WO2009047512A1

WO2009047512A1 - Intravenous injection aid

Info

Publication number: WO2009047512A1
Application number: PCT/GB2008/003425
Authority: WO
Inventors: Kin Fai Kam
Original assignee: Kin Fai Kam
Priority date: 2007-10-12
Filing date: 2008-10-09
Publication date: 2009-04-16
Also published as: GB0719976D0; WO2009047512A4; GB2467244A; GB201006039D0; GB2467244B

Abstract

An intravenous injection guide (and a method of using such a guide) comprising a supporting base frame (23) and one or more guider arms (22) connected to the base frame (23) whereby the guider arm or arms (22) can be used so as to engage with a protrusion (20) from a transfusion set in such a way that the contour of the guider arm or arms (22) helps guide the trajectory of the transfusion needle (11) into the vein of the patient during the act by a user of attempting veni-puncture access for medicinal infusion or blood sampling. In addition a method of determining the path for an intravenous injection needle.

Description

Intravenous Injection Aid

The present invention relates to an intravenous injection aid system. In particular, the present invention enables the venipuncture process to be more systematic and easier.

Intravenous injections (or IVi) are common procedure for medicinal infusion or blood sampling. For some medical conditions, regular administrations of intravenous injections at home by nonprofessional or the patient are also common. This procedure is obviously not pleasant and requires not just skills, but confidence in giving a smooth veni-puncture action on a steady site. A successful veni-puncture process (i.e. putting the needle through the skin and accurately into the vein to the right depth, with minimal damage to the venous and surrounding tissues) requires accuracy, skill, confidence, calmness and a steady hand with minimal tension. This combination of requirements also coincides with an anticipated inflicting of pain and an anxiety of misplacing the needle, which can lead to further anxiety and additional psychological barriers to a successful injection.

It is an aim of the present invention to at least mitigate some of the above-mentioned problems by enabling an accurate veni- puncture to be carried out by eliminating much of the judgement and skill required during the act of veni-puncture. The invention consists of a guiding apparatus for a winged-type transfusion set where the needle of the latter can be assisted to follow a fixed or adjustable or "feel enhanced" injection trajectory path aided by the guide, thus enabling the IVi process to be made easier and safer. The winged-type transfusion set is typically of a modified butterfly® transfusion set, which consists of a buttefly® venous access needle connected to a winged body hub, which is further connected to tubing and connector which can be connected to a syringe. Furthermore, the current invention also includes design analysis which enables automation of the IVi process, either via direct robotic control and/or via aid in the design variations of the guiding apparatus mechanism.

There are a number of other inventions related to intravenous injection aids; these are typically concerned with aid for locating the vein or methods of stabilising the vein (see for example patents US2007161906, CN 1456364, US6066116, US5254095, US5147306) or a form of venipuncture assistance (i.e. CN1456364, US6652487, US4517971). None describe a device which works on the principles and design features of the current invention. Some of the embodiments of the present invention assist in the stabilising of the to-be injected vein, and aid the location and finding of a suitable IVi site. The location of an eventual suitable injection site must still be determined by the IVi administrator either by the usual sighting identification and/or sometimes with the aid of touching and feeling for the pulse or bulge of a vein. Some sophisticated imaging vein location technologies (e.g. US2007161906) have also been developed. However, once the injection site has been determined, the present invention assists the accurate insertion of the shaft of the venous access needle (hereafter simply referred to as the "needle") at the predetermined site, at a predetermined or adjustable path such that the IVi process can be performed with greater confidence, ease and safety. Once a suitable site is decided upon, the present IVi aid system increases the automation of the veni-puncturing process, since the administrator can accurately guide the transfusion needle into the vein without as much consideration or skill, during the veni-puncture process. The present invention can minimise potential tissue damage from over puncture or missing the original target injection site from some last moment error of judgement or through an unsteady hand or from the movement of the patient. The actual veni-puncture process is made easier and more certain with the benefit of reducing anxiety and also creating greater confidence for the IVi administrator. These benefits are particularly significant for inexperienced IVi administrators or patients with medical condition which may require self injection medication, or in situations where the selected injection site is subject to vibrations (e.g. the patient is inside a moving vehicle, such as an ambulance) or where the patient is uncooperative or an animal. Furthermore, the current invention could also be used as a teaching aid, to help improve a student's intravenous injection technique.

To achieve these advantages, the current invention includes an intravenous injection guide comprising a supporting base frame and one or more guider arms connected to the base frame whereby the guider arm or arms can be used so as to engage with a protrusion from a transfusion set in such a way that the contour of the guider arm or arms helps guide the trajectory of the transfusion set to achieve successful veni-puncture.

The invention also includes a method of using such an intravenous injection guide in combination with a transfusion set adapted to engage with the guider arm or arms of the intravenous injection guide.

The invention further includes a method of determining a useful applicational profile for the trajectory of a transfusion set during the execution of an intravenous injection. Embodiments of the invention are now described in more detail.

In order to understand the principle of one of the key design features behind the current invention, it is instructive to consider the physical model of the IVi process, which is described in detail below:

The mechanical aspect of the IVi process can be broken down to four steps, as shown in Figure 1, which is a schematic sketch of the side profile of the main components of a transfusion set, consisting of the shaft of the venous access needle 11, the body hub 13, and the corresponding tubing component 14.

Step 1: The IVi administrator must first identify an ideal vein and location of the injection site. Once a site is identified, the needle should enter the injection site, through the skin layer, and then into the vein at an appropriate angle. The steepness of the initial entry angle depends on how far the vein is below the surface of the skin and the size of the vein. The IVi administrator will in general decide on the steepness of entry before he/she starts the puncturing motion. The injection site should be as close as possible to the middle section of the vein to minimise unnecessary venous damage and vein movement. Hence, to summarise, the administrator takes aim, at desired injection site 10, with needle 11 at an initial entry angle θo with respect to the surface of the injection site 15. With the exception of Figure 15, the tubing component 14 of the transfusion set is omitted from the remaining figures as it is not an active part of the invention for these figures. Step 2: The administrator makes a sharp straight through venipuncture at fixed angle θo up to the desired depth. This desired depth optimally corresponds to when the tip of the needle has safely passed the upper side of the vein 16, but before it hits the underside of the same vein 17, the vein's side profile outline being shown as a dashed line. The length of this desired depth is represented by I₀, as measured along the longitudinal length of the needle.

