WO2016034910A1

WO2016034910A1 - Device for assisting in the detection of body cavities

Info

Publication number: WO2016034910A1
Application number: PCT/IB2014/001684
Authority: WO
Inventors: Andrés Ernesto SALGUERO BELTRÁN; Augusto BUENDÍA RESTREPO
Original assignee: Salguero Beltrán Andrés Ernesto; Buendía Restrepo Augusto
Priority date: 2014-09-02
Filing date: 2014-09-02
Publication date: 2016-03-10
Also published as: CO2017002996A2

Abstract

The invention relates to a medical device for the detection of body cavities, comprising electronic means for measuring the bio-impedance of the tissue in contact with the tip of penetrating means, by means of electrodes that are removably inserted, using a stylus, in the hollow portion of said penetrating means.

Description

DEVICE FOR ASSISTING IN THE DETECTION OF CAVITY

BODIES

1. FIELD OF THE INVENTION

The present invention relates to a device for the detection of body cavities by means of puncture elements. For example, this device can be used to assist in the detection of epidural space.

2. BACKGROUND OF THE INVENTION

In the state of the art, the correct location of closed body cavities to perform some type of diagnostic or therapeutic procedure such as the supply of a pharmacological agent, or perform surgical procedures in situ, is performed indirectly through instrumental support. In very few cases the doctor can make a verification of such location, exclusively through his senses. Anesthesia is one of the most frequent procedures in medicine, in particular, epidural anesthesia that is used in the preparation of major procedures such as labor and various types of surgery, be they gynecological, urological or orthopedic; being indicated primarily for elderly patients. Epidural anesthesia is of the highest occurrence because the birth rate worldwide exceeds 134 million people ¹ and in developed countries 60% of deliveries are performed with epidural anesthesia ² , while in developing countries the percentage It reaches up to 40%.

1 The World Factbook 2013-14. Washington, DC: Central Intelligence Agency, 2013, USA.

² Michelle JK Osterman, MHS; and Joyce A. Martin, MPH "Epidural and Spinal Anesthesia Use During Labor: 27-state Reporting Area, 2008". In National Vital Statistics Reports, Vol. 59, No. 5, April 6, 2011. US Dept. ofhealth & human services. Hyattsville, -MD, USA. The application of epidural anesthesia requires locating the space left by the spinal cord in its path through the internal duct that has the spine. This space mainly contains the nerve roots projected from the spinal cord, arteries, an extensive vascular network of minor vessels, loose connective tissue and distributed semi-liquid fat.

The insertion of the epidural needle is a surgical act, during which the doctor experiences sensory feedback of the mechanical resistance that the tissues oppose to the passage of the needle, which can be modified, in some cases, by the softening of the ligaments in parturient women and others, due to excess fat in obese patients or to particular pathological conditions. However, the most important sensory component is the experience of loss of resistance to injection of media, liquids or gaseous, through the needle. Such sensory feedback conditioned to multiple variants makes epidural puncture risky due to the high probability of causing perforating trauma to the meninges. Reducing this risk is the responsibility of the anesthesiologist, who for this must develop surgical skills that are challenged by anatomical and physiological variations according to the patient's conditions. The loss of resistance as the main evidence in the location of the epidural space is a practical method with a high success rate. However, the risk of accidental perforation of the meninges is also high for the following reasons:

- In the first place, it is common for the needle to drag tissue debris into its interior, such as fat, muscle fragments or ligaments, creating a tamponade - which will not allow resistance to air or liquid flow to be reduced, leading to the doctor to erroneously conclude that it has not reached space and, consequently, to continue advancing the needle until the meninges are perforated.

Another cause is the uncontrolled penetrating movement due to the abrupt change of the force exerted by the doctor on the needle when crossing the ligament yellow, since in the direction of advance of the needle, this is a dense but thin fabric, the perforation is abrupt and the transient to move from a force control to a position in the manipulation of the needle, can cause a delay in the recovery of movement control, which results in unwanted puncture of the meninges.

