Patent Application
20080065130
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. A number of embodiments of the invention are shown in detail; although it will be apparent to those skilled in the relevant art that some features that are not relevant to the present invention may not be shown for the sake of clarity. It should be noted that directional terms, such as “up”, “down”, “top” and “bottom”, are used herein solely for the convenience of the reader in order to aid in the reader's understanding of the illustrated embodiments, and it is not the intent that the use of these directional terms in any manner limit the described, illustrated, and/or claimed features to a specific direction or orientation.
The present invention generally concerns an expression device for expressing fluid from an incision. The expression device includes an elastomeric ring, such as an o-ring, that is mounted to an expression plate. In one form, the expression device can have a unitary structure, and in another form, the device can have a two-component, complementary structure, such as an o-ring mounted to a support body. For the single molded piece, the expression device can be fabricated from a single material, such as silicone or other types of flexible elastomeric plastics, or a hard plastic, like polystyrene or ABS. For the two-component form, the expression device can be fabricated from two or more materials. For instance, the o-ring can be fabricated from an elastomeric material, and the support can be fabricated from a hard plastic with an elastomeric overmold. In another embodiment, the o-ring can be made of hard plastic, and the support can be made from an elastomeric plastic. In one particular embodiment, the o-ring has an internal diameter of 7 mm and a cross-sectional width of 1.5 mm. The support in this embodiment defines a lancet opening that has an internal diameter of 6 mm. In a further embodiment, the support has a countersink or beveled surface around the lancet opening. The countersink can have an angle of 20° to 30°. For an expression device having a concave expression ring with a countersink angle of 20°, it was discovered that the expression device unexpectedly improved expression of blood by 148.1% as compared to a control expression device.
Turning to
Referring again to
As can be seen in
Table I has been provided below which shows the results of a control study.
In the study protocol, three healthy subjects with normal skin types were lanced with a conventional microsampler 68 of a type commonly known in the art. The microsampler 68 used in the control study included a generally flat lancet with a capillary groove for transporting fluid to a test strip or sensor attached to the lancet. The lancet of the microsampler 68 lanced an incision in the skin with a single forward and backward movement through the expression or lancet opening 46. The microsampler 68 was fired using a conventional spring-based lancing mechanism, but it should be recognized that other types of lancing or firing mechanisms can be used to fire the lancet. Each subject was lanced to a depth of 1.8 mm on both hands as well as on the forearm and the radial side of the ring, middle, and index fingers.
Prior to lancing the skin, the subject pushed the incision site against one of three types of expression rings: a control type, an o-ring type, and a concave type. Fifteen (15) tests (N) were performed for each type of expression ring. The control type expression member was generally rigid and ring-shaped, and the surface that contacts the skin in the control was generally flat. With the o-ring type expression ring, the ring had an elastic o-ring that was pressed against the skin, but the o-ring type expression ring did not have a beveled surface around the expression opening. On the other hand, the concave type expression ring was configured in the manner as described above. That is, the concave expression ring included the expression cap 32 of the type illustrated in
After lancing, the incision site was firmly held against each type of expression ring for 4 seconds. The finger was removed and blood on the surface of the skin was collected with a capillary tube. The volume of blood in the capillary tube was then measured. The results from the tests of the three expression ring types have been tabulated in Table I.
For the “Lancing Success Rate” column in Table I, lancing was considered successful when the sample volume of blood produced on the skin was at least 0.1 μL, regardless of the manner in which the sample volume was obtained. In other words, the “Lancing Success Rate” column in Table I reflects whether the incision was capable of ever producing a sufficient fluid sample. For example, if the microsampler did not cut enough capillaries beneath the skin to produce a sufficient sample size, then the lancing would have been considered a failure. Lancing success could have been achieved with or without the need for expressing fluid. So if the incision by itself bled a sufficient volume of blood, without any type of expression, the lancing would have been considered successful. Likewise, even if use of the expression ring was unable to produce a sufficient sample volume, but a sample volume ≧0.1 μL was afterwards created by expressing in some other manner, such as by pinching or squeezing the skin, then lancing was considered successful. The 0.1 μL cutoff value was selected because 0.1 μL sample volume sizes are typically the lower limit for accurate home diagnostic testing in the current state of the art. The “Mean Blood Volume Expressed” column in Table I indicates the mean blood volume collected over all of the test for a particular expression ring type. Regarding the “Expression Success Rate” column in Table I, expression with a selected expression ring type was considered successful when the sample volume of blood on the skin surface was ≧0.1 μL. It should be recognized that the differences between the “Lancing Success Rate” and “Expression Success Rate” columns occurred when the particular expression ring could not express a sufficient amount of blood, but a sufficient amount (i.e., ≧0.1 μL) was able to be expressed in some other manner, such as by squeezing the skin. As can be seen in Table I, the expression cap 32 with countersink angle 66 of 20° (concave ring type) was able to successfully express fluid every time, whereas the control and o-ring expression ring types were considerably less successful.
Unexpectedly, it was discovered that the expression cap 32 with countersink angle 66 of 20° was able to produce over twice as much blood as compared to the control and o-ring expression ring types. The “Percent (%) Improvement (Expressed Blood) Over Control” column shows the percentage difference in volume between the expression ring being tested and the control. Looking at Table I, with the expression cap 32 having a countersink angle 66 of 20°, the percent improvement over the control expression ring was significant, specifically 148.1%. Even when this concave ring type is compared with the o-ring type expression ring, the concave ring type with a 20° countersink angle 66 represented about a 107.9% improvement in mean blood volume expressed. Thus, it should be appreciated that the concave expression ring enhances the ability to consistently provide a sufficient fluid sample for testing purposes.
While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected. All publications, patents and patent applications cited in this specification are herein incorporated by reference as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference as set forth in its entirety herein.
