Surgery – Instruments – Cutting – puncturing or piercing
Reexamination Certificate
1999-10-13
2001-04-03
Truong, Kevin (Department: 3731)
Surgery
Instruments
Cutting, puncturing or piercing
C606S181000
Reexamination Certificate
active
06210421
ABSTRACT:
The present invention addresses a device for cutting skin to obtain small blood samples from human or animal tissue in an almost pain-free manner. It comprises a blade with a cutting edge having a length of less than 10 mm and an oscillator to make the blade oscillate essentially parallel to the cutting edge.
To take small amounts of blood from the finger or the earlobe for diagnostic purposes, one uses lancets which are pricked into the corresponding body part either manually or with the aid of a simple apparatus by the doctor or lab personnel. It is a matter of fact that the lancet has to be sharp and sterile. Otherwise, there are no particularly high demands to be met by the doctors' offices as blood samples are collected from individual patients in greater time intervals and the procedure is carried out by specially trained staff.
The requirements are significantly higher when blood lancet devices are used which are to be operated by the patient. They are necessary to allow patient groups that are at a particular risk to regularly determine certain analytical blood values by home monitoring.
This applies in particular to diabetics who regularly and frequently have to monitor their blood glucose level to keep it within certain levels by adjusting the amount of insulin to be injected which depends on food intake, physical activity, and other factors. This is of utmost importance for the health of these patients to avoid delayed serious damage such as blindness and amputation of body parts.
For this reason, one has developed easy to handle and relatively inexpensive analytical systems which usually comprise blood test strips and a corresponding evaluation instrument. Although the possibility of performing an easy and relatively inexpensive analysis is available to every patient today, the self-monitoring of blood glucose levels has still not reached the desired general acceptance among diabetics. The main reason being the pain that accompanies the pricking procedure when taking the blood sample.
Prior art knows lancet devices where a spring-propelled lancet pricks the tissue at a very high speed. Blood emerges from the so-created wound which can then be used for diagnostic purposes. Devices of this kind are known, for example from U.S. patents U.S. Pat. No. 4,203,446 and U.S. Pat. No. 4,895,147. There is a great variety of such devices with differently ground lancets and different spring mechanisms available on the market. Experiments have shown, however, that the pain caused by this kind of device cannot be lowered under a limit which the user clearly identifies as being unpleasant. What makes it even more difficult in the case of diabetics is that the test must be carried out frequently; the affected skin parts such as the finger tips and earlobes develop cornifications which in turn require deeper penetration levels thus causing more pain during pricking.
Numerous different blood lancet devices have been developed that are suitable to generate the wound necessary to collect the blood specimen in a simple and relatively pain-free manner. Examples are described in patents U.S. Pat. No. 4,442,836, U.S. Pat. No. 4,469,110, U.S. Pat. No. 4,535,769, and U.S. Pat. No. 4,924,897. Blood sampling device for driving a lancet and lancets are made to match one another and are also referred to as blood collection systems. Despite some progress, the pain caused by the cutting procedure when using blood lancet device designed for patient use is still too great.
The pain sensed during cutting could be reduced in blood lancet devices where the needle is guided in a controlled manner (U.S. Pat. No. 4,824,879 and U.S. Pat. No. 5,318,584). The devices of this kind are known as controlled guidance systems, as opposed to ballistic systems where the lancet, propelled by a spring, contacts the skin surface in a relatively uncontrolled manner.
It was, hence, an object of the present invention to propose a device which causes less pain during blood sampling as is the case with prior arts systems. It was another object of the invention to provide a blood lancet where the penetration depth can be reproduced in a more precise and improved manner than is the case with known devices.
The object was accomplished in accordance with the invention in that the skin is penetrated in a manner where there is no pressure wave directed perpendicular to the skin and where a relatively small amount of pain receptors is activated due to precise guidance and a relatively small penetration depth of the lancet/blade. This can be achieved in that the skin is penetrated/opened in a procedure that is carried out essentially parallel to the skin surface. This cutting procedure causes significantly less pain than pricking.
In accordance with the invention, the pain sensed when obtaining small amounts of blood is reduced in that a rapid oscillating movement is superimposed on the movement (usually a linear movement) of the blade that is necessary to enter the tissue. The excursion of the blade generated by this oscillating movement can principally be transverse to the tissue or essentially perpendicular to the tissue. With respect to these two embodiments, two different blade types have proven to be expedient so that the embodiments are described separately hereinafter.
When coupling a slow pricking movement with an oscillating movement, it is advantageous that despite an extremely high relative movement of the blade with respect to the skin, a pressure wave affecting deeper layers of the blade is almost completely avoided since the excursion of the blade is very small despite the high speed (preferably ranging around 10-200 &mgr;m) and there is virtually no pressure component being generated perpendicular to the tissue surface. The blade “falls” into the skin. The penetration principle is, hence, based on a cutting procedure which can be carried out by an “oscillating” blade without a significant pressure component running perpendicular to the direction of movement. Owing to the small stroke of the blade, the cut is limited to very small dimensions and, hence, easy to control.
Coupling a slow blade movement with an oscillating movement leads to cutting procedures which cause less pain than do the methods for obtaining small blood samples known from prior art.
Time-consuming tests have shown that the disadvantages of the blood lancets known in prior art are likely due to the painfullness of the skin penetration process which is essentially caused by the activation of pain receptors and their afferent signals. When the lancet arrives on the tissue a pressure wave is generated that propagates predominantly in the direction of movement. This pressure wave precedes the moving blade and thus activates additional pain receptors which would not be activated during penetration and cutting if the lancet would execute a mere cutting and ripping process. Avoiding a pressure wave when the lancet hits the skin can, hence, significantly reduce the pain sensation. Moreover, the undefined penetration depth and the uncontrolled movements of the lancet are likely to be additional reasons for unnecessary high pain sensation when using known systems.
The device of the invention can be further improved when the skin opening is kept as small as possible, preferably smaller than 1.5 mm, more preferably smaller than 1 mm, and when the cutting movement is carried out in a controlled manner.
It is also important that the site opening be generated in a controlled movement and not in an uncontrolled “rip”. Ripping the tissue would lead to a corresponding pressure wave and/or pulling of the tissue which then causes pain. Advantageous movements are those where the blade is guided such that forward and backward movements are uniform. It is also advantageous to control the movement such that the forward movement upon reaching a predefined dead point changes into a backward movement.
REFERENCES:
patent: 4203446 (1980-05-01), Sutor et al.
patent: 4750489 (1988-06-01), Berkman et al.
patent: 4924879 (1990-05-01), O'Brien
patent: 5047044 (1991-09-0
Bocker Dirk
Fruhstorfer Heinrich
Arent Fox Kintner & Plotkin & Kahn, PLLC
Roche Diagnostics GmbH
Truong Kevin
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