Patent Grant
6955073
This invention relates generally to pressure sensors used on surgical cassettes and surgical consoles and more particularly to a method of testing the accuracy of such sensors prior to surgery.
Surgical cassettes utilized in phacoemsulsification, vitreoretinal, or other ophthalmic surgical procedures typically have an aspiration manifold within the cassette. When the cassette is inserted into an ophthalmic surgical console, the aspiration manifold is operatively coupled to a source of vacuum. The cassette is also fluidly coupled to the aspiration port of an ophthalmic surgical handpiece, typically via flexible plastic tubing. Ophthalmic tissue is aspirated by the handpiece into a collection bag that is also fluidly coupled to the aspiration manifold of the cassette. Such cassettes typically employ a variety of pressure sensors to measure the vacuum level within the aspiration manifold of the cassette and thus the eye. For example, such cassettes have utilized both conventional vacuum transducers and non-invasive pressure sensors to measure such vacuum. Exemplary non-invasive pressure sensors are disclosed in U.S. Pat. Nos. 5,910,110 to Bastable and 5,470,312 to Zanger et al., both of which are incorporated herein in their entirety by reference.
Communicating an accurate reading of the vacuum level within the aspiration manifold of such surgical cassettes to the surgeon is critical to the success of the surgical procedure and the safety of the patient. For example, during a phacoemulsification procedure, the tip of the phacoemulsification handpiece may become occluded with ophthalmic tissue. When the tip occludes, the peristaltic pump vacuum source of the surgical system continues to pump, increasing the vacuum within the aspiration line of the handpiece. When the blockage on the tip is removed, the patient's eye may be exposed to a dangerous surge of vacuum. However, if the vacuum level within the aspiration manifold of the cassette is measured and provided to the surgeon, the surgeon can use the user interface of the surgical console to slow down or stop the peristaltic pump to bring the vacuum to the desired level before the blockage breaks free. To insure that an accurate aspiration manifold vacuum reading is provided to the surgeon, certain ophthalmic surgical systems utilize two pressure sensors to measure vacuum in the aspiration manifold of the cassette. With this design, the surgeon still receives an accurate measurement of the vacuum level within the aspiration manifold of the cassette even if one of the sensors fails or is not working properly. However, such dual redundancy increases the cost and complexity of the surgical system and cassette. Therefore, a need exists for an improved apparatus and method of insuring the accuracy of such pressure sensors.
The present invention is directed to a method of determining the accuracy of a pressure sensor in a surgical console. A substantially non-compliant member is provided. A surgical console with a cassette receiving area and a linear actuator having a plunger are also provided. The substantially con-compliant member is disposed in the cassette receiving area. The linear actuator is actuated so that the plunger is linearly displaced a pre-defined amount, and the force exerted by the plunger on the non-compliant member is measured. The accuracy of the linear actuator and the plunger are determined by comparing the force measured in the measuring step to a pre-defined force.
For a more complete understanding of the present invention, and for further objects and advantages thereof, reference is made to the following description taken in conjunction with the accompanying drawings in which:
The preferred embodiments of the present invention and their advantages are best understood by referring to
Referring to
Surgical cassette 14 generally includes a body 50 having a pressure sensor receiving area 52, a non-invasive pressure sensor 54 disposed in receiving area 52, and an aspiration manifold 56 fluidly coupled to sensor 54. Body 50 is preferably a rigid thermoplastic and may be made from any suitable method, such as machining or injection molding. Although not shown if the Figures, cassette 14 may also include additional fluid channels, manifolds, or ports that provide control of aspiration or irrigation fluid. A preferred ophthalmic surgical cassette for cassette 14 is disclosed in U.S. Pat. No. 6,293,926, which is incorporated herein in its entirety by this reference.
Pressure sensor 54 has a body 58 having a cavity 60, a port 62 for fluidly coupling with aspiration manifold 56, and a diaphragm or membrane 64. Body 58 is preferably a rigid thermoplastic, and diaphragm 64 is preferably made of stainless steel. Diaphragm 64 has a rim 66 that mates with a recess 68 in body 58 to retain diaphragm 64 within body 58. Diaphragm 64 preferably has a diameter of about 0.996 inches (not including rim 66). Diaphragm 64 preferably has a thickness of about 0.0027 inches to about 0.0033 inches, and most preferably about 0.003 inches. Diaphragm 64 is preferably made of 17-7 stainless steel.
When cassette 14 is inserted into cassette receiving area 16 of console 12, computer 22 rotates stepper motor 18, causing shaft 24 and plunger 26 to be moved linearly through aperture 34 toward diaphragm 64 of sensor 54. Stepper motor 18 moves plunger 26 until it contacts and displaces diaphragm 64, as shown in
When console 12 provides vacuum to aspiration manifold 56 of cassette 14 and thus cavity 60 of sensor 54, the absolute value of the force exerted on diaphragm 64 by plunger 26 varies in an inversely proportional manner with the absolute value of the vacuum level. In other words, larger absolute values of vacuum yield smaller absolute values of force exerted by plunger 64, and smaller absolute values of vacuum yield larger absolute values of force exerted by plunger 64. This relationship may be calibrated so that when load cell 20 provides a force measurement to computer 22, computer 22 can calculate the vacuum level within cavity 60, aspiration manifold 56, and the eye.
