are related to the principles of physiology during volume clamp continuous blood pressure measurement utilizing a finger cuff. However, instead of using the plethysmography signal as a basis of performing proper volume clamping to extract the patient's arterial signal, pressure may be directly measured from a pressure transducer that is in direct contact with an incompressible transducing fluid. A bladder may be used on the patient’s finger to partially pressurize the tissues in the area of measurement. However, instead of air, the bladder may be filled with an incompressible fluid that has close to the same impedance as human tissue or blood. With the bladder applying an

approximately equal and constant pressure to the finger, the finger itself will become more of a constant rigid form allowing the natural signal of the artery to penetrate the finger and go into the bladder. These pressure changes may then be measured by a pressure transducer in line with the fluid system. These pressure wave fluctuations will be then used as a reference for the arterial waveform of the patient and be translated to appropriate pressures related to the patient’s blood pressure. An algorithm or equation may be used ensure that pressures are scaled appropriately for brachial translation as these pressures will be different from the patient’s actual arterial pressure at the finger due to the physics of pressure wave transduction over the measurement distance/inflection behavior.

[0018] In one example, disclosed is a finger cuff device to measure a patient’s blood pressure from an artery of the patient’s finger. The finger cuff device may comprise: a finger cuff including a cavity to receive the patient’s finger, the finger cuff extending around the patient’s finger, and a bladder included in the finger cuff, in which, the bladder contains a fluid to apply a constant pressure to the patient’s finger; and a pressure sensor. The pressure sensor is in fluid communication with the fluid of the bladder and is used to measure the pressure applied to the bladder by the patient’s artery to measure the arterial blood pressure of the finger. As one optional example, the pressure sensor may be a pressure transducer. However, any type of pressure sensor may be used.

[0019] Further, as an optional example, a processor may be coupled to the pressure transducer and may utilize pressure changes measured by the pressure transducer as a reference for an arterial waveform of the patient that may be translated into the arterial blood pressure of the patient. As an optional example, the processor may implement an algorithm to appropriately scale the arterial blood pressure measurement of the finger to a heart level blood pressure measurement of the patient. [0020] Further, as one optional example, the fluid of the bladder may comprise an incompressible fluid, such that, the incompressible fluid filled bladder applies an equal amount of constant pressure across the finger, such that, the finger becomes a constant rigid form allowing a natural signal of the artery to penetrate the finger into the bladder to be measured by the pressure sensor. As one optional example, the fluid may be a bio-blend oil. However, any suitable incompressible fluid or other type of suitable fluid may be used.

Further, as will be described, the pressure sensor may be located in the finger cuff itself or at a location external to the finger cuff. Moreover, in one optional example, measured arterial blood pressure may include systolic pressure, mean arterial pressure (MAP), and diastolic pressure. However, any suitable type of blood pressure measurements may be used.

[0021] As one example, with reference to FIG. 1, which illustrates an optional example of a finger cuff device 102, finger cuff device 102 includes a finger cuff 104 that may be attached to a patient’s finger and a processor 108, in which processor 108 may be attached to the patient’s body (e.g., a patient’s wrist or hand) as shown, as part of a suitable housing. Processor 108 may be attached on the patient’s hand or wrist with an attachment bracelet or band 106 that wraps around the patient’s wrist or hand. Attachment bracelet 106 may be metal, plastic, Velcro, etc. Cable 114 couples finger cuff 104 to processor 108. In other optional examples, processor 108 may be included in the finger cuff 104, itself, such that, only one integrated device is attached to the patient’ s finger.

[0022] Continuing with this optional example, as shown in FIG. 1, a patient’s hand may be placed on the face 110 of an arm rest 112 for measuring a patient’s blood pressure with processor 108. Processor 108 may be coupled to a patient monitoring device (not shown) through a power/data cable (not shown) or may be wirelessly connected to the patient monitoring device (e.g., without a cable). The patient monitoring device may be any type of medical electronic device that may read, collect, process, display, etc., physiological readings/data of a patient including blood pressure, as well as any other suitable physiological patient readings. Accordingly, data may be transmitted (wired or wirelessly) to and from the patient monitoring device and processor 108 of the finger cuff.

