Abstract:
In a peristaltic aspiration pump, a plurality of rollers are equally spaced apart from a rotating shaft and rotatable about the rotating shaft. The rollers sequentially compress and occlude an aspiration tube to generate a vacuum pressure within the aspiration tube. An irrigation-aspiration apparatus aspirates tissue to be removed together with an irrigation fluid supplied to an operated part via the aspiration tube, using the peristaltic aspiration pump. The peristaltic aspiration pump is driven under control to change the travelling speed of the roller in accordance with statuses of occluding the aspiration tube.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an irrigation-aspiration apparatus that supplies an irrigation fluid into an operated part (an affected part) and which aspirates the supplied irrigation fluid together with tissue to be removed from the affected part, and more particularly to a mechanism suitable for attenuating the pulsation (ripple) arising owing to a peristaltic aspiration pump (suction pump). 
     An irrigation-aspiration apparatus is known that supplies an irrigation fluid into an affected part and which aspirates the supplied irrigation fluid together with tissue to be removed from the affected part. For example, it is used in cataract surgery or vitreous surgery in the ophthalmic field. 
     In the irrigation-aspiration apparatus for use in these surgeries, a hand-piece is used to aspirate the supplied irrigation fluid together with the tissue to be removed from the affected part within the eyeball. The removed tissue is drawn in through an aspiration hole at the distal end of the hand-piece tip together with the supplied irrigation fluid by using a vacuum pressure (an aspiration pressure) generated by an aspiration pump (a suction pump) and thereafter drained through an aspiration tube connecting to the hand-piece into the inside of a drainage bag. A peristaltic aspiration pump is typically used as the aspiration pump which aspirates the tissue to be removed. 
     In the peristaltic aspiration pump, as shown in FIG.  6 ( a ), a plurality of pump rollers  52  are disposed on the same circumference (spaced apart at equal distance around a rotating shaft  55 ) on a rotating plate (a rotating support)  51 . When the rotating plate  51  revolves, the rollers  52  compress and occlude an aspiration tube  54  placed between an aspiration pump  50  and a tube receptacle (tube retainer)  53  as the pump rollers  52  rotate. The fluid in the aspiration tube  54  is pushed forward in the direction in which the pump rollers  52  rotate, thereby producing a vacuum pressure. 
     The peristaltic aspiration pump constructed as described above, however, encounters the following problem: During a first status lasting from a condition in which one of the pump rollers  52  starts compressing and occluding the aspiration tube  54  to a condition in which the one pump roller  52  completely occludes the aspiration tube  54 , the area of flow passage within the aspiration tube  54  is reduced, and consequently the quantity of aspiration flow and thus the flow rate of aspiration flow is decreased. Thereafter, during a second status lasting from the condition in which the one pump roller  52  completely occludes the aspiration tube  54  to the condition in which another subsequent one of the pump rollers  52  starts compressing and occluding the aspirating tube  54 , the aspiration tube  54  is released from the one pump roller  52  and restored by own resilience to increase the area of flow passage within the aspiration tube  54 . Consequently, the flow rate in the direction in which the pump rollers revolve is increased, and the quantity of aspiration flow is increased. Since the decrease and increase in quantity of aspiration flow associated with the first and second statuses are repeated, there occur periodic sinusoidal fluctuations in vacuum pressure or quantity of aspiration flow, which is called pulsation, as shown in FIG.  6 B. This pulsation may cause pressure variations in the eye under operation, occasionally making it difficult to achieve correct control in the vacuum pressure and the quantity of aspiration flow. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished in the light of the above-mentioned problem, and has, as an object, providing an irrigation-aspiration apparatus which is capable of suppressing the pulsation caused by a peristaltic aspiration pump to thereby secure a stable vacuum pressure and stable quantity of aspiration flow. 
     In order to solve the above-mentioned problems, the present invention provides the following configuration. 
