Causes of acute respiratory distress in children

INTRODUCTION — This topic will review causes of acute respiratory distress in children. A detailed discussion of the approach to children with acute respiratory distress and approach to children with severe upper airway obstruction is found elsewhere. (See "Acute respiratory distress in children: Emergency evaluation and initial stabilization" and "Emergency evaluation of acute upper airway obstruction in children".)

Other related topics including the initial assessment and stabilization of children with respiratory and circulatory compromise and airway management techniques, including rapid sequence intubation (RSI), and conditions causing respiratory distress in newborns are discussed separately:

●(See "Initial assessment and stabilization of children with respiratory or circulatory compromise".)

●(See "Basic airway management in children".)

●(See "Technique of emergency endotracheal intubation in children".)

●(See "Rapid sequence intubation (RSI) in children for emergency medicine: Approach".)

●(See "Overview of neonatal respiratory distress and disorders of transition".)

●(See "Meconium aspiration syndrome: Pathophysiology, clinical manifestations, and diagnosis".)

●(See "Pathogenesis, clinical manifestations, and diagnosis of apnea of prematurity".)

DEFINITION — Respiratory distress results when breathing does not match the body’s metabolic demand for oxygen due to failure of oxygenation and/or ventilation. Respiratory distress is typically characterized by signs of increased work of breathing, such as tachypnea, use of accessory muscles, and/or retractions [1]. Head bobbing, nasal flaring and grunting are additional signs more commonly seen in very young children. A respiratory rate that is inappropriately slow for the clinical condition may also be a sign of respiratory distress and may portent impending respiratory arrest. An abnormal pattern of respiration is a sign of respiratory distress that may offer clues to etiology. (See "Acute respiratory distress in children: Emergency evaluation and initial stabilization", section on 'Evaluation'.)

Respiratory distress may develop in children due to multiple etiologies (table 1) that result from the following physiologic abnormalities:

●Hypoxemia. (See "Control of ventilation", section on 'Hypoxic challenge'.)

●Hypercarbia. (See "Control of ventilation", section on 'Hypercapnic challenge'.)

●Difficulty with the mechanics of respiration, typically from airway obstruction, muscle weakness, or discomfort (as may occur in patients who are splinting due to abdominal pain).

●Disordered control of ventilation, with which respiration may be depressed (eg, opioid overdose, severe head injury) or stimulated (eg, metabolic acidosis, hyperammonemia, salicylate intoxication).

Respiratory distress in response to hypoxemia or hypercarbia can rapidly progress to life-threatening respiratory failure. Neonates, infants, and young children are at particular risk given that they have higher oxygen consumption and less respiratory reserve. Children with inadequate respiratory effort (as can occur with fatigue, muscle weakness or CNS depression) can quickly develop significant physiologic compromise. (See "Emergency airway management in children: Unique pediatric considerations".)

Acute respiratory distress syndrome (ARDS) refers to diffuse alveolar injury that results in impaired gas exchange, decreased pulmonary compliance and increased pulmonary artery pressure. It has a multitude of etiologies including pulmonary infection, gastric content aspiration, smoke inhalation, environmental toxins, drugs, alcohol, nonfatal drowning, sepsis, trauma, chemotherapeutic agents, immunosuppressants, and lung or stem cell transplant [2]. (See "Acute respiratory distress syndrome: Epidemiology, pathophysiology, pathology, and etiology in adults", section on 'Pathophysiology'.)

By contrast, children with respiratory distress secondary to disordered control of breathing or to pain, who do not have significant cardiopulmonary disease or trauma, usually improve with treatment of the primary condition and do not generally progress to respiratory failure.

CAUSES — Many conditions may cause acute respiratory distress in children (table 1). The underlying etiology, while commonly within the respiratory system, may also be within other systems, and the etiology may not be immediately obvious (eg, fever and rales may be due to heart failure as the result of myocarditis rather than pneumonia, which is more common).

Immediately life-threatening conditions — Any process that causes respiratory distress by compromising ventilation and/or oxygenation can be life-threatening. Imminently life-threatening conditions require early recognition and immediate, aggressive intervention.

Severe upper airway obstruction — Patients with complete upper airway obstruction have no effective air movement, hence no audible speech, cry, or cough. They frequently assume a sniffing or tripod position in attempts to maintain their airway. Causes of complete upper airway obstruction include foreign body aspiration, angioedema from anaphylaxis, laryngospasm caused by hypocalcemia, and epiglottitis (table 2). Foreign body aspiration, anaphylaxis, and epiglottitis are discussed in detail separately. (See "Emergency evaluation of acute upper airway obstruction in children", section on 'Causes' and "Epiglottitis (supraglottitis): Clinical features and diagnosis" and "Anaphylaxis: Emergency treatment".)

