Patent Publication Number: US-2003236530-A1

Title: Adjustable fluid flow resistor

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention is related to devices for restricting the flow of aspirant during surgery, especially ophthalmic surgery. In particular, the present invention relates to devices that are adjustable so as to provide a range of aspirant flow resistance.  
       [0003] 2. Description of Related Art  
       [0004] During eye surgery, especially cataract surgery, surgeons experience a tension between the amount of vacuum or aspiration to be used on a patient&#39;s eye and the time period in which the surgeon has to respond to events that may occur during surgery. Surgeons typically prefer higher vacuum levels to provide a higher holding force for the cataract. However, these higher vacuum levels result in the need for rapid response times by the surgeon when events such as occlusion occur in the aspiration line. The higher the vacuum levels, the quicker events occur and thus the potential for serious problems increases, such as the tearing of the capsular bag.  
       [0005] There are known devices for increasing the resistance to aspirant fluid flow to allow a surgeon to use higher vacuum levels, i.e., higher holding force, with a slower response time. These devices help the surgeon have the benefits of higher vacuum levels while limiting or minimizing the risks by providing the surgeon with greater time to respond to surgical events than would be possible without resistance to the aspirant flow. Coiled tubing is one example that increases the flow resistance. It has been asserted that increased resistance is achieved by passing fluid through a series of coil bends because fluid drops in pressure as it flows through a bend. However, a downside to the coiled tubing is that the chances of aspirant clogging within the coils is increased due to the elliptical cross section and bent kinks that may occur in the tubing. In addition, the resistance of the coiled tubing is a function of the coil radius and the resistance cannot be varied during surgery.  
       [0006] Another device that increases resistance to aspirant flow is a non-clogging orifice that collects waste and is commonly referred to phaco-guard. The phaco-guard is a large cross-sectional area filter funneled down to a small orifice. It allows limited clogging of the filter and is based on the assumption that the entire filter area will not clog. The filter may still clog and it is not adjustable.  
       [0007] Therefore, it would be advantageous to have a fluid flow resistor that is adjustable to provide the surgeon with a range of aspirant flow resistance. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0008]FIG. 1 is a cross-section of an adjustable fluid flow resistor in accordance with the present invention;  
     [0009]FIG. 2 is a front elevation view of an adjustable fluid flow resistor in accordance with the present invention wherein the fluid flow resistance is at a minimum;  
     [0010]FIG. 3 is a front elevation view of an adjustable fluid flow resistor in accordance with the present invention wherein the resistor is in a position of maximum resistance to fluid flow;  
     [0011]FIG. 4 is an illustration of the use of the present invention during eye surgery.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0012]FIG. 1 shows an adjustable fluid flow resistor  10  in accordance with the present invention. The resistor  10 , which is for use in ophthalmic surgery, includes a housing  12  formed of inlet  14  and outlet  16  attached to opposing ends of tube  18 . Inlet  14  and outlet  16  are to be connected to surgical tubing for receiving aspirant from a surgical site and allowing the aspirant to pass to a container as described below. The material used to form inlet  14 , outlet  16 , and tube  18  may be any material suitable for ophthalmic surgery. Inlet orifice  20  and outlet orifice  22  are both preferably large enough in cross-section so that any aspirant flowing through attached surgical tubing will not clog in the orifices  20  and  22 . It is also to be understood that the resistor  10  could be made integral to a surgical fluid collection cassette such as are well-known in the art. If the resistor is incorporated into a cassette it may also be desirable to automate the adjustment of the flow resistance.  
     [0013] Contained within housing  12  is a first set of dividers  24 . Each of the first set of dividers  24  includes at least one aperture  26  defining a path through which aspirant may flow during surgery. Dividers  24  should preferably be sealingly attached tube  18  so that fluid and aspirant may only flow through apertures  26 .  
     [0014] A second set of dividers  28  is also contained within the housing  12 . The dividers  28  are moveable relative to the first set of dividers  24  and each of the second set of dividers  28  includes at least one aperture  30  defining a path through which aspirant may flow during surgery. Dividers  28  should also be sealingly engaged with tube  18 , but unlike stationary dividers  24 , dividers  28  are preferably rotatable within resistor  10  by manipulation of handle  31 . Of course, dividers  24  may also be made to be rotatable within resistor  10 . The dividers  24  and  28  within housing  12  are spaced apart from each other to define a plurality of aspirant chambers  29 .  
