Respiratory emergencies in children
Respiratory Care Journal
Alexandre T Rotta MD
Budi Wiryawan MD
Acute obstructive respiratory emergencies in children are a common cause of emergency department visits. The severity of these conditions ranges from mild, self-limited disease to life-threatening forms of rapidly progressive airway obstruction. A high index of suspicion is necessary for prompt diagnosis and treatment.
Respiratory failure is the most common cause of cardiopulmonary arrest in pediatric patients. Therefore, prompt recognition, assessment, and expert management of respiratory emergencies are critical to obtaining the best possible outcome. Anatomical differences between pediatric and adult patients render children more susceptible to acute airway com-promise. Young children have proportionally larger heads, prominent occiputs, and relatively lax cervical support, which increase the likelihood of airway obstruction in the supine position. A relatively large tongue in comparison to a small oropharynx further contributes to this problem.
The subglottis is the narrowest segment of the pediatric airway, in contrast to the glottis in adults. The subglottic region is completely encircled by the cricoid cartilage, thus restricting its ability to freely expand in diameter. Furthermore, the subglottic airway contains loosely attached connective tissue that can rapidly cause substantial reduction in airway caliber should inflammation and soft tissue edema develop.
There are many potential causes of respiratory emergencies in children, including infections, inflammatory and allergic processes, foreign body aspirations or ingestions, trauma, chemical or thermal injuries, neoplasms, neurological syndromes, and congenital anomalies. This review discusses the emergency recognition and management of common conditions presenting with acute onset and that can rapidly progress to airway compromise, obstruction, and respiratory failure.
Croup (Laryngo tracheobron
chitis)
Croup or laryngotracheobronchitis (LTB) is the most common cause of infectious airway obstruction in children, with an annual incidence of 18 per 1,000 children in the United States. It primarily affects children between the ages of 6 months and 4 years, with a peak incidence of 60 per 1,000 among children 12 years of age. LTB is epidemic in nature, with peak incidence during early fall and winter, although sporadic cases may be seen throughout the year.
The most common etiologic agent is the parainfluenza virus type 1, although parainfluenza types 2 and 3, influenza A and B, respiratory syncytial virus, adenovirus, Mycoplasma pneumoniae, herpes simplex type 1, and numerous other organisms have also been implicated.
LTB has a broad disease severity spectrum. Most children who are seen in clinics and emergency departments return home for supportive care. Hospitalization rates ranging from 1 to 30% have been reported for patients in the more severe end of the spectrum. Endotracheal intubation and mechanical ventilation are needed in approximately
Processes that lead to obstructive respiratory
emergencies are common in the pediatric
population. Many of these entities can progress
rapidly, creating a life-threatening situation.
The clinician must maintain a high index of
suspicion and make a rapid and precise
diagnosis,
oftentimes based solely on the patients brief
history or a
limited
examination.
2% of hospitalized children, although the need for intubation appears to be diminishing because of the increasing use of glucocorticoids. The typical LTB patient presents with a several-day history of upper respiratory-type symptoms, progressing to hoarseness, the characteristic barky (seal-like) cough, and stridor.
The stridor is most commonly an inspiratory sound, with biphasic stridor indicating more severe narrowing of the airway. Breath sounds are generally clear except for transmitted upper airway sounds. The presence of biphasic stridor, nasal flaring, intercostal and suprasternal retractions, tachypnea, and low pulse oximetry values should be seen as signs of impending respiratory collapse. Low-grade fever is a common finding with LTB patients.
The hemogram may show leukocytosis with a viral differential, although a normal white cell count is commonly found. The diagnosis of classic viral LTB should be made clinically, posing little challenge to the experienced practitioner. In fact, only approximately 2% of patients initially diagnosed with croup are given an incorrect diagnosis. Radiographic examination of the soft tissues of the neck may help establish the diagnosis of croup, while ruling out other important conditions such as epiglottitis, hemangioma, congenital abnormality, foreign body, or retropharyngeal abscess.
