Measurement of oxygen uptake in newborn infants during assisted and spontaneous ventilation

Measurements of oxygen uptake (V O 2 ) and CO 2 output (V CO 2 ) are useful in critically ill patients. However, V O 2 is not routinely measured in intensive care during mechanical ventilation (MV) especially in premature newborns. The present study describes a new method of measuring V O 2 and V O 2 using a double open circuit which accounts for gas leaks around the uncuffed tracheal tube. The accuracy of the method was assessed with N 2 and CO 2 infusion. In case of leaks, V O 2 and V O 2 measurement was significantly underestimated by the simple circuit method. This underestimation was not present with double circuit method. Five preterm newborns were studied. V O 2 adn V CO 2 using the double open circuit were compared with the classic simple circuit. During MV, the mean underestimation assessed by the difference between simple and double circuit measurement was −12% (range from 0 to −29%) for V O 2 and −14%(range 0 to −26%) for V CO 2 .