Step 3: The administrator now inserts the needle further into the vein, accompanied by a simultaneous levelling of the needle (i.e. reducing the angle of penetration as shown by the direction arrow 18) until the needle is felt to be quite securely within the volume of the vein. Note for the purpose of diagrammatic clarity, the side vein profile (i.e. 16 and 17) has not be drawn in this and subsequent diagrams. Also shown in this diagram is the plane of the paper, defined by the (x,y) coordinate system.

Step 4: Assuming the veni-puncture has been successful, as can be assessed from observation of blood 'flashback' in the tubing of the transfusion set, the administrator stops the veni-puncture motion which may be accompanied by some minor adjustment, such that the body hub 13 part of the transfusion set is more or less resting stably on the patient's skin, at an orientation which ideally minimises tearing stress to the tissues at the injection site.

The assumed final resting angle of the needle with respect to the surface of the injection site 15 of this final motion is indicated by θ_f and the total length of the needle inside the patient's tissues is (Io + li), where U is the additional length of the needle that has been inserted during steps 3 and 4. If I₂ represents the length of the part of the needle outside the injection site 10, then the total length L of the needle satisfies the relation L= I₀ + Ii +I₂ -

The above steps summarise the physical essence of the IVi process, whereby the path and motion of the needle can potentially be predetermined. The following mathematical analysis shows a method of predicting this dynamical process.

The IVi action can be systematically represented by following the motion of any particular point in the needle. Let r represent the distance from the injection site 10, to the top of the needle (i.e. the point 12 where the needle and the body hub of the transfusion set meet). So, at injection site 10, r=0 and this represents the origin (r=0) of a polar co-ordinate system (r, θ). The motion of the IVi processes as described above can be analysed by following the motion of the point 12 (r, θ) relative to the injection site 10, at the origin.

Figure 2 shows a plot of point 12 in the polar coordinate system (r, θ). Here Pi₂ represents the path described between Step 1 and Step 2, and P₃4 is the path described in Steps 3 and 4, where r₃₄(θ) is the general equation representing this path. Note, the arrows in Pi₂ and P₃₄ simply indicate the temporal order of the dynamical IVi process.

From the expected motion and constraints, r₃₄(θ) can be approximated, without losing significant accuracy or generality, via a straight line which intersects (L-I_o,θ_o) and (l_2/θf). It can be readily shown that r_u(θ) = mθ + r₀ Eq.(la) where

m = — ϊ — and /-_Q = Z -Z₀ -Z₁ -ZW^ Eq. (Ib. Ic)

<9₀ -θ_f

Since the IVi process is a dynamical motion, the supposed paths can be emulated best from models which follow the time evolution of the IVi processes. The time dependency can be introduced via the speed at which the needle is being inserted in the IVi steps described. Hence, between Step 1 and Step 2, the needle can be assumed to be inserted at a particular rate Vi₂(t) over the period 0<t<to ,where t=0 corresponds to the start of the IVi process when the needle is just above the injection site 10, and about to enter the tissue, and to is the time when the depth of the needle inserted has reached Io.. The path Pi₂ can in general be described by

r_n{t) = L - and θ_n(t) = θ₀ Eq.(2a,2b)

for period O<t<t_o . This path is a simple straight line with gradient making an angle θ=θo with the local horizontal surface 15 of the injection site. It is most easy to visualise the path in Cartesian coordinates (x,y) where x=r.cos(θ )and y=r.sin(θ). Path Pi₂ in cartesian coordinates is

χ_n(t) = r_n(t)cosθ₀ and Jy₁₂(O = ri₂ (Osin0_o Eq.(2c,2d) or y_n = *₁₂.tan0_o Eq. (2d) Pi₂ is a straight line motion with the anticipated gradient tan(θo).

Similarly, for path P₃₄, which occurs over the period t₀ < t < tf , its equations of motion are: r_M(t) = L-l₀ - Jv₃₄(O* Eq. (3a)

Ό and hence from Eqs. (la,lb,lc)

In Cartesian coordinates,

*₃, (O =

sin 0₃₄(t) Eq.(4a,4b)

which gives the coordinates (x,y) of the path P₃₄ as a function of time, with the corresponding instantaneous gradient of the needle given by

The above equations provide the generic formulae of the path and direction which the IV needle follows. To illustrate the above analysis in determining the path structures, it is necessary to assign the velocity profiles Vi₂(t) and v₃₄(t). Figure 3 shows an illustrative simplified profile model during a typical realistic IVi process i.e. the needle is rapidly inserted into the injection site at an initial velocity V₀, whereby it slows down somewhat when the tip of the needle passes the first vein wall at about t=to. After that, the velocity profile must decrease with time (or equivalents with the depth of penetration), so that the needle motion in path P₃₄ must eventually come to a halt at the desired depth of penetration of (lo+li), at time t=tf. This profile can be approximated by quadratic or higher polynomial functions, or numerical representations if necessary. However, it is possible to obtain revealing analytical solutions, without losing the general significance of the result, by approximating the more realistic velocity profiles of Figure 3, by a constant velocity profile approximation where v₁₂(t)=v₀, and a linear decreasing function v₃₄(t) which satisfies the boundary conditions v₃4(t=t_o)=vo and v₃₄(t=t_f)=0. This is illustrated in Figure 4. The first part of this profile leads to the relations

and the latter profile leads to

so that

The path P₃₄ can be deduced by substituting Eq. (6b) into Eqs(3a,3b) or Eqs (4a, 4b).