-The second event that will occasionally lead the doctor to an erroneous conclusion, consists of the intra-vascular puncture that occurs when the tip of the needle enters a blood vessel, compared to the pressure exerted by the doctor on the plunger of the syringe, the pressure there will be low presenting loss of resistance, so the doctor could conclude that it is in the epidural space and would proceed with the application of the anesthetic, which will be injected into the blood vessel without reaching the nerve roots that are sought to block.

In the search for instrumental solutions to these problems, methods based on two main mechanisms have been disclosed: The first, as in the loss of resistance is based on pressure differentials and the second is based on the characterization of electrical impedance of the surrounding tissue at the tip. Below are realizations in these categories:

Among the mechanisms based on pressure differentials (pressure loss), is that described in US Patent 4,175,567. In said patent a device is revealed that indicates through the deflection of a membrane, if the pressure differential between the tip of the epidural needle facing the outside is negative or positive. In particular, when using said device, when the epidural space is reached the membrane will indicate a negative differential, emulating the technique of the "hanging drop" based on the fact that the pressure in the epidural space is negative with respect to atmospheric pressure.

Likewise, there are other patent documents such as patents No. US 4,801, 293 and US 4,9 9,653 which teach respectively, the detection of the negative pressure to inject a pressurized gas and a sensor to detect the pressure drop when entering the epidural space and with this signal retract the sharp means and avoid perforation of the meninges. Similar mechanisms are disclosed in patents US 5,205,828, US 5,902,273, US 6,773,417 and in the patent application with publication number US 201 1/0060229.

In patent application EP058259 a pressure measuring device is presented, with an auditory indicator, which adapts to the syringe and needle with which the technique of resistance loss is performed. Another embodiment is disclosed in publication US201 1/0224623 that uses a sealed chamber to which a spring-loaded plunger and mechanism and conductive flow means are incorporated into an epidural needle, the mechanism applies pressure to the plunger so that when at the tip of the needle has not blocked the liquid is injected and an alarm is generated. A method and device for monitoring pressure change is presented in WO2008 / 03890.

However, devices based only on mechanisms that use pressure differentials are subject to the same sources of error in the detection of pressure change, such as plugging of perforating media due to the accumulation of tissue detritus and intra puncture. - accidental vascular. Another disadvantage of such methods is the elimination of the sensory feedback of the anesthesiologist in the detection of the loss of resistance, excluding their expertise in the correct assessment of the phenomenon, and relegating said detection to the actuation of the mechanism.

On the other hand, among the mechanisms based on bio-impedance, they are described in the following patents and patent applications:

- US 3682162 discloses a device comprising a syringe and a hypodermic needle with electrodes and means for electrical stimulation. - US Patent 64401 18 discloses a device based on bioimpedance, as well as methods of manufacturing special needles for carrying electrodes for such measurements. - The patent application with publication No. US 2010/0286507, reveals an epidural needle with permanently incorporated electros to perform bio-impedance measurements.

- The patent application with publication number WO20090 9707 refers to a hand-held medical device, which replaces the materials and methods of the resistance loss technique and those for the measurement of impedance by means of a hollow needle with electrodes incorporated in it. Such devices are also disclosed in patent application No. US 2003/0083641 and US2006 / 0167404 and the latter has as main purpose the detection of blood vessel entry.

However, the embodiments that are based on the bioimpedance measurement, mentioned above, require special piercing means that permanently integrate the conductors and electrodes for measurement, leading to the modification of the usual means such as epidural needles. Another important aspect that is not addressed in these embodiments is the measurement error associated with the application and measurement of electrical signals through electrodes of reduced size in biological media. In some of these embodiments, the electrical means for calculating the bioimpedance are incorporated into a manual unit that the physician must support, modifying the ergonomics of the traditional medical technique. In other embodiments, external cables are used to connect the electrical bioimpedance calculation means with the conduction means incorporated in the penetrating means, adding complexity in the assembly and possible sources of measurement error.

From the technical problems presented with the known devices, methods and mechanisms for the detection of the epidural space in the state of the art such as the risk of dragging into the needle of the tissue detritus device such as fat, muscle fragments or ligaments, uncontrolled penetrating movement due to the abrupt change in the force that r.

the doctor exerts on the needle when crossing the yellow ligament, increase in the incidence of punctures in the meninges and the intravascular puncture that occurs when the tip of the needle enters a blood vessel against the pressure exerted by the doctor on the plunger of the syringe, there is a need for a device for the detection of epidural space that does not present these unwanted consequences and that does not increase uncertainty in the detection of said space or impose an increase in the complexity of the procedure compared to the traditional method of detection of the loss of resistance.