Noisy inspiration (stridor) is a hallmark of severe partial upper airway obstruction although absence of stridor does not preclude significant partial airway obstruction, especially in a patient with depressed mental status. Common causes of severe partial upper airway obstruction include foreign body aspiration, infection (most commonly croup), and injury (such as airway thermal or chemical burns). Causes of acute upper airway obstruction that are commonly life-threatening are discussed separately (table 2). (See "Emergency evaluation of acute upper airway obstruction in children", section on 'Causes'.)

Tension pneumothorax — Tension pneumothorax is an acutely life-threatening emergency that develops when increased intrathoracic volume from air that has leaked into the pleural cavity causes a shift of mediastinal structures toward the opposite side, compressing the contralateral lung and cardiac vessels. It is rapidly fatal without immediate decompression.

Tension pneumothorax is usually due to penetrating or blunt trauma, including mechanical ventilation and cardiopulmonary resuscitation but it can also occur as the result of a spontaneous pneumothorax. Although tension usually develops immediately, it may be delayed for up to 24 hours, particularly if the pneumothorax is spontaneous and develops slowly.

Hallmarks of tension pneumothorax are:

●Severe respiratory distress

●Shift of mediastinal structures, including the trachea, toward the side contralateral to the collapsed lung

●Ipsilateral hyperexpansion of the chest

●Decreased or absent breath sounds and hyper-resonance to percussion on the ipsilateral side of the collapsed lung

In the rare patient with bilateral tension pneumothoraces, physical findings may be symmetric. Bedside ultrasound can rapidly confirm the diagnosis of pneumothorax. (See "Spontaneous pneumothorax in children", section on 'Clinical features' and "Clinical presentation and diagnosis of pneumothorax", section on 'Diagnostic imaging'.)

Needle decompression is a potentially life-saving, temporizing measure that any physician should be able to perform. If immediately available, a thoracostomy tube or pigtail catheter can be placed in children with a tension pneumothorax without first performing needle thoracostomy only if the tube can be placed without delaying decompression; otherwise needle thoracostomy should be performed immediately, followed by chest tube or pigtail catheter placement as soon as possible. (See "Thoracostomy tubes and catheters: Placement techniques and complications", section on 'Techniques' and "Thoracostomy tubes and catheters: Placement techniques and complications", section on 'Needle thoracostomy'.)

Pulmonary embolism — Pulmonary embolism (PE) is a life-threatening condition that can cause respiratory distress. It is an uncommon condition in children and is often associated with the use of central venous lines or other vascular devices [3]. Other risk factors for PE include immobility, a hypercoagulable state (such as factor V Leiden mutation, protein S or protein C deficiency), congenital heart disease, trauma, surgery, nephrotic syndrome, systemic lupus erythematosus, hormone birth control, malignancy and complications of some chemotherapeutic regimens (such as L-asparaginase and steroids for acute lymphoblastic leukemia). (See "Venous thrombosis and thromboembolism (VTE) in children: Risk factors, clinical manifestations, and diagnosis", section on 'Clinical manifestations'.)

Cardiac tamponade — Cardiac tamponade occurs when blood, serous fluid, or air under tension fills the pericardial sack, resulting in life-threatening compromise of venous return and decreased stroke volume. Cardiac tamponade can present acutely with hypotension. Children may also have signs of respiratory distress or apnea [4,5]. The classic signs of pericardial tamponade, referred to as Beck's triad (hypotension, jugular venous distention, and muffled heart sounds), are present in less than one-third of patients [4]. Pulsus paradoxus (a drop in the systolic blood pressure of >10 mmHg upon inspiration and, when severe, a weakening or disappearance of the peripheral pulse upon inspiration) is an indication for emergency pericardiocentesis in children with pericardial effusion. Bedside ultrasound can be used to rapidly identify fluid in the pericardial sac in patients with cardiac tamponade, and to guide pericardiocentesis. (See "Pulsus paradoxus in pericardial disease" and "Pulsus paradoxus in pericardial disease", section on 'Measurement of pulsus paradoxus' and "Pulsus paradoxus in pericardial disease", section on 'Pulsus paradoxus in cardiac tamponade' and "Emergency pericardiocentesis".)

