Journal of Applied Physiology, Vol 51, Issue 1 232-237, Copyright © 1981 by American Physiological Society
Boundary-layer oxygen depletion in blood gas analysis
S. Venkatesh and G. Cumming
When O2 is withdrawn from blood by diffusion through a membrane and an
O2-depleted boundary layer is formed, it is suggested that the depletion
can cause significant dissociation of oxyhemoglobin (HbO2) in this layer.
The resulting nonlinear relation between net diffusive flux of O2 through
the membrane and the blood PO2 should be observable with membrane systems
having a sufficiently high permeability to O2. Evidence for this suggestion
is presented from in vitro experiments using a mass spectrometer to analyze
the O2 flux through membrane systems. A theoretical model of HbO2
dissociation in the depleted boundary layer of blood that explains these
results qualitatively is developed to yield quantitative predictions found
to be in reasonable agreement with the experimental observations. The
effect was seen to be of significance for membrane systems with O2-sampling
rates of about 2 X 10(-9) ml. s-1. Torr-1 and over; so if such systems are
to be used for the analysis of blood PO2, the phenomenon must be taken into
account.
