PROBE

Abstract

A system for measuring haemodynamic parameters relating to a subject, the system comprising a DRS probe, a microscope probe, and a cap for use at a respective distal end of each of the probes, one at a time. The cap comprises a rigid flat contact surface for contact with a body surface of a subject, the contact surface comprising an aperture arranged such that, in use, the aperture is optically aligned with the optical probe. A rigid side wall surrounds the contact surface, defining a closed end and an open end, the closed end being formed by the contact surface. The open end is arranged to receive the probe in use. The side wall is arranged such that, in use, the cap is held in abutment against the probe. A securing portion is arranged to removably secure the cap to the probe.

Claims

1. A system for measuring haemodynamic parameters relating to a subject, the system comprising: a DRS probe; a microscope probe; and a cap for use at a respective distal end of each of the probes, one at a time, wherein the cap comprises: a rigid flat contact surface for contact with a body surface of the subject, said contact surface comprising an aperture, said aperture being arranged such that, in use, the aperture is optically aligned with the optical probe in use; a rigid side wall surrounding the contact surface, wherein the side wall defines a closed end and an open end, said closed end being formed by the contact surface and said open end being arranged to receive the probe in use, said side wall being arranged such that, in use, the cap is held in abutment against the probe; and a securing portion arranged to removably secure the cap to each of the probes.

2. The system as claimed in claim 1, wherein the cap further comprises a substantially transparent window portion that covers the aperture of the contact surface.

3. The system as claimed in claim 2, wherein the cap is arranged such that, in use, a distance between the probe and the window portion is less than approximately 0.5 mm.

4. The system as claimed in claim 2, wherein the cap is arranged such that, in use, an operating end of the probe is in contact with the transparent window portion.

5. The system as claimed in claim 2, wherein the window portion has a thickness less than 1 mm, optionally between approximately 0.10 mm and 0.80 mm, further optionally between approximately 0.20 mm and 0.60 mm, further optionally between approximately 0.25 mm and 0.50 mm.

6. The system as claimed in claim 2, wherein the window portion comprises the same material as the contact surface and side wall, and optionally the securing portion.

7. The system as claimed in claim 2, wherein the window portion is affixed to the surface portion, optionally using glue or ultrasonic welding.

8. The system as claimed in claim 1, wherein an area of the contact surface is at least approximately 4 cm.sup.2, optionally wherein the area of the contact surface is at least approximately 5 cm.sup.2, further optionally wherein the area of the contact surface is at least approximately 6 cm.sup.2.

9. The system as claimed in claim 1, wherein the contact surface and side wall are optically opaque.

10. The system as claimed in claim 1, wherein the cap is substantially cylindrical.

11. The system as claimed in claim 1, wherein the side wall comprises has a diameter less than a diameter of the securement portion.

12. The system as claimed in claim 1, wherein the side wall comprises has a diameter less than a diameter of the contact surface.

13. The system as claimed in claim 1, wherein the contact surface and the side wall comprise a polymer.

14. The system as claimed in claim 13, wherein the contact surface and the side wall comprise the same polymer.

15. The system as claimed in claim 1, wherein the securing portion comprises a polymer, optionally wherein the securing portion comprises the same polymer as the contact surface and/or side wall.

16. The system as claimed in claim 13, wherein the polymer is biocompatible.

17. The system as claimed in claim 13, wherein the polymer does not discolour when sterilised and/or stored.

18. The system as claimed in claim 1, wherein the contact surface and the side wall are integrally formed, optionally wherein the securement portion and the side wall are integrally formed.

19. The system as claimed in claim 1, wherein the securing portion comprises a plurality of protrusions extending from the side wall, wherein each of said protrusions comprises an engagement member arranged to engage with a corresponding engagement member on the probe.

20. The system as claimed in claim 19, wherein the engagement members of the cap comprise at least one of a tab, a rib, or a tongue; and/or wherein the corresponding engagement on the probe comprises a groove or a socket.

21. The system as claimed in claim 1, wherein the securement portion is less rigid than the contact surface and side wall.

