Introduction
Endotracheal tubes created a seal between the endotracheal tube and the trachea, preventing aspiration of fluids and pathogens from the pharynx to the lungs and ventilation leaks. Consensus suggests that cuff pressure in endotracheal tubes should range from 20 to 30 cmH2O[1], However, in clinical practice cuff pressures > 30 cmH2O may be required to create a seal in the trachea[2], The possible reason is that cuff size may be unsuitable.
In terms of oral endotracheal tube, the global guidelines for endotracheal tube lack clear guidance or consensus on the selection of endotracheal tube model[3]. Foreign studies suggest that adult female patients choose (ID) 7.0 to (ID) 8.0mm cannula, and male patients choose (ID) 8mm and (ID) 8.5mm; In children, traditionally, the formula based on demographic data is used to predict the appropriate size of endotracheal tube, and the traditional formula based on age, such as Cole [4]formula of endotracheal tube without air bag (inner diameter [ID] [mm] = [age at 4 years] + 4.0); For example, Motoyama formula (inner diameter [mm] = [age in the fourth year] + 3.5) for endotracheal tube with air bag has been widely used in children’s ETT selection[5]. The above shows that there is no consensus on the choice of endotracheal tube for patients, and there is an urgent need for an accurate and feasible method.