Figure 1.

Example of the graphical representation of the extrapolation to zero-flow method. Using non-linear curve fitting to the equation described by Jacobson et al.¹⁸ (see equation (2) in the manuscript), the concentration in the matrix and in the extracellular fluid (C₀ in equation (2)) corresponds to the y-intercept. (a) In vitro extrapolation of the glucose data for catheter # 5. The estimated C₀ was 1.65 mmol/L, the value of k (where k = rA in equation (2)) was 1.17 mm/min, and the measured C₀ for glucose was 2.06 mmol/L. (b) In vivo extrapolation of the glucose data for patient # 12 (C₀ = 3.43 mmol/L, k = 0.18 mm/min). (c) In vivo extrapolation of the lactate data for patient # 12 (C₀ = 3.28 mmol/L, k = 0.14 mm/min). (d) In vivo extrapolation of the pyruvate data for patient #12 (C₀ = 169 mmol/L, k = 0.11 mm/min).