Analyte sensor

Abstract

Systems and methods of use for continuous analyte measurement of a host's vascular system are provided. In some embodiments, a continuous glucose measurement system includes a vascular access device, a sensor and sensor electronics, the system being configured for insertion into communication with a host's circulatory system.

1 . A method for measuring a concentration of an analyte in a vein of a host, the method comprising:
 passing a reference solution at a flow rate of from about 0.001 ml/min to about 0.02 ml/min past an analyte sensor configured to measure an analyte concentration, wherein the analyte sensor is a component of an analyte measuring system comprising a vascular access device, the analyte sensor, and electronics operatively connected to the analyte sensor and configured to generate a signal associated with the analyte concentration, wherein the analyte sensor resides within the vascular access device, and wherein the vascular access device and the analyte sensor are in fluid communication with a vein of a host;   measuring a signal associated with an analyte concentration of the reference solution;   drawing back a sample from the vein of the host; and   measuring a signal associated with an analyte concentration of the sample.   
     
     
         2 . The method of  claim 1 , wherein the analyte is glucose, and wherein measuring the concentration of the analyte comprises measuring a glucose concentration. 
     
     
         3 . The method of  claim 1 , further comprising repeating passing and drawing. 
     
     
         4 . The method of  claim 3 , wherein repeating is at least one of periodically repeating or intermittently repeating. 
     
     
         5 . The method of  claim 1 , further comprising calibrating the analyte sensor using a baseline measurement obtained from the signal associated with the analyte concentration of the reference solution. 
     
     
         6 . The method of  claim 1 , further comprising calibrating the analyte sensor using a sensitivity measurement obtained from the signal associated with the analyte concentration of the reference solution. 
     
     
         7 . The method of  claim 1 , wherein the vascular access device and the analyte sensor are configured for fluid communication with a central vein of the host. 
     
     
         8 . The method of  claim 1 , wherein drawing back a sample comprises drawing back a sample at a flow rate of from about 0.001 ml/min to about 2 ml/min. 
     
     
         9 . A method for measuring a concentration of an analyte in a vein of a host, the method comprising:
 passing a reference solution at a first flow rate controlled by a flow control device past an analyte sensor configured to measure an analyte concentration, wherein the analyte sensor is a component of an analyte measuring system comprising a vascular access device, the analyte sensor, and electronics operatively connected to the analyte sensor and configured to generate a signal associated with the analyte concentration, wherein the analyte sensor resides within the vascular access device, and wherein the vascular access device and the analyte sensor are in fluid communication with a vein of a host;   measuring a signal associated with an analyte concentration of the reference solution;   drawing back a sample from the vein of the host at a second flow rate of from about 0.001 ml/min to about 2 ml/min; and   measuring a signal associated with an analyte concentration of the sample, wherein the second flow rate is different from the first flow rate.   
     
     
         10 . The method of  claim 9 , wherein the second flow rate is from about 0.02 ml/min to about 0.35 ml/min. 
     
     
         11 . The method of  claim 9 , wherein drawing back a sample comprises substantially blocking mixing of the reference solution and the sample. 
     
     
         12 . The method of  claim 9 , wherein drawing back a sample comprises drawing back a sample volume of from about 1 μl to about 2 ml from the vein. 
     
     
         13 . The method of  claim 9 , wherein the analyte is glucose, and wherein measuring the concentration of the analyte comprises measuring a glucose concentration. 
     
     
         14 . The method of  claim 9 , further comprising repeating passing and drawing. 
     
     
         15 . The method of  claim 14 , wherein repeating is at least one of periodically repeating or intermittently repeating. 
     
     
         16 . The method of  claim 9 , further comprising calibrating the analyte sensor using a baseline measurement obtained from the signal associated with the analyte concentration of the reference solution. 
     
     
         17 . The method of  claim 9 , further comprising calibrating the analyte sensor using a sensitivity measurement obtained from the signal associated with the analyte concentration of the reference solution. 
     
     
         18 . The method of  claim 9 , wherein the vascular access device and the analyte sensor are configured for fluid communication with a central vein of the host. 
     
     
         19 . The method of  claim 9 , wherein the first flow rate is from about 0.25 μl/min to about 10 ml/min. 
     
     
         20 . The method of  claim 9 , wherein the first flow rate is from about 0.001 ml/min to about 2 ml/min. 
     
     
         21 . A method for measuring a concentration of an analyte in a circulatory system of a host, the method comprising:
 passing a reference solution past an analyte sensor configured to measure an analyte concentration, the analyte sensor comprising a component of an analyte measuring system comprising a vascular access device, the analyte sensor, and electronics operatively connected to the analyte sensor and configured to generate a signal associated with the analyte concentration, wherein the analyte sensor resides within the vascular access device, and wherein the vascular access device and the analyte sensor are in fluid communication with a circulatory system of a host;   measuring a signal associated with an analyte concentration of the reference solution;   drawing back a sample from the circulatory system; and   measuring a signal associated with an analyte concentration of the sample, wherein the analyte measuring system further comprises a flow control device, wherein the flow control device is configured to meter flow during passing and drawing, and wherein the flow control device comprises a valve having a first pinch position and a second pinch position, wherein the first pinch position and the second pinch position are configured to at least partially pinch at least a portion of a tubing through which at least one of the reference solution is passed or the sample is drawn.   
     
     
         22 . The method of  claim 21 , wherein passing a reference solution comprises moving the valve from the first position to the second position. 
     
     
         23 . The method of  claim 21 , wherein drawing back a sample comprises moving the valve from the second position to the first position. 
     
     
         24 . The method of  claim 21 , further comprising keeping the vein open by metering a flow of the reference solution through the vascular access device at a predetermined rate. 
     
     
         25 . The method of  claim 24 , wherein metering the flow is controlled at least in part by a timing of the valve movement between the first position and the second position. 
     
     
         26 . The method of  claim 21 , wherein the valve meters a volume of at least one of the reference solution or the sample of from about 1 μl to about 2 ml during movement between the first pinch position and the second pinch position. 
     
     
         27 . The method of  claim 21 , wherein the valve meters a flow of at least one of the reference solution and the sample at a flow rate of from about 0.001 ml/min to about 2 ml/min during movement between the first pinch position and the second pinch position. 
     
     
         28 . The method of  claim 21 , wherein the valve is a rotating pinch valve. 
     
     
         29 . A method for measuring a concentration of an analyte in a circulatory system of a host, the method comprising:
 passing a reference solution past an analyte sensor configured to measure an analyte concentration, wherein the analyte sensor is a component of an analyte measuring system comprising a vascular access device, the analyte sensor, and electronics operatively connected to the analyte sensor and configured to generate a signal associated with the analyte concentration, wherein the analyte sensor resides within the vascular access device, and wherein the vascular access device and the analyte sensor are in fluid communication with a circulatory system of a host;   measuring a signal associated with an analyte concentration of the reference solution;   drawing back a sample from the circulatory system; and   measuring a signal associated with the analyte concentration of the sample, wherein the analyte measuring system further comprises a flow control device, wherein the flow control device comprises a valve comprising a first discrete position and a second discrete position, wherein the valve is configured to meter flow in a first direction during passing and in a second direction opposite to the first direction during drawing, wherein drawing back a sample comprises drawing back a sample volume of about 500 microliters or less during movement of the valve from the second discrete position to the first discrete position.   
     
     
         30 . The method of  claim 29 , wherein a sample volume of about 300 microliters or less is drawn back.