Surgical Handpiece And Flow Control System For Use Therewith

Abstract

A flow control system is used in conjunction with a surgical handpiece for the removal of unwanted material in a very small enclosed operative site in which it is very critical to maintain a pressure within a certain range, such as in the surgical operation of the removal of a cataract lens from the human eye. The system includes an irrigation subsystem comprising a source of treatment fluid, such as an artificial aqueous solution, at a preselected constant pressure for supplying said fluid to the enclosed operative site via the handpiece. A suspension of the treatment fluid, including any unwanted material, is removed from the operative site by an aspiration subsystem. The aspiration subsystem comprises a pump used to remove the suspension and to overcome the friction and other losses throughout the entire fluid system, a flow transducer for measuring the rate of flow, and a vent valve to reduce the flow in the aspiration subsystem when necessary to assist in maintaining a relatively constant pressure within the operative site. An electronic flow control receives signals from the flow transducer and reacts to certain changes in flow signals by sending a signal to the venting valve.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a flow control system to be used with surgical handpiece, the combination of which is primarily concerned with the removal of tissue from any enclosed or semi-enclosed operative site. This flow control system is particularly of interest and value where it is important that the pressure in the operative site be maintained within relatively narrow limits and particularly where the total volume of the operative site chamber is very small in relation to the rest of the fluid in the system. Although by no means limited thereto, the present system is of particular advantage when used with an ultrasonic handpiece for the removal of a cataract lens in the human eye.

The usual procedure in the removal of a cataract lens from a human eye often involves a 180.degree. incision allow the surgeon to lift up the cornea and lift out the lens in toto. The flow control system of this invention makes it possible to remove a cataract lens from a human eye by making only a small incision in the eye and inserting the tip of the surgical handpiece therein so that the tip is within the anterior chamber (operative site) of the eye providing access to the lens.

One type of handpiece, (hereinafter to be referred to as the ultrasonic handpiece), includes a source of vibratory motion as well as a passage for treatment fluid to flow into the anterior chamber (operative site) and a passage for the fluid and unwanted material (hereinafter to be referred to as the suspension), to exit from the anterior chamber (operative site). The combined or separate action of the flowing fluid and/or the force of the vibratory motion of the handpiece when in contact with or adjacent to the lens of the eye will cause the lens to break apart and be removed from the eye. One example of such a handpiece is disclosed in the copending application of A. Banko and C. Kelman, Ser. No. 655,790 filed July 25, 1967 entitled "Material Removal Apparatus Employing High Frequency-vibration", now U.S. Pat. No. 3,589,363 dated June 29, 1971 and assigned to he assignee of this application. Discussion throughout this specification of maintaining a relatively constant pressure is intended to refer only to the pressure caused by the treatment fluid and not to any effect of the acoustic pressure waves caused by the ultrasonic vibrations. The latter effects can be neglected with respect to the flow parameters of interest to the invention disclosed herein.

Another type of handpiece, (hereinafter to be referred to as the irrigation-aspiration handpiece), merely contains two passages for flow into and out of the operative site. It is usually used during a type of "cleaning up" procedure within the enclosed operative site, though may be used as an alternative to the ultrasonic handpiece where the unwanted material is particularly soft and does not require the use of ultrasonics to break it apart.

