Stridor is an abnormal, high-pitched breathing sound that occurs when air struggles to pass through a narrowed or partially blocked upper airway. This turbulent airflow generates a harsh, often musical sound. While stridor can sometimes be mild and manageable, its presence always indicates air restriction and requires careful attention. Because the underlying cause can range from a minor infection to a complete obstruction, understanding the signs that signify an emergency is paramount.
Understanding the Sound of Stridor
The sound of stridor is produced by air moving rapidly through a significantly narrowed section of the airway. This contrasts with wheezing, which originates lower in the respiratory tract and is typically heard during exhalation. Stridor is most often heard during inspiration, pointing to a problem above the vocal cords in the larynx or pharynx.
The specific timing of the sound provides clues about the level of the obstruction. Inspiratory stridor suggests a blockage high up, such as in the voice box, while expiratory stridor points to a narrowing lower in the windpipe. If the sound is heard during both inhalation and exhalation, known as biphasic stridor, this usually indicates a fixed restriction just below the vocal cords.
The volume of the sound does not necessarily correlate with severity. A loud stridor indicates air is still moving with enough force to create turbulence. Conversely, a quiet or diminishing stridor suggests the airway is so narrowed that very little air is passing through. A sudden decrease in the sound can indicate near-total airway collapse.
Categorizing the Underlying Causes
Stridor is a sign, not a final diagnosis, caused by various conditions affecting the upper airway. These causes are generally grouped into infectious, mechanical, and congenital categories. Infectious causes are common, particularly in children whose smaller airways are prone to rapid swelling.
The most frequent infectious cause is Croup, a viral illness causing swelling of the voice box and windpipe, which produces a distinctive barking cough. Epiglottitis is a bacterial infection causing rapid swelling of the tissue flap covering the windpipe. Because Epiglottitis can lead to swift airway closure, it is treated as a medical emergency.
Mechanical causes involve physical blockage or injury. Aspiration of a foreign body, such as a small toy or food, is a common reason for sudden stridor. Other causes include direct neck trauma, inhaling corrosive substances, or complications following head or neck surgery.
Congenital causes are frequently seen in infants. Laryngomalacia, where soft tissue above the voice box partially collapses during inhalation, is the most common congenital cause. While this stridor is loud when the infant cries, it usually improves as the child grows. Fixed narrowing, such as subglottic stenosis, may require medical intervention.
Identifying Immediate Life-Threatening Signs
Stridor accompanied by signs of insufficient oxygen requires immediate attention. Respiratory distress is visible as retractions, where the skin pulls inward between the ribs, collarbone, or neck base. The nostrils may also flare as the body attempts to widen the air passages.
Any change in skin color is a sign of severely limited oxygenation. Cyanosis, a blue or dusky discoloration, is noticeable around the lips, on the tongue, or beneath the fingernails. This color change indicates a life-threatening drop in blood oxygen saturation.
A decline in mental status indicates the brain is not receiving enough oxygen. This manifests as lethargy, where the person is unusually sleepy or difficult to rouse, or as agitation and restlessness. In infants, a weak or absent cry or inability to feed signals significant respiratory compromise.
Associated symptoms help pinpoint the severity and underlying cause. Drooling or inability to swallow saliva, combined with a fever and reluctance to lie down, strongly suggests Epiglottitis. Sudden onset of stridor, particularly in a child playing with small objects, points to foreign body aspiration.
Immediate Actions During a Crisis
If any life-threatening signs are observed, call emergency services immediately. Time is of the essence when the airway is closing, and medical intervention is required to secure the airway. Do not attempt to transport the person yourself, as their condition could worsen rapidly.
While waiting for help, position the person to maximize airflow. Adults and older children should sit upright or lean forward to keep the airway open. Infants and young children should be held in an elevated position, as lying down often worsens the obstruction.
Avoid putting anything into the person’s mouth or throat. This is important if Epiglottitis is suspected, as stimulating the throat could trigger a spasm and airway closure. The only exception is if the person has aspirated a foreign object, requiring appropriate first aid maneuvers for choking.
Continuously monitor the person’s breathing effort, color, and level of consciousness until medical professionals take over. Keeping the person calm is important because crying or struggling increases oxygen demand and worsens turbulent airflow and swelling. Simple reassurance and a quiet environment help conserve energy and oxygen reserves.