WO2000056213A1

WO2000056213A1 - Locating and insertion device

Info

Publication number: WO2000056213A1
Application number: PCT/GB2000/001134
Authority: WO
Inventors: Aleksandar Zivanovic; Brian Lawrence Davies
Original assignee: Imperial College Of Science, Technology And Medicine
Priority date: 1999-03-24
Filing date: 2000-03-24
Publication date: 2000-09-28
Also published as: AU3444900A; GB9906759D0

Abstract

The present invention relates to a locating device for locating an artefact, in particular a vein, in soft tissue of a subject, and an insertion device for inserting a sharp instrument (12) into an artefact, in particular a vein, in soft tissue of a subject. The locating device comprises: at least one probe movable over the surface of soft tissue of a subject; a movement unit (27) for moving the at least one probe; a loading unit for selectively applying a predeterminable load to the at least one probe; a detector for detecting the displacement of the at least one probe when loaded; and a determination unit for determining the location of an artefact from the detected displacement of the at least one probe. The insertion device comprises: a drive unit (85) for inserting a sharp instrument into soft tissue of a subject; a detector (99) for detecting the force experienced by the drive unit on inserting the sharp instrument; and a control unit (3) for controlling the drive unit such as at least to stop further insertion of the sharp instrument on detection of a decrease in the force detected by the detector.

Description

LOCATING AND INSERTION DEVICES

The present invention relates to a locating device for locating an artefact in the soft tissue of a subject, in particular the vein of a human, and an insertion device for inserting a sharp instrument into an artefact in the soft tissue of a subject.

Taking blood samples by inserting a needle into a vein in the forearm, usually in the ante-cubital fossa, is a common procedure. Locating a vein can, however, prove very difficult and often requires multiple needle insertions prior actually to locating a vein. Such multiple needle insertions can lead to trauma, particularly in paediatric subjects. Another associated problem is that, even when a vein is properly detected, the needle can penetrate the far wall of the vein and cause painful and unsightly bruising.

It is thus an aim of the present invention to provide a locating device for locating an artefact, in particular a vein, in the soft tissue of a subject.

It is a further aim of the present invention to provide an insertion device for inserting a sharp instrument, such as a surgical needle, into an artefact, in particular a vein, in the soft tissue of a subject.

The present invention provides a locating device for locating an artefact, in particular a vein, in soft tissue of a subject, comprising: at least one probe movable over the surface of soft tissue of a subject; a movement unit for moving the at least one probe; a loading unit for selectively applying a predeterminable load to the at least one probe; a detector for detecting the displacement of the at least one probe when loaded; and a determination unit for determining the location of an artefact from the detected displacement of the at least one probe.

In one embodiment the movement unit is configured to locate the at least one probe at a plurality of discrete points on the surface of the soft tissue, and the loading unit is configured to load the at least one probe at each of the discrete points. In another embodiment the movement unit is configured to move the at least one probe continuously over the surface of the soft tissue.

In one embodiment the movement unit is configured to move the at least one probe along a line over the surface of the soft tissue.

In another embodiment the movement unit is configured to move the at least one probe over an area of the surface of the soft tissue.

Preferably, the determination unit is configured to determine the location of an artefact based on the point of the minimum detected displacement of the at least one probe.

In one embodiment the locating device comprises a single probe.

In another embodiment the locating device comprises a plurality of probes.

The present invention also provides an insertion device for inserting a sharp instrument into an artefact, in particular a vein, in soft tissue of a subject, comprising: a drive unit for inserting a sharp instrument into soft tissue of a subject; a detector for detecting the force experienced by the drive unit on inserting the sharp instrument; and a control unit for controlling the drive unit such as at least to stop further insertion of the sharp instrument on detection of a decrease in the force detected by the detector.

Preferably, the sharp instrument is a needle.

Preferably, the control unit is configured to control the drive unit such as at least to partially withdraw the sharp instrument on detection of a decrease in the force detected by the detector.

The present invention also extends to a fluid sampling robot comprising the above- described locating device. The present invention further extends to a fluid sampling robot comprising the above- described insertion device.

The present invention still further extends to a fluid sampling robot comprising the above-described locating device and the above-described insertion device.

