CA2198000C - A device to stop bleeding in living human and animal tissue - Google Patents
A device to stop bleeding in living human and animal tissue Download PDFInfo
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- CA2198000C CA2198000C CA002198000A CA2198000A CA2198000C CA 2198000 C CA2198000 C CA 2198000C CA 002198000 A CA002198000 A CA 002198000A CA 2198000 A CA2198000 A CA 2198000A CA 2198000 C CA2198000 C CA 2198000C
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
- A61B18/04—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating
- A61B18/042—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating using additional gas becoming plasma
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
- A61B18/04—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating
- A61B18/12—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating by passing a current through the tissue to be heated, e.g. high-frequency current
- A61B18/1206—Generators therefor
- A61B2018/1213—Generators therefor creating an arc
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Abstract
The invention concerns a device to improve the coagulation of moderately or heavily bleeding live human and animal tissue and to form an eschar by means of a plasma jet. The device comprises plasma- generating means consisting of an electrically conductive body (6) which is connected to a positive pole of a basic energy source having a positive potential. The body (6) is formed with a cylindrical channel (17) designed to heat the plasma-generating gas. The channel (17) is formed from a number of sections (8, 9, 10) which are electrically insulated from each other and each one of which is connected to the body (6) via bushes (22). The bushes are concentric with the sections (8, 9, 10) and are electrically insulating. The bushes (22) are formed with channels (19) arranged to conduct cooling liquid to and from the gas-heating channel (17).
Description
t'19~D0~
A DEVICE TO STOP BLEEDING IN LIVING F-IUMAN AND ANIMAL
TISSUE
The subject invention concerns a device to stop bleeding in live human and animal tissue and to form a crust by means of a plasma jet. The invention relates to plasma surgery and more particularly to a new and improved plasma surgical technique of achieving coagulation or a hemostatic effect, i.e. desiccation and coagulation by weak supply of plasma jet power to a layer of tissue and intense supply of jet power to the fluid component of the biological tissue.
The purpose of the invention resides in plasma dynamic desic-cation of a surgical site and in the creation in said site of an area of 1 () thermal necrosis at a rate highly exceeding the rate of medium or in-tense bleeding with the aid of direct application of a plasma jet having definite thermo-dynamic characteristics.
Plasma flow, laser irradiation and electrosurgery are methods used in surgery far clean-cutting purposes, for combined cutting and hemastasis effect as well as for obtaining hemostasis of a surgical wound.
The dominant reactions induced by intense energy application on tissue are thermochemical in nature as a result of the energy absorption by the biological object. The major part of the energy is converted into heat.
The thermal effect of the application of an intense flow of energy explains the character of the biological processes developing in tissue during and after the application.
An analysis of the biological and hemostatfc effect of a cancen-r 5 trated plasma flow and irradiation an tissue has shown that an area of thermal changes (ATC) is farmed therein which comprises several zones. As a result of intense power supply the surface of the tissue is desiccated and a span~~ desiccated necrosis layer is formed on the tissue surface. The surface of the spon~v layer is carbonized - Carbon-ized Spongy Layer (CSL). Due to a conduction mode of heat transfer a compact necrosis layer (CNL) is formed. This layer farms between the spongy layer and the unaffected living tissue. The generation of a com-pact necrosi~~ layer is a result of the therTnal denaturation of protein occurring as temperatures rise above 56°C.
From a. medical-biological point of view the elimination of bleeding is obtained by creating an ATC and the level of hemos;tasis reliability depends on the size of the ATC and the time of its creation.
In particular, the prior utilization of different methods of application (laser irradial:ion, plasma jet and electrosurgery) shows that positive hemostasis and lack of hazards during the healing process occur when the average thickness of the ATC is about 1.0 mm.
In the development ~~ork of the subject invention the character-istics of different layers in the area of thermal changes occurring when using conventional methods v~~ere carefully investigated.
Taking into consideration the bleeding rate when different ne-crosis layers were created in the area of thermal changes, fundamen-tal disadvantages were found with respect to the various methods of thermal applications. Consequently, a need was felt for developing new methods for the purpose of achieving a high degree of efficier.~cJ~
in surgery on highly bleeding organs. Various such methods for c:rea-2 0 ting characteristic of various zones of ATC will be discussed in the following.
While working on the prior .technique emphasis has primarily been placed on the bleeding rate as a decisive factor when applying the method on high-rate bleeding organs. When the blood flow :in tissue is heav'T and the bleeding from a surgical incision is high, it is necessary to create an ATC ensuring that the vaporization rate of the liquid component is higher than the flow rate of the blood moving towards the incision. This means that the thermal energy developing inside the volume unit of the tissue as a result of the outer application must exceed the amount of power expended on vaporization of 'the' volume unit of the blood flowing towards the incision.
To creat<: a spongy desiccation layer on the surface of the tissue it is necessary to separate in space the boundary of sublimation of this layer from the boundary of vaporization of the liquid component.
5 in this case it is moved towards the place of application at the ~>pe:ed of the blood flow r ate, preventing the creation of a spongy necrosis 1 ave r.
WAD 96106172 PCTlSE94100790 Depending on the technique of energy supplied to the tissue different methods of application are available, among them methods of delivery of ener~~ supply to the surface of a tissue where the tissue is heated and the creation of zones of necrosis in the ATC occurs at the expense of thermal conductivity. A method utilizing a COz-laser and a plasma. jet. belongs to this category. In order to obtain desiccation and create a spongy desiccation layer heat is in this case conducted to the boundar~% of vaporization of the liquid component by means of thermal conductivity. Because during the desiccation of tissue its thermal conductivity is reduced by 4-6 times compared ~~ith undesiccated tissue and by 0.62 W/m . °C, the rate of the displacement of the va-porization boundary with respect to the liquid component diminishes as well, which means that the rate of the ATC creation goes down considerably.
1!.p The use of this method allows the spongy necrosis layer to be obtained only during weak and rather moderate bleeding. This may be understood by the following example. In order to desiccate a layer of tissue during intense heating when an opposing blood tlotv is mov-ing at a rate of 2 mm/s, the thermal flow at the boundary of vaporization 2C of the liquid component in the tissue must exceed 4.6 x 106 Vv/m~.
However, when the thickness of the desiccation layer is close to 0.25 mm the quantity of thermal flow at the boundary of Liquid vaporiza-tion of the liquid component does not exceed 4 x 105 W/m~.
This is due to the fact that the temperature of sublimation of 25 the desiccated and charged surface is about 700°C and the tempera-ture of vaporization of the liquid component is about 100°C. This ex-plains the difficulties of reducing and eliminating intense bleeding by using methods involving energy supply= to a tissue surface. In particu-lar, a plasma jet flowing along the tissue surface is not able to elimi-30 note intense bleeding.
In accordance with another method energy is supplied t.o a tissue and allow to penetrate into it. In accordance with these methods a YAG (Nd-YAG) laser beam in the visible and the near-infra-red region is used as well as electrosurgical application. In the first 3 S case, the energVV is absorbed into the tissue to a depth of 1.0 mm. To achieve efficient desiccation of the tissue surface during the applica-tion of the laser beam the amount of thermal ener~> penetrating into the unit volume of tissue must slightly exceed the energy required to vaporize the blood flow in the tissue and the application must be terminated at the moment of achieving desiccation. This is essential in order to eliminate areas of heavy sublimation of the tissue surface, which would otherwise have led to destruction of the newly-construct-ed necrosis layer, as the desiccated layer have a much higher coeffeci-ent of laser energy absorbtion than non-desiccated tissue. Intense sublimation of the desiccated layer results if the application is conti-nued after the formation of a spongy layer. This feature is one of the most essential drav~~backs connected ~~ith the use of laser radiation within the visible and near-infrared regions in order to eliminate me-dium and h~°avy bleeding.
In the second case the energy supply to the tissue is effected by application of high-frequency current to the tissue. As soon as desic-ration is achieved, its impedence increases considerably, resulting in termination of the application and the achievement of a desiccated layer.
The most efficient method of eliminating heavy bleeding is to make use of the electrosurgical technique in order to obtain coagula-2 0 tion, which is described in the US Patent Specification 4 781 U 7;i.
