Patent Application
20070004996
The present disclosure relates generally to detecting needle disengagement, and more particularly to mechanisms for sensing needle disengagement.
Hemodialysis treatments use AV fistula needles so that blood may be removed from an arterial side of a patient for dialysis and the cleansed blood returned to the patient via the venous side. In some instances, the needle may become disconnected from the vascular access point of the patient.
One potential problem that may be associated with needle disengagement on the venous side of the vascular access point is that the patient may suffer substantial blood loss. Various hemodialysis machines include visual and/or audio alarms that are generated upon recognition of needle disconnection. The visual and/or audio alarms may be useful to alert another party, for example, a caregiver, of the disengagement, however, if that party is unable to respond, the potential for the patient to lose blood remains.
Various methods are available for detecting disconnection of the needle. One method of detecting needle disengagement involves measuring venous pressure. However, a potential problem with measuring venous pressure is that the device may fail to register a significant pressure change due, at least in part, to “back pressure” forming in the venous blood line. Another method of detecting needle disengagement involves using leaking body fluid to complete circuits and generate an alarm. A potential problem with this method is that the level of the leaking body fluid may be below a threshold level needed to generate the alarm. As such, the leak may go undetected. Still another method of detecting needle disengagement involves measuring the conductivity of the body fluid. A potential problem with this method is that a slight disconnection of the needle may not generate a significant change in the conductivity of the fluid contacting the sensor.
As such, it would be desirable to provide a mechanism that is capable of detecting needle disengagement with a desirable level of sensitivity and/or is capable of shutting down the hemodialysis machine automatically upon recognition of needle disengagement.
A needle disengagement sensing mechanism includes a fistula needle that is adapted to carry a fluid. An electronic sensing system is operatively connected to the needle. The electronic sensing system is capable of detecting partial or full disengagement of the fistula needle from a position where it is engaged with the fluid. Disengagement detection is a result of i) a comparative analysis of complex impedance measurements of the needle when in and at least partially out of the fluid engaged position and/or ii) a comparative analysis of optical spectroscopic measurements taken through an area of the mechanism adapted to carry the fluid, the measurements being taken when the needle is in and at least partially out of the fluid engaged position. An alarm control conduit operatively connects the sensing system to a hemodialysis machine and/or an electronic device. The alarm control conduit generates an alarm upon detecting at least partial disengagement of the fistula needle.
Objects, features and advantages of embodiments of the present disclosure will become apparent by reference to the following detailed description and drawings, in which like reference numerals correspond to similar, though not necessarily identical components. Reference numerals having a previously described function may not necessarily be described in connection with other drawings in which they appear.
Embodiment(s) of the device/mechanism and method disclosed herein advantageously measure complex impedance of the needle and/or optical signals of an area of the mechanism/needle, thereby allowing partial or full disengagement to be detected with a desired level of sensitivity. Measuring the complex impedance of the needle and/or optical signals of an area of the mechanism/needle provides substantially increased sensitivity, at least in part, because the measurement is a multivariate measurement. The mechanism has the capability to measure more than one physical, electrical, and/or optical property substantially simultaneously, thereby improving the resolution of the measurement and allowing detection of partial or full needle disengagement with a substantially high degree of confidence. Further, embodiment(s) of the device/mechanism and method disclosed herein advantageously allow the automatic shutdown of a hemodialysis machine upon recognition of partial or full disengagement of a needle from an engaged patient position. The automatic shutdown enables a patient's treatment to be discontinued without the assistance of another person (e.g. a caregiver). Still further, embodiment(s) of the mechanism incorporate measuring complex impedance of the needle and/or optical signals of an area of the mechanism/needle adapted to carry fluid via an electronic sensing system that may be passive or active.
