referring to the drawings , the preferred embodiment of the thoracentesis device of the present invention is illustrated and generally indicated as 10 in fig1 . 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 fig1 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 fig5 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 fig7 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 fig4 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 fig1 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 fig2 - 7 , the operation of thoracentesis device 10 will be discussed in greater detail . fig5 - 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 fig6 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 fig7 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 fig5 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 . fig2 - 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 fig6 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 fig8 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 fig8 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 .
a thoracentesis device for removing fluid from a cavity includes a hypersensitive dual spring indication mechanism for alerting the user of any contact to internal body organs . the thoracentesis device includes a handle and an outer needle fixedly attached to the handle . the outer needle forms a sharp distal end and a spring - loaded inner needle , including a blunt tip distal end , is slidably disposed inside the conduit of the outer needle . a first spring has a first spring force that urges the inner needle into a fully extended position and a second spring has a second spring force that acts on the inner needle in opposition of the first spring force . a first and second opposite colored indicators are arranged in contact with the springs so as to alert the user to any initial contact made by the thoracentesis device .