DESCRIPTION

Technical field

The present invention refers to the curved dilator and its use in the procedure of targeted thoracic drainage. The technical field of the invention can be classified as devices for placing a medium in or out of the body. Additionally, the present invention can be classified as a device for inserting, manipulating and positioning the catheter for thoracic drainage.

Technical problem

Technical problem being solved by the present invention refers to the improvement (i.e. shortening) of the thoracic drainage procedure. The procedure makes use of the curved dilator for placement of the thoracic drain. Technical problem being solved by the present invention gives a more precise and simple positioning of the guide wire for the drain in the intended quadrant of the patient's chest, and of the drain inserted afterwards for pleural air or fluid drainage.

State of art

Regarding the number of thoracic drainage procedures performed in European countries that is approx. 1 per 1000 inhabitants per year, one can assume very developed state of art. Thoracic drainage is commonly performed by using two techniques: a classical surgical technique and a targeted wire-guided technique. In a study entitled ,,Targeted wire-guided chest tube placement: a cadaver study"; Protic A. et al; European Journal of Emergency Medicine, the precision of the targeted wire-guided technique (TWG) is compared to the classical surgical technique (CS) . In this study, the TWG technique showed significantly higher precision of the tube placement (79%) in comparison to the CS technique (30%) . It is important to emphasise that precise placement of the chest tube could have a significant impact on the quality of the thoracic drainage among emergency, as well as among less emergency patients.

The TWG technique, i.e. procedure and the kit, are disclosed in a US patent published in 1987 as US 4,813,929; inventor Semrad, N. The procedure describes a today common insertion of a guide wire into the pleural cavity through a needle, after which an incision parallel to the ribs near the introduced wire is performed; and an insertion of the catheter via guide-wire into pleural cavity. After removing of the guide wire the chest tube is introduced through the catheter into pleural cavity.

Standard medical practice nowadays includes dilators for chest tube placement. In the said technique we deal with thicker or thinner dilators, having axially symmetric shape, without the curvature along the principal axis - by which the ,,hole ^xv in chest is enlarged. With said ,,straight" dilators it is not possible to have a significant impact on the guide wire propagation, nor on the subsequent positioning of the drainage catheter. The present invention teaches about the curved dilator that solves the above cited technical problem.

Curved dilators are already well-known in procedures of percutaneous tracheotomy, i.e. creating an artificial opening in the throat - trachea, where a plastic tube is introduced enabling breathing to patients whose life is at risk. Such curved dilators are used only for expanding the adjacent tissue and are guided by the guide wire during penetration. As such, they cannot, nor they need to, change the direction of the guide wire during percutaneous tracheotomy procedure. Curved dilators are completely made of relatively soft materials which only aim to increase the basic diameter on the trachea so that the plastic cannula can be installed while said dilators were being guided through by guide wire.

Such dilator can be found in the ,,Ciaglia Percutaneous Tracheotomy Introducer Set", which sells the Cook Critical Care and is shown in Figure 1.

Another example of an advanced dilator is shown in the US patent published as US 6,637,435 (COOK INCORPORATED) and sold under the BLUE RHINO® trademark. The name of the curved dilator comes from the features of a rhino's nose (lat. rhinoceros) and that dilator represents the closest state of art - shown in Figure 2. Its main advantage is the reduction in number of dilators used while performing the percutaneous tracheotomy procedure. Nevertheless, due to its relatively soft tip, the said dilator in this procedure is used only after another (harder and smaller) dilator that is used to make the initial dilatation wide enough for the said dilator to be inserted.

Unlike the aforementioned curved dilators, the curved dilator according to the present invention significantly directs the guide wire, thus increasing the procedure success rate. In addition, its internal structure prevents ,,wrinkling" of the guide wire in the body of the dilator and enables precise guidance to the intended chest quadrant.

