Distribution of xenon gas exchange rates in dogs

The kinetics of xenon gas uptake and elimination in seven anesthetized dogs were studied by simultaneous external recording of gas concentrations in several thousand anatomic sites during 7-h experiments. The data were analyzed by a previously described method of extracting moments of the distribution of gas residence times. Mean residence times (first moment) varied by more than a factor of 50 within a single animal: the fastest exchange was in the lungs (under 2 min), and progressively slower exchange occurred in the brain, spinal cord, ears, peripheral joints, and shoulder (over 2 h). Variance of the residence time (second moment) was found to approximate four times the mean residence time squared. This ratio was nearly the same throughout the body. Indications of unexpectedly high xenon solubility in the ear and joint regions were also found.