HK1119038B - Device for the extraction of a body fluid - Google Patents

Description

Device for removing body fluid

Technical Field

The invention relates to a method for removing body fluid, in particular blood, wherein a lancing member penetrates a body part through the skin in a forward movement and receives the body fluid via a capillary structure of the lancing member. The invention also relates to another corresponding device.

Background

The method and the device for taking out the small liquid volume are mainly used for self-detection of blood sugar of a diabetic patient which is carried out for a plurality of times in daily life. The newer solution has a measuring microneedle as a disposable article in a hand-held instrument for producing a skin penetration, whereby a small amount of blood is taken out using capillary forces and this blood sample is analyzed. The combined system can also be used to carry out the required steps simply and quickly by laymen in a detection process that is as automated as possible. In order to achieve this, it is important to adapt the needling and collection process to the single-use set-up on the instrument, so that blood or, if appropriate, interstitial fluid can be collected efficiently, quickly and painlessly.

In this connection, it has already been proposed to include a skin contact for controlling the forward-directed puncturing movement in order to be able to achieve a defined puncturing depth. However, such a movement control must be adapted to the desired high penetration rate with high instrument outlay. But the main drawback is that it is thus impossible to detect the situation as regards the result of the actual removal of blood.

For optimal testing of the blood, the applicant WO 03/009759 a1 describes a combined method in which the needle unit with the capillary structure is first inserted and then pulled back over a length of the insertion and held there for a few seconds for a collection period. A part of the needle channel should thus be released, so that the body fluid collects in and from there enters the capillary structure.

A needling system is known from WO2004/080306, which is designed to detect a characteristic variable (e.g., impedance) during the needling movement and, if necessary, also during retraction. However, this is only recognized as a surface and may indicate the depth of entry or penetration depth or the residence time of the user. And does not involve effective monitoring of actual fluid contact beyond skin detection.

Disclosure of Invention

The object of the invention is to avoid the disadvantages of the prior art and to achieve an optimal detection of body fluids with simple application, in particular with regard to reliability, effectiveness, low pain and hygiene.

The following technical solutions claimed in the present invention are provided to achieve this object.

The invention proceeds from the idea that, instead of a puncturing monitoring, the liquid reception is effected in a post-state in which blood is received. In terms of method, it is therefore proposed that a body fluid contact of the piercing element be detected within the body part after the forward movement during the collection phase. Accordingly, a device has a detection mechanism for detecting a body fluid contact of the piercing element within the body part after the forward movement during the collecting state. In this way, optimal removal is possible, since the body fluid must be reliably removed again from the puncture wound when the body fluid contact is detected. This achieves a conforming process taking into account user-specific parameters such as local skin properties and blood flow. The allowability for detecting the minimum necessary blood volume is increased and a removal with a minimum of pain is achieved, since the duration can be adapted depending on the result of the bodily fluid contact.

Another aspect of the invention is that the collection process is not performed statically, but that an improved blood transport is ensured in the pain-free zone. Accordingly, a method is proposed for retracting the puncturing element after the forward movement in a retracted state with a first stroke and in a subsequent collection state with a second stroke, wherein the retracted state is shorter than the collection state and the first stroke is greater than the second stroke and the second stroke is greater than zero. A corresponding device provides that the needling drive is designed with a first stroke in the retracted state and a second stroke in the subsequent collection state for the retraction movement of the needling member, wherein the retracted state is shorter than the collection state and the first stroke is greater than the second stroke and the second stroke is greater than zero. This makes it possible to achieve a needle channel in the blood area quickly and painlessly, while the collection process is carried out in the capillary structure in the less sensitive outer skin area by the time duration required for the self-transport of the liquid. It has surprisingly been found that the collection effectiveness is significantly better than in the static actual position by means of a slow pull-back. One possible explanation is that after a rapid lancing movement the skin is pressed by the lancing mechanism and this pressing force initially prevents the blood from flowing out. But with slow retraction the skin relaxes again during the collection phase, thereby allowing better blood re-flow. It is envisaged that a suction effect is achieved by pulling back the piercing member, thereby providing additional blood. In this case, it is advantageous hygienically to collect the liquid in the puncturing state and a small quantity of liquid is available for a metered removal.

The invention provides an advantageous development and improvement.

The painful area of the body part or skin is quickly removed by quickly returning to the pulled back position with less needle depth. The region which is not exposed to blood on the outside is monitored during the waiting time whether blood is flowing back through the lancet channel. A high collection efficiency can be obtained upon contact with body fluids, without exceeding the dead volume. Furthermore, the liquid can be received particularly hygienically in the skin without the exiting blood being visible. The impedance measurement is suitable for detecting a contact of a body fluid, in particular with the introduction of a lancing device as an electrode. The fluid obtained from the body part or from the needle wound can be monitored according to the detected contact level of the body fluid. The reliability of the effective reception of body fluid is significantly increased by this monitoring. Optimal collection times can thus also be expected. If necessary, a fault signal is emitted in the absence of contact and the removal process is interrupted.

