Gated laser Doppler flowmetry using a proximity-contact probe

Laser Doppler flowmetry (LDF) is a convenient way to measure gastric microcirculation, but it is sensitive to respiration movements and physical contact with the gastric surface. The authors modified a laser probe to measure the potential difference across the gastric wall as the distance between the probe and the wall changes. This potential difference signal was used to gate the LDF velocity during the respiration cycle, and to detect any times when the probe was in direct contact with the surface. During periods of intermittent contact, gating lowered the mean blood velocity signal 10 to 25%. During periods of continuous contact, the mean velocity increased 1.5 to 2 times, while instantaneous velocity decreased as the instantaneous pressure increased.<>