Patent Application
20060156875
Not applicable.
Not Applicable.
High pressure fluid streams provide one method of cutting tissue during a surgical procedure. Such “fluid jet cutting” has been used to cut, drill, bore, perforate, strip, delaminate, liquefy, ablate, and/or shape a diverse range of tissues. For example, fluid jets have been used to disintegrate and shape eye lens tissue, remove deposits from a vein or artery, and remove or shape meniscal tissue.
In use, a fluid is pressurized and a thin cutting beam is formed as the fluid stream travels through a tiny jet orifice in a surgical hand piece. A surgeon can vary the fluid pressure and/or the surgical hand piece depending on the type of surgical procedure that is performed. For example, selective variation of the jet stream pressure, (e.g., between 1 and 50,000 p.s.i.), allows the surgeon to cut hard bone, soft bone, cartilage and tissue, to strip away tissue exposing underlying organs or vessels or, simply, to wash away blood and debris created by the surgical procedure.
One exemplary fluid cutting jet system is disclosed in U.S. Pat. No. 6,216,573 to Moutafis et al. and is hereby incorporated by reference in its entirety. The fluid cutting jet system includes a variable pressure pump for generating a high pressure fluid jet. In use, a user can turn on, increase, and/or decrease the pressure of the pump by adjusting dials or buttons.
Despite the existence of these fluid cutting jet systems, there remains a need for fluid jet cutting system that can provide improved cutting performance. Conventional cutting systems often lack robust controllers that can account for variations within the fluid cutting jet system. Such controllers might only limit the maximum pressure in the interest of safety. For example, a simple ON/OFF controller that deactivates the pump in the event of an overpressure situation.
Other controllers, as disclosed in the above referenced Patent, allow a user to turn on the system and increase or decrease pump pressure. However, this system fails to account for the use of different surgical cutting wands and/or orifice dimensions that can vary within manufacturing tolerances. As a result, the cutting performance (i.e., cutting depth) is not consistent for a given pump pressure setting. The lack of a robust controller thus results in inconsistent cutting jets that can vary widely with the characteristics of the cutting jet system.
Disclosed herein are fluid cutting jet control systems that provide improved cutting performance. In one aspect, the control system achieves improved performance by controlling the jet power of the cutting stream. The cutting stream produced is less sensitive to variations, such as, for example dimensions that fluctuate within manufacturing tolerances and/or with different end effectors.
In one aspect, a fluid cutting jet system includes a fluid pump for pressurizing fluid including a fluid inlet and a fluid outlet. A control console communicates with the pump and is adapted to control the fluid jet power of the fluid cutting stream by manipulating pump settings. For example, the control console can include a processor that receives input from a user and sends an output signal to control the pump. A user can enter a cutting set point, and the control console then sends a signal indicating the proper pump setting.
In another aspect, the control console controls the power level of the pump motor. For example, where the pump motor is an electric motor, the control console can control the electrical power delivered to the pump.
The processor can also receive a feedback signal from a sensor and can vary the output signal in response to the feedback signal. Exemplary sensor(s) can be positioned throughout the system. For example, a sensor(s) can be positioned on/in the end effector to measure flow rate and/or pressure. An alternative or additional sensor can provide data to the control console related to the pump, such as, for example, the power delivered to the pump motor.
In another aspect, a method for controlling the fluid cutting jet is disclosed. In one embodiment, the method includes providing a fluid cutting jet system having a fluid pump for pressurizing fluid. The pump includes a pump motor for driving the pump, a control console connected to the pump motor and adapted to vary the pump motor power level, and an end effector including a nozzle for delivering pressurized fluid to tissue. The method further includes the steps of inputting a set point and varying the pump motor power level in response to the set point. In one aspect, the set point is representative of fluid jet power.
The method can include the further steps of providing a feedback signal to the control console from at least one sensor positioned to monitor a system variable. In response to the feedback signal, the control console can vary the pump motor power level.
The invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
Disclosed herein is a fluid jet cutting control system that provides improved cutting performance. The system includes a pump which delivers a fluid stream to an end effector. The fluid exits the end effector as a cutting stream that can be used to create surgical incisions. In one aspect, improved system performance is achieved by controlling the jet power of the cutting stream. In a further aspect, pump power is manipulated to control the jet power of the cutting stream.
Pump 12 can include a pump motor 22 that drives pump assembly 24 to pressurize the fluid. In one aspect, the pump is a positive displacement piston pump, however, one skilled in the art will appreciate that a variety of other pumps are available. For example, other pump mechanisms such as an air intensifier could be substituted.
The delivery tube 18 into which the fluid is delivered is preferably flexible and pressure resistant so that end effector 20 can be moved independently of pump 12. In one embodiment, delivery tube 18 is also adapted to detachably connect to end effector 20 so that different end effectors can be used with system 10. For example, a high-pressure quick connect at the end of delivery tube 18 can detachably connect to end effector 20.
End effector 20 can be a handheld or machine controlled surgical jet instrument that is in fluid communication with delivery tube 18. For example, end effector 20 can include a proximal handle portion 23, internal lumen (not shown), and one or more distal jet orifice(s) 21 that are positioned axially or transversely. In addition, end effector 20 can have a tip section 25 that is selectively moldable allowing the user to reshape or bend the jet tip into a desired configuration, or at an angle, thus facilitating positioning at the cutting site. One of skill in the art will appreciate that a variety of jet-creating-end-effector configurations can be used.