Further insights into the IVi process can be gained by plotting the path predicted by this equation using a typical real life situation. Consider a shallow entry IVi process (e.g as most commonly associated with IV injection on the dorsum of the hand or where the veins tend to be more flat and lying close to the surface). Values for initial injection entry and final resting angles of the needles would typically be Θ_O=1O° and θ_f=3° respectively. The length of a typical IV needle is around L= 18 mm and the user would typically make a sharp initial insertion of around l_o=3 mm, which would typically take a fraction of a second e.g. to=O.3 second. The user then proceeds to Steps 3 and 4 of the IVi process, where the user has an element of flexibility of the rate and depth at which the needle will move. Assuming the injection is successful and the vein structure allows it, then usually, the user would insert a significantly longer section of the needle to the vein for stability. Depending on the habit and style of the IVi administrator, this would mean that Ii could typically take a value of around li=10 mm. The period of this process is not exact, except that it is anticipated that tf would be several times larger than to, with expected values of tf of between 1 to 2 seconds. By varying the value of tf in the above model, the approximate time can be determined, corresponding to the current model, when the needle has reached its final preset final resting position of θ =θf, and I₂=L-

Figure 5A and 5B show respectively plots of (x,y) and its corresponding instantaneous gradient y/x (equivalents, the slope of the needle) of the point 12. Similarly, Figure 6A and 6B shows the same plots but changing the values of θ₀ only to θ_o=30° which corresponds to another common IVi scenario, whereby the initial IV injection angle is much steeper and is most relevant for deeper lying or larger veins typically found at the crook of the arm (or technically known as the Ante-cubital fossa region). Note, point 12 is also known as the Top Needle point or the TN-point as labelled in the title of Figures 5A and 6A.

The above analysis and examples show that for a particular IVi situation, the desirable IVi path of the needle can be usefully anticipated and therefore potentially controllable. One method of controlling the needle to follow the desirable IVi path, is to handle or assist guiding a 'component' or part of the transfusion set which is rigidly connected with the needle, such that the point 12 follows the desirable path. This 'component' can be a thin rod or bar or specially adapted shaped structure extending out of the body hub 13 of the transfusion set, whereby this component acts as a gliding mechanism, or as a holding system for robotic handling control. Furthermore, this 'component' may be located away from the body hub 13 of the transfusion set. Figure 7 A shows a new type of winged like transfusion set (hereafter referred to as the "glider transfusion set" or abbreviated to the G-transfusion set) with this 'component' part labelled by the numeral 20. For illustration clarity, this gliding transfusion set is shown with the needle 11 pointing upward and tilting slightly away from the plane of the paper. There are two new parts compared to an ordinary transfusion set, namely a large flat extended tail wing-like component 19, which is rigidly connected to the original body hub 13 of the transfusion set, and a pair of the thin extended bar component 20, which is rigidly and symmetrically connected to each side of the wing-like component 19. Figure 7B shows the gliding transfusion set in the same side- on view in the same sense as Figure 1, where the dotted point 21 is the geometric central point of the tip of the thin extended bar component 20. For reasons that will become clear, henceforth, component 19 will be referred as the handling wing, component 20 as the glider, and the geometric central point of the tip of the glider (i.e. dotted point 21) will be referred to as the glider point or G- point. An important feature of the current invention is the control of the glider 20, or effectively the control of the G-point 21 path to realise an effective IVi aid. In the light of the above analysis on the point 12, it is an aim to emulate the same desirable point 12 path, via the equivalent path dynamic of another point (i.e. the G-point 21) away from the point 12 where it can be controlled or handled.

The length of the line joining the point 12 and G- point 21 is indicated by I₉ and the angle this line makes with respect to body hub 13 of the new gliding transfusion set is indicated by β, as illustrated in Figure 7B. By denoting the location of the G-point 21 by (X,Y), it can be readily shown that for point 12 with coordinates (x,y), that

X(t) = x(t) + l_g cos(θ{ή+ β)

_{/ x} Eq. (7a, 7b)

Y(t) = y(t) + L sm(θ(t)+β)

Note that for β=0, the gradient of the line joining the injection site 10, and the G-point 21 is the same as the gradient of the needle i.e. Y(t)/X(t)=y(t)/x(t).

Using the same set of parameters as Figure 6A (e.g. Θ₀=30⁰), Figure 8A shows the paths of the point 12 (curve A) and the G- points 21 (X,Y) with I₉=IO mm, β=40° (curve B) and I₉=IO mm, β=0° (curve C). This figure shows that the positioning of the G- point 21 (and so the glider 20) allows a flexible or optimal design solution for any IVi aid that may rely on the principle of controlling the path and gradient of the needle via a mechanical control and constraints placed on the movement of the glider 20. The G-point 21 location for the curve B case approximates the common relative position where an IVi administrator would be holding the needle by the folded wing of a conventional butterfly® wing transfusion set. Thus curve B illustrates best the path taken by the holding fingers of the IVi administrator when administering this particular IVi.

For comparison, Figures 8B shows the paths of the point 21 (curve A) and the G-points 21 (X,Y) with I₉=IO mm, β=40° (curve B) and I₉=IO mm, β=0° (curve C), except the other parameters are the same as those for Figure 5A (e.g. θo=lθ°). Note the above model involves two distinct set of parameters a) those specific to the nature of the IVi process involving human interaction and decision, corresponding to the variables θ_Of θf, I₀, U, to and t_f and b) those variables specific to the design of the IVi transfusion set, corresponding to the variables L, I₉, and β.

The above mathematical analysis can be used to define how the orientation and movement of the needle is best controlled via appropriate handling and constraints applied to a rigid body part of the transfusion set (i.e. control in which the G-point path emulates the desirable calculated IVi path). The analysis sets out design equations which can be used with relevant parameters to achieve accurate predictions of the G-point path, and thus also enable optimal design and control of any IV needle, via control on the G- point movement. The use of this analysis and equations can achieve the automation of the IVi administration process e.g. by robotic control. It can also achieve the optimum design of the G- transfusion set, with handling component 19, and gliders 20 enabling control of the G-point path via means of a "guiding apparatus".

In a preferred embodiment, the invention comprises two parts as described in a) and b) below: -

a) An apparatus which when attached at the vicinity of the injection site, enables an accurate, adjustable, and flexible IVi action to be performed when this apparatus is used in conjunction with the specially designed G-transfusion set. This apparatus will be referred to as the "stable guider" or S- guider for short, because once it is stabilized at the injection site, it provides a flexible and secure physical guiding path for the needle during the veni-puncture process.

b) A complementary designed wing type transfusion set (i.e. the G-transfusion set) designed to work with the S-guider.