It is particularly preferred to receive body fluid in the outer, less painful skin layer during the collection state after the rapid retraction of the lancing member. In this case, the lancing device is retracted at the same speed or at different speeds at least in the partially collected state, whereby the collection effectiveness is correspondingly improved. The collection time is sufficiently designed to ensure adequate reception of the body fluid under the action of the capillary structure.

In particular, all the disclosed embodiments can be combined with one another with regard to the body fluid detection and the needling characteristics.

Drawings

The invention is described in detail below with the aid of embodiments that are represented schematically in the drawing. In the drawings:

figure 1 shows in block diagram a device for removing and optionally analyzing blood from a body part,

figures 2 to 5 show the needling member of the device according to figure 1 in different views in different needling positions,

figures 6 to 9 show different needling characteristics when using the needling member,

figure 10 shows an anatomical view of human skin in a schematic view,

fig. 11 shows the signal curves for different body fluid contact situations.

Detailed Description

The device shown in the figures allows the user to remove a blood sample for analysis, in particular for monitoring blood glucose, by himself. The device comprises a lancing member 10 as a disposable product for removing blood and a portable apparatus 12 for automatically disposing of the used lancing member 10.

The lancing device 10 shown in fig. 1 serves as a so-called "microsampler" for obtaining small amounts of blood from a body part 14, in particular the belly. The component is made as a flat component from thin stainless steel and has a distally shaped needle tip 16 as a lancing mechanism which is connected via a semi-open channel-shaped capillary channel 18 to a collection site 20 which may constitute a reaction zone for the confirmatory analysis of, for example, glucose. Verification of blood glucose exclusively by contactless optical methods is already known in the prior art and is therefore not described in detail here. However, it is also possible to select the collected blood to be fed to an analysis unit for analysis there.

The instrument and apparatus 12 has a lancing drive 22 for controlled forward and rearward movement of the lancing member 10 and a detection mechanism 24 for detecting blood contact with the lancing member 10 in a collection state. The needling drive 22 includes a mechanically and/or electrically operated drive unit 26, which is coupled to the needling member 10. It is specialized to have a two-stage hybrid drive in which a fast motion is imparted by a mechanism such as a drive spring or drive linkage, while a more slowly regulated motion is achieved by a motor. Alternatively, the electromagnetic drive influences the needling stroke in the form of a loudspeaker coil. The lancing drive 22 also comprises a control unit 28 for the process control or regulation of the blood removal and in particular the lancing movement. For this purpose, a microcontroller is used, which can optionally be additionally parameterized specifically for the user.

The detection means 24 can detect blood contact in the collecting state by impedance measurement via the lancing means 16 and the pressure ring 30, which is axially penetrated by the lancing means and is in contact with the body part 14, as counter electrodes. The lancing mechanism made of electrically conductive material can be controlled without risk by means of an electrical alternating voltage signal, for example 4Vpp and 10kHz, wherein the impedance in the path between the lancing mechanism and the counter electrode is significantly reduced by means of liquid contact. A monitoring device 32 enables an effective monitoring of the blood reception based on the detected body fluid contact, as explained in detail below.

Fig. 2 to 5 show a process of obtaining blood through the pricking member 10. The lancing mechanism 16 is first inserted through the skin surface 34 at a given depth into the body part 14 in a distally aligned forward movement, thereby reaching a blood presenting area 36 in the skin. At this site the capillaries terminate, possibly opening them by a needle mechanism. However, at this deeper point 36, the pain is also increased due to the neurons present there. It is therefore advantageous to have the lancing part be pulled back in a pulling-back movement directly after the forward movement from the deepest puncture position 38 into a pull-back position 40 (fig. 3) with a lower puncture depth. This pulled-back position is preferably located at the epidermis 42, especially inside the stratum corneum 44. After the rapid retraction of the lancing device 10, a certain time is left until the blood 46 flows into the epidermis again through the produced lancing channel 48.

The layer structure dimensions of human skin are actually shown in fig. 10. The epidermis having the stratum corneum as the uppermost cortex includes a depth of about 0.5 to 1mm, and the skin including the capillaries 37 reaches a deep portion of several millimeters.

