Pulmonary compliance in sick low birthweight infants. How reliable is the measurement of oesophageal pressure?

Measurements of dynamic lung compliance (Cdyn) were made on 42 occasions in a group of 15 intubated very low birthweight infants with respiratory distress syndrome, using an oesophageal balloon and pneumotachograph system. Values of Cdyn were compared with those of total respiratory system compliance (Crs) using an occlusion technique. Ten very low birthweight infants with no respiratory disease were similarly studied while breathing through a facemask. The occlusion tests for oesophageal balloon assessment were unsatisfactory in 14 of 15 intubated infants, but in only 3 of the 10 normal infants. Values of Cdyn were poorly reproducible and correlated poorly with Crs. We conclude that in sick intubated preterm infants oesophageal pressure (and hence Cdyn) cannot be reliably measured, but that Crs may be a useful parameter of lung stiffness.