Patent Application
20190104991
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 and snugness or tightness 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 wrappable portion that wraps around a patient's finger. The wrappable portion includes a bladder and a light emitting diode (LED) and photodiode (PD) pair. The finger cuff further comprises a plurality of tubules mountable on an exterior of the wrappable portion. The tubules are inflatable to provide pressure to the wrappable portion of the finger cuff to the patient's finger and to provide tightness of the wrappable portion of the finger cuff to the patient's finger. When the finger cuff is placed around the patient's finger, the bladder and the LED-PD pair 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 circuitry. 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 sensor, 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
In one embodiment, for attachment purposes to a patient's finger, finger cuff 400 may utilize a latching mechanism, for example a releasable tie wrap (or cable tie) fastening system (i.e., a tie wrap system that may be closed/locked in place and may thereafter be released), to latch the wrapping portion 410 to the patient's finger. For example, as shown, the first side of the wrapping portion 410 may include a head 465 and the second side of the wrapping portion 410 may include an elongated strap 460 (which may be formed of flexible material, e.g., nylon). The head 465 may include a strap entrance end 412 for insertion of the strap 460. Although not shown, in some embodiments, head 465 may include a locking device with a release tab. In some embodiments, as shown in
In operation, strap 460 may be pulled (e.g., by a healthcare provider) towards head 465 so that finger cuff 400 comfortably (or snuggly) fits around a patient's finger, and a tip of the strap 460 may be inserted through the strap entrance end 412. The locking device of head 465 may engage with a selected tooth 470 of the locking teeth so as to lock or secure the strap 460 in position within the head 465. Subsequently, to release strap 460 from head 465, the release tab may be activated to allow strap 460 to move in a release direction (e.g., a direction away from head 465), thereby permitting strap 460 to be removed or adjusted as desired.
Although a releasable tie wrap fastening system is illustrated in
As particularly shown in
As further shown in
Operationally, after the wrapping portion 410 is secured around a patient's finger (e.g., using the releasable tie wrap fastening system, as previously described), tubules 450 may be inflated (e.g., filled with a liquid or gas) to exert pressure and form tightness around the patient's finger so that finger cuff 400 effectively (or comfortably) fits around the patient's finger. Accordingly, the tightness or snugness of the finger cuff 400 around the patient's finger is dependent on the pressure provided to the tubules 450. Therefore, the tightness or snugness of the finger cuff 400 can be standardized by applying standardized pressure to the tubules 450 providing a snug or tight fit to the patient's finger improving the accuracy of the blood pressure measurement by the finger cuff.
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 adjustment ability of the latching mechanism and the pressure exerted by tubules 450, 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 almost any size finger.
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 circuitry 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 priority to U.S. Provisional Application No. 62/571,098, filed Oct. 11, 2017, the contents of which are incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62571098 | Oct 2017 | US |