     1. An irrigation-aspiration apparatus for supplying an irrigation fluid to a subject part under operation and aspirating the supplied irrigation fluid and tissue removed from the subject part, the apparatus comprising: 
     an aspiration tube through which the supplied fluid and the removed tissue is aspirated and disposed of; 
     a peristaltic aspiration pump having a plurality of rotatable rollers that travel to compress and occlude the aspiration tube to thereby generate a vacuum pressure in the aspiration tube; and 
     control means for driving and controlling the peristaltic aspiration pump to vary a travelling speed of the roller in accordance with statuses of occluding the aspiration tube. 
     2. The apparatus of 1, wherein the control means drives and controls the peristaltic aspiration pump so that the travelling speed is increased during a first status lasting from a condition in which one of the rollers first starts occluding the aspiration tube and to a condition in which the one roller occludes the aspiration tube substantially completely, and the travelling speed is decreased during a second status lasting from the condition in which the one roller occludes the aspiration tube substantially completely to a condition in which a subsequent one of the rollers starts occluding the aspiration tube. 
     3. The apparatus of 2, wherein the control means drives and controls the peristaltic aspiration pump so that the travelling speed presents a substantially square wave form. 
     4. The apparatus of 2, wherein the control means drives and controls the peristaltic aspiration pump so that the travelling speed presents a substantially sinusoidal form. 
     5. The apparatus of 1, wherein the rollers are arranged equidistantly from a rotational axis, and rotatingly travel about the rotational axis. 
     6. An irrigation-aspiration apparatus for supplying an irrigation fluid to a subject part under operation and aspirating the supplied irrigation fluid and tissue removed from the subject part, the apparatus comprising: 
     an aspiration tube through which the supplied irrigation fluid and the removed tissue is aspirated and disposed of; 
     a peristaltic aspiration pump having a plurality of rotatable rollers that travel to compress and occlude the aspiration tube to thereby generate a vacuum pressure in the aspiration tube; and 
     control means for driving and controlling the peristaltic aspiration pump to vary a travelling speed of the roller in accordance with a travelling rotation angle of the roller. 
     7. The apparatus of 6, wherein the control means drives and controls the peristaltic aspiration pump so that the travelling speed is increased once and decreased once when one of the rollers travels by a predetermined amount of the travelling rotation angle. 
     8. The apparatus of 7, wherein the predetermined amount of the travelling rotation angle is determined depending on the number of the rollers provided in the peristaltic aspiration pump. 
     9. The apparatus of 7, wherein the control means drives and controls the peristaltic aspiration pump so that the travelling speed presents a substantially square wave form. 
     10. The apparatus of 7, wherein the control means drives and controls the peristaltic aspiration pump so that the travelling speed presents a substantially sinusoidal form. 
     11. The apparatus of 6, wherein the rollers are arranged equidistantly from a rotational axis, and rotatingly travel about the rotational axis. 
     12. An irrigation-aspiration apparatus for supplying an irrigation fluid to a subject part under operation and aspirating the supplied irrigation fluid and tissue removed from the subject part, the apparatus comprising: 
     an aspiration tube through which the supplied irrigation fluid and the removed tissue is aspirated and disposed of; 
     a peristaltic aspiration pump having a plurality of rotatable rollers that travel to compress and occlude the aspiration tube to thereby generate a vacuum pressure in the aspiration tube; and 
     control means for driving and controlling the peristaltic aspiration pump to vary a travelling speed of the roller in conformity with variations in vacuum pressure or quantity of aspiration flow. 
     13. The apparatus of 12, wherein the control means drives and controls the peristaltic aspiration pump so that, if the vacuum pressure or the quantity of the aspiration flow is varied to be smaller, the travelling speed is larger, and if the vacuum pressure or the quantity of the aspiration flow is varied to be larger, the travelling speed is smaller. 
     14. The apparatus of 13, wherein the control means drives and controls the peristaltic aspiration pump so that, if the vacuum pressure or the quantity of the aspiration flow is minimal, the travelling speed is the largest, and if the vacuum pressure or the quantity of the aspiration flow is maximum, the travelling speed is the smallest. 
