Patent Application
20070213682
The invention concerns a penetration device and method for the extraction of body fluid with a penetration element that can prick the skin of a body part and an actuator formed to drive penetration movement of the penetration element.
Self-monitoring tests requiring a small volume of blood are well known. For example, test kits for measurement of blood sugar levels are utilized by diabetics. These kits require that a drop of blood be placed on a test strip that cooperates with a hand-held (or portable) measurement apparatus, which in turn displays the glucose concentration in the blood sample. To obtain the drop of blood, the user is typically supplied with a lancet device, which makes a skin prick, typically in the user's finger.
The condition of the skin has had a significant effect on the penetration of the lancet into it. Because of the ability of the skin to stretch, a significant variation in a depth of penetration of the lancet between different lancing episodes was possible. In prior technology, lancets were launched at speeds of about 1-5 m/sec. Using that technology, it is understood that a variation in skin impression and tissue movement prior to penetration was in the range of about 0.5 mm up to about 1 mm.
The observed variation in the penetration depth among different lancing episodes for a non-stabilized skin surface is attributed to the fact that, below a given penetration force level, there is a first linerly elastic range of the skin movement followed by an inelastic response until finally the lancet pierces with further stretching of the skin at the lancing site. Such a difference in distance between the first touching of the skin and the entry of the skin by the lancet depending on imperfections of the skin can lead to considerable variations in the actual penetration depth.
A skin stabilizer was therefore proposed as a remedy, which is pressed on the skin prior to the lancet penetrating the skin. See, U.S. Pat. No. 6,306,152 B1, The sequence, however, of movement must be controlled and possibly the blood is displaced by the pressed skin stabilizer.
The present invention provides a puncturing device and method formed to reach a definite penetration depth for improvement of the extraction of body fluid such as blood.
The invention is based on the idea that avoidance of the extensive skin movement during penetration may be achieved by taking advantage of the inertia of the concerned tissue parts. Accordingly, the instant invention uses an actuator in the form of a high-speed drive to bring the penetration element to a very high penetration speed that a penetration depth variation caused by skin impression or compression is less than about 0.3 mm, more particularly less than about 0.2 mm. Thus, in the instant invention the penetration depth no longer significantly depends on the elasticity or imperfections of the skin, but can be specifically and individually defined. No special measures are imposed on the penetration element for this, which is especially favorable for disposable units. Due to reduced penetration depth inaccuracy, a person can adjust the penetration device better to be reproducible in order to achieve an optimum penetration depth in the sense of a successful fluid extraction and reduction of the penetration pain. The skin is less traumatized by not penetrating unnecessarily deep, such that, due to increased convenience, prescribed test routines are more likely maintained, which is important for blood sugar tests in diabetes care.
An embodiment of the invention includes a method for extracting body fluid from a body part, the method comprising providing a penetration device including a penetration element formed to pierce the body part and an actuator formed to propel forward movement of the penetration element, moving the penetration element toward the body part at a very high penetration speed to form an impression in the body part having a depth less than about 0.3 mm, and piercing the body part with the penetration element.
Another embodiment provides a penetration device for the extraction of a body fluid. The device comprises a penetration element formed to pierce a skin of a body part, and actuating means for propelling a penetration movement of the penetration element, wherein the actuating means has a high-speed drive formed to bring the penetration element to such a high penetration speed that a penetration depth variation caused by skin impression is less than about 0.3 mm.
Another embodiment provides a kit for the extraction of body fluid from a body part. The kit comprises a pressing ring, a penetration element sized for extension into the pressing ring and formed to pierce the body part, a first actuator formed to propel forward movement of the penetration element at a penetration speed of at least about 15 m/sec, and a second actuator formed to propel a retraction of the penetration element from the body part.
It is appreciated that in at least one embodiment of the present invention it is the actuator that provides the penetration element with a penetration speed of at least about 15 m/sec. In another embodiment of the invention, the actuator provides the penetration element with a penetration speed of about 20 m/sec to about 30 m/sec, in order to reduce significantly the penetration depth variation caused by skin impression.
Further, for the collection of the body fluid, an embodiment provides that a retraction speed for the retraction of the penetration element out of the skin amounts to a no more than about 10% of the penetration speed.
In order to simplify the acceleration and its braking, an embodiment provides that the mass of the penetrative part of the penetration element penetrating into the body part is less than about 25 mg.
An embodiment of the invention provides that the actuator comprise separate drives for the forward movement and the retracting movement of the penetration element. With that, the different speeds in the forward propulsion phase and retracting phrase can be controlled.
An embodiment of the invention provides that the actuator can create an electromagnetic impulse for the initiation of the forward movement of the penetration element. Another embodiment provides for that the actuator create an excess-pressure impulse triggering the forward movement of the penetration element, such as via a pneumatic or hydraulic cylinder or a pyrotechnic propelling charge.
