Journal of Applied Physiology, Vol 44, Issue 4 528-533, Copyright © 1978 by American Physiological Society
Continuous measurement of gas partial pressures in intracerebral tissue
J. Seylaz and E. Pinard
A mass spectrograph technique has been developed for measurement of
physiological gas partial pressures locally in the brain. The sampling
cannula is implanted stereotaxically and remains in situ for several weeks.
It is a thin cylinder in shape, and is covered with a thin polyethylene
membrane across which gas molecules can be sampled continuously. The
conductance of this membrane is well adapted to the limited rate of
replacement of gas molecules afforded by the cerebral tissue, hence there
is no depletion around the cannula; this depletion has until now been the
major problem of this technology. The present technique provides a
continuous measurement with fast response time, which is directly
proportional to the partial pressures of the gases. The variations can be
expressed as a percentage of the base-line value.