The invention and several variants will now be explained and described solely by way of example and with reference to the accompanying drawings in which like reference numerals refer to like parts. Note with the exception of Figures 5A, 5B, 6A, 6B, 8A and 8B, all other figures are illustrations, so are not drawn with technical precision. For reason of clarity, in some of the following figures, some components are not drawn when it is not relevant to the description of the particular figure.

FIGURE 9 shows schematic of a S-guider at several viewing angles.

FIGURE 1OA shows a G-transfusion set for use with above.

FIGURE 1OB shows a G-transfusion set with stabilising flexible wings 27, and gliders 20 located on an extended handling tail wing.

FIGURE HA shows an S-guider without the guider arms.

FIGURE HB shows close-up views of the target vein stabiliser 28. FIGURE 12A shows a guider arm component 22 for shallow entry injection.

FIGURE 12B shows a guider arm component 22 for a G-transfusion set with gliders 20 positioned significantly away from the hub line.

FIGURE 13A shows detail features of the glider component 20.

FIGURE 13B shows an additional feature to the glider component.

FIGURE 14 shows a multi-adjustable S-guider.

FIGURE 15 shows a transfusion set stabiliser aid 30 in action.

FIGURE 16 shows an alternative handling wing design 19a.

Some of the difficulties of making a useful IV injection aid are the compact dimensions of the transfusion set and the relatively small and subtle movement of the IVi process (e.g. see parameters and results associated with Figure 8A or 8B). Furthermore, the IV injection aid system must allow flexibility in fine adjustment, and must not hinder the safe and efficient removal of the transfusion set. The current invention provides solutions which overcome these challenges via IVi aids based on innovative combined designs of the S-guider with the complementary G-transfusion set. Figures 9 1OA, and 1OB show such combination.

Figure 9 shows a S-guider with its main features at several viewing angles, suitable for use as an IVi aid for an injection site where the initial veni-puncture process is relatively steep e.g. θo around 30°, similar to the situation for Figure 6A. The S-guider consists of the following key components; a narrow base frame chassis 23 consisting a short side 23a and the pair of long sides 23b. Attached to 23b is a pair of guider arms 22, a pair of flexible wings 24, a pair of "needle depth" limiters 25, and an injection site indicator 26. Figure 1OA shows the G-transfusion set to be used with the S- guider of Figure 9. This is similar to the set shown in Figure 7, except the glider 20 is fixed to the body hub 13 (i.e. β=0°), and the dimensions (e.g. I₉, length of needle L, size of the handling wing 19 and the gliders 20) of the G-transfusion set are designed to work with the corresponding dimensions of the S-guider or vice versa.

By reference to Figures 9 and 1OA, the current invention works by: a) locating a suitable injection site location (i.e. corresponding to 10 in Figure 1), b) placing the S-guider on the location such that injection site 10 is at the geometric centre of the imaginary line joining the injection site markers 26, as indicated by the arrow heads in Figure 9. The S-guider can then be securely fixed to the patient by overlaying tapes on the flexible wings 24 and the patient's surrounding skin. Alternatively, the underneath of 24 may have non permanent adhesive properties which can be simply attached securely onto the skin. The IVi administrator can now hold the G-transfusion set via the handling wing 19 and manoeuvre it through the empty gap between the pair of guider arms 22 e.g. enter the gap, with the needle horizontal or pointing upward relative to the surface of the injection site. Note, the size and shape of the handling wing 19 enables the IVi administrator to effectively control the G-transfusion set without being hindered by the potential obstacles of the guiding arms 22, especially during the final stages of the IVi process when the transfusion set is at an low angle relative to the surface of the injection site. This means for example, the handling wing 19 needs to be bigger for deep initial entry IVi, because the guider arms 22 would be taller relative to the surface of the injection site. The gliders 20 can then be slotted into hooked end 22d of the guider arm 22 so that a glider 20 on each side of the S-guider engages with the hooked end 22d of the corresponding guide arm 22. Adjacent to the hooked end 22d is an edge 22a of the guider arm 22 which has a straight line contour for a distance between the hooked end 22d and a transition point 22c. On the other side of the transition point 22c is a contour edge 22b of the guider arm 22 which has a profile which is contoured. The straight edge 22a of each glider arm 22 corresponds to aiding the emulation of the initial venipuncture process associated with steps 1 and 2 of the IVi process (i.e. see Figure 1 or equivalents path Pi₂ of Figure 2). Step 3 and path P₃₄ in Figure 2 are emulated by the glider 20 following one or more contour edges 22b of the guider arm 22. One such contour edge is positioned on the contour arm 22, starting at point 22c and continuing for a distance towards the end of the arm 22 closest to the base side 23b. In addition, the path of the glider 20 may be further defined by an additional or alternative contour edge 22b positioned at the open end of the hook 22d (ie at the end of arm 22 furthest from base side 23b in circumstances where the arm 22 bends back on itself to form the hooked end 22d as shown in Figure 9). The needle 11 is then angled to aim at the injection site, so that it is parallel to the straight line edge 22a i.e. the line describing edge 22a is in the same direction as the straight line defining the direction of the transfusion set as shown in step 1 of Figure 1. The IVi administrator can now simply administer the veni- puncture according to the normal IVi process as described in the four steps of Figure 1, except step 2 and the transition from step 2 to the early part of the step 3 of the IVi processes are aided and constrained by the contour and constraints set by the straight line edge 22a and the contour edges 22b of the guider arms 22 respectively, the latter initiating the change of gradient of the needle. Note the guider arm 22 does not need to have contour edges 22b which follow the entire Step 3 veni-puncture process i.e. only the early part of the P34 path (see Figure 2) need to be emulated by the contour edges 22b of the glider arm 22. The rest of the P₃₄ motion in practice will be quite intuitive and natural after the initial guiding by the current invention. In fact, it would not be desirable to design an S-guider that follows a significantly greater portion of the P₃₄ contour path, because that design would be impractical and also not desirable anyway because that could restricts movement or correction of the G-transfusion set in the near final position or hinder the withdrawal of the needle. The final step of the IVi process is to stop the needle at a desirable penetration, which is achieved by the gliders 20 hitting the position adjustable needle depth limiters 25, which physically prevent the needle from travelling deeper than required. The limiters 25 should provide a sufficient resistance to the gliders 20, so that the IVi administrator is given a physical and enhanced feedback warning to stop the needle, and so prevent accidental or careless over puncture. Ideally, the limiters 25 resistance should not be an absolute hard stop. If the IVi administrator feels that he needs to insert the needle a little further, then the construction should enable him to do so by using a little more force to counter the nominal resistance of the limiters.