In order to provide high energy storage density, an embodiment provides that the actuator comprises a preloaded spring element, such as a pre-compressed silicone rubber spring, for the forward movement of the penetration element.
Another embodiment provides that the actuator comprises a driving body, which can be accelerated and decelerated, separately from the penetration element, such as a flywheel or a plunger, for the transfer of a mechanical impulse to the penetration element.
In order to create a definite framework, an embodiment provides that the penetration element is supported in a carrier or housing and is linearly moveable along an acceleration distance. For limiting the forward movement, an embodiment provides that the housing has a stop for the penetration element.
A further embodiment proves that the actuator engages the carrier for the retracting movement of the penetration element, whereby the carrier forms a driver for the penetration element.
In an embodiment, the penetration element is formed by a lancet, a microsampler (a penetration unit with reception area for the sample) or an integrated system, with which not only the extraction of blood but also the analysis is carried out, without additional steps on the part of the user.
As regarding the method, an embodiment provides that the penetration speed of the penetration element is selected to be very high that a penetration depth variation caused by skin impression is significantly reduced, such that, the skin surface is compressed by less than about 0.3 mm. In an embodiment, the skin surface is compressed by less than about 0.2 mm prior to penetration of the penetration element. For this, the penetration speed of at least about 15 m/sec is selected.
A further embodiment provides that the penetration element is driven in the forward phase of the penetration movement in a non-controlled manner such that the penetration element is provided with a kinetic energy, which is at minimum an order of magnitude greater than the energy required for penetration into the skin, and the surplus kinetic energy of the penetration element at the end of the forward-directed penetration movement is transferred to the carrier as thrust.
Other features and embodiments of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
Below, the invention is explained in detail based on the embodiments represented schematically in the drawings. The following are shown respectively in the longitudinal cross section:
The penetration or lancing devices represented in the drawings comprise a penetration or lancing element 14 for pricking into the skin 10 of a body part 12 and an actuator 16 that is formed to propel forward movement of the penetration element 14 to a sufficiently high penetration speed in order to reduce penetration depth variation formed by skin deformation. Non-limiting examples of suitable uses of a penetration device 20 include blood extraction systems, stand-alone pricking apparatuses, micro-samplers and integrated penetration and analysis systems for blood sugar measurements for patient self-monitoring.
According to
A diameter of the opening of the ring 22 is in the order of about 3 to about 8 mm. It is appreciated, that the diameter of the opening may vary depending upon the size of the body part e.g. the finger of e.g. a child or adult. It is further appreciated that the structure of the ring may be formed of a solid plastic or metal or may be flexible and formed of, for example a flexible plastic or rubber material. While the ring 22 may be a portion of a portable instrument, an additional non-limiting example of a compression unit suitable for use with the penetration element is found in U.S. Pat. No. 6.679,852 the disclosure of which is hereby incorporated by reference.
It is appreciated that while a finger is illustrated and described, than any number of body parts, non-limiting examples of which include hands, arms, legs, feet, toes, head, neck, stomach, chest, back, and buttocks, are within the scope of the present invention. The penetration speed of the drive of the penetration element 14 is selected to be so high that a concave impression 44 (
The penetration element 14 shown in FIGS. 1(a-c) is positioned within a channel 39 of a housing or carrier 32. The penetration element 14 has an elongated shaft 24, at whose distal end a penetration tip 28 is grinded and a transversal collection slit 26 is provided. In an embodiment, the shaft 24 and the tip 28 of the penetration element 14 have a combined mass that is less than about 25 mg. The proximal end of the penetration element 14 is coupled to the drive through a coupling member 30. A non-limiting example of a suitable penetration element 14 is a lancet.
Penetration element 14 is illustrated and described as one example of a suitable lancet. As used herein, the term “lancet” refers to an elongated object with a sharp point for inserting into the skin to induce bleeding., it is understood that generally lancets may be needle-like with a round cross-section, or it may have cutting edge(s) along its elongated body for a cutting action to effect a less traumatic penetration into the skin in accordance with this disclosure. It is further appreciated in accordance with the present invention that the penetration element 14 may be a microsampler, or an integrated penetration and analyzing system. When the term “prick” and “pierce” is used herein, unless specified otherwise, it is to be understood that any of such penetration elements may be used.
