Journal of Applied Physiology, Vol 61, Issue 4 1534-1545, Copyright © 1986 by American Physiological Society
Nitrogen gas exchange in the human knee
P. K. Weathersby, P. Meyer, E. T. Flynn, L. D. Homer and S. Survanshi
Human decompression sickness is presumed to result from excess inert gas in
the body when ambient pressure is reduced. Although the most common symptom
is pain in the skeletal joints, no direct study of nitrogen exchange in
this region has been undertaken. For this study, nitrogen tagged with
radioactive 13N was prepared in a linear accelerator. Nine human subjects
rebreathed this gas from a closed circuit for 30 min, then completed a 40-
to 100-min washout period breathing room air. The isotope 13N was monitored
continuously in the subject's knee during the entire period using positron
detectors. After correction for isotope decay (half-life = 9.96 min), the
concentration in most knees continued to rise for at least 30 min into the
washout period. Various causes of this unexpected result are discussed, the
most likely of which is an extensive redistribution of gas within avascular
knee tissues.
