Abstract:
A noninvasive system and method for measuring vacuum pressure in a fluid in accordance with the present invention generally includes a chamber with two interconnected diaphragms having different surface areas and a force transducer that makes contact with the smaller area diaphragm. When a pressure level less than atmospheric occurs inside the chamber, the smaller area diaphragm presses with a force on the force sensor. As the pressure level in the chamber decreases, the force on the sensor increases. The present system is intended for, but not limited to, use in a Phacoemulsification machine, where it will serve to measure the vacuum in a fluid without contaminating the fluid with previous uses of the system or with any components of the system which are unable to undergo a sterilization process.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of 35 U.S.C. § 119 and the filing date of provisional application 61/002,038, filed Nov. 6, 2007. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention relates to the field of pressure measuring systems. More specifically, the invention relates to systems that non-invasively measure the degree of vacuum in a fluid. 
       BACKGROUND OF THE INVENTION 
       [0003]    In essence, a vacuum is a volume of space that is void of any matter such that the gaseous pressure of this volume of space is less than standard atmospheric pressure. Simply measuring the vacuum in a fluid is neither new nor novel, and the methods to do so do not need to be mentioned in this application, except to say that these prior methods, when applied to a living system, have generally been invasive in nature and therefore at times were susceptible to cross contamination of the fluids in which the vacuum is being measured. Thus, there exists a need in the art, especially in the area of ophthalmic instruments such as Phacoemulsification machines, for a more hygienic and noninvasive system to measure fluid in a vacuum. 
         [0004]    Phacoemulsification machines are used for removing cataracts, or crystalline manifestations, from the eye. The machine may include a probing device, which typically constitutes an ultrasound driven hollow needle. In such a case, the needle is inserted into the eye through a small incision in the opaque layer of tissue surrounding the pupil, and vibrates at ultrasonic frequency to emulsify any crystalline manifestations that may be present. The emulsified particles of cataract are then aspirated through an opening at the tip of the hollow needle. The aspiration process is, in a sense, two interconnected operations. The first operation of the process is the actual removal of the cataract fragmentations through the application of a vacuum pressure. During the removal of the fragmentations, there must be a continuous circulation of fluid through the eye. This is provided by the second operation, in which the hollow needle supplies this circulation of fluid. 
         [0005]    The entire process is a delicate one, as the pressure in the eye must be constantly measured and maintained to prevent a number of problems. For example, during the removal operation, any blockage in the hollow needle, possibly created during the passage of one cataract fragmentation, may cause a void, or vacuum, to build in said needle. In such an instance, it may be necessary to apply a higher level of pressure in order to dislodge the blockage. Failure to adequately measure and control the fluid pressure during this process may result in the sudden ejection of the blockage followed by a rapid influx of fluid from the eye into the void. If this fluid is not replaced with sufficient speed, it could lead to the subsequent collapse of the eye chamber. Another way to remove a blockage from the hollow needle is to reverse the flow of fluid in the needle to expel the blocking fragmentation. Again, however, if the fluid pressure is not adequately measured and controlled, the ramifications could be extremely problematic. In this situation, the vacuum pressure would be negative, so when the blockage is removed there may be a subsequent flooding of the eye chamber leading to an inflation of the eye. Furthermore, as discussed above, the use of a standard pressure measuring system to monitor these pressures is not an adequate solution to the problem, as cross contamination of fluids will then become an issue. 
         [0006]    The industry has devised a number of different systems in trying to fulfill this need for a non-invasive system of measuring vacuum in a fluid, both respective and irrespective of use with Phacoemulsification machines. However, all of these solutions have been shown to suffer from deficiencies when utilized in this application. One such system involves separating the measured fluid from another fluid, usually air or gel, with a membrane, and measuring the pressure in the other fluid. Another such system involves using an elastic element to load a force transducer, for example, pressing a tube that contained the measured fluid to a force sensor and measuring the fluid pulling force on that element using the differences between the zero atmospheric level and the vacuum level. The two aforementioned systems, though operable, suffer from increased levels of hysteresis (path dependence) and volume variance. A third method uses a diaphragm exposed on one side to the fluid and on the other side to a force transducer. The pulling force on the diaphragm is measured usually using a magnetic coupling between the diaphragm and the force sensor. However, this third system can suffer from being overly robust in construction. Thus, there still exists a need in the art for a simply constructed, noninvasive system for the measuring of vacuum pressure in a fluid that will not suffer from high levels of hysteresis or volume variance. 