The housing 32 has opposite distal and proximal ends 35, 37 and the channel 39 extends between the ends 35, 37. The penetration element 14 is capable of linearly traversing a pre-defined acceleration distance 34 in channel 39 of the housing 32. A stop 36 is provided in the housing 32 at the distal end of the acceleration distance 34 for the limitation of the forward movement, in the direction shown by arrow 41 in
In order to carry out the forward and retraction movements (41, 43) of the penetration element 14 with the desired speed profile, the actuator 16 contains a high speed drive 38 for the fast penetration phase and a second separate drive 40 for the slower retracting phase of the penetration movements. The drive 38 acts directly on the coupling member 30 of the penetration element 14, while the drive 40 for the retracting phase attaches to the housing 32.
The housing 32 can be closed at its distal end 35 with a penetrable foil 42 for sterile protection. The coupling member 30 can also provide a sealing function on the proximal end 37, so that the penetration tip 28 within the housing 32 remains sterile and protected from environmental influences. The housing 32 can also be a portion of a magazine (not shown), a non-limiting example of which includes a cylindrical magazine in order to provide a number of penetration elements 14 for successive penetrations. Before starting the penetration action, the penetration device 20 is preset to a desired penetration depth distance in the finger/ring-configuration, as is shown in
In operation, the penetration element 14 pierces the body part to an extent, which permits the extraction of body fluid. When body fluid is extracted, the penetration depth distance following the piercing of the body part can be controlled by limiting the length the penetration element 14 protrudes from the distal end 35 of the housing 32. In the finger, the blood capillaries will end in the region where interstitial fluid is present, whereas the circumstances in the abdominal wall are different. In general, the dermis has a thickness of about 0.5 mm, and then each individual should be able to precisely adjust the penetration depth to a value between about 0.5 mm and 3 mm to account for any boundary condition, for example even for different consistency of the skin in winter and summer.
As shown in
The drive 38 brings the penetration element 14 to such a high penetration speed that the penetration depth variation caused by skin impression 44 is less than about 0.3 mm. In an embodiment, the penetration depth variation is less than about 0.2 mm. At the same time, the transverse oscillatory movements of the longitudinally guided penetration shaft 24 are avoided by the fast movement so that the penetration pain felt in the body part 12 is reduced.
A non-limiting estimate gives that for a penetration force of 0.3 N and a concerned tissue area of the assumed cube-shaped expansion of 1.5 mm as well as a penetration speed of 20 m/sec, the skin 10 is compressed by less than 0.1 mm per 1 mm penetration depth. The penetration depth variation caused by that lies therefore in the range of only 10%, so that a person intra-individually can adjust better to achieve an optimum with respect to the required penetration depth.
In order to reduce the equipment expense, it is appropriate if the penetration element 14 is driven in a non-controlled manner in the forward penetration phase of the penetration movement by the drive 38. This means that at least a significant part of the kinetic energy is transferred to the penetration element 14 before its penetration into skin 10 so that the cutting movement is carried out almost ballistically until the stop 36 is reached by the coupling member 30. For that, the transferred kinetic energy should be minimally about an order of magnitude above the cutting energy required for penetration in order to retain the very high speed during the forward movement into the tissue. A non-limiting example is as follows: for over 50% of the penetration depth d, the penetration speed can still be around about 15 m/sec.
After the fast penetration, the penetration element 14 is retracted in direction 43, as shown in
In FIGS. 1 to 6, different penetration devices are shown, each of which has a different actuating means for propelling a penetration movement of the penetration element to such a high penetration speed that a penetration depth variation caused by skin impression is less than about 0.3 mm. Each actuating means has a high-speed drive formed for the forward movement 41 of the penetration element 14 supported in the housing 32. Similar or same parts are provided with the same reference numbers as described above.
In the embodiment according to
For the embodiment according to
As such, a penetration process and device for the extraction of body fluid is provided wherein a penetration element 14 is driven at a penetration speed for the penetration of the skin 10 of a body part 12 characterized in that the penetration speed of the penetration element 14 is selected to be so high that the penetration depth variation caused by skin impression is significantly reduced. In an embodiment, the penetration depth variation caused by skin impression is less than 0.3 mm. A penetration speed of more than 15 m/sec is used.
In a further embodiment, the penetration element 14 is driven in a non-controlled manner in the forward phase of the penetration movement. The penetration element 14 is propelled with a kinetic energy, which is at least an order of magnitude greater than the energy required for the penetration into the skin 10. Further, a surplus kinetic energy of the penetration element 14 at the end of the forward-directed penetration movement is transferred to the housing 32 as thrust. The body part 12 is pressed against an opening 22 of a portable instrument so that the skin 10 bulges inside the instrument in order to allow the penetration of the penetration element 14.
Having described the invention in detail and by reference to specific embodiments thereof, it will be apparent that modification and variations are possible without departing from the scope of the invention defined in the appended claims. More specifically, although some aspects of the present invention are identified herein, it is contemplated that the present invention is not necessarily limed to these aspects of the invention.
