Oesophageal pressure measurement in rabbits and human infants using an air-filled balloon system

In ventilated anaesthetized rabbits the relationship between the oesophageal pressure and the intrapleural pressure, measured with an air-filled balloon system, was studied. A balloon 15 mm long and 3 mm diameter detected 95% of the measured intrapleural pressure, provided the balloon was positioned accurately. In babies undergoing IPPV, the best balloon position was in the lower third of the oesophagus. When synchronous spontaneous respiration occurred in the course of IPPV the mean of intrapleural pressure remained negative in spite of positive ventilating pressures in the range 30-45 cm H2O.