The present invention is not a federally sponsored research or development.
The present invention relates generally to the field of hypodermic injection of an agent for medical purpose. More specifically, the present invention provides an apparatus and methods to reduce pain and discomfort associated with an entry of a needle and an injectable agent into tissue.
Injection of an agent into cutaneous and muscle tissues through a needle prick disrupts mechanical and chemical stability of the tissue and initiates a series of electrophysiological and biochemical cascade in the local tissue environment and in free nerve endings of nociceptive primary afferent nerve fibers embedded in the tissue. Cationic channels of the free nerve endings are activated, dependent on biophysical properties of both the needle prick and injected agent. Once voltage gated Na+ channels are activated, membrane depolarization of the nociceptor is propagated, resulting in release of intracellular Ca++. The increase in Ca++ concentration mediates cellular and microenvironmental changes to sensitize nociceptors of the free nerve endings. Furthermore, cells that are disrupted by needle prick could release membrane fatty acids which convert to prostaglandins. Increase in prostaglandins could intensify nociceptive response of the free nerve endings, which translates into intensified painful sensation by a subject.
The majority of the nociceptive signals generated by the free nerve endings are transmitted via both A-delta and C nerve fibers to superficial dorsal horn of the spinal cord. A-delta nerve fibers are responsible for initial sensation of sharp localized pain and C fibers are responsible for so-called second pain of burning and bruised feeling over a wider area than perceived by the A-delta fibers. A-delta fibers are known to be sensitized by intense heat, and high intensity and prolonged activation of C fibers are known to perpetuate the sensitization cycle of C fibers by producing ligands acting on release of pro-inflammatory molecules. At the spinal cord, both A-delta and C-fibers produce glutamate that is a key molecule for transmission of sensation of pain. Postsynaptic nociceptive input then travels upward from the spinal cord to various parts of brain.
There are inhibitory neuronal signals arising from various parts of the brain that descend in the spinal cord to modulate nociception. Descending inhibitory signals may be activated by external factors including stimulation on peripheral or central nervous system. In addition, there are ascending inhibitory signals, albeit minor, arising from parts of the brain. Descending inhibitory signals come to various neuronal structures of the dorsal horn of the spinal cord where downward postsynaptic changes inhibit nociceptive responses. It is believed that in human subjects the descending inhibitory signals can be physically activated by acupuncture, transcutaneous electric nerve simulation (TENS), vibration, dorsal column stimulation and deep brain stimulation.
Vibration is one of peripheral stimulation methods to reduce nociception, which include TENS, acupuncture, acupuncture-like TENS, electroacupuncture and acupressure. Exact mechanisms of analgesia induced by vibration have not been clarified yet but it is believed to be related to activation of A-beta primary afferent nerve fibers that inhibit segmental neurons of the dorsal horn of the spinal cord. It is also proposed that vibration stimulates both high-threshold A-beta fibers and A-delta fibers, which activates the descending inhibitory signals to suppress the dorsal horn neurons. Clinically, both TENS and vibration have been shown to reduce acute and chronic pain conditions, including low back pain, acute orofacial pain, causalgia, pain associated with vaginal delivery of baby and arthritic pain. In particular, vibration of cutaneous tissue of patients has been shown to reduce pain associated with needle prick and injection of agents into the tissue, thereby reducing requirement of anesthetic agents for minor procedures on skin and its appendages.
Various frequencies have been studied for vibration induced analgesia, ranging from 20 Hz to 300 Hz with a varying degree of effectiveness on analgesia. Additional issues of vibration such as duration, amplitude and effective area and depth under vibration have not been studied for its comparative effectiveness except that it appears that analgesia is achieved best in an area directly under vibration. Shortcomings of vibration are short duration of effects and potential development of tolerance over repetitive uses.
Needle-free injection systems using high-pressure jet-stream have been developed over a few years to reduce discomfort of needle prick necessary for injecting agents into tissue. However, needle-free injection disrupts mechanical and chemical stability of the tissue, which initiates similar electrophysiological and biochemical responses in nociceptive primary afferent nerve fibers to needle-based injection systems. Diffuse but limited dispersion from a site of entry of pressured jet-stream of the needle-free system inside the tissue along a longitudinal injection path may be the only advantage of the needle-free system to the needle-based system that produces a radially globular expansion of an injected agent from a tip of a needle inserted in the tissue. It is conceivable that globular expansion of the injected agent, compared to the longitudinally diffuse dispersion of the agent, may exert a more outward pressure per an area of the tissue, thereby disrupting a larger amount of mechanical connection of the tissue. However, one major drawback of the needle-free injection system is a risk of contamination of injection nozzle by recipient's tissue fluid that may emanate from an entry site of injection of the recipient. Unless each device is used only once for each recipient, it poses a significant hazard of transmission of potentially infectious agents such as hepatitis virus or human immunodeficiency virus (HIV) to other recipients receiving injection using the same device. Disposable needle-free injection systems would be available yet their cost-effectiveness cannot be compared favorably to simple disposable syringes and steel needles.
