title: Computerized curve fitting in the analysis of hydrogen gas clearance curves.
abstract: Hydrogen gas clearance curves obtained from the rat gastric corpus were digitized into a computer and then analyzed by three methods: 1) linear regression of log-transformed data, 2) direct curve fitting with a modified Gauss-Newton nonlinear regression algorithm, and 3) Zierler's height-over-area algorithm. For linear regression of log-transformed data, if the initial base-line estimate was inaccurate or normal amounts of experimental noise were present, the log-transformed data was skewed, leading to deviation of the regression line and incorrect estimation of blood flow. By utilization of the direct-fit routine, the initial estimate of the parameters or experimental noise had little influence on the blood flow determination because of iterative improvement of the parameters. In a study of isoproterenol-stimulated gastric blood flow, Zierler's algorithm underestimated the blood flow estimate. We conclude that analysis of hydrogen gas clearance curves by linear regression of log-transformed data or by Zierler's algorithm may potentially introduce errors in blood flow estimates that may be avoided by analysis with a direct-fitting, nonlinear regression algorithm.
authors: Surgical Service, West Los Angeles, Veterans Administration Medical Center, California.
authors: E H
authors: EH
authors: Livingston
authors: T
authors: T
authors: Reedy
authors: F W
authors: FW
authors: Leung
authors: P H
authors: PH
authors: Guth
mesh_terms: D000465:Algorithms; D000818:Animals; D005753:Gastric Mucosa / Q000098:blood supply*; D006859:Hydrogen; D008297:Male; D008433:Mathematics; D008722:Methods; D008962:Models, Theoretical; D051381:Rats; D011919:Rats, Inbred Strains; D012039:Regional Blood Flow; D012044:Regression Analysis
chemical_list: D006859:Hydrogen