22. An optical probe arrangement for measuring haemodynamic parameters relating to a subject, the system comprising: an optical probe; and a cap for use at said distal end of the probe, wherein the cap comprises: a rigid flat contact surface for contact with a body surface of the subject, said contact surface comprising an aperture, said aperture being arranged such that, in use, the aperture is optically aligned with the optical probe; a rigid side wall surrounding the contact surface, wherein the side wall defines a closed end and an open end, said closed end being formed by the contact surface and said open end being arranged to receive the probe, said side wall being arranged such that, in use, the cap is held in abutment against the probe; and a securing portion arranged to removably secure the cap to the probe.

23. A cap for use at a distal end of an optical probe, wherein the cap comprises: a rigid flat contact surface for contact with a body surface of a subject, said contact surface comprising an aperture, said aperture being arranged such that, in use, the aperture is optically aligned with the optical probe; a rigid side wall surrounding the contact surface, wherein the side wall defines a closed end and an open end, said closed end being formed by the contact surface and said open end being arranged to receive the probe, said side wall being arranged such that, in use, the cap is held in abutment against the probe; and a securing portion arranged to removably secure the cap to the probe.

24-27. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0126] Certain embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

[0127] FIG. 1 is a side-on view of the body of a cap in accordance with an embodiment of the present invention;

[0128] FIG. 2 is a perspective view of the body of the cap of FIG. 1, providing a view of the interior of the cap;

[0129] FIG. 3 is a further view of the body of the cap of FIG. 1, providing a view of the side profile of the cap;

[0130] FIG. 4 is a schematic drawing of a window portion to be used with the cap body of FIGS. 1 to 3;

[0131] FIG. 5 is a cutaway view of a cap including both the cap body and window portion once assembled;

[0132] FIG. 6 shows a system for taking measurements of haemodynamic parameters relating to a patient;

[0133] FIG. 7 shows the system of FIG. 6 when the DRS probe is in use;

[0134] FIG. 8 shows the system of FIG. 6 when the microscope probe is in use;

[0135] FIG. 9 is a chart that shows the O.sub.2 estimate for varying degree of probe tilt;

[0136] FIG. 10 is a box plot that shows the mean intensity of reflected light associated with a number of different cap arrangements; and

[0137] FIG. 11 is a box plot that shows an exemplary set of O.sub.2 saturation measurements acquired with a DRS probe using different cap arrangements.

DETAILED DESCRIPTION

[0138] FIGS. 1 to 3 show the body of a cap 2 in accordance with an embodiment of the present invention in different views. Specifically, FIG. 1 is a side-on view of the body of the cap 2; FIG. 2 is a perspective view of the body of the cap 2, providing a view of the interior of the cap 2; and FIG. 3 is a further view of the body of the cap 2, providing a view of the side profile of the cap 2.

[0139] The cap 2 comprises a contact surface 4 and a side wall 6. As can be seen clearly in FIG. 1, the contact surface 4 is substantially flat and has a circular cross-section. The centre of the contact surface 4 is provided with a circular aperture 8. The contact surface 4 and side wall 6 are both constructed from an optically opaque polymer, and are formed using injection molding. The polymer used may, for example, be Eastar MN200, polycarbonate, or Makrolon 2458. These polymers may initially be transparent, where a colourant is added to provide the desired optical opacity prior to the injection molding process.

[0140] The side wall 6 is of a substantially cylindrical construction, such that the side wall extends around the contact surface 4. A substantially cylindrical securement portion 12 extends from the top of the side wall 6, where the securement portion 12 is discussed in further detail below. The side wall 6 has an annular portion 10 which is of smaller diameter than the securement portion 12 and the contact surface 4, though it will be appreciated that other arrangements are possible. The narrowed annular portion 10 provides a shoulder 13 on which the probe can rest.

[0141] At the securement portion 12 located at the top of the side wall 6, i.e. at the open end of the cap 2, there are a number of protrusions 14 that extend away from the contact surface 4. In this particular example, the protrusions 14 have a ‘bunny ear’ shape, though it will be appreciated that alternative shapes could be used as appropriate. The cap 2 of FIGS. 1 to 3 has four such protrusions 14.

