In medical, surgical, dental, and other fields (e.g., endodontics, periodontics, personal hygiene), fluid is delivered to intended treatment sites using standard manual syringes at desired flow rates. While such delivery can be simple and effective, undesired effects, including hand fatigue, inconsistent flow, and unsafe high positive pressure at a treatment site can occur. Also, reliance upon disposable standard manual syringes generates waste, requires more storage space, and increases cost. Furthermore, syringes either need to be purchased prefilled, or an operator manually fills the syringes with medicaments before use, adding time to procedures and generating waste. There also are increased safety risks with the traditional syringe, including the introduction of air bubbles into delivery and unregulated flow rate.
Powered syringes in a handheld device can deliver small, metered doses of a medicament. Powered desktop pumping units can infuse fluids into a recipient over an extended time. Neither type of powered device exists in a small, simple to use, and convenient package with a wide range of chemical compatibility, and neither type of device can deliver variable fluid volumes over short time periods. Both also typically require a traditional syringe to be attached instead of self priming and drawing fluid from a reservoir.
The present invention provides an economical, ergonomic, lightweight, compact, cordless, convenient, easy-to-use, automated device for dispensing and delivering a multitude of fluids at a constant, consistent flow rate to a treatment site in, e.g., medical, surgical, and dental applications without the need for a traditional syringe. For dental applications, suitably deliverable fluids include, without limitation, sodium hypochlorite, ethylenediaminetetraacetic acid (EDTA), chlorhexidine based solutions, oral rinses, saline, alcohols, air and other common dental fluids. For medical applications, the device may incorporate a medicinal cartridge for injection, pump insulin or other medications, or precision delivery of medicament, aggregates, adhesives, or other substrates used during diagnostic, treatment, or reconstructive procedures.
The device generally includes, in a housing configured to be comfortably and stably held by the operator, at least one internal fluid line that connects a quick-connect fluid source and a treatment tip or needle that meets the various dimensional constraints and flow rate requirements of distinct treatment sites. At least one fluid pump in fluid connection with the at least one internal fluid line is dimensionally, directionally, and positionally configured to directly or indirectly urge fluid from the fluid source to the treatment tip. The fluid source is designed in such a way that air bubbles are controlled and that fluid can be drawn in any spatial orientation of the device. The at least one pump is electronically controlled, is powered by an on-board power source, and meets the size, power, pressure, and flow rate requirements of the device and the application. The targeted flow rate for this device is at least 4 mL/min irrespective of the gauge of the needle, but this may range from 0.5 mL/min to 10 mL/min for endodontic procedures or medicinal delivery, or it may be increased above 10 mL/min, up to 100 mL/min, for periodontal cleaning procedures. The power source provides power output sufficiently high to ensure that the at least one fluid pump operates at suitable drive parameters (including but not limited to voltage, duty cycle, frequency, current, rise and fall time, and other defining waveform characteristics) to provide for the desired fluid flow rate. User-actuated control circuitry is in electronic connection with the fluid pump(s). User-actuated switches or other structures for activating and deactivating the device, for adjusting drive parameters to the pump (and, thus, the flow rate), and for monitoring operational parameters can be provided on the device housing, remote from the housing, or in other ways known in the art.
As seen in
The power source 36 can include at least one single use (primary) or rechargeable battery or super capacitor 36 capable of supplying continuous output power of at least 0.2 W during operation for at least about 20 minutes of use. The battery can be removable and replaceable. The battery can be lithium ion, nickel cadmium, alkaline or the like and is preferably a single cell rechargeable lithium ion battery. A rechargeable battery or super capacitor can be rechargeable by direct electrical contact charging or by induction charging.
The fluid source 22, here a reservoir preferably having a sealable fluid outlet connector, is in direct or indirect fluid communication with the fittings 18 and 34, and with the treatment tip 20 via one or more internal fluid lines 32. The fluid source 22 can connect to the fluid line 32 via a fluid source connector 34, and can, as needed, be detached, reattached, replaced, and/or interchanged with another fluid source. The fluid source connector 34 can be, without limitation, a threaded, Luer lock, quick-connect, or similar fitting known to a skilled artisan. The fluid source 22, fluid line 32, tips 20, fittings, and any other fluid-contacting element should be chemically compatible with the fluid(s).
At least one fluid pump 38, also in electrical communication with the control circuitry 30, is interposed in the one or more fluid lines 32. The at least one pump 38 is advantageously self-priming, compact, and quiet, and has low operational power consumption requirements, typically between about 0.1 W and 2 W, preferably less than 500 mW. Desired run time to be an effective product is at least 30 minutes but up to 2 hours from a single charge of the rechargeable battery. For a 500 mW power consumption, this would require a minimum 250 mAh battery for 30 minutes of use and up to a 1 Ah battery for 2 hours of use. If a single pump provides inadequate flow rate or fails to overcome back pressure encountered at the treatment tip 20, a plurality of pumps 38 can be provided, as discussed in greater detail below and as shown in the figures. The at least one pump can be a piezoelectric pump or an electric (DC) motor pump such as a peristaltic or diaphragm pump.
