Computerized curve fitting in the analysis of hydrogen gas clearance curves

1989 ◽  
Vol 257 (4) ◽  
pp. G668-G675 ◽  
Author(s):  
E. H. Livingston ◽  
T. Reedy ◽  
F. W. Leung ◽  
P. H. Guth
Keyword(s):  
Blood Flow ◽  
Linear Regression ◽  
Nonlinear Regression ◽  
Curve Fitting ◽  
Regression Line ◽  
Hydrogen Gas ◽  
Base Line ◽  
Hydrogen Gas Clearance ◽  
Experimental Noise ◽  
Fitting In

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.

Dissociated effects of somatostatin on gastric acid secretion and mucosal blood flow

1985 ◽  
Vol 248 (3) ◽  
pp. G337-G341
Author(s):  
F. W. Leung ◽  
P. H. Guth
Keyword(s):  
Blood Flow ◽  
Acid Secretion ◽  
Gastric Acid Secretion ◽  
Gastric Acid ◽  
Acid Output ◽  
Mucosal Blood Flow ◽  
Hydrogen Gas ◽  
Gastric Acid Output ◽  
Hydrogen Gas Clearance ◽  
Blood Flows

Somatostatin has been reported to control upper gastrointestinal hemorrhage, prevent restraint stress-induced gastric ulcerations, and inhibit gastric acid secretion. In this study we examined the effect of somatostatin on basal and pentagastrin-stimulated gastric acid output and mucosal blood flow. Antral and corpus mucosal blood flows were measured by hydrogen gas clearance in fasted, anesthetized rats. Acid output was determined by a continuous gastric perfusion technique. In the basal study somatostatin in doses of 8, 16, and 32 micrograms . kg-1 . h-1 was infused intravenously in separate groups of animals. In the pentagastrin stimulation study somatostatin (16 micrograms . kg-1 . h-1) was infused after gastric acid output was stimulated to plateau by intravenous pentagastrin (19.8 micrograms . kg-1 . h-1). The results showed that somatostatin had no effect on basal corpus or antral mucosal blood flow. During pentagastrin stimulation somatostatin decreased acid secretion but increased corpus mucosal blood flow. We speculate that this increase in blood flow may not be a direct effect as basal corpus or antral mucosal blood flow was unaffected by somatostatin.

scholarly journals -19-INTRAOPERATIVE MEASUREMENT OF MYOCARDIAL BLOOD FLOW BY ELECTROLYTIC HYDROGEN GAS CLEARANCE METHOD

1986 ◽  
Vol 50 (6) ◽  
pp. 464-465
Author(s):  
Fumio Kawajiri ◽  
Michio Kawasuji ◽  
Takekazu Aoyama ◽  
Naoki Sakakibara
Keyword(s):  
Blood Flow ◽  
Myocardial Blood Flow ◽  
Hydrogen Gas ◽  
Hydrogen Gas Clearance ◽  
Electrolytic Hydrogen

Measurements of gastric mucosal blood flow by hydrogen gas clearance

1984 ◽  
Vol 247 (4) ◽  
pp. G339-G345
Author(s):  
S. W. Ashley ◽  
L. Y. Cheung
Keyword(s):  
Blood Flow ◽  
Gas Flow ◽  
Mucosal Blood Flow ◽  
Gastric Mucosal Blood Flow ◽  
Close Correlation ◽  
Hydrogen Gas ◽  
Low Flow ◽  
Gas Mixture ◽  
Hydrogen Gas Clearance ◽  
Flow Rates

The validity of the use of H2 gas clearance to measure gastric mucosal blood flow (GMBF) was investigated in the intact stomach of anesthetized dogs. With a modified, more sensitive platinum electrode, we were able to reduce the H2 gas concentration to a nonflammable gas mixture. GMBF was repeatedly measured when the dogs inhaled gas containing 100, 10, and 3-5% H2. GMBF measured using 100% H2 demonstrated close correlation with inhaled gases containing 10% H2 (r = 0.84, slope = 0.89) and 3-5% H2 (r = 0.91, slope = 0.88). At a nonflammable concentration of 3% H2, it was safe to add 20% O2 into the gas mixture. The addition of O2 into the inhaled gas eliminated the transient hypoxia noted otherwise. It was also possible to reduce the gas flow rate from 5-10 to 1-3 l/min. Regression analysis of GMBF determined by inhalation of 5% H2 at these flow rates revealed a significant linear correlation (r = 0.95, slope = 1.13). In 10 dogs GMBF determined by using these low concentrations of H2 at the low flow rates also showed a good agreement (r = 0.93, slope = 0.65) with that measured by radioactive microspheres. These two methods also demonstrated comparable changes in GMBF induced by intravenous infusion of histamine and vasopressin. It was concluded that, with the technique as modified in our laboratory, H2 gas clearance could be a safe and accurate tool for quantitating gastric mucosal blood flow.

