A new laser Doppler interface for the continuous measurement of the rat gastric mucosal blood flow

The laser Doppler system (LD) has been proposed for a tissue blood flowmetry. However, its accuracy is dependent on the pressure and direction of the laser probe. Therefore, we have devised a new interface for the measurement of the gastric mucosal blood flow in rats keeping the probe constant in pressure and direction. This interface is a small cylinder with one end fixed upon the gastric serosa and the other end fixed externally upon the skin. The laser probe adjusts exactly in direction and pressure inside this button. The LD apparatus processes two shifted beams with a differential amplification and a root mean square. It delivers an index (LDI) from 0 to 10. This interface was tested in 3 groups of rats, comparing the mucosal (open stomach) with the serosal gastric LDI and the same serosal LDI with a 133Xe washout flow. Finally, the interface was used in control and restrained rats. The gastric serosal LDI was found to be similar to the mucosal LDI. The correlation between the LDI and the 133Xe washout flow was good, with a coefficient of 0.9. Finally, the LDI of the gastric mucosal blood was significantly different in control and stressed rats. This new interface makes the LD more reliable for the monitoring of gastric mucosal flowmetry. It has the same accuracy as the xenon washout and additionally it is simpler, cheaper and may be repeated or even be used continuously.