Evaluating Endotracheal Tube Depth in Infants Weighing Less Than 1 Kilogram

Endotracheal tube (ETT) depth in premature infants is of critical importance because potentially life-threatening adverse events can occur if the tube is malpositioned. Analysis of current data indicates that the accuracy of current resuscitation guidelines for infants <1 kg is poor. We hypothesized that a weight-based formula that is used clinically in our institution would accurately predict appropriate ETT placement in infants weighing < 1 kg.

The medical records, from July 2013 to November 2016, of all infants < 1 kg who were intubated were retrospectively reviewed and included. The 2 formulas utilized were the Duke formulas 5.5 cm + 1 cm/kg for infants 500-999 g or 5.0 + 1 cm/kg for infants <500 g. The appropriate ETT position was defined as the tip of the ETT below the thoracic inlet and above the carina, at approximately thoracic vertebrae 2 or 3 on an initial chest radiograph. The formula was defined as being accurate if the documented ETT depth was within 0.2 cm of the predicted depth. Post hoc analysis of current resuscitation guidelines (6 cm plus the weight of the infant in kg) was performed after the Duke formula performed worse than expected.

A total of 131 subjects (mean ± gestational age, 26 ± 1.8 wk; mean ± weight, 729 ± 140 g) were included. The documented depth was accurately predicted by the Duke formula for 47% of the subjects, with 69% of the ETTs appropriately positioned as seen on a chest radiograph. Sensitivity was 46.6%, specificity was 53.6%, positive predictive value was 68.8% and negative predictive value was 31.4% for the Duke formula. Post hoc analysis current resuscitation guidelines found that the documented depth was accurately predicted for 23% infants, with 70% of these appropriately positioned ETTs.

Our weight-based, institutional formula had a low sensitivity for predicting proper ETT depth. Weight-based formulas may have clinical utility; however, analysis of current data did not support use in infants < 1 kg. Rapid radiologic assessment of ETT placement is required for this patient population.