Selection of cuffed endotracheal tube for children with congenital heart disease based on an ultrasound-based linear regression formula

It remains to be discovered whether a formula predicting the subglottic transverse diameter measured by ultrasound (SGD_formula) for the selection of an appropriate endotracheal tube (ETT) for children without congenital heart disease (CHD) is useful for children with CHD. A formula for predicting SGD was established after assessing 60 children ≤ 8 years without CHD and validated on 60 children with CHD. We selected the cuffed ETT size based on the SGD by ultrasound (SGD_ultra). Subsequently, the fit of the ETT cuff in 60 children with CHD was examined via air-leak test. The maximum allowed difference between the SGD_formula and the ETT size that fit was 0.2 mm. The agreement among and accuracy of SGD_ultra, SGD_formula, and the ETT used in children was analyzed. For children without CHD, we adopted a linear formula, given by SGD_formula (mm) = 0.4 × age + 5.3. For children with CHD, allometric formula was adopted, given by SGD_formula (mm) = 5.4 × age^0.18. A stronger agreement exists between SGD_ultra and ETT size compared to that between SGD_formula and ETT size. And the mean bias (SGD_formula-ETT size and SGD_ultra-ETT size) was 0.21 mm (95% confidence interval, − 0.59 to 1.01 mm) and 0.00 mm (− 0.79 to 0.84 mm). For the CHD group, the ultrasound-based method yielded a 78% success rate of ETT size choice, while the formula-based method permitted an appropriate ETT size in only 32% of subjects (P < 0.001). Our analysis showed that measuring the SGD_ultra was more accurate in predicting the correct OD of the ETT in children with CHD undergoing cardiovascular surgery, based on the correlation and agreement with ETT OD.