Patent Document

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a medical device for performing thoracentesis, and more particularly to a thoracentesis device which is used for the removal of fluid from the pleural cavity. More specifically, the present invention relates to a thoracentesis device having a hyper-sensitive dual spring detection mechanism that greatly reduces the possibility of lung puncture or laceration by the device during thoracentesis. 
     2. Prior Art 
     Thoracentesis involves the removal or evacuation of fluid from the pleural cavity between the lungs and the chest wall of a patient who has sustained some kind of trauma to the pleural cavity area. Evacuation of fluid from the pleural cavity is a necessary procedure in order to allow the lungs to expand properly and promote proper convalescence. During a prior art thoracentesis procedure, a user makes an incision through the chest wall and inserts a catheter or other tubular member through the incision and into the pleural cavity. The proximal end of the catheter is then connected to a negative pressure source, e.g. luer tip syringe, and fluid which includes blood, air and other body secretions may be evacuated from the pleural cavity through the catheter by operation of the syringe. 
     Medical devices used to remove fluid from the pleural cavity during a thoracentesis procedure are well known in the art. A typical prior art device for performing thoracentesis is disclosed in U.S. Pat. No. 4,447,235 to Clarke entitled “Thoracentesis Device” which discloses a flexible catheter having a distal end and a proximal end, a means defining an elongated conduit connected to the proximal end of the catheter and in line therewith, and a hollow needle having a sharpened distal end adapted to penetrate the chest cavity. However, the drawback of the Clarke device is that an inadvertent puncture of an internal body organ by the sharpened distal end of the catheter could possibly occur during insertion of the device through the chest wall since there is no provision for indicating whether the sharp distal end of the device has made contact with the lungs, or other body organ, once the sharpened distal end enters the pleural cavity. 
     Other medical devices, such as Verress-type needle device, used for pneumoperitoneum also require a means for detecting whether the sharpened distal end of the device has made contact with an internal body organ when insufflating the abdominal cavity. A typical Verress-type needle device is disclosed in U.S. Pat. No. 5,256,148 to Smith et al., entitled “Verress Needle with Enhanced Acoustical Means” which shows a single spring-loaded, blunt tipped inner needle slidably contained within a larger diameter piercing outer needle fixedly attached to the handle of the device. In operation, the outer needle of the Verress-type needle device is used to penetrate completely through the abdominal and stomach walls and enter the stomach. As the outer needle penetrates the stomach, the resistance applied against the single spring loaded inner needle causes the inner needle to withdraw inside the conduit of the outer needle such that the sharp end of the outer needle is exposed and extends outwardly beyond the blunt tip inner needle. Once the outer needle completely penetrates the stomach wall and enters the stomach, the resistance against the end of the inner needle applied by the stomach wall is removed so that the single spring force applied to the inner needle causes the blunt tip distal end thereof to move forwardly to a fully extended position beyond the sharp distal end of the outer needle. The Smith et al. device is also provided with a detection means for visually indicating to the user whether the fully extended blunt tip distal end of the inner needle has made contact with an internal body organ after insertion into the stomach. The detection means of the Smith et al. device comprises a single spring arrangement wherein the proximal end of the inner needle disposed inside the housing of the device is spring loaded and operatively connected to a detection means such that a visual indication is given to the user that contact has been made by the blunt tip distal end of the inner needle. The detection means also features two opposite colored bands that are viewed through a window made in the handle of the device. One of the colored bands indicates that the blunt tip distal end of the inner needle is in a fully extended position outwardly beyond the sharp tip of the outer needle, thereby visually indicating to the user that the distal end of the device has not made physical contact with an internal body organ after entry into the stomach. The opposite colored band indicates that the blunt tip distal end of the inner needle has made contact with a body organ and has been retracted into the conduit of the outer needle so that the sharpened tip of the outer needle is exposed. These opposite colored bands provide a visual stimulus to the user as to whether contact is being made by the blunt tip distal end of the device with an internal body organ, thus inadvertent puncture or lacerations of other body organs can be prevented. However, the detection means of the Smith et al. device could be improved even further when applied to thoracentesis or other invasive procedures. The single spring arrangement used to visually indicate the position of the distal end of the device could be improved to provide enhanced detection sensitivity to indicate whether contact has been made with the lungs or other internal body organs. 
