Comparison of tracheal tube cuff diameters with internal transverse diameters of the trachea in children

BACKGROUND: In this study, we evaluated the ratio of the cuff diameters of the Microcuff paediatric tracheal tube (Microcuff PET, Weinheim, Germany) to fluoroscopically measured internal transverse tracheal diameters in children from birth to adolescence. METHODS: With Institutional Ethics Committee approval and parental consent, we measured the internal transverse tracheal diameters from fluoroscopy images in children undergoing cardiac catheterization requiring general anaesthesia with oro-tracheal intubation. Minimal tracheal sealing pressures were assessed at standardized respirator settings. Internal transverse tracheal diameters were compared with cuff diameters at 20 cmH2O cuff pressure. Linear regression analysis was employed to assess the correlation of tracheal diameters with age, height and weight, and to assess the correlation of the cuff/tracheal diameter ratio with sealing pressures. For all tests, P < 0.05 was considered to be statistically significant. RESULTS: One hundred and forty-five patients were studied (62 girls; 83 boys). Transverse tracheal diameters correlated well with age (r = 0.890; P < 0.0001), height (r = 0.900; P < 0.0001) and weight (r = 0.882; P < 0.0001). Tracheal sealing pressures ranged from 4 to 18 cmH2O. The ratio of the tracheal tube cuff diameter to the internal transverse tracheal diameter ranged from 1.06 in tubes with internal diameters of 6.0 and 4.5 mm to 2.01 in a tube with an internal diameter of 3.5 mm (median, 1.43), and did not correlate with tracheal sealing pressures (r = 0.021, P = 0.7999). CONCLUSIONS: The residual diameters of the Microcuff paediatric tracheal tube cuffs were sufficient to cover the measured internal transverse tracheal diameters of children from birth to adolescence. This allowed the internal tracheal mucosal surface to be draped and the trachea to be sealed at very low cuff pressures.