Abstract:
A combination pressurized airflow and thermal cutting tool constructed as a dual-use thermal airflow tool for directed heating and drying of a specific area in surgical procedures, such as, by way of example, in eye cataract surgery where it is primarily used for needs related to the operation of a thermal cutting tool. The thermal airflow tool comprises a probe having an elongated, hollow body adapted to provide electrical power to a burning ring formed at a distal end thereof, and an air channel for conducting pressurized airflow to the distal end of the probe, with at least two apertures radially disposed at the distal end of the probe. The thermal airflow tool is in physical and electrical connection with an air pressure unit and thermal power unit, respectively, for directing and concentrating at least one of the pressurized airflow and heat at the distal end of the thermal airflow tool onto a surgical area when electrical power is applied to the thermal airflow tool.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to medical devices and systems, and more particularly to a thermal airflow tool and an associated system for improving thermal surgical procedure.  
       BACKGROUND OF THE INVENTION  
       [0002]     Thermal surgical procedure is improved and made more efficient by concentrating heat at a position proximate to a surgical site. In eye cataract surgery, for example, the thermal procedure is usually complicated by the need for multiple instruments: a cutting tool, an air pressure inlet, a water pressure inlet, and related surgical and electrical equipment. It would be useful to simplify such surgical procedures by providing a combination tool that concentrates heat on the surgical site and which is constructed so as to be convenient to handle and which can be used for providing both regulated heating and airflow pressure directed to a surgical site.  
       SUMMARY OF THE INVENTION  
       [0003]     Accordingly, it is a principal object of the present invention to overcome the disadvantages of the prior art and to provide a combination pressurized airflow and thermal cutting tool and an associated system. The airflow and thermal cutting tool, hereinafter thermal airflow tool of the present invention, is a dual-use tool for directed heating and drying of a specific area in surgical procedures, such as, by way of example, in eye cataract surgery where it is primarily used for needs related to the operation of a thermal cutting tool.  
         [0004]     Thus there is provided a thermal airflow tool for performing a thermal surgical procedure, the thermal airflow tool comprising: 
        a probe comprising: 
            an elongated, hollow body adapted to provide electrical power to a burning ring formed at a distal end thereof;     an air channel for conducting pressurized airflow to the distal end of the probe;     at least two apertures radially disposed at the distal end of the probe in a non-perpendicular plane in respect to the axis of the hollow body for release of pressurized airflow, the air channel and the at least two apertures being in physical communication with one another within the hollow body of the probe; and    
            an input connector mounted on a proximal end of the probe for connecting the probe with respective sources of electrical power and pressurized airflow, the input connector having at least one resistor for controlling and monitoring the electrical power provided to the burning ring.        
 
         [0010]     There is also provided a thermal airflow system comprising: 
        an air pressure unit for providing pressurized airflow having substantially linear characteristics;     a thermal power unit for providing electrical power to the system; and     a thermal airflow tool in physical and electrical connection to the air pressure unit and the thermal power unit, respectively, for directing and concentrating at least one of the pressurized airflow and heat at the distal end of the thermal airflow tool onto a surgical area when electrical power is applied to the thermal airflow tool.        
 
         [0014]     The thermal airflow tool, in one embodiment of the invention, is provided with a burn-out resistor which functions as a fuse to limit the heating time in accordance with a predetermined temperature setting referenced to the size orifice needed in the thermal procedure. When the temperature has been reached, the burn-out resistor breaks the circuit and the heating element is turned off. The thermal airflow tool in this embodiment is for one-time use and is constructed as a disposable plug-in unit.  
         [0015]     In another embodiment of the invention, the thermal airflow tool is provided with a fixed resistor of about 1000 ohms enabling repeated use of the thermal airflow tool for burning an orifice with a pre-set diameter in eye capsulotomy surgery.  
