Microvascular oxygen transport: development of an optical triplicator

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Virginia Tech

Microvascular oxygen transport has been studied using many experimental methods. The three wavelength photometric method of Pittman and Duling (6) was the basis for this project. An optical triplicator was introduced into the microscopy assembly. The triplicator’s function was to take the image seen in the eyepiece of the microscope, triplicate it, filter it at three known wavelengths and direct each image onto the active area of a video camera. When used in-vivo, the triplicator allowed for three simultaneous intensity measurements, one at each wavelength, to be made. This measurement removed any assumptions concerning the uniformity of the blood sample which was inherent in Pittman and Duling’s design. Measurements were performed in vivo on several hamster retractor muscles. The intensity information obtained was then used to calculate oxygen saturation at regions near an arterial bifurcation. Oxygen saturation values ranged from 42.99 ± 4.20 to 96.46 ± 4.46% depending upon the location along the vessel. It was also concluded that the oxygen saturation profile across the vessel was altered near a bifurcation. The oxygen saturation profile prior to and following a bifurcation appeared to be uniform. However, in the region of a bifurcation, the asymmetry introduced nonuniformities in the profile.

This paper briefly discusses the theory behind the three wavelength photometric method, the development and fabrication of the optical triplicator and the measurement techniques used to obtain oxygen saturation profiles. It will be shown that the optical triplicator has the potential to advance the study of microvascular oxygen transport beyond previously unachievable levels.