The present invention relates to devices for penetrating the skin to extract blood or other fluids for analysis, and more particularly, to a skin-pricking device that is capable of transporting and analyzing physiological fluid from the skin.
Medical testing of a patient""s body fluid (such as blood) is often required for diagnosis and treatment of diseases. For example, to obtain a blood sample, the current state of-art requires either venipuncture or xe2x80x9cfinger-stickxe2x80x9d using a lancet. Finger-stick tests can be done for measuring blood sugar levels by diabetics using home test kits in xe2x80x9cpoint of care diagnosis.xe2x80x9d These test kits require that a drop of blood be obtained and placed into a measurement apparatus that calculates and then displays the glucose concentration in the blood sample. To obtain the drop of blood, the user is supplied with a lancet device, which makes a skin prick (typically in the user""s finger). The user then xe2x80x9cmilksxe2x80x9d the punctured spot to draw enough blood to the surface of the finger. The blood is then transferred to a test strip placed in the apparatus for measurement. In venipuncture, the blood sample is drawn in a syringe or a vial via a hypodermic needle from a vein and delivered to a measuring apparatus. In both these methods, the blood sample is injected into or applied onto a sensing device, which may be a sensor cartridge, or sensor strip (as in home glucose analysis) or a more sophisticated apparatus as used in laboratory tests. A clear disadvantage of these solutions is that they involve multiple steps, as well as other manipulations by the user. Moreover, in the finger-stick methods, the process of milking and drawing blood sample to the surface leads to changes in the analyte concentration, due to mixing of the sample with interstitial fluid or due to exposure of the sample to the ambient environment (e.g., exposure to air). For these reasons, the current methods of finger-stick sampling cannot be used to measure parameters such as blood gas contents. Due to the low efficiency of transferring the sample to the sensing apparatuses, the two step sampling and sensing methods in venipuncture typically need to draw larger blood samples than are actually required for sensing. Since pain is related to the amount of blood extracted, venipuncture inflicts significant amount of unnecessary pain and trauma to the patient. Thus, there is a need for an apparatus and method for sampling and quickly analyzing blood from a patient with minimal pain using a small volume of sample blood.
The present invention provides a technique for sampling and analyzing physiological fluid acquired from a tissue on the body of an animal (i.e., physiological tissue or body tissue) such as the skin (e.g., a liquid such as blood from the capillaries beneath the surface of the skin or the interstitial fluid of a tissue). In one aspect, the present invention provides a device for sampling and analyzing a fluid from the physiological tissue (e.g., from capillaries beneath the skin) of a patient by puncture. The device includes a body that includes a needle and sensors. The needle has a point for puncturing the physiological tissue and a channel in the body conducting fluid (e.g., blood) proximally from the wound into the body. Sensors in the body are accessible to blood conducted along the channel for analysis. The device can be used to sample and analyze the fluid quickly, and with minimal exposure to air. In one aspect, the present technique of sampling and analyzing a physiological fluid includes puncturing the physiological tissue with a lancing unit having a channel therein, leading through a needle to a sharp point; conducting the fluid from the physiological tissue from the sharp point up the channel; and analyzing the fluid with sensors along the channel while the fluid is in the channel.
Using the technique of the present invention, a user can conveniently obtain and analyze a small volume of a physiological sample (such as blood) quickly, thereby ensuring that the sample does not have exposure to air. Using a device of the present invention will enable one or more constituents (and parameters) of the patient""s physiological fluid to be measured to determine the biochemical parameters (which reflect the patient""s physiological condition). Such parameters may include pH, glucose concentration, blood gas content, the concentration of other blood constituents (such as , but not limited to, e.g., creatinine, potassium, chloride, calcium, blood urea nitrogen), and the like. There is no need for the user to undergo extensively invasive procedures such as arterial or venous punctures to measure such parameters, hence making self-monitoring possible for data such as blood gas contents. The convenience afforded by the present invention enables a user to more closely comply with the self-monitoring program prescribed by the health professionals. Further, the device can have a needle that is disposable and well-shielded to prevent exposure of biohazard (such as blood from a sick patient) to others. Additionally, the needle according to the present invention can be mass-produced, thus making such devices more cost-effective and available to users.