It is critical that linear stepper motor 18, shaft 24, plunger 26, and sensor 54 cooperate together to accurately measure the vacuum within aspiration manifold 56 of cassette 14. A preferred method of testing the accuracy of sensor 54 is disclosed in U.S. Pat. No. 6,868,720, which is incorporated herein in its entirety by reference. In addition, it has been discovered that periodic testing of stepper motor 18, shaft 24, and plunger 26 is desired to insure accurate pressure sensing by this system. Such testing can be initiated when desired by the user via the user interface of surgical console 12 in conjunction with a test cassette 14a. Computer 22 may also signal the surgeon that such testing is desired based upon a pre-defined number of insertions of cassette 14 into cassette receiving area 16.
The following describes the preferred procedure for testing the accuracy of linear stepper motor 18, shaft 24, and plunger 26. A test cassette 14a is inserted into cassette receiving area 16 of console 12, as shown in
From the above, it may be appreciated that the present invention provides a simple and reliable apparatus and method of insuring the accuracy of a non-invasive pressure sensor of a surgical cassette. The present invention is illustrated herein by example, and various modifications may be made by a person of ordinary skill in the art. For example, the present invention may be implemented with other linear actuators other than linear stepper motor 18 such as a DC motor with position feedback, a pneumatically actuated piston, or other conventional means of moving a plunger with a known displacement. As another example, a substantially non-compliant member may be disposed in pressure sensor receiving area 52 without the additional structure of pressure sensor 54a. As a further example, a substantially non-compliant member may be inserted into cassette receiving area 16 instead of surgical cassette 14a having pressure sensor 54a with substantially non-compliant member 64a. As a further example, computer 22 may generate a force Fplunger versus displacement D curve for a given console 12 and substantially non-compliant member for the entire range of values of D, and then compare this curve to a “tolerance” curve in a batch mode rather than comparing each measured value of Fplunger to see if it is within the pre-defined tolerance at the time its measured, as described above. As a further example, Fplunger may be measured at intervals of a pre-defined number of steps of linear stepper motor 18 instead of at each step of linear stepper motor 18 as described above. As a further example, computer 22 may monitor the number of steps of linear stepper motor 18 required for Fplunger to equal a pre-defined force and have console 12 signal the user, or prevent any surgical procedure, if the monitored number of steps does not equal a pre-defined number of steps for the pre-defined force.
It is believed that the operation and construction of the present invention will be apparent from the foregoing description. While the apparatus and methods shown or described above have been characterized as being preferred, various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined in the following claims.
This application claims the priority of U.S. Provisional Application No. 60/418,737 filed Oct. 16, 2002.
| Number | Name | Date | Kind |
|---|---|---|---|
| 526917 | Cochran | Oct 1894 | A |
| 1718494 | Schurig | Jun 1929 | A |
| 2260837 | Kuehni | Oct 1941 | A |
| 2510073 | Clark | Jun 1950 | A |
| 2583941 | Gordon | Jan 1952 | A |
| 3805617 | Kamazuka | Apr 1974 | A |
| 4192191 | Nelson | Mar 1980 | A |
| 4281666 | Cosman | Aug 1981 | A |
| 4281667 | Cosman | Aug 1981 | A |
| 4452202 | Meyer | Jun 1984 | A |
| 4505157 | Hong Le | Mar 1985 | A |
| 4539849 | Pike | Sep 1985 | A |
| 4541283 | Stuhlmann | Sep 1985 | A |
| 4653508 | Cosman | Mar 1987 | A |
| 4658829 | Wallace | Apr 1987 | A |
| 4755669 | Grant et al. | Jul 1988 | A |
| 4886070 | Demarest | Dec 1989 | A |
| 4892985 | Tateishi | Jan 1990 | A |
| RE33360 | Reynolds et al. | Oct 1990 | E |
| RE33518 | McCord et al. | Jan 1991 | E |
| 5029478 | Wamstad | Jul 1991 | A |
| 5080098 | Willett et al. | Jan 1992 | A |
| 5095401 | Zavracky et al. | Mar 1992 | A |
| 5144843 | Tamura et al. | Sep 1992 | A |
| 5257630 | Broitman et al. | Nov 1993 | A |
| 5275053 | Wlodarczyk et al. | Jan 1994 | A |
| 5333504 | Lutz et al. | Aug 1994 | A |
| 5353633 | Benedikt et al. | Oct 1994 | A |
| 5392653 | Zanger et al. | Feb 1995 | A |
| 5460049 | Kirsch | Oct 1995 | A |
| 5460490 | Carr et al. | Oct 1995 | A |
| 5470312 | Zanger et al. | Nov 1995 | A |
| 5528214 | Koga et al. | Jun 1996 | A |
| 5583297 | Stocker et al. | Dec 1996 | A |
| 5661245 | Svoboda et al. | Aug 1997 | A |
| 5752918 | Fowler et al. | May 1998 | A |
| 5848971 | Fowler et al. | Dec 1998 | A |
| 5866822 | Willig | Feb 1999 | A |
| 5880373 | Barton | Mar 1999 | A |
| 5910110 | Bastable | Jun 1999 | A |
| 6058779 | Cole | May 2000 | A |
| 6293926 | Sorensen et al. | Sep 2001 | B1 |
| 20010004684 | Morgan et al. | Jun 2001 | A1 |
| Number | Date | Country |
|---|---|---|
| 0 579 504 | Jan 1994 | EP |
| 1 258 717 | Nov 2002 | EP |
| WO 8804042 | Jun 1988 | WO |
| WO 9324817 | Sep 1993 | WO |
| WO 0044415 | Aug 2000 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20040074282 A1 | Apr 2004 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60418737 | Oct 2002 | US |