3. GENERAL DESCRIPTION OF THE INVENTION

The problem posed in the present application is the need to provide a device to assist the anesthesiologist in the timely detection of the epidural space that complements the standard technique of loss of resistance, increasing the safety of the procedure, both for the patient, as For the anesthesiologist, be this expert or be in the early stages of your learning curve. Consequently, said device allowing the appropriate location of the epidural space. Although, e | User of the device (the anesthesiologist) continues to perform the traditional technique of loss of resistance, it provides an increased certainty in the detection of the epidural space because the device indicates the discontinuity of the tissue that occurs when reaching the epidural space. The minimum dimensions of the device allow its assembly inside the traditional needle in a non-disruptive way. Therefore, the syringe and epidural needle of the standard and commercially available method can be continued. In addition, advantageously, said device does not require cable connections for electrodes, for example, external reference, or cannulas outside of said protocol. In such a way that, the user (anesthesiologist) continues with the usual manipulation of the needle and syringe and once the epidural space is located, the device is removed from the needle and discarded, to continue the application of the anesthetic. The invention presented here offers a set of advantages that allows its inclusion in the standard epidural space detection protocol in a slow manner. The experienced anesthesiologist remains in control of the procedure by applying and increasing his expertise while, the anesthesiologist in training or with little experience will continue to be trained in the standard technique with additional information to support his decisions. The inclusion of the device in the standard package for epidural anesthesia does not require modification of existing materials and supplies. The device is manufactured by means of current methods and materials in the medical supplies industry, so its cost is low. In the same way, it is considered to be of a single use, maintaining the safety conditions for the patient. The above characteristics allow it to be used, in facilities and clinical situations of varying complexity. A first aspect that the present invention focuses on is to reduce the accumulation of biological material on the stimulus / registration electrodes when the needle is penetrating the tissues in its path to the epidural space. The main adverse effects of this accumulation are the formation of short circuits between the electrodes due to conductive films of body fluids between them, and the shielding of the electrodes due to the accumulation of tissue debris. In both cases, electrical signals are blocked or distorted, either from stimulation or registration, on the tissues, thus preventing the characterization of their bioimpedance. Another aspect that the present invention focuses on is the appropriate constructive characteristics for the physician to perform the technique of resistance loss in the presence of the embodiment described herein. This implies that the air or liquid in the syringe can flow without resistance to the flow of air or liquid from the syringe when the doctor applies pressure to the embolus.

In particular, to solve the technical problems mentioned above, the present application provides a medical device for detecting body cavities, with electronic means for measuring the bioimpedance of the tissue in contact with the tip of penetrating means by means of electrodes that are removably inserted by means of a stylet; in the hollow portion of said penetrating means and within the stylet there are conductive means that connect the electrodes with said electronic means, which in turn produce a signal indicating the detection of the body cavity. Said medical device comprises:

An array of non-coplanar electrodes each embedded in a different plane or facet, the surface of each facet is formed with a rigid substrate, which is an electrical insulator, which embeds the electrode, and exposes only the electrode region for contact with the biological tissue, so that the substrate forms a surrounding area from the electrode to the edges of the facet that contains it. The plane formed by the surface of each facet is not to co-plan with the planes formed by the surfaces of the other facets of the arrangement. The planes formed by the surfaces of adjacent facets with common edge, have an angle, measured in the normal plane (625) to said common edge, greater than 180 °, where said faceted arrangement (612) of non-coplanar electrodes reduces the creation of short circuits between electrodes due to the formation of conductive films of body fluids.

Centering means for the stylus to concentrically travel the hollow portion of the penetrating means, creating lumen between the inner wall of said penetrating means and the stylet, so that the gas or liquid injected from the syringe flows with little opposition. In this way, the anesthesiologist remains in control of the procedure by performing the technique of resistance loss.

