VOLUME-CONTROLLED VENTILATION IS MADE POSSIBLE IN INFANTS BY USING COMPLIANT BREATHING CIRCUITS WITH LARGE COMPRESSION VOLUME

We studied the weight dependency of set rid al volume (VTset) during v olume-controlled ventilation of 80 infants (ASA physical status I-IV, 0.7-20 kg), including prematures, neonates, and exprematures, who Mi r e anesthetized for major and minor surgery, including abdominal, thora cic, and neurosurgical procedures. After neuromuscular blockade and en dotracheal intubation, infant's lungs were ventilated with an Ohmeda 7 800 volume-limited ventilator and either a pediatric or adult circle b reathing system (PC or AC) or a Bain circuit (Ba) and a pediatric- or adult-sized bellows (PB or AB). Except for larger and older infants in the ACAB group, body weight, age, peak inspiratory pressure (PIP), ET co(2), and Spo(2) did not differ among groups. Compression volume loss was large in the five circuits tested. We found that VTset/kg varied with weight in a curvilinear relationship where y represents volume ad ded and x represents PIP (y = 175.02x(-0.87); r(2) = 0.87), whereby VT set is similar to 150-200 mL/kg for a 1-kg infant and similar to 25 mL /kg for infants greater than or equal to 10 kg. Ventilation was adequa te in each infant, except for one with extremely poor pulmonary compli ance. We conclude that large compression volumes associated with compl iant breathing systems make possible the use of volume-controlled vent ilators in small infants.