[0142] Each of the protrusions 14 has an engagement member 16 which is arranged to engage with corresponding engagement member (e.g. a groove) on the probe when in use, as described in further detail below with reference to FIGS. 6 to 8. In this example, the engagement members 16 are small tabs that extend from the respective protrusion 14 toward the centre of the cap 2, i.e. in the direction of the aperture 8. For the sake of simplicity, all of the engagement members 16 are of identical dimensions and are positioned at the same height, i.e. distance from the contact surface 4, thus allowing easy connection and disconnection from a probe with a uniform groove around its handle. However, other arrangements are envisaged where this is not necessary, e.g. tabs at different heights arranged to engage with groove(s) at different positions on the probe handle.

[0143] FIG. 4 is a schematic drawing of a window portion 18 to be used with the cap body of FIGS. 1 to 3. The window portion 18 is constructed from a transparent polymer, such that it is substantially transparent with respect to at least visible and NIR light, e.g. to wavelengths between approximately 400 nm and 1400 nm. The window portion 18 may, of course, have different optical properties, depending on the requirements of the probes with which the cap 2 is to be used.

[0144] The window portion 18 has a central part 20 and a peripheral part 22. The central part 20 is the primary area through which light travels, e.g. during DRS or microscopy measurements. The peripheral part 22 surrounds the central part 20 and is shaped to fit in a suitable recess provided in the contact surface 4, as can be seen more clearly in FIG. 5.

[0145] FIG. 5 is a cutaway view of a cap 2 including both the cap body (i.e. the contact surface 4 and side wall 6) and window portion 18 once assembled. As can be seen in FIG. 5, the window portion 18 is positioned such that the aperture 8 is covered by the window portion 18. Thus the window portion 18 seals the aperture 8, thereby preventing the ingress of dirt, grease, particulate matter etc. into the interior of the cap 2. This prevents contaminates affecting the optics of a probe positioned within the cap 2, which may be particularly useful for microscopy procedures where baby oil is used, because the cap 2 prevents the oil getting to the microscope optics while allowing light to pass through the contact surface 4 via the window portion 18.

[0146] Similarly, sealing the aperture 8 with a window portion 18 may also advantageously prevent the body part under examination from contamination, e.g. due to pathogens, cleaning agent residues, chemicals, or dirt on the probe(s).

[0147] FIG. 6 shows a system 24 for taking measurements of haemodynamic parameters relating to a patient 26. The system 24 comprises a DRS probe 28 and a video microscope probe 30. The system 24 also includes the cap 2 described hereinabove with reference to FIGS. 1 to 5. In FIG. 6, the system 24 is shown without the cap 2 engaged with either probe 28, 30, however the cap 2 is shown in use in FIGS. 7 and 8, which are described in further detail below.

[0148] The DRS probe 28 includes optics 32, which are contained within a handle 34, which acts as a housing for the probe 28. The handle 34 has a groove 36 that extends around the periphery of the handle 34.

[0149] Similarly, the microscope probe 30 includes optics 38, which are contained within a handle 40, which acts as a housing for the probe 30. The handle 40 also has a groove 42 that extends around the periphery of the handle 40.

[0150] Both probes 28, 30 are to be used on the skin on the patient's hand 26 to determine haemodynamic parameters relating to the patient, where the DRS and microscopy measurement steps are described with reference to FIGS. 7 and 8 below respectively. It will be appreciated that while the hand of the patient 26 is used in this example, other parts of the body could be used instead as appropriate.

[0151] FIG. 7 shows the system 24 of FIG. 6 when the DRS probe 28 is in use. The cap 2 is ‘clicked’ into place on the DRS probe 28, where the engagement members 16 on the protrusions 14 physically engage with the groove 36 on the handle 34 of the DRS probe 28. Once put in place, the gap between the optics 32 of the DRS probe 28 and the transparent window portion 18 of the cap 2 is minimal, for example less than 0.5 mm, and the optics 32 of the DRS probe 28 may be pushed right up against the window portion 18 in some arrangements.

