Fluid pressure sensing chamber

[0001] The present invention generally relates to fluid pressure sensing chambers, and more particularly to fluid pressure sensing chambers used in ophthalmic surgical equipment.

[0002] When age or disease causes the lens to become less transparent, vision deteriorates because less light can be transmitted to the retina. This failure of the eye lens is known in medicine as a cataract. The accepted treatment for this condition is surgical removal of the lens and replacement by an artificial intraocular lens (IOL) that performs this function.

[0003] In the United States, most cataract-affected lenses are removed by a surgical technique called phacoemulsification (lens emulsification). When performing this procedure, a thin phacoemulsification cutting tip is inserted into the diseased lens and subjected to ultrasonic vibration. The vibrating cutting tip liquefies or emulsifies the lens so that it can be aspirated from the eye. The diseased lens, after removal, is replaced by an artificial lens.

[0004] A typical ultrasonic surgical device for ophthalmic procedures consists of an ultrasonic driven handle, an attached cutting tip, an irrigation sleeve and an electronic control console. The handle assembly is connected to the control console by an electric cable and flexible tubes. Through the electric cable, the console changes the level of power transferred by the handle to the attached cutting tip, while the flexible tubes deliver irrigation fluid to the eye and suck fluid from the eye using the handle assembly.

[0005] The operating part of the handle is a centrally located, hollow resonance rod or tube, directly attached to the piezoelectric crystal set. The crystals provide the desired ultrasonic vibrations needed to drive both the tube and the attached cutting tip during phacoemulsification and they are controlled by the console. The crystal / tube assembly is suspended inside the hollow body or handle shell using a flexible suspension. The handle body ends in a reduced diameter part or conical end at the distal end of the body. The conical end is externally threaded to receive the irrigation sleeve. Similarly, the hole in the tube is internally threaded at its distal end to receive the external thread of the cutting tip. The irrigation sleeve also has an internally threaded hole that is screwed onto the outer thread of the conical end. The cutting tip is positioned so that it projects only within a predetermined range beyond the open end of the irrigation sleeve.

[0006] In use, the ends of the cutting tip and irrigation sleeve are inserted into a small incision, of predetermined width, in the cornea, sclera or other location. The cutting tip is subjected to ultrasonic vibrations along its longitudinal axis w

Irrigation sleeve through a crystal-driven ultrasound tube, resulting in emulsification of the selected tissue in situ. The hollow hole of the cutting tip connects to the hole in the tube, which in turn connects to the suction line from the handle to the console. A source of reduced pressure or vacuum, usually a peristaltic pump, in the console pulls out or sucks the emulsified tissue from the eye through the open end of the cutting tip, holes of the cutting tip and tubes, and a suction line up to the collecting device. Suction of emulsified tissue is assisted by flushing with saline solution or irrigation fluid, which is injected into the surgical site through a small annular gap between the inner surface of the irrigating sleeve and the cutting tip.

[0007] Prior art devices have used sensors that detect purge pressure or aspiration vacuum. Based on information from these sensors, the surgical console can be programmed to respond to make the surgical procedure more effective and safer. To reduce the risk of contamination by aspirated fluid, the latest surgical systems use closed pressure sensors in which the fluid does not come into contact with the sensor working element or other fluid pressure sensing device. One such pressure sensor is illustrated in US Patent 5,392,653 (Zanger, et al.). The overall performance of such closed pressure sensors, however, depends significantly on removing all air from the system. Air is much more compressed than the irrigation solution used in surgery, and plugs or air bubbles increase system compliance. Compliance results from undesirable changes in pressure and fluctuation. Commonly known methods for removing air from sealed fluid systems (or "flooding" the system) include avoiding sharp edges and sharp shape changes in the system, as well as filling the system with fluid from the bottom or from the lowest point of the system. This allows air to escape through the top of the system as the system is filled with fluid from below. The inventors have found that pre-priming the chambers of a pressure sensor located in closed fluid surgical systems is relatively easy, but if air bubbles can enter the chamber (e.g., if the surgical handle is replaced during the procedure), these air bubbles are extremely difficult to remove from the system. This difficulty is due to the surface tension of the air bubble (in contrast to air that has not been enclosed in bubbles, usually associated with the initial flooding of the system), which makes the bubble quite durable and it is not easy to break and pull out of the pressure detection chamber immediately after introduction. In addition, the "film" of fluid surrounding the air bubble is sticky, which causes the bubble to stick or adhere to the surface inside the system and resist further movement, even at very fast flow rates. One document, US Patent 6,059,765 (Cole et al.), Suggests that certain chamber shapes and the location of the outlet may assist in the evacuation of air from surgical systems. The inventors have found that the shapes and constructions of the chambers discussed in this document are insufficient to ensure the evacuation of air bubbles from the system.

[0008] US-2005/186098 (Davis Sherman G., et al.) Describes a cassette having the features according to the preamble of claim 1 below, in which the cassette integrally

The shaped extension of the tubing passes through the bottom of the cavity formed in the pressure sensing chamber and has a centrally located vent outlet.

[0009] Accordingly, there is still a need for a pressure sensing chamber that prevents air from entering the chamber and closing it inside the chamber.

Brief Summary of the Invention [0010] The present invention as defined in claim 1 is an improvement over prior art peristaltic pumps by providing a pressure sensing chamber having a tubular extension with a reduced diameter portion extending through the chamber in accordance with the claims given below. The tubing has many through holes to allow air to escape from the chamber.