       SUMMARY OF THE INVENTION 
       [0007]    A noninvasive system for measuring vacuum pressure in a fluid in accordance with the present invention generally includes a chamber with two interconnected diaphragms, having different surface areas, and a force transducer that makes contact with the smaller area diaphragm. The two different surface areas allow for a pressure differential. When a pressure level less than atmospheric occurs inside the chamber, the smaller area diaphragm presses with a force on the force sensor. As the pressure level in the chamber decreases, the force on the sensor increases. The present system is intended for, but not limited to, use in a Phacoemulsification machine, where it will serve to measure the vacuum in a fluid without contaminating the fluid with previous uses of the system or with any components of the system which are unable to undergo a sterilization process. 
         [0008]    In order to differentiate from limitations found in the prior art and to maximize the scope of the invention presently disclosed, it is one object to provide for a system that noninvasively measures vacuum pressure in a fluid. It is considered noninvasive because this system created by the body, tubing and sensor chamber never contact external instrumentation or measuring devices. This presently disclosed system is conducive to ensuring the prevention of cross contamination of fluids from previous or subsequent use. It is another object of the present invention to avoid a system that suffers from hysteresis or volume variance. A third object of the present disclosure is to provide a system that is simply constructed and a method that is easy to follow. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  illustrates an exploded view of a pressure sensor in a noninvasive system for measuring vacuum pressure in a fluid in the preferred embodiment of the present invention. 
           [0010]      FIG. 2   a  illustrates a top view of a pressure sensor chamber in the preferred embodiment of the present invention. 
           [0011]      FIG. 2   b  illustrates a bottom view of a pressure sensor chamber in the preferred embodiment of the present invention. 
           [0012]      FIG. 3   a  illustrates a top angled view of the lower piece comprising a diaphragm of smaller surface area in the preferred embodiment of the present invention. 
           [0013]      FIG. 3   b  illustrates a bottom view of the lower piece comprising a diaphragm of smaller surface area in the preferred embodiment of the present invention. 
           [0014]      FIG. 3   c  illustrates a front view of the lower piece comprising a diaphragm of smaller surface area in the preferred embodiment of the present invention. 
           [0015]      FIG. 3   d  illustrates a side profile view of the lower piece comprising a diaphragm of smaller surface area in the preferred embodiment of the present invention. 
           [0016]      FIG. 4   a  illustrates a top angled view of the upper piece comprising a diaphragm of larger surface area in the preferred embodiment of the present invention. 
           [0017]      FIG. 4   b  illustrates a bottom view of the upper piece comprising a diaphragm of larger surface area in the preferred embodiment of the present invention. 
           [0018]      FIG. 4   c  illustrates a front view of the upper piece comprising a diaphragm of larger surface area in the preferred embodiment of the present invention. 
           [0019]      FIG. 4   d  illustrates a side profile view of the upper piece comprising a diaphragm of larger surface area in the preferred embodiment of the present invention. 
           [0020]      FIG. 5  shows a cross section of the pressure sensor chamber comprising its upper and lower pieces secured into a base plate with a transducer in the preferred embodiment of the present invention. 
           [0021]      FIG. 6  shows a flowchart of a method of using the pressure sensor chamber in a noninvasive system for measuring vacuum pressure in a fluid in the preferred embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0022]    In the following description of the various embodiments, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration, various embodiments in which the invention may be practiced. It is to be understood that other embodiments may still be utilized and structural and functional modifications may be made without departing from the scope and spirit of the present invention. 