The present invention further provides a method of locating an artefact, in particular a vein, in soft tissue of a subject, comprising the steps of: moving at least one probe over the surface of soft tissue of a subject; selectively applying a predeterminable load to the at least one probe; detecting the displacement of the at least one probe when loaded; and determining the location of an artefact from the detected displacement of the at least one probe.

In one embodiment the step of moving the at least one probe comprises the step of locating the at least one probe at a plurality of discrete points on the surface of the soft tissue, and the step of loading the at least one probe comprises the step of loading the at least one probe at each of the discrete points.

In another embodiment the step of moving the at least one probe comprises the step of moving the at least one probe continuously over the surface of the soft tissue.

In one embodiment the at least one probe is moved along a line over the surface of the soft tissue.

In another embodiment the at least one probe is moved over an area of the surface of the soft tissue.

Preferably, the step of determining the location of an artefact comprises the step of locating the artefact based on the point of the minimum detected displacement of the probe. In one embodiment the method uses a single probe.

In another embodiment the method uses a plurality of probes.

The present invention still further provides a method of inserting a sharp instrument into an artefact, in particular a vein, in soft tissue of a subject, comprising the steps of: inserting a sharp instrument into soft tissue of a subject using a drive unit; detecting the force experienced by the drive unit on inserting the sharp instrument; and controlling the drive unit such as at least to stop further insertion of the sharp instrument on detection of a decrease in the force detected by the detector.

Preferably, the sharp instrument is a needle.

Preferably, the step of controlling the drive unit comprises the step of at least partially withdrawing the sharp instrument on detection of a decrease in the force detected by the detector.

The present invention also extends to a method of sampling fluid from an artefact in soft tissue of a subject comprising the above-described locating method.

The present invention further extends to a method of sampling fluid from an artefact in soft tissue of a subject comprising the above-described insertion method.

The present invention still further extends to a method of sampling fluid from an artefact in soft tissue of a subject comprising the above-described locating method and the above-described insertion method.

A preferred embodiment of the present invention will now be described hereinbelow by way of example only with reference to the accompanying drawings, in which:

Figure 1 diagrammatically illustrates a blood sampling robot in accordance with a preferred embodiment of the present invention; Figure 2 illustrates a front view of the blood sampling device of the blood sampling robot of Figure 1 ;

Figure 3 illustrates a side view of the blood sampling device of Figure 2;

Figure 4 illustrates a plan view of the blood sampling device of Figure 2;

Figure 5 illustrates a representative probe displacement profile as measured by the blood sampling robot of Figure 1 ;

Figure 6 illustrates a representative force-position profile of a needle insertion as measured by the blood sampling robot of Figure 1 ; and

Figure 7 illustrates doppler-detected flow signals representative of background, an artery and a vein.

The blood sampling robot comprises a blood sampling device 1 and a control unit 3 for controlling the operation of the blood sampling device 1 in detecting a vein and inserting a surgical needle thereinto for the sampling of blood.

The blood sampling device 1 comprises a base unit 5, a first carriage 7 movably, in this embodiment slideably, disposed to the base unit 5, a support unit 9 rotatably disposed to the first carriage 7, a second carriage 10 movably, in this embodiment slideably, disposed to the support unit 9, and an instrument holding unit 11 movably, in this embodiment slideably, disposed to the second carriage 10 for holding an instrument 12.

The base unit 5 comprises a base plate 13 on which a subject locates the region of tissue in which a vein is to be located. Usually, a vein is located in the ante-cubital fossa for the sampling of blood, in which case the forearm would be located on the base plate 13. The base unit 5 further comprises a guide assembly 15 along which the first carriage 7 is slideable. The guide assembly 15 comprises first and second spaced upstanding end wall members 19, 21 and first and second parallel guide rods 23, 23 connected between the end wall members 19, 21 to which the first carriage 7 is slideably engaged.

The base unit 5 further comprises a drive assembly 27 which comprises a threaded drive rod 29, which extends between the end wall members 19, 21 and is captively held thereto such as to allow only for rotation thereof and a motor 31, in this embodiment a stepper motor, coupled to the drive rod 29 by a drive belt 33 for rotating the drive rod 29 in response to a drive signal from the control unit 3.