Intensity of nociception, i.e., pain sensation, associated with conventional hypodermic injection of an agent may be ameliorated by limiting extent of mechanical and chemical disruption of a target tissue and by activating descending inhibitory signals. Thinner and shorter hypodermic needles with a more acute angle of bevel may reduce the extent of mechanical disruption of the tissue. Stimulation of an injection site by vibration is one of available methods to activate the descending inhibitory signals. Successful implementation of vibration for achieving analgesia during the needle-based injection would require generation of a vibration field surrounding both a needle penetration site and a tissue infiltration site of an injected agent for an adequate length of time, adequate and redundant activation of primary afferent nerve fibers and fast diffusion of the injected agent from the tip of a needle to adjacent tissues. Yet the foremost importance should be given to a reproducible method of fail-safe delivery of an agent to a recipient without a risk of contamination by biologic fluids.
To achieve on-site placement of vibration surrounding a needle penetration site of a recipient and a tissue infiltration site of an injected agent and to eliminate a risk of cross-contamination of other recipients by a contaminated apparatus by biologic fluids emanating from a needle penetration site of a recipient, the current apparatus comprises a detachably disposable vibration tip located at the proximal end, a distal end configured as a conduit for electric power and a longitudinally tubular handle assembly housing a vibration assembly and a control and power assembly. A distal part of the vibration tip is configured to be releasably and slidably coupled with a longitudinally cylindrical vibration resonance enclosure of the handle assembly. A proximal part of said vibration tip contacts a recipient's skin and is configured to provide a circumferential field of vibration surrounding a needle penetration site. The vibration assembly of the handle assembly generates vibrations that are resonated by the vibration resonance enclosure located at a proximal end of said vibration assembly. The control and power assembly comprises a battery, an electronic circuit board, a switch and an instrument panel, which are electrically connected with each other and are disposed in and about the handle assembly. The distal end is configured for replacing or recharging a battery of the control and power assembly.
In one embodiment, the detachably disposable vibration tip, provided as one or a plurality of operating devices having one or a plurality of configurations, comprises a distal elongated round body and a proximal ring portion connected to said elongated round body at an angle. There is provided a central tubular space for a length in the elongated round body along the longitudinal axis, which opens distally to a junctional surface of said elongated round body. The ring portion of the vibration tip, provided in one or a plurality of configurations, comprises a circumferential rim and a neck that connects the ring portion to the elongated round body. The circumferential rim is configured in a range of cross-sectional thickness, radius and elasticity. The ring portion is configured to contact with and to encircle an area of a tissue that is penetrated by a needle and to deliver vibrations to said area of needle penetration.
In one embodiment, the handle assembly, provided as one or a plurality of operating devices having one or a plurality of configurations, comprises a vibration assembly and a control and power assembly, arranged in tandem along the longitudinal axis inside said handle assembly. One of the configurations of the handle assembly includes a compartmentalized tubular structure that is trapezoidally round along the circumferential axis. In one embodiment, the vibration assembly is housed in a proximal compartment and the control and power assembly in a distal compartment of said handle assembly. In between of the compartments, there is provided a space that is filled with one or a plurality of vibration absorbing materials. In another embodiment, the handle assembly is equipped with one or a plurality of means to shield an operator's hand from an electromagnetic field generated by the vibration assembly. One of the means includes coating of an inner surface of said handle assembly by heavy metals such as copper or aluminum.
In one embodiment, the vibration assembly, provided as one or a plurality of operating devices having one or a plurality of mechanical configurations, comprises a vibration generator and a vibration resonance enclosure which is connected to the vibration generator. The vibration resonance enclosure, provided in one or a plurality of mechanical configurations including a cylindrically tubular configuration, is located proximal to the vibration generator along the longitudinal axis and protrudes longitudinally through a junctional surface of the proximal end of the handle assembly. A proximal portion of the vibration resonance enclosure is configured to be releasably and closely insertable in the inner central tubular space of the elongated round body of said vibration tip. A distal end of the vibration resonance enclosure is configured to be attached to the vibration generator and transmits vibrations to said vibration resonance enclosure. The vibrations then are transmitted from the vibration resonance enclosure to the elongated round body of the vibration tip and to the ring portion of the vibration tip.