Piezoelectric pumps operate using a piezoelectric diaphragm in combination with passive check valves. A piezo ceramic mounted on a membrane is deformed when voltage is applied. The deformation causes displacement of the medium, liquid or gas, within the pump chamber. The check valves cause the medium to always be drawn in from one end, and expelled from the other, so that flow is created in the desired direction. Some of the advantages to a piezoelectric pump include low power consumption, small size, reliability of priming and prevention of occluding, and availability at an economically viable price, although they may be limited by flow and pressure capabilities. The piezo crystal responds to an AC voltage with the maximum and minimum of the waveform causing the crystal to displace in both “up” and “down” direction from its steady state position. The drive may be specific to the pump manufacturer, though a typical drive would be 100-400 Volts peak-to-peak waveform operating at 20-1000 Hz. The type of electrical waveform may be, but is not limited to, sinusoidal, square, or exponential ramp, and may include a DC offset. The drive waveform is based on requirements of the pump selected and a balance between performance, audible noise, and pump longevity. The peak-to-peak voltage has a positive correlation with both flow rate and pressure handling of the pump. Depending on the manufacturers design, inappropriate voltages in the positive or negative may depolarize the piezo crystals, resulting in reduced performance. Too high of a voltage also may run the risk of electrical breakthroughs through the ceramic and jumping between electrodes. A slower rise time on the waveform will make the pumps audibly quieter, whereas a faster rise time may increase the performance of the pump; however, there is a limit as too sharp of a rise time can lead to cracking of the piezo crystal. Waveform frequency may increase the flow rate of the pump; however, the maximum frequency is limited by the recovery time of the check valves. Flow rate can be selectable by the user by adjusting at least one of duty cycle, frequency, waveform shape, and waveform peak-to-peak voltage if using piezoelectric pumps. A general circuit diagram for the device utilizing one or more piezoelectric pumps is shown in
Electric (DC) motor pumps designed for fluid delivery are typically of a diaphragm or peristaltic type. A DC diaphragm pump uses the reciprocating action of a diaphragm membrane in combination with check valves to cause positive displacement of the medium. The diaphragm flexes and creates negative pressure to draw in the medium, then flexes in the other direction to cause the medium to displace. Diaphragm displacement can be done with a DC motor and piston or other linear drive methods. The check valves ensure that the medium is only drawn in through one end and expelled from the other. Advantages of DC diaphragm pumps may include availability in a wide range of pressure and flow ratings and utility for a variety of fluids, including liquids and gas; however, if DC-driven, they may not be as compact or low power as the piezoelectric type of pump. A peristaltic pump uses a rotor with one or more rollers that compresses flexible tubing as it rotates inside a circular pump casing. As the tubing is pinched, it is closed off and the roller is able to push the medium forward through the line. The corresponding negative pressure created behind the roller then draws in the new medium from the inlet. Advantages to peristaltic pumps are low risk of occlusion, ability to handle highly viscous materials, and a high level of compatibility with different mediums since only the tubing is wetted. However, the pumps are typically larger and require more power, and the tubing used will wear out over time from squeezing and may need to be replaced. An electric (DC) motor pump would be driven by DC voltage ranging from 0 Volts to the maximum voltage recommended for the chosen pump with a duty cycle of 0-100%. Flow rate can be selectable by the user by adjusting at least one of DC voltage or duty cycle if using an electric (DC) motor pump. Suitable electric (DC) motor pumps are manufactured by, e.g., Parker, KNF, Schwarzer Precision, TCS Micropumps.
Various embodiments employing other combinations of pumps and fluid line arrangements are envisioned, including the ones depicted in the figures. In those embodiments, like reference numerals to the embodiment of
Alternatively, as shown in
In still other embodiments, the device also may incorporate a connection for an external vacuum line 452 (see
The fluid source and device may also interact with each other in a way that the programming inside the device receives information about the fluid that is attached. The information can be coded on the canister in multiple ways. Simple color coding or grayscale can be used to identify the solution, e.g., a light may reflect off a chosen color paint, sticker, dye, or other colorant and be picked up by a photodiode. Based on how much light that color reflects, software executed by processor on the device is able to determine type of solution. Alternatively, a bar or QR code or similar may be scanned with a laser reader or optical camera, the bar or QR code or similar having a large amount of information encoded, including but not limited to the type of solution, expiration date, and an identifier unique to that specific canister to monitor if it has been used before. In still another alternative, a passive RF tag or other form of near field communication can be installed on the canister and sensed by the device when the canister is installed. As with the bar or QR coding, this option also may allow for a large amount of information to be stored. Still further, some fluids may become ineffective after the expiration date, and the device can be programmed to prevent the use of such solutions. It also may be unsafe to use certain fluids in sequence, since they may mix and have an undesired chemical reaction with each other. Thus, the device may be configured to monitor the type and order of fluids used and analyze that information against data corresponding to prohibited or undesirable combinations in order to prevent such mixing. Also, only approved fluids may be used with the device, and one or more of the techniques described herein may be used to determine that the container is from an acceptable source and/or to track if the container has been used before to prevent refills, thereby preventing the use of untested fluids that may be harmful to the device or patient or otherwise may be outside of the application scope of the device.