The first carriage 7 comprises first and second spaced upstanding side wall members 35, 37 and an interconnecting block 39 connecting the lower ends of the side wall members 35, 37. The side wall members 35, 37 each include an arcuate track 41 as a sector of an annulus. The interconnecting block 39 includes first and second guide bores 43, 43 in which the first and second guide rods 23, 23 are located and a threaded drive bore 45 in which the drive rod 29 is in threaded engagement.

The support unit 9 comprises a first, upwardly-extending arm 49 which is rotatably coupled to the first carriage 7 about a pivot 51 , which extends orthogonally to the axis of movement of the first carriage 7, and a second arm 52 which is fixed to and extends orthogonally from the distal end of the first arm 49 in a direction parallel to the pivot axis. In this embodiment the support unit 9 is lockable in position relative to the first carriage 7 by a locking bolt 53. The second arm 52 includes a substantially planar surface 54 over which the second carriage 10 is slideable.

The support unit 9 further comprises a guide assembly 55 to which the second carriage 10 is slideably disposed. The guide assembly 55 comprises first and second spaced end wall members 57, 59 and first and second parallel guide rods 61, 61 connected between the end wall members 57, 59 to which the second carriage 10 is slideably engaged.

The support unit 9 further comprises a drive assembly 63 which comprises a threaded drive rod 65, which extends between the end wall members 57, 59 and is captively held thereto such as to allow only for rotation thereof, and a motor 67, in this embodiment a stepper motor, coupled to the drive rod 65 by a drive belt 69 for rotating the drive rod 65 in response to a drive signal from the control unit 3.

The second carriage 10 comprises a main plate 71 which is located at the planar surface 54 of the second arm 52 of the support unit 9, and a supporting block 73 which is attached to one side of the plate 71 for supporting the plate 71 to the second arm 52. The supporting block 73 includes first and second guide bores 75, 75 in which the first and second guide rods 61, 61 are located and a threaded drive bore 77 in which the drive rod 65 is in threaded engagement.

The second carriage 10 further comprises a guide assembly 78 to which the instrument holding unit 1 1 is slideably disposed. The guide assembly 78 comprises first and second spaced end wall members 79, 81 which extend from the other side of the plate 71, and first and second parallel guide rods 83, 83 connected between the end wall members 79, 81 to which the instrument holding unit 11 is slideably engaged.

The second carriage 10 further comprises a drive assembly 85 which comprises a threaded drive rod 87, which extends between the end wall members 79, 81 and is captively held thereto such as to allow only for rotation thereof, and a motor 89, in this embodiment a stepper motor, coupled to the drive rod 87 for rotating the drive rod 87 in response to a drive signal from the control unit 3.

The instrument holding unit 11 comprises an instrument holder 91, in this embodiment a clamp, and a supporting block 93 attached to the instrument holder 91 for supporting the instrument holder 91 to the second carriage 10. The supporting block 93 includes first and second guide bores 95, 95 in which the first and second guide rods 83, 83 are located and a threaded drive bore 97 in which the drive rod 87 is in threaded engagement.

The instrument holding unit 1 1 further comprises a force sensor 99, in this embodiment a piezoelectric force sensor, for measuring the force applied to the instrument 12 when driven by the drive assembly 85. In an alternative embodiment the force sensor 99 could comprise a strain gauge.

The operation of the blood sampling robot is as follows.

The support unit 9 is moved to the upright position and locked in position by tightening the locking bolt 53. As illustrated in Figure 2, a blunt probe 12 is then clamped in the instrument holder 91. The instrument holding unit 1 1 is then moved, by selective operation of the drive assemblies 27, 63, 85 operated under control of the control unit 3, to a reference position. A subject then locates the region of the tissue from which a blood sample is to be taken, typically the ante-cubital fossa, beneath the probe 12. In a preferred embodiment the base unit 5 can include a brace for holding the region of tissue in fixed position.