By this means the current invention has eliminated or at least reduced the most skilful and psychologically difficult parts of the IVi process. Also, the results of the theoretical analyses (e.g. Figure 8A) can assist in the design and engineering for the S-guider, given the particular parameters of the transfusion set and the IVi decision process.

The IVi process is complete with the G-transfusion set lying in its final position. Note the gliders 20 now also act as needle stabilisers, reducing the possibility of the transfusion set rotating about the injection site.

If the gliders 20 were positioned on the handling wing 19 instead (e.g. β≠O), then it would also be desirable to have a pair of appropriate sized stabilising wings 27 (Figure 10B) attached on the hub of the G-transfusion set.

Figure HA illustrates a base frame 23 of the S-guider, with the guider arms 22 removed from the illustration. It illustrates the component parts: short side of base frame 23a, connected to pair of long sides of base frame 23b, with part 23a connecting rigidly the latter components 23b. Side 23a is preferably shaped or positioned such that it minimises contact with the skin surface e.g. 23a can be slightly arched in shape. This is because near the vicinity of the injection site 10, it is desirable to prevent possible compression of the target vein ahead of the injection site 10 by any object which may be in contact with the skin. The pair of base frame long sides 23b comprise or are attached to the other chief components of the S-guider: the guider arms 22 (not shown), the injection site indicator 26, needle depth limiters 25 and flexible wings 24. Note the injection site indicator 26 is simply a marker or markers on the frame 23b (as indicated by the arrows, marked at the appropriate position commensurate with the engineering criteria as discussed above), or marked on a slightly protruding structure 28. This structure 28 can act as a vein stabiliser since some visible target veins can be quite prominent; the edge structure of 28 minimises side movement of the prominent vein making it more stable during the veni-puncture action. For smaller or less prominent target veins, a slight cusp or lip structure 28a (see Figure HB) added to the underside structure of the protruding structure 28 can assist vein stability. When the S-guider is securely fixed in position, the cusp 28a has the effect of slightly digging into the tissue surrounding the target vein 29, thus having a desirable effect of making the target vein more stable and prominent. Note, for the structure 28 to be particularly effective, an appropriate size and width separation would be chosen as is most appropriate for the size and width of the target vein. As set out above, the S- guider can be secured to the injection site area using the flexible wing structure 24 secured by tapes or backing adhesive. The flexible wings 24 shown in Figure HA are a variation of those shown in Figure 9. Each wing is connected to the long side frame 23b as shown. The wing can be split into two or more smaller strips, and shaped such that when tied down, it offers an improved secure arrangement against forced movement. Note the splitting of the wing into smaller strips can be essential for secure attachment to the injection site area, where there may be local curvature.

The needle depth limiter 25 is an adjustable slider moveable on a track connected to the side of the base frame 23b. The slider 25 may be situated on either side of the base frame 23b, depending on the situation and design of the G-transfusion set. In the current invention description, the prefered designs shown have the limiters 25 and the relevant tracks situated on the inside of the base frame 23b. This design enables the G-guider to be as compact as possible, which can be an important consideration since the vicinity of most injection sites are not entirely level surfaces. The example limiter 25 is simply based on a raised slider, which is moveable under control resistance along a track adjacent the inside side surface of the base frame 23b). When positioned appropriately before the veni-puncture process, it provides a positive feedback as well as physical resistance to unintentional excessive penetration of the needle, when the gliders 20 of the G-transfusion set hit the limiter 25. One possible design option is to have the base of the limiter 25 in contact with the skin, so that the friction between the base and the skin contributes to the control resistance, as well as providing an enhanced feedback when the gliders 20 reach the preset position of the limiters. The limiter is not totally immovable and so, unless it has reached the track limit, the transfusion needle can be further adjusted if necessary.

Figures 12A,and 12B show in more detail structure designs for the guider arm 22. Since the pair of guider arms 22 is symmetrically identical, only the profile of one of the arms is shown.

Part of Figure 12A shows a side profile of a guider arm 22 suitable for an initial shallow needle entry (e.g. Θ_O« 1O°) case. Comparing with Figure 9, note how the guiding edges (22a, 22b) of the guider arm 22 are now more commensurate with the profiles deduced for Figure 5A. As is the case for Figure 9, note only the paths Pi₂ and the early stage of P₃4 are aided via the profile of edges 22a and 22b. An important feature shown is that the size (i.e. length and size of the gap) within the hooked end 22d along the straight section edge 22a will always have space for the gliders 20 to manoeuvre, and is not tightly constrained. Some spare room for manoeuvre is also true along the contour edges 22b. This is a preferable design feature, since it offers flexibility and best feel for the IVi administrator. The current invention reduces the scope for injection error in the forward direction, whereas allowing backward and rotational freedom at the latter stages (ie steps 3 and 4) of the IVi process. A tightly constrained path could potentially limit the performance of the IVi aid because the path is less flexible and adds too much restraint, which will more likely interfere with the IVi process.

Also shown in Figure 12A is a bird's eye view of the S-guider together with a G-transfusion set ready primed (i.e. as in Step 1 of Figure 1) to carry out the IVi process. The gliders 20 are now inside the hooked end 22d adjacent the straight line edge 22a of the guider arm, with the tip of the needle 11 just above the injection site 10. One useful feature of the guider arm 22, indicated by this figure, is that only near the base region of the arm 22 is it in line with the base chassis sides 23b. Further towards the hooked end 23d of the guider arm 22, the arm 22 is closer to the needle 11 than are the sides 23b. There are three main advantages to this design: the guiders 20 can be shorter and therefore more rigid; the lateral available curvature deviation about the injection site is smaller; and the G-transfusion set can lie completely flat (rather than the tips of the gliders 20 resting on the base chassis sides 23b). Note, the latter is not an issue if the gliders 20 are placed above the level of the hub 13 e.g. as in the G-transfusion set shown in Figure 1OB.

