Patent Description:
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 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 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, many finger cuffs use a type of flexible band that wraps around a patient's finger and then utilize a conventional method to close or secure the finger cuff to the finger, such as, Velcro, or other securing means. Unfortunately, these types of finger cuffs are difficult to use by healthcare providers and also introduce attachment errors, such as, rotation errors, wrong orientation errors, lack of snugness errors, etc. These attachment errors then negatively impact the accuracy of the blood pressure measurement.

<CIT> describes blood pressure sensing means comprising an arcuate base plate, a hollow cuff, a luminescent diode, a photodiode, a force sensor, soft U-shaped circuit boards and a wiring board.

<CIT> describes a sensor system for continuous non-invasive arterial blood pressure (CNAP) that comprises a base portion and a detachable and disposable portion. The base portion is connected to a control system. The disposable portion is for attachment to a human body part. The CNAP sensor system includes a photo-plethysmographic (PPG) system having at least one light source, at least one light detector, electrical supplies, light coupling systems, one or more connectors, and a cuff including air supplies.

<CIT> describes an inflatable cuff for encircling a patient's finger and which includes a light source and a light detector constructed in a way to detect the movement, or lack of movement, of arterial passages within the finger. The cuff is comprised of an inflatable bladder that contacts the patient finger; having a tubing provided for inflation and deflation of the bladder. Surrounding the external surface of the bladder from the finger is a metalized backing that covers and shields the inflatable bladder. A flexible circuit is affixed to the metalized backing and to which is attached the light source and light detector and which further includes wiring from the light detector and light source to a connector at its distal end for connection to further circuiting. Further, surrounding the flexible circuit is a electrical and light shielding and label that covers the flexible circuit and which provides shielding as well as a means of affixing the inflatable cuff to the patients finger.

The present invention relates to a finger cuff as defined in appended claim <NUM> and a method as defined in appended claim <NUM>. The finger cuff of the invention is connectable to a patient's finger to aid in measuring the patient's blood pressure by a blood pressure measurement system. The finger cuff comprises: a shell, a bladder, and a clamping mechanism. The has a finger cavity and a pair of opposed first and second top portions. The finger cavity of the shell is configured to be placed under a patient's finger to receive the patient's finger. Further, the finger cavity includes a light emitting diode (LED) - photodiode (PD) pair. The bladder includes a pair of openings in the form of a pair of indendations that open towards the finger cavity and the bladder is mountable within the finger cavity such that the pair of openings receive and circumferentially surround the LED-PD pair, respectively. The clamping mechanism is coupled to the opposed first and second top portions of the shell. The clamping mechanism is used to suitably clamp the patient's finger received in the finger cavity of the shell against the bladder mounted within the finger cavity of the shell, such that, the bladder and the LED-PD pair aid in measuring the patient's blood pressure by the blood pressure measurement system.

With reference to <FIG>, an example of an environment in which a finger cuff <NUM> may be implemented will be described. As an example, a blood pressure measurement system <NUM> that includes a finger cuff <NUM> that may be attached to a patient's finger <NUM> and a blood pressure measurement controller <NUM> that may be attached to the patient's body (e.g., a patient's wrist or hand) is shown. The blood pressure measurement system <NUM> may further be connected to a patient monitoring device <NUM>, and, in some embodiments, a pump <NUM>. Further, finger cuff <NUM> 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 <NUM> may include a pressure measurement controller <NUM> 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 <NUM> to replicate the patient's blood pressure based upon measuring the pleth signal received from the LED-PD pair of the finger cuff <NUM>. Further, the control circuitry may be configured to: control the opening of the internal valve to release pneumatic pressure; 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 <NUM>.