         [0016]     Other features and advantages of the invention will become apparent from the following drawings and descriptions. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     For a better understanding of the invention in regard to the embodiments thereof, reference is made to the following drawings, not shown to scale, in which like numerals and letters designate corresponding sections or objects throughout, and in which:  
         [0018]      FIG. 1  is a general view of the layout of the major components comprising the system of the invention in accordance with an embodiment thereof;  
         [0019]      FIGS. 2A and 2B  are isometric views of the probe of the thermal airflow tool of  FIG. 1  and an enlarged, detailed view of a burning ring in accordance with the principles of the present invention, respectively;  
         [0020]     FIGS.  3 A-D are orthographic views of the hollow tube construction of the probe, and axial cross-sections showing the construction of air pressure release apertures;  
         [0021]      FIG. 4A  is an isometric view of a plug-in thermal airflow tool in accordance with an embodiment of the invention;  
         [0022]      FIGS. 4B and 4C  are isometric external views of the plug end and a side view, respectively, of the thermal airflow tool of  FIG. 4A  shown with a protective housing;  
         [0023]      FIG. 5  is a schematic electrical diagram of an embodiment of the invention illustrating a dual-resistor electrical circuit for the airflow tool of  FIG. 4A ;  
         [0024]      FIG. 6  is a schematic electrical diagram of another embodiment of the invention illustrating a single-resistor electrical circuit for the airflow tool of  FIG. 4A ;  
         [0025]      FIG. 7  is a general circuit diagram of the thermal airflow tool of  FIG. 4A  shown connected electrically to a central processing unit in accordance with the principles of the invention;  
         [0026]      FIG. 8  is a schematic block diagram of an embodiment of the system of the invention; and  
         [0027]      FIG. 9  is a cross-section view of a capsulotomy application of the airflow tool of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0028]     The present invention provides a system for surgical thermal procedures, such as for capsulotomy in eye cataract surgery, and a dual-purpose thermal airflow tool generally useful in this as well as in other kinds of surgical procedures. The system comprises two main parts, an air pressure unit and a thermal power unit connected to a thermal airflow tool.  
         [0029]     Referring now to  FIG. 1 , there is shown a general view of the layout of the major components comprising the system of the invention in accordance with an embodiment thereof. An air pressure unit  10  provides pressurized air for the system, while a thermal power unit  12  provides regulated heating, suitable, for example, for safely performing capsulotomy in eye cataract surgery (see  FIG. 9 ). An air pressure input pipe  14  passes through a hollow handle  16  and directs airflow into thermal airflow tool  18  along a tube (see  FIG. 2 ) passing through the central axis of both handle  16  and thermal airflow tool  18  when joined, as by example, with matching connectors, as is known by those skilled in the art, so as to direct a controlled stream of this pressurized air onto the surface of a surgical site. In the example shown in  FIG. 1 , the electrical connection to thermal unit  12  is by a three-wire power cable  24  wired from thermal power unit  12  to receptacle  22  disposed in the distal end of handle  16 .  
         [0030]     Individual foot-pedal switches (see  FIG. 8 ) turn the power on/off to both units  10 ,  12  of the system, while controls  26  and  28  on each of the respective air pressure unit  10  and thermal power unit  12  allow a scaled adjustment and fine-tuning control of air and heating requirements, respectively, such as burning time, while individual bar graph displays  30 ,  32  provide a user with visual representations of the respective air pressure and heating levels being provided closest to the surgical site at the distal end of the thermal airflow tool  18 .  
         [0031]      FIGS. 2A and 2B  are isometric views of the probe of the thermal airflow tool of  FIG. 1  and an enlarged, detailed view of a burning ring in accordance with the principles of the present invention, respectively.  
         [0032]     In  FIG. 2A , probe  52  is shown as a hollow tube comprising two, electrically conducting half-sections, a negative half-section  34  and a positive half-section  36  insulated from one another by axial cuts  38  extending along most of the length from pressurized air input tube  42  to a burning ring  40  formed on the distal end of probe  52 . Two apertures  48 ,  50  are disposed adjacent to burning ring  40  on opposing sides of the longitudinal axis of probe  52  for advantageously concentrating and directing pressurized air onto a surgical site (see  FIG. 9  for example).  
