Page "Tracheal intubation" Paragraph 61

Because the airway of a child is narrow, a small amount of glottic or tracheal swelling can produce critical obstruction.

Inserting a tube that is too large relative to the diameter of the trachea can cause swelling.

Conversely, inserting a tube that is too small can result in inability to achieve effective positive pressure ventilation due to retrograde escape of gas through the glottis and out the mouth and nose ( often referred to as a " leak " around the tube ).

An excessive leak can usually be corrected by inserting a larger tube or a cuffed tube.