A photometric device for measuring blood vessel diameter in the microcirculation.

A simple photometric device has been developed for measuring changes in blood vessel diameter in the microcirculation in conjunction with a monochrome television microscope. The device consists of a photocell mounted at the end of a small conical hood, which is attached to the screen of the television monitor. The photocell responds to changes in light emitted from the screen during dilatation or constriction of a blood vessel, and a continuous record of these changes is obtained by displaying the output from the photocell on a pen recorder. By using one or more photocells, mounted in separate hoods, the diameter of a number of vessels can be recorded simultaneously. The device has been used to record changes in the diameter of precapillary arterioles and postcapillary venules in the hamster cheek pouch microcirculation. The device has the advantage over image-shearing techniques of being automatic, and it is also considerably less expensive than a number of automated electro-optical or scanning systems.