When the handpiece is inserted into the eye or operative site, and in the case of the eye, the anterior chamber, it is very important that the pressure of the anterior chamber is maintained within a certain range of values, since otherwise various portions of the eye could be damaged. A collapse of the anterior chamber could result in either the iris, the endothelium layer of the cornea, or the posterior capsule, as well as other parts coming into contact with that portion of the handpiece within the eye which is connected to a source of fluid suction as well as a source of high frequency vibration, either of which could cause damage to one or more of the above-named parts of the eye. This problem of maintaining the proper pressure is a particularly difficult and sensitive one in the case of an operative site wherein the volume of said operative site considerably smaller than the volume of fluid which is necessary for the irrigating and aspirating subsystems connected to the handpiece for maintaining the necessary flow to and from the operative site. In addition, as in the case of a cataract operation, when the lens or portions thereof are drawn towards the surgical handpiece tip within the operative site, there is a possibility of particles which are bigger than the exit passage from the operative site to occlude the fluid line in the tip portion of the handpiece leading to the aspiration subsystem. When this occlusion occurs, there is an increased negative pressure or suction in the fluid line between the operative site and the pump which is assisting in the aspirating of the fluid out of the operative site. When the occlusion is finally removed, whether it be by the mechanical action of the ultrasonic tip or by an increase in the value of the aspirating force at the tip of the handpiece or due to any other reason, the flow control system is designed so there is an extremely rapid equalization of the pressure in the entire system. If there were no such equalization of the pressure, then due to this increased negative pressure or suction in the aspiration line, there would be a tendency for all of the fluid volume of the operative site to be suddenly conducted through the handpiece towards the pump once the occlusion is removed. This is especially true where the volume of the operative site is small relative to the volume of the remainder of the fluid system. This could result in anywhere from a partial to a total collapse of the enclosed operative site resulting in undesirable damage.

Therefore, it is an object of the present invention to provide a flow control system for keeping the pressure within an enclosed or semi-enclosed operative site at a relatively constant level.

Another object of this invention is to provide a flow control system for keeping the pressure within an enclosed or semi-enclosed operative site relatively constant while forcing a fluid through said chamber for the removal of unwanted material from said chamber.

A further object of the invention is to provide a flow control system for keeping the pressure in a small enclosed or semi-enclosed operative site relatively constant while forcing a fluid through said operative site and applying a high frequency mechanical vibratory force to a material within said chamber resulting in the breaking apart and removal of said material.

A still further object of the invention is to provide a flow control system which is sufficiently sensitive to certain changes in flow rates such that prior to any significant collapse of an enclosed site, an adjustment is made on the fluid system to avoid said collapse.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and objects of this invention, reference should be made to the following detailed disclosure taken in connection with the accompanying drawings in which:

FIG. 1 is a cross-sectional view of an ultrasonic handpiece showing its basic internal construction;

FIG. 2 is a cross-sectional view of an irrigation-aspiration handpiece showing its basic internal construction;

FIG. 3 is a pictorial representation of a human eye in enlarged form and illustrating the use of a surgical handpiece in cataract removal; and

FIG. 4 is a schematic diagram of the combination of the ultrasonic handpiece and the flow control system.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Referring to FIG. 1, the ultrasonic handpiece 10 includes a proximal end 11 and a distal end 12 and hydraulically coupled to a power and coolant supply 15 (FIG. 4) at its proximal end 11 via a coolant fluid inlet tube 16 and a coolant fluid outlet tube 17 and a pair of electrical leads 18. The electrical leads 18 are connected to coil 19 which is wound internally within the ultrasonic handpiece 10. Within said handpiece, there is a vibratory body 20 containing a transducer element 21 at the proximal end 11 of said vibratory body 20. The transducer element which may be either magnetostrictive or electrostrictive type converts the high frequency alternating current generated in the coil 19 into high frequency mechanical vibrations. The transducer element 21 is energized by the coil 19 containing the high frequency electrical signal and the resulting mechanical vibrations are transmitted via a connecting body 22 to an operative tip 23 at the proximal end 12 of the handpiece 10. The high frequency electrical signal is provided by a circuit (not shown) in the power and coolant supply 15. There are many such circuits which are well known in the art and need not be further described here.

Due to the heat generated in the transducer element 21 by the electrical-to-mechanical energy conversion occurring in the ultrasonic handpiece 10, especially if it is of a magneto strictive type, a source of coolant is provided by the power and coolant supply 15, and it is carried to and from the handpiece 10 by the coolant fluid inlet and outlet tubes 16 and 17.