4. BRIEF DESCRIPTION OF THE DRAWINGS

The invention to assist in the detection of body cavities, for example of the epidural space presented here, will be more easily understood with the detailed description accompanied by the following set of drawings, in which: Figure 1 illustrates the way in which the doctor takes the needle and epidural syringe in his hands to perform the technique of loss of resistance to detect the epidural space. Figure 2 illustrates the temporal assembly line of the invention between the syringe and the epidural needle, as well as a perspective view of how the system looks with the epidural cavity detection device mounted in the syringe and needle kit. Figure 3 illustrates how the epidural space detector incorporated into the syringe and needle pair does not affect the way in which the doctor takes said assembly into his hands compared to the traditional technique pair (illustrated in Fig.

Figure 4 shows three views of the device: (i) the first in perspective, (ii) the second is a perspective cut of the syringe, detector and syringe assembly, and (ii) the third is a sectional view of how The hollow shaft of the needle concentrically contains the stylus of the sensing device.

Figure 5 shows a longitudinal section of the temporary assembly of the syringe, detector device and the epidural needle.

Figure 6 presents three views of the tip of the epidural needle with assembly of the electrode array whose substrate is faceted, wherein said array has two electrodes for bioimpedance measurement.

Figure 7 presents two views of the tip of the epidural needle with assembly of the faceted array of electrodes, wherein said arrangement has four electrodes for bioimpedance measurement. 5. DETAILED DESCRIPTION OF THE INVENTION

Figure 1 shows the prior state of the art, for location. of the epidural space in which the traditional 10-needle syringe pair 20 (which constitutes a penetrating medium) is used. In this technique, according to the doctor Anesthesiologist pushes the holding fins 201 of the needle into the body, presses the plunger 101 of the syringe to try to inject the air, or liquid. If there is no flow of said content, the plunger returns to its initial position due to the elastic decompression of the air, or in the case that there is only liquid, it will not move due to the incompressibility of the same. The doctor will consider such resistance as evidence that the surrounding tissue blocks the tip of the needle and the epidural space has not been reached as long as the depth reached by the needle and the specific conditions of the patient support such a conclusion. Therefore, it will continue to sink the needle until there is no blockage in the tip and there is no resistance to the flow of air, or liquid, as the case may be; which generally indicates that the epidural space has been reached.

A preferred embodiment 60 of the present invention is shown in Figure 2, in which the syringe 10 and the assembly 50 are inserted between the syringe 10 and the doctor performs the manipulation described above, however, now the device will emit a signal through indicators 606 that the tip of the needle 203 is in the epidural cavity. With this information the doctor will have more evidence to conclude if he has reached the epidural space. Once this conclusion is reached, the device and the syringe are removed and discarded, to continue the application of the anesthetic. Figure 3 shows that the inclusion of the device is minimally disruptive, allowing the doctor to perform the standard protocol maneuvers.

A view of embodiment 60 is shown in Figure 4A whose external body has a base 601, indicators 606, a concentrator 610 with flow outlets 609, stylet 602, centering fins 61 1 and at tip 603 the electrode array 620 Figure 4B shows a sectional view of the assembly 50 composed of a syringe 10, device for detecting the epidural space 60 and the epidural needle 20, where it is shown in detail how the tip 102 of the syringe is tightly coupled with port 607 at base 601. Said port connects with the ducts 608 of the concentrator 610 which, in turn, is tightly coupled with the Luer type connection port 204 of the epidural needle, continuity is created in the pavilion of this port 204 of flow with the syringe through the perforations 609 of the concentrator 610 of the device. This The concentrator serves as a support from which the stylet 602 is projected to its distal end, whose tip 603 houses an array of electrodes 620, described below, which in turn is aligned with the tip of the needle 203. In the detail view 65 of figure 4C, the cross section 652 of the needle is shown which, concentrically, embeds the cross section 651 of the stylet 602, of the latter projecting at least three centering fins 61 1, which position the stylet so that its entire path is concentric with the needle and a hollow runner 653 is formed, through which the air or liquid from the syringe flows with low resistance. The constructive characteristics mentioned, allow the physician to continue executing the technique of resistance loss, in the presence of the preferred embodiment described herein.