This publical:ion concerns conducting a predetermined ionizable gas in the form of a jet to the tissue as the predetermined flow rate that is sufficient to <~lear the tissue of natural fluids and to expose the con-nective tissue. (stroma) to an essential degree. Electric radio frequency 2 5 energy is conducted to the tissue in ionized conductive pathways in the gas jet. To achieve fulguration, the electrical energy is conducted in the form oil arcs in ionized conductive pathways. To achieve a :non-contact type of electrosurgical desiccation, the electric energy is con-ducted as a non-arcing diffused current in the ionized conductive' 3 0 pathv~~ays.
The conduction of energy into the bulk of the tissue is pointed out to be on~° of the advantages of the described method, providing a rapid build-up of a desiccation layer on the surface of intense-bleeding surgical incisions.
35 The use of a laminar jet of an inert gas in order to remove 1:>lood from the surgical site and also for substantially uniform distribution of electric power ~;-ithin the tissue makes it possible to create thermal-ly desiccated layers having a uniform depth compared with prior art electrosurgical techniques.
In addition, this method involves feedback during the application because the energy supply stops at the moment of tissue surface 5 desiccation, i.e. after the final creation of the spongy necrosis layer.
This diminishes the generally harmful effect of the method and provides an opportunity to choose determined regimes with guaranteed power amounts and hence with guaranteed achievement of arresting intensive bleeding.
The main disadvantages of electrosurgical application on biological tissue are the following. In order to stop intensive bleeding it is necessary to increase the amount of enemy of the application, which is carried out at the expense of the regime of the microarc generation between the tissue and the surgical instrument. The emission of energy in biological tissue involves passing current through a patient, which may limit its usage (for instance in the case of heart diseases). This method does not allow precise incision to be made in tissue in contrast to the characteristics of the laser beam method.
Traditional plasma methods are characterized by a supply of thermal energy to a tissue surface by means of a plasma flow, which makes it rather difficult to use it in connection with medium and intensive bleeding. The disadvantages of plasma application may be eliminated only by heat exchange between the plasma flow and the biological tissue.
The invention provides a device to stop bleeding in live human and animal tissue and to form an escarre by means of a plasma jet, - the device comprising means for the generation of plasma, comprising an electrically conductive body and a gas power source, said electrically conductive body having the appearance of a pencil and being formed with a tip for forming the required cross-section of the plasma jet, said body being connected to a positive pole of said gas power source having a positive potential, - the body comprising a cylindrical channel for heating a plasma-generating gas which channel is formed from a number of sections, each one of which is connected to the body via electrically insulated bushes which are concentric with the sections, characterised in that the number of sections are longitudinally separated and are electrically insulated from each other ;end the electrically insulated bushes are formed with channels designf:d to conduct cooling liquid to and from the gas-heating channel, and in that said sections have a channel length ln, n being the number of sections calculated from a cathode, the total number of said sections being at least three, said sections, except the outermost one, having an equal channel diameter d~, and the length of each subsequent section, separated from the cathode, being In = n . d~.
The invention will be described in closer detail with reference to the accompanying drawings wherein Fig. 1 is a cross-sectional view through a wound in tissue that has been treated by rneans of the device in accordance with the invention, Fig. 2 is a corresponding cross-sectional view through tissue treated by mean; of an electrosurgical method, Figs. 3a and b are corresponding sectional views schematically illustrating the inter-active flows to and away from a tissue, Figs. ~l and 5 show coordinate systems with curves represen-ting measured values of thermal energy as a function of plasma jet temperature , Fig. 6 is longitudinal sectional view through a plasma nozzle in accordance with one embodiment of the invention wherein an inert gas is used, Fig. 6a is a cross-sectional view along line A-A in Fig. 6, Figs. 7 and ?a are corresponding sectional views but show a different embodiment of the plasma nozzle wherein the used gas is air and Figs. 8 and 8a are corresponding sectional views of a third em-bodiment of the plasma nozzle using water vapor.
Fig. 1 is sectional view through a treated wound in a tissue.
l~umeral reference 1 designates a spongy desiccated layer showing locally dead cells (necrosis). This layer 1 is covered by a carbonized layer 2. Owing to heat transfer a compact necrosis layer 3 has formed underneath the spongy desiccated layer 1. The necrosis layer is for-med between the spongy layer 1 and the unaffected, live tissue 4.
Fig. 2 shows a wound treated with the aid of electrosurgical technique. In this case the spongy layer 1 is characterized by an ex-ternal, essentially uniform-depth supporting tissue (reticulum) having holes 5 created by means of a light arc. The holes are essentially of identical cross-sectional area and are essentially evenly distributed across the esc:har surface. The tissue intermediate adjacent holes 5 confers pliability to the eschar, preventing cracking. And generally uniform-depth thermally desiccated layer 3 separates the arc hole re-ticulum from the unaffected tissue.
The high porosity of the necrosis layer (as will be shown below it amounts to approximately the percentage of fluid component in the tissue -75-85°~0) makes it possible to use the essentially novel method of plasma flow to obtain this layer under extensive bleeding condi-dons.
As mentioned above the difficulties of arresting intense bleeding are related to the need for separating in space the external boundary of tissue surface sublimation and for presenting in the depth of thf:
tissue the boundary of fluidcomponent vaporization. The latter boun-dary moves with blood flow rates towards the application and pre-vents theformation of a spongy necrosis layer, in particular in the ca-se of intensf~ bleeding.
The presence of various forms of energy resources is typical of plasma jet. 'rhe plasma flow energy is concentrated as a form of plas-ma enthalpi, a dynamic component of jet energy and broadband~
emission of :ionized gas. By changing the consumption of the plasma-generating gas, the cross-sectional area of the plasma jet and its tem-perature it becomes possible to control the dynamic pressure of the plasma flow. Consequently, it becomes possible to establish inte:r-action between the plasma jet and the spongy necrosis layer when the plasma jet penetrates this layer completely or partly. As a result, the plasma jet is partly cooled while heating the spongy necrosis layer and the remaining part of the jet energy is absorbed at the boundary of the vaporization of the tissue fluid component. The filtration of the cooled plasma-generating gas and of the vapour flow takes place throul;h the low pressure area of the plasma jet. The above-described modes of interactions het~~een the plasma jet and the tissue surface are s:hovsrn schematically in Fig. 3a and 3b.
This analysis points out a new principal possibility of conduc-t 0 ting energy to tissues by making use of a plasma-dynamic effect of an ionized gas flow. The high porosity of the spongy necrosis layer estab-lished by predetermined thermo-physical and gasodynamical parame-ters in the plasma flow results in gasodynamical and thermal penet-ration by the plasma jet in this layer 3b. In this case it becomes pos-sible to realise combined properties in the conduction of energy to tissue - volume power delivery to the spongy necrosis layer anal su-perficial heating of the fluid component of the tissue within the spongy layer.
The investigation of the porosity of the spongy layer has indica-ted that the cross-section of pores d and the porosity P with respect to typical parenc:hy-matous organs are: lungs d = 0.06-0.09 mm, P == 0.9-0.95, spleen d = 0.04-0.07 mm, P = 0.85-0.9, liver d = 0.035-0.06 mm, P = 0.75-0.8, kidney d = 0.02-0.04 mm, P = 0.65-0.7. As a result, the maximum. cross-section of a plasma jet that realizes penetration of plasma flow in the spongy necrosis layer to a depth of about 0.25 mm equals 3.5 mrn in lungs, 3.0 mm in the spleen, 2.5 mm in the liver and 1.5 mm in kidneys.
21 ~?~~J ~0 w0 96tt16i72 PGTISE9d100190 These data are applicable to an argon plasma jet. The use of lighter gases (neon, air and helium) leads to a reduction of the toler-able jet cross-section.
In order to establish the influence of plasma-generating gas pa-s rameters on the efficiency of arresting intensive bleeding investiga-tions have been carried out on arrests of bleeding in experimental subjects (53 dogs in more than S00 experiments). The dogs wore anesthezed and regional resections wore carried out. The area, of the wound surfaco was within 3-i4 cma. Before the coagulation of the 7.0 wound surface started the value of wound bleeding ~%as measured at a fixed time as also the wound area and from tho results it becamo possible to calculate tho mean flow-rate of blood from the wound and to define the intensity of the bleeding.
