Stridor is a medical term for a specific kind of abnormal breathing sound that can cause alarm, particularly when it occurs while sleeping. This high-pitched noise is not a condition itself but rather a symptom indicating turbulent airflow through a narrowed upper airway. Because the air passage of a child is significantly smaller than that of an adult, even a minor obstruction can lead to pronounced noisy breathing. Understanding the nature of this sound and its potential origins is important for parents and caregivers to determine when observation is appropriate and when immediate medical intervention is necessary.
What Stridor Sounds Like
Stridor is acoustically distinct from common congested breathing or snoring. It is often described as a harsh, musical, or squeaking sound, produced when air is forced through a partially blocked section of the larynx or trachea. This high-pitched quality results from the rapid vibration of tissue as the air attempts to pass through the constricted space. Stridor differs from stertor, which is a lower-pitched, snoring-like sound caused by obstruction higher up, usually in the nose or throat.
The timing of the sound offers important clues about the location of the narrowing. Inspiratory stridor, which occurs when breathing in, is the most common type and usually suggests an obstruction above the vocal cords (extratracheal region). Expiratory stridor, heard when breathing out, typically points to a narrowing lower down in the windpipe within the chest cavity. If the noise is heard during both inhalation and exhalation (biphasic stridor), it often suggests a fixed obstruction at the level of the vocal cords or just below them, in the subglottic area.
Underlying Causes of Noisy Breathing
The causes of stridor are varied, ranging from temporary infections to congenital structural anomalies, and they often become more noticeable when a child is lying flat or sleeping. Laryngomalacia represents the most frequent congenital cause of stridor in infants, accounting for up to 75% of all cases. This condition involves a softness or floppiness of the laryngeal cartilage above the vocal cords, causing the tissue to collapse into the airway during inspiration. The stridor is typically inspiratory and often worsens when the infant is supine or crying, but it usually improves as the child grows, often resolving by 18 months of age.
Conversely, Croup (laryngotracheobronchitis) is the most common infectious cause of acute stridor, primarily affecting children between six months and two years old. This viral infection leads to swelling of the airway lining, which produces the characteristic “barking” cough that frequently accompanies the inspiratory stridor. The symptoms of Croup are often worse at night.
Other structural issues can also lead to stridor, such as tracheomalacia, where the walls of the trachea are unusually weak, or subglottic stenosis, a narrowing of the airway just below the vocal cords. A sudden onset of stridor, especially in a toddler, should immediately raise suspicion of foreign body aspiration, where an object becomes lodged in the airway.
When to Seek Immediate Medical Attention
The presence of stridor while sleeping is not automatically an emergency, but it requires prompt evaluation if certain signs of severe respiratory distress accompany the sound. The most concerning indicator is an increased effort to breathe, which can manifest as retractions. This occurs when the skin visibly pulls inward between the ribs, above the collarbone, or at the neck with each breath, signifying the child is struggling to move air past the obstruction.
Other serious signs include:
- Cyanosis, a bluish or grayish tint around the lips, tongue, or face, indicating a dangerous drop in blood oxygen levels.
- Flaring nostrils, a compensatory mechanism to widen the airway and increase air intake.
- Lethargy or a noticeable change in mental status.
- Inability to speak or cry with a normal voice.
- Excessive drooling, indicating the obstruction may be quickly progressing.
Any stridor that occurs even when the child is at rest, rather than just during crying or activity, is a red flag that warrants immediate medical attention. Parents should call emergency services if they observe these signs of distress or if the child has pauses in breathing. For mild stridor associated with a common cold, simple home measures like exposure to cool night air or steam can sometimes help reduce swelling, but these should not delay seeking professional help if the breathing difficulty is severe or worsening.