[0011] The reduced diameter part produces a pressure difference between the holes. This pressure difference causes flow through the chamber at high fluid flow rates and turbulent flow cases.

[0012] One of the objects of the present invention is to provide a cartridge, a pressure sensing chamber, which can be easily flooded.

[0013] Another object of the present invention is to provide a pressure sensing chamber that does not allow air bubbles to be caught in the chamber.

[0014] Still another object of the present invention is to provide a pressure sensing chamber having a tubing extending through the chamber.

[0015] These and other advantages and objects of the present invention will become apparent from the detailed description, drawings and claims that follow.

Brief description of the drawings [0016]

Fig. 1 is a perspective view of a surgical system that can be used with the present invention;

Fig. 2 is a perspective view of a surgical cassette that can be used with the present invention;

Fig. 3 is an enlarged perspective view of a first embodiment of a pressure sensing chamber according to the present invention;

Fig. 4 is an enlarged perspective view of a second embodiment of a pressure sensing chamber according to the present invention.

Detailed Description of the Invention [0017] As best seen in Fig. 1, commercially available surgical systems typically include a surgical console 110 that has an adjustable shelf 10 attached and handle 20 attached to console 110 via aspiration tube 22, irrigation tube 24, and power cable 26. Energy for handle 20 as well as irrigation and suction fluid flows are controlled by console 110, which includes appropriate hardware and software such as power supplies, pumps, pressure sensors, valves, and all of this is known in the art. As best seen in Fig. 2, the cassette 200, which can be used with the present invention, adopts aspiration tube 22 and irrigation tube

-424, and is installed in the cassette receiving portion 200 of the console 110. The cassette 200 includes a pressure sensing chamber 210 that may include a hollow opening 230 formed in the body 220 of the cassette 200 and closed by a pressure sensing membrane 215. Cassette 200 can_® be any of a variety of commercially available surgical cassettes such as INFINITI^® Fluid Management System, available from Alcon Laboratories, Inc., Fort Worth, Texas. The body 220 is usually formed of a suitable thermoplastic material.

[0018] As best seen in Fig. 3, the chamber 210 includes a tubing extension 240 that passes through the hollow opening 230, essentially dividing this opening in half into two identical hemispheres, although other shapes than the chamber 210 and the hollow opening 230 may be used The tubing extension may be integrally formed in the body 220 or may be integrally formed with the suction tube 22. In any case, the tubing extension 240 connects seamlessly to the suction tube 22 in such a way as to draw fluid through the suction tube 22 into the peristaltic pump 250, as indicated by the flow arrows in Fig. 3. Passing through the tube extension 240 there are one or more holes 260 that allow fluid communication between the suction tube, 22, the hollow hole 230 and the membrane 215. This fluid communication allows the pressure in the suction tube 22 to change in pressure to connect to the hollow opening 230 causing deformation of the membrane 215 which can be detected by a load cell (not shown) mounted inside the console receiving portion 25. Holes 260 also allow the hollow opening 230 air removal during initial priming of cassette 200. More importantly, the holes 260 are so dimensioned and shaped that no air bubbles entering the suction line 22 can easily pass through the holes 260 and enter the hollow hole 230. The arrangement and dimensions of the hole (holes) 260 support good bubble retention tubing extensions 240, while allowing fluid to flow through the bottom opening (s) 260 during fluid pre-filling the hollow hole 230.

[0019] As best seen in Fig. 4, to assist in pre-filling the hollow hole 230 'with fluid, the internal dimension of the tubing extension 240' may have a reduced diameter portion 241 to cause flow restriction through the tubing extension 240 '. This flow restriction assists the flow of fluid during pre-filling of the hollow hole 230 'through the hole (s) 260' below the constriction 242. The flow narrowing 242 within the tubing extension 240 'also generates a pressure difference between the opening (holes) 260' 'above the narrowing 242 and the opening (holes) 260' below the narrowing 242. This pressure difference causes fluid to flow through the hollow opening

230 'with increased flow rate and the appearance of turbulent flow. For example,₂ holes 260, 260 'and 260' 'have a surface area of ​​0.129 mm² (0.0002 square inch) ₂ up to 12.9 mm² (0.02 square inches). This precise dimensioning of the 260, 260 'and 260' 'holes prevents the passage of air bubbles and sucked tissue through the 260, 260' and 260 '' holes due to the surface tension of the bubbles. The liquid film surrounding the air bubbles suspended in the liquid is extremely durable and very resistant to

-5 piercing or cracking. Thus, the small size of the 260, 260 'and 260' 'holes prevents any air bubbles from passing through the 260, 260' and 260 '' holes. Furthermore, during use, negative pressure (negative pressure) is usually caused in the suction lines 22 and 22 'and elongations 240 and 240' of the tubing due to the operation of the pump 250. As a result of this vacuum, very little, if any, fluid escapes from the tubing extension to the hollow hole 230 and 230 '. Therefore, in fact, no fluid flows into the hollow hole 230 and 230 'that could carry any air bubbles into the hollow hole 230 and 230'.

[0020] This description is given for illustrative and explanatory purposes. It will be understood by those skilled in the art that modifications can be made to the invention described herein without departing from its scope as defined in the claims.