The mean bloeding rate from a liver wound lay within the aroa 1~~ of 0.6-1.8 mm/s, from a spleen wound 0.$-2.5 mm,/s. It should be pointed out that intensive bleeding corresponds to an average bleeding rata iif U > 1.0 mm/ s.
In accordanco therewith various sources of action worn compa-red with each other, possessing bieoding rates of 1.5-2.0 mm/ s. In the 20 investigations using microplasmatrons working on hokum, noon, ar-gon, nitrogon tend air, the plasma flow parameters could be changed u~ithin a wide range since these microplasmatrons were produced wit-hout taking into consideration some limitations required for the surgi-cal plasma generators, in particular the follo~xring: small dimensions, '~?:: convenience of manipulation and handling, stability and reliability, major overhauls, minimum content of erosion products an the elect-rodes, limited gas consumption to exclude of gaseous embolism and some other limitations.
The results of those investigations are shown in Figs. 4 and 5.
3D The black dots correspond to the values of the thermal power and plasma jet temperatures that provide reliable arrest of intensive bleeding. Lines I, II, III iilustrato the paramoters of the plasma jet bo-undaries beyond which it was not possible to stop bleeding.
When helium was used it eras possible to achieve reliable arrest ~5 of bleeding only at a bleeding rate of U < 1.0 mm/s.
Theso findings give evidence of a principal effect of the plasma-generating gas and of the thermo-physical properties of plasma. Parti-z~sc~~~c R'n 96!06572 PC1'ISE94l0079t1 cularly helium plasma fails to provide arrest of intensive bleeding in practically every range. By using argon, neon and air it becomes pos-sible to stop intensive bleeding but their use involves limitations of the thermo-physical parameters of the plasma flotv, of the extent of t~ consumption of the plasma-generating gas and of the plasma jet cross-sectional area.
To analyze the particularities of these limitations a numerical model of interaction between plasma flow and live tissue has been de-veloped. This model comprises:
1G - percentage of fluid component in the tissue - bleeding rate from wound - volume density of blood flow in the tissue - distinction of the thermo-physical characteristics of the tissue upon phase-structural changes and the formation of ATC
15 - distinction between temperatures of vaporization of the liquid com-ponent of the tissue and of the sublimation of the charring spongy layer gasodvnamics of plasma jet flow and vapour flow in the spongy ne-crosis layer.
20 The analysis of experimental data a.nd the realization of a nu-meric model show that the existence of limitations with respect to the plasma flow parameters that reliably arrest intensive bleeding is de-termined by the following principal characteristics of interaction bet-ween the plasma jet and the live tissue.
25 1. Boundary line I defnes the condition of gasodynamic penet-ration of the plasma flow into a porous dessicated tissue layer, to a depth of 0.2-0.25 mm, i.e. exceeding by 3-5 times the a characteristic cross-section of the pares d. The position of the boundary 1 is deter-mined by tissue species and depends on the cross-sectional area of 30 the plasma jet.
2. Boundary line II defines the condition of vaporization of the liquid component of the tissue at a rate exceeding the rate of bleeding.
The position of baundary II is determined by the extent of cooling of the plasma jet in the bulk of the spongy necrosis layer and is defined 35 by the parameter ~~r . P
Cpr . Icr . d i.e. the type of the plasma generating gas.
An analysis of the investigation of the heat transfer process in the po-rous systems in which gas flows shows that the intensity of the heat transfer in the pores is determined by 5 ~.f < 2.0 CPf . wf This in turn explains the dependence of the creation of a spongy des-sicated layer on the thermo-physical characteristics of the plasma flow obtained during experiment.
10 3. Boundary line III defines the condition of intensive sublima-tion of a carlr~onized spongy layer when the boundary of tissue subli-mation coincides with the boundary of the fluid component. Besides the limitations mentioned it is necessary to also take into account that the very considerable volume increase of the plasma-generating gas consumption may be the cause of the generation of gaseous em-bolism. Investigations show that in order to exclude gaseous embo-lism appearance the value of argo n and air consumption must not exceed 2.0 1/min. To increase the temperature of the argon plasma jet to a value above 10 500° K it is necessary to increase the discharge 2 0 current rate to more than 30A, which leads to the appearance of in-tensive erosion of the electrodes and to the occurrence of erosion pro-ducts in the field of operation. Considering these factors the par~~ne-ters most suitable for arresting intensive bleeding by means of a plasma jet are those falling within the marked areas.
2 5 The results from the investigation prove that the arrest of in-tensive bleeding as a result of plasma application takes place within a limited area of therTno-physical characteristics and of ~gasodynarmic parameters of the plasma jet. In addition, it does not provide a reliable arrest of inten;~ive bleeding when plasma-generating gases are used 3 0 that have high heat conduction, low heating capacity and low viscosi-ty.
The gas ~~roviding the widest range of change of the plasma. pa-rameters and able to arrest heavy bleeding is argon. The use of air as the plasma generating gas could also make it possible to stop intensi-3 5 ve bleeding but: within a much narrower range of plasma parameters compared with argon. It should be noted that in order to generate plasma flows having the above-mentioned parameters some limit;a-W0 961itG572 PCTJSE94J00790 dons of the plasma surgical instrument must be respected. In particu-lar, surgical microplasmatrons must generate plasma flows having an average mass temperature valid for the given type of gas (argon ar air) of a necessarily comparatively high value (argon 7500 - 10 500° K, air 4500 - 5000° K) and that must change only insignificantly during fluctuations of consumption of the plasma-generating gas (between the limits 1.0-2.0 1/min). Furthermore, the above parameters of plas-ma flow must be achieved ~~ith limitation of the value of the discharge current at a level near 30 A, excluding erosion of the electrodes of the microplasmatron.
In order to obtain a guaranteed hemostatic effect in the wound surface during a significant change of the bleeding intensity it is ne-cessary that the plasma-surgical instrument generates a plasma jet at a stable and comparatively- high level of its temperature. The jet tem-i 5 perature must not change significantly during the regulation of the consumption of the plasma-generating gas. To attain high-level plas-ma flow temperature it is necessary to diminish the cross-section size of the electric arc that heats the gas. This means that the chamber channel for heating the plasma.-generating gas by means of an electric arc must have a reduced cross-sectional size.
Proceeding from the required level of gas consumption (1.0-2.0 I/min) and taking into consideration the elimination of its thermal choking during heating the minimum cross-sectional area of the chamber channel for heating the plasma-generating gas must be O.S
2 5 mm and according to the investigation the optimal size thereof falls within the range of 0.7-1.0 mm in the case of air and 1.0-1.5 mm in the case of argon.
This crass-section of the electrical arc results in a high value of the electrical field strength in the channel and the length of the chan-nel that is necessary to heat the argon at the consumption rate of 2.0 1/min is insufficient to provide the electric discharge-distance strength. In this case a voltage drop in the plasma of the electric arc increases above 15-16 V (total value of voltage step input) and in con-sequence thereof instead of one long arc two sequential arcs appear, burning at a loner voltage and not providing gas heating to a high temperature.
To exclude electric breakdowns in the channel designated to heat the plasma-generating gas this channel is designed as electrically isolated sections. Its number must not be less than three: The highest electrical field strength is generated by the initial field of the electric arc at the cathode where a cooled gas enters into the arc. The length of the channel sections must be increased at a distance from the cathode since the field strength decreases. The most suitable channel geometry is to design it with a length of its first section at the cathode equalling its cross-sectional diameter (1~ = d~) with the length of each subsequent section being In = n . d~ where n represents the number of sections. The sections are interconnected via non-electr~ic-ally conductive gaskets. The first channel section is connected to the positive pole of a pulse periodic energy accumulator and to a high-voltage sparl~: gap (triggering system of a surgical microplasmatron).