     Therefore, there appears a need in the art for a medical device which includes an indication means that provides improved sensitivity as to the position of the blunt tip distal end of the inner needle relative to the sharpened outer needle of the device. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     In brief summary, the present invention overcomes and substantially alleviates the deficiencies in the prior art by providing a thoracentesis device having a hypersensitive dual spring detection mechanism that provides quick and immediate visual indication to the user of when the blunt tip distal end of the inner needle of the device has made contact with a body organ, thereby preventing puncture or laceration of the lung area during thoracentesis. The thoracentesis device of the present invention comprises an outer needle fixedly attached at its proximal end to a handle and a sharp distal end adapted for penetrating the chest wall of a patient. The sharp distal end of the outer needle includes an opening in communication with a first conduit formed along the longitudinal axis of the outer needle. Slidably disposed inside the first conduit is a smaller diameter inner needle having a spring-loaded proximal end slidably engaged inside the handle and a blunt tip distal end which, in its fully extended position, extends a short distance outwardly beyond the sharp distal end of the outer needle. A plurality of radial ports are formed around the blunt tip distal end of the inner needle with each port in communication with a second conduit that extends longitudinally through the inner needle and opens into a cavity formed inside the handle. The second conduit of the inner needle provides a means for evacuating fluid via a fluid pathway established through the second conduit and cavity of the thoracentesis device. 
     The blunt tip distal end of the inner needle is maintained in its fully extended position due to its operative engagement with a large spring housed in the handle which applies a distal spring force along the longitudinal axis of the inner needle. The inner needle is also operatively engaged with a small spring which applies a smaller proximal spring force in direct opposition to the distal spring force applied by the large spring. The large spring and a small spring form a part of the dual spring detection mechanism of the present invention which provides an immediate visual indication that the blunt tip distal end of the inner needle has made contact with an internal organ, such as the lungs, while the thoracentesis device is operating inside the pleural cavity of a patient. When properly assembled, the detection mechanism has a dual spring arrangement operatively connected to an indicator arrangement comprising positive and negative indicators. The positive indicator is attached to a portion of the blunt tip inner needle housed in the cavity of the handle so that longitudinal movement by the spring-loaded inner needle necessarily moves the positive indicator relative to the stationary negative indicator which is nested and hidden inside the positive indicator. A cavity is formed at the distal end of the positive indicator for housing and completely masking the negative indicator from view through the transparent housing of the handle when the inner needle is in a fully extended position. 
     The dual spring arrangement according to the present invention is designed so that the large spring is in a minimum compressed state and the small spring is in a maximum compressed state when the blunt tip distal end is maintained in its fully extended position. In operation, when the blunt tip distal end makes contact with a body organ, e.g. the lungs, after insertion of the thoracentesis device through the patient&#39;s chest wall, the proximal contact force applied by the lungs to the blunt tip distal end of the inner needle in combination with the proximal spring force generated by the small spring, more quickly overcomes the distal spring force applied by the large spring at a reduced organ contact force than that required of prior art single spring arrangements. In other words, the addition of the proximal spring applied by the small spring requires a much smaller contact force to be applied by the contacted organ in order to more quickly visually alert the user that the inner needle is being withdrawn and the sharp distal end of the outer needle is being exposed. As the combined proximal forces applied by the small spring and contacted body organ become greater than the single distal spring force applied by the large spring, the positive indicator is made to move relative to the stationary negative indicator which exposes the negative indicator to view from its nested position inside the positive indicator and visually alerts the user that contact has been made by the blunt tip distal end of the inner needle. Accordingly, the addition of a second spring provides added detection sensitivity to the slightest contact made by the blunt tip distal end of the inner needle which better avoids inadvertent punctures or lacerations by the sharp distal end of the outer needle. 
     It will be appreciated that the dual spring arrangement of the present invention provides enhanced detection sensitivity by the thoracentesis device to the slightest contact made by the blunt tip distal end of the inner needle with a body organ. In the absence of the small spring providing a counterforce against the large spring, a much greater contact force by the body organ against the blunt tip distal end would be required to detect and alert the user that an internal organ was contacted. This lessened sensitivity by the single spring detection mechanism could cause possible inadvertent puncture or laceration of the lung wall since the user would be unaware that the blunt tip distal end had made sufficient contact with the body organ and exposed the sharp distal end of the thoracentesis device to the body organ. 
     The thoracentesis device of the present invention further comprises a sleeve member disposed in the cavity of the handle. The sleeve member includes distal and proximal bores with the distal bore housing the large spring therein as well as a portion of the positive indicator. The sleeve member also includes an axial opening formed through an internal shoulder which communicates with both proximal and distal bores and establishes a fluid pathway which extends from the radial ports of the inner needle to an opening formed at the proximal end of the handle. The proximal bore communicates with a one-way valve for preventing the reflux of evacuated fluid back through the thoracentesis device. Finally, the opening may be connected to a negative pressure device, e.g. a luer-tipped syringe, for manually evacuating fluid from the pleural cavity and out through the thoracentesis device. 
