HK1037550B - Pressure/force computer controlled drug delivery system - Google Patents

Description

computer controlled pressure drug delivery system

The present invention relates to improvements in drug delivery, and in particular to a system (syringe) for subcutaneous infusion/aspiration for providing intermittent, occasional or limited drug delivery (relative to continuous drug delivery by a syringe pump). More particularly, the present invention relates to an improved subcutaneous drug (fluid) infusion and aspiration device providing a device and method for controlling and monitoring the interaction of specific flow rates and pressures during fluid infusion and aspiration with a hypodermic hollow needle.

Infusion pump devices and systems are well known in the medical arts for providing prescribed medications to patients. These devices may have a small pump housing, or have a larger stationary pump housing device. Infusion of prescribed drugs has been described in the literature, wherein a patient is injected with a drug through an infusion tube and associated catheter or the like, whereby the drug is introduced intravenously. These systems have been modified over time to determine if the injection line is blocked. A tube blockage will cause the pressure within the syringe to increase. Systems have been developed in the prior art for identifying a predetermined pressure threshold or for monitoring pressure to determine a means for selecting an occlusion pressure range to ensure patient safety. Us patents 5295967, 4731058, and 5080653 disclose systems (with syringe pumps or the like) that are adequate for the intended use of drug injections, and in particular are capable of monitoring for blockages during injections. However, these systems do not provide a means for injecting the drug subcutaneously through a hypodermic needle. Furthermore, these systems do not provide means for inhalation during drug injection, a medical requirement when performing hypodermic injections, in an attempt to avoid intravascular movement of the hypodermic needle.

Pain, tissue damage and post-operative complications have long been a side effect of using existing subcutaneous drug infusion systems. This is reported extensively in the dental and medical literature. Pain and tissue damage are a direct result of uncontrolled flow and excessive pressure generated within the tissue space during injection. It has been demonstrated that the subjective pain response of a patient at a particular flow rate can be minimized during drug infusion. Furthermore, it has been scientifically proven that a particular pressure (too great without itself obstructing) will cause damage to a particular type of tissue. It is therefore important to maintain a specific flow rate and a prescribed pressure range during drug infusion when performing subcutaneous injections in order to avoid subjective pain response and tissue damage. There is also a need for a system with pumping capability under controlled flow and pressure conditions to avoid the same side effects during fluid movement. One invention is disclosed in us patent 5180371, which is hereby incorporated by reference, wherein the flow of medicament may be set by a hypodermic needle. However, said invention does not disclose means for determining, checking or monitoring the pressure during the drug infusion.

During the period around 1980, several researchers { see, for example, hood: pressure resulting from poor bleb injection, ", British Dental j.144: 280-282 (1978); walton and Abbot: "periodontal line injection; clinical evaluation, "JADA" (oct.1981); smith and Walton: "periodontal line injection; distribution of injection solution, "Oral Surg 55: 232-238(1983) } earlier confirmed and concluded that the pressure generated by the injected fluid is important to avoid tissue destruction and painful responses. In addition, the different types of collagen and the density of the connective tissue cause different tissue compliances and expansions. These differences exist between patients and within individual patients. Hood in its 1978 article discusses that "when 2.0ml was injected, the relationship between the injected flow rate and the pressure rise, which is clearly seen in smaller volumes, disappeared. Several high pressures and some unexpectedly low pressures were recorded. There are many indications that there is tissue destruction and it can be said that the low pressure is caused by no more fluid being contained in the pterygomandical (pterygomandible) space when the injected dose is similar to the previously estimated volume of the tissue space ". Thus, it appears that there is no direct relationship between flow and pressure during interstitial injection.

Smith and Walton mentioned in the above-mentioned article that they performed histological animal (canine) studies using a technique aimed at correcting the hand pressure generated. They concluded that: "volume of injection and needle position are not always distribution dependent. Injection at moderate and high back pressure resulted in deeper and more extensive dye penetration. "this again demonstrates that pressure is an important variable for the distribution of the solution within the tissue, and that volume is not always related to the pressure generated.

Pashley, Nelson and Pashley use a pressure transducer in "pressure generated by dental injection" (J DentRes 1981) and the fixed flow rate generated by a conventional syringe driven by a motor clearly indicates that different tissues have different tissue compliances. Even at a fixed flow rate, the variability of the gap pressure is statistically and clinically important. Thus, it can be concluded that by using the measured flow, they produce large pressure variations.

Pertot and Dejou in their article "pressure effects during periodontal injection in dogs" (Oral Surg. Oral Med, Oral Pathol.1992) mention how they use a syringe connected to a miniature force sensor and found that there is a defined relationship between the number of osteoclasts and the force applied to the plunger of the syringe, which indicates that the pressure generated in the PDL space increases osteoclast activity. This experiment again shows that pressure is a major factor for tissue destruction and is dependent on the resistance encountered and independent of the flow of solution into the tissue.

One of the dental and medical goals should be to treat patients in the most humane and painless way. The purpose of any treatment is to produce the desired result without causing tissue destruction or pain to the patient. Accordingly, there is a great need in the medical field for an injection system that is substantially free of pain and tissue damage to the patient.

The present invention aims to minimize the subjective painful response and tissue damage of a patient caused by inappropriate pressure generated during the injection of a drug using a hypodermic needle.

It is another object of the present invention to provide these advantages using a variety of different drug sources, i.e., standard syringes and anesthetic cartridges (cartridges) or ampoules (carpule).

The present invention provides an electronic device for selectively infusing fluid into a patient or withdrawing fluid from a patient, comprising: a container for injecting or collecting the fluid; a fluid delivery system having a first end connected to the container and a second end for insertion into the patient; an electric drive mechanism arranged and constructed to apply a force in one of a first direction and a second direction within the container in response to a command, the first direction being a direction of fluid entry into the patient's body from the container through the fluid delivery system, the second direction being a direction of fluid withdrawal from the patient's body through the fluid delivery system; a detector coupled to one of the container, fluid delivery system and electric drive mechanism for detecting an internal parameter indicative of the force generated by the drive mechanism; and a controller connected to said detector and said electric drive mechanism, said controller including a calculator for calculating an inlet/outlet pressure at said second end based on said internal parameter and an internal resistance to said force within said container and said fluid delivery system, said controller generating said instructions to ensure that said inlet/outlet pressure does not exceed a predetermined level.

The present invention also provides an injection device for injecting fluid into human tissue, comprising: a fluid container for holding a fluid to be injected; a fluid delivery portion having a first end connected to the fluid container and a second end adapted for insertion into body tissue; a drive mechanism for generating an internal pressure within the fluid container in response to a command, thereby forcing the fluid to flow through the fluid delivery portion and out through the second end, the fluid having an outlet pressure at the second end; an input element for inputting a physical characteristic of at least one of the fluid, the fluid container, and the fluid delivery portion; a detector for detecting an internal parameter indicative of the internal pressure; and a controller receiving said physical characteristic and said internal parameter, said controller including a calculator for determining said outlet pressure based on said physical characteristic and said internal parameter, said controller generating said instructions to ensure that said outlet pressure does not exceed a predetermined level.