Figure 12B shows a side profile of a guider arm 22 suitable for a deeper initial needle entry (e.g. θo«3O°), but for use with an S- transfusion set where the gliders 20 are situated on the handling wing 19 (e.g. similar to the situation for the result obtained for curve B of Figure 8A). Hence, one advantage of using such an S- transfusion set (where the gliders 20 are a further distance up from the hub 13) is it allows the design of a less 'cramped' S-guider.

The guider arm 22 shown in Figures 12A or 12B is securely attached to the base chassis edges 23b via a permanent construction casting. The end 22e of arm 22 is connected to the base of the guider arm 22. The IVi administrator would have to choose the appropriate S-guider with the appropriate angled guider arm 22 for the particular relevant target vein situation.

Alternatively, it is possible to design the guider arm base 22e to be detachable from the base chassis sides 23b. This can be done via a number of usual secure detachable means, a neat solution being the use of a powerful magnetic attachment method e.g. with powerful rare earth type magnets embedded in the guider arm base 22e, which is attracted to a magnetically attractive base chassis side 23b; or vice versa. This design enables quick interchange of the guider arms for optimal application of the current invention.

Figures 13A and 13B show some additional features to the design of glider 20. Figure 13A shows a cross sectional view 20a of the glider 20 of the G-transfusion set. To facilitate smooth guiding action along the guided paths 22a and especially 22b, the frontal side profile should be slightly sloped as shown magnified at 20a. Also implicit in the design is that the materials of the glider 20 and that of the contact regions between it and the guider arm (i.e. 22a and 22b areas especially) can be moved along each others smoothly. Figure 13B shows an additional feature in the glider 20 by way of the addition of a small upturn tip 20b to the end of the glider 20. The purpose of the tip 20b is to prevent excessive sideward mishandling during the venipuncture process, when the gliders 20 are inside the guided sections 22a, 22b of the guider arm. The length of the glider is selected so that the tip 20b is just on the outside of each guider arm.

Figure 14 shows an adjustable S-guider where the initial angle of injection (θo) can be adjusted, where the top illustration has high θo and the lower illustration has lower θo- The guider arm 22 can be rotated via a joint/hinge mechanism built at the base 22e of the arm 22 so easily to achieve the aim of varying θo. Furthermore, the length of the guider arm can also be varied via telescopic mechanism as indicated at 22f. The straight line section edge 22a guides the glider 20 through steps 1 and 2 of the IVi process. Guidance of the glider 20 through steps 3 and 4 of the IVi process is achieved by the inclusion of an additional slider 22g with a changing slope profile as shown in the Figure 14. In particular, the slider 22g has a profile designed to guide glider 20 (indicated by 22h) and a vertical edge adjacent that profile (indicated by 22i). This 'sloping' slider 22g is attached to the inside of the base chassis sides 23b in a similar way to the limiter 25 and has sufficient sliding resistance to resist movement when the glider 20 is only sliding past its contour profile 22h, but moves more readily when glider 20 hits the vertical side 22i. For high θ₀, the gliders 20 of the transfusion set would be guided by the high slope profile suitable for such IVi as shown on the top figure. For low θo, the slider 22g and the guider arm 22 (and if necessary the length of the arm via 22f) can be adjusted to provide the appropriate contour guide. The S-guider shown in Figure 14 is suitable for a G-transfusion set where the position of the gliders 20 is situated at the hub 13. An adjustable S-guider suitable for a G-transfusion set where the position of the glider 20 is not situated at the hub (i.e. β≠0) can be similarly constructed using the same principles described, where the appropriate paths can be calculated from the mathematical analyses set out above.

The following are some additional or alternative adaptations of the current invention:

1) The use of bendy or malleable long sides 23b for better fit on not so level surfaces such as the kooks of the arm. Alternatively, long sides 23b may be attached to short sides 23a via a resistive adjustable hinge/joint mechanism, so that sides 23b can be rotated relative to the surface 15 of the injection site 10 which may not be exactly smooth and flat.

2) The use of tiny electric driven motor embedded in any appropriate location in the S-guider, such that it causes the vein stabiliser 28 (and any cusp 28a) to rapidly vibrate e.g. giving an equivalent rapid stimulating massage around the target vein encouraging extra blood flow. The stimulating vibration is also significantly enhanced by use of a cusp 28a in the design, so that blood flow through weakly circulating or less obvious target veins may be significantly improved and can potentially be made more visible . The vibration would then be turned off during the venipuncture process. External power sources via batteries or mains connected via wire to the S-guider would be required for the S-guider to remain compact and light. In general, this functionality on its own is also an IVi aid. Thus the above massaging mechanism via the electronic vibrating or pulsing of a small sectioned vein stabiliser like 28, and potentially accompanied with cusp 28a, could be constructed as a standalone device, not necessarily built within the S-guider.

3) For some suitable injection sites, the Flexible wings 24 for secure attachment may be substituted by a wrap around hook and loop (e.g. Velcro® type) fastener.

4) The use of a light source (e.g. LED) with optional various colours to suit different skin tones, which may be embedded in the protruding side structure 28 to improve vein contrast. For example, reddish/purple colour light shone from the side level is particularly effective for making the target vein clearer. External power sources via batteries or mains connected via wire to the S-guider would be required for the S-guider to remain compact and light. 5) Frequently due to the tension from the tubing component 14 or movement from the patient or the IVi administrator, the transfusion set is pulled towards an orientation which is not ideal as it can cause unnecessary tissue damage, and sometimes even leads to the needle loosing the vein connection. Hence it is preferable that the transfusion set is stabilised by securing it e.g. by taping down. However this is often not performed because of inconvenience and because it can make needle withdrawal more difficult (the securing tape would need to be removed before the transfusion set can easily be removed). The current invention can facilitate a secure connection without the inconvenience of applying taping procedure by incorporating a simple weighty and flexible string or strap 30 connected to the S-guider (e.g. attached to the open end section of side 23b). The underside of the strap 30 is made of material which does not easily slip against the surface (i.e. skin) on which it lays. Furthermore, the flexibility of the strap enables it to contour and sit itself securely with the surrounding skin area. The string or strap 30 is connected so that it can be manoeuvred (i.e. rotated round) to rest itself securely on the tubing 14 of the transfusion set, once the veni-puncture has been made successfully. This is demonstrated in Figure 15, with non relevant components omitted for clarity. A flexible strap 30 is installed on each side of the S-guider base side 23b in order to facilitate the optimal placement option as the transfusion set tubing 14 could be in an awkward position. The weight of the strap prevents unintentional movement of the transfusion set during normal routine medication or blood sampling. When the transfusion set needs to be removed, the strap can simply be pulled away without any interference to the transfusion set. In general, on its own the above functionality associated with the stabilising strap 30, also constitutes an IVi aid. Thus strap 30 does not necessarily have to be connected with the S-guider as shown, and may be used on its own. 6) The use of a small protractor or angle indicator sited just next to the guider arm 22, as an additional aid for the venipuncture process.

