Predicting endotracheal tube size by length in newborns

The objective of this study was to determine the relationship of length to endotracheal tube (ETT) size in newborns and to use this relationship to develop a tool for predicting ETT size. The study, a prospective derivation, and validation of a predictive model, took place in the neonatal intensive care units (NICUs) in two urban teaching hospitals. Subjects included: ETT derivation set - 39 intubated neonates admitted to the NICU; Validation set - 69 intubated newborns from the same NICU. Leak percentages were measured in intubated neonates where the actual ETT size did not correlate with the tape-determined ETT size. Interventions were length, weight, and leak measurements. A prototype tape was developed using the derivation set and published anthropometric studies. The accuracy of the tape was validated on a separate set of newborns. The average relative difference between tape-predicted weight and actual weight was 9.5% (confidence interval [CI] = 8.3-10.6%) and was evenly distributed throughout all the weight groups. The tape predicted actual ETT size in 96% of cases (CI 86.3-99.5%) and was correct within 1 tube size (1/2 mm) in 100% (CI 94.8-100%). The only error in prediction of ETT size was in underestimation. Length-based weight estimations were tested on 100 subjects and predicted actual weight within 20% in 94% of cases. We concluded that length is an accurate predictor of ETT size and weight in term and preterm newborns and may be useful in situations in which weights are unobtainable, such as emergency resuscitation.