Known prior art attempts to measure the pressure within the syringe using a pressure sensor (see us patent 5295967). The main disadvantage of these systems is that they do not regulate the flow and pressure of the fluid in order to compensate for changes in resistance through the entire system, or changes in resistance to the outlet pressure. (Outlet pressure refers to the fluid pressure downstream of the needle tip in the patient). Furthermore, the prior art does not provide any means for determining the outlet pressure. The present invention includes a microprocessor-based system that measures the pressure or force generated outside of the tissue and then uses this measurement to accurately determine the corresponding outlet pressure. In other words, by using specific software, the system monitors the outlet pressure, thereby generating and maintaining a certain flow rate even when there is a change in the resistance of the system.

The present invention also provides a system that automatically compensates for the total resistance encountered within the system that has been demonstrated to affect flow and measured pressure. It is believed that this is the first system to provide an accurately determined flow rate and required pressure by taking into account the total system resistance. Without this capability, it is believed that the flow rates and outlet pressures and fluid characteristics for different replaceable components, including syringes, tubing, and needles of different sizes, cannot be accurately derived. The system is primarily characterized in that it uses sensors that generate feedback parameters to control and monitor pressure.

Briefly, a system for dispensing fluid by injecting fluid into a patient in accordance with the present invention includes mechanical components and an electrical controller. The mechanical components include a drive mechanism and a disposable portion that includes a fluid storage device, such as a syringe, ampoule, or the like, and a fluid delivery portion that includes a tubing connected to the fluid storage device and terminating in a needle for insertion into tissue to be injected. The drive mechanism includes a housing having an internal motor, and a securing portion for securing the fluid storage device to the housing. The fluid storage device includes a plunger that is movable back and forth. A linkage mechanism is used to move the plunger using the motor. It is important to use a sensor to detect the force or pressure generated by the motor and applied by the plunger within the fluid storage device. If an ampoule is used as the fluid storage device, an adapter is also provided to enable the same fixing device to fix the ampoule. The holding device is designed and constructed for holding syringes or ampoules of different sizes. The motor, the linkage mechanism connected to the motor, and an electronic controller to be described below are at least partially disposed within the housing to protect it.

An electrical controller is provided for controlling the overall operation of the system. The controller includes a master microprocessor provided as a standard stand-alone PC or as a portable PC, and an internal slave microprocessor for operating in response to instructions from the master microprocessor. The main microprocessor provides an interface with the physician and collects data about the mechanical device. The main microprocessor is also connected to a display device for providing instructions to the physician and an input device, which may be a keyboard, touch screen or voice activated device, for collecting information from the physician. The main microprocessor is also connected to a memory that stores a plurality of databases, each database being associated with one element of the disposable part and other parameters.

The fluid storage device is filled and a setup process is performed during which various operating parameters entered by the physician are calculated, retrieved or otherwise received. The physician also specifies the fluid flow rate and peak outlet pressure as well as the total amount of fluid to be injected. The physician then operates a pneumatic device, such as a foot pedal, to initiate fluid flow. In addition, the physician may issue instructions electronically or audibly. During injection, the output from the sensor is used to calculate the current outlet fluid pressure. If the outlet pressure approaches a threshold, the flow is automatically reduced, thereby preventing excessive outlet pressure, thereby ensuring that the patient is not overly painful and the tissue is not damaged. Several optional features are also provided, including pumping, purging, or filling the media with or without air.

Furthermore, the system may be operated in biopsy mode, where inlet pressure and output or extracted fluid flow rate are relevant control parameters.

The physician is constantly provided with visual or audible information about the current treatment status, including the current flow rate, total volume expelled or aspirated, outlet or inlet pressure, and other parameters throughout the procedure. The slave microprocessor receives instructions from the master microprocessor and generates the drive signals required to operate the motor.

FIG. 1 illustrates the major elements of the mechanical system of the present invention;

FIG. 2 is a perspective view of the drive mechanism;

FIG. 3 shows the main elements of the drive mechanism;

FIG. 4 shows how the elements of the drive mechanism of FIG. 3 are disposed in a housing;

FIG. 5A is a top view of the housing without the bracket;

FIG. 5B is a perspective view of the housing without the bracket;

FIG. 6 is a front view of a clamp for securing the syringe to the housing;

FIG. 7A is a top view of the platform 30 of FIG. 2;

FIG. 7B is a side view of the platform 30 of FIGS. 2 and 6;

FIG. 8 is a side view of a prior art fluid cartridge;

FIG. 9 is a schematic side view of an adapter using a cartridge with the system of FIGS. 1-7;

FIG. 10 is a block diagram of an electronic controller;

FIG. 11 is a general flow chart illustrating the operation of the controller of FIG. 10;

FIG. 12A depicts an exemplary display showing various possible selections of elements for the replaceable portion;

FIG. 12B is an exemplary display that collectively lists the operating characteristics and parameters of the current process;

FIG. 13 is an exemplary display shown to a physician during a setup process;

FIG. 14 schematically represents control signals derived from a foot pedal;

FIGS. 15A and 15B show graphs of fluid flow and outlet pressure, respectively, over time;

FIGS. 16A and 16B show fluid flow and outlet pressure over time when the pressure exceeds a threshold value;

fig. 17 is a flowchart of the inhalation operation;

FIG. 18 is a flow chart for charging a syringe;

FIG. 19 shows the syringe and associated equipment required for filling; and

FIG. 20 is a flow chart for determining the typical elements required to determine the outlet pressure.

The present invention relates to a system for delivering a drug, such as an anesthetic, or for providing a suction effect, such as for biopsy, which system is capable of ensuring that pain is minimized in an efficient manner. The system includes a mechanical device cooperating with an electronic controller.

The mechanical arrangement is illustrated in fig. 1-9 and the electronic controller is illustrated in fig. 10-18.

A drug delivery system 10 constructed in accordance with the present invention includes a drive mechanism 12, a delivery tube 14 and a handle 16 having a needle 17 at the distal end. More specifically, the syringe 90 (or other fluid storage device) is secured to the drive mechanism such that one end of the tube 14 is connected to the syringe 90. The drive mechanism 12 operates the syringe 94 to selectively expel fluid through the tube 14 and handle 16 and needle 17 or to aspirate fluid in the opposite direction. The drive mechanism 12 is connected to an external controller for selecting various operating parameters as described in detail below. The external control may be provided on the housing of the drive mechanism or may be connected to the drive mechanism 12 as a separate control device 18 via a cable 20. The control device 18 may be a PC or a portable computer, for example. Furthermore, the control device 18 may be internal.