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The fistula needle 12 includes a body 18 having two opposed end regions 20, 22. One of the opposed end regions 20 is a fluid contacting end, and the other end region 22 is opposed to the fluid contacting end region 20. It is to be understood that the needle 12 is adapted to carry fluid (a non-limitative example of which is a bodily fluid (e.g. blood) of a patient P). In an embodiment when the needle 12 is in an engaged position, the fluid contacting end region 20 receives fluid that flows through the other end region 22 to a fluid tubing set 24, which is fluidly connected to the other end region 22 of the needle 12. It is to be understood that the fluid tubing set 24 may be connected to a medical device, such as, for example a hemodialysis machine.
Non-limitative examples of the fistula needle 12 include monopolar needles, concentric needles, single-fiber needles, and/or the like. A monopolar needle may serve as an active electrode, and a separate skin surface electrode may be used as a reference electrode. Concentric needles are generally bipolar and have an insulated wire(s) in the center of the cannula. It is to be understood that the active electrode is the tip of the center wire, and the reference electrode is the outside cannula. Single-fiber needles are generally bipolar needles having enhanced sensitivity. A non-limitative example of a single-fiber needle has about a 0.5 mm to about a 0.6 mm stainless steel cannula with a 25 μm platinum wire in its hollow shaft, where a portion of the platinum wire is exposed.
In the embodiment depicted in
The electronic sensing system 14, 14′ is capable of detecting partial or full disengagement of the fistula needle 12 from a position engaged with the fluid. The fluid or patient engaged position occurs when the needle 12 is fully inserted at a vascular access point V on the patient P. The fluid or patient disengaged position occurs when the needle 12 become partially or fully disengaged form the vascular access point V.
In an embodiment, the electronic sensing system 14, 14′ measures the complex impedance of the needle 12, both when the needle 12 is in, and when it 12 is at least partially out of the engaged position. Examples of complex impedances that the electronic sensing system 14, 14′ is capable of measuring include, but are not limited to inductance measurements, capacitance measurements, resistance measurements, magnetic measurements, and combinations thereof. Without being bound to any theory, it is believed that the results of the complex impedance measurements of the needle 12 in the engaged position advantageously differ from the results of the measurements of the needle 12 when disengaged. As such, the detection of disengagement results from a comparative analysis of the complex impedance measurements of the needle 12. It is to be understood that the electronic sensing system 14, 14′ is capable of comparing the various measurements and distinguishing between the various measurements.
In a non-limitative example, resistance impedance may be measured via a conductive strip or contact on the needle body 18 and a reference contact connected to a ground potential. In another non-limitative example, resistance impedance may be measured via a metallic needle body 18 and a return contact in relatively close proximity to the body 18 of the needle 12.
The electronic sensing system 14, 14′ may include any suitable electronic circuitry, sensors, and/or combination thereof. Non-limitative examples of suitable sensors include conductive sensors, capacitive sensors, inductive sensors, resistance sensors, magnetic sensors, optical sensors and/or combinations thereof. It is to be understood that the configuration of the sensors may be passive or active to improve the signal-to-noise ratio characteristics of the physiological measurement. With a passive configuration, the signal is measured without the addition of other signals, and in an active configuration, additional signals are provided to the sensor during measurements to improve sensor sensitivity.
The optical signal S emitted by the optical transmitter 19 may be infrared radiation, ultraviolet radiation, visible radiation, and/or combinations thereof. It is to be understood that the peak wavelength of the optical transmitter 19 and the sensitivity of the optical transducer 21 may be optimized to maximize the signal-to-noise ratio.
When the needle 12 is in the engaged position, fluid flows through the area across which the optical signal S is transmitted. In this embodiment, a relatively large optical attenuation may be measured. When the needle 12 is at least partially disengaged, the amount of fluid flowing through the area where the optical signal S is transmitted across decreases, resulting in a smaller optical attenuation. As such, the detection of disengagement results from a comparative analysis of the optical spectroscopic measurements (i.e. optical transmission characteristics) taken through the area when the needle 12 is in and at least partially out of the engaged position.
It is to be understood that the electronic sensing system 14, 14′ is capable of comparing the various measurements and distinguishing between the various measurements.