Acute cardiac tamponade is rare in children and is usually the result of trauma, particularly penetrating cardiac injury. It is rapidly fatal. In children, accumulation of fluid in the pericardial sac is usually caused by infection, inflammation (most commonly collagen vascular disease), malignancy (eg, mediastinal lymphoma), or cardiac surgery (postpericardiotomy syndrome). Accumulation of pericardial fluid due to atraumatic etiology is usually insidious and less likely to progress to tamponade.

Other traumatic conditions — In addition to tension pneumothorax and cardiac tamponade, several other traumatic conditions may cause respiratory distress including:

●Flail chest – Flail chest occurs when multiple rib fractures result in a loss of stability of the chest wall. The flail segment retracts with inspiration and bulges with exhalation, resulting in inefficient expansion of the thorax, inefficient ventilation, and a significant increase in the energy expenditure for breathing (figure 1). The mechanism of injury usually is direct impact. Flail chest is uncommon in children because the greater deformability of immature bone makes rib fractures less likely than in adults, and when present, is often associated with pulmonary contusion. Even without rib fractures, children may have significant pulmonary injury. (See "Chest wall injuries after blunt trauma in children", section on 'Flail chest'.)

●Pulmonary contusion – In children, pulmonary contusion occurs when traumatic force is applied to the chest wall and results in parenchymal damage with hemorrhage and edema. The initial presentation of children with pulmonary contusion is often dominated by clinical features associated with extrathoracic injuries. Nevertheless, pulmonary contusion should be suspected in any child with significant blunt force to the thorax, whether or not there are signs of respiratory distress or chest wall injury. Decreased breath sounds, rales, or rhonchi may be noted on physical examination. Chest radiography should be performed for all children with respiratory distress and may reveal pulmonary contusion. Further imaging with computed tomography (CT) is not indicated for pulmonary contusion unless tracheobronchial, diaphragmatic or vascular injury is suspected. (See "Pulmonary contusion in children", section on 'Clinical features' and "Pulmonary contusion in children", section on 'Diagnosis'.)

●Pneumothorax – Pneumothorax occurs when air leaks from the lungs into the pleural space, resulting in collapse of the lung. It may be caused by blunt or penetrating trauma that creates air leak by directly damaging intrathoracic structures or indirectly due to increased intrathoracic pressure that ruptures respiratory structures. Ultrasound reveals echogenicity in the region of the uninflated lung. Ultrasound is more sensitive for diagnosis of pneumothorax than chest radiograph. (See "Clinical presentation and diagnosis of pneumothorax", section on 'Diagnostic imaging'.)

●Open pneumothorax – Pneumothorax due to a traumatic open chest wall wound occurs when ambient air enters the pleural space during inspiration through the chest wall defect (ie, a "sucking wound"). The air-filled space causes the lung within the injured hemithorax to collapse and shifts the mediastinum toward the unaffected hemithorax. During expiration, air exits the pleural space through the chest wall defect and the mediastinum swings back toward the injured hemithorax. Expiratory air from the normal lung (ie, "pendulum air") fills the collapsed lung. The "mediastinal flutter" may cause respiratory failure. Chest radiograph of an open pneumothorax is characterized by a visible chest wall defect and by massive expiratory mediastinal shift towards the injured side: this mediastinal behavior is different from tension pneumothorax where the expiratory shift of the mediastinum occurs towards the normal lung, resulting from air-trapping in the affected pleural space.

Treatment of open pneumothorax consists of immediately placing a sterile petroleum gauze over the open wound and taping on three sides to allow the dressing to act as a flutter valve that prevents air entry through the wound upon inspiration but allows air to escape during exhalation. A chest tube or pigtail catheter should be placed as soon as possible. (See "Thoracostomy tubes and catheters: Placement techniques and complications", section on 'Techniques'.)

●Hemothorax – In patients with massive hemothorax, respiratory distress results from the inability of the lung to expand on the affected side and from hemorrhagic shock. Thoracostomy tube placement and fluid resuscitation are key interventions. (See "Trauma management: Approach to the unstable child", section on 'Breathing'.)

●Smoke inhalation – Smoke inhalation may cause respiratory distress due to thermal injury to the upper and lower airways, hypoxic gas inhalation, bronchopulmonary exposure to toxins with direct lung injury, and/or systemic toxicity from carbon monoxide and cyanide. Thermal injury to the upper airway is suggested by stridor, respiratory distress, facial burns, oropharyngeal blisters or edema, and carbonaceous sputum and warrants early endotracheal intubation. (See "Inhalation injury from heat, smoke, or chemical irritants", section on 'General care' and "Inhalation injury from heat, smoke, or chemical irritants" and "Inhalation injury from heat, smoke, or chemical irritants", section on 'Initial management'.)

