Abstract:
An improved injection device is operated in a manual mode in which it delivers a liquid drug to a patient at a rate determined all the time by a control member, and a cruise control mode in which the preselected rate is maintained by the controller after the control member is released by a clinician. The control member may be used to select one of two liquid delivery rates, or alternatively a delivery rate may be selected which may have values between an upper and a lower limits. If the device is operated in the cruise control mode, an override switch must be activated to reset the rate.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/226,446 filed Aug. 18, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     a. Field of Invention 
     This invention pertains to an automated anesthetic delivery apparatus particularly suited for the dental and medical fields, and more particularly to an apparatus and method in which the rate is controlled and maintained automatically until reset or otherwise changed by the operator. 
     b. Description of the Prior Art 
     While local anesthetics eliminate the often excruciating pain that would otherwise be suffered during medical procedures, dental extractions, drilling, etc., the medical and dental patient is still subject to pain from the hypodermic injection of the anesthetic into the local tissues of the body. 
     It is well established that more than 50% of adult patients fear injections in general, and even a greater number especially fear injections in the mouth during a dental procedure. 
     Accordingly, it would be desirable to provide a medical and dental anesthetic injection delivery system which substantially eliminates the pain suffered by a patient during injection of anesthetic into the mouth or other tissues of the body. 
     U.S. Pat. No. 6,022,337, incorporated herein by reference generally describes a local anesthetic delivery system which renders the nerve bundles which supply the teeth and supporting dental structures disabled in the area of the injection and in the path of the needle before a pain sensation is perceived by the patient. The system comprises a drive unit for selectively delivering anesthetic through a controllable handpiece unit which carries a needle for tissue penetration. Operation of the drive unit can be selectively controlled so that different amounts of anesthesia may be delivered through the needle, depending upon whether the practitioner is either penetrating the tissue or has otherwise reached the location within the tissue where nerve disability is required. 
     The system uses a linear activator to deliver a controlled amount of anesthetic from a cartridge that is locked into the drive unit. The drive unit which can be operated by a foot pedal that is selectively depressed in order to deliver anesthetic through the handpiece unit. 
     The system is designed to accommodate a local anesthetic cartridge and a variety of needle sizes. The drive unit of the system includes a motor and an on-board microprocessor to facilitate control of anesthetic flow. The drive unit, utilizing the technology described in U.S. Pat. Nos. 4,747,824 and 5,180,371, and incorporated herein by reference, enables delivery of an anesthetic solution at a constant pressure and volume, regardless of variations in tissue resistance. At the delivery end of the needle, the system delivers a minute amount of the anesthetic which precedes the needle during injection in the dental tissue, creating in effect an anesthetic pathway. The combination of an anesthetic pathway and controlled pressure and volume (flow rate) results in an effective and pain-free injection. Importantly, the system further incorporates foot pedal  29  is operatively connected to air hose  31 , which in turn is coupled to a pressure sensor  64  located inside unit  13 . In operation of system  11 , the pressure change from pedal  29  is detected by the sensor  64 . Sensor  64  then generates a corresponding control signal used to control the flow of the anesthetic solution. In the preferred embodiment, as described in more detail below, when foot pedal  29  is slightly or partially depressed, system  11  operates at a slow speed. When foot pedal  29  is firmly or fully depressed, system  11  operates at a faster speed. The system can be programmed to have multiple rates of flow, not limited to two speeds. 
     While this system operates satisfactorily, some physicians or dentists may not be completely satisfied with it because it requires the pedal to be maintained in a certain position for an extended time period. 
     OBJECTIVES AND SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the invention to provide a local anesthetic delivery injection system which can be used for all known medical and dental injection procedures and having an improved automatic mode of operation. 
     A further objective is to provide a device which reduces the strain on the dentist or other health care practitioner for extended injection sections. 
     A further objective is to provide an injection device that has an automated mode of operation that allows the physician, dentist or health practitioner to devote his attention to other details and pay attention to the system only when a change in its operation is required. 
     Yet another object of the invention is to provide a dental anesthetic injection delivery system which enhances the precision and accuracy of anesthetic delivery. 
