Patent Application
20180289271
Embodiments of the invention relate to a blood pressure measurement device that utilizes volume clamping and that is wearable by a patient.
Volume clamping is a technique for non-invasively measuring blood pressure in which pressure is applied to a subject's finger in such a manner that venous flow is fully obstructed and 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 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 conjunction with 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 subject's blood pressure.
Unfortunately, present finger cuff systems rely upon very large devices, such as, rotary pumps, blower pumps, and related devices, for the pressure generating system, to generate the pneumatic pressure for the volume clamp system. Such pump devices are comparatively much larger than the finger cuff itself and are located at distant locations to provide pressure to the finger cuff. As such, these types of pumps consume significant power and are physically removed from the patient thereby creating long air paths that hinder performance and that may result in inaccurate blood pressure measurements. Further, the large pump systems and supporting hardware expand clutter and hinder mobility in the hospital, emergency room, intensive care unit (ICU), doctor's office, ambulance, and other patient care locations. Moreover, this type of large pump system requires high energy consumption as a result of the continuously operating pump and provides further disadvantages as to noise due to the pump and the regular discharge of air. These attributes of high energy use, large components, and noise are undesirable in particular health care environments, such as ambulatory use, emergency rooms, intensive care unit (ICU), examination rooms, and in hospital rooms in which measurements are performed while a patient is sleeping.
Embodiments of the invention may relate to a blood pressure measurement device that utilizes volume clamping and that is wearable by a patient. The blood pressure measurement device may comprise: a finger cuff attachable to the patient's finger including a light emitting diode (LED)-photodiode (PD) pair to measure a pleth signal and a bladder surrounding the finger and a blood pressure measurement controller coupled to the bladder through a finger cuff connector to provide pneumatic pressure to the bladder. The blood pressure measurement controller may be wearable by the patient. The blood pressure measurement controller may include: a pump coupled to the finger cuff connector, a valve, a pressure sensor, and control circuitry coupled to the pump, the valve, the pressure sensor, and the LED-PD pair. The control circuitry may be configured to: control the pneumatic pressure applied by the pump through the finger cuff connector to the bladder to replicate the patient's blood pressure based upon measuring the pleth signal; control the opening of the valve to release pneumatic pressure from the bladder; and measure the patient's blood pressure by monitoring the pressure of the bladder with the pressure sensor.
Embodiments of the invention may relate to a pressure regulating feedback loop for volume clamp blood pressure measurement for use with a finger cuff. The feedback loop may contain a pump for generating pressure within a bladder of the finger cuff to compress a subject's artery and a valve for releasing pressure from the bladder. The feedback loop may further contain a pressure sensor that measures pressure within the bladder of the finger cuff and a system for measuring the volume of the clamped artery, such as, by utilizing an infrared light emitting diode (LED) and photodiode (PD).
In particular, embodiments of the invention may relate to a blood pressure measurement device that utilizes volume clamping and that is wearable by a patient. The blood pressure measurement device may comprise: a finger cuff attachable to the patient's finger including a light emitting diode (LED)-photodiode (PD) pair to measure a pleth signal and a bladder surrounding the finger and a blood pressure measurement controller coupled to the bladder through a finger cuff connector to provide pneumatic pressure to the bladder. The blood pressure measurement controller may also be wearable by the patient. The blood pressure measurement controller may include: a pump coupled to the finger cuff connector, a valve, a pressure sensor, and control circuitry coupled to the pump, the valve, the pressure sensor, and the LED-PD pair. As will be described, the control circuitry may be configured to: control the pneumatic pressure applied by the pump through the finger cuff connector to the bladder to replicate the patient's blood pressure based upon measuring the pleth signal; control the opening of the valve to release pneumatic pressure from the bladder; and measure the patient's blood pressure by monitoring the pressure of the bladder with the pressure sensor.
As will be described, according to embodiments of the invention, the finger cuff may be attached to a patient's finger and a blood pressure measurement controller including a pump, a valve, and a sensor may be coupled to the patient's finger, hand, wrist, arm, or other part of the patient's body, or may not be on the patient's body but may be in close proximity to the finger cuff, for a compact and energy efficient system to monitor a patient's blood pressure.
With reference to
Continuing with this example, as shown in
As can be seen in
Alternatively, the blood pressure measurement controller 120 may be placed not on the patient's body but may be placed or mounted in close proximity to the finger cuff 104. For example, the blood pressure measurement controller 120 may be clamped or attached to the arm rest 112 (e.g., placed on a clip or be velcroed) near the finger cuff 104 or may simply dangle off of the finger cuff 104 and may not be attached to anything. By having the blood pressure measurement controller 120 removed from the patient's body, access to a patient's arteries and veins is freed-up. Additionally, it should be appreciated that the approximately rectangular formation of the blood pressure measurement controller 120 shown in
As will be described in more detail hereafter, finger cuff 104 in conjunction with blood pressure measurement controller 120 that includes: a pump, a valve, a pressure sensor and control circuitry; may be utilized to measure the patient's blood pressure by monitoring the pressure of the bladder with the pressure sensor and may display the patient's blood pressure on the patient monitoring device 130. In particular, due to the small size of the finger cuff 104 and blood pressure measurement controller 120, techniques are provided to monitor a patient's blood pressure with a compact, mobile, energy efficient, and low noise system.