The la~;t section is connected to the positive pole of a main power source in the surgical microplasmatron. A suitable length of this section i:~ two to three times the diameter of channel d. All chan-nel sections with the exception of the last one have the same cro;ss-sectional dimensions. The last section should, for the purpose of dis-secting tissues in optiriZal modes of operations, have a channeY width of 0.4-0.6 mm. Its design when employed for this purpose does not depend on thc~ kind of plasma-generating gas used.
When a microplasmatron is used to stop bleeding from a wound surface the cross-sectional size of the last channel section does, 2 5 however, depend on both tissue species and type of plasma-generating ga~~.
When argon gas is used to stop bleeding from surgical incisions on the lungs, the spleen and the liver the cross-sectional dimensions of the last channel sections should be 2.5 mm and in the case ~of kid-3 0 neys 1.5 mm.
In Fig. 7 a basic embodiment of a plasma surgical unit is shown, consisting of an electrically conductive body 6 similar to a pencil with a tip 7 for forming a plasma jet having the required cross-section and connected to a positive pole of a gas power source having 35 a positive potential. The body 6 comprises a cylindrical channel for heating the plasma-generating gas and it is formed from channel sec-tions 8, 9, 10 which are electrically isolated from each other and which are connecaed to the body 6 through an electrically isolated concentric bush 11 having channels 12 for conveyance of cooling fl,uicL to and from the gas heat-ing channel. The sections 8, 9, 10 are interconnected b;~ means of non-electrically conductive sleeves 22.
Sections 8, 9 and 10 each have a channel length ln, n being the number of sections as calculated from the cathode 13 and as illustrate°d as 11, 12 and is re~;peetively in Figure 7.
Sections 8 and 9 have an equal diameter d~. The last section 10, which is designed to form the plasma jet, is connected with the tip '7 and constructed as two co-axial cylindrical holes 17, 18 having an entrance diameter identical to the diameter of all preceding sections d~ and a.n exit hole 18 having th a diameter df = 0.4-0.6 mm and the length 1 = ( 1.5-2 .0) . dr. The channel cross-section dr at the exit hole 18 stops bleedings from large surgical wounds. The channel cross-section depends on the kind of plasma-generating gas and the species of the biological tissue.
The total nvumber of sections 8, 9 and 10 must not be less than three and the length of each subsequent section separated from the cathode must be In = n . d~.
The first section 8 is configured as a hollow cylindrical electrode which is connected with the body 6 via the electrically isolated bush 1 1 and with the cathode 13, 14 via the electrically isolated sealing bush 15.
The seconds are mutually interconnected via the non-electrically conductive sleeves 22.
The cathode consists of an electrically conductive tube 14 on one end of which the electrode 13 from a high-melting metal is fixed, providing the required level of current for thermal-electronic emission within the working range of discharged currents. The opposite end of the tube serves as a connection to the gas supply unit and is connect.°d with the negative poles of the basic energy source and of the trigger system of the mirroplasmatron. The electrically conductive tube 14 is formed with holes 16 for input and uniform distribution of the plasma-generating gas to the discharge chamber of the microplasmatron.
In order to work with inert plasma-generating gases (argon, crypton, xenon) the electrode of the cathode 13 is made from wolfram or its alloys (Fig. 6). In order to use air or steam as the plasma-generati:r~g gas the electrode of the cathode 13 is made from zirconium or hafnium (Figs. 7, 8).
When steam is used as the plasma-generating gas the second last and the last sections 9 and 10, respectively, are formed at t:he beginning and the end, respectively, with tangentially positioned channels 1~~ (see Fig. Band 8a ~~hich are connected to the channel heating the plasma-generating gas and having the volume separated from the cooling water by means of inserts 20 formed with pores positioned in-side a heat insulated cylindrical sleeve 21. The porous inserts 2(J
cover at lea:;t half of the external surface of the second last and the last sections. 9 and 10. The water-filled cavity is connected to a system regulating tl~ie water pressure in order to control the quantity of steam consumption. The discharge current provides the required tempera-ture of the p:(asma flows and the size of the steam consumption :is between 3.0 and 8.0 A.
It should be obvious that the eschar resulting from the use of the device proposed in accordance v~rith the subject invention :has a well defined spongy necrosis layer having a thickness of 0.15-0.25 mm, which corresponds to between 3 and 5 characteristic cross-2 0 sections of pores therein.
The porous layer in accordance with the invention has a well defined boundary to~~ards the subjacent tissue, which indicates the highly restricted heat penetration into the tissue and the localisation in this area of the boundary of vaporization of the liquid component of the tissue.
A comparison of the thickness of the spongy necrosis layer (SNL) resulting from the exposure to plasma and laser~on liver and spleen wounds with intensive bleeding shows that in the first case the SNL has a thi~~kness which is between 3 and 5 times larger than in the second case.
The pore size upon plasma exposure is 1.5 times less that upon laser exposure and the thickness of tissue intermediate the pores is 1.3 times large°r. This indicates that the permiability of a spongy des-sicated layer i;5 approximately similar to that of a dessicated tissue obtained by means of methods involving slow heating at a tempera-ture which only slightly exceeds that of vaporization of the tissue liq-uid component of the tissue.
1;~~U~~
WO 9b106572 PCTISE9dIp0790 These investigations of the reparative processes in the tissue of liver, lungs and kidneys have shown that the healing after the expo-sure to argon, neon and helium plasma flows takes place in the can-ventianal way and is not dependent on the type of gas used. The 5 healing of organs takes place without deformation of rough scars therein.
The device in accordance with the invention is not limited to the features shaven and described but could be varied in several ways within the scope of the appended claims.
~. o
A DEVICE TO STOP BLEEDING IN LIVING F-IUMAN AND ANIMAL
TISSUE
The subject invention concerns a device to stop bleeding in live human and animal tissue and to form a crust by means of a plasma jet. The invention relates to plasma surgery and more particularly to a new and improved plasma surgical technique of achieving coagulation or a hemostatic effect, i.e. desiccation and coagulation by weak supply of plasma jet power to a layer of tissue and intense supply of jet power to the fluid component of the biological tissue.
The purpose of the invention resides in plasma dynamic desic-cation of a surgical site and in the creation in said site of an area of 1 () thermal necrosis at a rate highly exceeding the rate of medium or in-tense bleeding with the aid of direct application of a plasma jet having definite thermo-dynamic characteristics.
Plasma flow, laser irradiation and electrosurgery are methods used in surgery far clean-cutting purposes, for combined cutting and hemastasis effect as well as for obtaining hemostasis of a surgical wound.
The dominant reactions induced by intense energy application on tissue are thermochemical in nature as a result of the energy absorption by the biological object. The major part of the energy is converted into heat.
The thermal effect of the application of an intense flow of energy explains the character of the biological processes developing in tissue during and after the application.
An analysis of the biological and hemostatfc effect of a cancen-r 5 trated plasma flow and irradiation an tissue has shown that an area of thermal changes (ATC) is farmed therein which comprises several zones. As a result of intense power supply the surface of the tissue is desiccated and a span~~ desiccated necrosis layer is formed on the tissue surface. The surface of the spon~v layer is carbonized - Carbon-ized Spongy Layer (CSL). Due to a conduction mode of heat transfer a compact necrosis layer (CNL) is formed. This layer farms between the spongy layer and the unaffected living tissue. The generation of a com-pact necrosi~~ layer is a result of the therTnal denaturation of protein occurring as temperatures rise above 56°C.
From a. medical-biological point of view the elimination of bleeding is obtained by creating an ATC and the level of hemos;tasis reliability depends on the size of the ATC and the time of its creation.
In particular, the prior utilization of different methods of application (laser irradial:ion, plasma jet and electrosurgery) shows that positive hemostasis and lack of hazards during the healing process occur when the average thickness of the ATC is about 1.0 mm.
In the development ~~ork of the subject invention the character-istics of different layers in the area of thermal changes occurring when using conventional methods v~~ere carefully investigated.
Taking into consideration the bleeding rate when different ne-crosis layers were created in the area of thermal changes, fundamen-tal disadvantages were found with respect to the various methods of thermal applications. Consequently, a need was felt for developing new methods for the purpose of achieving a high degree of efficier.~cJ~
in surgery on highly bleeding organs. Various such methods for c:rea-2 0 ting characteristic of various zones of ATC will be discussed in the following.