The other major elements of the handpiece 10 which are coupled to the irrigation and aspiration subsystems of the flow control system, respectively, are a fluid inlet channel 24 and a fluid outlet channel 25. The fluid inlet channel 24 connects with an annular passage 26 within the ultrasonic handpiece 10 which surrounds the connecting body 22 and the operative tip 23 and terminates at the very distal end 12 of the handpiece 10. The fluid outlet channel 25 connects with a bore 27 through the center of the connected body 22 and with the bore 28 through the center of the operative tip 23 termination at the very distal end 12 of the handpiece 10. For more details on the operation of such an ultrasonic handpiece reference is made to the above-named copending patent application.

Referring to FIG. 2, the irrigation-aspiration handpiece 30, having proximal end 31 and a distal end 32 has a fluid inlet channel 34 coupled to the irrigation subsystem of the flow control system. The fluid from the irrigation subsystem flows through an annular space 35 within the handpiece and exits at the distal end 32. The suspension from the operative site flows through a center bore 36 and exits at the fluid outlet channel 37 at the proximal end 31 of the handpiece 30. The fluid outlet channel 37 is coupled to the aspiration subsystem of the flow control system.

While the invention system can be used for the removal of material from any enclosed volume, particularly a volume in which the maintenance of a relatively constant pressure is critical, some of the discussion in this disclosure will refer to the removal of a cataract lens from the human eye as one particular example. The use of a surgical handpiece as applied to cataract removal is illustrated in FIG. 3. A portion of a simplified cross-section of a human eye is shown to illustrate the manner in which the device is employed.

Referring to FIG. 3, the opaque or cataract lens which is to be removed is designated by the number 40, and is enclosed in a membrane including an outer portion 40a known as the anterior capsule. The iris is designated by the numeral 41 and the major gel-filled portion of the eye, or vitreous, is designated as 42. The cornea, the transparent outer surface of the eye, is shown as 43, and the portion of the eye generally called the anterior chamber is designated as 45. A small incision 46 is made near the edge of the cornea 43 to provide access for the distal end 12 of the ultrasonic handpiece 10 or the distal end 32 of the irrigation-aspiration handpiece 30.

Referring to FIG. 4, the dotted lines represent electrical connections and the solid lines represent hydraulic connections. Those components of the flow control system which are hydraulically coupled to the fluid inlet channel 24 of the ultrasonic handpiece 10 are part of the irrigation subsystem and those components which are hydraulically coupled to the fluid outlet channel 25 are part of the aspiration subsystem.

The irrigation subsystem comprises a treatment fluid supply 50 having a pressure P.sub.1 and a treatment fluid supply 55 having a pressure P.sub.2, with P.sub.2 being greater than P.sub.1. The treatment fluid is preferably a solution, which is compatible with the tissue being treated. For purposes of cataract removal, an artificial aqueous solution has been found to be satisfactory. The treatment fluid supplies 50 and 55 are connected to the fluid inlet channel 24 of the ultrasonic handpiece 10 by hydraulic tubing 56.

The function of the aspiration subsystem is to remove from the enclosed operative site (in the case of the eye it is the anterior chamber 45, see FIG. the excess treatment fluid and/or any other unwanted material which the surgeon may want to signal removed. The fluid and other unwanted material being removed from the enclosed operative site shall hereinafter be referred to as the suspension. All the components of the aspiration subsystem are interconnected and connected to the fluid outlet channel 25 of the ultrasonic handpiece 10 by hydraulic tubing 58, hereinafter to be referred to as the main suction line.

The aspiration subsystem includes a flow transducer 60, which is the first major component downstream from the handpiece 10 along the main suction line 58. The flow transducer 60 does not impede the flow of the suspension, but it is designed to sense the flow rate and produce a corresponding electrical signal which is transmitted to the electronic flow control 70, which will be discussed in more detail later. The flow transducer 60, which is a commercially available product, is an electromagnetic device which produces an electrical signal proportional to the flow velocity of the suspension. The flow transducer 60 is energized by the master control panel 80.