In another embodiment, a conventional pressure generating and regulating system may be utilized, in which, a pump <NUM> is located remotely from the body of the patient. In this embodiment, the blood pressure measurement controller <NUM> receives pneumatic pressure from remote pump <NUM> through tube <NUM> and passes on the pneumatic pressure through tube <NUM> to the bladder of finger cuff <NUM>. Blood pressure measurement device controller <NUM> may also control the pneumatic pressure (e.g., utilizing a controllable valve) applied to the finger cuff <NUM> as well as other functions. In this example, the pneumatic pressure applied by the pump <NUM> to the bladder of finger cuff <NUM> to replicate the patient's blood pressure based upon measuring the pleth signal received from the LED-PD pair of the finger cuff <NUM> and measuring the patient's blood pressure by monitoring the pressure of the bladder may be controlled by the blood pressure measurement controller <NUM> and/or a remote computing device and/or the pump <NUM> and/or the patient monitoring device <NUM>. In some embodiments, a blood pressure measurement controller <NUM> is not used at all and there is simply a connection from the tube <NUM> to finger cuff <NUM> from a remote pump <NUM> including a remote pressure regulatory system, 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 <FIG>, a patient's hand may be placed on the face <NUM> of an arm rest <NUM> for measuring a patient's blood pressure with the blood pressure measurement system <NUM>. The blood pressure measurement controller <NUM> of the blood pressure measurement system <NUM> may be coupled to a bladder of the finger cuff <NUM> in order to provide pneumatic pressure to the bladder for use in blood pressure measurement. Blood pressure measurement controller <NUM> may be coupled to the patient monitoring device <NUM> through a power/data cable <NUM>. Also, in one embodiment, as previously described, in a remote implementation, blood pressure measurement controller <NUM> may be coupled to a remote pump <NUM> through tube <NUM> to receive pneumatic pressure for the bladder of the finger cuff <NUM>. The patient monitoring device <NUM> 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, power/data cable <NUM> may transmit data to and from patient monitoring device <NUM> and also may provide power from the patient monitoring device <NUM> to the blood pressure measurement controller <NUM> and finger cuff <NUM>.

As can be seen in <FIG>, in one example, the finger cuff <NUM> may be attached to a patient's finger and the blood pressure measurement controller <NUM> may be attached on the patient's hand or wrist with an attachment bracelet <NUM> that wraps around the patient's wrist or hand. The attachment bracelet <NUM> may be metal, plastic, Velcro, etc. It should be appreciated that this is just one example of attaching a blood pressure measurement controller <NUM> and that any suitable way of attaching a blood pressure measurement controller to a patient's body or in close proximity to a patient's body may be utilized and that, in some embodiments, a blood pressure measurement controller <NUM> may not be used at all. It should further be appreciated that the finger cuff <NUM> may be connected to a blood pressure measurement controller described herein, or a pressure generating and regulating system of any other kind, such as a conventional pressure generating and regulating system that is located remotely from the body of the patient (e.g., a pump <NUM> located remotely from a patient). Any kind of pressure generating and regulating system that can be used, including but not limited to the blood pressure measurement controller, may be described simply as a pressure generating and regulating system. As a further example, in some embodiments, there may be no blood pressure measurement controller, at all, and a remote pump <NUM> that is controlled remotely may be directly connected via a tube <NUM> and <NUM> to finger cuff <NUM> to provide pneumatic pressure to the finger cuff <NUM>.

In particular, as will be described in more detail hereafter, embodiments of the invention may relate to a finger cuff <NUM> that is connectable to a patient's finger <NUM> to aid in measuring the patient's blood pressure by the blood pressure measurement system <NUM>. As will be described in more detail hereafter, the finger cuff <NUM> may comprise a shell, a bladder, and a clamping mechanism. The shell may have a finger cavity and a pair of opposed first and second top portions. The finger cavity of the shell may be placed under the patient's finger <NUM> to receive the patient's finger. The finger cavity may include a light emitting diode (LED) - photo diode (PD) pair (not shown). As will be described, the bladder (not shown) may include a pair of openings. The bladder may be mountable within the finger cavity such that the pair of openings surround the LED-PD pair, respectively. The clamping mechanism (not shown) may be coupled to the opposed first and second top portions of the shell. In particular, the clamping mechanism may be used to suitably clamp the patient's finger <NUM> received in the finger cavity of the shell against the bladder mounted within the finger cavity of the shell such that the bladder and the LED-PD pair aid in measuring the patient's blood pressure by the blood pressure measurement system <NUM> utilizing the volume clamping method.

With additional reference <FIG>, embodiments of the invention related to the shell finger cuff will be particularly described. As has been described, finger cuff <NUM> may be connectable to a patient's finger <NUM> to aid in measuring the patient's blood pressure by the previously described blood pressure measurement system <NUM> utilizing the volume clamping method. As can be seen in these figures, finger cuff <NUM> may particularly comprise: a shell <NUM>; a bladder (as will be described in more detail hereafter); and a clamping mechanism <NUM>.

Looking particularly at the shell <NUM>, the shell <NUM> may be approximately arch-shaped and may have a finger cavity <NUM> and a pair of opposed first and second top portions <NUM>. In particular, as can be seen in these figures, the finger cavity <NUM> of the shell <NUM> may be placed under a patient's finger <NUM> to receive the patient's finger <NUM> such that the half open shape formed by the shell <NUM> makes it easy to put the patient's finger in.