Details of the drive mechanism 12 are described below with reference to fig. 2-5. Referring first to fig. 2, the drive mechanism 12 includes a housing 22 having a top surface 24 and an intermediate surface 26 disposed below the top surface 24. On the surface 26, a track 28 is formed, extending along the longitudinal axis of the housing 14. The platform 30, which is disposed on the rails 28, is movable back and forth parallel to the longitudinal axis, as will be described in more detail below.

On the top surface 24, as can be seen in detail in fig. 5A and 5B, two parallel elongated slots 32 and 34 are provided, and between these slots, a slot 36 is formed. The ends of each slot have laterally extending portions 38 facing each other. The slot 36 terminates adjacent the transverse slot 54.

The clamp 40 rides in the grooves 32, 34. As shown in fig. 6, the clamp 40 has a C-shaped body 42 terminating in legs 44 extending toward each other and a web 46. A bolt 48 having a head 50 extends through a threaded bore (not shown) in the connecting plate 46 and terminates in a pad 52.

The clip 40 is constructed and designed so that the feet 44 fit into the extensions 38 and cause the clip to ride horizontally in the slots 32, 34.

Platform 30 (see fig. 7A and 7B) is formed on top surface 58 with a groove 56, with a graduated key slot 60 on one side of groove 56.

Inside the housing 22, there is provided a motor 66 (fig. 3 and 4) which is held securely within the housing. The worm 72 passes through the motor 66. The worm 72 is arranged such that when the motor 66 is activated, the worm 72 moves in one direction or the other parallel to the longitudinal axis of the housing, depending on the direction of rotation of the motor. One end of the worm 72 is non-rotatably secured to a pad 74 and is connected to a platform 76. Between the platform 76 and the pad 74 is a load cell 78 arranged to transmit and measure forces between the pad 74 and the platform 76. The load cell 78 is bi-directional so that pressure and tension can be measured depending on whether the worm 72 is moving to the left or right as shown in fig. 3. Two short bars 80 are used to join the pad 74 and the platform 76 to prevent the transfer of rotational force generated by the motor 66 to the platform 76.

Two cylinders or rods 82, 84 extend between the platforms 30 and 76 and connect the two components together. These rods 82, 84 are slidably supported on the housing 22 by two pairs of bushings 68 and 70. With the exception of these bushings, the platforms 76 and 30 float inside and outside of the housing 22, respectively. Rods 82, 84 extend through walls 86, with walls 86 extending between surfaces 24 and 26 through apertures (not shown). The track 28 is hollow and aligned with the worm 72 such that the worm 72 moves along a longitudinal axis through the housing 22.

Generally, the syringe 90 has a barrel 92 positioned in the slot 36 such that its index finger tab 95A is positioned in the slot 54 (see FIG. 6). The syringe 90 also includes a plunger 94 that is moved within the barrel 92 by a shaft 93. The shaft 93 terminates at an index finger pad 96. When the syringe 90 is positioned in the slot 36, the index finger pad 96 is positioned in the slot 58 of the platform 30. In this position, the syringe 90 is secured to the housing 22 by inserting the feet 44 of the clip 40 into the slot extensions 38 and pushing the clip 40 on the syringe 90 to the left until it is at the end of the syringe body 92 adjacent the slot 4. In this position, screw 50 is tightened so that pad 52 is forward and engages cylinder 90. The slot 36 aids in positioning the syringe 90. The syringe terminates with a locking member 95 for connecting it to the tubing 14.

It should be appreciated that the motor 66, the pad 74, the load cell 80, the worm 72 and the platform 76 are all located within the housing 22. The platform 30 is located outside the housing 22. When the motor 66 is activated, as described below, it applies a force to the worm 72 causing the worm to move in a certain direction. The worm screws thus move the platforms 30, 76 and the rods 82, 84 in unison, thereby moving the plunger 94. The only elements that enter and exit the housing are rods 82 and 84. Thus, most of the major elements of the system are protected within the housing from contaminating or spilling the fluid. In addition, the drive mechanism 12 is adapted to operate syringes having a variety of diameters and lengths. Similarly, the delivery tube 14, handle 16 and needle 17 may have any desired dimensions.

In the embodiment discussed above, it is assumed that fluid is being injected from syringe 90, and therefore, syringe 90 must be pre-loaded with the fluid, which may be done by the manufacturer or filled in the field by a healthcare worker before initiating the procedure. However, in many processes it is more desirable to provide the fluid to be injected in a cartridge 100 as shown in fig. 8. As can be seen in fig. 8, the cartridge 100 is comprised of a cylindrical barrel 102. At one end of the cylinder 102 there is a flange 104 made of rubber or similar resilient material which can be reciprocated through the cylinder to selectively expel the liquid contained therein. At the opposite end of the cylinder, the cartridge has an opposite end formed by a membrane 106, which must be pierced before the medicament in the cartridge can be injected.

Fig. 9 shows an adapter 110 for allowing the driver of fig. 1-7 to inject fluid from the cartridge 100. The adapter 110 comprises a holder 112 adapted to hold the cartridge 100. The retainer 112 includes a first end having a connector 114 (e.g., a Luer connector) for connecting the adapter 110 and the delivery conduit 14. Inside the holder 112, adjacent to the connector 114, there is a spike 116 which is constructed and arranged to pierce the membrane 106 when the cartridge 100 is inserted into the holder 112. At the opposite end, the retainer 112 has a radially extending projection 118 for securing the retainer 112 to the drive mechanism 12. The above-described cartridge holder 112 is described in the 09/028009 patent application filed on 23/2/1998 entitled "dental anesthesia and delivery injection device", which is incorporated herein by reference.

The adapter 110 also includes a connecting member 118 formed of a shaft 120 having a barb or hook 121 at one end and a thumb pad 122 at the other end. The shaft 120 passes through a cap 124 that is adapted to be secured to the holder 112 by engagement of the protrusion 116 and a corresponding recess (not shown) in the cap 124. The cap 124 has tabs 126 that extend radially and have a shape approximating the index finger tabs 95A on a standard syringe 90.

To secure cartridge 100 to drive mechanism 12, cartridge 100 is first inserted into holder 112 from the rear end of holder 112. Once cartridge 100 is positioned within holder 112, shaft 120 is longitudinally aligned with the axis of holder 112, and the hook thereon is then inserted into piston 104 until securely engaged therewith. The cartridge 100 is then advanced toward the connector 114 such that the spike 116 pierces the membrane 106, thereby providing an outlet for the fluid therein. To ensure that fluid does not escape, the tubing 14 may first be installed on the connector 114, with the tubing 114 omitted from FIG. 9 for clarity.