         [0033]     Apertures  48 ,  50  are formed in a non-perpendicular plane in relation to the axis of probe  52  leaving just a small amount of material which forms neck pieces  49 ,  51  physically and electrically connecting burning ring  40  with each half-section  34 ,  36  respectively. Burning ring  40  comprises a thin metal ring obliquely truncated in a plane parallel to the plane of apertures  48 ,  50  so as to facilitate maximal contact with the surface of a surgical site, such as the spherical surface of an eye when the thermal airflow tool is used in this application ( FIG. 9 ).  
         [0034]     Burning ring  40  is heated when an electric current is applied to contact points in electrical contact with burning ring  40  via the two neck pieces  49 ,  51  which secure burning ring  40  to each of the electrically conducting half-sections  34 ,  36 . Burning ring  40  is fabricated of a heat-conducting material, such as titanium, steel, and the like, which concentrates the heat at the extreme distal edge of probe  52 .  
         [0035]     FIGS.  3 A-D are orthographic views of the hollow tube construction of the probe, and axial cross-sections showing the construction of air pressure release apertures. Probe  52  of the present invention is typically a tubular body, cylindrical in shape, although other shapes are also usable. The interior of this body is lined with a non-conducting, insulating material forming sleeve  44 , such as vinyl plastic, or nylon. Air input tube  42  is also made of non-conductive material, such as rubber or plastic (vinyl) and extends slightly outwardly from proximal end of probe  52  to join with air pressure tube  14  (see  FIG. 1 ) connected to air pressure unit  10  (see  FIG. 1 ). Air input tube  42  extends internally along the length of probe  52  to the distal end adjacent to burning ring  40 .  
         [0036]      FIG. 4A  is an isometric view of a plug-in thermal airflow tool in accordance with an embodiment of the invention. A non-conductive sleeve  54  retains the two half-sections  34 ,  36  (see  FIG. 2A ) at about a mid-portion of probe  52  which is embedded in a non-conductive, three-prong connector base  60  provided with prongs  72 ,  74 ,  76  and respective electrical contacts  62 ,  64 ,  66  on an inner face of connector base  60 . A first resistor  56  and a second resistor  58 , in a preferred embodiment of the invention, are provided mounted between contacts  62 ,  64 , and  66  as shown in  FIG. 4A . The functions and operation of the circuit is explained below in relation to  FIG. 7 .  
         [0037]      FIGS. 4B and 4C  are isometric external views of the plug end and a side view, respectively, of the thermal airflow tool of  FIG. 4A  shown with a protective housing. The proximal portion of probe  52  is provided with a housing unit  68  for safety of operation and for protecting inner components (see  FIG. 4A ) mounted on connector base  60 . When plugged into a matching female connector (see  FIG. 1 ) mounted in handle  16  (see  FIG. 1 ), the three prongs  72 ,  74 ,  76  electrically connect probe  52  to a power source (not shown) within thermal unit  12  ( FIG. 1 ). Note the centrally disposed orifice  70  in the externally oriented face of input connector base  60  to which air input tube  42  (see  FIG. 2 ) is tightly joined when the respective, matching connectors are fully connected.  
         [0038]      FIG. 5  is a schematic electrical diagram of a preferred embodiment of the invention illustrating a dual-resistor electrical circuit for the thermal airflow tool of  FIG. 4A .  
         [0039]     The two halves  34 ,  36  of the body of probe  52  serve as positive and negative terminals in relation to one another and burning ring  40 . They are wired to the contacts  62 ,  64 ,  66  electrically connected to the three prongs  72 ,  74 ,  76  mounted in input connector base  60 . A reference resistor  56  and a second, burn-out type resistor  58  are mounted between the outer prongs  72 , 76  and middle prong  74 . The purpose of these resistors  56  and  58  will be explained in the description of the overall electrical operation of the system of the invention given below in reference to  FIG. 7 .  
