Patent Application
20190082982
Embodiments of the invention relate generally to non-invasive blood pressure measurement. More particularly, embodiments of the invention relate to a finger cuff for blood pressure measurement.
Volume clamping is a technique for non-invasively measuring blood pressure 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 equal 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.
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.
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 are 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.
Today, finger cuff based blood pressure monitoring devices generally use the same technology (e.g., photoplethysmography or similar technologies) to measure blood pressure. Unfortunately, such finger cuff devices may not be easily attachable to a patient's finger and may not be that accurate due to the finger cuff's positioning on the patient's finger.
Embodiments of the invention may relate to a finger cuff that is attachable to a patient's finger to be used in measuring the patient's blood pressure by a blood pressure measurement system utilizing a volume clamp method. The finger cuff comprises a bladder configured to exert pressure on the patient's finger. The finger cuff further comprises a plurality of light emitting diodes (LEDs) and a plurality of photodiodes (PDs) that respectively align with one another to form a plurality of LED-PD pairs. When the finger cuff is placed around the patient's finger, the bladder and the plurality of LED-PD pairs aid in measuring the patient's blood pressure by the blood pressure measurement system utilizing the volume clamp method.
With reference to
The blood pressure measurement system 102 may further be connected to a patient monitoring device 130, and, in some embodiments, a pump 134. Further, finger cuff 104 may include a bladder (not shown) and an LED-PD pair (not shown), which are conventional for finger cuffs.
In one embodiment, the blood pressure measurement system 102 may include a pressure measurement controller 120 that includes: a small internal pump, a small internal valve, a pressure sensor, and control circuity. In this embodiment, the control circuitry may be configured to: control the pneumatic pressure applied by the internal pump to the bladder of the finger cuff 104 to replicate the patient's blood pressure based upon measuring the pleth signal received from the LED-PD pair of the finger cuff 104. Further, the control circuitry may be configured to: control the opening of the internal valve to release pneumatic pressure from the bladder; or the internal valve may simply be an orifice that is not controlled. Additionally, the control circuitry may be configured to: measure the patient's blood pressure by monitoring the pressure of the bladder based upon the input from a pressure senor, which should be the same as patient's blood pressure, and may display the patient's blood pressure on the patient monitoring device 130.
In another embodiment, a conventional pressure generating and regulating system may be utilized, in which, a pump 134 is located remotely from the body of the patient. In this embodiment, the blood pressure measurement controller 120 receives pneumatic pressure from remote pump 134 through tube 136 and passes on the pneumatic pressure through tube 123 to the bladder of finger cuff 104. Blood pressure measurement device controller 120 may also control the pneumatic pressure (e.g., utilizing a controllable valve) applied to the finger cuff 104 as well as other functions. In this example, the pneumatic pressure applied by the pump 134 to the bladder of finger cuff 104 to replicate the patient's blood pressure based upon measuring the pleth signal received from the LED-PD pair of the finger cuff 104 (e.g., to keep the pleth signal constant) and measuring the patient's blood pressure by monitoring the pressure of the bladder may be controlled by the blood pressure measurement controller 120 and/or a remote computing device and/or the pump 134 and/or the patient monitoring device 130 to implement the volume clamping method. In some embodiments, a blood pressure measurement controller 120 is not used at all and there is simply a connection from tube 136 from a remote pump 134 including a remote pressure regulatory system to finger cuff 104, and all processing for the pressure generating and regulatory system, data processing, and display is performed by a remote computing device.
Continuing with this example, as shown in
As can be seen in
Further, finger cuff 300 may include a bladder 340 and an LED-PD pair 335a-b mounted on the interior of the finger cuff 300. In one embodiment, the bladder 340 may include a pair of openings that surround the LED-PD pair 335a-b, respectively. The bladder 340 and LED-PD pair 335a-b may be coupled to tube or cable 360 through a connector, which may be attached to finger cuff 300, to provide pneumatic pressure to the bladder 340, and to provide power to and receive data from the LED-PD pair 335a-b. The LED-PD pair 335a-b may be used to perform measurements of a pleth signal to aid in measuring the patient's blood pressure.