Furthermore, its tip is significantly harder than the tips of all the aforementioned curved dilators, thus making it unnecessary to use smaller and harder dilators in order to initially expand the opening after the needle is inserted, which is a common practice when existing curved dilators are implemented. Another advantage of the present invention is the fact that the chest tube is inserted in considerably less time, as it is no longer necessary to use two or more dilators in order to gradually enlarge the dilatation, but it is sufficient to use only the present invention for the said purpose. Summary of the invention

Curved dilator for targeted thoracic drainage consists of a partially curved part of the dilator, as shown in Figure 3. Cone- shaped mouth is at the rear end of the dilator and it narrows down to the canal diameter for wire guidance. Dilator is curved at an angle of α≥80°, wherein the angle β of approx. 60° defines the total length of the dilator. Dilator body progressively decreases in diameter after the straight part of the dilator, so that the tip of the dilator, which first enters the chest, is slightly larger than the diameter of the canal for wire guidance, for approx. 0,1 mm to ensure smooth wire guidance. The role of cone-shaped mouth facilitates introduction and visual control of the guide wire position in the chest. The diameter of the canal for the guide wire progressively decreases from cone-shaped mouth to its very tip, making it only slightly larger than the wire diameter. Such canal construction prevents accumulation of the guide wire in the dilator.

Description of drawings

Figures 1 and 2 show the prior state of art - longitudinal cross- sections of existing curved dilators found in the state of art for the percutaneous tracheotomy procedure.

Figure 3 shows the curved dilator for targeted thoracic drainage according to the present invention. Figure 4 shows the rear end of the dilator according to the invention concerned, whereas Figure 5 shows the tip of the dilator which is inserted in the chest.

Detailed description of the invention

Curved dilator for targeted thoracic drainage is shown in Figure 3. It consists of the body (1) which is mainly constant in diameter from the end (7) to the position (2). After position (2), the dilator's body (1) diameter progressively decreases; along with that it gradually curves for the angle α which approximately ends at position (3) ; while outer diameter maintains to decrease to the very tip of the dilator (4) .

Throughout the body of the dilator (1) runs a canal (5) for the guide-wire which begins behind the cone-shaped mouth (6) with the outer edge (7) . From the cone-shaped mouth (6) to the very tip (4) of the dilator the canal (5) has a diameter which progressively decreases in width towards the tip (4) of the dilator. This makes the canal (5) diameter only slightly larger than the wire diameter at the said tip (4) and about 2-3 times narrower than at the cone- shaped mouth (6) . Such construction of the canal prevents the accumulation of the guide wire in the dilator.

Maximal curvature of the dilator that is denoted with an angle α, is measured from the tangents that define the beginning and the end of the curved part of the dilator. When compared to the previous state of art, the values are the following:

Dilator dimensions from the previous state of art vary due to purpose of the dilator, as they were designed for a different procedure - percutaneous tracheotomy. For that reason, we are not making a dimension comparison with the dilator of the present invention, as it has a different purpose.

According to the preferred embodiment of the invention, the dilator body (1) from the beginning edge (7) to the position (2), when the curvature begins, is approximately 90 mm length and is constant in diameter, resembling a straight cylinder. The said length can vary, and the position (2) is situated at the place that forms 40%-60% of the total dilator length when measured from the said edge (7) . Practice showed that 90 mm is ergonomically the most acceptable length for safe dilator manipulation. The cone-shaped mouth (6) are situated within those 90 mm with approx. 9 mm deep, and with the outer diameter of said mouth (6) being approx. 9 mm and decreasing to approx. 3 mm, which is the initial diameter of the canal (5) - see Figure 4. Angle β defines the length of the tip (4) and in the present invention is around 60°±10°. The end part of the dilator that is inserted in the chest is not curved - from position (3) to the very tip (4) , and measuring about 15 mm. The said canal (5) diameter at the very tip of the dilator (4) is ca 1 mm. The largest diameter has the body (1) of the dilator at its very beginning, measuring ca 11 mm and remaining constant till the position (2) . Edge (7) is designed as a circular ring approx. 0.5 mm wide. Diameter of the dilator body (1) progressively decreases from position (2) all the way to the tip (4) . The total dilator length from the edge (7) to the tip (4) is ca 200 mm. The tip is designed in such a way that it slightly widens from the canal (5) , as illustrated in Figure 5, for approx. 0,1 mm to ensure smooth wire guidance .

