Result of pH monitoring with the Cordis pH ISFET catheter and signal conditioner during spontaneous breathing. (By permission of Sentron, Roden, The Netherlands.)
Furthermore, one can conclude from this registration and from others not given here, that during spontaneous breathing the blood pH may vary by at least 0.06 pH units. This indicates that the pH determination of an arbitrary blood sample within an accuracy of 0.001 pH unit, as is possible with modern pH-blood gas analysers, is physiologically insignificant.