         [0040]     Burning ring  40  can have different diameters, from 0.5 mm up to several millimeters. If diameters are changed, the current and time frame inputs will be directly affected and result in different parameters for these two factors. To control the heating level of burning ring  40  and protect it from overheating, a calibration resistor  56  in the range of 200 ohms to 18 kilo-ohms in ten steps is inserted between the positive connector  62  and connector  64 . A second fuse-type resistor  58  is inserted between connector  64  and connector  66 . The values of the burn-out resistor  58  are calibrated in accordance with the size of the diameter of burning ring  40  so as to disable the heating portion of the thermal airflow tool  18  when current flows through the circuit, burning out the second fuse-type resistor  58  once a pre-set temperature is reached. The thermal operation of the airflow tool  18  is thus limited to a single limited-life heating cycle when provided with the fuse-type resistor  58 . The thermal airflow tool is conveniently designed to be replaceable for subsequent use by use of a quick release input connector configured with three prongs  72 ,  74 ,  76 . A matching female connector  22  on the handle  16  (see  FIG. 1 ) provides for quick-release and replacement of the thermal airflow tool.  
         [0041]     When a current is applied through electrical power connector  66  and power connector  62  to two points in an angle of 180° of the circumference, burning ring  40  heats up. The duration and power depends on the material used, preferably a titanium alloy, but other alloys are also usable. Titanium is used in a preferred embodiment of the invention due to its advantageous properties of high heat and current resistance.  
         [0042]      FIG. 6  is a schematic electrical diagram of another embodiment of the invention illustrating a single-resistor electrical circuit for the thermal airflow tool of  FIG. 4A . The effect of using only one resistor  58  is to provide a thermal airflow tool which is reusable if necessary, during one continued surgical procedure on the same patient. The burn-out effect in the use of a dual-resistor thermal airflow tool is not applicable in this embodiment of the invention since the thermal airflow tool continues to function within the pre-set limits of the value of the resistor  58 .  
         [0043]      FIG. 7  is a general circuit diagram of the thermal airflow tool of  FIG. 4B  shown connected electrically to a central processing unit in accordance with the principles of the invention.  
         [0044]     In an initial test cycle, when a +5 voltage is applied to the circuit at I input, the current flows through prong  72  in the airflow tool  18  and passes through burning ring  40 . In parallel, the current passes across a load reference resistor  56  which in a preferred embodiment of the invention is rated at between 1K to about 20K ohms, and which is in electrical connection with resistor R 2  rated at about 10K ohms and from there through return at ground G. Pin P 1  in microprocessor  84  is activated and reads the voltage applied to the circuit. The fuse-like resistor  58  is determined to be operative if the reading is +5V. However, if the voltage is less than or equal to 4.5V, the fuse-like resistor  58  is not operative. The microprocessor is programmed to start a timer (not shown) for using the thermal power unit  12  for a period over about 10 to 20 minutes. A pulse of time t 1 , preferably of 100 ms is applied to field effect transistor F 1  through pin P 3  which promptly kills fuse-resistor  58 , that is, makes it inoperative.  
         [0045]     A second cycle in the circuit of  FIG. 7  tests the reference resistor  56  in airflow tool  18 . The input voltage at I is +5V which passes through prong  72  of airflow tool  18  and across reference resistor  56  of the range value 1K to 20K ohms and returns to ground G via middle test-prong  74  and across resistor R 2  of 10K ohms. The microprocessor  84  reads the reference resistor  56  whose value is between 1K ohm and 20K ohms in a preferred embodiment of the invention and is set in relation to the diameter of burning head  40 . For example: 1K ohm represents a diameter of 1 mm; 2K ohm represents 1.2 mm; and so on, up to 20K ohms which represents 5 mm diameter. Furthermore, a 1K ohm value represents a reference value of 4.5V on pin P 1  of microprocessor  84  progressively increasing up to 20K ohms which represents a 2.3V reference value on pin P 1 .  
         [0046]     Finally, the heating cycle for burning ring  40  is activated via microprocessor  84  which switches on field effect transistor F 2  over a time t 2  set between 10 ms up to 400 ms, in a preferred embodiment of the invention, and which is determined in relation to the diameter of burning ring  40  (read out by the reference resistor  56 ). Fine adjustment can be made with the potentiometer switch  28  on the front panel of thermal power unit  12 .  
         [0047]      FIG. 8  is a schematic block diagram of an embodiment of the system of the invention.  