While working on the prior .technique emphasis has primarily been placed on the bleeding rate as a decisive factor when applying the method on high-rate bleeding organs. When the blood flow :in tissue is heav'T and the bleeding from a surgical incision is high, it is necessary to create an ATC ensuring that the vaporization rate of the liquid component is higher than the flow rate of the blood moving towards the incision. This means that the thermal energy developing inside the volume unit of the tissue as a result of the outer application must exceed the amount of power expended on vaporization of 'the' volume unit of the blood flowing towards the incision.
To creat<: a spongy desiccation layer on the surface of the tissue it is necessary to separate in space the boundary of sublimation of this layer from the boundary of vaporization of the liquid component.
5 in this case it is moved towards the place of application at the ~>pe:ed of the blood flow r ate, preventing the creation of a spongy necrosis 1 ave r.
WAD 96106172 PCTlSE94100790 Depending on the technique of energy supplied to the tissue different methods of application are available, among them methods of delivery of ener~~ supply to the surface of a tissue where the tissue is heated and the creation of zones of necrosis in the ATC occurs at the expense of thermal conductivity. A method utilizing a COz-laser and a plasma. jet. belongs to this category. In order to obtain desiccation and create a spongy desiccation layer heat is in this case conducted to the boundar~% of vaporization of the liquid component by means of thermal conductivity. Because during the desiccation of tissue its thermal conductivity is reduced by 4-6 times compared ~~ith undesiccated tissue and by 0.62 W/m . °C, the rate of the displacement of the va-porization boundary with respect to the liquid component diminishes as well, which means that the rate of the ATC creation goes down considerably.
1!.p The use of this method allows the spongy necrosis layer to be obtained only during weak and rather moderate bleeding. This may be understood by the following example. In order to desiccate a layer of tissue during intense heating when an opposing blood tlotv is mov-ing at a rate of 2 mm/s, the thermal flow at the boundary of vaporization 2C of the liquid component in the tissue must exceed 4.6 x 106 Vv/m~.
However, when the thickness of the desiccation layer is close to 0.25 mm the quantity of thermal flow at the boundary of Liquid vaporiza-tion of the liquid component does not exceed 4 x 105 W/m~.
This is due to the fact that the temperature of sublimation of 25 the desiccated and charged surface is about 700°C and the tempera-ture of vaporization of the liquid component is about 100°C. This ex-plains the difficulties of reducing and eliminating intense bleeding by using methods involving energy supply= to a tissue surface. In particu-lar, a plasma jet flowing along the tissue surface is not able to elimi-30 note intense bleeding.
In accordance with another method energy is supplied t.o a tissue and allow to penetrate into it. In accordance with these methods a YAG (Nd-YAG) laser beam in the visible and the near-infra-red region is used as well as electrosurgical application. In the first 3 S case, the energVV is absorbed into the tissue to a depth of 1.0 mm. To achieve efficient desiccation of the tissue surface during the applica-tion of the laser beam the amount of thermal ener~> penetrating into the unit volume of tissue must slightly exceed the energy required to vaporize the blood flow in the tissue and the application must be terminated at the moment of achieving desiccation. This is essential in order to eliminate areas of heavy sublimation of the tissue surface, which would otherwise have led to destruction of the newly-construct-ed necrosis layer, as the desiccated layer have a much higher coeffeci-ent of laser energy absorbtion than non-desiccated tissue. Intense sublimation of the desiccated layer results if the application is conti-nued after the formation of a spongy layer. This feature is one of the most essential drav~~backs connected ~~ith the use of laser radiation within the visible and near-infrared regions in order to eliminate me-dium and h~°avy bleeding.
In the second case the energy supply to the tissue is effected by application of high-frequency current to the tissue. As soon as desic-ration is achieved, its impedence increases considerably, resulting in termination of the application and the achievement of a desiccated layer.
The most efficient method of eliminating heavy bleeding is to make use of the electrosurgical technique in order to obtain coagula-2 0 tion, which is described in the US Patent Specification 4 781 U 7;i.
This publical:ion concerns conducting a predetermined ionizable gas in the form of a jet to the tissue as the predetermined flow rate that is sufficient to <~lear the tissue of natural fluids and to expose the con-nective tissue. (stroma) to an essential degree. Electric radio frequency 2 5 energy is conducted to the tissue in ionized conductive pathways in the gas jet. To achieve fulguration, the electrical energy is conducted in the form oil arcs in ionized conductive pathways. To achieve a :non-contact type of electrosurgical desiccation, the electric energy is con-ducted as a non-arcing diffused current in the ionized conductive' 3 0 pathv~~ays.
The conduction of energy into the bulk of the tissue is pointed out to be on~° of the advantages of the described method, providing a rapid build-up of a desiccation layer on the surface of intense-bleeding surgical incisions.
35 The use of a laminar jet of an inert gas in order to remove 1:>lood from the surgical site and also for substantially uniform distribution of electric power ~;-ithin the tissue makes it possible to create thermal-ly desiccated layers having a uniform depth compared with prior art electrosurgical techniques.
In addition, this method involves feedback during the application because the energy supply stops at the moment of tissue surface 5 desiccation, i.e. after the final creation of the spongy necrosis layer.
This diminishes the generally harmful effect of the method and provides an opportunity to choose determined regimes with guaranteed power amounts and hence with guaranteed achievement of arresting intensive bleeding.
The main disadvantages of electrosurgical application on biological tissue are the following. In order to stop intensive bleeding it is necessary to increase the amount of enemy of the application, which is carried out at the expense of the regime of the microarc generation between the tissue and the surgical instrument. The emission of energy in biological tissue involves passing current through a patient, which may limit its usage (for instance in the case of heart diseases). This method does not allow precise incision to be made in tissue in contrast to the characteristics of the laser beam method.
Traditional plasma methods are characterized by a supply of thermal energy to a tissue surface by means of a plasma flow, which makes it rather difficult to use it in connection with medium and intensive bleeding. The disadvantages of plasma application may be eliminated only by heat exchange between the plasma flow and the biological tissue.
The invention provides a device to stop bleeding in live human and animal tissue and to form an escarre by means of a plasma jet, - the device comprising means for the generation of plasma, comprising an electrically conductive body and a gas power source, said electrically conductive body having the appearance of a pencil and being formed with a tip for forming the required cross-section of the plasma jet, said body being connected to a positive pole of said gas power source having a positive potential, - the body comprising a cylindrical channel for heating a plasma-generating gas which channel is formed from a number of sections, each one of which is connected to the body via electrically insulated bushes which are concentric with the sections, characterised in that the number of sections are longitudinally separated and are electrically insulated from each other ;end the electrically insulated bushes are formed with channels designf:d to conduct cooling liquid to and from the gas-heating channel, and in that said sections have a channel length ln, n being the number of sections calculated from a cathode, the total number of said sections being at least three, said sections, except the outermost one, having an equal channel diameter d~, and the length of each subsequent section, separated from the cathode, being In = n . d~.
The invention will be described in closer detail with reference to the accompanying drawings wherein Fig. 1 is a cross-sectional view through a wound in tissue that has been treated by rneans of the device in accordance with the invention, Fig. 2 is a corresponding cross-sectional view through tissue treated by mean; of an electrosurgical method, Figs. 3a and b are corresponding sectional views schematically illustrating the inter-active flows to and away from a tissue, Figs. ~l and 5 show coordinate systems with curves represen-ting measured values of thermal energy as a function of plasma jet temperature , Fig. 6 is longitudinal sectional view through a plasma nozzle in accordance with one embodiment of the invention wherein an inert gas is used, Fig. 6a is a cross-sectional view along line A-A in Fig. 6, Figs. 7 and ?a are corresponding sectional views but show a different embodiment of the plasma nozzle wherein the used gas is air and Figs. 8 and 8a are corresponding sectional views of a third em-bodiment of the plasma nozzle using water vapor.
