Medical-surgical devices

Abstract

A tubular medical-surgical device (1, 1') made of a substantially transparent plastic material, having a shaft (1, 1'), characterized in that the material contains gas bubbles (12, 12') through the majority of the thickness of the material in at least a portion of the device, which gas bubbles are selected to enhance visibility along the shaft (1, 1') of the device under ultrasound imaging, the gas bubbles (12, 12') being continuously contained along the length of the shaft (1, 1'), and in that the size and density of the bubbles (12, 12') are selected to enable material flow along and within the device to be observed by eye.

Description

[0001] This invention relates to medical-surgical devices made of plastic material according to the preamble of claim 1.

[0002] The invention particularly relates to medical-surgical devices such as catheters that are visible under ultrasound observation.

[0003] Ultrasound imaging equipment is increasingly used during surgical procedures to monitor the location of a device within the body. The visibility of a device under ultrasound depends on several factors, including the difference between the acoustic impedance of the device material and that of the surrounding medium, such as patient tissue or body fluid, in which the device is located. This difference is relatively small for plastic devices such as catheters and can make conventional catheters difficult to locate. Even metal devices such as needles pose problems of visibility under ultrasound observation due to the directional nature of reflections. In some orientations, a metal needle may be clearly visible, but in others it may be considerably less visible.

[0004] Attempts have been made to increase the visibility of medical-surgical devices under ultrasound observation in various ways. The surface of the device can be modified, such as by forming grooves or notches in its surface. A reflective coating can be applied to the device, such as incorporating bubbles, as described in WO 98 / 19713 A1 and EP 0 624 342 A1. Alternatively, a metal marker can be attached to a plastic catheter.

[0005] US 4,582,061 A relates to a needle for insertion into the body, which has an ultrasound-reflecting scale of gaseous inclusions arranged regularly along the needle. The inclusions are arranged in a scale-like pattern at only a few widely spaced locations on the needle, allowing distances to be read directly from the ultrasound display. However, due to the short gaseous inclusions, the ultrasound display only displays a sequence of dots, so that the longitudinal extension of the needle can only be inadequately represented and recorded.

[0006] It is an object of the present invention to provide an alternative medical-surgical device.

[0007] According to the present invention there is provided a medical-surgical device of the type specified above, characterized in that the material contains gas bubbles through the majority of the thickness of the material in at least a part of the device to increase visibility along the shaft (1, 1') of the device under ultrasonic imaging, the gas bubbles (12, 12') being contained continuously along the length of the shaft (1, 1').

[0008] The device is preferably tubular, and the gas bubbles may be provided around the entire circumference of the device or may be provided in an area of the device occupying only a portion of the circumference of the device. The outer surface of the device may be smooth and uninterrupted by gas bubbles, and the device may have an inner surface that is smooth and uninterrupted by gas bubbles. The bubbles may have a diameter in the range of 1 µm to 50 µm and may be substantially spherical. The device may be extruded, with the gas bubbles being formed by the addition of gas during extrusion of the device. The plastics material is preferably substantially transparent, with the size and density of the bubbles being selected to enable a flow of material along the device to be observed by sight.

[0009] An embryo transfer catheter and its method of manufacture according to the present invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a side elevation of the catheter; Fig. Figure 2 is a side elevational view of a portion of the catheter of Fig. 1 on a larger scale; Fig. 3 schematically shows the manufacture of the catheter; and Fig. Figure 4 is a cross-sectional view through an alternative catheter.

[0010] With reference first to the Fig. 1 and Fig. 2, the catheter comprises a flexible shaft 1 and a hub 2 attached to the rear end of the shaft. The shaft 1 has a circular cross-section and a bore 10 extending along its length. The shaft 1 opens at its front, right patient end 11, which is atraumatically rounded. The shaft 1 is extruded from a clear, transparent polyurethane material and contains small, gas-filled bubbles 12, the size and distribution of which are selected to increase the visibility of the catheter under ultrasound observation. Typically, the gas bubbles have a diameter in the range of about 0.1 µ to 300 µ, preferably between 1 µ and 50 µ, with the most preferred range being 5 µ to 10 µ. The bubbles 12 extend through the entire thickness of the wall of the shaft 1 and may be spherical or have any other regular or irregular shape.The outer and inner surfaces 13 and 14 of the shaft may be smooth and uninterrupted by gas bubbles, or the bubbles may interrupt the surface.

[0011] The hub 2 serves to establish a connection with the shaft 1 and is formed from a rigid, transparent plastic material and then glued to the rear end of the shaft.

[0012] The shaft 1 is in the Fig. 3 using an extrusion machine 20. Polyurethane material 21 is heated and fed to the extrusion head 22 in the usual manner, but a gas such as nitrogen or carbon dioxide is also injected under pressure into the melt through the inlet 23. As the plastic exits the extrusion head 22, the gas expands to form the bubbles 12. The relatively gas-permeable nature of the plastic means that after production, the gas forming the bubbles quickly escapes and is replaced by air.

[0013] The shaft 1 can be continuously extruded at low cost without the need for any subsequent operations other than attaching the hub 2 and final forming of the patient end tip 11.

[0014] The catheter shaft could be formed by other melting processes such as injection molding or blow molding.

