What is Stridor?
Stridor is a distinctive breathing sound, characterized by its high-pitched, harsh, or squeaky quality. This sound typically arises from turbulent airflow as air attempts to pass through a narrowed upper airway. It differs significantly from snoring, which is a softer, rumbling sound produced by vibrations in the soft palate and uvula, usually originating lower in the airway. Stridor is also distinct from wheezing, a musical, whistling sound that generally indicates narrowing in the lower airways, such as the bronchioles.
The mechanism behind stridor involves an obstruction or narrowing anywhere from the pharynx down to the trachea. This constriction forces air through a smaller opening, creating the characteristic harsh sound. The location of the obstruction often dictates when the sound is heard during the breathing cycle.
Stridor can manifest in different forms depending on the phase of respiration. Inspiratory stridor, heard primarily during inhalation, often suggests an obstruction located above the vocal cords, perhaps in the pharynx or supraglottic region. Expiratory stridor, occurring during exhalation, usually points to a blockage in the lower trachea or main bronchi. When stridor is heard during both inhalation and exhalation, known as biphasic stridor, it typically indicates a fixed obstruction at the level of the vocal cords or just below them in the subglottic area.
Why Stridor Occurs During Sleep
Stridor often becomes more noticeable during sleep due to several physiological changes. During sleep, the muscles supporting the upper airway naturally relax. This relaxation can exacerbate an existing airway narrowing, making a partial obstruction more significant. The supine sleeping position can also contribute, as gravity may cause tissues to fall backward, further compressing the airway.
Additionally, mucus and secretions can accumulate in the airway overnight, potentially adding to the obstruction that causes stridor. The reduced conscious control over breathing during sleep means that minor airway resistances are not actively compensated for, allowing the characteristic sound to emerge. These factors combine to make sleep a common time for stridor to be observed.
In children, several conditions commonly lead to stridor during sleep:
Laryngomalacia: A frequent cause in infants, where the cartilage of the larynx is unusually soft and collapses inward during inspiration, producing inspiratory stridor. This condition often resolves as the child matures and the laryngeal cartilage stiffens.
Croup: A viral infection causing swelling in the larynx and trachea, is another common culprit, resulting in a characteristic “barking” cough and inspiratory stridor that often worsens at night.
Foreign body aspiration: Where an object becomes lodged in the airway, can cause sudden onset stridor, which may persist or worsen during sleep.
Epiglottitis: A bacterial infection causing severe swelling of the epiglottis, is a serious medical situation that can lead to rapid airway obstruction and stridor.
Subglottic stenosis: A narrowing of the airway just below the vocal cords, can be congenital or acquired and consistently causes stridor, often more noticeable when the child is relaxed in sleep.
Stridor in adults during sleep is less common but can arise from various causes. Vocal cord dysfunction involves the paradoxical closure of the vocal cords during breathing, which can lead to stridor. Tumors or growths in the larynx or trachea can progressively narrow the airway, causing stridor. An enlarged thyroid gland, known as a goiter, can compress the trachea and produce stridor. Stridor may also occur as a complication following neck or airway surgeries due to swelling or scar tissue formation.
Recognizing Warning Signs
Observing stridor, especially during sleep, necessitates an understanding of accompanying signs that indicate a need for immediate medical attention. Certain red flags suggest that the airway obstruction is significant and requires urgent evaluation. These include visible difficulty breathing, such as retractions where the skin pulls in between the ribs, above the collarbone, or at the neck with each breath. Nasal flaring, where the nostrils widen during breathing, and unusually rapid breathing are also critical indicators.
A bluish discoloration of the lips, tongue, or skin, medically termed cyanosis, signals a severe lack of oxygen and constitutes a medical emergency. Drooling or difficulty swallowing, particularly if accompanied by a muffled voice or inability to speak, can point to a serious obstruction. Changes in a person’s state, such as becoming unusually lethargic, extremely irritable, or less responsive, are also concerning.
In some severe cases, a sudden absence of the stridor sound after it has been present can be an alarming sign. This paradoxical silence might indicate a complete airway obstruction, which is a life-threatening emergency. Any of these warning signs warrant immediate emergency medical care to ensure the airway remains open and oxygenation is maintained.
Medical Evaluation and Treatment
A medical evaluation for stridor typically begins with a comprehensive medical history, focusing on the characteristics of the sound, its onset, and any associated symptoms. A thorough physical examination assesses breathing patterns, the condition of the airway, and overall health.
Further diagnostic methods may include:
Imaging studies, such as neck X-rays or CT scans, can provide detailed views of the airway structures to identify the location and nature of any narrowing or obstruction.
Endoscopic procedures, including laryngoscopy to visualize the larynx or bronchoscopy to examine the lower airways, offer direct visualization of the airway and help pinpoint the exact cause of the stridor.
Blood tests may be conducted to identify underlying infections or inflammatory processes.
In some instances, a sleep study might be recommended to evaluate airway dynamics during sleep and assess the severity of obstruction.
Treatment for stridor is highly individualized and primarily focuses on addressing the underlying cause.
For conditions like croup, treatment often involves humidified air, corticosteroids to reduce airway swelling, and sometimes nebulized epinephrine for more severe cases.
Mild laryngomalacia is frequently managed with observation, as it often resolves spontaneously as an infant grows.
Severe structural issues, such as significant subglottic stenosis or the presence of tumors, may necessitate surgical intervention to correct the narrowing or remove the growth.
If a foreign body is aspirated, it requires endoscopic removal to clear the airway.
Bacterial infections, such as epiglottitis, are treated with antibiotics, and immediate airway management, such as intubation, may be required to secure breathing.