In one embodiment, vibration is generated by an electromagnetic voice coil actuator with a moving coil, provided in one or a plurality of configurations, releasably and axially inserted in one or a plurality of cylindrical permanent magnets of said voice coil actuator. In a second embodiment, vibration is generated by an electromagnetic solenoid coil, provided in one or a plurality of configurations, releasably and axially inserted in one or a plurality of cylindrical permanent magnets. In another embodiment, vibration is produced by a vibratory electromagnetic motor provided as one or a plurality of mechanical configurations including an eccentric mass rotary motor or by an electromagnetic disc vibrator. A proximal end of the moving coil of the voice coil actuator, the vibratory rotary motor, or the disc vibrator is attached to a vibration cone which in turn is attached to the distal end of the vibration resonance enclosure. The vibration cone is configured as diaphragm in a range of thickness and pliability.
In one embodiment, the vibration resonance enclosure provides resonance which amplifies vibration in a certain range of frequencies generated by the vibration generator. One of the configurations of the vibration resonance enclosure provides a natural frequency of said resonance matched to a frequency range from 20 Hz to 300 Hz. The vibration resonance enclosure may or may not have a cylindrically tubular space inside said enclosure. A vibration resonance enclosure without the cylindrically tubular space is configured as a solid cylinder to which the vibration is directly transmitted and resonated.
In one embodiment, a moving coil of a voice coil actuator produces electromagnetic vibration in one or a plurality of frequencies ranging from 20 Hz to 20 kHz and of one or a plurality of amplitudes. In another embodiment, the voice coil actuator simultaneously generates vibrations of multiple frequencies. Concurrent generation of vibrations in multiple frequencies is meant to cover a wide range of nociceptive primary afferent nerve fibers which may have individually distinctive activation thresholds to different frequencies for activating inhibitory signals. Vibration amplitude is provided as adjustable to penetration depth of needle into tissue and to volume of injectable agent. A deeper penetration of a needle into a tissue and a larger volume of an injectable agent require a wider and deeper vibration field to sufficiently encompass the area of the injection, compared to a shallow penetration and to a smaller injection volume. Force of vibration is proportional to amplitude of vibration, which suggests that a higher amplitude is required to generate a larger force of vibration to cover a larger three-dimensional volume of a tissue that needs to be vibrated. Electromagnetic disc vibrator is also provided in one or a plurality of frequencies and with one or a plurality of amplitudes. The disc vibrator also is configured to simultaneously generate vibrations of multiple frequencies. Vibratory eccentric mass rotary motor is provided in frequency that is variable.
In one embodiment, the control and power assembly, comprising a electronic control unit and a power source, is housed in the handle assembly and connected electrically to the vibration generator. The power source includes one or a plurality of replaceable or rechargeable batteries and is electrically connected to the electronic control unit. The electronic control unit is provided as one or a plurality of electronic configurations, which comprises an electronic circuit board, a switch and an instrument panel and which controls an electric current to the vibration generator and modulates both frequency and amplitude of vibration. Both the electronic circuit board and the power source are housed in a compartment of the handle assembly, which is located distal to the vibration assembly compartment of said handle assembly and is enclosed by one or a plurality of vibration absorbing materials.
In one embodiment, an operator, using one hand, places the ring portion of the vibration tip of the apparatus with a firm pressure to a sterilized skin of a recipient and switches on said apparatus to provide the recipient with vibrations. The operator, using the other hand, pushes in a needle of a syringe in the middle of an encircled area of a tissue by the rim of the ring portion of the vibration tip of said apparatus and delivers an injectable agent into the tissue. Upon completion of the injection, the needle of the syringe is removed first, followed by switching off said apparatus and discarding the vibration tip by pulling out said vibration tip from the proximal end of the handle assembly. A new vibration tip then is installed for a next recipient.
Overview shows a schematic example of the apparatus of the present invention.
As described below, the present invention provides a vibration analgesia apparatus and methods of use. It is to be understood that the descriptions are solely for the purposes of illustrating the present invention, and should not be understood in any way as restrictive or limited. Embodiments of the present invention are preferably depicted with reference to
The overview shows a schematic three-dimensional illustration of an example of the apparatus.
In
In an example of one configuration, illustrated in
It is to be understood that the aforementioned description of the apparatus and methods is simple illustrative embodiments of the principles of the present invention. Various modifications and variations of the description of the present invention are expected to occur to those skilled in the art without departing from the spirit and scope of the present invention. Therefore the present invention is to be defined not by the aforementioned description but instead by the spirit and scope of the following claims.
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