7) The handling wing 19 described above consists of a single wing design with gliders 20 on each side. This necessitates that the handling wing 19 is relatively rigid and rigidly attached to the hub 13 of the transfusion set. However, for more efficient packaging, it is possible to design two flat handling wings 19a which are flexible about the hub 13, which can then be folded and held vertically to form the normal shape of handling wing. Depending on the particular design of the G-transfusion set, the gliders 20 could be positioned along the hub or on the handing wings 19a as shown in Figure 16. Standard simple locking mechanisms (e.g. plug and hole method) could be utilised so that when the two wings are held in the vertical wing position, the folded wings remain so.

8) An S-guider comprising only one guider arm 22. Such an S- guider could simply be similar to either of the sides of the S- guider associated with Figure 9, but without the edge 23a. Note that part of the wing structure 24 close to the base 23b would no longer be flexible, although malleable , so as to give this S-guider structural integrity and adjustability to rest securely near the injection site. Alternatively the base 23b could be shaped more broadly or have a malleable protrusion part to enable it to rest securely near the injection site. The S-guider would be applied next to the target vein with the single injection site indicator 26 pointing in the direction of the injection site. A G-transfusion set similar to those shown in Figures 1OA or 1OB would still be used, although its handling wing 19 could be reoriented to enable easier handling . For example, if a right sided single armed

S-guider is used, then the handling wing 19 of the G- transfusion set shown in Figure 1OA would be preferentially tilted away (in a rotational sense) from the central vertical position, with the orientation of the needle 11 and the single glider 20 remaining identical as before. This ensures that the handling wing 19 and the fingers holding such tilted handling wing 19 are not blocked or prevented from free movement due to the nearby guider arm 22. Positioning the handling wing 19 like this could also assist feel and handling. Such positioning would counter balance the slightly uneven force that would otherwise be felt due to the loss of a symmetrical reaction from a pair of guider arms. An advantage of the single armed S-guider is that it has a much smaller footprint, and is therefore not as affected by excessive local curvature deviation or bumps near the injection site.

The simpler S-guider described is expected to be disposable, although the more sophisticated versions described may be reusable after sterilisation. The material used for the S-guider should ideally be hypoallergenic or have anti-bacterial property, especially if it is designed to be reusable. Furthermore, to minimise light blockage, the S-guider, and especially the guider arm 22, should ideally be made of transparent or translucent materials e.g. clear acrylics plastics.

It is intended that the embodiments described above be considered only as illustrations of the present invention and that the scope thereof should not be limited thereto but be determined by reference to the relevant claims.

Claims

1. An intravenous injection guide comprising a supporting base frame (23) and one or more guider arms (22) connected to the base frame (23) whereby the guider arm or arms (22) can be used so as to engage with a protrusion (20) from a transfusion set in such a way that the contour of the guider arm or arms (22) helps guide the trajectory of the transfusion needle (11) into the vein of the patient during the act by a user of attempting veni-puncture access for medicinal infusion or blood sampling.

2. A guide according to claim 1 wherein the contour of each guider arm (22) is shaped such that when the protrusion (20) from the transfusion set engages with such contour or contours, and the transfusion set is used for veni-puncture, the contour or contours guide the needle (11) of the transfusion set initially on a linear trajectory and then on a trajectory through which the gradient of the needle (11) changes.

3. A guide according to claim 2 wherein each guider arm (22) is shaped so that following the guidance of the needle (11) along the linear trajectory and then along the trajectory through which the gradient of the needle changes, the guider arm or arms (22) exert no substantial constraints on the trajectory of the needle (11) during the subsequent phase of the veni-puncture procedure when the needle (11) is inserted further into the patient before it finally comes to rest.

4. A guide according to any previous claim wherein one or more of the guider arms (22) has a hooked end (22d) remote from the end of the guider arm (22) connected to the base frame (23).

5. A guide according to any previous claim wherein the supporting base frame (23) comprises a short side (23a) connecting a pair of long sides (23b).

6. A guide according to claim 5 wherein the short side (23a) is shaped so as to minimise contact with the skin.

7. A guide according to claim 5 or 6 wherein at least one of the connections between the short side (23a) and the long sides (23b) is jointed so that the sides can be rotated relative to each other.

8. A guide according to any previous claim wherein there are two guider arms (22).

9. A guide according to any previous claim wherein connected to the base frame (23) is at least one needle depth limiter (25) comprising a rigid or semi rigid projection so that if during the process of veni-puncture an attempt is made to advance the needle beyond a pre-set point, the projection will engage with the protrusion (20) from the transfusion set and provide a degree of resistance to further advancement of the needle (11).

10. A guide according to claim 9 wherein at least one of the depth limiters (25) is adjustable in its position in relation to the base frame (23).

11. A guide according to claim 9 or 10 wherein the depth limiters (25) allow the user of the transfusion set to exert a degree of force so as to achieve a deeper advancement of the needle (11).

12. A guide according to any previous claim wherein the base frame (23) has an injection site indicator (26) which marks the point at which the needle (11) is to enter the skin.

13. A guide according to any previous claim wherein the base frame (23) is connected to one or more flexible wings (24) to assist the secure attachment of the guide to the patient.

14. A guide according to claim 13 wherein the underside of the flexible wings (24) is coated in an adhesive material suitable to attach the wings (24) to the skin of the patient.

15. A guide according to any previous claim wherein the base frame (23) is connected to a wrap around hook and loop fastener for securing the base frame (23) to the patient.