With additional reference to
For example, in
With respect to the conventional finger cuff 300, previously described, it is generally available in different sizes (e.g., small, medium, large), and includes differently sizes bladders 340 (depending on the size of the finger cuff 300). The distance between the LED 335a and the PD 335b (which may be referred to as “x”), therefore, may vary depending on the size of the finger cuff and bladder to meet the different finger sizes and finger physiology of the patient. In applying the finger cuff 300 on a patient's finger (e.g., finger 310), it is important for a healthcare provider to select a suitable finger cuff size for the patient such that the LED-PD pair 335a-b is properly and effectively positioned on the patient's finger in order to obtain an accurate optical measurement. However, the various sized conventional finger cuffs 300 may not be suitable for the finger sizes and physiology of many patients such that inadequate finger cuff attachments by health care providers may occur. In such circumstances, the LED-PD pair 335a-b may not be properly positioned on the patient's finger, and therefore, the PD 335b may not adequately detect or register light signals from the LED 335a (as shown in
Embodiments shown in
With reference to
As shown in
Operationally, LED 425a and LED 435a may concurrently, alternatively, or in pre-defined sequences, transmit or emit light in different directions through finger arteries 330. In this scenario, the light from the LED 425a and LED 435a may be detected and registered by one or both of PD 425b and PD 435b (depending on the directions of the light) to generate a pleth signal from each PD 425b and PD 435b to create a more accurate optimal quality pleth signal. For example, each of the pleth signals generated may be averaged, or another type of algorithm may be utilized, to combine the pleth signals to generate an optimal quality pleth signal. Therefore, the additional LED-PD pair (e.g., LED-PD pair 435a-b) is utilized for additional light signal recognition and the increased number of light signals (e.g., pleth signals) transmitted through the finger arteries 330 and received by the PDs may result in increased signal quality and, in particular, may be utilized to generate an optimal quality pleth signal. Accordingly, an optimal quality pleth signal may be generated from the pleth signals received from the LED-PD pair 425a-b and LED-PD pair 435a-b.
As an example, as part of the volume clamp method, the pneumatic pressure is applied to the bladder 440 of the finger cuff based upon measuring the pleth signals received from the LED-PD pair 425a-b and LED-PD pair 435a-b of the finger cuff (e.g., to keep the optimal quality pleth signal constant) so that the pressure applied to the bladder 440 and measured by a pressure sensor should be correlated to the patient's blood pressure.
In another embodiment, with reference to
It should be appreciated that the operational aspects of
As an example, as part of the volume clamp method, the pneumatic pressure is applied to the bladder 440 of the finger cuff based upon measuring the pleth signals received from the PDs 455 of the finger cuff (e.g., to keep the optimal quality pleth signal constant) so that the pressure applied to the bladder 440 and measured by a pressure sensor should be correlated to the patient's blood pressure.
It should be noted that in these previously described embodiments, in which, multiple LED-PD pairs are utilized for pleth signal detection, an optimal location (both horizontally and vertically) for the finger cuff 400 on the patient's finger 310 in relation to the finger arteries 330 may be determined (e.g., by a health care provider) in order to perform blood pressure measurement (as shown in
With the previously described embodiments, the application of the finger cuff 400 to a patient's finger by a healthcare provider is less susceptible to application errors. Further, the finger cuff 400, with the increased ability to find an optimal quality pleth signal, allows for the finger cuff 400 to be single-sized or a one-size-fits-all finger cuff, such that different finger cuff sizes (as previously discussed with respect to finger cuff 300) do not need to be utilized and a single sized finger cuff 400 may be utilized for most any size finger. It should be appreciated that while LEDs and PDs are illustrated in
It should be appreciated that aspects of the invention previously described may be implemented in conjunction with the execution of instructions by processors, circuitry, controllers, control circuitry, etc. As an example, control circuity may operate under the control of a program, algorithm, routine, or the execution of instructions to execute methods or processes in accordance with embodiments of the invention previously described. 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 processors, control circuitry, 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 of the invention.
The various illustrative logical 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.
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.
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.
This application claims the benefit of U.S. Provisional Application No. 62/561,072, filed Sep. 20, 2017, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62561072 | Sep 2017 | US |