●Submersion injury – Children with nonfatal drowning, defined as a process resulting in primary respiratory impairment from submersion or immersion in a liquid medium, may have hypoxemia (due to fluid aspiration or reflex laryngospasm) resulting in noncardiogenic pulmonary edema and acute respiratory distress syndrome. Pulmonary insufficiency can develop insidiously or rapidly. Findings include tachypnea, dyspnea, rales, and wheezing. Chest radiograph may be normal or show focal or diffuse pulmonary edema. Symptoms and radiographs may worsen dramatically within hours. (See "Drowning (submersion injuries)".)

●Hemorrhagic shock – Massive hemorrhage can cause respiratory distress from hypoxia and acidosis (as the result of decreased oxygen carrying capacity due to red blood cell loss). (See "Trauma management: Approach to the unstable child", section on 'Circulation'.)

●Central nervous system trauma – Central nervous system injury involving the brain or spinal cord, may result in life-threatening apnea or respiratory depression. (See "Severe traumatic brain injury (TBI) in children: Initial evaluation and management", section on 'Secondary survey' and "Evaluation and acute management of cervical spine injuries in children and adolescents", section on 'Vital signs'.)

Biologic or chemical weapons — Several biologic and chemical agents that are potential weapons of terrorism or warfare produce respiratory distress as their most predominant effect [6,7]. Although exposure to these agents is fortunately rare, prompt recognition is essential to contain the exposure and prepare for mass casualties. Children often manifest symptoms prior to adults because of greater exposure per unit body mass, particularly since many agents are heavier than air and are therefore at greatest concentration lower to the ground, the level at which children breathe, and because children breathe at a faster rate and have less compensatory capacity. The respiratory symptoms are typically nonspecific. Biologic agents include, but are not limited to, inhalational anthrax, pneumonic plague, pneumonic tularemia, melioidosis, and the toxins staphylococcus enterotoxin B and ricin (see "Identifying and managing casualties of biological terrorism"). Chemical agents that can cause respiratory distress include chlorine, phosgene, sarin, ricin, and cyanide. (See "Chemical terrorism: Rapid recognition and initial medical management".)

Other nontraumatic conditions

Respiratory tract conditions — Respiratory distress can occur as the result of upper or lower respiratory tract processes. The clinical manifestations of respiratory distress depend, in part, on the location of the disease process. As an example, stridor develops in children with upper airway obstruction, whereas rales are characteristic of alveolar disease. (See "Acute respiratory distress in children: Emergency evaluation and initial stabilization", section on 'Physical examination'.)

Infections — Respiratory distress as the result of an infectious process usually develops gradually but can be acute in onset if structures of the upper airway are directly involved (eg, epiglottitis, severe croup). Patients are often febrile. (See "Emergency evaluation of acute upper airway obstruction in children".)

Common infectious causes of respiratory distress include:

●Peritonsillar abscesses – Peritonsillar abscess classically causes local pain, sore throat, trismus, difficulty swallowing, and muffled ("hot potato") voice. Patients with peritonsillar abscess exhibit tonsillar and peritonsillar swelling and erythema with deviation of the uvula to the unaffected side. It is rare that the swelling is so severe that it obstructs the oral airway enough to cause difficulty breathing. Peritonsillar abscess is most commonly caused by Group A streptococcus but can be caused by other bacteria and sometimes develops secondary to Epstein-Barr virus (ie, mononucleosis). Peritonsillar abscess is more common in older children and adolescents. The onset of symptoms is typically gradual. (See "Peritonsillar cellulitis and abscess", section on 'Evaluation'.)

●Retropharyngeal abscesses – Children with retropharyngeal abscesses may develop stridor and typical signs of respiratory distress if the abscess impinges on the trachea. Retropharyngeal abscess is more likely to develop in infants and toddlers and is unusual in children older than four years (image 1 and image 2). Additional findings include drooling, dysphagia, torticollis, meningismus, and change in voice. (See "Retropharyngeal infections in children", section on 'Clinical manifestations'.)

●Croup – Croup (laryngotracheobronchitis) is the most common infectious cause of upper airway obstruction in children between 6 and 36 months of age but can occur from early infancy through school age (image 3 and image 4). The etiology is usually viral (most commonly due to infection with parainfluenza virus) but may be caused by many other viral pathogens including pathogens that may also cause lower airway infection including respiratory syncytial virus (RSV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Spasmodic croup, also referred to as allergic croup is a noninfectious form of croup thought to be allergy mediated, given it is seen most often in patients with atopic disease. Most patients with spasmodic croup are older than those with infectious croup and many have recurrent episodes (See "Croup: Clinical features, evaluation, and diagnosis", section on 'Epidemiology' and "Croup: Clinical features, evaluation, and diagnosis", section on 'Etiology'.)