According to fig. 4, after a waiting time after the forward movement of the retracted collection position 40, the blood contact is detected by the detection means 24 in the sense of effective monitoring. In this way, the collection time can be optimized, since the blood can reliably flow out of the needle wound again when the body fluid comes into contact. If, however, no blood contact is detected after the waiting time, the measurement can be interrupted by the monitoring device 32. Thereby producing no false results due to a lack or too little blood volume. For this purpose, the monitoring device 32 informs the user of a corresponding signal.

The collection process need not be performed statically, but rather can be performed during the continued pulling back movement of the piercing member 10. Collection may optionally be effected on the skin surface 34, as shown in fig. 5. The liquid contact can be reliably detected here by the lancing device 16, which is immersed in the discharged blood drop 50 and is thus in fluid contact with the skin, as a measuring electrode and the pressure dome 30, which is pressed against the skin, as a counter electrode. The pressure ring additionally serves to support the blood flow under pressure and to open the wound, thereby minimizing the contact between the lancing mechanism and the skin and the pain of the user associated therewith.

The needling characteristics shown in fig. 6 to 9 are particularly advantageous for blood reception which is as effective and less painful as possible. The term "needling characteristic" is understood here to mean the temporal course of the needling movement, as the depth of the needling is expressed as a function of time.

With the lancing feature shown in fig. 6, the lancing mechanism rapidly penetrates a blood-bearing, pain-sensitive skin area 52 in a forward movement to a given depth 56 and is immediately retracted to a depth of about 0.5mm in a retraction movement 58. The pull-back state is in this case of the order of magnitude of the duration of the forward movement, i.e. less than 100 μ s. The pulled-back position 60 can lie in the stratum corneum area and thus outside the pain area 52. The collection state 62 is then engaged, in which blood is received and the lancing member is slowly pulled back onto the skin surface. This collection state 62 lasts a few seconds, with the stroke d2 traveled by the lancing mechanism being much less than the pull-back stroke d1 during the pull-back state 58. The skin is relaxed by pulling back more slowly afterwards, so that the needle channel is not immediately locked again.

Since the collecting process takes a certain time, the process is suitably performed in an denervated outer skin area. The collection under the skin surface, i.e. in the puncturing state, is also important in order to avoid the blood from being discharged onto the skin and thus to achieve a particularly hygienic removal process. For this reason, blood that has appeared on the skin surface can be removed cleanly by only the piercing member 10, as long as the capillary force of the capillary tube 18 is sufficiently large at this position. This is the case when the lancing mechanism 16 is in at least a slightly pierced state, since the capillary depth becomes smaller towards the needle tip and thus also reduces the capillary force.

An electrical or electromagnetic drive is better suited for the needling profile according to fig. 6 than a purely mechanical drive, since the final impact effect is more difficult to control (damping can be achieved more simply by an electrical solution than by a mechanical solution).

In order to be able to set the puncture depth in a defined manner, the skin surface can be detected, for example, by an impedance measurement prior to the actual puncture process. Where the position of the skin surface is detected during the slow forward movement of the lancing member 10.

The transition between different needling characteristics may be controlled either by location (depth) or temporally. The transition between ranges with different speeds may be effected by intermittent changes, but may also be smooth (continuous speed change). The advantage of the continuous variation is that less drive energy is required and the adjustment of the movement is simplified.

The difference in needling characteristics shown in fig. 7 is only an additional stage 64 during the collection phase 62. After the rapid retraction to the depth B, a slightly slower retraction to the depth C is continued, the skin being relaxed during this interval. The actual collection process is then again effected slowly from the depth C up to the skin surface. The entire needling and collection process can thereby be shortened.

A similar process is given in accordance with FIG. 8, by slowly pulling back the lancing mechanism after the quick pull-back condition 58 until time t1 to achieve skin relaxation, and then continuing to collect at rest of the lancing mechanism until time t 2. However, a lateral offset of the lancing mechanism with respect to the skin is clearly perceived by the user.

In the needling profile according to fig. 9, after the first rapid forward movement 54, the needling mechanism is completely retracted from the skin and then reinserted in the second forward movement 54' with a lesser needling depth. Blood contact is detected at this point and the collection process is then performed with the lancing mechanism slowly pulled back to the skin surface 62. The advantage of a complete retraction is that a possible re-collision of the lancing mechanism takes place outside the skin and therefore no damping is required, which significantly reduces the requirements for the actuating mechanism.