[0023] With reference to Figures 1 and 2, as one optional example, a finger cuff device 102 to measure a patient’s blood pressure from a finger of the patient includes a finger cuff 104. As previously described, finger cuff 104 includes a cavity to receive the finger, the finger cuff to extend around the finger. Further, the finger cuff device 102 comprises a bladder 206 in the finger cuff 104, in which, the bladder 206 contains a fluid to apply a constant pressure to the patient’s finger; and the finger cuff 104 includes a pressure sensor 204. The pressure sensor 204 may be in fluid communication with the fluid of the bladder and may be used to measure the pressure applied to the bladder 204 by the patient’s artery to measure the arterial blood pressure of the finger. The pressure sensor 204 may be located in the finger cuff itself or may be located in an external housing, as has been described. As one optional example, the pressure sensor 204 may be a pressure transducer. However, any type of pressure sensor (e.g., electronic, strain gauge, mechanical, magnetic, optical, combinations thereof, etc.) may be used.

[0024] Additionally, as another optional example, a processor 108 (and/or appropriate electronics, control circuitry, etc.) may be coupled to the pressure sensor 204 and may utilize pressure changes measured by the pressure sensor 204 as a reference for an arterial waveform of the patient that may be translated into the arterial blood pressure of the patient. As an optional example, the processor 108 may implement an algorithm to appropriately scale the arterial blood pressure measurement of the finger to a heart level blood pressure measurement of the patient. It should be appreciated that the use a processor is an optional example and that in some optional examples the finger cuff device 104 only includes the bladder 206 that contains a fluid to apply a constant pressure to the patient’s finger and the pressure sensor 206, in which, the pressure sensor is in fluid communication with the fluid of the bladder and is used to measure the pressure applied to the bladder by the patient’s artery to measure the arterial blood pressure of the finger. In this case, only the pressure sensor is used for blood pressure measurement and a processor is not utilized.

[0025] Further, as one optional example, the fluid of the bladder 206 may comprise an incompressible fluid, such that, the incompressible fluid filled bladder applies an equal amount of constant pressure across the finger, such that, the finger becomes a constant rigid form allowing a natural signal of the artery to penetrate the finger into the bladder 206 to be measured by the pressure sensor 204. As one optional example, the fluid may be a bio-blend oil. However, any suitable incompressible fluid (e.g., saline, medical grade hydraulic fluid, etc.) may be used or other types of fluid that may or may not be incompressible may be used for measurement by the pressure sensor 204, if suitable.

[0026] Moreover, the pressure sensor 204 may be located in the finger cuff 104, itself, or at a location external to the finger cuff 104. As one optional example, the pressure sensor 204 may located with the processor 108 as part of circuit device attached to the patient hand, arm, wrist or another location. As one optional example, a connector tube 114 may connect fluid of the bladder 206 to the pressure sensor 204 of the attached device with the processor 108. In other optional examples, all of the electronic components (e.g., including processor 108 and pressure sensor 204) may be present in the finger cuff 104, as an integrated device, to perform the functions. As an optional example, the pressure sensor 204 may be directly coupled to the bladder 206. Further, as has been described, in some optional examples, a processor is not utilized for blood pressure measurement and only the pressure sensor is utilized for blood pressure measurement.