Instead of hooks, the plunger 121A may be fixed to the shaft 120 in such a way that when the plunger is inserted into the holder 112, a vacuum/pressure connection is created between the plunger and the piston 104. As a result, longitudinal movement of the plunger in each direction causes the piston 104 to follow, thereby expelling or drawing fluid into the system.

The cap 124 is then connected to the holder 112 by pushing the protrusion 116 into the recess in the cap 124, thereby securing the cap to the holder 112. In this configuration, cartridge 100 and adapter 110 have a configuration similar to syringe 90 and thus may be mounted on the drive device of FIGS. 1-7 as a syringe, with clip 40 engaged with cap 124, tab 126 extending into slot 54, and thumb pad 122 engaged with slot 56 on platform 30. With the adapter 110 in this position, the motor 66 can be used to move the shaft 120 and piston 104 back and forth into and out of the cartridge 100, either through the hook 121 or through the plunger, thereby causing fluid to be expelled or drawn in as desired. The provision of a hook 121 (or plunger) formed at the end of the shaft 120 serves to ensure proper engagement and a secure mechanical coupling of the shaft 120 and piston 104, thereby ensuring that the piston 104 follows the movement of the shaft 120 and platform 30 in each direction.

Fig. 10 shows a block diagram of electronic controller 150. The controller 150 includes two microprocessors: a master microprocessor 152 and a slave microprocessor 154. The slave microprocessor 154 is used to derive signals for driving the motor 66 and to gather information about the platforms 30, 76.

The master microprocessor 152 is used to gather information about the rest of the system, including the syringe 90 and its contents, tubing 14, handle 16, etc., and to generate control signals for causing the slave microprocessor 154 to operate the motor 66 to deliver fluid from the syringe 90.

Physically, the slave microprocessor 154 and its associated circuitry are disposed within the housing 22. The main microprocessor 152 is included in the control device 18 which is connected to the housing 22 by the cable 20 shown in fig. 1.

As shown in fig. 10, microprocessor 152 is coupled to memory 160, input device 162, display device 164, and interface 164.

The memory 160 is used to store programs and data for the main microprocessor 152. More specifically, the memory 160 is used to store 6 or more data sets, each dedicated to the following information: (a) a syringe, (b) tubing, (c) a needle, (d) a fluid, (e) a control parameter, and (f) a profile made up of a plurality of parameters for a particular treatment to be performed. Each parameter is used to determine a control signal generated from the microprocessor 154. Each data set contains the appropriate parameters for a product available on the market or contains parametric data obtained by using a specific algorithm. Information about the various elements for a particular configuration is entered through the input device 102 and confirmed on the display device 164. These input devices may include a keyboard, touch screen, mouse, and microphone. If a microphone is included, the voice instructions are interpreted by voice recognition circuit 162A.

Display device 164 is also used to provide instructions and instructions for the operation of system 10. Instructions for operating the motor 66 are generated by the main microprocessor 152 and delivered to the interface 162. The microprocessor 152 also has a speaker 165 for providing various voice information, including pre-recorded or synthesized utterances (generated by the speech synthesis circuit 165A), harmonic tones, etc., for providing instructions to the physician and providing other information about the current status of the overall system and its components so that the physician need not always view the display.

These instructions are received from the microprocessor 154 via a cable or other connection and interface 170.

Also associated with the slave microprocessor 154 are one or more position detectors 172 and a chopper drive circuit 174. As previously described, the force between the platform 76 and the pad 74 is measured by the load cell 78. The load cell may be a model S400 load cell manufactured by SMD corporation of Meridien, Connecticut.

Also associated with the slave microprocessor 154 is a foot switch or foot pedal 176. Preferably, the foot pedal 176 includes an air chamber having flexible side walls arranged to vary the volume of air within the chamber in response to operator manipulation. A pressure sensor (not shown) is part of the foot pedal and is arranged to provide information about the pressure to the slave microprocessor 154 via a corresponding analogue to digital converter 190. This type of footrest is well known in the art and thus details thereof are omitted.

The sequence of operation of the system 10 is described below with reference to fig. 11. Beginning in step 300, the system is first set up. This step is performed by the host microprocessor 152 because it involves the exchange of information with the physician and the outside world.

Step 300 involves first having the physician enter the following information: the type of syringe used, the type of tubing 14 (i.e., size and length), the type of needle used, the name of the fluid in the syringe, or other identification. This information may be entered manually by the physician using an input device, for example using a keyboard or a touch screen provided in the screen. In addition, a plurality of corresponding items (e.g., syringes) may be retrieved from the database and displayed and then provided to the physician. The physician then selects the appropriate syringe using a standard pointing device such as a mouse or touch screen. In addition, voice instructions may be used to make this selection. Figure 12A shows an exemplary screen for specifying or selecting an injector. As can be seen from this screen, once the injector is selected or designated, its physical characteristics, such as length, nominal volume, stroke length, injection force, etc., are retrieved from the database and displayed. After the needle and fluid are specified, their characteristics are also retrieved and displayed.

Some information, such as the length of the pipe 14, must be manually entered because the system is difficult to determine. However, other information as well as various operating parameters are automatically determined. For example, the identification of the injector may be encoded as part of the injector information and read by the system. One desired parameter is the cross-sectional area a of the injector, as described below. This is determined by the length or stroke of the syringe divided by the volume.

Once information about the system components is entered, or other selections made, another screen is presented to the physician (fig. 12B). This screen is used to provide information to the physician or to enable the physician to enter certain parameters required to complete the setup.

The screen of FIG. 12B has 5 general areas designated 502, 504, 506, 508, and 510. In area 502 some basic information is provided or selected by the physician, including a profile specified for the current treatment, such as "periodontal ligament injection", and in area 504 the parameters in the screen of fig. 12A are repeated in a short format to represent syringe, needle, tubing and fluid information.

In region 506, the physician selects the type of procedure (e.g., injection) he needs, the level of flow, and the optimal pressure limit. As previously mentioned, this last parameter is very important because it controls the degree of pain and tissue destruction that the patient may experience during treatment. Additional parameters such as charge flow, suction heat capacity and flow, purge capacity and flow, etc. may also be selected in this region.

In region 508, the physician specifies the total amount to be injected, and whether (a) the syringe is filled, (b) with an air charge, or (c) without an air charge. The final field 510 is used to represent various parameters calculated from previously received or selected information, including system volume, maximum flow, maximum pressure, etc.

In one embodiment of the invention, the system, and in particular the main microprocessor 152, then uses these parameters to retrieve a profile from a profile database that determines the sequence and programming characteristics required for delivering fluid through the needle at the desired or optimal flow rate. For each particular syringe-tube-needle combination, the profile is calculated and stored in the memory described above. These profiles have unique characteristics for each type of treatment. For example, the profile for PDL (periodontal ligament) and the profile for the anterior subcutaneous anaesthetic injection are different. Only a unique set or family of profiles associated with a particular process is stored in the memory of the host microprocessor because other profiles are redundant.