The next major component in the aspiration subsystem downstream from the flow transducer 60 and along the main suction line 58 is the by-pass valve 90. Also connected to the by-pass valve via a tube 99 is a by-pass reservoir 100. The by-pass valve 90 is a double action solenoid such that in one position, to be referred to as its aspiration position, the suspension is allowed to flow unimpeded through the main suction line 58 and there is no flow in tube 99. In the other position of the solenoid, to be referred to as its by-pass position, there is no flow of the suspension while the solution from the by-pass reservoir 100 is allowed to flow.

The next major component in the aspiration subsystem downstream from the by-pass valve 90 and along the main suction line 58 is the pump 110. The pump 1110 is a constant displacement, variable speed, peristaltic pump. The peristaltic feature is to avoid any contact of the pump with the suspension hence minimizing maintenance problems of the pump 110, and the tubing can be easily removed from the pump for the purposes of sterilization. The constant displacement feature is necessary in order to insure accurate sensing of flow by the flow transducer 60, especially due to the exceedingly small fluid volume of the anterior chamber 45 of the eye relative to the fluidic volume of the remaining hydraulic components of the system.

Another component of the aspiration subsystem is the by-pass reservoir 100, coupled to the main suction line 58 via the by-pass valve 90. When the solenoid of the by-pass valve 90 switches to its by-pass position, the flow from the flow transducer 60 ceases, hence the aspiration of the anterior chamber 45 of the eye ceases, and instead there is a flow from the by-pass reservoir 100. The by-pass reservoir 100 is used to insure that fluid fills all portions of the main suction line 58 at all times, so that the hydraulic response time of the system is kept to a minimum. Thus, even though suction at the handpiece 10 may not be desired, from time to time, the continuously running pump 110 is always ready to apply the required suction, wherever necessary.

Another component of the aspiration subsystem is the vent valve 120 which is intermediate of the by-pass valve 90 and the pump 110. The vent valve 120 is a spring loaded, electrically operated solenoid which is normally in a shut position. An electrical signal from the electronic flow control 70 causes the vent valve 120 to open and close to complete a cycle. What determines the existence of such a signal shall be discussed in more detail later. The function of the vent valve 120 is to provide for a pressure equalization between atmospheric pressure and the hydraulic pressure in the main suction line 58, hereinafter to be referred to as venting, hence negating pressure buildup in the aspiration subsystem upon removal of the occlusion. The master control panel 80 selectively enables the vent valve 120. This allows the vent valve 120 to become inoperative so that the system can be started prior to the commencement of an operation. The electronic flow control 70 has a control for adjusting the amount of time the vent valve 120 remains open.

In the operation of the components heretofore described, a suitable footswitch 130, having a foot-actuated control arm 135 with a conductive segment 136, is uses, having an "off" position, three stable "on" positions and a fourth position to be called the transition position or position T. Position T results only when the control arm 135 moves between two of its stable "on" positions.

While nothing is activated in the "off" position, it is important to note that the solenoid of the by-pass valve 90 is in its by-pass position at this time. This would allow sterilized solution from the by-pass reservoir 100 to flow through a portion of the aspirat1on subsystem, assuming the pump 110 is in operation. The footswitch 130 has no switching function with respect to the pump 110.

In footswitch position 1, (hereinafter the irrigation position), since the conductive segment 136b of the control arm 135 bridges the pair of spaced contacts 137, the treatment fluid supply 50 is actuated, such that the treatment fluid at a pressure P.sub.1 flow to the fluid inlet channel 24. The solenoid of the by-pass valve 90 remains in its by-pass position.

In footswitch position 2, (hereinafter the irrigation and aspiration position), since the conductive segment 136b of the control arm 135 bridges the pair of spaced contacts 138, the treatment fluid supply 55 is actuated such that the treatment fluid at a pressure P.sub.2 flows to the fluid inlet channel 24. In addition, since the conductive segment 136c of the control arm 135 bridges the pair of spaced contacts 139, the by-pass valve 90 changes to its aspiration position.