The onset of symptoms with croup due to infection is usually gradual, beginning with nasal congestion, and coryza. Symptoms generally progress over 12 to 48 hours to include fever (usually <39°C although may be higher especially if due to influenza or SARS-CoV-2) as well as barky cough and possibly hoarseness and/or stridor. Onset of spasmodic croup is abrupt, and symptoms are limited to barky cough. Barky cough, for infectious or spasmodic croup, most commonly begins during the night or with napping. Respiratory distress increases as upper airway obstruction becomes more severe. Rapid progression or signs of lower airway involvement suggests a more serious illness. Symptoms of viral croup typically persist for three to seven days with resolution of barky cough by day four in approximately 80 percent of children, with influenza and possibly SARS-CoV-2 causing more protracted illness than other viruses. Deviations from this expected course should prompt consideration of diagnoses other than laryngotracheitis. Spasmodic croup usually remits more quickly, sometimes within hours. Some children with severe or recurrent croup may have underlying airway abnormalities (eg, laryngomalacia, structural congenital airway abnormality, subglottic hemangioma, papillomatosis). (See "Croup: Clinical features, evaluation, and diagnosis", section on 'Clinical presentation' and "COVID-19: Clinical manifestations and diagnosis in children", section on 'Clinical manifestations'.)

●Bacterial tracheitis – Bacterial tracheitis is an invasive infection of the soft tissues of the trachea. Classically, it is caused by bacteria, most commonly Streptococcus or Staphylococcus aureus including MRSA (picture 1) as a secondary infection in a child with croup (image 5) but may occur as a primary infection. Increasingly, cases due to viral infection or cases in which no pathogen is identified have been reported. Patients with tracheitis may have rapid, dramatic and often transient decreases in oxygen saturation. In patients with respiratory failure due to upper airway infection, tracheitis is more common than epiglottitis or croup. The predominant clinical features of tracheitis are those of airway obstruction: stridor, cough, and respiratory distress accompanied by fever, highest in patients with bacterial or influenza as the etiology. Children younger than two to three years of age may be at increased risk for severe disease because of their relatively narrow airway diameter. In children with signs of total or near-total airway obstruction, airway control should precede diagnostic evaluation. (See "Bacterial tracheitis in children: Clinical features and diagnosis", section on 'Clinical features'.)

●Bronchiolitis – Bronchiolitis (caused most commonly by respiratory syncytial virus and not uncommonly by influenza or SARS-CoV-2) typically affects children younger than two years of age. It is characterized by several days of upper airway symptoms, most classically nasal congestion and copious nasal secretions, followed by onset of lower airway symptoms that include wheezing, rales, rhonchi, and cough. Neonates and very young infants may have apnea, and it may be the presenting manifestation. Peak severity of illness is usually between days 4 and 6 with resolution of symptoms between days 10 and 14. A detailed review of bronchiolitis can be found separately. (See "Bronchiolitis in infants and children: Clinical features and diagnosis".)

●Pneumonia – Pneumonia is a common cause of lower airway disease in infants and children. The disease process is more likely to be localized in the setting of bacterial pneumonia, whereas patients with viral and atypical pneumonias, such as Mycoplasma or Chlamydia, tend to have diffuse peribronchial, interstitial processes. (See "Community-acquired pneumonia in children: Clinical features and diagnosis", section on 'Clinical evaluation'.)

●COVID-19 – COVID-19, caused by SARS-CoV-2, should also be considered in acutely ill children even without known exposure. Respiratory findings may include tachypnea, hypoxia, shortness of breath, chest pain and/or cough; SARS-CoV-2 rarely causes serious respiratory illness in the pediatric age group. Chest radiograph may reveal bilateral consolidations and/or ground glass opacities. (See "COVID-19: Clinical manifestations and diagnosis in children", section on 'Severe disease in children'.)

Asthma — Bronchospasm due to reactive airways can cause severe respiratory distress. It may be triggered by infection, exercise, environmental irritants, stress, and/or gastroesophageal reflux. Respiratory distress from bronchospasm may be exacerbated by alveolar disease (as a result of infection) and/or atelectasis. Assessment of severity and acute management of children with asthma exacerbations in the outpatient setting are discussed separately. (See "Acute asthma exacerbations in children younger than 12 years: Emergency department management" and "Acute asthma exacerbations in children younger than 12 years: Overview of home/office management and severity assessment", section on 'Assessment of exacerbation severity'.)

