Acute respiratory distress in children: Emergency evaluation and initial stabilization

INTRODUCTION — This topic will review the emergency evaluation and initial stabilization of children with acute respiratory distress.

The initial assessment and stabilization of children with respiratory and circulatory distress, basic airway management, emergency endotracheal intubation, rapid sequence intubation (RSI), causes of respiratory compromise in children, and conditions causing respiratory distress in neonates 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 "Causes of acute respiratory distress in children".)

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

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

BACKGROUND — Respiratory disorders account for almost 10 million of the 30 million emergency department visits by children in the United States annually, and acute respiratory infections, particularly pneumonia, pulmonary tuberculosis, and asthma, are among the leading causes of death in young children worldwide [2,3]. Respiratory distress in children, particularly neonates and infants, must be promptly recognized and aggressively treated because they may decompensate quickly. Factors that contribute to rapid respiratory compromise in children include smaller airways, increased metabolic demand, decreased respiratory reserve, and inadequate compensatory mechanisms compared with adults. Respiratory arrest is the most common cause of cardiac arrest in children, and outcomes are poor for patients who develop cardiopulmonary arrest because of respiratory deterioration. (See "Emergency airway management in children: Unique pediatric considerations" and "Pediatric basic life support (BLS) for health care providers", section on 'Epidemiology and survival'.)

INITIAL STABILIZATION — Respiratory distress must be promptly recognized and treated. Delay may result in respiratory failure [4], cardiopulmonary arrest, and death. Airway and breathing interventions in patients with signs of impending respiratory failure should be initiated prior to full evaluation. Definitive diagnosis based on history, signs and symptoms of illness, underlying conditions, and evaluation should be established as expeditiously as possible to guide treatment of specific underlying conditions (algorithm 1). (See "Causes of acute respiratory distress in children", section on 'Immediately life-threatening conditions' and "Emergency evaluation of acute upper airway obstruction in children".)

In patients with signs of shock, appropriate circulatory resuscitation should also be provided. (See "Initial evaluation of shock in children" and "Shock in children in resource-abundant settings: Initial management".)

Rapid assessment — The pediatric assessment triangle (PAT) focuses the initial evaluation of acutely ill or injured children on appearance, breathing, and circulation to quickly identify conditions that require immediate intervention. The PAT is reviewed separately. (See "Initial assessment and stabilization of children with respiratory or circulatory compromise", section on 'Pediatric assessment triangle'.)

Features of the PAT that are specific to children with acute respiratory distress include [1]:

●Appearance – Restlessness, agitation, and combativeness are early manifestations of air hunger or hypoxia. Somnolence and lethargy are indicative of severe hypoxia, hypercarbia, and/or respiratory fatigue.

●Breathing – Tachypnea is usually the initial sign of respiratory compromise. Abnormal airway sounds (eg, stridor, wheezing), nasal flaring, head bobbing, increased accessory muscle use, and positioning to maximize airway opening are other indicators of respiratory compromise. Children with upper airway obstruction often assume a "sniffing" position (neck flexed, head extended (picture 1)), while those with lower airway obstruction may sit in the "tripod" position (upright and leaning forward on outstretched hands (picture 2)). Nasal congestion in neonates and young infants may result in significant respiratory distress. Inability to handle secretions and/or swallow are signs of oropharyngeal or laryngotracheal obstruction.

As respiratory distress progresses, respiratory rate often decreases and the pattern of respirations becomes irregular and, particularly in neonates and young infants, may progress to apnea. These are ominous signs. Without intervention, respiratory arrest quickly ensues.

●Circulation – Pallor, ashen color, and cyanosis are concerning findings that may indicate hypoxemia but may also be observed in patients with shock.

This assessment should take less than one minute. Throughout this evaluation, every reasonable effort must be made to keep the child calm and comfortable because anxiety and crying can substantially increase the work of breathing in young children by decreasing upper airway diameter and increasing metabolic demand for oxygen. The child should be positioned or allowed to maintain the position that best supports their respiratory effort.

Support airway, breathing, and circulation — Initial management should focus on the support of airway, breathing, and circulation [1,5]:

●Airway – Key steps in basic airway management include (see "Basic airway management in children"):

•Provide 100 percent inspired oxygen.

•Allow the child to assume a position of comfort. As needed to relieve upper airway obstruction, manually open the airway with a jaw thrust (figure 1) (trauma patients) or chin lift (picture 3).

•Clear the airway (suction).

•Insertion of an artificial airway is warranted if a jaw thrust and/or chin lift do not relieve the obstruction or if there is altered or decreasing levels of consciousness. A nasopharyngeal airway (picture 4) may be used in an awake, semiconscious, or unconscious patient; oropharyngeal airway (picture 5) should be inserted only if the patient is comatose and the gag reflex is absent.