This needling feature provides simple adjustment changes. The skin surface can first be detected from time t0 for an accurate determination of the penetration depth. This process can be accomplished inductively or by impedance measurement by slowly moving the lancing member relative to the skin until it contacts its surface as described above. The first needling process (fast entry and fast exit) can be performed as if "blindly", i.e. without feedback through the regulation loop. This has the advantage that, in particular in the case of solenoid drives, rapid and cost-intensive control circuits can be avoided. In hybrid drives this rapid needling process is undertaken by mechanical parts (e.g., spring or linkage drives). After the first needling process, the needling process is moved forward more slowly than before (state 54'). This movement can likewise be realized without a control loop. If the skin surface is reached (obtained by renewed skin examination if necessary), a control signal can be released which triggers the retention phase of the needling characteristic (collection state). The transition point 66 may be determined by a time delay relative to the trigger signal. This time delay must be short enough for it to no longer advance into the pain zone 52. This collection process up to t2 can likewise be carried out without position regulation by simple control. The lancing member is then pulled back into the device up to time t3 and the lancing mechanism is thus moved away from the skin.

Fig. 11 shows the time profile of the measurement signal 68 for different possibilities of blood contact in the situation according to fig. 2 to 4 in detail. The conductivity increases slowly until the inflection point 70 first, as the skin penetrates into dry skin, until the needle tip 16 contacts the blood in the skin 36 causing the signal to increase rapidly. At the end of the forward movement, a signal level 72 is reached, which is characteristic of direct body fluid contact and can thus be used as a comparison signal. It is considered here that the conductivity and impedance of the skin surface when contacting the skin is proportional between the needle tip 16 and the ring electrode 30 and thus the ring radius. The effective electrode surface is suddenly enlarged when the needle tip 16 is immersed into the body fluid 36, and the signal is influenced only by the skin thickness between the blood zone 36 and the ring 30 lying above it, which is much thinner than the ring radius. It is therefore advantageous, particularly for capacitive measurements, to electrically insulate the ring 30 from the skin surface 44.

At the end of the forward movement, according to fig. 11a, the blood-carrying region 36 is thus reached in fig. 2, and a signal level 72 is reached which is characteristic of the contact (and can be determined experimentally if necessary) of the body fluid. When subsequently retracted into the collection position 40 according to fig. 3, a state of short residence time can be entered until the body fluid again flows to the retracted needle tip. The signal therefore decreases during the retraction and reaches the maximum 72 again during the second contact with the blood. Effective monitoring of the blood reception can therefore be continued after a given waiting time has elapsed, a comparison being made whether a high signal level is again present.

For the case of rapid re-flow of body fluid, the body fluid contact does not disengage the rearwardly moving needle tip 16 and the signal level remains constantly high as shown in fig. 11 b. Active and effective monitoring can also be achieved here.

In contrast, the signal level in fig. 11c also drops again to the retracted position when no blood is flowing out or only poorly flowing out, so that a fault state is detected after a given waiting time has elapsed, in which no body fluid can be collected effectively, as a function of the change in the measurement signal. The critical signal change can be determined by comparing the signal level at the beginning of the waiting time or by evaluating the slope of the signal curve. The measurement can be interrupted and the user alerted.

Claims (9)

1. Device for removing body fluid, having a lancing part (10) for puncturing the skin in a body part (14) having a capillary structure (18) for receiving the body fluid and a lancing drive (22) for moving the lancing part (10) forward and backward, characterized in that the lancing drive (22) is designed to pull back the lancing part (10) in a first stroke (d1) in a retraction state (58) and in a subsequent collection state (62) in a second stroke (d2), wherein the retraction state (58) is shorter than the collection state (62) and the first stroke (d1) is greater than the second stroke (d2) and the second stroke is greater than zero.

2. The device according to claim 1, characterized in that the pull-back condition (58) is of the order of magnitude of the duration of the forward movement (54).

3. The device according to claim 1 or 2, wherein the collecting state (62) is prolonged by a factor of 10 to 10000 compared to the pull-back state (58).

4. The device according to claim 1 or 2, characterized in that the needling drive (22) causes the needle punching member (10) to be retracted at the same speed during the collecting state (62).

5. The device according to claim 1 or 2, characterized in that the needling drive (22) causes the needle punching part (10) to be retracted faster in a first time period in the collecting state (62) than in a subsequent second time period.

6. The device according to claim 1 or 2, characterized in that the needling drive (22) maintains the needling member (10) for a defined dwell time for a second period of time.

7. The device according to claim 1 or 2, characterized in that the lancing drive (22) causes the lancing part (10) to be completely withdrawn from the skin in the retracted state (58) and to be re-penetrated with a lesser lancing depth before the collecting state (62).

8. The device according to claim 1 or 2, characterized in that the needling drive (22) causes the needle punching member (10) to be retracted during the collecting state (62) with a second stroke of 2mm to 0.1 mm.

9. The device according to claim 1 or 2, characterized in that the movement of the piercing member (10) is controlled by time detection or position detection.