The Wagner-Nelson method can generate an accurate gastric emptying flow curve from 13CO2 data obtained by a 13C-labeled substrate breath test

Background: In pharmacokinetics, the Wagner-Nelson (W-N) method can accurately estimate the rate of drug absorption from its urinary elimination rate. A stable isotope (C-13) breath test attempts to estimate the rate of absorption of C-13, as an index of gastric emptying rate, from the rate of pulmonary elimination of (CO2)-C-13. The time-gastric emptying curve determined by the breath test is quite different from that determined by scintigraphy or ultrasonography. In this report, we have shown that the W-N method can adjust the difference. Methods: The W-N equation to estimate gastric emptying from breath data is as follows: the fractional cumulative amount of gastric contents emptied by time t=A(breath)(t)/A(breath)(infinity) +(1/0.65).d[A(breath)(t)/A(breath)(infinity)]/dt, where A(breath)(t)=the cumulative recovery of (CO2)-C-13 in breath by time t and A(breath)(infinity)=the ultimate cumulative (CO2)-C-13 recovery. The emptying flow curve generated by ultrasonography was compared with that generated by the W-N method-adjusted breath test in 6 volunteers. Results: The emptying curves by the W-N method were almost identical to those by ultrasound. Conclusions: The W-N method can generate an accurate emptying flow curve from (CO2)-C-13 data, and it can adjust the difference between ultrasonography and the breath test. Copyright (C) 2004 S. Karger AG, Basel.