In addition, the main microprocessor 152 may be programmed to perform the calculations required to generate the profile. However, it is desirable for most applications to compute a profile, a priori and programmed, and stored in a database, as described above.

After the setup process is complete, a test is made to determine whether the physician needs to fill syringe 90 with the relevant device, step 302. In many instances, it is contemplated that the practitioner will either manually preload the syringe or use a pre-filled syringe or cartridge. If the injector is loaded or attributed to the device, the master microprocessor 152 issues a command to the slave microprocessor 154 to move the platform to the initial position at step 304.

Referring to fig. 10, microprocessor 154 is connected to load cell 78 through a/D converter 83, RAM182, EEPROM184, and limit switch 172. The slave microprocessor 154 controls the operation of the motor 66 using information obtained from these elements, the functions of which are described in detail below, and in response to instructions from the master microprocessor 152 via the interface 170. More specifically, the slave microprocessor 154 operates the chopper drive circuit 188 to generate step pulses that are provided to the motor 66 to rotate the motor 66 in one of two directions at discrete angular increments. The frequency of these pulses determines the speed of the motor. For high flow, low flow purging, inhalation or charging, separate velocities may be used. The physician selects the values for these speed parameters and the microprocessor then calculates the speed (i.e., step frequency) of the corresponding motor using the dimensions of the syringe and fluid delivery system.

The microprocessor 154 maintains the position of the tracking platforms 30, 76 by counting the number of steps the motor 66 rotates. In addition, other detector switches may be provided for detecting or verifying the position of the platform, such as several positions of the platform 76 along its path of travel. In a preferred embodiment, at least one detector switch is provided for defining an initial position of the platform 76. All other positions of platform 76 are calculated from the initial position. For example, the initial position may be the leftmost position shown in fig. 4.

The motor 66 is preferably made of a rare earth permanent magnet so as to have a small volume but a large torque.

Returning to FIG. 11, in step 304, microprocessor 152 sends an instruction instructing microprocessor 154 to move platform 76 to the initial position. One instruction table of all this type is stored in the memory 160 as part of the control database. The microprocessor 154 activates the motor until the platform 76 reaches the initial position and this position is verified by the output of the detector 172 and reported to the microprocessor 152. Next, in step 306, microprocessor 152 commands platform 76 to move toward the initial position. The initial position is a function of the selected syringe and the amount of fluid contained in the syringe and is determined by a profile stored in a profile database.

The system 10 is now ready to receive a syringe filled with medication. Fig. 13 shows an exemplary screen on screen 164, which may be displayed to the physician at this time. The display includes several soft or programmed buttons that can be activated by the physician for issuing certain instructions, and several display areas in which information is provided to the physician. In this particular example, the display represents the following buttons referenced 198: quit, print, pedal. In other examples, other buttons may be represented.

Further, the display of fig. 13 includes the following information areas: an information area 200 in which instructions are provided for the next step; or display information to inform the physician of the currently performed processing step; two profiles 202, 204, where flow and outlet pressure are displayed in terms of time, syringe icon 206, pressure gauge 208, which represents the current outlet pressure (another parameter generated as part of the profile) in percent of the maximum allowable pressure, and another set of meters, indicated by reference numeral 210, representing the following parameters: the position of the platform 76 (and thus the plunger within the syringe) relative to the initial position in inches, the volume of fluid injected (or the volume of fluid collected in the case of a biopsy), the current flow rate in cc/sec, the current pressure (psi), the force applied and the force applied by the foot switch 176. Beginning at step 306, the display areas 202, 204, 208, and 210 indicate that the corresponding values have no value, and the icon 206 has an indication 212 that no syringe has been checked. Display 200 represents a message instructing the physician to load injector 90 and depress pedal 176.

The practitioner can now take a filled syringe and place the syringe in the slot 36 using the index finger tab 95A extending into the slot 54 and the thumb tab 96 inserted into the slot 56 of the platform 30. As previously described, the motor 66 has moved the platforms 76, 30 to the initial position. The initial position is defined as the position in which the filled syringe 90 can be secured by fitting its thumb pad 96 into the groove 56. It should be noted that in any other location, the system will not receive a syringe. In effect, the use of software ensures that the correct syringe with the correct amount of fluid is loaded so that any other syringe is not mis-loaded.

At step 310, the system waits for a syringe to be installed. The physician may indicate that the syringe is mounted by temporarily activating the foot pedal 176 or by activating the pedal button 198 on the screen. When a pedal signal is detected, a drug infusion may be performed. The red stop symbol 212 is first turned off. In step 312, the system checks whether the physician requires cleaning. If so, a purge is performed in step 313, during which time the drug delivery system is debubbled. The volumes of the needle, handle and tubing are known and therefore the volume of fluid to be cleaned is easily calculated.

As mentioned above, the foot switch 176 preferably includes a bellows and air pressure sensor (not shown). The output of the air pressure sensor is sent to the a/D converter 190 and the digital signal output from the pedal switch is sent to the microprocessor 154. The microprocessor 154 uses this detector and a look-up table stored in the EEPROM184 to determine or generate a switch indication signal indicative of the position of the switch. It has been found that for best response and sensitivity, the position of the switch is converted into 4 different positions or states using hysteresis. In other words, as shown in fig. 14, the switch is initially in an idle state. As the switch is depressed, its initial pressure increases. When it reaches a first value, ON1, the microprocessor 154 generates a low flow instruction. If the pressure increases but does not exceed the value of ON2, the low flow command is maintained. If the pressure decreases below the value OFF1, an idle state is displayed. The typical pressure OFF1 is lower than ON 1. If the pressure exceeds ON2, a high flow command is generated. The high flow command is not turned OFF until the pressure drops below the pressure value OFF2, which is OFF2 below ON 2.

Returning to FIG. 11, after cleaning, the position or state of the pedal 176 is determined in step 314. If a low flow command is received, the medication is injected at a low flow. If a high flow command is received, the drug is injected at a high flow. The actual values of the high and low flows have been set in advance as described above.

Once the pedal is depressed, the motor is activated and operates at a predetermined flow rate corresponding to the desired flow rate (step 316). A typical drug delivery is shown in fig. 15A and 15B, which would occur in regions 202 and 204, respectively. As can be seen from these figures, at T0 the flow rises fairly quickly to a first value LOW and then stops at a constant value. The outlet pressure begins to rise according to a certain law determined by the resistance of the tissue to fluid flow or other factors. At time T1, the pedal is actuated to a higher value HIGH and the flow rate rises to this new value. The outlet pressure continues to rise. At time T2, the pedal is released back to the lower value LOW. As processing continues, the microprocessor 152 continues to monitor the various pressure parameters (step 318), and it accumulates the total injection volume and compares the current injection volume to the total required injection volume (step 320). If the total shot size has not been reached, a check is made to determine if the pedal 176 is still depressed in step 322. If so, step 314 is repeated. If not, inhalation is deemed to be required and the inhalation sequence described below in connection with FIG. 17 is executed.

