Abstract:
Systems and methods use extraction devices for extracting and monitoring biological fluids of patients. The systems and methods involve creating an opening in the biological tissue of the patient and placing a sampling aperture of the extraction device over the opening. The sampling aperture is defined in a contact surface of the extraction device that is placed into contact with the tissue of the patient. A pump of the extraction device such as a depressible bulb sealed to the body is charged to create a vacuum between the pump through a sampling channel to the sampling aperture, and the vacuum draws the biological fluid from the tissue opening into the sampling channel. An access point is exposed to the sampling channel, and the sample of fluid may be accessed from the access point. The access point may be an extraction opening covered by an access door, and the access door is opened to access the sample. Alternatively, the access point may be electrodes extending into the sampling channel where the electrodes are connectable to a fluid analyzer device.

Description:
[0001]     This application is being filed as a PCT International Patent application in the name of Mark Faupel and Danny Lincoln (both U.S. nationals and resident), designating all countries, on 22 May 2003.  
       TECHNICAL FIELD  
       [0002]     The present invention is related to the extraction and monitoring of biological fluids. More particularly, the present invention is related to methods and systems including devices that extract biological fluids for subsequent monitoring of fluid parameters.  
       BACKGROUND  
       [0003]     Biological fluids of patients such as blood, interstitial fluid, or other fluid types may be extracted and monitored by analyzing the fluid samples for various parameters. Components of a fluid sample may be analyzed to determine the current physical condition of the patient. Conventionally, the fluid sample may be taken through a sample collection device such as the Terumo CAPIJECT™.  
         [0004]     To extract a biological fluid sample using a collection device such as the CAPIJECT™, the skin of the patient is lanced with a suitable and relatively sizable lance. The tube of the CAPIJECT™ is placed in an upright position over the relatively sizable puncture site where a drop of fluid has developed by squeezing the lanced site. A collection port of the tube is placed in proximity with the drop, and the fluid sample is then allowed to flow by gravity into the tube of the CAPIJECT™ through the collection port until the tube is filled to a recommended marking. A cap is then placed on the tube of the CAPIJECT™ to prevent the fluid sample from leaking from the tube. After taking the sample, the puncture site is treated to stop any further bleeding or other fluid loss by applying pressure to the site using a gauze pad.  
         [0005]     Thus, while the use of the CAPIJECT™ obtains the necessary sample, there are drawbacks to its use. Notably, the patient experiences discomfort associated with the sizable puncture that is required to develop the drop of fluid. Furthermore, the puncture size must be treated as noted above to stop further fluid loss. Additionally, the puncture process recurs and a new CAPIJECT™ tube may be used each time a new sample is taken. Accordingly, the patient is inconvenienced by the extraction of biological fluid with the CAPIJECT™ device.  
       SUMMARY  
       [0006]     Embodiments of the present invention address these issues and others by providing methods and devices that extract samples of biological fluids. A vacuum is created at an aperture on a surface of the device to draw fluid from the puncture into the device. The sample may then be accessed from an access point of the device for further analysis.  
         [0007]     One embodiment is a device for extracting biological fluid. The device has a body including a contact surface that defines a sampling aperture and a sensor surface that defines an access point. The device also has a pump and a sampling channel between the sampling aperture and the pump. The sampling channel is in fluid communication with the access point.  
         [0008]     Another embodiment is a method of extracting biological fluid. The method involves creating an artificial unobstructed opening in biological tissue. A contact surface of a sampling device is placed on the tissue, where the contact surface defines an aperture located proximate to the opening in the biological tissue. A pump of the sampling device is charged to develop a vacuum at the aperture and draw the biological fluid through the aperture into a sampling channel. The biological fluid is accessed through at an access point of the sampling device that is in fluid communication with the sampling channel.  
         [0009]     Another embodiment is a device for extracting biological fluid. The device has a body that includes a planar contact surface that defines a sampling aperture. The device also has a sensor surface that defines an access point and a ventilation surface that defines a ventilation opening. The device also includes a depressible self-restoring bulb sealed to the body and a sampling channel between the sampling aperture and the bulb. The sampling channel is in fluid communication with the access point, and a wick is disposed within the sampling channel between the extraction opening and the bulb. A ventilation channel interconnects the ventilation opening to the sampling channel, and the wick is disposed between the ventilation chamber and the sampling aperture.  
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a top perspective view of an extraction device according to one embodiment.  