End effector 20 can further include a fluid evacuation pathway for the removal of fluid from a surgical site. For example, an exit orifice located near the fluid delivery orifice can receive debris caused by the fluid cutting, as well as, cutting fluid. The removed debris and fluid can travel through exit lumen 27 in fluid contact with the exit orifice. In one aspect, suction may be employed to assist with debris and fluid removal, however, the outflow can also be gravity drained.
The flow of cutting fluid from end effector 20 is preferably controlled by console 14. A user can input a setting into console 14 and the console can output control data. For example, control console 14 can include controls 28 so that a user can vary the system settings, such as, the jet power of the fluid exiting orifice 21. Controls 28 can also be positioned remotely from console 14, such as via a foot switch (not shown in
Console 14 is preferably in electrical communication with pump 12 to facilitate control of the pump.
In one embodiment, processor 30 controls the pump 12 in response to input from a user and/or a sensor. For example, when user enters a cutting set point, the controller determines the proper pump motor settings and sends an output signal that controls the pump. Processor 30 can include, for example, discrete electronic components, integrated circuit semiconductors, microcontrollers (e.g., stand alone computing units), and combinations thereof. One skilled in the art will appreciate that the variety of known processors can be used to assist with operation of system 10. In addition, where a control system is used, a variety of controllers can be used. For example, the controller can be analog (continuous) or digital (discrete), open or closed loop, and can incorporate single or multiple variables. Exemplary controllers include PI control, PID control, and IMC-based PID control. Simplistic control systems, such as on/off control can also be used. One skilled in the art will appreciate that a variety of other control systems can be implemented in system 10.
Processor 30 can receive signals from sensor(s) located throughout system 10. As shown in
In addition, or as an alternative, system 10 can include other sensors for measuring fluid jet characteristics such as fluid flow rate and/or fluid pressure. In one aspect, sensors are positioned within end effector 20 to measure cutting fluid variables and/or outlet flow rate. For example, sensors can measure flow rate and/or pressure within the internal lumen of end effector 20. Other sensor locations include placement immediately adjacent to fluid jet orifice 21, in console 14, and/or sensors positioned in a surgical field separate from end effector 20.
Sensors 32 are preferably in communication with processor 30 and can transfer data electronically through wires or wirelessly. For example, dotted line 33 illustrates console 14 electronically communicating with sensors 32.
To protect against contamination of fluid flowing through the pump and to facilitate sterilization, the pump motor can drive the fluid via a replaceable cartridge 26. In one aspect, cartridge 26 contains the fluid pathway. Pump assembly 24 can act on cartridge 26 and pump the cutting fluid without the pump assembly contacting the fluid. After each use, the cartridge can be replaced.
System 10 can provide consistent cutting jet performance. In one embodiment, the improved performance is obtained by adjusting or controlling system variables to achieve a desired jet power from the fluid cutting stream. The resulting cutting stream can provide consistent cutting depth and is less susceptible to system variations. For example, dimensions that fluctuate within manufacturing tolerances and the substitution of different end effectors have less impact on the cutting performance of system 10. The result is an accurate and precise fluid cutting jet.
Jet power depends on the pressure and volumetric flow rate of the fluid cutting jet. As shown in Equation 1 jet power is the product of pressure and flow rate.
Jet Power=Pressure×Volume Flow Rate (1)
At a constant jet power, a change in one variable (pressure or flow rate) is compensated for by an inverse change in the other variable. For example, if system pressure were to drop, an increase in flow rate of the cutting fluid would compensate.
The advantages of controlling jet cutting system 10 based on jet power are illustrated in
At a smaller nozzle size (0.005), the pressure increases but the volumetric flow rate decreases, while a larger nozzle size results in an increases in volumetric flow rate but a decrease in pressure. However, as shown in
In one embodiment, the jet power of system 10 is directly measured with pressure and flow rate sensors such as sensors 32 illustrated in
In another embodiment, jet power is controlled indirectly. For example, Applicant has found that the power delivered to the pump motor (e.g., Watts of power) can be controlled to achieve a desired jet power. Directly measuring fluid pressure and flow rate can be complicated, so controlling pump motor power facilitates the control of system 10.
Using pump power to control the fluid cutting jet provides an advantage over conventional fluid jet control systems. In fact, compared to prior art systems in which the fluid stream is controlled by controlling pump speed, Applicant has found that variations in the fluid cutting jet system created less variations in cutting performance when pump power is used as a control variable. For example,
In one embodiment, Applicant therefore controls system 10 by controlling pump power. When a user enters a set point in console 14, processor 30 determines the proper pump power and controls the pump power to achieve the desired cutting performance.
To assist with controlling pump power, a feedback control system can be used. In one embodiment, the processor 30 receives data representative of the pump power to assist with feedback control of the system. In one embodiment, sensors positioned on the pump motor 22 and/or pump assembly 24 can provide processor 30 with feedback input. Such input can be, by way of non-limiting example, the actual power delivered to the pump motor (e.g., watts of power delivered), pump activity (e.g., rpm of the pump motor or speed of the pump piston), flow rate of the cutting fluid, and/or pressure of the fluid exiting pump 12. Based on the data delivered by sensors 32, controller 30 can fine tune the power delivered to pump 12. In another embodiment, other feedback data can be sent to processor 30 to assist with system control. For example, processor 30 can receive data representative of other variable(s) that are related to jet power (e.g., pressure and/or flow rate data).
One skilled in the art will appreciate further features and advantages of the invention based on the above-described embodiments. Accordingly, the invention is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety.