At step 318, the current pressure indicated by the load cell is checked against a threshold value for peak pressure that is safe for the system. This pressure value depends on the chosen component of the system. In addition, the outlet pressure value is also monitored 318. As mentioned above, it has been found that fluid pressure during injection plays a very important role in the degree of pain felt by the patient and the degree of tissue destruction. At low pressure values, pain is minimal and the patient is most comfortable. However, if the pressure increases beyond a certain value, the injection becomes very painful. Therefore, an important consideration in the present invention is to control the flow rate in such a way as to ensure that a low outlet pressure value is maintained.

More specifically, if the pressure (i.e., the pressure within the system or the outlet pressure) is found to be excessive at step 318, the flow is reduced at step 324. At step 326, the pressure is checked. If the pressure is still too high, the flow is again reduced in step 324. If the flow is acceptable, the flow is maintained in step 328 and the process continues in step 320.

The flow rate and various other parameters are displayed to the physician on a display as shown in fig. 13 so that the physician can very easily see the procedure. As shown in fig. 16A and 16B, at TX, it is entirely possible to cause pressure increase due to occlusion or needle encountering bone. When abnormal pressure is detected, a visual and audible alarm is provided. It is therefore desirable for the physician to take certain measures to counter the high pressures. However, if the occlusion continues and the pressure remains increasing, the flow is gradually reduced until it completely stops, as shown in FIG. 16A.

Returning to step 320, when the specified volume is reached, or the physician issues a stop command, the end subroutine is executed in step 330. During the subroutine, the syringe plunger stops moving forward and displays a message to the physician to pull the needle out. The physician may withdraw the needle, disconnect the tubing 14 from the syringe 90, and discard the tubing 14 and handle 16 and needle 17. Optionally, the aspiration subroutine discussed below may also be performed to ensure that fluid in needle 17 does not spill out.

In many cases, inhalation is required during drug delivery. For example, to deliver an anesthetic, aspiration is required after the needle is inserted in order to check whether the needle tip is placed in a blood vessel. In this case, the suction causes some blood to be drawn from the blood vessel. The blood is visible in the handle 16 or the hub of the needle 17.

It can be seen from fig. 11 that if the pedal is found to be released in step 322, the inhalation subroutine shown in fig. 17 is initiated.

More specifically, a check is made at step 400 to determine whether the plunger 94 in the syringe 90 is stopped. If not, a check is made to determine if the plunger is moving at a low speed in step 402. If so, a low speed stop routine is executed in step 404 to slow down and stop the motor.

A check is made in step 408 to determine if there is sufficient distance to inhale. Referring to fig. 3, at the time of receipt of an inhalation command, the plunger 94 may be in its rightmost position such that further retraction thereof from the syringe may cause dislodgement. Obviously this situation is undesirable. Accordingly, a check is made at step 408 to determine if it is safe to perform an aspiration without dislodging the plunger, based on the position of the plunger and the length of the syringe. If not, the process is stopped and an error message is displayed to the physician in step 410 indicating that it is not safe to inhale at that time.

Otherwise, the motor is reversed at step 412 and operated in the reverse direction for a predetermined time to retract the plunger. After the plunger moves a predetermined distance, it is stopped (step 414). The plunger then moves forward again (step 416) until it returns to its original position at step 408. The motor is then stopped (step 418). Steps 416 and 418 may be omitted if aspiration is performed at the end of the treatment when the needle is withdrawn from the tissue. In this manner, the system is used to deliver anesthetic for a particular treatment. For example, if the treatment is periodontal ligation, the following parameters may be used:

syringe type dental cartridge

Syringe size 1.8cc

Pharmaceutical local anesthetics (lidocaine HCI 2%, and epinephrine)

(epinephrene)1∶100,000)

Specific gravity of the medicine is 0.0361

Inner diameter of the pipe is 0.015in

Pipe length 60in

Needle type BD 30G1/2

The length of the needle is 0.5in

Needle head inner diameter 0.006in

Low speed 0.0059cc/sec

High speed 0.370cc/sec

Maximum pressure 250psi

When the same fluid is manually injected using a standard syringe and needle of the above dimensions, the outlet pressure produced is found to be as high as 660psi or higher.

For other treatments, different syringes, medications, tubing, and needles were selected.

As mentioned above, an important parameter to monitor using the system is the fluid outlet pressure at the needle tip, i.e. the pressure within the tissue as fluid flows out of the needle. This is the pressure represented by fig. 15A and 16A. However, this pressure is very difficult to measure directly. Therefore, in the present invention, direct measurement is not employed, but indirect measurement is employed. More specifically, the desired outlet or needle pressure Pn is derived from the force represented by element 78 and the physical characteristics of the system. More specifically, it has been found that during steady state (i.e. when the plunger is moving at a constant velocity) the outlet pressure can be expressed as follows:

pn ═ Ps-dVhn + dVh1-d (F1+ Ft + Fn) wherein

Ps is the pressure at the interface of the plunger and the fluid due to the motion of the plunger;

vhn is the velocity head in the needle;

vh1 is the velocity head in the injector;

d is the specific gravity of the fluid; and

f1, Ft and Fn are frictional losses due to flow in the syringe, tubing and needle, respectively.

There are some other minor pressure losses in the system, less than 1%, which are negligible.

The friction loss may be determined empirically and stored as part of a profile for each element of the system. For example, it has been found that the values of F1, Ft and Fn are:

f1 ═ 0.1%; ft is 89%; fn is 11% (total head loss).

The density of the fluid is known and is typically close to that of water.

The velocity head is calculated using the following equation:

Vh1＝α*Q²d/[(π/4)²D⁴(2g)]

where α is the kinetic energy coefficient related to Reynolds number, which is 2 for laminar flow;

q is the flow rate, as shown in FIGS. 15A and 16A;

g is the gravitational constant; and

d is the inner diameter of the element, i.e. the inner diameter of the syringe for Vh1 and the needle for Vhn.

When the speed of the motor increases or decreases, a factor relating to the acceleration must also be added. The coefficient is represented by:

ms a/As + Mt a/At + Mn a/An wherein Ms, Mt and Mn are the mass of fluid in the syringe, tubing and needle, respectively, and As, At, and An are the corresponding cross-sectional areas.