Anaphylaxis — Anaphylaxis (most commonly caused by food or medications) may be severe and life-threatening, particularly when edema involves the retropharynx and/or larynx. In the lower airways, anaphylaxis usually causes bronchospasm (table 3). Onset is usually within one hour, often within minutes, and there may be associated signs and symptoms, including facial swelling, urticaria, pruritus, vomiting; and less commonly, hypotension, dizziness, decreased level of consciousness, and/or syncope. (See "Anaphylaxis: Acute diagnosis", section on 'Symptoms and signs'.)

Foreign body — Foreign bodies that partially obstruct the upper airway or those lodged in the lower airways or esophagus, are not usually acutely life-threatening but often cause respiratory distress. Children with a foreign body in the upper airway, or with an esophageal foreign body compressing the airway, are more likely to acutely develop severe symptoms, typically choking, drooling, dysphagia, and/or stridor. In comparison, foreign body in the lower airway, most commonly manifests as unilateral wheeze, but presentation may be delayed days to weeks and manifest as fever, rales, or cough due to foreign body-induced infection. Children with significant upper airway obstruction may develop pulmonary edema following relief of the obstruction (see "Airway foreign bodies in children", section on 'Presentation'). Rarely, a foreign body lodged in the esophagus will cause esophageal erosion resulting in esophageal stricture, tracheal esophageal fistula, and/or mediastinitis. (See "Foreign bodies of the esophagus and gastrointestinal tract in children", section on 'Clinical manifestations'.)

Airway anomalies — Fixed and functional congenital abnormalities of the airway that include vocal cord paralysis, mass, laryngeal cleft, tracheal stenosis, ring, sling, tracheoesophageal fistula, subglottic hemangioma, laryngomalacia, tracheomalacia, and/or bronchomalacia may all cause respiratory distress most commonly in the neonate or infant. Adenotonsillar hypertrophy, laryngospasm, hypocalcemic tetany, paradoxical vocal cord movement, vocal cord paralysis, and papillomatosis are acquired causes of upper airway obstruction that may occur at any age.

Pulmonary edema — Noncardiogenic pulmonary edema may occur from upper airway obstruction (such as from foreign body or croup), pulmonary irritants, submersion injury, severe central nervous system insult and acute salicylate toxicity. (See "Neurogenic pulmonary edema" and "Salicylate (aspirin) poisoning: Clinical manifestations and evaluation", section on 'Pulmonary edema'.)

Chest wall and thoracic cavity abnormalities — Disease processes involving the chest wall structure (such as asphyxiating thoracic dystrophy, muscular dystrophy, severe pectus excavatum) may severely restrict lung expansion, limiting ventilatory efforts. (See "Chest wall diseases and restrictive physiology".)

Mass lesions in the chest or mediastinum may be congenital or acquired and include diaphragmatic hernia, esophageal anomalies, bronchopulmonary sequestration, benign and malignant masses and vascular anomalies. They cause respiratory compromise usually by compression of the airway or as space-occupying lesions. (See "Bronchopulmonary sequestration" and "Overview of common presenting signs and symptoms of childhood cancer", section on 'Mediastinal masses' and "Approach to the adult patient with a mediastinal mass".)

Pleural effusion may be caused by infection, inflammation, ischemia, malignancy, organ failure, drug hypersensitivity, venous or lymphatic obstruction and trauma. In children, infectious causes are most common. The onset and progression of respiratory distress is usually gradual. (See "Epidemiology, clinical presentation, and evaluation of parapneumonic effusion and empyema in children", section on 'Clinical presentation'.)

Cardiovascular conditions — Cardiovascular causes of respiratory distress may be congenital or acquired.

Congenital heart disease — Congenital cardiac anomalies with right-to-left shunting of deoxygenated blood result in reduced oxygen saturation of blood entering the systemic circulation, causing hypoxia with cyanosis (table 4). Signs of respiratory distress other than cyanosis may not be present, however, unless the child is also in heart failure. (See "Cardiac causes of cyanosis in the newborn".)

Acute decompensated heart failure — Heart failure may develop due to a congenital or acquired cardiac condition. For congenital heart defects, the time of onset of congestive heart failure (CHF) is dependent on the specific heart defect and its severity. As an example, a newborn with an obstructive left-sided heart lesion, such as severe coarctation of the aorta, may develop severe CHF when the ductus arteriosus closes. (See "Cardiac causes of cyanosis in the newborn", section on 'Left-sided obstructive lesions'.)