[0027] As seen as an example, in FIG. 1, the patient’s finger with finger cuff 104, as well as their hand and arm, may be placed on the surface 110 of a table 112. As another optional example, the person may wear the finger cuff 104 anywhere and it does not have to be on a table. Also, as one optional example, the processor 108 and/or other circuitry (e.g., the pressure sensor 204) in an appropriate housing may be connected to the finger cuff by tube or cable 114, in which the housing or appropriate structure is connected by a band around the person’s wrist (as part of finger cuff device 102). As another optional example, all of the electronic components (e.g., including processor 108 and pressure sensor 204) may be present in the finger cuff 104, as an integrated device, to perform the functions. Similarly, finger cuff 104 and/or processor 108 (whether in an integrated device or divided

implementation, as previously described) may be connected (wirelessly /or by wire) to a display monitoring device to show the patient’s blood pressure and/or other physiological measurements. Further, as has been described, in some optional examples, a processor is not utilized for blood pressure measurement and only the pressure sensor is utilized for blood pressure measurement.

[0028] Also, in an optional example, finger cuff 104 may include an optical source and an optical sensor to form an optical source and sensor pair 202 to perform measurements of a plethysmography signal from an artery of the finger. In one optional example, optical source and optical sensor pair 202 includes a light emitting diode (LED) and photodiode (PD) (LED-PD) pair that may be used to obtain the plethysmography signal. However, it should be appreciated that utilizing an optical source and sensor pair is only an optional example of acquiring a plethysmography signal from an artery of the finger and that other devices and processes may be used. Moreover, in one optional example, measured arterial blood pressure may include systolic pressure, mean arterial pressure (MAP), and diastolic pressure.

However, any suitable type of blood pressure measurements may be used. [0029] With reference to FIG. 3, a flow diagram 300 illustrating an optional example method for measuring the blood pressure of a patient is shown. At step 302, the method applies, by the bladder 206, a constant pressure to the patient’s finger, in which, the patient’s finger is received and located in a cavity of the finger cuff 104. Further, at step 304, the method measures, by the pressure sensor 204, the pressure applied to the bladder 206 by the patient’s artery in their finger to measure the arterial blood pressure of the finger. As has been described, the pressure sensor 204 is in fluid communication with the fluid of the bladder 206.

[0030] With the previously described method that uses static pressure transduction readings to extract the arterial waveform, this allows for very accurate continuous arterial blood pressure measurement. This is because a pump is no longer needed, as opposed to prior finger cuff implementations that utilize a pump that therefore require active pressure translation. With no physical active pressure translation needed for the measurement, the fundamentals of continuous blood pressure measurement are changed, in a way, in which, there is no longer a risk of actively artificially altering the measurement from the beginning as may happen with active volume clamping.

[0031] With brief reference to FIG. 4A, FIG. 4A shows a pleth signal 402 and a pressure signal 404, for the same patient for the same session, which shows that they are directly linked (e.g., linearly related) and are generally inversely related to one another. With brief reference to FIG. 4B, FIG. 4B shows that when the pleth signal 408 is converted to be in correspondence with the pressure signal 406, and compared, they are basically the same. Therefore, this shows that both the pleth signal and the pressure signal can be used as measurements of blood flow and blood pressure. In particular, it has been found that by utilizing a finger cuff 104 with the bladder 206 that applies a constant pressure to the patient’s finger, as previously described, blood pressure at low pulsatility is more easily measurable than with prior finger cuff implementations. As shown in FIG. 5, which shows pleth signal 512 and pressure signal 514, by applying 120 mmHg constant pressure by the fluid filled bladder, high blood pressure with low pulsatility is easily measurable.

[0032] As one optional example, processor 108 of finger cuff device 102 connected to optical source and sensor pair 202 (e.g., to obtain the pleth signal) and to pressure sensor 204 (e.g., to measure arterial blood pressure from the finger), may be used to extract the patient’s arterial blood pressure waveform signal from the plethysmography signal. The patient’s arterial blood pressure waveform signal may be extracted from the plethysmography signal based upon an equation relating the plethysmography signal to the blood flow in the finger and the arterial blood pressure of the finger. As an example, as shown in FIG. 5, the arterial blood pressure waveform signal itself may be extracted from the plethysmography signal 512 based on the relationship between blood flow in the finger and the arterial blood pressure of the finger (as shown by pressure signal 514 as measured by the pressure sensor). It should be noted, as previously described, a 120 mm Hg constant pressure is applied by the fluid filled bladder 206 to the finger. By allowing the plethysmography signal 512 to oscillate, the arterial blood pressure waveform signal itself may be captured. As has been described, in one optional example, pressure sensor 204 via an incompressible fluid is coupled to the incompressible fluid filled bladder 206 allowing pressure variations of the bladder from the artery to be measured by the pressures sensor, such that, pressure fluctuations may be used in the equation relating the plethysmography signal to the blood flow in the finger and the arterial blood pressure of the finger in extracting the patient’s arterial blood pressure waveform signal from the plethysmography signal. Therefore, in optional examples, pressure fluctuations measured by the pressure sensor may be used as a reference for the

