Volume-controlled ventilation is made possible in infants by using compliant breathing circuits with large compression volume.

We studied the weight dependency of set tidal volume (VTset) during volume-controlled ventilation of 80 infants (ASA physical status I-IV, 0.7-20 kg), including prematures, neonates, and exprematures, who were anesthetized for major and minor surgery, including abdominal, thoracic, and neurosurgical procedures. After neuromuscular blockade and endotracheal intubation, infant's lungs were ventilated with an Ohmeda 7800 volume-limited ventilator and either a pediatric or adult circle breathing 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), ETCO2, and SPO2 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 added and x represents PIP (y = 175.02x-0.87; r2 - 0.87), whereby VTset is approximately 150-200 mL/kg for a 1-kg infant and approximately 25 mL/kg for infants > or = 10 kg. Ventilation was adequate in each infant, except for one with extremely poor pulmonary compliance. We conclude that large compression volumes associated with compliant breathing systems make possible the use of volume-controlled ventilators in small infants.