A high-pitched, sometimes whistling sound heard when a baby breathes in can be alarming for any parent. This noisy inhalation indicates that air is struggling to pass through a narrowed point in the respiratory tract. While parents often describe this sound as a wheeze, it typically requires immediate medical assessment. Understanding the precise nature and location of this breathing noise is the first step in determining the cause.
Distinguishing Wheezing from Inspiratory Stridor
Medically, wheezing refers to a high-pitched, musical sound primarily heard during exhalation. This classic wheeze originates from the lower airways, specifically the constricted bronchi and bronchioles within the lungs. The restricted airflow creates the characteristic expiratory sound.
The sound that occurs when a baby breathes in (inspiration) is called stridor. Stridor is a harsh, turbulent, high-pitched sound suggesting an obstruction or narrowing in the upper airway, including the larynx and trachea. This distinction is based on anatomy, as the upper airway is located outside the chest cavity. During inspiration, the pressure difference causes the extrathoracic airway to collapse slightly, worsening any existing narrowing and producing the inspiratory stridor sound.
A classic wheeze indicates a lower airway issue, such as asthma or bronchiolitis. Inspiratory stridor signals a partial blockage above the chest, usually at the level of the larynx or subglottis. The timing of the sound—inhalation, exhalation, or both—is a powerful clue used by clinicians to pinpoint the obstruction’s location. If the sound is heard only on inspiration, the issue is typically above the vocal cords.
Common Causes of Inspiratory Stridor in Infants
Causes of inspiratory stridor are categorized as either chronic (long-term) or acute (sudden onset).
Chronic Causes
The most frequent chronic cause is Laryngomalacia, a congenital condition where the cartilage supporting the structures above the vocal cords is too soft. These soft tissues collapse inward during inspiration, temporarily obstructing the airway and causing stridor. Laryngomalacia is often present from birth and accounts for up to 75% of chronic stridor cases in infancy. It usually resolves on its own by 12 to 24 months of age as the cartilage stiffens.
Subglottic stenosis, a narrowing of the airway just below the vocal cords, is another structural cause. It can be present from birth or acquired, often following prolonged intubation. While less common than Laryngomalacia, it can cause both inspiratory and expiratory stridor.
Acute Causes
A common cause of acute stridor is Croup, or laryngotracheobronchitis, typically caused by a viral infection. Croup results in swelling of the voice box and trachea, leading to a loud, harsh stridor often accompanied by a distinctive barking cough. This condition most frequently affects children between six months and three years of age and can worsen at night.
Other causes relate to structural or infectious issues within the throat and upper airway. Vocal cord paralysis, where one or both vocal cords do not move properly, is a serious congenital cause of stridor. In older infants and toddlers, a sudden onset of stridor with coughing or gagging suggests foreign body aspiration. This occurs when an inhaled object becomes lodged in the airway, creating a mechanical obstruction. A thorough medical evaluation is necessary to identify the specific origin of the stridor, as management depends entirely on the underlying cause.
Immediate Action and Emergency Red Flags
Parents must monitor for specific signs of respiratory distress that require immediate medical intervention. The most severe red flag is cyanosis, a bluish or grayish discoloration of the lips, tongue, or skin, signaling a dangerous lack of oxygen. Any sudden inability to cry or speak, or a change in alertness, such as extreme drowsiness or agitation, necessitates an emergency room visit.
Parents should observe the physical effort involved in breathing. Look for retractions, where the skin visibly sinks in around the ribs, collarbone, or neck with each inhale. Nasal flaring, where the nostrils widen during inspiration, is another sign the child is struggling to pull air into the lungs. Constant, loud stridor accompanied by drooling or difficulty swallowing suggests a severe obstruction.
While seeking professional help, certain home actions can temporarily ease stridor, especially if Croup is suspected. Exposure to moist air, such as sitting in a steamy bathroom, can sometimes reduce airway swelling. Cool air exposure, like opening a freezer door or taking the child outside in cold weather, may also help decrease inflammation.
The most important supportive measure is keeping the infant calm. Crying and agitation worsen stridor by increasing the force of air passing through the narrowed airway. Holding and comforting the baby helps conserve energy and prevents the breathing issue from escalating. These temporary measures are not a substitute for medical evaluation, and any child showing significant breathing difficulty must be taken to an emergency department.
Medical Diagnosis and Long-Term Management
Diagnosis begins with a detailed history, including the age of onset, the sound’s characteristics, and whether it is positional or associated with feeding. A healthcare provider performs a physical examination, listening to the chest and neck to confirm the timing and location of the noisy breathing. Initial tests may include a pulse oximetry reading to measure blood oxygen saturation and an X-ray of the neck and chest.
For a definitive diagnosis, especially for chronic stridor, the gold standard is flexible fiberoptic laryngoscopy. This procedure is performed by an ear, nose, and throat specialist. It involves passing a tiny, flexible camera through the nose to visualize the larynx and surrounding structures while the infant is awake. This allows the physician to directly observe airway dynamics, such as tissue collapse in Laryngomalacia or vocal cord immobility.
Long-term management is tailored to the specific diagnosis. For mild Laryngomalacia, the primary treatment is observation, as the condition resolves naturally in most children. If stridor is severe and causes difficulty feeding or poor weight gain, a surgical procedure called supraglottoplasty may be necessary to trim redundant tissue.
For infectious causes like Croup, treatment often involves a single dose of an oral steroid medication, such as dexamethasone, to reduce airway swelling. This is sometimes combined with humidified air or nebulized medications. For structural anomalies like subglottic stenosis, more invasive surgery may be required to widen the airway or relieve external compression. Many infants with stridor are also managed for associated conditions, such as gastroesophageal reflux disease, which can worsen airway inflammation. Long-term follow-up ensures the child’s breathing and overall development are monitored until the condition is fully resolved.