In Figure 5, it is detailed that in the base 601 there is a concentric chamber 632 that houses the electronic means with its energy source, to perform bioimpedance measurements, which are widely known in the state of the art, so that They are detailed in this description. To said means the electrode arrangement 620 and the metallic axis 202 of the needle are connected through the conductive means 630, embedded along the stylet, all in its entirety to perform the bioimpedance measurements of the tissue in contact with the tip of the entire assembly 50. In the centering fins 61 1 proximal to the concentrator 610 of the device, the electrodes 631 are exposed, which make electrical contact with the metallic axis 202 of the epidural needle. Preferred embodiments of the present invention are characterized in that they identify with certainty the epidural space. To achieve this it is necessary to reduce the sources of contamination of the stimulus / measurement signals. One of the main causes of contamination lies in the accumulation of tissue debris on the electrodes. When it comes to blood or other body fluid, liquid layers will appear that short-circuit them, producing a false measure of low impedance. The inventive principle, exemplified below, is applied to break with the continuity of such conductive layers. An embodiment of such a principle is presented in Figure 6. and part A shows the array of electrodes 620 inserted in the tip 202 of the epidural needle and surrounded by its bezel 204, where it is observed that the two electrodes 621 and 622 are embedded in different facets / planes 620i and 620j, respectively, of the rigid faceted layer, which is electrical insulator, only the electrode region being exposed for contact with the biological tissue . Each facet forms a polygon with adjacent edges with other facets, when one of these embeds an electrode, it does not touch any of the edges of the electrode, leaving for or so many areas of guard substrate that extend from the respective electrode to the edges of the facets that contain them. From the set of views of Figure 6 it can be seen that the plane formed by the surface of each facet is not co-planar with the planes formed by the surfaces of the other facets of the arrangement. In the profile view of Figure 6C it is shown how adjacent facets 620i and 620j, with common edge, have an angle Θ, greater than 180 °, measured in a normal plane 625 to said common edge. This angulation between facets prevents the continuity of conductive layers between two or more electrodes since in the boundaries between facets forces are created that are greater than the surface tension of the liquid.

In the embodiment shown in Figure 6, with at least two electrodes 621 and 622, these align with the longitudinal axis 618 of the needle. Such alignment divides into two symmetrical portions of the faceted stratum of the electrode array, the first portion with facets 620a through 620d, and the second symmetrical portion with facets 620e through 620h. Between the distal electrode 621 and the tip of the stylet, the substrate has two symmetrical facets 620a and 620e with a common adjacent edge. This arrangement, in the form of a keel, has the purpose of separating the body tissue as the needle advances into the epidural space, so that upon entering it, any remaining tissue is removed from the electrodes.

While it is possible to bioimpedance measurements using only two electrodes 621 and 622, is known in the prior art ³ ^'4 which in this configuration

³ YÉLA OS, D., CASAS, Ó., BRAGÓS, R. and ROSELL, J. (1999), Improvement of a Front End for Bioimpedance Spectroscopy. Annals of the New York Academy of Sciences, 873: 306-312. The measured impedance includes the impedance of the tissue of interest plus the impedance that occurs at the electrode / tissue interface, which in general is much greater than the tissue impedance. This phenomenon is exacerbated for electrodes with small contact area and in preferred embodiments of the present invention, the electrode diameters are between 100μιη to 200μηι. This is due to the fact that the sizes of the epidural needles, for regular use, are smaller than 17Ga. For example, an 18Ga epidural needle has an approximate internal diameter of 0.84mm; with an equivalent cross-sectional area of less than 0.55mm ² and additionally, the electrodes must have an approximate separation of twice their diameter in order to establish the impedance of the tissue in the presence of contaminating sources of the measurement. To improve the measurement of the impedance of the medium of interest, another embodiment of the present invention uses the metal axis of the epidural needle, connected to the electrical means, as a third electrode 631, as a reference electrode (see Figures 5 and 6 ). In this way, the bevel 204 at the tip of the needle, forms an electrode of elliptical geometry which surrounds the array of electrodes, and given its proximity to it, receives the majority of the current flow injected by the active electrode of the current source, which for this embodiment is defined as electrode 622. Similarly, for the present embodiment, the voltage measurement between electrode 621 and the electrode formed by bevel 204 is defined.