Yet further, it is to be understood that the electronic sensing system 14, 14′ may be capable of conducting both complex impedance measurements and comparisons and optical spectroscopic measurements and comparisons. Incorporating both methods may advantageously provide varying forms of generating the alarm (described hereinbelow).
The electronic sensing system 14, 14′ is operatively connected to the alarm control conduit 16.
In the wired embodiment of the alarm control conduit 16, a cable 28 electrically connects the electronic sensing system 14, 14′ to an electronic device 30 (non-limitative examples of which include pagers, computers, personal digital assistants (PDAs), cellular phones, and combinations thereof) and/or a hemodialysis machine 32. As depicted, the cable 28 electrically connects to a power outlet strip 34, where the hemodialysis machine 32 and/or the electronic device 30 may be plugged in.
In the wireless embodiment of the alarm control conduit 16, radio frequency or infrared means 36 electrically and operatively connects the electronic sensing system 14, 14′ to the electronic device 30 and/or the hemodialysis machine 32. In a non-limitative example, a transmitter (not shown) is operatively connected to the electronic sensing system 14, 14′, and a receiver (not shown) is operatively connected to the electronic device 30 and/or the hemodialysis machine 32. In this non-limitative example embodiment, the receiver may be positioned in, and electrically connected to, the power outlet strip 34.
Upon recognition of partial or full disengagement of the needle 12 from the engaged position, the electronic sensing system 14, 14′ sends a signal to the alarm control conduit 16. In response, the alarm control conduit 16 is capable of generating an alarm. Non-limitative examples of the alarm include visual alarms, audio alarms, and/or combinations thereof.
In alternate embodiments, the alarm is capable of sending a signal to the electronic device 30 and/or automatically shutting down the hemodialysis machine 32.
In an embodiment where the alarm control conduit 16 is operatively connected (e.g. via a cable 28 or a wireless 36 connection) with the power strip 34, the alarm interrupts a main power supply to any device (e.g. hemodialysis machine 32) that is plugged into the modified power strip 34. As such, the device loses power and shuts down. It is to be understood that in this embodiment, the power strip 34 may be modified to include electronics capable of interrupting the power supply, thereby shutting down the machine 32, upon recognition of the alarm.
In an alternate embodiment not depicted in the figures, the alarm control conduit 16 is operatively connected to the electronic device 30, which is also operatively connected to the hemodialysis machine 32. In this embodiment, upon recognizing the alarm, the electronic device 30 signals the hemodialysis machine 32 to shut down. Still further, the electronic device 30 may also or alternately be programmed so that the patient P or other person may manually shut down the machine 32 via the electronic device 30 when the alarm is generated. It is to be understood that in this embodiment, the hemodialysis machine 32 may be modified to include electronics capable of shutting down the machine 32 upon recognition of the signal from the electronic device 30.
It is to be understood that the previous methods of automatic shutdown may be combined such that a safeguard mode is implemented if one of the shutdown mechanisms fails. The alarm conduit control 16 may also optionally be programmed to emit a visual and/or audible alarm.
Referring now to
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Embodiment(s) of the mechanism 10 and method include, but are not limited to the following advantages. Detection at a desired level of sensitivity of partial or full disengagement of the needle 12 may be accomplished using the mechanism 10. Without being bound to any theory, this may be due, at least in part, to the direct impedance measurements of the needle 12 and/or the optical measurements. Further, the automatic shutdown of the hemodialysis machine 32 enables the treatment of patient P to be discontinued without the assistance of another person (e.g. a caregiver). Still further, embodiment(s) of the mechanism 10 incorporate measuring complex impedance of the needle and/or optical signals of an area of the mechanism 10 adapted to carry fluid via an electronic sensing system 14 that may be passive or active.
While several embodiments have been described in detail, it will be apparent to those skilled in the art that the disclosed embodiments may be modified. Therefore, the foregoing description is to be considered exemplary rather than limiting.