16. A guide according to any previous claim wherein the base frame (23) has a protruding structure (28) in contact with the skin and adjacent the point where the needle (11) enters the skin such that when the guide is in use, the protruding structure (28) will press against the skin adjacent the relevant vein and reduce movement of that vein during the veni-puncture process.

17. A guide according to claim 16 wherein the underside of the protruding structure (28) includes a slight cusp or lip (28a).

18. A guide according to claim 16 or 17 wherein the protruding structure (28) can be vibrated by use of an electric motor attached to the base frame (23).

19. A guide according to claims 16 to 18 wherein the guide incorporates a light source to improve vein contrast and such light source is embedded in the protruding side structure (28) such that when in use the light source emits a light beam which is directed generally parallel to the surface of the skin.

20. A guide according to any previous claim wherein one or more guider arms (22) are detachable from the base frame (23).

21. A guide according to any previous claim wherein the angles of one or more guider arms (22) can be adjusted relative to the base frame (23).

22. A guide according to any previous claim wherein the length of one or more of the guider arms (22) can be adjusted by a telescopic mechanism.

23. A guide according to any previous claim having one or more slider arms (22g) connected to the base frame (23) so that their position can be adjusted relative to the base frame (23), each slider arm (22g) having an edge for engagement with the protrusion (20) comprising a curved portion (22h) and a portion substantially perpendicular to the base frame (22i).

24. A guide according to claim 23 wherein the slider arm (22g) slides in relation to the base frame (23) when sufficient force is applied at the substantially perpendicular portion (22i).

25. A guide according to any previous claim wherein the base frame (23) is made wholly or partly out of bendy or malleable material.

26. A guide according to any previous claim wherein the guide is connected to at least one weighty, flexible and moveable string or strap (30) made of a material which does not readily slip across skin.

27. A guide according to any previous claim wherein the guide incorporates an angle indicator positioned to measure the angle of a guider arm (22).

28. A guide according to any previous claim where any part of the guide is made from transparent or translucent material.

29. A method of carrying out veni-puncture by using a transfusion set having a protrusion (20), in such a way that the protrusion (20) engages with the guider arm or arms (22) of a guide of the type described in any preceding claim and the contour of the guider arm or arms (22) helps guide the trajectory of the needle (11) during the injection process.

30. A method according to claim 29 wherein the protrusion (20) is a thin rod or bar.

31. A method according to claim 29 or 30 wherein near and at the point where the veni-puncture process has been completed, the relative sizes and shapes of the protrusion (20) and the guide are such that the protrusion (20) does not extend beyond the inner surfaces of the base frame (23).

32. A method according to any of claims 29 to 31 wherein the protrusion (20) and guider arm or arms (22) are made of a material or materials such that the protrusion (20) and guider arm or arms (22) can slide smoothly across each other.

33. A method according to any of claims 29 to 32 wherein the cross-section of the protrusion (20) is sloped (20a) so as to assist the smooth engagement of the protrusion (20) and the guider arm or arms (22).

34. A method according to any of the claims 29 to 33 wherein the protrusion (20) has an upturn (20b) at its end or ends remote from the body hub (13) of the transfusion set.

35. A method according to any of the claims 29 to 34 wherein the transfusion set has a flat extended tail wing-like component (19) which is rigidly connected to the body hub (13) of the transfusion set and the size and shape of the tail wing-like component (19) is such that any user can hold the component (19) and manually control the trajectory of the needle (11) without being hindered by the potential obstacles of the guiding arms (22).

36. A method according to any of the claims 29 to 35 wherein the protrusion (20) is rigidly connected to each side of the body hub (13) of the transfusion set.

37. A method according to claim 35 wherein the protrusion (20) is rigidly connected to each side of the tail wing-like component (19).

38. A method according to claim 35 or 37 wherein the tail wing-like component (19) comprises two elements (19a), each being an individual handling wing which is flexible about the body hub (13) but which can be brought together with the other element (19a) to lock relative to the body hub (13) so as to define a single tail wing-like component (19).

39. A method according to any of the claims 29 to 38 wherein the transfusion set has a pair of stabilising wings (27) attached to the body hub (13) of the transfusion set.

40. A method of determining a path for an IV needle to follow during part of the veni-puncture process, between the point when the needle has just completed the linear entry motion and the point where the positioning of the needle is complete, by use of the following formulae:

For to <t< t_f,

r(t)= L-l_o -- \t_f{t-t_o)-Ht^> -A

where: r(t) is the distance of the point (the TN-point) where the needle joins the body hub of the transfusion set from the injection site; θ(t) is the angle the needle makes with the skin surface at the localised injection site; θo is the initial angle at which the needle enters the skin surface at the localised injection site; θf is the final angle of the needle relative to the skin surface at the localised injection site;

L is the length of the needle;

1₀ is the length of the desired depth of penetration of the needle during the initial linear entry of the needle into the vein;

1₁ is the additional length needle that is inserted following the initial linear entry into the vein;

V₀ is the velocity of the TN-point as the needle penetrates the skin and is equivalent I₀ divided by t₀; t represents the time that has elapsed during the venepuncture action, starting when the needle hits the injection site; to is the time at which the needle has passed the upper side of the relevant vein wall and at which time a length I₀ of the needle has penetrated the skin; tf is the time at which the needle comes to rest at its desired position within the vein.

41. A method of determining a path as described in claim 40 where θf is about 3°.

42. A method of determining a path as described in claim 40 or 41 where I₀ is about 3mm and to is about 0.3 seconds.

43. A method of determining a path as described in any of the claims 40 to 42 where Ii is about 10mm and t_f is approximately between 1 and 2 seconds.

44. A method of determining a path as described in any of the claims 40 to 43 where θo is about 10°.

45. A method of determining a path as described in any of the claims 40 to 44 where θo is about 30°.

46. A guide according to any of the claims 1 to 28 wherein the profile of the contour of one or more guider arms is determined by reference to the formulae set out in any of claims 40 to 45.

47. A method of carrying out an intravenous injection by using a transfusion set wherein the trajectory of the transfusion set is controlled by robotic or other automated mechanical control so that the path the needle follows, between the point when the needle has just made initial entry to the vein and the point where the positioning of the needle is complete, is determined by reference to the formulae set out in any of the claims 40 to 45.