Fig. 1 is sectional view through a treated wound in a tissue.
l~umeral reference 1 designates a spongy desiccated layer showing locally dead cells (necrosis). This layer 1 is covered by a carbonized layer 2. Owing to heat transfer a compact necrosis layer 3 has formed underneath the spongy desiccated layer 1. The necrosis layer is for-med between the spongy layer 1 and the unaffected, live tissue 4.
Fig. 2 shows a wound treated with the aid of electrosurgical technique. In this case the spongy layer 1 is characterized by an ex-ternal, essentially uniform-depth supporting tissue (reticulum) having holes 5 created by means of a light arc. The holes are essentially of identical cross-sectional area and are essentially evenly distributed across the esc:har surface. The tissue intermediate adjacent holes 5 confers pliability to the eschar, preventing cracking. And generally uniform-depth thermally desiccated layer 3 separates the arc hole re-ticulum from the unaffected tissue.
The high porosity of the necrosis layer (as will be shown below it amounts to approximately the percentage of fluid component in the tissue -75-85°~0) makes it possible to use the essentially novel method of plasma flow to obtain this layer under extensive bleeding condi-dons.
As mentioned above the difficulties of arresting intense bleeding are related to the need for separating in space the external boundary of tissue surface sublimation and for presenting in the depth of thf:
tissue the boundary of fluidcomponent vaporization. The latter boun-dary moves with blood flow rates towards the application and pre-vents theformation of a spongy necrosis layer, in particular in the ca-se of intensf~ bleeding.
The presence of various forms of energy resources is typical of plasma jet. 'rhe plasma flow energy is concentrated as a form of plas-ma enthalpi, a dynamic component of jet energy and broadband~
emission of :ionized gas. By changing the consumption of the plasma-generating gas, the cross-sectional area of the plasma jet and its tem-perature it becomes possible to control the dynamic pressure of the plasma flow. Consequently, it becomes possible to establish inte:r-action between the plasma jet and the spongy necrosis layer when the plasma jet penetrates this layer completely or partly. As a result, the plasma jet is partly cooled while heating the spongy necrosis layer and the remaining part of the jet energy is absorbed at the boundary of the vaporization of the tissue fluid component. The filtration of the cooled plasma-generating gas and of the vapour flow takes place throul;h the low pressure area of the plasma jet. The above-described modes of interactions het~~een the plasma jet and the tissue surface are s:hovsrn schematically in Fig. 3a and 3b.
This analysis points out a new principal possibility of conduc-t 0 ting energy to tissues by making use of a plasma-dynamic effect of an ionized gas flow. The high porosity of the spongy necrosis layer estab-lished by predetermined thermo-physical and gasodynamical parame-ters in the plasma flow results in gasodynamical and thermal penet-ration by the plasma jet in this layer 3b. In this case it becomes pos-sible to realise combined properties in the conduction of energy to tissue - volume power delivery to the spongy necrosis layer anal su-perficial heating of the fluid component of the tissue within the spongy layer.
The investigation of the porosity of the spongy layer has indica-ted that the cross-section of pores d and the porosity P with respect to typical parenc:hy-matous organs are: lungs d = 0.06-0.09 mm, P == 0.9-0.95, spleen d = 0.04-0.07 mm, P = 0.85-0.9, liver d = 0.035-0.06 mm, P = 0.75-0.8, kidney d = 0.02-0.04 mm, P = 0.65-0.7. As a result, the maximum. cross-section of a plasma jet that realizes penetration of plasma flow in the spongy necrosis layer to a depth of about 0.25 mm equals 3.5 mrn in lungs, 3.0 mm in the spleen, 2.5 mm in the liver and 1.5 mm in kidneys.
21 ~?~~J ~0 w0 96tt16i72 PGTISE9d100190 These data are applicable to an argon plasma jet. The use of lighter gases (neon, air and helium) leads to a reduction of the toler-able jet cross-section.
In order to establish the influence of plasma-generating gas pa-s rameters on the efficiency of arresting intensive bleeding investiga-tions have been carried out on arrests of bleeding in experimental subjects (53 dogs in more than S00 experiments). The dogs wore anesthezed and regional resections wore carried out. The area, of the wound surfaco was within 3-i4 cma. Before the coagulation of the 7.0 wound surface started the value of wound bleeding ~%as measured at a fixed time as also the wound area and from tho results it becamo possible to calculate tho mean flow-rate of blood from the wound and to define the intensity of the bleeding.
The mean bloeding rate from a liver wound lay within the aroa 1~~ of 0.6-1.8 mm/s, from a spleen wound 0.$-2.5 mm,/s. It should be pointed out that intensive bleeding corresponds to an average bleeding rata iif U > 1.0 mm/ s.
In accordanco therewith various sources of action worn compa-red with each other, possessing bieoding rates of 1.5-2.0 mm/ s. In the 20 investigations using microplasmatrons working on hokum, noon, ar-gon, nitrogon tend air, the plasma flow parameters could be changed u~ithin a wide range since these microplasmatrons were produced wit-hout taking into consideration some limitations required for the surgi-cal plasma generators, in particular the follo~xring: small dimensions, '~?:: convenience of manipulation and handling, stability and reliability, major overhauls, minimum content of erosion products an the elect-rodes, limited gas consumption to exclude of gaseous embolism and some other limitations.
The results of those investigations are shown in Figs. 4 and 5.
3D The black dots correspond to the values of the thermal power and plasma jet temperatures that provide reliable arrest of intensive bleeding. Lines I, II, III iilustrato the paramoters of the plasma jet bo-undaries beyond which it was not possible to stop bleeding.
When helium was used it eras possible to achieve reliable arrest ~5 of bleeding only at a bleeding rate of U < 1.0 mm/s.
Theso findings give evidence of a principal effect of the plasma-generating gas and of the thermo-physical properties of plasma. Parti-z~sc~~~c R'n 96!06572 PC1'ISE94l0079t1 cularly helium plasma fails to provide arrest of intensive bleeding in practically every range. By using argon, neon and air it becomes pos-sible to stop intensive bleeding but their use involves limitations of the thermo-physical parameters of the plasma flotv, of the extent of t~ consumption of the plasma-generating gas and of the plasma jet cross-sectional area.
To analyze the particularities of these limitations a numerical model of interaction between plasma flow and live tissue has been de-veloped. This model comprises:
1G - percentage of fluid component in the tissue - bleeding rate from wound - volume density of blood flow in the tissue - distinction of the thermo-physical characteristics of the tissue upon phase-structural changes and the formation of ATC
15 - distinction between temperatures of vaporization of the liquid com-ponent of the tissue and of the sublimation of the charring spongy layer gasodvnamics of plasma jet flow and vapour flow in the spongy ne-crosis layer.
20 The analysis of experimental data a.nd the realization of a nu-meric model show that the existence of limitations with respect to the plasma flow parameters that reliably arrest intensive bleeding is de-termined by the following principal characteristics of interaction bet-ween the plasma jet and the live tissue.
25 1. Boundary line I defnes the condition of gasodynamic penet-ration of the plasma flow into a porous dessicated tissue layer, to a depth of 0.2-0.25 mm, i.e. exceeding by 3-5 times the a characteristic cross-section of the pares d. The position of the boundary 1 is deter-mined by tissue species and depends on the cross-sectional area of 30 the plasma jet.
2. Boundary line II defines the condition of vaporization of the liquid component of the tissue at a rate exceeding the rate of bleeding.
The position of baundary II is determined by the extent of cooling of the plasma jet in the bulk of the spongy necrosis layer and is defined 35 by the parameter ~~r . P
Cpr . Icr . d i.e. the type of the plasma generating gas.
An analysis of the investigation of the heat transfer process in the po-rous systems in which gas flows shows that the intensity of the heat transfer in the pores is determined by 5 ~.f < 2.0 CPf . wf This in turn explains the dependence of the creation of a spongy des-sicated layer on the thermo-physical characteristics of the plasma flow obtained during experiment.