     Accordingly, a primary object of the present invention is to provide a medical device which is operable to reduce the possibility of inadvertent puncture or laceration of the lung or other body organ by the device. 
     Another object of the present invention is to provide a hypersensitive detection means for quickly indicating contact of a body organ by the distal end of the medical device to the user. 
     A further object of the present invention is to provide a visual indication means that may be viewed at any angle through the handle of the medical device. 
     Another further object of the present invention is to provide a dual spring arrangement operatively connected to a visual indication means for enhanced detection of an internal body organ by the medical device. 
     These and other objects of the present invention are realized in the preferred embodiment of the present invention, described by way of example and not by way of limitation, which provides for a medical device having a hyper-sensitive detection means for indicating contact of the distal end of the device with a body organ. 
     Additional objects, advantages and novel features of the invention will be set forth in the description which follows, and will become apparent to those skilled in the art upon examination of the following more detailed description and drawings in which like elements of the invention are similarly numbered throughout. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of the thoracentesis device according to the present invention; 
     FIG. 2 is a perspective view of the thoracentesis device with the blunt tip distal end in the retracted position exposing the sharpened distal end according to the present invention; 
     FIG. 3 is a perspective view of the thoracentesis device with the blunt tip distal end in a partial retracted position according to the present invention; 
     FIG. 4 is a perspective view of the thoracentesis device with the blunt tip distal end in the fully extended position according to the present invention; 
     FIG. 5 is a cross-sectional view of the thoracentesis device taken along line B—B shown in FIG. 4 with the blunt tip distal end in the fully extended position inside the pleural cavity according to the present invention; 
     FIG. 6 is a cross-sectional view of FIG. 2 taken along line A—A in FIG. 2 with the blunt tip distal end in the retracted position and the sharpened distal end penetrating the chest wall according to the present invention; 
     FIG. 7 is a cross-sectional view taken along line C—C shown in FIG. 3 with the blunt tip distal end in the partial retracted position when in contact with the lung wall according to the present invention; and 
     FIG. 8 is a graph illustrating the enhanced sensitivity of the dual spring arrangement according to the present invention relative to the prior art single spring arrangement. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings, the preferred embodiment of the thoracentesis device of the present invention is illustrated and generally indicated as  10  in FIG.  1 . For ease of reference, distal shall refer to the end of the device farthest away from the user, while proximal shall refer to the end of the device closest to the user. Referring to FIGS. 1 and 5, thoracentesis device  10  comprises a handle  11  having a transparent hollow body  13  and a hollow outer needle  30  fixedly attached to handle  11 . 
     As shown specifically in FIG. 5, handle  11  comprises a front housing  12  attachable to a rear housing  14  which defines a cavity  50  within handle  11 . The front housing  12  includes an external threaded portion  80  which mates with a corresponding internal threaded portion  81  formed along the exterior surface of rear housing  14  by rotating either housing  12 ,  14  relative to the other until a sealing engagement is obtained between threaded portions  80 ,  81 . As further shown, front housing  12  forms an annular chamber  42  which communicates with a larger annular chamber  44 . The outer surface of handle  11  forms a finger portion  56  at the distal portion thereof adapted to be gripped between the user&#39;s thumb and forefinger during operation of thoracentesis device  10 . A gripping portion  52  is also formed along the outer surface of handle  11  at its middle portion for engagement by the palm of the user. 
     Outer needle  30  defines a longitudinal inner conduit  34  which extends the entire length of outer needle  30  and communicates with a distal opening  38  formed at the distal end of thoracentesis device  10 . Outer needle  30  further includes a sharpened distal end  54  which is adapted to penetrate through a chest wall  41  of a patient and is formed adjacent the distal opening  38 . Referring to FIG. 7, slidably disposed along conduit  34  and longitudinally aligned with outer needle  30  is a springloaded inner needle  28 . The proximal end of inner needle  28  is spring-loaded by virtue of its operative connection to a large spring  20  disposed inside handle  11 , while the distal end of inner needle  28  defines a blunt tip distal end  32  with a plurality of radial ports  36  formed adjacent end  32  which communicate with conduct  34 . The blunt tip distal end  32  provides a safe blunt surface for contacting the lung wall  43  or other body organ without penetrating or lacerating the tissue. Referring to FIGS. 4 and 5, when properly assembled large spring  20  imparts a spring force in the distal direction to inner needle  28  sufficient to place the blunt tip distal end  32  of needle  28  in a fully extended position that extends beyond the sharpened distal end  54  of the outer needle  30 . 