[0152] Firstly, a measurement is taken in which the DRS probe 28 is placed against a white reference 44, which substantially reflects all light. The measurements taken in relation to the white reference 44 are used for the sake of comparison. Generally, the operator may take a number of measurements using the white reference 44, for example three measurements may be taken using the white reference 44.

[0153] The operator then moves the DRS probe 28 to the patient's skin 26 and takes a number of DRS measurements relating to the patient. For example, the operator may take twelve DRS measurements in respect of the patient's skin 26.

[0154] The DRS recordings are captured from a skin area of roughly 1-2 cm.sup.2. The DRS probe 28 is relocated for each of the twelve recordings in order to provide statistical data for averaging and calculation of coefficient of variation. From these recordings, the level of local oxygenation in the skin capillaries is extracted by a suitable algorithm, known in the art per se, the details of which are not described herein.

[0155] The DRS probe 28 is kept substantially upright throughout the DRS measurements because the flat contact surface 4 of the cap 2 which is in contact with the patient's skin 26 impedes the tilting of the probe 28 away from the optimum angle of incidence, which in this example is normal (i.e. at right angles) to the patient's skin 26. This helps to improve the reliability of repeatability of the measurements taken with the DRS probe 28.

[0156] Once all of the DRS measurements have been taken, the video microscopy steps are carried out as described with reference to FIG. 8, which shows the system 24 of FIG. 6 when the microscope probe 30 is in use.

[0157] The cap 2 is removed from the DRS probe 28. While the mechanical connection between the cap 2 and the probes 28, 30 is robust during use, the ‘click-on’ nature of the cap 2 makes it relatively easy for the operator to remove it from one probe and to move it over to the other probe.

[0158] Once removed from the DRS probe 28, the cap 2 is ‘clicked’ into place on the microscope probe 30. Similarly to with the DRS probe 28, the engagement members 16 on the protrusions 14 physically engage with the groove 42 on the handle 40 of the microscope probe 30. The gap between the optics 38 of the microscope probe 30 and the transparent window portion 18 of the cap 2 is minimal, for example less than 0.5 mm, and the optics 38 of the microscope probe 30 may be pushed right up against the window portion 18 in some arrangements.

[0159] Baby oil 46 is applied to the patient's skin 26 in order to reduce the impact of specular reflections on measurements taken with the microscope probe 30. The video microscope 30 is then positioned on the patient's skin 26 and a number of video recordings are taken. Generally, the use of the baby oil 46 in the microscopy procedure means that the microscopy is typically carried out after the DRS procedure, which requires no such oil.

[0160] In this particular example, five videos are recorded using the microscope probe 30 which captures a video sequence of 20 seconds for each of the recordings. As with the DRS procedure described above with reference to FIG. 7, the microscope probe 30 is relocated for each recording and the total area covered is approximately the same as in the DRS procedure. From these video recordings, the capillary density (i.e. the capillaries per square millimeter which may be counted by human visual analysis) and velocities are extracted (which may be graded on a scale ranging from 0-5 by a human analysis and interpretation).

[0161] The cap 2 prevents the baby oil 46 from coming into contact with the optics 38 of the microscope probe 30. This may advantageously reduce the amount of cleaning of the probe 30 that is required, and may help to prevent the ingress of grease, dirt, etc. from affecting the operation of the microscope probe 30. As above, sealing the aperture 8 with a window portion 18 may also advantageously prevent the body part under examination from contamination, e.g. due to pathogens, cleaning agent residues, chemicals, or dirt on the microscope probe 30.

[0162] As with the DRS probe 28, the microscope probe 30 is kept substantially upright during the measurements due to the flat contact surface 4 of the cap 2. This helps to improve the reliability of repeatability of the measurements taken with the microscope probe 30.

[0163] FIG. 10 is a box plot that shows the mean intensity of reflected light associated with a number of different cap arrangements. Specifically, FIG. 10 shows the mean intensity over a recorded spectrum of 400 nm to 900 nm as a function of different cap setups.

