[Microcirculation during inhalation of 100% oxygen in rabbits]

Using a rabbit ear chamber (REC), the author compared the effect of air inhalation and that of 100% oxygen inhalation on microcirculation of rabbits. Eight rabbits, weighing 3-4 kg, were used for this study. After observing the microcirculation under air inhalation, the inspired gas was changed to 100% oxygen and the microcirculation was again observed. This procedure was repeated twice to confirm any changes that had been observed. No significant changes were observed in the blood pressure, heart rate and pulse pressure by inhaling either O2 concentration. During the inhalation of 100% oxygen, the diameter, blood-flow velocity and blood-flow rate of the arterioles were markedly reduced (P less than 0.01). All these parameters observed in the venules during air inhalation showed no significant differences compared with the values taken during 100% oxygen inhalation. This study using REC has shown that inhalation of 100% oxygen causes microcirculatory changes especially affecting the arterioles.