Influence of chest wall distortion on esophageal pressure

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Abstract
The caudocephalad profile of esophageal pressure swings was studied in 10 preterm and 5 full-term [human] infants, and the effect of chest wall distortion on esophageal pressure swings was analyzed in 12 preterm infants. Esophageal pressure was measured with a fluid-filled catheter, tidal volume with a pneumotachograph, mouth pressure with a face mask and pressure transducer, and rib cage and abdominal motion with magnetometers. In preterm infants the profile of esophageal pressure swings fell very steeply in the caudocephalad direction. In full-term infants it was flat during quiet sleep and steep during rapid-eye-movement sleep. When breaths, standardized for pleural pressure, were compared between a period with maximal and a period with minimal chest wall distortion, esophageal pressure swings for both spontaneous and occluded breaths were higher in the former period. The compliant preterm rib cage results in an uneven distribution of pleural pressure. This distribution varies with changes in chest wall distortion. Esophageal pressure measurements are an unreliable estimate of mean pleural pressure in the preterm infant and can be unreliable in the term infant.