Influence of Chest Wall Distortion and Esophageal Catheter Position on Esophageal Manometry in Preterm Infants

摘要

The purpose of this study was to determine the effect of chest wall distortion on esophageal manometry by measuring simultaneous esophageal pressure changes at two sites in preterm infants. Fourteen infants were studied (mean ± SD: birth weight, 1340 ± 260 g; age, 8.5 ± 4 d). Esophageal pressure was measured through two water-filled catheters, one placed just above the cardia (Pes1) and the other at the level of the carina (Pes2). Chest wall distortion was measured by inductance plethysmography, and inspiratory and expiratory flow by pneumotachography. No significant differences were found between the peak to peak esophageal pressure changes measured through the lower and higher catheters during both airway occlusion (18.7 ± 4.4 versus 18.3 ± 2.6 cm H2O) and spontaneous breathing (9.4 ±1.8 versus 9.0 ± 1.8 cm H2O), although half of the infants had significant chest wall distortion. Mean pulmonary compliance and resistance measures calculated from the two pressures for individual infants showed small differences consistent with the difference between Pes1 and Pes2. For the whole group of 14 infants, however, these differences were not significant. The pressure changes from the lower and higher measuring sites for each breath were analyzed using linear regression. The weighted average of the mean slopes of the 14 infants was significantly different from 1.0 (mean ± SD: 0.92 ± 0.10, range: 0.75-1.10; p < 0.05). In some of the infants, the slopes for different breaths were not consistent, but varied from breath to breath. Neither this breath to breath variability in the relationship between Pesl and Pes2, nor the mean slopes were related to the degree of chest wall distortion. The results indicate that esophageal pressure measurements in preterm infants are not as dependent on the position of the catheter tip and the degree of chest wall distortion as previously suggested. A tip positioned between the cardia and the level of the carina transmits pleural pressure changes reliably.