In footswitch position 3, (hereinafter the ultrasonic position), since the conductive segments 136b and 136c bridge the pair of spaced contacts 141 and 142, it can be seen that the irrigation and aspiration subsystems remain in the same state as when the control arm 135 was in footswitch position 2. However, in addition, since the conductive segment 136a bridges the pair of spaced contacts 143, the circuit (not shown) of the power and coolant supply 15 is coupled to the ultrasonic handpiece 10, assuming the power and coolant supply 15 has already been energized by the master control panel 80. This results in high frequency vibrations of the operative tip 23 of the vibratory body at the proximal end 12 of handpiece 10. Simultaneous to this, a pressurized coolant is caused to flow to the handpiece 10 and back to the power and coolant supply 15 via the coolant inlet an outlet tubes 16 and 17. All the other controls of the power and coolant supply 15 are on the master control panel 80 including the on-off switch, the power level control of the circuit and the pressurizing of the coolant supply.

Position T, (the transition position) of the footswitch 130, occurs whenever the footswitch control arm 135 moves from position 1 to position 2 or vice versa. During such movement the conductive segment 136b bridges the pair of spaced contacts 144 which causes actuation of the electronic flow control 70 such that an electrical signal is sent to the vent valve 120 causing a venting of the main suction line 58, hence an equalization of the pressure in the entire aspiration subsystem.

A functional description of the electronic flow control 70 is necessary to tie together the entire system. The electronic flow control 70, which is energized by the master control panel 80, continually receives signals from the flow transducer 60 concerning the flow rate of the suspension and contains circuitry to differentiate these signals such that an electrical signal results whenever certain changes in the flow rate signals occur. The circuitry is designed so that whenever the flow rate falls below a first predetermined value and subsequently increases above a second predetermined value, a pulse is generated and sent to the vent valve 120. This results in the venting of the main suction line 58 causing the momentary elimination of the negative pressure at the bore 28 of the operative tip 23 and substantially reducing the flow of the suspension through the main suction line 58. The circuitry of the electronic flow control 70 is designed so as to account for all of the fluidic parameters of the entire system.

In addition, the circuitry of the electronic flow control 70 is designed so that whenever certain irregular conditions are sensed, such as the passage of air bubbles or lens particles through the flow transducer 60 or an impact against or constriction of one of the hydraulic tubes in the aspiration subsystem, the electronic flow control 70 will send an electrical signal to the vent valve 120.

While FIG. 4 illustrates the use of the flow control system with the ultrasonic handpiece 10, it would be equally applicable with the irrigation-aspiration handpiece 30 except that footswitch position 3 would be inapplicable.

Set-up and Operation of the System

Before commencing an actual operation it is necessary to set the pressures P.sub.1 and P.sub.2 and the speed of the pump 110 to within the approximate range that will be required for the operation. A rubber type chamber is positioned over the tip and P.sub.1, P.sub.2 and the pump speed are set by observing the effects on the rubber chamber. The desired effects on the rubber chamber are determined empirically by past experience.

Since P.sub.1 is used when the footswitch is in position 1 and there is no aspiration, it must be set at a value such that it will mantain the enclosed operative site at a relatively constant volume taking into account the pressure drops throughout the irrigation subsystem and the fluid and/or suspension which may flow from the enclosed operative site through the incision leakage around the proximal end of the handpiece.

P.sub.2 must be at a value higher than P.sub.1 since it will be used when the footswitch is in position 2 when there is aspiration due to the operation of the pump.

It is also necessary to prime the fluid system prior to start of the operation. During this priming operation, the flow transducer 60 and the electronic flow control 70 will remain de-energized from the master control panel 80. Otherwise, continual venting would make the priming of the system very difficult, if not impossible.

It is also necessary to choose the power level for the circuit in the power and coolant supply 15. The power level determines the amplitude of that portion of the operative tip 23 which comes into contact with the cataract lens. Usually the minimum possible power level to accomplish the task is chosen.