The most common acquired conditions that cause CHF in children are myocarditis and supraventricular tachycardia that persists for more than 12 to 24 hours. Other conditions include valvular heart disease, myocardial dysfunction, sepsis, metabolic disturbance, fluid overload, severe anemia, ischemia, and myocardial infarction. (See "Clinical manifestations and diagnosis of myocarditis in children" and "Clinical features and diagnosis of supraventricular tachycardia (SVT) in children", section on 'Heart failure' and "Heart failure in children: Etiology, clinical manifestations, and diagnosis".)

Respiratory manifestations of CHF include tachypnea, dyspnea, orthopnea, cough, wheeze, and rales. Other manifestations include poor feeding, tiring with feeds, failure to thrive, pallor, diaphoresis, tachycardia, murmur, gallop, rub, thready pulses, jugular venous distension, cardiomegaly, hepatomegaly, and/or edema.

Pericarditis — Inflammation of the pericardium from pericarditis may cause chest pain that results in splinting with respiration and if severe, could compromise cardiac output resulting in inadequate oxygenation. (See "Acute pericarditis: Clinical presentation and diagnosis", section on 'Clinical features'.)

Cardiac arrhythmia — Both tachyarrhythmias and bradyarrhythmias can cause respiratory distress if circulatory function is inadequate to meet tissue demands especially if circulatory compromise results in metabolic acidosis. Supraventricular tachycardia is the most common arrhythmia in children and can cause heart failure with tachypnea as a manifestation. Ventricular tachycardia, atrial fibrillation, atrial flutter, and atrioventricular block are less common and more likely to occur in children with underlying structural heart disease or in the case of AV bock, in patients with Lyme disease. (See "Clinical features and diagnosis of supraventricular tachycardia (SVT) in children" and "Management and evaluation of wide QRS complex tachycardia in children".)

Myocardial infarction — Coronary vasospasm (variant angina) and myocardial infarction are rare causes of respiratory distress and are associated with chest or supraumbilical abdominal pain in children and adolescents. Coronary vasospasm is associated with transient ischemic changes on ECG, normal coronary arteriography, reversible septal akinesia by echocardiography, and cardiac enzyme elevation. (See "Vasospastic angina" and "Causes of nontraumatic chest pain in children and adolescents", section on 'Cardiac disease'.)

In children without underlying cardiac conditions, myocardial infarction occurs more frequently in adolescent males and is associated with smoking and substance abuse, most commonly cocaine and amphetamines.

Neurologic and muscle diseases — Central nervous system (CNS) disturbances typically cause respiratory compromise because of impaired ventilation. Conditions may be congenital (such as CNS malformation, neuromuscular disease, seizures) or acquired (eg, intoxication, CNS infection, seizures, or brain or spinal cord trauma) and may involve the central and/or the peripheral nervous system (table 5). Children with central causes may have hypo or hyperventilation, decreased gag reflex, and/or decreased pharyngeal tone. Associated neurologic findings include focal neurologic deficits, hypo or hypertonia, and/or altered level of consciousness. Fever, headache, posterior neck pain, meningismus and/or altered level of consciousness suggest CNS infection, including meningitis, encephalitis, brain abscess, or an intracranial vascular event. (See "Evaluation of stupor and coma in children", section on 'Evaluation'.)

Acute muscle weakness may result in dysfunction of respiratory muscles causing respiratory compromise. Etiologies include conditions that affect the cerebral cortex, spinal cord, anterior horn cell, peripheral nerve, neuromuscular junction, and muscle (table 6). (See "Etiology and evaluation of the child with weakness".)

Gastrointestinal conditions — Gastroesophageal reflux can cause stridor due to irritation of infraglottic structures, or pneumonia due to aspiration. (See "Clinical manifestations and diagnosis of gastroesophageal reflux disease in children and adolescents", section on 'Clinical manifestations'.)

Abdominal processes that cause pain (such as appendicitis or intraabdominal injury) or distention (as with a small bowel obstruction) may cause respiratory distress as the result of splinting or interference with excursion of the diaphragm. (See "Acute appendicitis in children: Clinical manifestations and diagnosis", section on 'Clinical manifestations' and "Intestinal malrotation in children", section on 'Clinical presentation'.)

Metabolic and endocrine diseases — Tachypnea, with or without hyperventilation, may occur as a compensatory mechanism in children with metabolic acidosis from any cause, such as diabetic ketoacidosis, shock, metabolic disease, or ingestion (table 7). (See "Approach to the child with metabolic acidosis".)