plethysmography signal and ultimately for the resulting translated blood pressure waveform utilizing the equation. However, it should be appreciated that this is only optional example of acquiring a translated blood pressure waveform and that other processes may be used.

Additionally, suitable digital signal processing (DSP) techniques may then be used to filter out artifacts such as respiration and high frequency noise to allow for a clean arterial blood pressure waveform signal.

[0033] By utilizing the previously described apparatus and method of extracting arterial blood pressure measurement from static pressure transduction measurement, the measurement is greatly simplified no longer requiring additional complicated circuity, sensors, or mechanics that is required for prior art finger cuff active volume clamping, while still maintaining the same amount of accuracy. The minimum circuit implementation needed may include processor 108, pressure sensor 204, as previously described. In some optional examples, as previously described, only a pressure sensor in combination with the bladder is utilized. However, any suitable hardware, sensor, etc., implementation may be used. This simplification also allows the finger cuff device to work outside of the OR/Critical Care sector of healthcare and move into other health spaces that would benefit from continuous blood pressure measurement. Spaces that in the past have been closed to finger volume clamp devices due to the environment (e.g., home, mobile, non-hospital, etc.) may now be used. In particular, with the measurement simplified using this method along with moving into new spaces, the previously described finger cuff device may be used with wireless capabilities and particularly designed virtual applications.

[0034] It should be appreciated that FIG. 2 illustrates a non-limiting optional example of a processor implementation to implement the previously described functions. As an example, a processor may comprise a processing unit, a memory, and an input/output connected with a bus. Under the control of the processing unit, data may be received from an external source through the input/output interface and stored in the memory, and/or may be transmitted from the memory to an external destination through the input/output interface.

The processing unit may process, add, remove, change, or otherwise manipulate data stored in the memory. Further, code may be stored in the memory. The code, when executed by the processing unit, may cause the processor to perform operations relating to data manipulation and/or transmission and/or any other possible operations.

[0035] It should be appreciated that aspects of the invention previously described may be implemented in conjunction with the execution of instructions by processors, control circuitry, circuitry, controllers, etc. (e.g., processor 108 used as an optional example of FIG. 2). As an example, a processor may operate under the control of a program, algorithm, routine, or the execution of instructions to execute methods or processes in accordance with embodiments previously described (e.g., the method 300 of FIG. 3, as well as other functions). For example, such a program may be implemented in firmware or software (e.g. stored in memory and/or other locations) and may be implemented by control circuitry, processors, and/or other circuitry, these terms being utilized interchangeably. Further, it should be appreciated that the terms processor, microprocessor, circuitry, control circuitry, circuit board, controller, microcontroller, etc., refer to any type of logic or circuitry capable of executing logic, commands, instructions, software, firmware, functionality, etc., which may be utilized to execute embodiments.

[0036] The various illustrative blocks, processors, modules, and circuitry described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a specialized processor, circuitry, a microcontroller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field

programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A processor may be a microprocessor or any conventional processor, controller, microcontroller, circuitry, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0037] The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module/firmware executed by a processor, or any combination thereof. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor.