The electronic flow control 70 requires certain internal balances of its electrical components to take into account the ambient factors of the operating room and needs to be energized prior to the commencement of an operation to stabilize it as to temperature, transient signals, etc. Therefore, after the priming of the entire irrigation and aspiration subsystems has been completed, the flow transducer 60 and the electronic flow control 70 are energized. Then while the entire system is operating at its maximum desired flow, as determined by the various settings discussed above, the electronic flow control 70 is programmed to read such a flow as the maximum flow rate. Then an artificial occlusion is placed along the aspiration subsystem as close to the distal end 12 of the handpiece 10 as possible. The electronic flow control 70 is then programmed to sense this as the minimum flow rate. These minimum and maximum flow rates plus the circuitry of the electronic flow control 70 which has been designed to take into account all the parameters of the system, determine the two predetermined values of flow rate, mentioned above, about which the electronic flow control 70 will react to generate an output signal to send to the vent valve 120. In addition, there is a sensitivity setting on the electronic flow control 70 which regulates the response time of the electronic flow control 70 to signals received form the flow transducer 60.

Most of the controls which are available to the surgeon and which are necessary to understand the inventive aspects of the system have already been described above. Decisions as to when to change one of the settings are in the complete discretion of the surgeon and determined in part by his operating techniques which need not be discussed for purposes of describing the invention.

The main and most serious operating problem which the surgeon must contend with is when a particle occludes the tip 23 such that the suspension is unable to leave the enclosed operative site. Since the pump 110 continues to operate, the vacuum in the main suction line 58 will tend to increase. The surgeon will become aware of such a condition almost instantaneously and will handle the handpiece and/or ultrasonic controls in such a manner as to break apart the occlusion. At the moment the occlusion clears the tip there would be a tendency for the fluid and/or suspension within the enclosed operative site to rush into the main suction line 58 to fill the vacuum created therein. This imbalance of pressures during the occlusion, between the enclosed operative site and the main suction line 58, is especially critical since the volume of the enclosed operative site is exceedingly small as compared to the volume of the main suction line 58. If the increased flow from the enclosed operative site to the main suction line 58 is allowed to continue for too long a period of time (measured in milliseconds) it is possible that the entire contents of the enclosed operative site, including parts which are not meant to be disturbed, will be forced against the handpiece tip 23 and damaged. In the case of the human eye there is a further risk that the entire anterior chamber 45 would collapse. Any increased flow at the handpiece tip 23 will be immediately sensed at the flow transducer 60, since the average time for an occlusion is very small and there is a column of liquid between the handpiece tip 23 and the flow transducer 60. The flow transducer which is continually sensing the flow, will send a signal to the electronic flow control 70 proportional to he higher rate for flow. Since the electronic flow control 70 has been electronically programmed to react to certain changes in he flow signals, an output signal will be sent to the vent valve 120 to vent the main suction line 58 to atmosphere and reduce the vacuum in said line. Depending upon whether the condition is corrected after one venting, the signals from the flow transducer 60 may cause the electronic flow control 70 to send another output signal to the vent valve 120. This could be repeated several times until there is an equilibrium in the flow.

It will be apparent from the foregoing, that a novel improved flow control system for the removal of unwanted material from an enclosed operative site in which it is very critical to maintain a pressure within a certain range, has been disclosed. It is also recognized that many variations of the particular system disclosed herein will occur to those skilled in the art, without departing from the spirit of the invention. Accordingly, the invention is to be deemed limited only by the scope of the appended claims .

