Prediction of endotracheal tube size for pediatric patients from the length of the middle finger in comparison with standard age-based formula in South Indian population

Background: Determining the appropriate size of an endotracheal tube (ETT) in infants and children remains a challenge for anesthesiologists. We conducted this study to assess the accuracy of middle finger length (MFL) in predicting the appropriate ETT size for pediatric patients in comparison with the age-based estimation and derive a formula based on MFL for the estimation of ETT size. Materials and Methods: In the study, South Indian children 1-10 years of age, requiring general anesthesia were intubated by consultant anesthesiologists based on their discretion with an appropriately sized ETT. Subsequently, the MFL of the children was measured and tracheal tube size calculated from the age-based formula was also noted. The actual size of the ETT inserted was compared with the MFL and age-based formula using Pearson's correlation. Results: In children between 1 and 10 years of age, the age-based formulae (ABF) was found to correlate with ETT estimated with the correlation coefficient (r = 0.885; P < 0.001) and MFL (r = 0.783 and P < 0.001). ABF showed a stronger correlation with the ETT inserted compared to the MFL, nevertheless, we were able to arrive at a formula to predict tracheal tube size based on MFL: ETT ID (mm) =1.1+ (0.7 × MFL [cm]). Conclusion: Although age-based Cole's and Motoyama's formulae are better predictors of pediatric ETT size, MFL can still be used to predict the tube size in cases when age and weight are unknown.