10 3. Boundary line III defines the condition of intensive sublima-tion of a carlr~onized spongy layer when the boundary of tissue subli-mation coincides with the boundary of the fluid component. Besides the limitations mentioned it is necessary to also take into account that the very considerable volume increase of the plasma-generating gas consumption may be the cause of the generation of gaseous em-bolism. Investigations show that in order to exclude gaseous embo-lism appearance the value of argo n and air consumption must not exceed 2.0 1/min. To increase the temperature of the argon plasma jet to a value above 10 500° K it is necessary to increase the discharge 2 0 current rate to more than 30A, which leads to the appearance of in-tensive erosion of the electrodes and to the occurrence of erosion pro-ducts in the field of operation. Considering these factors the par~~ne-ters most suitable for arresting intensive bleeding by means of a plasma jet are those falling within the marked areas.
2 5 The results from the investigation prove that the arrest of in-tensive bleeding as a result of plasma application takes place within a limited area of therTno-physical characteristics and of ~gasodynarmic parameters of the plasma jet. In addition, it does not provide a reliable arrest of inten;~ive bleeding when plasma-generating gases are used 3 0 that have high heat conduction, low heating capacity and low viscosi-ty.
The gas ~~roviding the widest range of change of the plasma. pa-rameters and able to arrest heavy bleeding is argon. The use of air as the plasma generating gas could also make it possible to stop intensi-3 5 ve bleeding but: within a much narrower range of plasma parameters compared with argon. It should be noted that in order to generate plasma flows having the above-mentioned parameters some limit;a-W0 961itG572 PCTJSE94J00790 dons of the plasma surgical instrument must be respected. In particu-lar, surgical microplasmatrons must generate plasma flows having an average mass temperature valid for the given type of gas (argon ar air) of a necessarily comparatively high value (argon 7500 - 10 500° K, air 4500 - 5000° K) and that must change only insignificantly during fluctuations of consumption of the plasma-generating gas (between the limits 1.0-2.0 1/min). Furthermore, the above parameters of plas-ma flow must be achieved ~~ith limitation of the value of the discharge current at a level near 30 A, excluding erosion of the electrodes of the microplasmatron.
In order to obtain a guaranteed hemostatic effect in the wound surface during a significant change of the bleeding intensity it is ne-cessary that the plasma-surgical instrument generates a plasma jet at a stable and comparatively- high level of its temperature. The jet tem-i 5 perature must not change significantly during the regulation of the consumption of the plasma-generating gas. To attain high-level plas-ma flow temperature it is necessary to diminish the cross-section size of the electric arc that heats the gas. This means that the chamber channel for heating the plasma.-generating gas by means of an electric arc must have a reduced cross-sectional size.
Proceeding from the required level of gas consumption (1.0-2.0 I/min) and taking into consideration the elimination of its thermal choking during heating the minimum cross-sectional area of the chamber channel for heating the plasma-generating gas must be O.S
2 5 mm and according to the investigation the optimal size thereof falls within the range of 0.7-1.0 mm in the case of air and 1.0-1.5 mm in the case of argon.
This crass-section of the electrical arc results in a high value of the electrical field strength in the channel and the length of the chan-nel that is necessary to heat the argon at the consumption rate of 2.0 1/min is insufficient to provide the electric discharge-distance strength. In this case a voltage drop in the plasma of the electric arc increases above 15-16 V (total value of voltage step input) and in con-sequence thereof instead of one long arc two sequential arcs appear, burning at a loner voltage and not providing gas heating to a high temperature.
To exclude electric breakdowns in the channel designated to heat the plasma-generating gas this channel is designed as electrically isolated sections. Its number must not be less than three: The highest electrical field strength is generated by the initial field of the electric arc at the cathode where a cooled gas enters into the arc. The length of the channel sections must be increased at a distance from the cathode since the field strength decreases. The most suitable channel geometry is to design it with a length of its first section at the cathode equalling its cross-sectional diameter (1~ = d~) with the length of each subsequent section being In = n . d~ where n represents the number of sections. The sections are interconnected via non-electr~ic-ally conductive gaskets. The first channel section is connected to the positive pole of a pulse periodic energy accumulator and to a high-voltage sparl~: gap (triggering system of a surgical microplasmatron).
The la~;t section is connected to the positive pole of a main power source in the surgical microplasmatron. A suitable length of this section i:~ two to three times the diameter of channel d. All chan-nel sections with the exception of the last one have the same cro;ss-sectional dimensions. The last section should, for the purpose of dis-secting tissues in optiriZal modes of operations, have a channeY width of 0.4-0.6 mm. Its design when employed for this purpose does not depend on thc~ kind of plasma-generating gas used.
When a microplasmatron is used to stop bleeding from a wound surface the cross-sectional size of the last channel section does, 2 5 however, depend on both tissue species and type of plasma-generating ga~~.
When argon gas is used to stop bleeding from surgical incisions on the lungs, the spleen and the liver the cross-sectional dimensions of the last channel sections should be 2.5 mm and in the case ~of kid-3 0 neys 1.5 mm.
In Fig. 7 a basic embodiment of a plasma surgical unit is shown, consisting of an electrically conductive body 6 similar to a pencil with a tip 7 for forming a plasma jet having the required cross-section and connected to a positive pole of a gas power source having 35 a positive potential. The body 6 comprises a cylindrical channel for heating the plasma-generating gas and it is formed from channel sec-tions 8, 9, 10 which are electrically isolated from each other and which are connecaed to the body 6 through an electrically isolated concentric bush 11 having channels 12 for conveyance of cooling fl,uicL to and from the gas heat-ing channel. The sections 8, 9, 10 are interconnected b;~ means of non-electrically conductive sleeves 22.
Sections 8, 9 and 10 each have a channel length ln, n being the number of sections as calculated from the cathode 13 and as illustrate°d as 11, 12 and is re~;peetively in Figure 7.
Sections 8 and 9 have an equal diameter d~. The last section 10, which is designed to form the plasma jet, is connected with the tip '7 and constructed as two co-axial cylindrical holes 17, 18 having an entrance diameter identical to the diameter of all preceding sections d~ and a.n exit hole 18 having th a diameter df = 0.4-0.6 mm and the length 1 = ( 1.5-2 .0) . dr. The channel cross-section dr at the exit hole 18 stops bleedings from large surgical wounds. The channel cross-section depends on the kind of plasma-generating gas and the species of the biological tissue.
The total nvumber of sections 8, 9 and 10 must not be less than three and the length of each subsequent section separated from the cathode must be In = n . d~.
The first section 8 is configured as a hollow cylindrical electrode which is connected with the body 6 via the electrically isolated bush 1 1 and with the cathode 13, 14 via the electrically isolated sealing bush 15.
The seconds are mutually interconnected via the non-electrically conductive sleeves 22.
The cathode consists of an electrically conductive tube 14 on one end of which the electrode 13 from a high-melting metal is fixed, providing the required level of current for thermal-electronic emission within the working range of discharged currents. The opposite end of the tube serves as a connection to the gas supply unit and is connect.°d with the negative poles of the basic energy source and of the trigger system of the mirroplasmatron. The electrically conductive tube 14 is formed with holes 16 for input and uniform distribution of the plasma-generating gas to the discharge chamber of the microplasmatron.
In order to work with inert plasma-generating gases (argon, crypton, xenon) the electrode of the cathode 13 is made from wolfram or its alloys (Fig. 6). In order to use air or steam as the plasma-generati:r~g gas the electrode of the cathode 13 is made from zirconium or hafnium (Figs. 7, 8).
When steam is used as the plasma-generating gas the second last and the last sections 9 and 10, respectively, are formed at t:he beginning and the end, respectively, with tangentially positioned channels 1~~ (see Fig. Band 8a ~~hich are connected to the channel heating the plasma-generating gas and having the volume separated from the cooling water by means of inserts 20 formed with pores positioned in-side a heat insulated cylindrical sleeve 21. The porous inserts 2(J
cover at lea:;t half of the external surface of the second last and the last sections. 9 and 10. The water-filled cavity is connected to a system regulating tl~ie water pressure in order to control the quantity of steam consumption. The discharge current provides the required tempera-ture of the p:(asma flows and the size of the steam consumption :is between 3.0 and 8.0 A.
