A NEW FIBER OPTIC UMBILICAL ARTERIAL CATHETER FOR CONTINUOUS OXYHEMOGLOBIN SATURATION MEASUREMENT

A new dual lumen polyurethane umbilical arterial catheter containing fiber optics was placed in 29 sick infants. One lumen is used to measure pressure and sample blood, the other lumen contains fiber optics which transmit 3 wavelights of red light. The light reflected from the blood is measured and converted to a digital and analogue display of oxyhemoglobin saturation (SaO₂). The instrument is calibrated before insertion and has a time constant of 5 secs. Regression analysis of 129 paired values using a cuvette oximeter (1.L.182) shows great accuracy (r=0.977, S.D. ±2.46). Oxygen concentration or transpulmonary distending pressure were adjusted to maintain SaO₂ between 87 and 95% in infants with HbF and 85 to 93% in infants with transfused HbA blood. PaO₂ measured 1503 times was between 45-85 torr at these values. Abnormal serum electrolytes and indirect bilirubin up to 18 mg/dl did not affect accuracy. In 22 prematurely delivered infants measurements began 3-26 min after birth (mean 8.5 min). SaO₂ was as low as 10% in severely asphyxiated infants. The effect of a change in assisted ventilation was immediately indicated on the digital display. Complications such as pneumothorax, pulmonary hemorrhage, pulmonary edema, patent ductus arteriosus and alveolar capillary air embolism were diagnosed and treated with the help of continuous monitoring. In one infant during apnea, SaO₂ fell below 85%, triggering an alarm before the conventional respiratory alarm responded.