scope:

This part of ISO 5361 is one of a series of International Standards dealing with anaesthetic equipment and medical breathing machines; it makes provision for tracheal tubes of the Cole-type, i.e. the type with a small patient end for use with infants. The narrowest part of the infant airway is the nondistensible cricoid cartilage ring which is the main controlling factor during tracheal intubation. Consequently, the size of the tracheal portion is the limiting factor which determines the choice of size of tube to be used.