Laser doppler flowmetry for estimating microcirculatory function in response to prolonged inhaled nitric oxide applications

Abstract

The aim of this study was to evaluate the effects of the long-term use of inhaled nitric oxide on blood microcirculation in skin blood vessels of healthy rats. The experiment was performed using 40 adult male Wistar rats. The animals in the first group (n = 10) were the controls, which were kept without any manipulations. The animals in the second, third, and fourth groups received daily inhaled nitric oxide during 30 days (the concentrations of NO in the gas stream were 20, 50, and 100 ppm, respectively, for these groups). Upon completion of the full course of nitric oxide inhalation the state of the microcirculation was studied in all groups of animals. The estimated parameters were the microcirculation index, the amplitudes of the main regulatory factors (endothelial, neurogenic, myogenic, respiratory, and cardiac), and the rate of bypass coefficient. Our research demonstrated that during the long-term use of nitric oxide inhalation for up to 30 days a dose-dependent effect of NO on microcirculatory function was observed; the most effective response was seen when the low dose of the compound at a rate of 20 ppm was used. This effect is obtained both by the dynamics of the total intensity of the blood flow in microvessels and the relative activity of the involved regulatory mechanisms.