         [0048]     A DC-motor-controlled membrane air pump  80  produces the desired air pressure depending on rotation speed. The rotation speed is controlled by the microprocessor  82 . On the air pump output  84 , a security valve  86  is disposed to rapidly relieve undesirable build-up of air pressure from the system. The valve  86  exhausts the pressurized air under non-current conditions to output  88 . The system pressure between the valve  86  and an air filter  90  is checked by a pressure sensor  92  in communication with microprocessor  82 . The pressurized air flows out through the air input tube  14  which is connected from air pressure unit  10  to the thermal airflow tool  18  (see  FIG. 1 ). Another flow control pressure sensor  94  is disposed between filter  90  and air input tube  14  which monitors the return air pressure. Sensor  94  checks the return pressure and valve  96  is responsible for the release of overpressure through exhaust  98 .  
         [0049]     To prevent system swinging, a damping air chamber  100  is disposed between valve  94  and valve  96 . Valve  96 , in a preferred embodiment of the invention, is a high-speed pulse-width-modulated (PWM) valve chosen for its linear characteristics. The system pressure is pre-selected by control switch  26 , which is provided as a potentiometer in a preferred embodiment of the invention, and monitored visually with the aid of a bar graph display  32  (see  FIG. 1 ). A convenient footswitch  102  allows for on and off control of the air flow while freeing the surgeon&#39;s hands for necessary manipulation of the thermal airflow tool  18 . The thermal unit  12  is controlled for time and power by a second microprocessor  104  and pre-selected by control switch  28  which is provided as a second potentiometer.  
         [0050]     While connecting thermal power unit  12  to handle  16  (see  FIG. 1 ), the microprocessor  104  reads out the value of resistor  56  (see  FIG. 7 ) and selects the necessary power range and time. In parallel to the identification resistor  56 , a second resistor  58  (see  FIG. 7 ) is provided with a 1 ohm/0.125 W resistance which is blown out (fused) by a starting current. After the second resistor  58  is blown, the microprocessor  104  is able to read out the identification resistor  56 . For a much higher identification resistor resistance, it can never be fused. The microprocessor  104  is programmed to allow the user to use the thermal unit  12  for a limited time only. The timer control switch  28 , on thermal unit  12  is, in a preferred embodiment of the invention, a second potentiometer, allowing a user to set this time frame.  
         [0051]     In an alternate embodiment of the invention, the second resistor  58  is omitted and the airflow tool is consequently reusable, but at a fixed heating level for a given diameter burning ring.  
         [0052]     The burning cycle is controlled by microprocessor  104  which is operated by second foot switch  108 . The power supply  110 , connected to a power source by cable  102 , is a standard 110/230 V input and provides a 24V/5V output. An on-off power switch  112  is provided for the power source housed within thermal power unit  12 .  
         [0053]      FIG. 9  is a cross-section view of a capsulotomy application of the airflow tool of the invention. The thermal airflow tool  52  is inserted through the cornea  116  of an eye  115 . Burning ring  40  is carefully moved into close proximity to the anterior surface  120  of the lens  122  which is situated below the iris  118  in the lumen of the eye  115 . Pressurized airflow enters probe  52  at the proximal end (shown by arrow) and passes through an inner air input tube  42  (dashed lines) until exiting (indicated by lateral arrows) from distal apertures  48 ,  50  (see above description and  FIGS. 2-3 ). The pressurized airflow is advantageously dispersed around as well as directed directly onto the surgical site behind the cornea  116  and helps maintain the full configuration of the lumen while simultaneously, burning ring  40  decomposes the target capsule as required. Removal of unwanted substances resulting from the surgery is performed using conventional surgical procedures well-known to those skilled in the art. The use of the thermal airflow tool of the present invention leaves only a tiny hole, perhaps less than three millimeters in diameter, in the cornea and saves making larger incisions in the eye which might take longer to heal and cause complications.  
         [0054]     Having described the invention with regard to certain specific embodiments, it is to be understood that the description is not meant as a limitation, since further modifications may now suggest themselves to those skilled in the art, and it is intended to cover such modifications as fall within the scope of the invention.