The 'best fit' endotracheal tube in children --comparison of four formulae.

BACKGROUND: Uncuffed endotracheal tubes are still being recommended by most pediatric of anesthetists at our Institutes. Different algorithms and formulae have been proposed to choose the best-fitting size of the tracheal tube. The most widely accepted is related to the age of the child [inner diameter [ID] in mm = (age in yr/4) + 4; the second is a body, length-related formula (ID in mm = 2 + height in cm/30); the third, a multivariate formula (ID in mm = 2.44 + age in yr x 0.1 + height in cm x 0.02 + weight in kg x 0.016]5; the fourth, the width of the 5th fingernail is used for ID prediction of the ETT (ID in mm = maximum width of the 5th fingernail). The primary endpoint of this prospective study was to compare the size of the 'best fit' tracheal tube with the size predicted using each of the above mentioned formulae.

PATIENTS AND METHODS: With Institutional Ethics Committee approval and parental consent, 27 boys, 23 girls, ASA I-III, 2-10 years, scheduled for different surgical procedures requiring general anesthesia and endotracheal intubation, were enrolled in the study. The size of 'best fit' endotracheal tubes in those children were compared. The internal diameter considered the 'best fit' by the attending pediatric anesthesiologist was compared to age-based, length-based, multivariate-based and 5th fingernail width-based formulae. For all tests, P < 0.05 was considered to be statistically significant.

RESULTS: The mean (SD) IDs for the 'best fit', age-based, length-based, multivariate and 5th fingernail techniques were 5.31 (0.691), 5.54 (0.622), 5.82 (0.572), 5.71 (0.67) and 5.43 (0.821) mm, respectively.

CONCLUSIONS: The age-based and 5th fingernail width-based predictions of ETT size are more accurate than length-based and multivariate-based formulae in terms of mean value and case matching.