By selective operation of the drive assemblies 27, 63, 85 operated under the control of the control unit 3, the probe 12 is then brought into contact with the surface of the tissue and the probe displacement profile measured on maintaining a predetermined load on the probe 12. A typical force threshold is 2 N. In this embodiment the drive assemblies 63, 85 are operated to measure a one-dimensional profile on a line laterally across the region of the tissue. In an alternative embodiment the drive assemblies 27, 63, 85 could be operated to measure a two-dimensional profile over the surface of the tissue. Measuring a two-dimensional profile has the advantage that a more optimal vein insertion location can be identified.

In one mode of operation, as in this embodiment, discrete measurements are taken at a plurality of spaced points along a line laterally across the region of the tissue. In this embodiment the spacing between the measurement points is about 3 mm, but spacings down to 1 mm could be employed. A representative probe displacement profile is illustrated in Figure 5. As will be noted, this probe displacement profile includes a region of lesser probe displacement which is characteristic of a vein; veins being suffer than surrounding fatty tissue and thus deformed less than the surrounding fatty tissue under the same load.

In another mode of operation, instead of generating the probe displacement profile by- taking discrete measurements at a plurality of spaced points, the probe 12 could be moved continuously over the surface of the tissue. This mode of operation would usually require lubrication of the surface of the tissue, typically by a lubricating gel, in order to avoid the possibility of the skin rucking up in front of the probe 12.

When the probe displacement profile has been measured, the control unit 3, by selective operation of the drive assemblies 27, 63, 85, returns the instrument holding unit 1 1 to the reference position and determines the position of a vein from the probe displacement profile. In this embodiment the control unit 3 is configured to determine the lateral centre of an identified vein as that position corresponding to the point of least probe displacement.

The probe 12 is then removed from the instrument holder 91 and replaced by a surgical syringe 12, as illustrated in Figure 3. With the syringe 12 clamped in position, the support unit 9 is then rotated about the pivot 51 such that the needle of the syringe 12 encloses an acute angle, in this embodiment an angle of about 30 degrees, with respect to a plane parallel to the base plate 13. The support unit 9 is then locked in this position by tightening the locking bolt 53. As will become clear hereinbelow, by rotating the support unit 9, the axis of movement of the needle of the syringe 12 encloses an acute angle with the surface of the tissue into which the needle is to be inserted, which tissue surface will be generally parallel to the base plate 13.

By selective operation of the drive assemblies 27, 63, 85 operated under the control of the control unit 3, the instrument holding unit 1 1 is moved from the reference position such as to position the needle of the syringe 12 at the determined vein position. Here, it will be noted that the control unit 3 is configured to insert the needle into the tissue at a point spaced from the detected vein position in order to accommodate for the vein being located below the surface of the tissue. The vein depth depends on the thickness of the fatty tissue, but typically is about 3 mm. Once in this position, the drive assembly 85, under the control of the control unit 3, is driven to insert the needle into the soft tissue. Insertion continues until penetration of the vein wall is detected by the control unit 3. at which time the drive assembly 85 is de-actuated. In an alternative embodiment the control unit 3 can be configured to back drive the drive assembly 85 when penetration of the vein wall is detected so as to withdraw the needle slightly. A representative force-displacement profile is illustrated in Figure 6. As will be noted, this force-displacement profile includes a pronounced dip characteristic of penetration of the artefact, in this embodiment the vein wall, which force dip is detected by the control unit 3 to halt the insertion of the needle.

When the required volume of blood has been sampled, the needle is withdrawn from the tissue and the instrument holding unit 1 1 returned to the reference position. The syringe 12 is then removed from the instrument holder 91. The blood sampling robot is then ready for further operation.

Finally, it will be understood that the present invention has been described in its preferred embodiment and can be modified in many different ways without departing from the scope of the invention as defined by the appended claims.

For example, in one modification the probe 12 can include a doppler sensor which allows for detection of flow signals. By providing a doppler sensor at the tip of the probe 12, the detected signals can be used to confirm that the detected artefact is in fact a vein and not, for example, an artery. Figure 7 illustrates signals representative of background, an artery and a vein.

Claims

1. A locating device for locating an artefact, in particular a vein, in soft tissue of a subject, comprising: at least one probe movable over the surface of soft tissue of a subject; a movement unit for moving the at least one probe; a loading unit for selectively applying a predeterminable load to the at least one probe; a detector for detecting the displacement of the at least one probe when loaded; and a determination unit for determining the location of an artefact from the detected displacement of the at least one probe.