The procedure for determining the outlet pressure (designated "needle pressure" in the program listing) is appended to the end of this description. As can be seen from the described procedure and the flow chart of fig. 20, in order to calculate the outlet pressure, the respective friction losses in the 3 (syringe, tubing and needle) elements were first determined as follows. The reynolds number is determined at step 700 from the flow rate, element diameter and velocity. If the Reynolds number exceeds 2000 (indicating turbulent flow) then the kinetic energy coefficient is set to 1 in step 702 and the Reynolds number is used to calculate the friction loss in step 704.

If R < 2000, the kinetic energy coefficient is set to 2 in step 706 and the friction loss is calculated using a different formula in step 706. (depending on the viscosity and flow rate of the fluid and the diameter of the element). In the absence of flow, the friction loss and kinetic energy coefficient are set to 0 (708). Next, when the parameters are calculated from all of the elements, the flow loss for each element is calculated, the force of the actuator is calculated, and the outlet pressure or needle pressure is obtained using all of these parameters (step 712).

Each time the microprocessor 152 checks the pressure (step 318 of FIG. 11), the outlet pressure or needle pressure described above is actually calculated. Fig. 16B and 17B show a normal pressure curve and an abnormal pressure curve obtained using these formulas, respectively.

Returning to step 302 of fig. 11, if the device is to be used to charge a syringe, the charge subroutine shown in fig. 18 is initiated. At step 600, the platform 30 is moved to its original position. At step 602, a test is made to determine if the syringe is filled with air and if so, the platform 30 is positioned at step 604 so that the syringe head is in a fully filled position. In step 606, the system waits for the syringe to be set.

To fill a syringe, the system must be connected to a fluid source, such as a vial. More specifically, as shown in fig. 19, for filling, the syringe is connected to the conduit 14 through a three-way valve 700. Valve 700 is adapted to be connected to a fluid source 702 via a conduit 706. To fill a syringe, the valve is set so that the fluid source 702 is connected to the syringe. In fig. 19, the fluid source 701 is inverted such that it has an air space 706. To fill in the presence of air, the syringe plunger 94 is positioned as if the syringe had been filled, i.e., in the position shown in fig. 19. To fill without air, the syringe plunger is moved as close as possible to 94A at the opposite end. Once the connection is made as shown in FIG. 19, the practitioner can secure the syringe in the channel 38 and using the clamp 40 to secure it with the plunger head engaged with the platform 30.

Returning to FIG. 18, the syringe is tested in step 606. The syringe is advanced 608 to an empty position, forcing air into the source 702, thereby pressurizing the medication. In step 601, the plunger is retracted to an initial position corresponding to the amount of drug to be injected previously set by the physician. At step 612, the physician opens the valve 700, thereby connecting the syringe 90 to the conduit 14. The system now returns to step 308.

If it is determined in step 602 that there is no air charge, the platform 30 is moved in step 604 to a syringe empty position. The system then waits 616 for the syringe to be placed in its position, after which the system continues 610 as shown.

The system has thus far been described in terms of an injection process. It will be apparent, however, to those skilled in the art that the system may be used equally effectively for biopsy, such as for spinal cord puncture or other similar anesthetic procedures. Essentially the same parameters can be used for this process with only minor modifications. For example, instead of defining the outlet pressure, the physician now defines the inlet pressure. Some sub-procedures, such as washing, filling or aspiration, are not required at all for biopsy.

Obviously, many modifications may be made without departing from the scope of the invention.

Program listing

us math, Sys Utils; typeT Pressure-Record FlowRate: a single; // Cubic Inches/second (input) mechanismForce: a single; // Pounds (DB) { machine Resistanccd } LoadCellForce: a single; // Pounds (input) SyringeForce: a single; // Pounds (DB) Syringeddiameter: a single; // Inches (input) SyringeLength: a single; // Inches (DB) Tubingdiameter: a single; // Inches (DB) TubingLength: a single; // Inches (DB) NeedleDiameter: a single; // Inches (DB) needleLength: a single; // Inches (DB) specific weight: a single; // Slugs/Cubic Inch (DB) Viscosity: a single; the// No Units (DB) DB indicates that the value of the parameter is retrieved from one of the databases. Input indicates that the parameters are calculated in advance. The called represents the value Calculated by this routine. End;

the following variables are defined in this process:

