Validity of esophageal pressure measurements with positive end‐expiratory pressure in preterm infants

Previous research suggested that esophageal pressure changes (ΔP es ) may not reflect pleural pressure changes (ΔP pl ) in the presence of positive end‐expiratory pressure (PEEP), making assessments of dynamic lung mechanics invalid in these circumstances. To test this hypothesis, we measured ΔP es using a water‐filled catheter in 18 preterm infants with lung disease (9 intubated), and adjusted the catheter position to achieve a valid occlusion test. End‐expiratory occlusions were then carried out at PEEP (cm H 2 O) of 0, 4, and 8, and plots of ΔP es against ΔP ao during airway occlusion were examined to derive the ratio ΔP es /ΔP ao and the r value (as a measure of linearity). There was no significant change in ΔP es /ΔP ao , which remained close to 1.0 as PEEP was increased from 0 to 8 cm H 2 O, and r also remained close to unity, indicating no appreciable hysteresis or alinearity of the plots. Our results show that ΔP es , when measured with an appropriately placed water‐filled catheter, continues to reflect ΔP pl accurately when lung volume is raised by applying PEEP up to 8 cm H 2 O. Pediatr Pulmonol. 2003; 36:216–222. © 2003 Wiley‐Liss, Inc.