Down syndrome: analysis of airway size and a guide for appropriate intubation
OBJECTIVES/HYPOTHESIS: The purpose of this study is to prospectively evaluate the airway size of children with Down syndrome (DS). Previous studies have observed an increase in postintubation stridor in children with DS. Anesthetic literature suggests using a smaller endotracheal tube in children with DS, but more specific recommendations are not offered. With this study, recommendations are presented for the appropriate endotracheal tube size to use in children with DS undergoing intubation.
STUDY DESIGN: A prospective, nonrandomized study was performed on a cohort of 42 children with DS and 32 control subjects. Sizing of the airway was assessed through measurement of an air leak around the endotracheal tube at intubation. The size of the airway was also evaluated through measurements of the tracheal diameter at the "tracheotomy point" on magnetic resonance imagine (MRI) studies of the head and neck which were performed on a group of children with DS. These were compared with normative values of the tracheal diameter in children.
METHODS: The proper size of endotracheal tube in a population of children with DS and in a group of normal controls was determined. The "proper size" of an endotracheal tube was defined as that size of tube which allowed an audible air leak around the tube between 10 and 30 cm of H2O pressure. Anesthetic technique was controlled and identical for all study subjects. Participants had no previous history of airway compromise, stridor, or previous intubation. Weight and age were recorded and evaluated for their influence on the results. A retrospective evaluation was made of MRI studies of the neck that were performed on children with DS. Using measurement techniques described by Reed et al., the tracheal diameters at the "tracheostomy point" were compared with normative values for children. Measurements were both obtained by the author and confirmed by a pediatric radiologist.
RESULTS: Using this prescribed method to determine the proper size of endotracheal tube, the control group used endotracheal tubes that were predicted from established anesthesia charts and formulas. However, children with DS required endotracheal tubes at least two sizes smaller. Age was found to be a more reliable factor in predicting the endotracheal tube size. A table of endotracheal tube sizes for intubation in children with DS is presented. Evaluation of the tracheal diameter at the tracheotomy point revealed that children with DS have a smaller trachea when compared with control children. It is not only the subglottis that is smaller; the tracheal diameter as well must be assumed to be of a smaller diameter in children with DS.
CONCLUSIONS: Children with DS have smaller airways than other children. This is because of an overall decrease in the diameter of the tracheal lumens. Initial intubation of a child with DS should be performed with an endotracheal tube at least two sizes smaller than would be used in a child of the same age without DS, to avert potential trauma to the airway.