         [0011]      FIG. 2  is a bottom perspective view of an extraction device according to the embodiment of  FIG. 1 .  
         [0012]      FIG. 3  is a cross-sectional view taken through the extraction device according to the embodiment of  FIGS. 1 and 2 .  
         [0013]      FIG. 4  is a top perspective view of an extraction device according to another embodiment.  
         [0014]      FIG. 5  is a bottom perspective view of an extraction device according to the embodiment of  FIG. 4 .  
         [0015]      FIG. 6  is a cross-sectional view taken through the extraction device according to the embodiment of  FIGS. 4 and 5 .  
         [0016]      FIG. 7  illustrates a set of operations performed to extract a sample using an extraction device according to the embodiments of  FIGS. 1-6 . 
     
    
     DETAILED DESCRIPTION  
       [0017]     Embodiments of the present invention extract fluid samples from a patient by creating a vacuum over an opening on the biological tissue of the patient to draw the fluid into the device. The opening in the tissue may be of various sizes such as but not limited to relatively small openings such as a microporation puncture sites formed in the stratum corneum layer of the skin. Accordingly, the patient may experience less discomfort where such relatively small openings are created, and the relatively smaller openings in the tissue require little or no further treatment after the sample has been taken. Furthermore, upon placing the device over an opening in the tissue, the device may be fixed to the site so that multiple samples may be taken from the site over a period of time.  
         [0018]      FIG. 1  shows one embodiment of an extraction device  100 . The device includes a body  102  that provides several surfaces. The body  102  may be made of various materials, such as the Alphagary Dural 725 polyvinyl chloride (“PVC”) product. Such body materials are commonly approved by government regulations for use in biomedical devices. The body may be constructed of two separate pieces to simplify the construction and the pieces are then bonded together with an adhesive. For example at top piece may define a sensor surface  128  and ventilation surface  130  while a bottom piece defines a contact surface  110  as shown in  FIG. 2 .  
         [0019]     A sensor surface  128  of the body  102  defines an access point, discussed in more detail below with reference to  FIG. 3 , where the fluid sample may be accessed. The access point of this embodiment includes an extraction opening covered by an access door  106 . The access door  106  is held in place by access door retainers  122  covering over small tabs extending from each side of the door  106 . The retainers  122  are fixed to body  102  by an adhesive such as Loctite 4011 or alternatively may be integrally formed into the body  102 . The access door retainers  122  hold the access door  106  in position and allow the access door to be opened and closed relative to the extraction opening. The access door  106  may be made of various materials such as the PVC used for the body  102  and a seal  134  such as silicone rubber may be placed between the access door  106  and the body  102  to form a proper seal. The access door  106  may have a snap fit to the body  102  to hold the access door  106  closed against the silicone seal.  
         [0020]     A ventilation surface  130  of the body  102  defines a ventilation opening  118 , discussed in more detail below with reference to  FIG. 3 , through which ventilation is provided to eliminate a vacuum created by the device  100  when the device  100  is to be removed from the patient. A ventilation plate  108  seals the ventilation opening to prevent ventilation when the vacuum is being created and sustained to draw fluid into the device  100  as discussed below. The ventilation plate  108  of this embodiment is held in place by a ventilation strap  124  that is adhesively attached to the body  102  and is removed when the ventilation plate  108  is to be removed to release the vacuum. The ventilation plate  108  and ventilation strap  124  may be made of various materials such as PVC, and a silicone rubber seal  132  may be positioned between the plate  124  and the body  102  to form a proper seal.  
         [0021]     The extraction device  100  also includes a pump  104 . In this embodiment, the pump  104  is a bulb that is sealed to the body  102  by application of an adhesive such as Loctite 4011 around the edges of the bulb. The bulb  104  is depressible and is self-restoring so that when the bulb  104  is depressed, air is forced out of the bulb and as the bulb restores its shape, a vacuum is created. The bulb  104  may be made of various resilient materials such as the ELASTOCIL® silicon rubber product. While the pump  104  is shown as a bulb, the pump  104  may be of other forms such as a syringe type pump that may be biased to self-restore the plunger position once it has been depressed or may rely on the user to restore the plunger manually to create the vacuum through the extraction device  100 .  