         [0023]    Referring to  FIG. 1 , an exploded view of a pressure sensor of the preferred embodiment of a system for noninvasively measuring the vacuum pressure in a fluid is shown. Pressure sensor chamber  100  is shown comprised of lower piece  30  and upper piece  40 . Lower piece  30  comprises small diaphragm  35  while upper piece  40  comprises large diaphragm  45 , whereby small diaphragm  35  and large diaphragm  45  are interconnected by diaphragm bridge  50 . In the preferred embodiment, the entire pressure sensor is less than one inch in diameter and may be ovular or circular from the top down. In this embodiment, chamber  100  is constructed of biocompatible and autoclavable silicon but it can be envisioned to be constructed either wholly or partially of plastic, rubber, glass or any other suitable material known to one of ordinary skill in the art. Force transducer  70 , which is preferred to be an industry standard force transducer, is held by a support and directly contacts small diaphragm  35 . Fluid inlet  60  and fluid outlet  65  (not shown) bookend chamber  100  and are openly connected within chamber  100  in such a way so that fluid inlet  60 , fluid outlet  65  and chamber  100  may form one continuous channel which circumscribe diaphragm bridge  50 . It should be clear to one of ordinary skill in the art that the function of fluid inlet  60  and outlet  65  are to serve as entry and exit paths for any fluid that is desired to pass through chamber  100  while the presently disclosed system for measuring vacuum pressure of a fluid is in use. 
         [0024]    During operation, a fluid will flow from fluid inlet  60  through chamber  100  and exit out of fluid outlet  65 . During this flow of fluid, small diaphragm  35  and large diaphragm  45 , which are preferably glued together at diaphragm bridge  50 , will react to variances in pressure of this fluid. When a pressure level less than atmospheric, or simply less than the pressure of the surroundings, occurs inside chamber  100  and creates a vacuum, small diaphragm  35  will exert a force on force transducer  70 . As the pressure in chamber  100  decreases relative to the surroundings, the force on transducer  70  increases proportionally. Therefore, the disclosed system will immediately be able to detect changes in the pressure of any fluid within chamber  100 , while eliminating the risk of cross contamination from prior uses by keeping many of the requisite elements external. This allows for minimal sterilization to be necessary between uses. It should also be apparent to one of ordinary skill in the art that the ability of fluid to freely flow through chamber  100  will reduce problems that may be caused by hysteresis or volume variance. 
         [0025]    Now referring to  FIG. 2   a , a top view of the entire pressure sensor chamber of the preferred embodiment of a system for noninvasively measuring the vacuum pressure in a fluid is shown. Inlet wing  20  and outlet wing  25  on lower piece  30  can be viewed extending out beyond upper piece  40 . Large diaphragm  45  can best be viewed from this angle, having a preferable surface area of approximately three times smaller diaphragm  35  (not shown). Although, any difference in surface areas will allow the presently disclosed sensor to function. Ribbed crease  48  can also be seen surrounding large diaphragm  45  which allows for movement while in use. The normal stiffness of ribbed crease  48  is very slight and can be tared when computing measurements. Also, the position of ribbed crease  48  is indented slightly below the surface plane of upper large diaphragm  45  and upper piece  40 . This positioning allows upper piece  40  and lower piece  30  to fit snugly together. 
         [0026]    Now referring to  FIG. 2   b , a bottom view of the entire pressure sensor chamber of the preferred embodiment of a system for noninvasively measuring the vacuum pressure in a fluid is shown. Again, inlet wing  20  and outlet wing  25  on lower piece  30 , which house fluid inlet  60  and fluid outlet  65  respectively, can be viewed extending outward. Small diaphragm  35  can best be viewed from this angle. Depending on its size, small diaphragm  35  may or may not expand in a radial stepping manner before reaching ribbed crease  38  for support purposes. Ribbed crease  38  is preferably smaller in diameter than ribbed crease  48 , in  FIG. 2   a , but it provides the same minimal rigidity. Ribbed crease  38  similarly extends into chamber  100  and below the plane of lower piece  30 . 
