Estridor

iAssessment of stridor in children

Authors
Diana R Quintero, MD
Khoulood Fakhoury, MD Section Editor
Gregory Redding, MD Deputy Editor
Alison G Hoppin, MD

Last literature review version 19.1: January 2011 | This topic last updated: May 12, 2010 (More)

INTRODUCTION — An examination of the etymology of the English word stridor indicates that the noun is derived from the Latinverb stridere, meaning to make a harsh noise or shrill sound, as to creak. Appropriately, one of the primary uses of the word stridor, today, is to signify a high-pitched, musical sound made when breathing, which is usually superimposed on the normal breath sounds. Stridor is caused by the oscillation of a narrowed airway, and its presence suggests significant obstruction of the large airways. Theacoustics of stridor may be explained as a result of Bernoulli's Principle, which states that as the speed of a moving fluid increases, the pressure within the fluid decreases. In an application in which airflow is forced through a narrowed tube, a local area of low pressure creates a vacuum effect distal to the narrowing. The focal area of low pressure distal to a narrowed airway causes theairway walls to collapse and vibrate, generating the squeak characteristic of stridor [1-5].

A commonly encountered presenting symptom in the pediatric population, stridor is an important physical finding that requires prompt evaluation. The pathophysiology, differential diagnosis and clinical management of stridor will be reviewed here. Other common presenting respiratory symptoms, includingwheeze and cough, are presented separately, as is the emergent evaluation and treatment of acute upper airway obstruction. (See "Approach to wheezing in children" and "Wheezing illnesses other than asthma in children" and "Approach to chronic cough in children" and "Emergent evaluation of acute upper airway obstruction in children".)

ANATOMY AND ETIOLOGY — Anatomically, the upper airway can bedivided into two regions, extrathoracic and intrathoracic:

Extrathoracic — This region includes airways above the thoracic inlet, which, in turn, can be subdivided into two anatomic areas:

Supraglottic area — This area includes the nasopharynx, epiglottis, larynx, aryepiglottic folds, and false vocal cords. The walls supporting this region are made of soft tissue and muscles, and lackcartilaginous support. Therefore, airway collapse and obstruction can occur easily and progress rapidly in this area.

Glottic and subglottic area — This portion of the airway extends from the vocal cords to the extrathoracic segment of the trachea, just before it enters the thoracic cavity. The glottic area has some cartilaginous support (ie, cricoid cartilage and incomplete tracheal rings), whichmakes it less vulnerable to collapse than the supraglottic area. The subglottis, surrounded by the cricoid cartilage, is the narrowest part of the trachea, with a diameter of 5 to 7 mm at birth. A narrowing by 1 mm in the subglottic area will decrease the cross-sectional area by 75 percent and increase airway resistance 16 fold [6].

Classic diseases that cause acute obstruction at extrathoraciclevel include laryngotracheitis (croup), epiglottitis, retropharyngeal abscess, and diphtheria [1]. (See "Clinical features, evaluation, and diagnosis of croup" and "Epiglottitis (supraglottitis): Clinical features and diagnosis" and "Retropharyngeal infections in children" and "Epidemiology and clinical features of diphtheria".)

Laryngomalacia is the most common cause of chronic extrathoracicairway obstruction in infants [6]. However, other abnormalities can also result in obstruction at this level, including tracheomalacia, vocal cord paralysis, and subglottic stenosis [1]. (See "Congenital anomalies of the larynx", section on 'Laryngomalacia' and "Congenital anomalies of the larynx", section on 'Atresia and stenosis' and "Congenital anomalies of the intrathoracic airways and...