In PALS (Pediatric Advanced Life Support), upper airway obstruction in children most commonly results from infections like croup, foreign body aspiration, anaphylaxis, and trauma. Children are particularly vulnerable to airway obstruction because their airways are anatomically smaller and structured differently than adult airways. The narrowest point in a child’s airway sits at the subglottic level, near the cricoid cartilage, which means even a small amount of swelling can dramatically reduce airflow. In an infant with a 4 mm airway, just 1 mm of circumferential swelling increases airway resistance 16-fold.
How Stridor Points to the Obstruction Level
Stridor is the hallmark sound of upper airway obstruction, and its timing during breathing tells you where the problem is. Inspiratory stridor (heard during breathing in) points to an obstruction at the larynx. Expiratory stridor (heard during breathing out) suggests a tracheobronchial obstruction lower in the airway. Biphasic stridor, audible during both inspiration and expiration, typically indicates a problem at the subglottic or glottic level. Recognizing this pattern helps narrow the cause quickly in an emergency.
Croup: The Most Common Infectious Cause
Viral laryngotracheobronchitis, or croup, is the single most common infectious cause of upper airway obstruction in children. It’s usually caused by parainfluenza viruses, particularly parainfluenza type 1, which tends to cause seasonal outbreaks. The illness typically starts with one to two days of runny nose, cold symptoms, and low-grade fever (or no fever at all), then progresses to the characteristic barky, seal-like cough and inspiratory stridor as the subglottic area swells.
Most cases are mild and self-limiting. Severity is assessed based on the presence and timing of stridor, the degree of chest wall retractions, air entry, level of consciousness, and whether cyanosis is present. A mild case involves an occasional barky cough with no stridor at rest and little or no retractions. Moderate croup produces frequent barky cough, stridor at rest, and visible retractions. Severe croup adds marked retractions and significant distress, while impending respiratory failure shows a depressed level of consciousness, poor air entry, and cyanosis or pallor.
Epiglottitis
Epiglottitis is a bacterial infection of the epiglottis that constitutes a true medical emergency because of the risk of rapid progression to complete airway obstruction. Before widespread vaccination against Haemophilus influenzae type b (Hib), this was a major cause of pediatric airway emergencies. Since the introduction of the Hib conjugate vaccine in the early 1990s, pediatric epiglottitis has become rare, which paradoxically makes recognition and early diagnosis more challenging when it does occur. A small number of cases still happen, sometimes caused by other organisms.
Unlike croup, epiglottitis typically presents with a toxic-appearing child, high fever, drooling, and a preference for sitting upright in the “tripod” or “sniffing” position. The child often looks much sicker than a child with croup and deteriorates faster.
Bacterial Tracheitis
Bacterial tracheitis is rare but important to recognize because it can mimic severe croup that isn’t responding to treatment. It often starts as what looks like a typical viral croup episode, but then symptoms worsen. The child develops high fevers, appears toxic, and shows severe respiratory distress. The key differentiator: bacterial tracheitis does not improve with the standard croup treatments (corticosteroids and nebulized epinephrine). The most common culprit is Staphylococcus aureus, though several other bacteria can be responsible.
Foreign Body Aspiration
Foreign body aspiration is a significant cause of accidental death in infants and young children, largely because infants explore the world by putting objects in their mouths. The symptoms depend on where the object lodges. A foreign body stuck in the glottic or subglottic airway produces sudden-onset stridor and respiratory distress that can look a lot like croup. An object lodged lower in the trachea or bronchi tends to cause coughing and wheezing that mimics asthma or bronchiolitis.
The most dangerous objects are round or cylindrical items that can form a complete seal of the airway: hot dogs, sausages, grapes, and marbles. Uninflated balloons are particularly hazardous for the same reason. Certain aspirated items carry additional risks beyond simple obstruction. Batteries can erode the airway lining. Peanuts release oils that trigger intense inflammation in the bronchial tubes. Sharp objects like bones, safety pins, or needles can perforate the airway and migrate into surrounding structures. Any of these warrants urgent surgical consultation.
Anaphylaxis and Angioedema
Anaphylaxis can produce rapid, life-threatening upper airway obstruction through angioedema, a type of swelling that affects deeper tissue layers. Signs and symptoms typically begin within about 15 minutes of exposure to an allergen. Early symptoms include itching of the eyes, nose, and throat, facial flushing, and a tightening sensation in the throat. This can quickly progress to stridor, wheezing, hives, a rapid heart rate, and cardiovascular collapse.
In a pediatric emergency setting, anaphylaxis is identified when two or more body systems are involved rapidly after allergen exposure. These include skin or mucosal changes (hives, flushing, swollen lips or tongue), respiratory compromise (stridor, wheezing, difficulty breathing), drops in blood pressure with signs like fainting or limpness, and persistent gastrointestinal symptoms like crampy abdominal pain or vomiting.
Trauma and Post-Intubation Swelling
Direct trauma to the airway, whether blunt or penetrating, can cause swelling and blood accumulation that obstruct breathing. Blunt trauma is more common than penetrating trauma in children and is most frequent in adolescents. Thermal or chemical injuries, such as from inhaling hot gases or caustic substances, also damage the upper airway and produce significant swelling.
Even routine medical procedures can cause obstruction. Tracheal intubation creates pressure against the airway lining, and the reactive swelling that follows can worsen after the tube is removed. This post-extubation swelling develops in the glottic or subglottic mucosa and is particularly dangerous in smaller pediatric airways where there is very little margin for any reduction in airway diameter.
Other Infectious Causes
Several less common infections can also obstruct the upper airway in children. A retropharyngeal abscess forms when infection spreads through lymph nodes in the back of the throat, usually involving a mix of bacteria including staph and strep species. Peritonsillar abscess (sometimes called quinsy) is actually the most common deep-space head and neck infection in both adults and children, with Streptococcus pyogenes as the predominant organism. Infectious mononucleosis, caused by Epstein-Barr virus, can produce upper airway obstruction through massive tonsillar swelling, though the classic warning signs of stridor and respiratory distress may not appear until late in the process. Diphtheria, once the most common infectious cause of acute upper airway obstruction in children, is now rare in vaccinated populations but remains a concern in areas with low immunization rates.