  VelocityLast：single；  TimeLast：double；implementationfunction CalculatePressure(P：TPressure)：single；const  KineticEnergyFactor＝2.0；  Gravity＝386.4；var  KineticEnergyFactorSyringe：single；  KineticEnergyFactorNeedle：single；  KineticEnergyFactorTubing：single；  SyringeFrictionLoss：single；  SyringeFlowLoss：single；  SyringeVelocityHead：single；  NeedleFrictionLoss：single；  NeedleFlowLoss：single；  NeedleVelocityHead：single；  TubingFrictionLoss：single；  TubingFlowLoss：single；<dp n="d23"/>  VelocityConstant：single；  StopperForce：single；  ReynoldsSyringe：single；  ReynoldsTubing：single；  ReynoldsNeedle：single；  NeedlePressure：single；//Value returned  Volume，Accel：single；  VelocityNow：single；  TimeNow：double；begin  VelocityConstant：＝P.SpecificWeight  /                      (Sqr(PI/4.0)*2.0*Gravity)；  try    ReynoldsSyringe：＝P.Flowrate/(PI*P.SyringeDiameter*(P.Viscosity/4))；    if ReynoldsSyringe＞＝2000.0 then begin      KineticEnergyFactorSyringe：＝1.0；      SyringeFrictionLoss：＝0.25/sqr(log10(0.0000012/(3.7*P.SyringeDiameter)+                             (5.74/power(ReynoldsSyringe，0.9))))；    end else begin      KineticEnergyFactorSyringe：＝2.0；<dp n="d24"/>      SyringeFrictionLoss：＝(16*P.Viscosity*PI*P.SyringeDiameter)/                             P.Flowrate      end；　　except　　  SyringeFrictionLoss：＝0；　　  KineticEnergyFactorSyringe：＝0；　　end；　　try　　  ReynoldsTubing：＝P.Flowrate/(PI*P.TubingDiameter*(P.Viscosity/4))；　　if ReynoldsTubing＞＝2000.0 then begin　　  KineticEnergyFactorTubing：＝1.0；　　  TubingFrictionLoss：＝0.25/sqr(log10(0.0000012/(3.7*P.TubingDiameter)+　　                        (5.74/Power(ReynoldsTubing，0.9))))；　　end else begin　　  KineticEnergyFactorTubing：＝2.0；　　  TubingFrictionLoss：＝(16*P.Viscosity*PI*P.TubingDiameter)/　　                        P.Flowrate　　end；  except<dp n="d25"/>　　TubingFrictionLoss：＝0；　　KineticEnergyFactorTubing：＝0；  end；  try　　ReynoldsNeedle：＝P.Flowrate/(PI*P.NeedleDiameter*(P.Viscosity/4))；　　if ReynoldsNeedle＞＝2000.0 then begin　　KineticEnergyFactorNeedle：＝1.0；　　NeedleFrictionLoss：＝0.25/sqr(log10(0.0000012/(3.7*P.NeedleDiameter)+　　                      (5.74/Power(ReynoldsNeedle，0.9))))；　　end else begin　　  KineticEnergyFactorNeedle：＝2.0；　　  NeedleFrictionLoss：＝(16*P.Viscosity*PI*P.NeedleDiameter)/　　                        P.Flowrate　　end；　　except　　  NeedleFrictionLoss：＝0；　　  KineticEnergyFactorNeedle：＝0；　　end；<dp n="d26"/>  Volume：＝((PI/4)*sqr(P.SyringeDiameter)*P.SyringeLength)+　　        ((PI/4)*sqr(P.TubingDiameter)*P.TubingLength)+　　        ((PI/4)*sqr(P.NeedleDiameter)*P.NeedleLength)；  VelocityNow：＝P.FlowRate/((PI/4)*Sqr(P.SyringeDiameter))；  TimeNow：＝now*24*60*60；  if(TimeLast＞0)and(not P.TestMode)then begin     //First time entered switch　　Accel：＝((P.SpecificWeight*Volume)/Gravity)*　　 //ABS 　　         ((VelocityLast-VelocityNow)/(TimeNow-TimeLast))；  end else begin　　Accel：＝0；  end；  VelocityLast：＝VelocityNow；//Savefor next tme  TimeLast：＝TimeNow；<dp n="d27"/>  NeedleVelocityHead：＝(VelocityConstant*KineticEnergyFactorNeedle)*　　                    (Sqr(P.FlowRate)/Power(P.NeedleDiameter，4.0))；  SyringeVelocityHead：＝(VelocityConstant*KineticEnergyFactorSyringe)*　　                     (Sqr(P.FlowRate)/Power(P.SyringeDiameter，4.0))；  SyringeFlowLoss：＝(SyringeFrictiorLoss*P.SyringeLength*Sqr(P.FlowRate))/　　                 (P.SyringeDiameter*2.0*Gravity*　　                 Sqr(PI*Sqr(P.SyringeDiameter)/4.0))  TubingFlowLoss：＝(TubingFrictionLoss*P.TubingLength*Sqr(P.FlowRate))/　　                (P.TubingDiameter*2.0*Gravity*　　                Sqr(PI*Sqr(P.TubingDiameter)/4.0))；  NeedleFlowLoss：＝(NeedleFrictionLoss*P.NeedleLength*Sqr(P.FlowRate))/　　                (P.NeedleDiameter*2.0*Gravity*　　                Sqr(PI*Sqr(P.NeedleDiameter)/4.0))；<dp n="d28"/>  StopperForce：＝P.LoadCellForce-P.SyringeForce-P.MechanismForce；  //StopperForce：＝P.LoadCellForce；  NeedlePressure：＝(StopperForce/(PI*sqr(P.SyringeDiameter/2)))-　　                  NeedleVelocityHead+SyringeVelocityHead　　                  (P.SpecificWeight*(SyringeFlowLoss+　　                  TubingFlowLoss+NeedleFlowLoss)-　　                  (Accel/(PI*sqr(P.SyringeDiameter/2))))；end.

Claims (16)

1. An electronic device for selectively infusing fluid into a patient or withdrawing fluid from a patient, comprising:

a container for injecting or collecting the fluid;

a fluid delivery system having a first end connected to the container and a second end for insertion into the patient;

an electric drive mechanism arranged and constructed to apply a force in one of a first direction and a second direction within the container in response to a command, the first direction being a direction of fluid entry into the patient's body from the container through the fluid delivery system, the second direction being a direction of fluid withdrawal from the patient's body through the fluid delivery system;

a detector coupled to one of the container, fluid delivery system and electric drive mechanism for detecting an internal parameter indicative of the force generated by the drive mechanism; and

a controller connected to said detector and said electric drive mechanism, said controller including a calculator for calculating an inlet/outlet pressure at said second end based on said internal parameter and an internal resistance to said force within said container and said fluid delivery system, said controller generating said instructions to ensure that said inlet/outlet pressure does not exceed a predetermined level.

2. The apparatus of claim 1, wherein the controller comprises a comparator for comparing the inlet/outlet pressure to a predetermined threshold value.

3. The apparatus of claim 2, wherein the predetermined threshold value is selected in accordance with a pressure value that has been determined to minimize pain and tissue damage in the patient.

4. The apparatus of claim 1, further comprising a memory for storing physical characteristics of the fluid delivery system and the container, and wherein the calculator is for determining the outlet/inlet pressure based on the physical characteristics.

5. The apparatus of claim 4, wherein the memory is further configured to store a fluid characteristic of the fluid, and wherein the calculator is configured to generate the outlet/inlet pressure based on the fluid characteristic.

6. The apparatus of claim 1, wherein the container and the fluid delivery system are replaceable.

7. An injection device for injecting fluid into human tissue, comprising:

a fluid container for holding a fluid to be injected;

a fluid delivery portion having a first end connected to the fluid container and a second end adapted for insertion into body tissue;

a drive mechanism for generating an internal pressure within the fluid container in response to a command, thereby forcing the fluid to flow through the fluid delivery portion and out through the second end, the fluid having an outlet pressure at the second end;

an input element for inputting a physical characteristic of at least one of the fluid, the fluid container, and the fluid delivery portion;

a detector for detecting an internal parameter indicative of the internal pressure; and

a controller receiving said physical characteristic and said internal parameter, said controller including a calculator for determining said outlet pressure based on said physical characteristic and said internal parameter, said controller generating said instructions to ensure that said outlet pressure does not exceed a predetermined level.

8. The injection device of claim 7, wherein the controller comprises a master microprocessor for processing the physical characteristic and generating the instructions, and a slave microprocessor controlled by the master microprocessor.

9. An injection device according to claim 8, wherein the drive mechanism comprises a motor controlled by the slave microprocessor and a coupling means for coupling the motor to the container.

10. The injection device of claim 9, wherein the detector is disposed within the connection component.

11. The injection device of claim 9, wherein the motor and the slave microprocessor are disposed within a single housing.

12. The injection device of claim 7, further comprising a housing for the drive mechanism.

13. The injection device of claim 12, further comprising a securing portion for securing the container to the housing.

14. The injection device of claim 13, further comprising a detector for detecting when the container is positioned, and the controller generates instructions upon detecting the container.

15. The injection device of claim 12, wherein the container is a syringe having a barrel and a plunger that reciprocates within the barrel, and wherein the drive mechanism is coupled to the plunger.

16. The injection device of claim 12, wherein the container is an ampoule having a side wall and a detent, and wherein the drive mechanism comprises an adapter having a component connected to the detent.