The classic radiographic finding of LTB on the frontal view is a narrowing of the subglottic area, commonly known as the steeple sign. The absence of this finding, however, does not rule out the diagnosis of LTB, since as many as half of patients may have normal neck radio-graphs. When visible, the subglottic narrowing is dynamic and is more accentuated during inspiration, because of the more negative intraluminal airway pressure during inspiration.
LTB is usually self-limited and frequently requires only supportive care. Less than 10% of LTB patients require hospitalization and management is largely dependent on the severity of respiratory symptoms. Traditionally, patients with LTB have been treated with humidified air, as either heated or cool mist. The rationale for this practice includes soothing the inflamed mucosa, decreasing the amount of coughing due to mucosal irritation, and liquefying secretions for easier expectoration. Unfortunately, no scientific evidence exists to support the idea that humidified air has any effect on the subglottic mucosa or that it positively influences patient outcome. Furthermore, mist tents can increase respiratory distress by provoking anxiety and upsetting the patient because of separation from the parents. Another potential disadvantage of the mist tent is the reduced ability to closely observe the child because he or she is behind a plastic wall. Despite the lack of objective benefit, humidified air continues to be used by many in the treatment of LTB, largely based on anecdotal evidence.
Nebulized racemic epinephrine is an important treatment for LTB patients, as the vasoconstrictive adrenergic effect on the mucosal vasculature is highly effective in rapidly reducing airway edema.
The use of corticosteroids for LTB has been the topic of substantial debate. Recent studies have shown substantial improvement in children with severe LTB treated with corticosteroids. In these studies corticosteroids were beneficial regardless of the route of administra- The study by Johnson et al compared patients treated with placebo, nebulized budesonide, or a dose of 0.6 mg/kg dexamethasone either orally, intramuscularly, or intravenously, and found a lower hospitalization rate among patients treated with any type of steroid, compared to placebo. The precise mechanism of action of steroids in LTB is not known.
Spasmodic Croup
The term spasmodic croup describes a condition clinically similar to LTB. Patients with spasmodic croup typically have a barking cough and stridor, but lack fever and a viral prodrome. Its onset tends to be abrupt, usually at night, and it often improves within hours either with cool humidified air or without intervention. The precise pathogenesis of spasmodic croup is unknown, although it is thought to be allergic or angioneurotic in origin, as opposed to infectious. Treatment for severe forms of spasmodic croup is the same as for viral LTB.
Epiglottitis
Epiglottitis is a serious, life-threatening infection of the extrathoracic airway and is an airway emergency. The term epiglottitis is somewhat misleading, since the process is actually a cellulitis of supraglottic structures, including the posterior lingual surface and surrounding soft tissues, the epiglottis and the aryepiglottic folds, thus making supraglottitis a more appropriate designation. Supraglottitis is classically described in children between 2 and 8 years of age, although it can occur at any age.
Haemophilus influenzae type B is the most common causative organism, although many other agents have been reported, including viruses, group A -hemolytic Streptococcus, pneumococci, staphylococci, Klebsiel-la, Pseudomonas, and Candida.
Bacterial Tracheitis
Bacterial tracheitis, also known as bacterial laryngotracheobronchitis or pseudomembranous croup, was first described in detail by Jones et al in 1979. This is a rare disease, with a peak incidence during fall and winter months, predominantly in children between the ages of 6 months and 8 years (mean age of 5 years).This condition is characterized by marked subglottic edema and thick mucopurulent (membranous) secretions.
Retropharyngeal Abscess
Retropharyngeal abscesses are serious infections of the normally sterile retropharyngeal space. Under normal conditions, this space contains loose connective tissue and lymph nodes that drain the nasopharynx, paranasal sinuses, middle ear, teeth, and adjacent bones. Retropharyngeal abscesses generally result from lymphatic spread of infection, although direct spread from contiguous areas, trauma, or foreign bodies can also play a role. Retropharyngeal abscesses are more common in young children, with the vast majority of cases occurring in patients younger than 6 years of age. This may be due to the fact that retro-pharyngeal lymph nodes are abundant in young children but suffer progressive involution and atrophy in older patients.