[0164] There are nine recordings for each of the six setups, where each recording is depicted as a dot on the corresponding box plot. The central line across the box plot for each setup indicates the mean value associated with that cap setup. The area of the box immediately outwards of the central line shows the standard error of the mean (95% confidence interval) for that setup, assuming a Gaussian distribution of the measurements. The outer box for each setup indicates the standard deviation.

[0165] In particular, the arrangements used in this pilot study, shown in FIG. 10 in the following order are: [0166] 1. A bare probe without a cap. [0167] 2. A flexible black cap. [0168] 3. A rigid black cap with window of 0.25 mm thickness, where the probe is pushed probe onto the window portion. [0169] 4. A rigid black cap with window of 0.25 mm thickness, where there is a gap of 0.5 mm to 1.0 mm between the probe and the window portion. [0170] 5. A rigid black cap with window of 0.50 mm thickness, where the probe is pushed probe onto the window portion. [0171] 6. A rigid black cap with window of 0.50 mm thickness, where there is a gap of 0.5 mm to 1.0 mm between the probe and the window portion.

[0172] FIG. 10 shows the mean intensity from the spectroscopy recording on skin using the various cap setups as described above. It can be seen from the box plot that the average intensity only changes significantly in setups where there is a window with a distance of 0.5 mm to 1.0 mm between the probe tip and the window (i.e. measurements 4 and 6).

[0173] Thus measurements 4 and 6 demonstrate the ‘flash light’ effect referred to previously. However, where the probe tip is pushed close to the transparent window portion (i.e. measurements 3 and 5), it is clear that the window portion does not significantly impact to average intensity of the reflected light compared to cases where no window is used (i.e. measurements 1 and 2).

[0174] FIG. 11 is a box plot that shows an exemplary set of O.sub.2 saturation measurements acquired with a DRS probe using different cap arrangements.

[0175] There are nine recordings for each of the six setups, where each recording is depicted as a dot on the corresponding box plot. The central line across the box plot for each setup indicates the mean value associated with that cap setup. The area of the box immediately outwards of the central line shows the standard error of the mean (95% confidence interval) for that setup, assuming a Gaussian distribution of the measurements. The outer box for each setup indicates the standard deviation.

[0176] In particular, the arrangements used in this pilot study, shown in FIG. 11 in the following order are: [0177] 1. A bare probe without a cap. [0178] 2. A flexible black cap. [0179] 3. A rigid black cap with window of 0.25 mm thickness, where the probe is pushed probe onto the window portion. [0180] 4. A rigid black cap with window of 0.25 mm thickness, where there is a gap of 0.5 mm to 1.0 mm between the probe and the window portion. [0181] 5. A rigid black cap with window of 0.50 mm thickness, where the probe is pushed probe onto the window portion. [0182] 6. A rigid black cap with window of 0.50 mm thickness, where there is a gap of 0.5 mm to 1.0 mm between the probe and the window portion.

[0183] When no cap or a flexible cap was used (measurements 1 and 2 respectively), the results show variable oxygenation and a relatively large variance.

[0184] When a stiff cap was used with a window but there is an extra gap (of 0.5 mm to 1.0 mm) between the tip of the probe and the window surface (i.e. measurements 4 and 6), the results also show variations in levels of oxygenation and a higher degree of variance in general.

[0185] It is believed that the variations when no cap or a flexible cap was used are due to variations in spectroscope probe angle onto the skin surface cause a variation in specular reflections from the surface of the skin. The same is the case for the stiff caps with the extra gap between the probe tip and the window.

[0186] It can be seen that when the probe is brought into close proximity with the window portion (i.e. measurements 3 and 5) such that the gap is less than 0.50 mm (and potentially zero), the variance is significantly reduced.

[0187] Thus it will be appreciated by those skilled in the art that embodiments of the present invention provide a cap for use with probes such as DRS and microscope probes. The cap of the present invention may significantly reduce the ability for the probe angle to deviate from the desired angle (e.g. away from being normal to a patient's skin). Due to the rigidity of the cap, the cap does not flex when pushed around the subject's skin.

[0188] While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that the embodiments described in detail are not limiting on the scope of the invention.