With additional reference to
Finger cuff 104 may include a light emitting diode (LED) 150 and a photodiode (PD) 152 to create an LED-PD pair. The finger cuff 104 including the LED-PD pair in cooperation with a bladder 156 that surrounds the finger and compresses or clamps against the patient's artery 160 may be used to measure a pleth signal to measure a patient's blood pressure, as will be described.
The blood pressure measurement controller 120 may be coupled to the bladder 156 of the finger cuff 104 through a finger cuff connector 175 to provide pneumatic pressure to the bladder 156. The blood pressure measurement controller 120 may include a pump 172, a valve 174, and a sensor 176. Further, blood pressure measurement controller 120 may include control circuitry 180 and input/output circuitry and interfaces 182, as will be described in more detail hereafter. As examples of interfaces, an interface to HRS connector 136 to HRS 134 and an interface to power/data cable 132 to patient monitoring device 130 may be utilized.
As has been described, the blood pressure measurement controller 120 may be wearable by a patient and may be mounted on patient's finger, hand, wrist, arm, or other part of the patient's body or may not be worn by the patient but may just be located locally to the finger cuff 104 (e.g., be placed on the arm rest, be dangling from the patient's finger, etc.). Further, as has been described, the blood pressure measurement controller 120 may be coupled to the finger cuff 104 by a finger cuff connector 175 which may be an appropriate connector 122 that includes a tube portion to provide pneumatic pressure from the pump 172 of the blood pressure measurement controller 120 to the bladder 156 of the finger cuff 104 (as well as a cable portion to provide the LED drive to the finger cuff and the pleth signal from the finger cuff 104 to the control circuitry 180) or by a connection fixture for directly connecting pneumatic pressure from the pump 172 of blood pressure measurement controller 120 to the bladder 156 of the finger cuff 104 (as well as to provide the pleth signal from the finger cuff 104 to the control circuitry 180) such that the blood pressure measurement controller 120 is mountable on top of the finger cuff 104. Thus, blood pressure measurement controller 120 may be connected locally by a tube or may be directly connected on top of the finger cuff 104 via a connection fixture upon a user's finger. These examples will be described in more detail hereafter. Also, it should be appreciated that the finger cuff connector 175 electronically connects the output of the LED-PD pair to the control circuitry 180.
Therefore, in one embodiment, blood pressure measurement controller 120 may include: a pump 172 including an air inlet 173 that is coupled to the finger cuff connector 175 to provide pneumatic pressure to the bladder 156; a valve 174 with a vent 177 coupled to the pneumatic pressure flow to release pneumatic pressure from the bladder 156; a pressure sensor 176 coupled to the pneumatic pressure flow to monitor the pneumatic pressure of the bladder 156; and control circuitry 180 coupled to the pump 172, valve 174, and sensor 176. It should be appreciated that the components of the blood pressure measurement controller 120 may be suitably contained and interconnected within the housing of the blood pressure measurement controller 120 shown in
The control circuitry 180 may be coupled to the pump 172, the valve 174, the sensor 176, and the LED-PD pair in order to control the bladder 156 of the finger cuff 104 and to measure the pleth signal from the LED-PD pair such that the control circuitry 180 of the blood pressure measurement controller 120 can measure a patient's blood pressure.
In particular, control circuitry 180 may be configured to: control the pneumatic pressure applied by the pump 172 (e.g., from air inlet 173) through the finger cuff connector 175 to the bladder 156 (e.g., denoted as output) 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, control circuitry 180 may be configured to: control the opening of the valve 174 via vent 177 to release pneumatic pressure from the bladder 156. Additionally, control circuitry 180 may be configured to: measure the patient's blood pressure by monitoring the pressure of the bladder 156 based upon the input from the pressure sensor 176, which should be the same as patient's blood pressure.
The patient's measured blood pressure may be commanded by control circuitry 180 to be transmitted through the I/O circuitry and interface 182 through data/power cable 132 to patient monitoring device 130 to display the patient's measured blood pressure. Further, control circuitry 180 based upon input from HRS 134 and other sources received through the I/O circuitry and interface 182 through HRS connector 136 may allow for compensation of potential errors due to differences in height between the finger cuff 104 and the heart level in the calculation of blood pressure measurements.
