THE DIAGNOSIS in this case was initially laryngotracheobronchitis and subsequently laryngeal stridor, with episodes of varying degree between the two in the intervening year. What applies to laryngotracheobronchitis applies to the less severe respiratory disturbance of laryngeal stridor in young children.
Acute infective laryngotracheobronchitis is an acute inflammation of the upper and lower air passages, with certain clinical findings.1 It occurs endemically every winter with an incidence corresponding to the prevalence of acute infection of the upper respiratory tract. The chief predisposing cause is age, for anatomic reasons. Loose areolar tissue is abundant in the larynx during the first few years of life, and the lumen of all the air passages below the larynx is small. Although a small child needs only a small tube under "normal" conditions, the small tube, as a small pipe in plumbing, is more easily stopped up than a large one. Thus 2 mm.
SIMMONS FH. PREVENTIVE TREATMENT OF LARYNGOTRACHEOBRONCHITIS IN CHILD OF TWENTY-TWO MONTHS. AMA Arch Otolaryngol. 1952;56(2):209–212. doi:10.1001/archotol.1952.00710020228014