End-tidal PCO2 measurements sampled at the distal and proximal ends of the endotracheal tube in infants and children.

To determine whether the site of gas sampling affects end-tidal gas measurements in pediatric patients, end-tidal PCO2 was measured continuously from the distal and proximal ends of the endotracheal tube in 60 infants and children ventilated with an Air-Shields Ventimeter and a partial rebreathing circuit. These data were compared with simultaneous arterial PCO2 measurements. In infants and children weighing greater than or equal to 12 kg, both distal and proximal end-tidal PCO2 values approximated arterial PCO2 measurements. In infants and children weighing less than 12 kg, however, only distal end-tidal PCO2 measurements approximated arterial PCO2 measurements. It is concluded that in infants and children weighing less than 12 kg, accurate end-tidal measurements can be obtained only from the distal end of the endotracheal tube.