The Wagner-Nelson method can generate an accurate gastric emptying flow curve from CO2 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 (13C) breath test attempts to estimate the rate of absorption of 13C, as an index of gastric emptying rate, from the rate of pulmonary elimination of 13CO2. 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 = Abreath (t)/Abreath (infinity) + (1/0.65).d[Abreath (t)/Abreath (infinity) ]/dt, where Abreath (t) = the cumulative recovery of 13CO2 in breath by time t and Abreath ( infinity ) = the ultimate cumulative 13CO2 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 13CO2 data, and it can adjust the difference between ultrasonography and the breath test.
Sanaka
Masaki
M
Department of Internal Medicine, Tokyo Metropolitan Komagome Hospital, Tokyo, Japan.
Yamamoto
Takatsugu
T
Ishii
Tarou
T
Kuyama
Yasushi
Y
D000328:Adult; D019540:Area Under Curve; D001944:Breath Tests / Q000379:methods; D002245:Carbon Dioxide / Q000378:metabolism*; D002247:Carbon Isotopes / Q000493:pharmacokinetics; D005746:Gastric Emptying / Q000502:physiology*; D006801:Humans; D007408:Intestinal Absorption; D008297:Male; D017711:Nonlinear Dynamics; D010599:Pharmacokinetics
D002247:Carbon Isotopes; D002245:Carbon Dioxide