     Still other objects and advantages of the invention will in part be obvious, and will in part be apparent from the following description. Briefly, an injection device constructed in accordance with this invention includes an electrically controlled pump, a handle terminating in a needle through which the medication is ejected and a foot switch or other similar control means (i.e., hand control) used to activate the pump controller. The control means may have several positions. In one embodiment, the control means includes three positions: OFF, SPEED 1 and SPEED 2. The pump is off in the off position, at SPEED 1 the medication is administered at a first flow rate, and at SPEED 2 the pain killer is administered at a second, higher flow rate. Alternatively the control means may be adapted to have either many discrete positions or could be adjusted continuously between the SPEED 1 and SPEED 2 positions and the flow rate may be changed substantially continuously between an upper and a lower speed limit. Preferably the control means may be spring loaded or otherwise biased, so that when it is SPEED 1 or SPEED 2 position and is then released, it goes to the OFF position automatically. Importantly, according to this invention, the pump controller is provided with several modes of operation. In one mode of operation, which may be termed a manual mode, the pump controller monitors the position of the control means continuously and operates the pump in a responsive manner so that if the control means is in the SPEED 1 position, the pump is operated at SPEED 1, in the SPEED 2 position, the pump is operated at SPEED 2 (and fluid is delivered at a corresponding rate) and if the control means is in the OFF position, the pump motor is turned off, or it goes into an automatic aspiration mode. Another mode of operation is a so-called cruise control mode. In this mode of operation the pump controller operates in a manner similar to a cruise control in a car. More particularly, in the cruise control mode, when control means is released, the pump controller maintains the previous operation of the pump until a separate control means such as an override switch is activated to change the mode of operation of the pump. This separate control means may consist of a separate push button on the handle, on the controller or on the pedal switch. It may also be achieved as currently embodied via software configuration. A “window” of time exists in which removal of ones foot from the foot control activates “cruise-control”. This “window” may be defined within the software and activated by removal of the foot control. 
     The invention is also applicable to other medical and/or dental devices such as ultrasonic scalers, polishing devices, and other rotary and electronic instruments which are operated by a clinician at a controlled rate or speed. 
     In one aspect, the invention pertains to an injection device adapted to inject a therapeutic liquid into a patient under the control of a clinician, said device comprising a handle adapted to be held by a clinician for administering the liquid; a pump adapted to selectively deliver the liquid to said handle; a motor adapted to operate said pump at a selected rate in accordance with a control signal; control member operated by the clinician to select said rate, said control member having a first position associated with the selected rate and a second position; and a microprocessor coupled to said control member and adapted to generate said control signal after said control member has been operated and released by the clinician to generate said control signal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a fuller understanding of the invention, reference is made to the following description, taken in connection with the accompanying drawings, in which: 
     FIG. 1 shows a somewhat schematic representation of an injection device constructed in accordance with this invention; 
     FIG. 2 shows a block diagram of the device of FIG. 1; shows a manual mode of operation of the injection device of FIG. 1; and 
     FIG. 3 shows a flow chart showing the operation of the device of FIGS. 1 and 2 in a manual mode; 
     FIG. 4 shows a cruise control mode of operation of the injection device of FIGS. 1 and 2; and 
     FIG. 5 shows an alternate mode of operation of the injection device of FIGS. 1 and 2. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 and 2 show generically a device  100  can be used to inject or otherwise introduce (and, selectively aspirate) a liquid into a patient. As shown in the Figures, device  100  includes a housing  102  with a plurality of indicators  104 , and control buttons  106  or other user selectable data and command input means. One of the control buttons  106  is a rotatable knob  108  having a plurality of positions, as discussed in more detail below. 
     Disposed in or otherwise associated with the housing is a reservoir containing a drug, an anesthetic or other liquid that may be used by a doctor or other health care provider to perform a medical or dental procedure on the patient. 
     Device  100  further includes an elongated tube  108  having one end attached to the housing  102  and the other end attached to a handle  110 . The handle  110  includes a syringe  112 . 
     Device  100  further includes a foot pedal  114  attached to the housing  116  by an air hose  116 . The pedal  114  is made with a primary foot control element  118  having three or more positions, as discussed in more detail below. Also mounted on the pedal  114  is a second control element  120 . 
     FIG. 2 shows a block diagram of the electrical elements of the device  100 . The device includes a microprocessor  150  which operates in accordance with programming stored in a memory  152  and control signals received from control switches  106 . As seen in the Figure, the air hose  116  is connected to a pressure sensor  154  which generates an electrical signal indicative of the position of the foot pedal switch  118 . The microprocessor provides visual indication and prompts to the operator through indicators  104  and oral indications and prompts through a speaker  156 . 
     The primary purpose of the microprocessor  150  is to control the operation of a motor  158 . The motor receives control commands from the microprocessor  150  and in response activates a pump  160 . The pump  160  is coupled to a source or reservoir of liquid  162  and is capable of either dispensing the liquid from the reservoir to tube  108 , or, when reversed, it can withdraw liquid from the tube  108  into the reservoir  162 . The pump  160  and reservoir  162  can be implemented in many forms. For example, the pump  160  and reservoir  162  can be implemented as a syringe with a piston reciprocated by a rod coupled to motor  158 . 
