The accuracy of continuous interstitial fluid glucose sensing is an essential component of current and emerging open and closed loop systems for type 1 diabetes. An important determinant of sensor accuracy is the physiological time lag of glucose transport from the vascular to the interstitial space. We have performed the first direct measurement of this phenomenon in 8 healthy subjects under overnight fasted condition. Microdialysis catheters were inserted into the abdominal subcutaneous space. After intravenous bolus administrations of glucose tracers, timed samples of plasma and interstitial fluid were collected sequentially and analyzed for tracer enrichments. After accounting for catheter dead space and assay noise, the mean time lag of appearance of tracer into the interstitial space after intravenous bolus was 5.3 to 6.2 minutes. We conclude that in the overnight fasted state in healthy adults, the physiological delay of glucose transport from the vascular to the interstitial space is 5-6 minutes. Physiological delay between blood glucose and interstitial fluid glucose should, therefore, not be an obstacle to sensor accuracy in overnight or fasting state closed loop systems of insulin delivery or open loop therapy assessment for type 1 diabetes.
- Received July 22, 2013.
- Accepted August 30, 2013.
- © 2013 by the American Diabetes Association.
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