It should be obvious that the eschar resulting from the use of the device proposed in accordance v~rith the subject invention :has a well defined spongy necrosis layer having a thickness of 0.15-0.25 mm, which corresponds to between 3 and 5 characteristic cross-2 0 sections of pores therein.
The porous layer in accordance with the invention has a well defined boundary to~~ards the subjacent tissue, which indicates the highly restricted heat penetration into the tissue and the localisation in this area of the boundary of vaporization of the liquid component of the tissue.
A comparison of the thickness of the spongy necrosis layer (SNL) resulting from the exposure to plasma and laser~on liver and spleen wounds with intensive bleeding shows that in the first case the SNL has a thi~~kness which is between 3 and 5 times larger than in the second case.
The pore size upon plasma exposure is 1.5 times less that upon laser exposure and the thickness of tissue intermediate the pores is 1.3 times large°r. This indicates that the permiability of a spongy des-sicated layer i;5 approximately similar to that of a dessicated tissue obtained by means of methods involving slow heating at a tempera-ture which only slightly exceeds that of vaporization of the tissue liq-uid component of the tissue.
1;~~U~~
WO 9b106572 PCTISE9dIp0790 These investigations of the reparative processes in the tissue of liver, lungs and kidneys have shown that the healing after the expo-sure to argon, neon and helium plasma flows takes place in the can-ventianal way and is not dependent on the type of gas used. The 5 healing of organs takes place without deformation of rough scars therein.
The device in accordance with the invention is not limited to the features shaven and described but could be varied in several ways within the scope of the appended claims.
~. o
Claims (7)
1. A device to stop bleeding in live human and animal tissue and to form an escarre by means of a plasma jet, - the device comprising means for the generation of plasma, comprising an electrically conductive body and a gas power source, said electrically conductive body having the appearance of a pencil and being formed with a tip for forming the required cross-section of the plasma jet, said body being connected to a positive pole of said gas power source having a positive potential, - the body comprising a cylindrical channel for heating a plasma-generating gas which channel is formed from a number of sections, each one of which is connected to the body via electrically insulated bushes which are concentric with the sections, characterised in that the number of sections are longitudinally separated and are electrically insulated from each other and the electrically insulated bushes are formed with channels designed to conduct cooling liquid to and from the gas-heating channel, and in that said sections have a channel length l n, n being the number of sections calculated from a cathode, the total number of said sections being at least three, said sections, except the outermost one, having an equal channel diameter d c, and the length of each subsequent section, separated from the cathode, being l n = n . d c.
2. A device as claimed in claim 1, wherein the outermost section is connected with the tip portion of the body and is shaped as two co-axial cylindrical bores the entrance diameter of which equals the diameter d c of all preceding sections and the diameter do at the exit hole thereof, which diameter d f equals 0.4-0.6 mm and the length 1 of which equals (1.5-2.0) × d f.
3. A device as claimed in claim 1 or 2, wherein the innermost section is in the form of a hollow cylindrical electrode which is connected to the body by way of the electrically insulated bush, and comprises the cathode which is connected to the section through an electrically insulated sealing gasket.
4. A device as claimed in claim 1, 2 or 3, wherein the cathode is an electrically conductive tube to one end of which a high-melting metal electrode is attached, said electrode providing a required current level upon thermo-electronic emission within an operative range of discharge currents in order to heat the plasma to a sufficiently high temperature, and in that the opposite end of said tube serves as the connection for gas transportation and for the negative pole of the base energy source and a negative pole of a trigger system of a microplasmatron, and in that the electrically conductive tube is formed with holes to convey and evenly distribute the plasma-generating gas into a flow chamber of said microplasmatron.
5. A device as claimed in claim 3 or 4, wherein the electrode of the cathode is made from wolfram or its alloys.
6. A device as claimed in claim 3 or 4, when in use with air as the plasma-generating gas, wherein the electrode of the cathode is made from zirconium or hafnium.
7. A device as claimed in any one of the claims 1 - 2, when in use with steam as the plasma-generating gas, wherein the second outermost and the most outermost sections are formed at their front and rear parts with tangentially positioned channels which are connected to the channel for heating the plasma-generating gas and the channel is separated from cooling water by means of porous inserts disposed in a thermo-insulating cylindrical bushing, and in that said porous inserts cover at least half of the outer surface of the second outermost and the outermost sections.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE9301850A SE503334C2 (en) | 1993-06-01 | 1993-06-01 | Device for stopping bleeding and forming a crust by means of a plasma jet |
| PCT/SE1994/000790 WO1996006572A1 (en) | 1993-06-01 | 1994-08-29 | A device to stop bleeding in living human and animal tissue |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2198000A1 CA2198000A1 (en) | 1996-03-07 |
| CA2198000C true CA2198000C (en) | 2006-08-22 |
Family
ID=26661751
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002198000A Expired - Lifetime CA2198000C (en) | 1993-06-01 | 1994-08-29 | A device to stop bleeding in living human and animal tissue |
Country Status (4)
| Country | Link |
|---|---|
| AU (1) | AU7865794A (en) |
| CA (1) | CA2198000C (en) |
| SE (1) | SE503334C2 (en) |
| WO (1) | WO1996006572A1 (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE518902C2 (en) * | 1998-06-24 | 2002-12-03 | Plasma Surgical Invest Ltd | plasma Cutter |
| SE524441C2 (en) | 2002-10-04 | 2004-08-10 | Plasma Surgical Invest Ltd | Plasma surgical device for reducing bleeding in living tissue by means of a gas plasma |
| SE529053C2 (en) | 2005-07-08 | 2007-04-17 | Plasma Surgical Invest Ltd | Plasma generating device, plasma surgical device and use of a plasma surgical device |
| EP2405721B1 (en) * | 2007-08-06 | 2016-04-20 | Plasma Surgical Investments Limited | Pulsed Plasma Device |
| WO2011091855A1 (en) * | 2010-01-29 | 2011-08-04 | Plasma Surgical Investments Limited | Methods of sealing vessels using plasma |
| EP2591742A4 (en) | 2010-07-07 | 2018-01-03 | National Institute of Advanced Industrial Science And Technology | Plasma irradiation treatment device |
| US9089319B2 (en) | 2010-07-22 | 2015-07-28 | Plasma Surgical Investments Limited | Volumetrically oscillating plasma flows |
| EP4205515A2 (en) | 2020-08-28 | 2023-07-05 | Plasma Surgical Investments Limited | Systems, methods, and devices for generating predominantly radially expanded plasma flow |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3991764A (en) * | 1973-11-28 | 1976-11-16 | Purdue Research Foundation | Plasma arc scalpel |
| EP0277233B1 (en) * | 1986-08-11 | 1990-04-04 | 2-i MOSKOVSKY GOSUDARSTVENNY MEDITSINSKY INSTITUT IMENI N.I. PIROGOVA | Device for plasma-arc cutting of biological tissues |
| US4788408A (en) * | 1987-05-08 | 1988-11-29 | The Perkin-Elmer Corporation | Arc device with adjustable cathode |
| WO1992019166A1 (en) * | 1991-04-15 | 1992-11-12 | Nauchno-Issledovatelsky Institut Energeticheskogo Mashinostroenia Moskovskogo Gosudarstvennogo Tekhnicheskogo Universiteta Imeni N.E.Baumana | Device for plasma surgical treatment of biological tissues |
-
1993
- 1993-06-01 SE SE9301850A patent/SE503334C2/en unknown
-
1994
- 1994-08-29 AU AU78657/94A patent/AU7865794A/en not_active Abandoned
- 1994-08-29 CA CA002198000A patent/CA2198000C/en not_active Expired - Lifetime
- 1994-08-29 WO PCT/SE1994/000790 patent/WO1996006572A1/en active IP Right Grant
Also Published As
| Publication number | Publication date |
|---|---|
| SE9301850D0 (en) | 1993-06-01 |
| SE503334C2 (en) | 1996-05-28 |
| AU7865794A (en) | 1996-03-22 |
| WO1996006572A1 (en) | 1996-03-07 |
| SE9301850L (en) | 1994-12-02 |
| CA2198000A1 (en) | 1996-03-07 |
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| EEER | Examination request | ||
| MKEX | Expiry |
Effective date: 20140829 |