Continuous intra-arterial pH-monitoring using monocrystalline antimony as sensor. A study in non-heparinized dogs

Continuous intra-arterial pH-monitoring was performed on anaesthetized and artificially ventilated dogs. The pH sensor consisted of monocrystalline antimony. The sensor was placed on the tip of a catheter, length approximately 35 cm and diameter 0.8 mm. No anticoagulation was undertaken. The pH range studied was 7.01-7.53, the pH being changed by infusion of sodium bicarbonate ro ammonium chloride. Arterial reference blood samples for in vitro blood gas analyses were taken under stable monitoring conditions and analysed with a minimal delay. The millivolt signal from the antimony sensor was found to be a linear function of the pH of the reference blood samples in the intra-arterial pH range studied. The sensitivities of the different antimony sensors were closely correlated but not identical. When the antimony sensor was used completely uncalibrated, the standard deviation of the registered potential corresponds to 0.06 pH units. After single point calibration a standard deviation of 0.03 pH units was obtained. These standard deviations include a suspected influence of minor changes in the partial pressure of oxygen during the experiments.