Time course and determinants of recovery of function after reversible ischemia in conscious dogs

1988 ◽  
Vol 254 (1) ◽  
pp. H102-H114 ◽  
Author(s):  
R. Bolli ◽  
W. X. Zhu ◽  
J. I. Thornby ◽  
P. G. O'Neill ◽  
R. Roberts
Keyword(s):  
Blood Flow ◽  
Time Course ◽  
Contractile Function ◽  
Recovery Of Function ◽  
Regression Line ◽  
Systolic Pressure ◽  
Conscious Dogs ◽  
Rate Pressure Product ◽  
Wall Thickening ◽  
Base Line

The postischemic recovery of contractile function [measured as systolic wall thickening (WT)] was analyzed in 21 conscious dogs undergoing a 15-min coronary occlusion followed by 7 days of reperfusion (REP). Average WT was still depressed 24 h after REP (85% of base line, P less than 0.001) and returned to base line by 48 h. Analysis of individual dogs, however, revealed marked variability, whereby some recovered completely by 1 h of REP and others required up to 48 h. WT recovered completely within 30 min in dogs with collateral blood flow (CBF) greater than 50% of nonischemic zone flow (NZF) but was still impaired at 24 h (P less than 0.05) in those with CBF less than 25% of NZF. There was a close, curvilinear relation between WT during the first 4 h of REP and transmural CBF, which was described best by an exponential equation WT (as percent of base line) = P0-P1e-P2.CBF(as % of NZF) (r2 = 0.92 at 1 h, 0.76 at 2 h, 0.71 at 3 h, and 0.72 at 4 h), where P0, P1, and P2 are regression coefficients. Importantly, the slope of the regression line was very steep at low CBF, implying that even small differences in CBF produce large differences in postischemic function. Heart rate, systolic pressure, and rate-pressure product during ischemia were also related to WT after REP, but when the effect of CBF was taken into account, the influence of these variables became insignificant. The size of the occluded vascular bed did not correlate with postischemic WT. The presence of hypokinesis or akinesis during ischemia was associated with rapid recovery after REP, but there was no relation between ischemic and postischemic dysfunction when dyskinesis was present during occlusion. Thus, on the average, regional function remains depressed for 24 h after a 15-min ischemic episode, but there is considerable individual variability. This variable rate of recovery is determined primarily by the severity of blood flow reduction during ischemia. Systemic hemodynamics may modulate recovery of function indirectly via their effects on ischemic blood flow.

Role of blood flow and alkaline secretion in acid-induced deep duodenal villous injury in rats

1991 ◽  
Vol 260 (3) ◽  
pp. G399-G404 ◽  
Author(s):  
F. W. Leung
Keyword(s):  
Blood Flow ◽  
Histological Examination ◽  
Simultaneous Measurement ◽  
Hydrogen Gas ◽  
Corticotropin Releasing Factor ◽  
Hydrogen Gas Clearance ◽  
Anesthetized Rats ◽  
Back Titration ◽  
Alkaline Secretion

The effect of 16,16-dimethylprostaglandin E2 (dmPGE2) and corticotropin-releasing factor (CRF) on duodenal blood flow, alkaline secretion, and acid-induced deep duodenal villous injury was studied. The duodena of anesthetized rats were prepared for simultaneous measurement of alkaline secretion by back titration, and blood flow by hydrogen gas clearance; or for perfusion with 0.1 N HCl and histological examination of villous injury. The results revealed that the dmPGE2-induced increase in basal alkaline secretion (due solely to an increase in the volume of secretion) appears to be a better predictor of protection against exogenous acid-induced deep duodenal villous injury than rise in duodenal blood flow, since CRF induces a similar rise in duodenal blood flow but does not enhance alkaline secretion or reduce acid-induced villous damage. The absence of a greater loss of H+ during acid perfusion of the duodenum in the dmPGE2-treated rats, however, suggests that the mechanism of the dmPGE2 protection against acid-induced deep duodenal villous injury cannot be explained entirely by its ability to increase basal duodenal alkaline secretion.

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