     In addition to large spring  20 , thoracentesis device  10  further includes a small spring  22  which is slidably mounted around a portion of inner needle  28  housed in handle  11  and provides a smaller proximal spring force to inner needle  28  in direct opposition to the spring force applied by the large spring  20  in the distal direction. As shall be discussed in greater detail below, large spring  20  imparts a greater spring force than the spring force applied by the small spring  22  such that the blunt tip distal end  32  of inner needle  28  is maintained in its fully extended, non-contact position forward of the sharpened distal end  54 . The large spring  20  and small spring  22  comprise a dual spring arrangement  90 . The dual spring arrangement  90  is designed such that large spring  20  is in a minimum compressed state and small spring  22  is in a maximum compressed state when the blunt tip distal end  32  is maintained in the fully extended position. When the blunt tip distal end  32  contacts an internal body organ, the spring loaded inner needle  28  is moved in the proximal direction which forces the small spring  22  to uncompress and the large spring  20  to compress. 
     According to another aspect of the present invention, thoracentesis device  10  comprises positive and negative indicators  16  and  18  having respective contrasting colors for providing a visual stimulus to the user that the blunt tip distal end  32  has made contact with an internal body organ. Positive and negative indicators  16  and  18  are housed inside the transparent body of handle  11  and at least one of the indicators  16 ,  18  are visible to the user at all angles through handle  11 . Referring to FIGS. 1 and 5, positive indicator  16  is fixedly attached along a portion of inner needle  28  housed inside handle  11  and is partially disposed inside a distal passage  65  of a hollow sleeve  24  which is slidably mounted along inner needle  28 . Positive indicator  16  includes a chamber  46  which is adapted to nest negative indicator  18  therein when blunt tip distal end  32  is in the fully extended position. As further shown, negative indicator  18  is stationary and fixedly positioned inside cavity  50 . As shall be explained in greater detail below, when blunt tip distal end  32  makes contact with a internal body organ inner needle  28  is forced backward such that positive indicator  16  moves relative to the stationary negative indicator  18  and unmasks indictor  18 . 
     Sleeve  24  has a generally hollow tubular configuration and includes distal passage  65  and proximal passage  67  separated by an inner wall  82  interposed across the interior of sleeve  24 . Inner wall  82  forms an axial opening  84  that slidably engages the proximal portion of inner needle  28  therethrough. To securely retain sleeve  24  inside handle  11 , the end of proximal passage  67  defines an annular flange  66  for seating against inner shoulder  68  that sandwiches flange  66  between the front and rear portions  12 ,  14  handle  11 , thereby fixedly maintaining sleeve  24  in a stationary position inside cavity  50 . Handle  11  further includes a chamber  58  for housing a one-way valve  70  which provides a means of preventing the reflux of evacuated fluid back through thoracentesis device  10  as well as preventing atmospheric air from entering the pleural cavity during operation of device  10  through the chest wall  41 . As further shown, one-way valve  70  includes an annular flange  71  formed adjacent one end thereof for anchoring valve  70  between sleeve  24  and an inner shoulder  72  formed along the interior surface of handle  11 . Preferably, one-way valve  70  is a duck bill valve, although any valve which functions to prevent reflux of fluid being withdrawn in one direction, while also preventing atmospheric air from entering into the pleural cavity from the other direction, is felt to fall within the scope of the present invention. 
     Referring to FIGS. 2-7, the operation of thoracentesis device  10  will be discussed in greater detail. FIGS. 5-7 illustrate the sequence of the thoracentesis device  10  as the outer needle  30  penetrates the chest wall  41  of a patient. Referring specifically to FIG. 6, the user penetrates through the chest wall  41  of a patient by contacting the blunt tip distal end  32  of thoracentesis device  10  against wall  41  until the combined force generated by the resistance of chest wall  41  and the proximal spring force applied by small spring  22  to inner needle  28  overcomes the distal spring force similarly applied by the large spring  20 . Referring to FIG. 7, as sufficient contact is made by the blunt tip distal end  32 , distal end  32  is forced to withdraw backward in the proximal direction into conduit  34  as the sharpened distal end  54  of outer needle  30  is exposed and penetrates through the chest wall  41 . Once the sharpened distal end  54  of thoracentesis device  10  completely penetrates the chest wall  41 , distal end  54  enters the pleural cavity  45  of the patient. 