[0038] The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0039] The disclosure also includes the following clauses:

E A finger cuff device to measure a patient’s blood pressure from an artery of the patient’s finger, the finger cuff device comprising:

a finger cuff including:

a cavity configured to receive the patient’s finger with the finger cuff extending around the patient’ s finger; and

a bladder included in the finger cuff, the bladder containing a fluid to apply a constant pressure to the patient’s finger; and

a pressure sensor in fluid communication with the fluid of the bladder, the pressure sensor configured to measure the pressure applied to the bladder by the patient’s artery to measure the arterial blood pressure of the finger. 2. The finger cuff device of claim 1, further comprising a processor connected to an optical source and sensor pair, the processor configured to extract the patient’s arterial blood pressure waveform signal from a plethysmography signal measured by the optical source and sensor pair, the patient’s arterial blood pressure waveform signal being extracted from the plethysmography signal based upon an equation relating the plethysmography signal to the blood flow in the finger and the arterial blood pressure of the finger.

3. The finger cuff device of any of the claims 1-2, wherein the pressure sensor is a pressure transducer.

4. The finger cuff device of claim 3, further comprising a connector tube that connects the fluid of the bladder to the pressure transducer.

5. The finger cuff device of any of the claims 1-4, further comprising a processor coupled to the pressure transducer, the processor configured to utilize pressure changes measured by the pressure transducer as a reference for an arterial waveform of the patient that is translated into the arterial blood pressure of the patient.

6. The finger cuff device of claim 5, wherein the processor implements an algorithm to appropriately scale the arterial blood pressure measurement of the finger to a heart level blood pressure measurement of the patient.

7. The finger cuff device of any of the claims 1-6, wherein the fluid of the bladder comprises an incompressible fluid, such that the incompressible fluid filled bladder applies an equal amount of constant pressure across the finger, such that the finger becomes a constant rigid form allowing a natural signal of the artery to penetrate the finger into the bladder to be measured by the pressure sensor.

8. The finger cuff device of any of the claims 1-7, wherein the fluid is a bio-blend oil.

9. The finger cuff device of any of the claims 1-8, wherein the pressure sensor is located in the finger cuff itself or at a location external to the finger cuff. 10. The finger cuff device of any of the claims 1-9, wherein the measured arterial blood pressure includes systolic pressure, mean arterial pressure (MAP), and diastolic pressure.

11. A method for measuring the blood pressure of a patient, the method comprising: applying, by a bladder, a constant pressure to a patient’s finger, wherein the patient’s finger is received in a cavity of a finger cuff; and

measuring, by a pressure sensor, the pressure applied to the bladder by the patient’s artery in their finger to measure the arterial blood pressure of the finger, wherein the pressure sensor is in fluid communication with the fluid of the bladder.

12. The method of claim 11, further comprising, extracting, by a processor, the patient’s arterial blood pressure waveform signal from a plethysmography signal measured by an optical source and sensor pair, the patient’s arterial blood pressure waveform signal being extracted from the plethysmography signal based upon an equation relating the plethysmography signal to the blood flow in the finger and the arterial blood pressure of the finger.

13. The method of any of the claims 11-12, wherein the pressure sensor is a pressure transducer.

14. The method of claim 13, wherein a connector tube connects the fluid of the bladder to the pressure transducer.

15. The method of any of the claims 11-14, wherein a processor is coupled to the pressure transducer, and the processor is configured to utilize pressure changes measured by the pressure transducer as a reference for an arterial waveform of the patient that is translated into the arterial blood pressure of the patient.

16. The method of claim 15, wherein the processor implements an algorithm to appropriately scale the arterial blood pressure measurement of the finger to a heart level blood pressure measurement of the patient. 17. The method of any of the claims 11-16, wherein the fluid of the bladder comprises an incompressible fluid, such that the incompressible fluid filled bladder applies an equal amount of constant pressure across the finger, such that the finger becomes a constant rigid form allowing a natural signal of the artery to penetrate the finger into the bladder to be measured by the pressure sensor.

18. The method of any of the claims 11-17, wherein the fluid is a bio-blend oil.

19. The method of any of the claims 11-18, wherein the pressure sensor is located in the finger cuff itself or at a location external to the finger cuff.

