Lancet device with skin movement control and ballistic preload

Details Lancet device with skin movement control and ballistic preload Lancet device with skin movement control and ballistic preload

1999-03-08

2001-10-23

Reip, David O. (Department: 3731)

Surgery

Instruments

Cutting, puncturing or piercing

Reexamination Certificate

active

06306152

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to devices for penetrating the skin to extract blood or other fluids, and more particularly, to a device for driving a lancet to puncture the skin.
BACKGROUND
Medical tests that require a small volume of blood are well known. For example, test kits for self-measurement of blood sugar levels are utilized by diabetics. These test kits require that a drop of blood be placed on a test strip that is then inserted into a measurement apparatus that displays the glucose concentration in the blood sample. To obtain the drop of blood, the user is supplied with a lancet device, which makes a skin prick, typically in the user's finger. It would be advantageous to minimize the variation between lancing episodes so that sufficient blood is obtained every time and yet the skin is not overly traumatized, since any unnecessary trauma to the skin would result in unnecessary discomfort.
To successfully obtain blood, a piercing device must traverse the skin's various layers to reach the blood vasculature. Human skin is composed of a tough, keratinized squamous epithelium. The outermost layer of skin is known as the epidermis (0.07 to 0.12 mm thick), and has its own distinct layers: stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale. (For a review about skin, see Tortora and Anagnostakos “
Principles of anatomy and Physiology,”
Harper and Row 1981). Underneath the epidermis is the dermis, which is 1 to 2 mm thick. Because of its varying elasticity and thickness due to the cellular structure and anatomical locations, the force necessary for penetrating the epidermis to access the vascular beds within the dermis layer will vary. It has been reported that skin tension is the greatest in the areas where the epidermal elastic keratinous fibers are dense, particularly in regions where the skin is thick, such as is found in the epigastric (stomach) regions.
To penetrate the skin surface requires a force applied normal to the surface of the skin equal to or greater than the rupture strength of the skin. Below this force level, there is first an elastic range within which the degree of deflection corresponds directly with the applied force (skin depression), followed by a non-linear response by the skin (otherwise known as the inelastic response), corresponding to the further stretching of the skin at the point of application prior to rupture. The applied force reaches a maximum when the skin ruptures, resulting in the penetration of the object into the skin. The capillary bed under the dermis is approximately 300 to 750 microns below the outer surface of the skin in the areas of the fingers, the forearms and the abdomen. Bleeding can occur when the penetration of the object reaches the capillary bed.
Many factors affect the pain sensation associated with the sampling of blood. One factor is thought to be the generation of pressure waves that are built up at the site of puncture. Providing a shallow taper to the piercing end of the lancet should reduce the pressure wave buildup, and thereby reduce the pain sensation of blood sampling.
Another successful method to minimize the pain of skin puncture by a needle, pin or lancet, is to minimize the area over which the puncture occurs. This can be achieved by miniaturizing the needle or lancet and by reducing the force applied to create the wound. The smaller the needle, the less force is required to puncture the skin, and less nerves endings are stimulated by the cut. Unfortunately, as the size of the needle used becomes smaller, the tendency of the needle to flex increases. Flexing the needle during skin penetration will increase the discomfort of the user.
Additional ways to reduce the discomfort associated with blood sampling include reducing the penetration depth of the needle into the skin and rapidly advancing and retracting the needle from the skin. Optimizing the factors to reduce patient discomfort will encourage compliance to self test, for example, for diabetic self-monitoring. Certain lancets and lancet launchers have been used. For example, U.S. Pat. No. 4,976,724 (Nieto, et al.), U.S. Pat. No. 5,318,584 (Lange, et al.); U.S. Pat. No. 5,628,764 (Schraga); U.S. Pat. No. 5,611,809 (Marshall, et al.); U.S. Pat. No. 5,624,458 (Lipscher); U.S. Pat. No. 5,628,765 (Morita); U.S. Pat. No. 5,630,828 (Marwhirt, et al.); U.S. Pat. No. 5,643,306 (Schraga); U.S. Pat. No. 5,645,555 (Davis, et al.); U.S. Pat. No. 5,707,384 (Kim); U.S. Pat. No. 5,733,300 (Pambianchi); and U.S. Pat. No. 5,746,761 (Turchin) disclose reusable or disposable launchers for lancets.
However, for blood sampling, there is still a need for a technique that can provide an adequate amount of blood with little discomfort to a patient and provide less variation in penetration depth among different lancing episodes.
SUMMARY OF THE INVENTION
The present invention provides a technique for extracting blood from the skin of a user with reduced discomfort. In one aspect, a device for puncturing the skin of a patient is provided. The device includes a lancet for puncturing the skin and a skin stabilizer associated with the lancet for stabilizing the skin peripheral to the puncture site to reduce its freedom of movement when the lancet strikes it. The skin stabilizer has an opening through which the lancet can pass. When applied to the skin, the stabilizer presses on the skin around the opening. The application of the skin stabilizer, in addition to reducing the freedom of movement of the skin under it, increases the tautness of the skin in the opening prior to the lancet penetrating the skin. The opening is not substantially larger than the size of the lancet.
The present invention can be used to advantageously lance the skin of a user with more reproducible results. Since the skin under the skin stabilizer is prevented from excessive movement and the stretching of the skin at the lancing site (in the opening not held under the skin stabilizer) is accomplished prior to the lancet contact, the variation of lancet penetration into the skin is significantly reduced between lancing episodes. With a tighter control of this variation of penetration depth, it would be much easier to reproducibly lance the skin only to the desired depth for obtaining a specific amount of blood. With better control of the penetration depth, the skin is spared the unnecessary discomfort of excessive penetration by the lancet. This will lead to better compliance of the patient self-monitoring routine prescribed by health professionals.
In an embodiment, the skin stabilizer is propelled to strike the skin to apply pressure right before the lancet is forced into the skin ballistically. The skin stabilizer provides a well-controlled and painless preload for stabilizing the skin. Furthermore, the rapid penetration of the lancet that immediately follows the preload application would result in less pain sensation, since the impact of the skin stabilizer would tend to distract the user at the time of lancet penetration. The skin stabilizer can have a bore that is mated with (i.e., closely fits) the lancet. The lancet can slide freely under guidance. Such a system will prevent lateral flexure of the lancet, thereby allowing a thinner lancet to be used.


REFERENCES:
patent: 4817603 (1989-04-01), Turner et al.
patent: 4976724 (1990-12-01), Nieto et al.
patent: 4983178 (1991-01-01), Schnell
patent: 5318584 (1994-06-01), Lange et al.
patent: 5540709 (1996-07-01), Ramel
patent: 5554166 (1996-09-01), Lange et al.
patent: 5611809 (1997-03-01), Marshall et al.
patent: 5624458 (1997-04-01), Lipscher
patent: 5628764 (1997-05-01), Schraga
patent: 5628765 (1997-05-01), Morita
patent: 5630828 (1997-05-01), Mawhirt
patent: 5643306 (1997-07-01), Schraga
patent: 5645555 (1997-07-01), Davis et al.
patent: 5707384 (1998-01-01), Kim
patent: 5733300 (1998-03-01), Pambianchi et al.
patent: 5746761 (1998-05-01), Turchin
patent: 5951493 (1999-09-01), Douglas et al.

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