Effect of SF6-O2 (80/20) breathing on air bubbles in rat tissues

We studied the effect of SF6-O2 breathing on air bubbles injected into skeletal muscle, rat-tail tendon, the anterior chamber of the eye, and spinal white matter. Decompression-induced nitrogen bubbles in adipose tissue were studied during breathing of SF6-O2 (80/20). The results of SF6-O2 breathing are compared with previous experiments using heliox (80/20) as the breathing medium. Bubbles studied in skeletal muscle, eye chamber, and spinal white matter were found to behave in a two-phased manner during SF6-O2 (80/20) breathing. All bubbles would initially decrease rapidly in size for a period of 10-80 min (depending on the tissue). Subsequently, the bubbles stabilized and decreased in size with a shrinking rate near zero. In spinal white matter, very small bubbles decreased size with a shrinking rate near zero. In spinal white matter, very small bubbles could disappear before development of the slow phase. All bubbles in tendon shrank at a rather constant rate during SF6-O2 (80/20) breathing until they disappeared. During SF6-O2 (80/20) breathing, all bubbles in adipose tissue shrank and disappeared at least as fast as during heliox (80/20) breathing. Just before disappearance of the bubbles the shrinking rate slowed. Comparison of the effects of SF6-O2 (80/20) and heliox (80/20) breathing suggests that countercurrent gas exchange is at work in some tissues.