2. The locating device of claim 1, wherein the movement unit is configured to locate the at least one probe at a plurality of discrete points on the surface of the soft tissue, and the loading unit is configured to load the at least one probe at each of the discrete points.

3. The locating device of claim 1, wherein the movement unit is configured to move the at least one probe continuously over the surface of the soft tissue.

4. The locating device of any of claims 1 to 3, wherein the movement unit is configured to move the at least one probe along a line over the surface of the soft tissue.

The locating device of any of claims 1 to 3, wherein the movement unit is configured to move the at least one probe over an area of the surface of the soft tissue.

6. The locating device of any of claims 1 to 5, wherein the determination unit is configured to determine the location of an artefact based on the point of the minimum detected displacement of the at least one probe.

7. The locating device of any of claims 1 to 6, comprising a single probe.

8. The locating device of any of claims 1 to 6, comprising a plurality of probes.

9. An insertion device for inserting a sharp instrument into an artefact, in particular a vein, in soft tissue of a subject, comprising: a drive unit for inserting a sharp instrument into soft tissue of a subject; a detector for detecting the force experienced by the drive unit on inserting the sharp instrument; and a control unit for controlling the drive unit such as at least to stop further insertion of the sharp instrument on detection of a decrease in the force detected by the detector.

10. The insertion device of claim 9, wherein the sharp instrument is a needle.

11. The insertion device of claim 9 or 10, wherein the control unit is configured to control the drive unit such as at least to partially withdraw the sharp instrument on detection of a decrease in the force detected by the detector.

12. A fluid sampling robot comprising the locating device of any of claims 1 to 8.

13. A fluid sampling robot comprising the insertion device of any of claims 9 to 11.

14. A fluid sampling robot comprising the locating device of any of claims 1 to 8 and the insertion device of any of claims 9 to 1 1.

15. Λ method of locating an artefact, in particular a vein, in soft tissue of a subject, comprising the steps of: moving at least one probe over the surface of soft tissue of a subject; selectively applying a predeterminable load to the at least one probe; detecting the displacement of the at least one probe when loaded; and determining the location of an artefact from the detected displacement of the at least one probe.

16. The method of claim 15, wherein the step of moving the at least one probe comprises the step of locating the probe at a plurality of discrete points on the surface of the soft tissue, and the step of loading the at least one probe comprises the step of loading the at least one probe at each of the discrete points.

17. The method of claim 15, wherein the step of moving the at least one probe comprises the step of moving the at least one probe continuously over the surface of the soft tissue.

18. The method of any of claims 15 to 17, wherein the at least one probe is moved along a line over the surface of the soft tissue.

19. The method of any of claims 15 to 17, wherein the at least one probe is moved over an area of the surface of the soft tissue.

20. The method of any of claims 15 to 19, wherein the step of determining the location of an artefact comprises the step of locating the artefact based on the point of the minimum detected displacement of the at least one probe.

21. The method of any of claims 15 to 20, using a single probe.

22. The method of any of claims 15 to 20, using a plurality of probes.

23. A method of inserting a sharp instrument into an artefact, in particular a vein, in soft tissue of a subject, comprising the steps of: inserting a sharp instrument into soft tissue of a subject using a drive unit; detecting the force experienced by the drive unit on inserting the sharp instrument; and controlling the drive unit such as at least to stop further insertion of the sharp instrument on detection of a decrease in the force detected by the detector.

24. The method of claim 23, wherein the sharp instrument is a needle.

25. The method of claim 23 or 24, wherein the step of controlling the drive unit comprises the step of at least partially withdrawing the sharp instrument on detection of a decrease in the force detected by the detector.

26. A method of sampling fluid from an artefact in soft tissue of a subject comprising the locating method of any of claims 15 to 22.

27. A method of sampling fluid from an artefact in soft tissue of a subject comprising the insertion method of any of claims 23 to 25.

28. A method of sampling fluid from an artefact in soft tissue of a subject comprising the locating method of any of claims 15 to 22 and the insertion method of any of claims 23 to 25.