     The elements shown in FIG. 2 can be disposed in housing  102 . Alternatively, at least some of the elements, including the motor  158 , reservoir  162  and pump  160  may be disposed in handle  110 , in which case the tube  108  may be replaced by an electrical connector. 
     Device  100  can be operated in several modes. The mode of operation is determined by the position of the knob  106 B. For one position of the knob, the device  100  operates in the same manner as the prior injection devices. In this mode the operation of the device  100  can be characterized as a manual or semiautomatic mode in which the device is operated in response to control signals from the clinician. This mode of operation is now described in conjunction with the flow chart of FIG.  3 . In step  200  the device is initialized. This step includes entering various operational parameters into memory  152 , loading the reservoir  162  with the appropriate liquid, purging the tube  108 , and needle  112 , etc. When the clinician is ready for the injection, he pushed a button, such as  106 B indicating that the start of the operation (step  202 ). Once the operation is started, the microprocessor  150  checks the position of the foot pedal switch  118  (step  204 ). If this switch is activated, as determined in step  206 , then in step  208 , the microprocessor  150  obtains the current position of the pedal switch  118 . For example, the switch could have an off position, a position 1 and a position 2. 
     At step  210  a check is performed to determine if the switch is in position 1. If it is then in step  212  the microprocessor  150  sets the motor  158  to operate at a first speed. The microprocessor  150  then returns to step  208  and gets the new position of the pedal switch  118 . 
     If in step  210  it is determined that the switch  118  is not in position 1 then in step  216  a check is performed to determine if the switch  118  is in position 2. If it is, then in step  216 , the microprocessor sets the motor  158  to operate at a second speed 2. In an alternate embodiment, the speed of the motor  158  can be set in these steps to be anywhere between a lower and an upper limit. For this embodiment, the switch  118  must be capable of having a variable position between positions 1 and 2. 
     If the switch is not in position 2 then in step  218  the microprocessor checks if the switch  118  is in the off position. If it is then in step  220  the motor  158  is stopped. In an alternate embodiment, under certain conditions, the motor  158  in step  220  may be reversed for a short time period to induce aspiration. In addition, a separate switch (not shown) may be provided which would cause the motor to reverse. In any event, in the mode shown in FIG. 3, the microprocessor  150  checks the position of the switch  118  and adjusts the operation of the motor  158  accordingly. 
     As discussed above, in some instances this mode of operation may be unsatisfactory. Therefore according to this invention, the device  158  could be operated in a cruise control mode. This mode can be selected by changing the position of know  106 A. In this mode, the device  100  operates as shown in a manner similar to the one shown in FIG. 3, with some exceptions. More particularly, in step  202 A when the device operation is started, the clinician is advised of the selected mode of operation (i.e., in this case, cruise control). This step is accomplished by generating an audio message through speaker  156 , a visual message on one of the displays, a combination audio/visual message or by other similar means. 
     In addition, after the requested motor is set in either of these steps, the microprocessor checks if an override switch is activated (step  222 ). This override switch can be set on the housing (see switch  106 B, on the foot pedal-switch  120 , on the handle-switch  124 , and so on. If in step  224  it is determined that the override switch has not been activated, then in step  226  the previous speed of the motor  158  is maintained. 
     The microprocessor  150  continues to check the position of the override switch at regular intervals and during this time the motor is maintained at the previously selected speed. Since during steps  222 ,  224 ,  226  the position of the pedal switch  118  is not checked, after step  212  the clinician can release the pedal switch and allow it to return to a neutral or off position. 
     After the override switch is activated (the override switch is preferably a momentary switch) the clinician can use the pedal switch  118  to generate a new control signal for the motor (i.e., speed 1, speed 2, off, etc.) 
     Alternatively, as shown in FIG. 5, the function of the override switch can be implemented by software. In this embodiment, after the speed of the motor is set (in steps  212 , or  216 ), this speed is confirmed in step  222 A. That is, an indication (either visual, oral, or both) is given to the clinician to indicate what is the current speed of the motor. This indication is a trigger or prompt to the clinician to release the pedal switch and allow it to return to the neutral or off position. Then in step  223  the position of the pedal switch is checked. In step  224  a determination made as to whether the pedal switch has been activated or moved from its off position. If the pedal switch is still in the off position, the motor speed is maintained in step  226 . If the pedal switch is reactivated, the microcomputer  150  returns to step  204 . 
     In the embodiments disclosed above a specific type of injection device is described that is operated by a clinician through a multi-position foot pedal switch. Of course, other types of control means or members may be used as well to obtain a similar functionality. For example, switches or other control elements for controlling the dispensing of the liquid may be provided on the housing or on the handle. 
     It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained, and since changes may be made without departing from the spirit and scope of the invention, it is understood that the above description is merely illustrative and does not otherwise limit the scope of the invention. The claims that follow define the inventive scope.