Less common metabolic and endocrine conditions that may result in tachypnea include disorders that cause hyperammonemia (because ammonia stimulates central hyperventilation), mitochondrial disorders (through interruption of oxygen metabolism) and hyperthyroidism (as a result, in part, of increased metabolic rate). (See "Urea cycle disorders: Clinical features and diagnosis", section on 'Clinical features'.)

Hematologic conditions — Respiratory distress may develop in patients with decreased oxygen delivery to tissues due to acute onset of severe anemia (eg, hemolytic uremic syndrome, autoimmune hemolytic anemia, aplastic crisis) or the presence of a significant amount of abnormal hemoglobin with decreased or absent oxygen-carrying capacity (eg, sickle cell disease, methemoglobinemia, carbon monoxide poisoning). See selected topic reviews.

Neonatal polycythemia may cause respiratory distress as a result of compromised oxygen delivery due to sludging of blood and/or acute decompensated heart failure. (See "Neonatal polycythemia", section on 'Signs and symptoms'.)

Acute on chronic diseases — Children with chronic disease may develop acute respiratory distress or worsening of a chronic respiratory condition. Examples include:

●Children who have chronic causes of upper airway obstruction (such as laryngotracheomalacia, an anatomic abnormality of the airway, or adenotonsillar hypertrophy) often have worsening obstruction when they develop an acute condition such as an upper respiratory tract infection (table 8A-B). (See "Assessment of stridor in children" and "Emergency evaluation of acute upper airway obstruction in children", section on 'Causes'.)

●Children with chronic pulmonary disease such as cystic fibrosis or bronchopulmonary dysplasia are at increased risk for bronchopulmonary infections. Patients with asthma are at increased risk for pneumothorax and pneumomediastinum, which may cause chest pain and respiratory distress that persists despite treatment that improves bronchospasm. (See "Cystic fibrosis: Clinical manifestations of pulmonary disease" and "Bronchopulmonary dysplasia (BPD): Management and outcome", section on 'Acute exacerbations'.)

●Acute chest syndrome, defined as chest pain and infiltrate on chest radiograph, is a cause of respiratory distress that occurs in children with sickle cell disease. (See "Acute chest syndrome (ACS) in sickle cell disease (adults and children)", section on 'Definitions and pediatric-adult differences'.)

●Patients with neuromuscular disease may develop upper airway obstruction from poor pharyngeal muscle tone, pneumonia from aspiration, and/or atelectasis from impaired respiratory effort. (See "Respiratory muscle weakness due to neuromuscular disease: Clinical manifestations and evaluation".)

SUMMARY

●Definition – Respiratory distress results when breathing does not match the body’s metabolic demand for oxygen due to failure of oxygenation and/or ventilation. Respiratory distress is typically characterized by signs of increased work of breathing, such as tachypnea, use of accessory muscles, and/or retractions. Head bobbing, nasal flaring, and grunting are additional signs more commonly seen in very young children. A respiratory rate that is inappropriately slow for the clinical condition may also be a sign of respiratory distress and may indicate impending respiratory arrest. An abnormal pattern of respiration is a sign of respiratory distress that may offer clues to etiology. (See 'Definition' above.)

Respiratory distress may develop in children due to multiple etiologies that result from (table 1) (see 'Definition' above):

•Hypoxemia. (See "Control of ventilation", section on 'Hypoxic challenge'.)

•Hypercarbia. (See "Control of ventilation", section on 'Hypercapnic challenge'.)

•Difficulty with the mechanics of respiration, typically from airway obstruction, muscle weakness, or discomfort (as may occur for patients who are splinting due to abdominal pain).

•Disordered control of ventilation, in which respiration may be depressed (eg, opioid overdose, severe head injury) or stimulated (eg, metabolic acidosis, hyperammonemia, salicylate intoxication).

Respiratory distress in response to hypoxemia or hypercarbia can rapidly progress to life-threatening respiratory failure. Neonates, infants, and young children are at particular risk because they have higher oxygen consumption and less respiratory reserve. (See 'Definition' above and "Emergency airway management in children: Unique pediatric considerations".)

●Causes – Many conditions may cause acute respiratory distress in children (table 1). The inciting condition, while commonly within the respiratory system, may be due to a condition within other systems, and may not be immediately obvious (eg, fever and rales may be due to heart failure due to myocarditis rather than pneumonia, which is more common). (See 'Causes' above.)