         [0022]      FIG. 2  shows the underside contact surface  110  of the body  102 . The contact surface may be planar or may have various curvatures, depending upon the area of the body where the sample may be extracted. For example, a planar contact surface  110  is adequate where the sample is taken from the relatively flat abdomen of the patient. The contact surface  110  defines a sampling aperture  112 . The sampling aperture  112  is a hole that extends from the exterior of the contact surface  110  into an internal sampling channel discussed below with reference to  FIG. 3 . The sampling aperture  112  may be have a countersink shape such that the hole at the exterior has a larger diameter than the channel leading from the exterior to facilitate proper placement of the aperture  112  over the puncture site.  
         [0023]      FIG. 3  provides a cross-sectional view of the extraction device  102  as taken through the center of the bulb  104 , an extraction opening  116  forming an access point, a ventilation opening  118 , a wick  120 , and the sampling aperture  112 . As shown in this view, the interior of the bulb  104  is hollow so that the interior volume can be collapsed to evacuate the air upon the user depressing the bulb  104 . The bulb collapses toward the wick  120  that allows air to pass from the bulb and out through an available channel. For example, after the device  100  is installed and the ventilation opening  118  remains sealed, the air being evacuated from the pump  104  cannot pass through the ventilation channel  126  due to the seal and cannot pass through the extraction opening  116  to ambient due to the access door  106  being closed. However, the air may pass through the sampling channel  114  and out the sampling aperture  112  to the exterior of the device  100  as the sampling aperture  112  is not sealed to the patient.  
         [0024]     After the bulb  104  is released upon being depressed, the bulb  104  begins to restore its shape which creates a vacuum to establish suction through the wick  120 , sampling channel  114 , and sampling aperture  112 . The vacuum causes fluid to be drawn from the opening in the tissue through the sampling aperture  112 . The drawn fluid fills the portion of the sampling channel  114  up to the wick  120  but is prevented from entering the bulb  104  or the ventilation channel  126  by the wick  120 . The fluid pools into the extraction opening  116 . The sample can then be accessed from the access point defined by the extraction opening  116  which is in fluid communication with the sampling channel  114  upon opening the access door  106 .  
         [0025]     The wick  120  may be made of a material such as Whatman filter paper. As noted above, the wick is provided to allow air to flow while preventing the fluid from being drawn into the pump  104  and/or the ventilation chamber  126 . The wick  120  thereby reduces the amount of fluid that must be sampled to produce a pool at the extraction opening  116 . The wick  120  may also absorb the sample of fluid remaining after it has been satisfactorily accessed.  
         [0026]      FIG. 4  shows an alternative embodiment of the present invention. The embodiment of  FIG. 4  is similar to that of  FIG. 1 . However, the embodiment of  FIG. 4  includes a sensor connector tube and corresponding electrodes so that the fluid sample may be accessed through contact of the electrodes with the fluid. Additionally, the embodiment of  FIG. 4  has a repositioned wick and sampling aperture as well as a re-routed sampling channel, and this embodiment relies on a single adhesive piece to provide the ventilation seal.  
         [0027]     The extraction device  200  of  FIG. 4  includes a body  202  that may be constructed of the materials used for the embodiment of  FIG. 1 . Additionally, the device  200  includes a pump  204  such as a bulb sealed to the body  202 . The device  200  also includes a ventilation surface  230  of the body  202  and a ventilation cover  208  that covers a ventilation opening. The device  200  includes an sensor surface  228  that includes a tubular port  206  containing electrodes that extend into the sampling channel  214  of the body  202  to form an access point. While the tubular port  206  is shown as being integral to the body  202 , the tubular port  206  and the electrode contained within it may alternatively be detachable.  
         [0028]      FIG. 5  shows the underside contact surface  210  of the device  200 . As discussed above, the contact surface  210  may be planar or have a curvature. Additionally, the contact surface  210  defines a sampling aperture  212  that includes a hole at the exterior of the contact surface  210  and extends into an interior sampling channel. As discussed above, the sampling aperture  212  may have a countersink shape so that the larger diameter of the opening at the exterior facilitates placement of the aperture  212  over the opening in the tissue.  
         [0029]      FIG. 6  shows a cross-sectional view taken through the center of the bulb  204 , a ventilation opening  218 , the sampling aperture  212 , the tube  206 , and a wick  220 . As shown in this embodiment, the wick is positioned under the sensor surface  228  of the body  202 . Additionally, the sampling aperture  212  is positioned directly beneath the pump  204 . However, the sampling channel  214  is routed from the base of the pump  204  to the wick  220 , as indicated in phantom, and from the wick  220  to the sampling aperture  212 .  