     [0015] A flow resistance of resistor  10  is at a minimum when the apertures  26  and  30  of the first and second set of dividers  24  and  28  are aligned and the flow resistance increases as the apertures  26  and  30  of the first set of dividers  24  are positioned further away from the second set of dividers  28 . The fluid flow resistor  10  of FIG. 1 is shown at a maximum resistance position, where the apertures  30  are 180° from apertures  26 .  
     [0016] Handle  31  includes arms  32  which are connected to dividers  28 . Obviously, arms  32  passing through tube  18  must be formed such that a liquid-tight seal is made between arms  32 , divider  28 , and tube  18  so that no surgical fluid escapes from resistor  10  during surgery.  
     [0017] It is preferred that the orifices  20  and  22  and the apertures  26  and  30  and the distance between the dividers  28  and  24  are all large enough such that pieces of aspirant  34  do not become clogged within resistor  10  during surgery, and are able to flow freely through resistor  10 . Said another way, each apertures  26  and  30  and the distance between each of the first and second set of dividers  24  and  28  is at least as large in cross-section as a cross-section of an inner-diameter of tubing to be connected to the inlet, thereby avoiding any possibility of aspirant occluding one of the apertures  26  and  30  or between any dividers. It is preferable for the spacing to cause turbulent flow, which is known to have higher resistance than laminar flow.  
     [0018] While the preferred embodiment shows only one aperture per divider, it is to be understood that more than one aperture could be contained in the dividers  24  and  28 . The apertures could also be notches formed in the dividers  24  and  28  or a variety of other spacings.  
     [0019] The handle  31  connected to the second set of dividers  28  allows a user to rotate the second set of dividers  28  to vary the fluid flow resistance. However, other ways of rotating the dividers can also be used. For example, a motor could be utilized for rotation or each divider could have its own independent handle. Also, other means of movement of the dividers may be used such as hinging each of the dividers or any other manner of varying the fluid flow path length. Such hinging movement is described in co-pending application entitled “Adjustable Fluid Flow Resistor Cassette, serial number (to be assigned) and is incorporated herein by reference.  
     [0020]FIG. 2 shows the aspirant flow resistor  10  positioned such that the resistance of resistor  10  is minimal. FIG. 3 shows the resistor  10  positioned at its maximum resistance where apertures  30  are rotated 180° from inlet  20  and apertures  26 . This causes aspirant to flow along line  36  as shown in FIG. 1 which creates an increased fluid flow path length from the configuration shown in FIG. 2.  
     [0021] Another way of describing the invention follows. Housing  12  has an inlet  20  and an outlet  22  for receiving a flow of aspirant fluid for a surgical site. The first and second set of dividers  24  and  28  together form a set of path restrictors, and are disposed within the housing between the inlet  20  and outlet  22 . At least some of the path restrictors are moveable within the housing, and cooperate to vary a path length  36  from the inlet to the outlet. An aspirant fluid flow resistance increases as the path length  36  increases from the inlet to the outlet.  
     [0022]FIG. 4 shows the present invention is use in ophthalmic surgery. Eye surgery  40  includes irrigation fluid  42  passing to the surgical site through tube  44  and into eye  46 . Aspirant, including for example pieces of removed cataract, and irrigation fluid  42  pass through tube  48  and into aspirant flow resistor  10  and then onto a collection reservoir  50 . The present invention allows a surgeon a great amount of control over the level of vacuum that may be used as well as the response time that will be available to respond to surgical events. Resistor  10  is easily adjusted during surgery by simply rotating handle  31  about the housing  12 .  
     [0023] Thus, there has been shown an adjustable aspirant flow resistor in accordance with the claims of the present invention. It is to be understood that changes and alterations may be made to the present invention without departing from the scope of the invention as set forth in claims. For example, dividers  28  may be rotated within the resistor  10  by use of a knob or wheel contained at one end of resistor  10  instead of the disclosed handle  31 .