Focal gastric mucosal blood flow by laser-Doppler and hydrogen gas clearance: a comparative study.

We compared focal gastric mucosal blood flow (GMBF) values simultaneously obtained by laser-Doppler flowmetry (LDF) and hydrogen gas clearance (HGC) from the same point in a chambered segment model of the gastric corpus in two sets of experiments (Experiments 1 and 2) involving nine anesthetized dogs (weighing 20-30 kg). We also investigated the feasibility of obtaining a conversion factor for LDF signal to absolute flow values. The GMBF values showed a highly significant linear correlation within individual experiments and for the combined data in experiments 1 (r = 0.7132, P less than 0.0001, n = 37) and 2 (r = 0.5660, P less than 0.0001, n = 61). The combined data did not corroborate a common regression line hypothesis in both experiments (Experiment 1: F = 6.59, P less than 0.0005; Experiment 2: F = 10.57, P less than 0.0005). There was a statistically significant difference between the slopes of the 5 and 4 linear regression lines obtained in Experiments 1 (F = 13.15, P less than 0.0005) and 2 (F = 21.14, P less than 0.0005), respectively. The LDF signal was stable and optical coupling is not a problem in this experimental model. HGC and GMBF values were reliable and highly reproducible within dog measurements. We conclude that LDF and HGC are comparable in the measurement of focal GMBF. Our data, however, did not suggest the existence of a conversion factor for LDF signal to absolute flow values from experiment to experiment. Conversion will have to be within individual experiments. Thus, LDF may only be useful in situations where qualitative changes in focal blood flow are investigated.

Focal gastric mucosal blood flow in aspirin-induced ulceration.

Focal gastric mucosal blood flow was studied during aspirin injury by hydrogen gas clearance in a chambered segment model of canine gastric corpus. Measurements were made simultaneously every 15 minutes at ulcerated and nonulcerated areas 1.5 hours before, during (20 mM of aspirin in 150 mM of HCl for 1 hour), and 2 hours after exposure of the mucosa to topical aspirin. There was a highly significant decrease (p less than 0.001) in flow at the ulcerated areas 30 minutes after exposure to aspirin, coinciding with the appearance of focal mucosal pallor followed by subsequent hemorrhagic foci and ulceration. This was not followed by recovery to basal flow values. Blood flow to the non-ulcerated areas was significantly but less severely reduced than in the ulcerated areas (p less than 0.05) 90 minutes after exposure to aspirin. This was followed by recovery to basal levels. It is proposed that aspirin induces reduction of focal mucosal blood flow of varying degrees and that mucosal areas with flow reduced to below a "critical value" develop gross damage.