Cuff bulk of tracheal tubes in adolescence

Purpose: To investigate cuff types for potential use in late childhood and early adolescence for appropriate fit. Method: Formulae suggest the use of a tracheal tube having a 6.5 mm internal diameter at ages 8 to IO years, so a model system was used to test the passage of cuffed and uncuffed tracheal tubes of 6.5 mm internal diameter through calibrated holes 8.1-16.6 mm diameter, in plastic plates. Results: Uncuffed tracheal tubes passed through 9.0 mm diameter holes. ''High pressure'' cuffed tubes passed through 10.5 to 11.3 mm holes. ''Low pressure'' cuffed tubes passed through 12.3 to 16.4 mm. Conclusion: Patients aged 8 to 10 yr have a limiting internal diameter at the cricoid of 8 to IO mm. Their unstretched tracheal diameter below the cricoid is only about II mm. The actual outside diameters of ''low pressure'' cuffs chosen by commonly used formulae considerably exceed the limiting diameters of eight to ten year old patients, even considering recommended compensation factors. Analysis of background data indicates that these problems are especially aggravated at this age by non-linear growth of the cricoid.