Claims

I claim:

1. Flow control system for removing a suspension of unwanted material in a treatment fluid from an enclosed operative site comprising,

a source of treatment fluid at a certain pressure for causing said fluid to flow into the enclosed operative site including hydraulic tubing for connecting said treatment fluid source to the enclosed operative site,

a source of negative pressure for withdrawing the suspension from the enclosed operative site including hydraulic tubing for connecting said negative pressure source to the enclosed operative site,

a flow transducer intermediate of and interconnected by the hydraulic tubing between the negative pressure source and the enclosed operative site, for sensing the flow of suspension and for generating an electrical signal proportional to said flow,

a vent valve coupled to the hydraulic tubing between said flow transducer and said negative pressure source for venting the flow of the suspension to atmospheric pressure, and

electronic flow control means electrically interconnected to said flow transducer and said vent valve for sending an electrical signal to said vent valve for venting the hydraulic tubing through which said suspension flows upon sensing a predetermined signal.

2. A flow control system in accordance with claim 1, wherein said electronic flow control means senses certain changes in flow rates due to the signals received from the flow transducer and at a certain predetermined value, sends an electrical signal to the vent valve for venting the hydraulic tubing through which said suspension flows.

3. A flow control system in accordance with claim 1, further involving a bypass reservoir and a solenoid operated valve located intermediate of and interconnected by the hydraulic tubing between the flow transducer and the negative pressure source, the solenoid operated valve having a first position wherein the suspension only flows from the flow transducer to the negative pressure source, and having a second position wherein fluid only flows from the bypass reservoir to the negative pressure source.

4. A flow control system in accordance with claim 1 wherein

the source of treatment fluid includes two separate sources of fluid each of which has a different pressure, and

said flow control system further including

switch means having at least two positions, said first switch position coupling only the source of treatment fluid having the lower pressure to the enclosed operative site, said second switch position coupling the source of treatment fluid having the higher pressure and the negative pressure source to the enclosed operative site, with the vent valve receiving an electrical signal to vent the hydraulic tubing between the flow transducer and the negative pressure source whenever the switch means moves between these two positions.

5. Flow control system for removing a suspension of unwanted material in a treatment fluid from a small enclosed operative site comprising,

a first source of treatment fluid at a certain pressure for causing said fluid to flow into the enclosed operative site including hydraulic tubing for connecting said first treatment fluid source to the enclosed operative site,

a second source of treatment fluid at a pressure higher than the first source for causing said fluid to flow into the enclosed operative site including hydraulic tubing for connecting said second treatment fluid source to the enclosed operative site,

a source of negative pressure for withdrawing the suspension from the enclosed operative site including hydraulic tubing for connecting said negative pressure source to the enclosed operative site,

a flow transducer intermediate of and interconnected by the hydraulic tubing between the negative pressure source and the enclosed operative site, for sensing the flow of the suspension and for generating an electrical signal proportional to said flow,

a vent valve coupled to the hydraulic tubing between said flow transducer and said negative pressure source for venting the flow of the suspension to atmospheric pressure,

electronic flow control means electrically interconnected to said flow transducer and said vent valve for sensing certain changes in flow rates due to the signal received from said flow transducer and, at certain predetermined value, for sending an electrical signal to the vent valve for venting the hydraulic tubing through which said suspension flows, and

a switch means having at least two positions, said first switch position coupling only the first source of treatment fluid to the enclosed operative site, said second switch position coupling the second source of treatment fluid and the negative pressure source to the enclosed operative site, with the vent valve receiving an electrical signal to vent the hydraulic tubing between the flow transducer and the negative pressure source whenever the switch means moves between these two positions.

6. A flow control system in accordance with claim 5 further including

a bypass reservoir, and

a solenoid operated valve located intermediate of and interconnected by the hydraulic tubing between the flow transducer and the negative pressure source, having a first position wherein the suspension only flows from the flow transducer to the negative pressure source, and having a second position wherein fluid only flows from the bypass reservoir to the negative pressure source.

