Estimation of Relative Changes in Resting Muscle Blood Flow by ¹³³Xe Washout: The Effect of Oxygen

Abstract

¹³³Xe washout from resting anterior tibial muscle was studied in the 10 to 30-minute period after injection of ¹³³Xe. The elimination curves were not strictly monoexponential, but presented a slight spontaneous decrease in rate constant during the period. An experimental design is presented which permits the detection of small, induced changes in muscle blood flow despite this spontaneous decrease in rate constant. Errors in the determination of resting muscle blood flow from ¹³³Xe washout are discussed. It is concluded that relative changes in resting muscle blood flow may be overestimated when calculated from changes in ¹³³Xe elimination rate constants. Oxygen breathing at 1 atm. was shown to reduce resting muscle blood flow.

Key Words:

• Man
• oxygen breathing
• resting muscle blood flow
• veno-arterial diffusion shunts
• ¹³³Xenon washout technique