“…The right upper lobe of an anesthetized dog was isolated in vivo by a balloon catheter and artificially ventilated with nitrogen (N2), air or 60% oxygen (02) in nitrogen mixed with a trace amount of helium (He), while the rest of the lungs was breathing air spontaneously as reported previously (Isawa et al 1978a(Isawa et al , b, 1979(Isawa et al , 1980(Isawa et al , 1981. Each perfusion percentage in the right upper lobe when the lobe was artificially ventilated with N2, air and 60% 02 in N2, respectively was measured by a scintillation camera (RC-IC-1205, Hitachi Medical Corporation, Tokyo) after sequentially injecting 99mTc-albumin microsphere (TCK-5, SORIN, Salingia, Italy) as a tracer material.…”