It is also possible to form a canal (5) of a constant diameter from the cone-shaped mouth (6) to the tip (4) , but such a dilator would be slightly more difficult to be manufactured in serial production. Technical effect would be almost the same as in the preferred embodiment .

Advantages of such designed curved dilator for targeted thoracic drainage are multiple. The said dilator enables a precise navigation of the guide wire in the intended chest quadrant with a standard function of expanding the opening made in the chest.

It should be pointed out that dilators from the state of art do not insert the guide wire but instead follow the already introduced guide wire to perform the dilatation on such well-defined trajectory. Therefore, the dilators discussed in the state of art have a relatively soft tip (4) and a significantly wider canal (5) than is the case with the present invention. In order to ,,manipulate" the wire without accumulating it in the body of the dilator, cone-shaped mouth is designed to receive the wire. The cone-shaped mouth (6) enables the operator a visual inspection of the status of the wire and eliminates the possibility of accumulating the guide wire within the dilator. In addition, one can noticed a larger curvature of the dilator according to the present invention in comparison to the dilators described in the art, α≥80°. That is necessary for two reasons: the first being the specific thoracic drainage procedure and guiding the wire inside the chest, and the second is the possibility of imagining the position of the tip (4) by the operator, which is made more difficult if angle α<80°.

The dilator according to the present invention can be manufactured from medically acceptable materials, such as ,,Radiopaque polyethylene", a material commonly used the existing straight and firm dilators, or by using some other suitable material. Using the said material, the tip of the curved dilator will be firm enough to ensure that dilation of the opening will be safely performed, but at the same time flexible enough so it would not break while being manipulated (as is the case with firm plastic dilators) . Moreover, it would not lead to damage in the chest while manipulating the dilator in order to position the wire in the desired chest quadrant. In addition, the material used for manufacturing the dilator can be some other type of ultrasound or x-ray contrast material.

Furthermore, it is preferable (but not a condition) that the dilator according to the present invention is further covered by an hydrophilic layer from position (2) to the tip (4) in order to facilitate the penetration and dilation in the chest, thus minimizing the damage of the adjacent tissue. Such hydrophilic coating of the dilator is already described in state of art, see e.g. procedure of applying the hydrophilic layer as described in US 6,637,435 (column 4, lines 7-22).

It is also preferable that on its body part (1) , which extends from the edge (7) to the position (2), the dilator bears markings that enable the operator to receive the information regarding the direction of the dilator curvature. These markings can be designed as visual signs (e.g. in different colour); tactile bulges or some other technique which leaves no doubt about the tip (4) position once it is inserted into the patient's chest.

Applicability

The use of the dilator according to the present invention is the following: after the guide wire insertion in the pleural cavity through the needle (see state of art) , the dilatation of a hole through which the guide wire goes is performed by using the curved part of dilator according to the invention. The dilator stays in the chest up to the beginning of the curved part on the dilator, approximately at position (2) . Afterwards, the guide wire is pulled out up to the marking of 200 mm (dilator length) . Rotation around the main axe of the dilator handle enables the tip of the dilator to be directed towards the intended chest quadrant. In order to insert the chest tube for pleural air drainage (pneumotorax) , the tip of the dilator is directed to front and up. In order to insert the chest tube for pleural fluid drainage, the tip of the dilator is directed to back and down. In both situations the guide wire is placed deep into the chest up to the marking of 350 mm, parallel to the end of the curved dilator, which assumes that the wire will reach the intended position. When the curved dilator is extracted, a pleural fluid drainage is inserted for the indented task.

The application of present invention facilitates and improves the thoracic drainage procedure. Thoracic drainage has so far proven to be an extremely invasive procedure with limited success rate which can only be performed by well-educated medical staff. Application of the curved dilator during the thoracic drainage procedure would make the said technique (yet to be confirmed by the clinical studies) more available to less educated medical staff. At the same time it provides more reliable and better effect of the inserted thoracic drain. Indications for thoracic drainage are wide and include the following: traumatic and spontaneous pneumotorax, traumatic bleeding in the pleural cavity, malignant and other pleural haemorrhage.

According to present invention the described dilator is designed in dimensions to form a part of a kit for thoracic drainage procedure.