Relationship of laryngeal dimensions to body size and gestational age in premature neonates and small infants.

The larynges of 27 infants weighing between 250 gm and 9160 gm were studied. Twenty-two neonates were from 24 to 40 weeks' gestational age. Five subjects died more than 6 weeks post partum but were included because of their small size. Relationships of larynx size to the standard clinical measurements of crown-heel length, crown-rump length, head circumference, and gestational age were developed. Cartilage size relationships to these measurements were found to be linear. Glottic length related linearly to crown-rump length but related in a curvilinear way to crown-heel length, head circumference, and gestational age. A guide to the choice of endotracheal tube sizes for small infants is suggested.