     15. The apparatus of 13, wherein the control means drives and controls the peristaltic aspiration pump so that the travelling speed presents a substantially square wave form. 
     16. The apparatus of 13, wherein the control means drives and controls the peristaltic aspiration pump so that the travelling speed presents a substantially sinusoidal form. 
     17. The apparatus of 12, wherein the rollers are arranged equidistantly from a rotational axis, and rotatingly travel about the rotational axis. 
     The present disclosure relates to the subject matter contained in Japanese patent application Nos. Hei. 11-285309 (filed on Oct. 6, 1999), and 2000-278688 (filed on Sep. 8, 2000), which are expressly incorporated herein by reference in their entirety. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of the essence of an irrigation-aspiration apparatus according to an embodiment of the present invention. 
     FIG. 2 is a schematic view of the essence of a peristaltic aspiration pump. 
     FIG. 3 is an explanatory view of the drive control of the aspiration pump. 
     FIG. 4 is an explanatory view of a modification of the drive control of the aspiration pump. 
     FIG. 5 is an explanatory view of a modification of the arrangement of the pump rollers. 
     FIG. 6 is a schematic view of the essence of a typical peristaltic aspiration pump. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An irrigation-aspiration apparatus for use in cataract surgery according to one embodiment of the present invention will be described below with reference to accompanying drawings. FIG. 1 is a schematic view showing the arrangement of an irrigation-aspiration apparatus of the embodiment. 
     An irrigating bottle  1  filled with an irrigation fluid is hung on an irrigation pole  2 . The irrigation pole  2  is vertically moved by a vertically moving device  12  in accordance with the height that is set for the pole  2  by an input device  11 . The height of the bottle  10  is changed by the up/down movement of the irrigation pole  2  so as to adjust an irrigation pressure. 
     The irrigation fluid from the irrigation bottle  1  passes through an irrigation tube  3  to be supplied to the patient&#39;s eye E via an operation handpiece  5  held by a surgeon. A control valve  4  is provided midway of the irrigation tube  3 , and opened or closed to control the outflow of the irrigation fluid. In this embodiment, as the operation handpiece  5 , a US handpiece is used, which emulsifies and aspirates an opaque and hardened nucleus of a lens due to cataract using ultrasonic vibrations of a cutting tip  5   a  provided at the distal end. Ultrasonic vibrations of the cutting tip  5   a  are generated by applying electric power to a ultrasonic vibrator within the handpiece  5  via a power cable  13 . 
     The handpiece  5  is connected to one end of a flexible irrigation tube  6 . Provided midway of the rearward section of the aspiration tube  6  are a connecting section  16  connecting to a pressure sensor  15 , and a peristaltic aspiration pump (suction pump)  7 . Also, the aspiration tube  6  is in communication via a bypass tube  17  to the irrigation tube  3 . The control valve  18  controls the flow out of the bypass tube  17 . The pressure sensor  15  normally detects a vacuum pressure (an aspirating pressure) When the vacuum pressure rises above a preset value, the control valve  18  is opened under the control of a control unit  10 , as required, so that the irrigation fluid is passed from the irrigation tube  3  via the bypass tube  17  into the aspiration tube  6 , thereby decreasing the vacuum pressure. The upper limit of vacuum pressure is set by switch operation of the input device  11 . 
     The irrigation fluid and the removed tissue are sucked through an aspiration hole provided at the distal end of the cutting tip  5   a  of the handpiece  5 , and drained via the aspiration tube  6  and the aspiration pump  7  into a drainage bag  8 . The control unit  10  controls the drive of the aspiration pump  7  to adjust the vacuum pressure, based on a signal depending on foot position of a foot switch  14  or a preset value input from the input device  11 . 
