- Author: Timothy D Murphy, MD; Chief Editor: Michael R Bye, MD more...
Stridor is a clinical sign characterized by monophonic, audible breath sounds (noisy breathing) that usually originates from the extrathoracic airways. The presence of stridor indicates a partial obstruction of the upper airways, glottis, or trachea. The pitch of the stridor is determined by the degree of airway obstruction and the velocity of the airflow; the loudness and tone of the sound also varies by the specific cause. Congenital stridor presents at birth or within the first few weeks (4-6) of life.
See the video of breath sound assessment, below.Breath sound assessment. Video courtesy of Therese Canares, MD, and Jonathan Valente, MD, Rhode Island Hospital, Brown University.
Stridor results from partial obstruction of an airway with turbulent flow characteristics. Such respiratory tract areas are the upper airway, glottis, and trachea. The obstruction can be fixed or variable. Variable extrathoracic obstructions are primarily associated with inspiratory stridor. This is because, during inspiration, extrathoracic intraluminal airway pressure is negative relative to atmospheric pressure, leading to collapse of supraglottic structures. During expiration, intrathoracic pressure is positive and tends to collapse the airway. Thus, stridor caused by intrathoracic obstructions tends to be more prominent upon expiration. Stridor heard during both phases of respiration is usually due to either a fixed airway obstruction or to 2 areas of obstruction (ie, intrathoracic and extrathoracic).
Congenital stridor is rarely life-threatening. Immediately life-threatening obstruction from congenital lesions such as severe micrognathia are apparent at birth, and are treated with emergent tracheotomy. Bilateral vocal cord paralysis and subglottic hemangioma may present as causes of congenital stridor that are life-threatening. Significant airway obstruction can lead to respiratory distress and failure to thrive, secondary to the increased work of breathing.
Congenital stridor is present either at birth or shortly afterward.
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