Lower esophageal sphincter position in premature infants cannot be correctly estimated with current formulas

Objectives: Strobel's formula (Esophageal length = 5 + 0.252 x Height) is f requently used as a guide for determining the distance from the nares to th e lower esophageal sphincter (LES) in term infants. The aim of this study w as to examine this relationship in premature infants. Study design: The distance from nares to LES was manometrically determined in 156 premature infants (26-40 weeks' postmenstrual age; body weights of 6 10-3050 g). The ability of body weight, height (body length), head circumfe rence, and postmenstrual age to predict the manometrically determined LES p osition wa's evaluated with linear and non-linear regression analyses. Results: Body weight and body length were the most predictive of distance f rom nares to LES (r(2) = 0.848 and 0.802, respectively). These relationship s were non-linear and, in the case of body length, deviated substantially f rom Strobel's model. Conclusions: In premature neonates, a different formula is needed for predi ction of the distance between nares and LES than that applied to term infan ts and children.