The electronic control circuitry 30 provides the operator with variable or selectable control of fluid flow rate. To ensure that the desired flow rate is achieved, control circuitry 30 can monitor the flow rate via a feedback loop and can adjust the flow rate by varying the fluid pump drive parameters. By way of example, flow rates appropriate and safe for use in endodontic cleansing range from about 0.5 mL/min to 15 mL/min, and more preferably from about 0.5 mL/min to about 10 mL/min. For endodontic work, about 4 mL/min is a preferred flow rate of solutions delivered into a root canal by positive pressure irrigation syringe via a general use irrigation needle (Park, “Apical pressure and extent of irrigant flow beyond the needle tip during positive-pressure irrigation in an in vitro root canal model,” Journal of Endodontics 39.4: 511-515 (2013)), as there is no greater clearance of solutions at higher rates. Also, at higher flow rates the apical pressure generated during endodontic cleansing can cause irrigation solutions to penetrate beyond the apex into body tissue (Park 2013). Hypochlorite accident, i.e., expression of sodium hypochlorite (NaOCl) beyond the confines of the root canal, can result in significant patient harm. In another example, flow rates higher than 10 mL/min may have utility in periodontal application that don't have the risk of harm from positive pressure.
We determined suitable fluid pump flow-rates for a device in accord with the invention by measuring the back pressures created in 23, 27, and 30 gauge needles when liquid was pumped at various defined flow rates (0-15 mL/min) from a 60 ml syringe using an infusion syringe pump (All Pro Corporation, Model WZ-50C6T, modified to remove occlusion limiter). A pressure gauge (Honeywell True Stability Model SSCDANN030PGAA5) in direct communication with the fluid line recorded the pressures that developed at various flow rates. The experimental setup is depicted in
Results are shown in Chart 1 (
where:
ΔP—is the change in pressure
L—is the length of pipe
μ—is the dynamic viscosity
Q—is the volumetric flow rate
r—is the radius
d—is the inner diameter
π—is the mathematical constant Pi
Small gauge needles can achieve suitably high flow rates only if the pumping system can overcome high back pressure. Flow rate and back pressure created are linearly related. One can determine from the linear slope the required back pressure tolerance of a pump at a desired flow rate through a given tip. These results show that suitable fluid pumps must handle back pressures exceeding 10 psi and upwards of 30 psi to deliver suitable flow rates through commonly used needle tips. Flow rates could not be analyzed for some needle gauges because the infusion pump could not create pressures above 35 pounds per square inch (psi). With a 23 gauge needle, the back pressure remained under 5 psi when tested up to 15 mL/min. The 27 gauge needle could only be tested to 12 mL/min, at which rate it produced 30 psi of pressure. The 30 gauge needle caused much greater pressure, reaching 27 psi at only 5 mL/min. This can also be explained by the above equation, as the inner diameter is raised to the 4th power. The listed flow rates are for liquids; suitable flow rates for gases would range up to 20 L/min.
To determine configurations appropriate to achieve suitable flow rates using one or more piezoelectric pump (Bartels Mikrotechnik mp6), flow rate was measured for each of the three needle gauges in various configurations, including a single pump, two pumps with fluid paths in series, and two pumps with fluid paths in parallel, as shown above. The tubing used was 1/16 inch ID Tygon PVC, with 180 mm length at the inlet and outlet. For the parallel configuration, 10 mm of tubing was provided between the pumps and the Y-connector. For the series configuration, 10 mm of tubing was provided between the two pumps. Chart 2 (
The foregoing description was primarily directed to one or more embodiments of the invention. Although some attention has been given to various alternatives within the scope of the invention, it is anticipated that one skilled in the art will likely realize additional alternatives that are now apparent from disclosure of embodiments of the invention. Accordingly, the scope of the invention should be determined from the following claims and not limited by the above disclosure.
This application claims the benefit of priority from U.S. provisional application 62/147,061, filed Apr. 14, 2015, the disclosure of which is incorporated herein by reference in its entirety.
Filing Document | Filing Date | Country | Kind |
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PCT/US2016/027435 | 4/14/2016 | WO | 00 |
Number | Date | Country | |
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62147061 | Apr 2015 | US |