Foreign Bodies
Foreign body aspiration or ingestion can lead to partial obstruction of the airway or a catastrophic complete obstruction that can lead to death in a matter of minutes. The victim of an airway obstruction caused by a foreign body is generally asymptomatic prior to the event. Airway compression or obstruction by the foreign body leads to the acute onset of symptoms. Clinical symptoms and signs include coughing fits and increased respiratory difficulty, such as the use of accessory muscles, nasal flaring, stridor, or wheezing, depending on the anatomical location and severity of the obstruction.
A foreign body lodged in the extrathoracic airway typically causes inspiratory or biphasic stridor. An intrathoracic foreign body is associated with expiratory or biphasic wheezing. The clinical presentation of these types of airway obstructions may be complicated by the fact that signs and symptoms will change, depending on the location of the foreign body and whether it migrates up or down the airway over time. For instance, a toddler may be very symptomatic after a choking spell with severe stridor and retractions due to a subglottic foreign body, only to have no evidence of respiratory distress and mild expiratory wheezing when the object moves into the right main bronchus. Signs and symptoms of airway obstruction are not exclusive of airway foreign bodies. An ingested object that is unable to progress down the esophagus can cause inflammation and compression of the posterior wall of the trachea and lead to a clinical picture almost indistinguishable from that of a foreign body lodged in the airway.
Radiopaque foreign bodies can be easily diagnosed by radiograph. Frontal and lateral views of the neck and chest should be used to further localize the object to the esophagus or airway. Flat foreign bodies, such as coins, that enter the esophagus tend to assume a coronal orientation, owing to the fact that the narrowest diameter of the esophageal lumen at rest is antero-posterior.
Esophageal foreign bodies will generally obstruct in one of 3 sites: immediately distal to the pyriform sinus, at the level of the aortic arch, or at the cardia. The diagnosis of a nonradiopaque foreign body poses a much greater challenge. Intrathoracic foreign bodies located beyond the carina may be diagnosed by dynamic radiographic (fluoroscopic) examination or by the use of inspiratory and expiratory radiographs showing asymmetric pulmonary aeration. Young children unable to cooperate with instructions to inspire and forcefully exhale can be studied in the right and left lateral decubiti, since the dependent side simulates the lung aspect during exhalation. A patient who has a highly suggestive clinical picture should undergo a diagnostic and therapeutic endoscopy, despite a negative radiograph.
Inhalational Injuries
Inhalational injuries are frequently associated with major burns in victims of fires in enclosed spaces. In fact, inhalational injuries are responsible for approximately 50 80% of the mortality attributed to burns. Inhalational injuries lead to morbidity and mortality by 3 distinct but frequently overlapping processes: airway thermal burn, asphyxia (carbon monoxide or cyanide poisoning), and pulmonary injury from smoke inhalation.
Thermal injury to the airway by inhalation of hot gas is generally limited to the supraglottic airway. This sparing of the subglottic airway and trachea is related to a protective reflex of vocal cord closure upon exposure to heat. In addition, air is a poor conductor of heat, which, coupled with the efficient heat exchange characteristics of the upper airway, contributes to the cooling of hot inspired gas before it reaches the lungs. Substantial direct pulmonary injury, however, is known to occur when steam is inhaled. This is because steam has approximately 4,000 times the heat-carrying capacity of dry air and easily overwhelms the upper airways ability to equilibrate the temperature of the inspired gas.
Processes that lead to obstructive respiratory emergencies are common in the pediatric population. Many of these entities can progress rapidly, creating a life-threatening situation. The clinician must maintain a high index of suspicion and make a rapid and precise diagnosis, oftentimes based solely on the patients brief history or a limited examination. In the setting of obstructive airway emergencies, appropriate treatment needs to be implemented without delay. This generally involves assuring the presence of a patent airway while time, supportive therapies, and (when appropriate) antibiotics contribute to the resolution of the baseline process.
