Journal of Applied Physiology, Vol 44, Issue 2 254-257, Copyright © 1978 by American Physiological Society
Colloid osmotic pressure changes of dog's blood exposed to different mixtures of CO2 and air
Y. Kakiuchi, A. B. DuBois and D. Gorenberg
Hansen's membrane manometer method for measuring plasma colloid osmotic
pressure was used to obtain the osmolality changes of dogs breathing
different levels of CO2. Osmotic pressure was converted to osmolality by
calibration of the manometer with saline and plasma, using freezing point
depression osmometry. The addition of 10 vol% of CO2 to tonometered blood
caused about a 2.0 mosmol/kg H2O increase of osmolality, or 1.2% increase
of red blood cell volume. The swelling of the red blood cells was probably
due to osmosis caused by Cl- exchanged for the HCO3- which was produced
rapidly by carbonic anhydrase present in the red blood cells. The change in
colloid osmotic pressure accompanying a change in co2 tension was measured
on blood obtained from dogs breathing different CO2 mixtures. It was
approximately 0.14 mosmol/kg H2O per Torr Pco2. The corresponding change in
red cell volume could not be calculated from this because water can
exchange between the plasma and tissues.