     The aspiration pump  7  comprises a rotating plate (a rotating support)  20 , four pump rollers  21  which are disposed rotatably on the circumference of the rotating plate  20  (spaced apart at equal distance with respect to the rotating shaft  24 ), and a tube receptacle (a tube retainer)  22 , as shown in a schematic view of the essence of the peristaltic aspiration pump of FIG.  2 . The tube receptacle  22  is vertically movable by the operation of a lever  23 , so that the aspiration tube  6  can be readily placed between the aspiration pump  7  and the tube receptacle  22 . When the rotating plate  20  revolves, the four pump rollers  21  travel to sequentially compressing and occluding the aspiration tube  6  while rotating. This operation causes the movement of the fluid in the aspiration tube  6 , thereby imparting the vacuum pressure. 
     The drive control for the aspiration pump  7  to attenuate the pulsation in the irrigation-aspiration apparatus having the above-described configuration will be described with reference to an explanatory view of the drive control for the aspiration pump  7  as shown in FIG.  3 . FIG. 3A is a view for explaining drive positions of the pump roller  21  when the pump roller  21  compresses and occludes the aspiration tube  6 . FIG. 3B is a view showing the periodical changes in the travelling speed (or rotation speed of the rotating plate) V at which the pump roller  21  rotates. FIG. 3C is a view showing the periodical changes in the vacuum pressure P. The changes in vacuum pressure of the peristaltic aspiration pump which rotates at steady (constant) rate are indicated by the dot-line in FIG.  3 C. 
     As shown in FIG. 3A, during a first status lasting from a position A where a pump roller  21  starts compressing and occluding the aspiration tube  6  to a position B where the pump roller  21  first completely occludes (completely closes) the aspiration tube  6 , the flow passage of the aspiration tube  6  in the handpiece  5  side is gradually narrowed. Accordingly, during the first status in which the pump roller  21  travels in this section between the positions A and B, the quantity of aspiration flow decreases gradually. When the pump roller  21  reaches the position B, the quantity of aspiration flow is minimal and the vacuum pressure is the lowest. 
     On the other hand, during a second status lasting from the position B where the pump roller  21  first completely occludes the aspiration tube  6  to a position C where a subsequent pump roller  21  starts compressing and occluding the aspiration tube  6  to(the subsequent pump roller  21  reaches the position A), the aspiration tube  6  is released from the pressure of the pump roller  21  and restored due to own resiliency, and the flow passage of the aspiration tube  6  in the handpiece  5  side is gradually made larger. Accordingly, during the second status in which the pump roller  21  travels in this section between the positions B and C, the quantity of aspiration flow increases gradually. When the pump roller  21  reaches the position C, the quantity of aspiration flow is maximum and the vacuum pressure is the greatest. The above operation is repeated so that a vacuum pressure is produced continuously within the aspiration tube  6 . 
     Considering the variations in vacuum pressure caused by the positional relation of the pump roller  21 , as described above, the control unit  10  controls the travelling speed of the pump roller  21  (i.e. the rotational speed of the rotating plate  20 ) V to vary as shown in FIG.  3 B. That is, during the first status in which the pump roller  21  rotatingly travels in the section A-B, since the quantity of aspiration flow decreases gradually as described above, the control unit  10  gradually increases the travelling speed of the pump roller  21  to reach the maximum travelling speed at the position B. In the section A-B, since compressing and occluding the aspiration tube  6  will cause the gradual reduction in the vacuum pressure, the control unit  10  increases the travelling speed of the pump roller  21  to suppress the reduction in the vacuum pressure. 
     On the other hand, during the second status in which the pump roller  21  rotatingly travels in the section B-C, since the quantity of aspiration flow increases gradually, the control unit  10  gradually decreases the travelling speed of the pump roller  21  to reach a minimum travelling speed at the position C. In the section B-C, since the aspiration tube  6  is restored gradually and therefore the quantity of aspiration flow is made large to increase the vacuum pressure, the travelling speed of the pump roller  21  is reduced, thereby suppressing abrupt rise in the vacuum pressure. 