         [0030]     The access point for accessing the fluid for testing includes the area where the electrodes enter and pass through the sampling channel  214  between the wick  220  and the sampling aperture  212 . The wick  220  continues to prevent fluid from being drawn into the pump and/or ventilation channel  226  so that less fluid is necessary to remain in contact with the electrodes. Accordingly, when the pump is depressed with the ventilation seal  208  closed, air is evacuated through the sampling aperture  212  by passing from the pump  204  through the wick  220 . Then, upon the pump  104  restoring its shape, a vacuum occurs and creates suction at the sampling aperture  212  so that fluid is drawn into the sampling aperture  212  and pools along the sampling channel  214  between the between the aperture  212  and the wick  220  where the electrodes are placed.  
         [0031]     The electrodes  222  are disposed within the tube  206  and extend through into the sampling channel  214  to form the access point  216  in fluid communication with the sampling channel  214  and where the electrodes  222  access the fluid. Thus, when fluid is drawn into the sampling channel  214  and pools between the wick  220  and the sampling aperture  212 , the electrodes  222  are immersed in the fluid. A sensor device (not shown) connected to the tube  206  in electrical communication with the electrodes  222  may then analyze the fluid through the exposure of the electrodes  222  to the fluid. The fluid analysis through the electrodes  222  may be performed by well-known techniques.  
         [0032]     When the extraction device  200  is to be removed from the patient, the ventilation seal  208  may be peeled back from the ventilation opening  218  to eliminate the vacuum that has been created by passing air from ambient through the ventilation channel  226 . The ventilation seal  208  may be of various forms such as an adhesive film that covers the ventilation opening  218  and that seals to the ventilation surface  230  of the body  202 . The device  200  is then removed from the patient once the vacuum has been eliminated.  
         [0033]      FIG. 7  provides one example of a set of steps performed to extract samples from a patient using one of the embodiments discussed above. At opening operation  302 , an artificial and unobstructed opening in the biological tissue of the patient is created. For example, the opening in the tissue may be created by a lancet, by a microporation device, by lasers, or by other techniques such as examples discussed in U.S. Pat. No. 5,885,211. The extraction device is then placed on the tissue of the patient with the sampling aperture positioned directly over the opening in the tissue at position operation  304 . The extraction device is fastened to the tissue of the patient such as by taping the device to the tissue at installation operation  306 . Adhesive tape may be applied to the contact surface of the extraction device such that when the device is placed on the tissue, the adhesive tape bonds to the tissue and holds the device in place. An example of such adhesive tape is ARcare® 7717.  
         [0034]     After the device has been positioned and fastened to the tissue of the patient, the pump of the device can then be charged. For the device embodiment that includes an access door as opposed to a tube to interface with a sensor, then the pump is charged to create a vacuum at the sampling aperture at charge operation  310 . For the device embodiment that includes the tube to interface with a sensor and electrodes to access the fluid, the sensor may be connected to the tube and electrodes of the extraction device at sensor operation  308 , and then the pump is charged at charge operation  310 .  
         [0035]     Once the pump has been charged to create the vacuum, the fluid sample is drawn by the suction into the extraction device where it can be accessed from the access point by physically accessing the fluid through the extraction opening or can be accessed from the access point defined by the electrodes extending into the sampling channel. The fluid is accessed accordingly at sample operation  312 . Then, if another sample is to be taken using the currently installed extraction device as decided at query  314 , the pump is charged again at some later time at charge operation  310  to create a new vacuum and draw a new fluid sample as the older sample has been absorbed by the wick the time this next sample is to be taken.  
         [0036]     If another sample is not to be taken using the currently installed extraction device, then the ventilation seal is removed to allow the vacuum to be eliminated at ventilation operation  316 . The extraction device is then unfastened and removed from the tissue of the patient at removal operation  318 . When a later sample must be taken, the process returns to the opening operation  302 . The extraction device may be replaced every 2-3 days by performing the process of  FIG. 7 .  
         [0037]     The various embodiments described above are provided by way of illustration only and should not be construed to limit the invention. Those skilled in the art will readily recognize various modifications and changes that may be made to the present invention without following the example embodiments and applications illustrated and described herein, and without departing from the true spirit and scope of the present invention, which is set forth in the following claims.