Wheezing is a high-pitched, whistling sound resulting from turbulent airflow moving through a narrowed or partially obstructed airway. Infants and young children have smaller, softer airways than adults, making them susceptible to noisy breathing sounds even with minor swelling or mucus. Understanding the exact nature of the sound is the first step in determining the problem’s location and urgency.
Understanding the Sound: Wheezing Versus Stridor
The sound described as “wheezing on inhalation” is often stridor, not a true wheeze. Wheezing typically occurs during exhalation, indicating an obstruction in the lower airways, such as the bronchi or bronchioles. True wheezing is caused by the collapse of these small airways during expiration when resistance is increased.
Stridor, in contrast, is a harsh, high-pitched noise usually heard during inhalation. This sound originates higher up in the respiratory tract, specifically in the upper airway, which includes the larynx (voice box) or trachea (windpipe). The distinction is based on the location of the blockage: stridor points to an issue outside the chest cavity, while wheezing signals a problem inside the lungs. Inspiratory stridor occurs because the negative pressure created during inhalation causes the already narrowed upper airway to collapse further, generating the turbulent sound.
Identifying the Underlying Causes
The causes of noisy breathing are grouped by the sound they produce, which helps narrow down the affected area.
Lower Airway Causes (Wheezing)
Conditions causing true wheezing involve the lower airways and are often triggered by inflammation and mucus production. The most common cause of wheezing in infants is bronchiolitis, a viral infection usually caused by Respiratory Syncytial Virus (RSV). RSV leads to inflammation and blockage in the tiny air passages of the lungs. Asthma or reactive airway disease is also a common cause, although it is often difficult to definitively diagnose in infancy.
Upper Airway Causes (Stridor)
The causes of stridor relate to obstruction or narrowing of the upper airway. The most frequent cause of acute stridor is Croup (laryngotracheobronchitis), a viral infection that causes swelling around the vocal cords. Laryngomalacia is the most common congenital cause of stridor, where soft tissues above the vocal cords temporarily collapse inward during inhalation. This condition is often present from birth and usually resolves without intervention by the time a child reaches two years of age.
Other Causes
A sudden onset of either wheezing or stridor, without preceding cold symptoms, raises concern for foreign body aspiration. This occurs when a child inhales a small object that becomes lodged in the airway, causing abrupt obstruction. Less common causes include tracheomalacia, where the tracheal cartilage is too soft, or external compression from a vascular ring. Gastroesophageal reflux disease (GERD) can also contribute, as refluxed stomach contents may irritate and inflame the airway, leading to obstruction.
Immediate Triage: Monitoring and Red Flags
When a baby makes a noisy breathing sound, parents must evaluate the baby’s overall effort and behavior. Respiratory distress means the baby is working harder than normal to breathe. Parents should observe for retractions, where the skin pulls inward between the ribs, under the breastbone, or at the neck with each breath. This sign indicates the use of accessory muscles to force air in, signaling struggling.
Other red flags include an increased breathing rate and nasal flaring, where the nostrils widen during inhalation. Parents must also watch for changes in the baby’s color, such as a bluish tint around the lips or on the fingernails, known as cyanosis. Cyanosis signals dangerously low oxygen levels. A decrease in alertness, lethargy, or extreme fussiness, along with difficulty feeding or inability to cry normally, are serious signs of oxygen deprivation.
If the baby exhibits a bluish color, is unresponsive, or is struggling so hard to breathe that they cannot make any noise, immediate medical help is required. Parents should call emergency services immediately. If the breathing effort is moderately increased but the baby is still alert, feeding, and maintaining a normal color, contact the pediatrician or visit an urgent care center.
Clinical Diagnosis and Treatment Approaches
Once a baby is under professional medical care, the first step involves a thorough physical examination and medical history to determine the sound’s origin and severity. A healthcare provider uses a stethoscope to confirm if the sound is true wheezing (lower airways) or stridor (upper airways). They will also measure the baby’s oxygen saturation using a pulse oximeter.
Diagnostic procedures may include a chest X-ray to look for signs of pneumonia, a foreign body, or structural anomalies. If a viral cause like RSV is suspected, a nasal swab may confirm the infection, guiding supportive care. When the cause is uncertain or structural issues are suspected, a specialist may perform a flexible laryngoscopy to visually examine the larynx and upper trachea.
Treatment is tailored directly to the underlying cause and the severity of distress.
Treatment for Wheezing
For wheezing caused by bronchiolitis, supportive care is primary, including adequate hydration and potentially administering humidified oxygen if saturation levels are low. Nebulized saline may be used to help loosen secretions and reduce airway resistance.
Treatment for Stridor
For stridor caused by Croup, steroids are often administered to reduce inflammation in the upper airway. Humidified air or nebulized epinephrine may be used in more severe cases. If a foreign body is confirmed, immediate intervention is necessary to remove the obstruction.