     As described above, the travelling speed of the pump roller  21  is controlled to present a substantially sinusoidal form in accordance with the statues where the pump roller  21  compresses and occludes the aspiration tube  6 , that is, in accordance with fluctuations of a sinusoidal form in the vacuum pressure (the quantity of aspiration flow) associated with the rotating travel of the pump rollers  21 . By this control, the fluctuations in vacuum pressure can be suppressed, as indicated by the solid line of FIG. 3C, and thus the changes in pressure within the eye under surgery can be reduced. 
     The travelling speed of the pump roller  21  may be controlled to present a substantially square wave (pulse wave) form in accordance with the statues where the pump roller  21  compresses and occludes the aspiration tube  6 , that is, in accordance with fluctuations in the vacuum pressure (the quantity of aspiration flow) associated with the rotating travel of the pump rollers  21 . This control can also suppress the fluctuations in vacuum pressure. 
     Under the control by the control unit  10 , the travelling speed of the pump rollers  21  (the rotation speed of the rotating plate  20 ) V is changed as shown in FIG.  4 A. That is, during the first status in which the pump roller  21  rotatingly travels in the section A-B, since the quantity of aspiration flow gradually decreases, the control unit  10  increases (or speeds up) the travelling speed of the pump roller  21  to a speed higher by a certain amount than a predetermined reference speed. Conversely, during the second status in which the pump roller  21  travels in the section B-C, since the quantity of aspiration flow gradually increases, the control unit  10  reduces (or speeds down) the travelling speed of the pump roller  21  to be the predetermined reference speed. This control can suppress the fluctuations in vacuum pressure, and the changes in pressure within the eye under surgery. 
     If such a quantity of aspiration flow is obtained as to be greater than an average quantity of aspiration flow obtained by an average travelling speed of the pump roller  21 , the reference speed alone may be increased as shown in FIG. 4B, or the reference speed and the increased travelling speed may be both increased. 
     The travelling speed of the pump roller  21  can be changed in accordance with the positions of the travel or the angles of rotation in conformity with statuses of occluding the aspiration tube, i.e. fluctuations in vacuum pressure (quantity of aspiration flow). For example, in the case where a pulse motor with a full step of 1.8° is used to rotate the shaft  24  secured to the rotating plate  20 , the travelling speed of the pump roller  21  can be readily controlled in accordance with the angle of rotation, because the pulse motor is rotated 0.45° per pulse. 
     For example, in the case where four pump rollers  21  are arranged, it suffices that the travelling speed of the pump roller  21  is increased or decreased repetitively, every time the pump roller  21  rotates about 45° (including about ±5°). In other words, the travelling speed is increased once and decreased once as one cycle during the travelling rotation angle of 90° (360°/4: number of pump rollers) of the pump roller  21  (if the pump roller  21  travels at the increased travelling speed during the travelling rotation angle of 42°, the pump roller  21  travels at the decreased travelling speed during the travelling rotation angle of 48°). Similarly, in the case where six pump rollers  21  are arranged, it suffices that the travelling speed of the pump roller  21  is increased or decreased repetitively, every time the pump roller  21  rotates about 30° (including about ±5°). In other words, the travelling speed is increased once and decreased once as one cycle during the travelling rotation angle of 60° (360°/6: number of pump rollers) of the pump roller  21  (if the pump roller  21  travels at the increased travelling speed during the travelling rotation angle of 27°, the pump roller  21  travels at the decreased travelling speed during the travelling rotation angle of 33°) In this way, the control unit  10  can control and change the travelling speed in accordance with the travelling rotation angle easily regardless of the number of pump rollers  21 . 
     In this embodiment, the pump rollers  21  travels to rotate about the rotating shaft  24 . However, the travelling of the pump rollers  21  may include linear motion as shown in FIG.  5 . Of course, the number of pump rollers is not be limited to four. 
     As described above, the pulsation produced by a peristaltic aspiration pump can be suppressed, and the fluctuations in pressure within the eye under surgery can be reduced. Also, stable vacuum pressure and stable quantity of aspiration flow can be obtained.