It should be appreciated that that control circuitry 180 of blood pressure measurement controller 120 may implement a computational algorithm to control the pneumatic pressure applied by the pump 172 (e.g., output) through the finger cuff connector 175 to the bladder 156 to replicate the patient's blood pressure based upon the measured pleth signal received from the LED-PD pair of the finger cuff 104 in conjunction with controlling the opening of the valve 174 to release pneumatic pressure from the bladder 156 and measuring the patient's blood pressure by monitoring the pressure of the bladder 156 with the pressure sensor 176 and at the same time commanding the calculated blood pressure measurement to be displayed by the patient monitoring device 130. Further, it should be appreciated that the pneumatic pressure applied via the pump 172 may be a suitable gas, such as, air, or in other implementation may utilize a suitable liquid.
With additional reference to
Examples of the types of operations implemented by the finger cuff 104 and blood pressure measurement controller 120 will be hereafter described.
With additional reference to
In particular, as can be seen in
With additional reference to
With additional reference to
It should be appreciated that various types of pumps 172 may be utilized to implement the previously described embodiments of the invention. For example, in one embodiment, a piezoelectric pump may be utilized as pump 172. A piezoelectric pump 172 may be of relatively small size, low power consumption, and may operate at high operating frequencies well outside of the human auditory range. Therefore, the piezoelectric pump 172 being of small size and low power consumption is suitable for use in the previously described blood pressure measurement controller 120 that is easily mountable on a patient's finger, hand, wrist, etc., as previously described, in very close proximity to the finger cuff 104. Also, since a piezoelectric pump 172 is relatively quiet it does not interfere with a patient's sleep. Additionally, the piezoelectric pump's 172 ability to be modulated (e.g., quickly turned on and off) to control the pneumatic pressure applied to the bladder 156 of the finger cuff 104 may further minimize power usage and maximize control and efficiency.
Other types of pumps 172 that are of small size, low power consumption, and low sound may also be utilized, such as: a voice coil pump, a piston pump, a diaphragm pump, an electrolytic pump, or a peristaltic pump. These types of pumps may be utilized with these same types of advantages as the piezoelectric pump.
In one embodiment, valve 174 may be a piezoelectric valve including a vent 177. Piezoelectric valves, similar to the piezoelectric pump, have the advantages of small size, low power consumption, and high actuation speeds. As one particular example, piezoelectric valve 177 may include a piezoceramic actuator section, a fixed beam section connected to the piezoceramic actuator section, and a rubber sleeve portion connected to the fixed beam section. The piezoceramic actuator section, the fixed beam section, and the rubber sleeve portion may be connected linearly and the rubber sleeve portion may extend over the vent 177. In this way, the valve command signal from the control circuitry 180 may the cause the movement/actuation of the piezoceramic actuator section such that the rubber sleeve portion moves away from the vent 177 (opening) or over the vent 177 (closing) to control the opening and the closing of the vent. As previously described, as an example, a command signal (0-1) may be sent commanding how much the piezoelectric valve should be opened (e.g., how much the piezoceramic actuator section should be commanded to be moved/actuated to simultaneously move the rubber sleeve portion away from the vent to open the vent). It should be appreciated that this is just one example. Other types of valves that have similar characteristics of a piezoelectric valve (e.g., small size, low power consumption, and high actuation speeds), such as, a solenoid valve, an electromechanical valve, etc. It should be appreciated that any type of suitable valve may be utilized.
Various examples will be hereafter described that may be used to implement the previously described blood pressure measurement device that is wearable by a patient.
For example,
As can be seen in
In this example, in which, the finger cuff connector 175 may be an appropriate connector 122 to provide the pneumatic pressure from the pump 172 of the blood pressure measurement controller 120 to the bladder 156 of the finger cuff 104, the operation of the blood controller pressure measurement controller 120 proceeds, as previously described. In particular, control circuitry 180 may be configured to: control the pneumatic pressure applied by the pump 172 (e.g., from air inlet 173) through the connector 122 to the bladder 156 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, control circuitry 180 may be configured to: control the opening of the valve 174 to release pneumatic pressure from the bladder 156. However, in some embodiments, as previously described, a valve controlled by control circuitry 180 to open and close to release pneumatic pressure from the bladder 156 is not utilized, and a fixed orifice not controlled by controlled circuitry 180, to passively release pneumatic pressure from the bladder 156 may be utilized. Additionally, control circuitry 180 may be configured to: measure the patient's blood pressure by monitoring the pressure of the bladder 156 based upon the input from the pressure sensor 176, which should be the same as patient's blood pressure. The patient's measured blood pressure may be commanded by the control circuitry 180 to be transmitted through the I/O circuitry and interface 182 through data/power cable 132 to the patient monitoring device 130 to display the patient's measured blood pressure. Further, control circuitry 180 based upon input from HRS 134 and other sources received through the I/O circuitry and interface 182 through HRS connector 136 may allow for compensation of potential errors due to differences in height between the finger cuff 104 and the heart level in the calculation of blood pressure measurements.