Also, the finger cavity <NUM> may include a LED-PD pair <NUM> and <NUM> (see particularly <FIG>). As will be described in more detail hereafter, the bladder may include a pair of openings such that the bladder may be mountable within the finger cavity <NUM>, such that, the pair of openings surround the LED-PD pair <NUM> and <NUM>. As can be particularly seen in <FIG>, in conjunction with <FIG>, <FIG>, the shell <NUM> may include a lower section <NUM> that includes the LED-PD pair <NUM> and <NUM>. This lower section <NUM> that includes the LED-PD pair <NUM> and <NUM> may be made from a more flexible material to provide flexibility in accommodating the patient's finger <NUM>. Such type of flexible material may include a polyvinyl chloride (PVC) material or any suitably flexible material. It should be appreciated that the flexible material of the lower section <NUM>, although flexible to accommodate the patient's finger, is rigid enough to form the cavity <NUM>, when not in use. Also, the lower section <NUM> closely follows the lower side of the patient's finger reducing bladder volume which is beneficial for the servo performance of the volume clamp system. On the other hand, the shell <NUM> may also include a higher section <NUM> that includes the opposed first and second top portions <NUM>. The opposed top portions <NUM> may be made of a more rigid material to accommodate the clamping mechanism <NUM>, as will be described in more detail hereafter. It should be appreciated that any suitable sort of rigid material, such as, a metallic material, may be utilized.

Details of the clamping mechanism <NUM> will now be described in more detail with reference to <FIG>. In one embodiment, the clamping mechanism <NUM> may be coupled to the opposed first and second top portions <NUM> of the shell <NUM>. The clamping mechanism <NUM> may be used to suitably clamp the patient's finger <NUM> received in the finger cavity <NUM> of the shell <NUM> against the bladder mounted within the finger cavity <NUM> such that the bladder and the LED-PD pair <NUM> and <NUM> may be used to aid in measuring the patient's blood pressure by the blood pressure measurement system <NUM> utilizing the volume clamping method.

In one particular embodiment, the clamping mechanism <NUM> may include a pulling and closing mechanism that comprises a flexible material <NUM> having a first end and a second end. In one embodiment, the flexible material <NUM> may be considered a flap or a strap. The first end of the flexible material <NUM> may be permanently mounted to the first top portion <NUM> of the shell <NUM>. For example, the flexible material <NUM> may be mounted to a first slot of the first top portion <NUM> of the shell <NUM>. Further, the second end <NUM> of the flexible material <NUM> may be extendable through a second slot <NUM> of the second top portion <NUM> of the shell <NUM> such that the second end <NUM> may be pulled by a healthcare provider through the second slot <NUM> such that the flexible material <NUM> clamps the patient's finger <NUM> securely within the finger cavity <NUM> of the shell <NUM>. It should be appreciated that the slots are formed in the opposed rigid top sections <NUM> to provide strength for the clamping mechanism. Further, thereafter, a bottom portion of the flexible material <NUM> near the second end <NUM> may be affixed to a remainder of the flexible material <NUM> (e.g., on the top of the flexible material <NUM>) such that the flexible material <NUM> is locked in place and secures the patient's finger <NUM> within the finger cuff <NUM> for more accurate blood pressure measurements. As an example, Velcro portions on the bottom portion of the flexible material <NUM> near the second end <NUM> and on the top portion of the flexible material <NUM> may connect together to lock the flexible material in place (e.g., see <FIG>). In this way, a tight fit of the finger <NUM> to the finger cuff <NUM> is ensured. Also, by having a tight fit with the clamping mechanism <NUM>, the air pressure from the bladder is efficiently transferred to the finger artery. Also, although a Velcro implementation is provided as an example to lock the flexible material <NUM> in place, it should be appreciated that other affixing means may be utilized such as glue, tape, adhesives, etc..

In particular, by utilizing the shell <NUM> that extends around a patient's finger <NUM>, that guides the finger <NUM> in, and, that, is then secured in place by the clamping mechanism <NUM>, such that a snug fit is provided, orientation and rotation errors due to the movement of the finger are avoided, and more accurate blood pressure measurements can be taken by the volume clamp method of the blood pressure measurement system <NUM>. In particular, with the clamping mechanism <NUM> firmly clamping the patient's finger <NUM> received in the finger cavity <NUM> of the shell <NUM> against the bladder mounted within the finger cavity <NUM> of the shell <NUM>, the bladder (being provided pneumatic pressure through the tube <NUM>) and the LED-PD pair <NUM> and <NUM>, may be more accurately utilized in measuring the patient's blood pressure by the volume clamp method of the blood pressure measurement system <NUM>. Additionally, the shell <NUM> being formed with a rigid higher section and a more flexible lower section may be molded such that it is efficient to manufacture and easy to mount the optical components and bladder to the lower section.