         [0027]    Now referring to  FIG. 3   a , a top angled view of the lower piece comprising a diaphragm of smaller surface area in the preferred embodiment of the present invention is shown. Lower piece  30  can be seen in more detail from this inward view which comprises inlet wing  20 , fluid inlet  60 , outlet wing  25 , fluid outlet  65 , small diaphragm  35  and diaphragm bridge  50 . It can easily be seen that the fluid path crosses only through lower piece  30 , but it could be envisioned to conduct fluid through chamber  100  in any fashion that creates this continuously sealed cavern. 
         [0028]    Now referring to  FIG. 3   b , a bottom view of the lower piece comprising a diaphragm of smaller surface area in the preferred embodiment of the present invention is shown. Besides inlet and outlet wings  20 ,  25 , this view showcases ribbed crease  38 , described infra. It should be pointed out that in the preferred embodiment of the present disclosure, small diaphragm  35  actually extends beyond the plane of lower piece  30 , which can more easily be seen in the front and side profile views of  FIGS. 3   c  and  3   d . In  FIG. 3   c , fluid outlet  65  is turned to face out, while in  FIG. 3   d , outlet wing  25  can be seen facing left. An important significance to  FIGS. 3   a - d  is that lower piece  30  is thicker than upper piece  40 , so as to offer a cup-like shape in this embodiment. 
         [0029]    Now referring to  FIG. 4   a , a top angled view of the upper piece comprising a diaphragm of larger surface area in the preferred embodiment of the present disclosure is shown. As previously described, upper piece  40  comprises large diaphragm  45 . 
         [0030]    Now referring to  FIG. 4   b , a bottom view of the upper piece comprising a diaphragm of larger surface area in the preferred embodiment of the present disclosure is shown. In this embodiment, larger diaphragm  45  converges on the underside to form cone shaped diaphragm bridge  50 . Although bridge  50  can be found on both upper piece  40  and lower piece  30 , it combines to form one structure when the pieces are assembled together by methods known in the art. 
         [0031]    Now referring to  FIGS. 4   c  and  4   d , a front view and side profile view of the upper piece comprising a diaphragm of larger surface area in the preferred embodiment of the present disclosure is shown. The conical shape of the upper portion of bridge  50  can easily be seen from this angle. Also locking rung  55 , which aids in making a snug connection is shown elevated above upper piece  40 . 
         [0032]    Now referring to  FIG. 5 , a cross section of the chamber comprising its upper and lower pieces is shown. Chamber  100  can be seen resting atop force transducer  70 . Force transducer  70  in turn sits on base plate  72  and is secured by clamps  74  using clamp screws  76 . This view best shows how the system presently described can be used in conjunction with many types of medical and surgical devices, including but not limited to Phaco-emulsification machines. 
         [0033]    Now referring to  FIG. 6 , a flowchart of one method of using the pressure sensor chamber in a noninvasive system for measuring vacuum pressure in a fluid in the preferred embodiment of the present disclosure is shown. In step  91 , a Phacoemulsification machine connected by tubing to the system presently described is used to dissolve a cataract from an eye. In step  92 , any fluid, such as saline solution is used to wash and maintain pressure in the eye. The fluid is then sucked to the presently disclosed system through fluid inlet  60 . In step  92 , the vacuum pressure of the fluid is measured from a transducer in contact with smaller diaphragm  35 . In step  94 , the system continuously allows fluid to flow through chamber  100  and back to the eye through fluid outlet  65 . In step  95 , the system compensates for affected pressure readings by increasing suction force and/or instantaneously reversing suction force until the blockage is cleared. If the pressure reading remains unaffected, no change occurs. After step  95 , the system continues to measure and maintain the pressure of fluid in the eye until the operation procedure is accomplished. 
         [0034]    The present invention includes any novel feature or combination of features disclosed herein either explicitly or any generalization thereof. While the invention has been described with respect to specific examples including presently preferred modes of carrying out the invention, those skilled in the art will appreciate that there are numerous variations and permutations of the above described apparatus. Thus, the spirit and scope of the invention should be construed broadly as set forth in the previous specification or appended claims.