20. The method of any of the claims 11-19, wherein the measured arterial blood pressure includes systolic pressure, mean arterial pressure (MAP), and diastolic pressure.

21. A finger cuff device to measure a patient’s blood pressure from an artery of the patient’s finger, the finger cuff device comprising:

a finger cuff including:

a bladder included in the finger cuff, the bladder containing a fluid to apply a constant pressure to the patient’s finger;

a pressure transducer in fluid communication with the fluid of the bladder, the pressure sensor configured to measure the pressure applied to the bladder by the patient’s artery to measure the arterial blood pressure of the finger; and

a processor coupled to the pressure transducer, the processor configured to utilize pressure changes measured by the pressure transducer as a reference for an arterial waveform of the patient that is translated into the arterial blood pressure of the patient.

22. The finger cuff device of claim 21, further comprising extracting, by a processor, the patient’s arterial blood pressure waveform signal from a plethysmography signal measured by an optical source and sensor pair, the patient’s arterial blood pressure waveform signal being extracted from the plethysmography signal based upon an equation relating the plethysmography signal to the blood flow in the finger and the arterial blood pressure of the finger.

23. The finger cuff device of any of the claims 21-22, wherein the processor implements an algorithm to appropriately scale the arterial blood pressure measurement of the finger to a heart level blood pressure measurement of the patient.

24. The finger cuff device of any of the claims 21-23, wherein the fluid of the bladder comprises an incompressible fluid, such that the incompressible fluid filled bladder applies an equal amount of constant pressure across the finger, such that the finger becomes a constant rigid form allowing a natural signal of the artery to penetrate the finger into the bladder to be measured by the pressure transducer.

25. The finger cuff device of any of the claims 21-24, wherein the fluid is a bio-blend oil.

26. The finger cuff device of any of the claims 21-25, wherein the pressure transducer is located in the finger cuff itself or at a location external to the finger cuff.

27. The finger cuff device of any of the claims 21-26, wherein the measured arterial blood pressure includes systolic pressure, mean arterial pressure (MAP), and diastolic pressure.

Claims

WHAT IS CLAIMED IS:

1. A finger cuff device to measure a patient’s blood pressure from an artery of the patient’s finger, the finger cuff device comprising:

a finger cuff including:

a pressure sensor in fluid communication with the fluid of the bladder, the pressure sensor configured to measure the pressure applied to the bladder by the patient’s artery to measure the arterial blood pressure of the finger.

2. The finger cuff device of claim 1, further comprising a processor connected to an optical source and sensor pair, the processor configured to extract the patient’s arterial blood pressure waveform signal from a plethysmography signal measured by the optical source and sensor pair, the patient’s arterial blood pressure waveform signal being extracted from the plethysmography signal based upon an equation relating the plethysmography signal to the blood flow in the finger and the arterial blood pressure of the finger.

9. The finger cuff device of any of the claims 1-8, wherein the pressure sensor is located in the finger cuff itself or at a location external to the finger cuff.

10. The finger cuff device of any of the claims 1-9, wherein the measured arterial blood pressure includes systolic pressure, mean arterial pressure (MAP), and diastolic pressure.

16. The method of claim 15, wherein the processor implements an algorithm to appropriately scale the arterial blood pressure measurement of the finger to a heart level blood pressure measurement of the patient.

17. The method of any of the claims 11-16, wherein the fluid of the bladder comprises an incompressible fluid, such that the incompressible fluid filled bladder applies an equal amount of constant pressure across the finger, such that the finger becomes a constant rigid form allowing a natural signal of the artery to penetrate the finger into the bladder to be measured by the pressure sensor.

a finger cuff including:

a bladder included in the finger cuff, the bladder containing a fluid to apply a constant pressure to the patient’s finger; a pressure transducer in fluid communication with the fluid of the bladder, the pressure sensor configured to measure the pressure applied to the bladder by the patient’s artery to measure the arterial blood pressure of the finger; and