     As illustrated in FIG. 5, once the sharpened distal end  54  enters the pleural cavity  45 , the resistance generated by chest wall  41  against distal end  54  ceases and the distal spring force applied by the large spring  20  overcomes the smaller proximal spring force applied by small spring  22 . This forces the blunt tip distal end  32  forwardly out from conduit  34  such that tip  32  is placed in its original fully extended position beyond the sharpened distal end  54 . In the fully extended position, blunt tip distal end  32  shields sharpened distal end  54  so that end  54  is prevented from lacerating the tissue of the patient. FIGS. 2-4 illustrate this sequence of the blunt tip distal end  32  being urged forwardly beyond the sharpened distal end  54  as the distal spring force applied by the large spring  20  overcomes the smaller proximal spring force of the smaller spring  22 . At this point, the user attaches a luer tip syringe (not shown) to an adapter  62  provided at the proximal end of thoracentesis device  10  by inserting the tip of the syringe through proximal opening  86  and into passage  60  until a sealing engagement with proximal opening  86  is achieved. The user then pulls the plunger of the syringe backward in order to create a negative pressure within the pleural cavity  45  that suctions fluid into the plurality of radial ports  36  of inner needle  28 . The suctioned fluid is then evacuated through the conduit  34  and out valve  26  where it enters the body of the syringe. 
     As noted above, the present invention contemplates a hypersensitive detection means for detecting any resistance met by the blunt tip distal end  32 . During thoracentesis or any similar medical procedure the user must manipulate the distal end of thoracentesis device  10  within the pleural cavity  45  in order to effectively suction secretions throughout cavity  45 . However, such manipulation of the thoracentesis device  10  may cause inadvertent contact with the lungs  43  or other sensitive internal body organ. As shown in FIGS. 6 and 7, inadvertent contact of the blunt tip distal end  32  with the lungs  43  causes end  32  to be forced backward. As the inner needle  28  is driven backward into conduit  34  the small spring  22  exerts a proximal spring force in the same direction, which in combination with a resistive force A generated by the contacted organ, moves the positive indicator  16  relative to negative indicator  18  and unmask negative indicator  18  from its hidden nesting position within positive indicator  16 . As the negative indicator  18  comes into view it visually alerts the user that blunt tip distal end  32  has made contact with a body organ. 
     Referring to FIG. 8, a graph is shown illustrating the greater detection sensitivity of the dual spring arrangement  90  according to the present invention in comparison to the single spring arrangement  88  of prior art detection mechanisms. As shown in FIG. 8, it takes a much smaller resisting force being generated by the contacted internal body organ in order to displace the inner needle  28  and unmask the negative indicator  18 , thereby more quickly alerting the user. For example, inner needle  28  of the present invention begins to displace the positive indicator  16  and unmask negative indicator  18  when 0.075 lbs. of combined force generated by both the resistance of the lung  43  and the proximal spring force of small spring  22  are applied to inner needle  28 . In contrast, it takes at least 0.275 lbs. of resistive force alone to begin displacing the inner needle of the prior art single spring arrangement. It is not until over 0.55 lbs. of force has been applied that both the double spring arrangement and single spring arrangement have equal displacement of the positive indicator  16  for the same force as noted at point  92 . 
     It can be appreciated that the double spring arrangement of the present invention promotes enhanced detection sensitivity and quicker visual indication of detection to the user due to the addition of a small spring  22  to the double spring arrangement. Accordingly, the combined resisting force and proximal spring force applied by the small spring  22  in direct opposition to the larger distal spring force applied by the large spring  20  permits a more rapid displacement of positive indicator  16  since the spring force of the small spring  22  supplements the resisting force of the contacted organ in overcoming the distal spring force of the large spring  20 . Preferably, both large and small springs  20 ,  22  are made from any suitable flexible metal, however any resilient, flexible material that imparts a spring force upon compression is felt to fall within the scope of the present invention. The present invention contemplates that positive and negative indicators may have any contrasting colors, such as red and green, which will visually alert the user. It should be apparent to those skilled in the art that the present invention, although intended for thoracentesis, could also be applied to similar medical procedures, such as paracentesis, pneumothorax, or pericardiocentesis that require some type of hypersensitive detection mechanism to prevent laceration or puncture of internal body organs. 
     It should be understood from the foregoing that, while particular embodiments of the invention have been illustrated and described, various modifications can be made thereto without departing from the spirit and scope of the present invention. Therefore, it is not intended that the invention be limited by the specification; instead, the scope of the present invention is intended to be limited only by the appended claims.

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