7. The combination of a surgical handpiece and a flow control system for removing a suspension of unwanted material in a treatment fluid from an enclosed operative site wherein said surgical handpiece comprises

a fluid inlet channel for treatment fluid to enter the enclosed operative site,

a fluid outlet channel for the suspension of unwanted material in the treatment fluid to exit from the enclosed operative site, and

wherein the flow control system comprises

a first source of treatment fluid at a certain pressure for causing said fluid to flow into the enclosed operative site, including hydraulic tubing for connecting said first treatment fluid source to the enclosed operative site,

a second source of treatment fluid at a pressure higher than the first source for causing said fluid to flow into the enclosed operative site, including hydraulic tubing for connecting said second treatment fluid source to the enclosed operative site,

a source of negative pressure for withdrawing the suspension from the enclosed operative site including hydraulic tubing for connecting said negative pressure source to the enclosed operative site,

a flow transducer intermediate of and interconnected by the hydraulic tubing between the negative pressure source and the enclosed operative site, for sensing the flow of the suspension and for generating an electrical signal proportional to said flow,

a vent valve coupled to the hydraulic tubing between said flow transducer and said negative pressure source for venting the flow of the suspension to atmospheric pressure,

electronic flow control means electrically interconnected to said flow transducer and said vent valve for sensing certain changes in flow rates due to the signal received from said flow transducer and, at a certain predetermined value, for sending an electrical signal to the vent valve for venting the hydraulic tubing through which said suspension flows, and

a switch means having at least two positions, said first position coupling only the first source of treatment fluid to the enclosed operative site, said second switch position coupling the second source of treatment fluid and the negative pressure source to the enclosed operative site, with the vent valve receiving an electrical signal to vent the hydraulic tubing between the flow transducer and the negative pressure source whenever the switch means moves between these two positions.

8. The combination as described in claim 7, wherein the flow control system further includes

a bypass reservoir, and

a solenoid operated valve located intermediate of and interconnected by the the hydraulic tubing between the flow transducer and the negative pressure source, having a first position wherein the suspension only flows from the flow transducer to the negative pressure source, and having a second position wherein the fluid only flows from the bypass reservoir to the negative pressure source.

9. The combination of a surgical handpiece and a flow control system for removing a suspension of unwanted material in a treatment fluid from an enclosed operative site wherein said surgical handpiece comprises

a fluid inlet channel for treatment fluid to enter the enclosed operative site,

a fluid outlet channel for the suspension of unwanted material in the treatment fluid to exit from the enclosed operative site, and

a vibratory body, coupled to a source of high frequency electrical energy, for converting said electrical energy to high frequency mechanical vibrations, and coupled to a source of coolant for cooling a portion of said vibratory body, and

wherein the flow control system comprises,

a first source of treatment fluid at a certain pressure for causing said fluid to flow into the enclosed operative site, including hydraulic tubing for connecting said first treatment fluid source to the enclosed operative site,

a second source of treatment fluid at a pressure higher than the first source for causing said fluid to flow into the enclosed operative site, including hydraulic tubing for connecting said second treatment fluid source to the enclosed operative site,

a source of negative pressure for withdrawing the suspension from the enclosed operative site, including hydraulic tubing for connecting said negative pressure source to the enclosed operative site,

a flow transducer intermediate of and interconnected by the hydraulic tubing between the negative pressure source and the enclosed operative site, for sensing the flow of the suspension and for generating an electrical signal proportional to said flow,

a vent valve coupled to the hydraulic tubing between said flow transducer and said negative pressure source for venting the flow of the suspension to atmospheric pressure,

electronic flow control means electrically interconnected to said flow transducer and said vent valve for sensing certain changes rates flow rtes due to the signal received from said flow transducer and, at a certain predetermined value, for sending an electrical signal to the vent valve for venting the hydraulic tubing through which said suspension flows, and

a switch means having three positions, said first switch position coupling only the source of treatment fluid having the lower pressure to the enclosed operative site, said second switch position coupling the source of treatment fluid having the higher pressure and the negative pressure source to the enclosed operative site, and said third switch position coupling the source of treatment fluid having the higher pressure and the negative pressure source to the enclosed operative site and energizing the high frequency vibratory body; with the vent valve receiving an electrical signal to vent the hydraulic tubing between the flow transducer and the negative pressure source whenever the switch means moves between the first and second positions.