Esophageal pressure in infants at elevated lung volumes and positive airway pressure

The measurement of esophageal pressure changes (delta Pes) under conditions of elevated lung volume or continuous positive airway pressure (CPAP) was investigated in a group of 17 infants by use of an esophageal balloon. Eleven of the infants were studied in a whole-body plethysmograph, and lung volume was increased by a volume injection technique. Reproducible measurements of lung volume in the plethysmograph showed that changes in mask pressure (delta Pm) were accurate during airway occlusion in 10 of the 11 infants. A progressive elevation of the ratio delta Pes/delta Pm during respiratory efforts against occlusion at lung volumes above the tidal range was observed in 8 of the 11 infants. In only one of these infants could the error have been in delta Pm measurement. Of seven infants (including one common to both studies) studied under CPAP, six also showed this effect, which occurred predominantly in very young or preterm infants. Changes in esophageal pressure in infancy, measured at high lung volumes or pressures, may not be representative of mean pleural pressure changes.