As another example, with reference to
As can be seen in
In this example, in which, the finger cuff connector 175 may be a connection fixture to provide the pneumatic pressure from the pump 172 of the blood pressure measurement controller 120 to the bladder 156 of the finger cuff 104, the operation of the blood pressure measurement controller 120 proceeds, as previously described. In particular, control circuitry 180 may be configured to: control the pneumatic pressure applied by the pump 172 (e.g., from air inlet 173) through the connection fixture 175 to the bladder 156 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, control circuitry 180 may be configured to: control the opening of the valve 174 to release pneumatic pressure from the bladder 156. However, in some embodiments, as previously described, a valve controlled by control circuitry 180 to open and close to release pneumatic pressure from the bladder 156 is not utilized, and a fixed orifice not controlled by controlled circuitry 180, to passively release pneumatic pressure from the bladder 156 may be utilized. Additionally, control circuitry 180 may be configured to: measure the patient's blood pressure by monitoring the pressure of the bladder 156 based upon the input from the pressure sensor 176, which should be the same as patient's blood pressure. The patient's measured blood pressure may be commanded by the control circuitry 180 to be transmitted through the I/O circuitry and interface 182 through data/power cable 132 to the patient monitoring device 130 to display the patient's measured blood pressure. Further, control circuitry 180 based upon input from HRS 134 and other sources received through the I/O circuitry and interface 182 through HRS connector 136 may allow for compensation of potential errors due to differences in height between the finger cuff 104 and the heart level in the calculation of blood pressure measurements.
It should be appreciated that various other alternative implementations may be utilized. For example, in one alternative implementation, the valve 174 may simply be a fixed orifice to release pneumatic pressure from the bladder 156. In this implementation, the opening and closing of the valve 174 will therefore not be controlled by the control circuitry 180, as previously described, as it is simply an orifice. In this instance, pneumatic pressure applied to the bladder 156 will be completely controlled and modulated by the pump 172 as controlled by the control circuitry 180. In another implementation, backward leakage of pneumatic pressure out of the pump 172 may be allowed when the pump 172 is powered off to allow for the release of pneumatic pressure from the bladder 156.
Also, although a wired data cable 132 has been illustrated to transmit the measured patient's blood pressure through a wired connection to the patient monitoring device 130, it should be appreciated that a wireless connection may be utilized to transmit data to and from the patient monitoring device 130 instead of a wired connection.
As previously described, blood pressure measurement device 102 utilizing a finger cuff 104 in conjunction with a relatively small and compact blood pressure measurement controller 120 that includes: an internal controllable valve 174, an internal controllable pump 172, and a sensor 176; enables a very compact pressure drive system and feedback loop for a continuous non-invasive blood pressure monitoring system. Further, this type of blood pressure measurement device 102 may simply be located on the patient's wrist, hand, or finger, or may be located in close proximity thereto (e.g., the blood pressure measurement controller 120 may be mounted to a nearby fixture near the finger cuff 104 or may dangle from the finger cuff 104).
Moreover, the compact size of the internal controllable pump 172 (e.g., a piezoelectric pump) and the internal controllable valve 174 (e.g., a piezoelectric valve) being utilized in the blood pressure measurement controller 120 closely coupled to the finger cuff 104 such that the blood pressure measurement device 102 is mountable to patient's finger, hand, wrist, etc., enables a continuous blood pressure measurement system that is portable and can be worn continuously by a patient as the patient moves through the hospital (e.g., from operating room (OR) to intensive care unit (ICU)), or from an ambulance to the emergency room (ER), ICU, etc., or between any locations in a hospital, medical, or home environment, etc. Therefore, by utilizing an internal controllable pump 172 (e.g., a piezoelectric pump) and an internal controllable valve 174 (e.g., a piezoelectric valve) in the blood pressure measurement device 102, a small, compact, and portable blood pressure measurement system is provided. This type of more compact blood pressure measurement device has various advantages as to current systems, such as: provides a high-fidelity feedback loop; is less obtrusive in the OR, ER, ICU, etc.; is of lower cost; is very portable; utilizes less energy; creates less sound—is quieter; etc. In particular, in one implementation, the small size and lightweight of the previously described blood pressure measurement device allows for the easy movability of the patient around a medical facility, as well as, in and out of the medical facility.
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., such as control circuitry 180, I/O circuitry 182, etc. As an example, control circuitry 180 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.
| Number | Date | Country | |
|---|---|---|---|
| 62484092 | Apr 2017 | US |