[0015] The bubbles could be formed in ways other than by blowing gas into the melt. For example, chemical foam generators could be added to the plastic material, such as: azocarbonomide, dinitrosopentmethylenetetramine, benzenephonohydrazine, 4,4-oxybis(benzenephonohydrazine), NN 1 -Dimethyl-NN 1-dinitrosoterephthalamide, azoisobutyronitrile, sodium bicarbonate, terephthalazide, or trihydrazinatrazine. Another way to form the gas bubbles would be to incorporate a liquid into the plastic melt, which evaporates during the melting process. Alternatively, solid, powdered dry ice (carbon dioxide) could be incorporated into the melt so that the dry ice particles become gas bubbles during the formation process. It might be possible to use other solids that undergo sublimation in this way. The bubbles could be formed directly as a result of a chemical reaction during polymerization and / or alternatively during crosslinking. The bubbles could be formed mechanically by beating the plastic in a liquid form, such as in the manner used to form latex foam.The bubbles could be formed by incorporating hollow microspheres of resin or glass. Alternatively, small particles of a soluble material could be added to the plastic melt and then dissolved away.

[0016] A shaft of this type can exhibit good visibility under ultrasound imaging without generating multiple echoes and can produce a good image regardless of the shaft's orientation. The shaft can be made sufficiently transparent to ultrasound energy to allow material flow along the catheter bore to be observed on the ultrasound image.

[0017] Because the catheter does not require any coating or separate marking, there is no need for subsequent assembly procedures and no risk of detachment. The catheter can be made from conventional medically approved materials, thus posing no new risk to the patient. Because the catheter surface can be smooth, the catheter can be inserted or advanced through an external tube with little friction. The smooth bore of the catheter ensures free flow along the bore, which can be important when the catheter is used for embryo transfer. The smooth surfaces also reduce the accumulation of a film of microorganisms on the catheter. The catheter can be manufactured without the need for metal components, which can be an advantage when the catheter is used while the patient is being viewed by magnetic imaging techniques.The catheter may be completely transparent to X-rays, or the plastic it is made of may contain an X-ray-opaque filler such as barium sulfate.

[0018] The bubble size and density can be selected so that the optical transparency of the plastic forming the shaft remains sufficient to allow material flow along the shaft to be observed with the eye.

[0019] There are several ways in which the catheter could be modified. For example, it might be preferred that the bubbles have a non-spherical shape and be oriented in a specific direction, such as lengthwise. This could be achieved by an obstruction in the extrusion die that constrains and elongates the bubbles as they flow through. Such an arrangement can result in an increase in ultrasound visibility while reducing the opacity of the shaft to the eye.

[0020] It is not essential that the bladders are provided around the entire circumference of the shaft. As in Fig.4, the bubbles 12' could be formed only in one or more strips extending along the shaft 1', such as in strip 40. This arrangement can be used when the shaft is required to have increased clarity so that the material within the catheter can be seen by the eye. The bubble region need not be continuous along the length of the catheter. Instead, discrete, separate regions of bubbles along the length of the catheter could be separated by regions without bubbles. A shaft for such a catheter could be manufactured by interrupting the gas flow to the extruder. If the bubbles are contained within a strip, this could be interrupted to make it discontinuous by extruding the strip using two auxiliary extruders, one comprising material with a blowing agent and the other comprising material without the blowing agent.Alternating extruders are turned on and off, allowing the strip to have sections containing bubbles separated by sections without bubbles. A catheter with an interrupted bubble region can provide a clearer ultrasound indication of the catheter's movement along its length and can also allow for clearer observation of material flow along the catheter, both by ultrasound and by sight.

Claims

[1] Tubular medical-surgical device (1, 1') made of a substantially transparent plastic material, with a shaft (1, 1'), characterized by in that the material contains gas bubbles (12, 12') through the majority of the thickness of the material in at least a portion of the device, which gas bubbles are selected to enhance visibility along the shaft (1, 1') of the device under ultrasonic imaging, the gas bubbles (12, 12') being contained continuously along the length of the shaft (1, 1'), and in that the size and density of the bubbles (12, 12') are selected to enable material flow along and within the device to be viewed by eye. [2] Device according to claim 1, characterized by that the gas bubbles (12) are provided around the entire circumference of the device (1). [3] Device according to claim 1, characterized bythat the gas bubbles (12') are provided in a region (40) of the device (1') which occupies only part of the circumference of the device. [4] Device according to one of the preceding claims, characterized by that the outer surface (13) of the device (1, 1') is smooth and not interrupted by gas bubbles (12, 12'). [5] Device according to one of the preceding claims, characterized by that the device has an inner surface (14) and the inner surface is smooth and not interrupted by gas bubbles (12, 12'), [6] Device according to one of the preceding claims, characterized by that the bubbles (12, 12') have a diameter in the range of 1 µ to 50 µ. [7] Device according to one of the preceding claims, characterized by that the bubbles (12, 12') are essentially spherical. [8] Device according to one of claims 1 to 7, characterized bythat the device (1, 1') is extruded and that the gas bubbles (12, 12') are formed by adding a gas during the extrusion of the device. [9] Device according to one of claims 1 to 7, characterized by that the gas bubbles (12, 12') are formed by the incorporation of hollow microspheres made of resin or glass, [10] Device according to one of the preceding claims, characterized by that the device is an embryo exchange catheter.

Images