Air contamination in umbilical cord blood gas sampling

The effect of air contamination when measuring umbilical cord blood gases can be minimized by drawing blood samples into 1 milliliter (ml) syringes. However, air contamination does not appear to affect the measurements used to evaluate fetal asphyxia. Clinical circumstances were simulated in order to evaluate the effect of time and air contamination on umbilical cord blood samples drawn after birth for blood gas analysis. Umbilical cord blood was collected from 21 healthy, term infants. Blood gases from samples with varying amounts of air in the syringe were compared with gases from air-free syringes. Air contamination had no effect on carbon dioxide levels, pH, or bicarbonate, the parameters used to evaluate fetal asphyxia. Oxygen level was affected by exposure to more than 38% air in a 3 ml syringe, but air contamination had no effect in a 1 ml syringe. The interval between birth and the last sample collected ranged from 26 to 96 minutes and did not affect results.