With additional reference <FIG>, in one embodiment, a bladder <NUM> that is fully inflatable may be utilized. Bladder <NUM> may be connected to tube <NUM> for receiving pneumatic pressure. Further, bladder <NUM> may include a pair of circular openings <NUM> and <NUM> such that bladder <NUM> may be mounted within the finger cavity <NUM> to the shell <NUM> such that the pair of openings <NUM> and <NUM> surround the LED-PD pair <NUM> and <NUM>, respectively. Thus, the two openings <NUM> and <NUM> particularly align and surround the LED-PD pair <NUM> and <NUM> to allow for the bladder to inflate and deflate within the finger cavity <NUM> of the shell <NUM>. Also, this type of bladder <NUM> provides a full volume of air, as shown in <FIG>, which is a more efficient implementation of air volume than previous types of bladders. As has been described, with the clamping mechanism <NUM> firmly clamping the patient's finger <NUM> received in the finger cavity <NUM> of the shell <NUM> against the bladder <NUM> mounted within the finger cavity <NUM> of the shell <NUM>, the bladder <NUM> and the LED-PD pair <NUM> and <NUM> may be more accurately utilized in measuring the patient's blood pressure by the volume clamp method of the blood pressure measurement system <NUM>.

It should be appreciated that the shell <NUM>, the LED-PD pair <NUM> and <NUM>, and the clamping mechanism <NUM> of the finger cuff <NUM> may be re-usable. Further, although bladder <NUM> may also be re-usable it may also be disposable and replaceable. Thus, in one embodiment, bladder <NUM> is disposable and replaceable such that a new bladder <NUM> may be mountable within the finger cavity <NUM> of the shell <NUM> of the finger cuff <NUM> so that the pair of openings <NUM> and <NUM> surround the LED-PD pair <NUM> and <NUM>, respectively. Thus, in some embodiments, the shell <NUM> and clamping mechanism <NUM> of finger cuff <NUM> are re-usable and the bladder <NUM> may be disposable and replaceable. By utilizing this type of disposable and replaceable implementation of the bladder <NUM> with the re-usable finger cuff <NUM> (shell <NUM> and clamping mechanism <NUM>), significant cost savings may be realized due to the fact that the key components of the finger cuff <NUM> are not completely disposable and may be re-used. In fact, the main components of the finger cuff <NUM> - the shell <NUM>, the LED-PD pair <NUM> and <NUM>, and the clamping mechanism <NUM>, are all re-usable and only the bladder <NUM> is disposable.

Claim 1:
A finger cuff (<NUM>) connectable to a patient's finger (<NUM>) to aid in measuring the patient's blood pressure by a blood pressure measurement system (<NUM>), the finger cuff (<NUM>) comprising:
a shell (<NUM>) having a finger cavity (<NUM>) and a pair of opposed first and second top portions (<NUM>), the finger cavity (<NUM>) of the shell (<NUM>) being configured to be placed under a patient's finger (<NUM>) to receive the patient's finger (<NUM>), the shell (<NUM>) including a light emitting diode (LED) - photodiode (PD) pair (<NUM>, <NUM>) protruding into the finger cavity (<NUM>);
a bladder (<NUM>) including a pair of openings (<NUM>, <NUM>) in the form of a pair of indentations that open towards the finger cavity (<NUM>), the bladder (<NUM>) mountable within the finger cavity (<NUM>) such that the pair of openings (<NUM>, <NUM>) receive and circumferentially surround and cover the LED-PD pair (<NUM>, <NUM>), respectively; and
a clamping mechanism (<NUM>) coupled to the opposed first and second top portions (<NUM>) of the shell (<NUM>), the clamping mechanism (<NUM>) being configured to suitably clamp the patient's finger (<NUM>) received in the finger cavity (<NUM>) of the shell (<NUM>) against the bladder (<NUM>) mounted within the finger cavity (<NUM>) of the shell (<NUM>) such that the bladder (<NUM>) and the LED-PD pair (<NUM>, <NUM>) aid in measuring the patient's blood pressure by the blood pressure measurement system (<NUM>).