Another preferred embodiment for the arrangement of electrodes in the present invention is shown in Figure 7 wherein four electrodes 622,623, 624, and 625, are aligned with the longitudinal axis 618 of the needle, using the same inventive concepts described above to remove contaminants. on the electrodes (both tissue detritus and liquid films). In this embodiment, the four electrode configuration is used for impedance measurement, well known in the state of the art, where electrodes 622 and 625 are used as input and output of the stimulus current and between electrodes 623 and 624 the voltage is measured. In other possible embodiments of the present invention, Steendijk, P .; ur, Gerrit; van der Velde, ET; Baan, Jan "The four-electrode resistivity technique in anisotropic media: theoretical analysis and application on myocardial tissue in vivo", Biomedical Engineering, IEEE Transactions on, On page (s): 1138 - 148 Volume: 40, Issue: 11, Nov 1993 The metallic axis of the needle can be connected or not, to make it work as an electrical ground of the system or leave it unconnected.

Claims

1. A medical device for detecting body cavities, with electronic means to measure the bioimpedance of the tissue in contact with the tip of penetrating means, by means of electrodes that are inserted in a removable way, by means of a stylus, in a hollow portion of said penetrating means; Inside the stylet there are conductive means that connect the electrodes with said electronic means, which in turn produce a signal indicating the detection of the body cavity, wherein said device comprises:

- An arrangement of non-coplanar electrodes each embedded in a different plane or facet, where the surface of each facet is formed with a rigid substrate, which is an electrical insulator, which embeds the electrode, and exposes only the electrode region for contact with the biological tissue, so that the substrate forms a surrounding area from the electrode to the edges of the facet that contains it, the plane formed by the surface of each facet is not co-planar with the planes formed by the surfaces of the other facets of the arrangement; and the planes formed by the surfaces of adjacent facets with common edge, have an angle, measured in the normal plane (625) to said common edge, greater than 180 °, where said faceted arrangement (612) of non-coplanar electrodes reduces the creation of short circuits between electrodes due to the formation of conductive films of body fluids.

2. A device according to claim 1, wherein the stylet (602) has fins for centering (611) at least the distal end, an intermediate point and the proximal end of the portion that travels the hollow shaft (202) of the penetrating means, whereby the stylet is concentrically embedded in said penetrating means without touching its internal surface except for the points where the centering fins rest, the transverse area (651) of the stylet being smaller than the transverse area (652) of the hollow section of said penetrating means, thereby allowing the flow of gas or some liquid through the hollow corridor (653) thus formed.

3. A device according to claim 1 or 2 wherein its base (610) has a port (607) for hermetic coupling with a syringe, and which through ducts (608) creates continuity of flow with said syringe through a concentrator (610) that is tightly inserted into the connector of the penetrating means.

4. A device according to claim 1 wherein the electrode array has only two electrodes (621, 622), which are aligned with the longitudinal axis (618) of the penetrating means, wherein:

- such alignment defines a longitudinal axis for the sensor, which divides it into two portions of symmetrical faceted layer (620) on each side of the electrode array, - the substrate between the distal electrode (621) and the tip of the stylet, has two symmetric facets (620a, 620e) whose adjacent edge is aligned with the longitudinal axis of the sensor, said common edge approaches the axis (618) as it approaches the tip of the stylet where said symmetrical arrangement of the substrate around the alignment of electrodes and at the tip, it separates the body tissue by removing tissue debris that accumulates - on the electrode array during insertion of the penetrating media with the stylet.

5. A device according to any one of claims 1, 2, 3 and 4, wherein the proximal portion of the stylet (602) has at least one electrode (631) that makes electrical contact with the hollow metal shaft (202) of the penetrating means, so that the bevel (204) at the tip becomes an elliptical electrode surrounding the array of electrodes (620).

6. A device according to claim 5 wherein a syringe is connected with air or liquid and whose stylet is inserted into an epidural needle as a penetrating medium, for insertion into the body tissue, and to jointly perform the technique of loss of resistance to epidural space location simultaneously with the device's bioimpedance based detection.

MGM \ MG \! D-270912 \ WPC21370