●Breathing – The clinician should:

•Assist ventilation manually in patients not responding to basic airway maneuvers or with inadequate or ineffective respiratory effort [6].

In preparation for intubation, 100 percent oxygen should be administered via nonrebreather mask or other high-concentration device. If the patient has evidence of respiratory failure, positive pressure ventilation should be initiated with a bag-valve mask or flow-inflating device to oxygenate and improve ventilation. (See "Basic airway management in children".)

•Monitor oxygenation by pulse oximetry.

•Monitor ventilation by end-tidal carbon dioxide (EtCO₂) in intubated patients to confirm tracheal intubation. Assess adequacy of ventilation and, in intubated patients undergoing cardiopulmonary resuscitation (CPR), when feasible, to confirm tracheal intubation, assess effectiveness of CPR, identify return of spontaneous circulation (ROSC), and guide decisions regarding continued CPR in patients not responding to CPR. EtCO₂ measured by side port nasal cannula may also be useful in selected nonintubated patients with respiratory distress who are spontaneously breathing to inform effectiveness of ventilation and perfusion, assess response to treatment, and diagnose metabolic acidosis. (See "Carbon dioxide monitoring (capnography)".)

•Administer medications as needed to treat underlying cause (eg, inhaled albuterol for status asthmaticus or inhaled racemic epinephrine for croup).

●Circulation – Key interventions consist of monitoring heart rate and rhythm and establishing vascular access to provide volume administration and/or medications for resuscitation. (See "Vascular (venous) access for pediatric resuscitation and other pediatric emergencies".)

Massive hemorrhage can cause respiratory distress as the result of decreased oxygen-carrying capacity and shock. Airway management should be performed with cervical spine immobilization when cervical spine injury cannot be ruled out. Bedside ultrasound can be performed to rapidly identify pleural, pericardial, and intra-abdominal fluid. Therapeutic fluid resuscitation should include early administration of blood products to restore oxygen-carrying capacity. (See "Trauma management: Approach to the unstable child", section on 'Fluid resuscitation'.)

Emergency conditions — Several conditions associated with acute respiratory distress (eg, acute upper airway obstruction, tension pneumothorax, impending respiratory arrest, and acute cardiac tamponade) require immediate, life-saving interventions.

Acute upper airway obstruction — Children with upper airway symptoms such as choking, gagging, changes in voice, and/or stridor are likely to have an upper airway obstruction as the etiology of their distress. Initial management depends upon the degree and cause of obstruction (table 2):

●Complete upper airway obstruction caused by a foreign body warrants immediate basic life support interventions (ie, back blows under one year of age versus abdominal thrusts over one year of age, a finger sweep for a visible foreign body, and attempted bag-mask ventilation), an emergency call to an anesthesiologist and, if less invasive measures fail, advanced airway procedures to reestablish oxygenation and ventilation (algorithm 2). (See "Emergency evaluation of acute upper airway obstruction in children", section on 'Suspected foreign body'.)

●Given the risk of sudden decompensation, patients with significant laryngotracheal injury, thermal or chemical epiglottitis, and progressive partial upper airway obstruction warrant immediate preparation for airway management and an emergency consultation, as available, with an anesthesiologist, pediatric intensivist, and/or an otolaryngologist to help secure the airway. Bag-mask ventilation may temporarily provide oxygenation until a definitive airway is established. In cases that progress to complete airway obstruction that does not respond to bag-mask ventilation, endotracheal intubation or, if unsuccessful, a surgical tracheal airway may be necessary. (See "The difficult pediatric airway for emergency medicine".)

Pneumo- or hemothorax — Pneumothorax or hemothorax most commonly occurs in patients who have sustained chest trauma. Patients with tension pneumothorax typically have marked respiratory distress with decreased breath sounds on the affected side; the rare patient with bilateral pneumothoraces may have symmetrically decreased breath sounds on examination. Bedside ultrasound can be used to rapidly diagnose pneumothorax and hemothorax. (See "Overview of intrathoracic injuries in children", section on 'Pneumo- and hemothorax'.)

Other findings with tension pneumothorax include:

●Chest hyperexpansion on the affected side

●Tracheal deviation with shift of trachea to opposite side (not reliably seen in young children)

●Cardiovascular compromise progressing to shock

Tension pneumothorax or bilateral pneumothoraces may be rapidly fatal and require immediate decompression by needle thoracostomy. Bedside ultrasound can be diagnostic and, when equipment and trained personnel are immediately available, should be rapidly performed to confirm pneumothorax (algorithm 3) (see "Bedside pleural ultrasonography: Equipment, technique, and the identification of pleural effusion and pneumothorax", section on 'Ultrasonography findings'). However, needle decompression should not be delayed in the unstable patient. Once needle decompression has been accomplished, then chest tube or pigtail catheter placement is indicated. (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'.)

Open pneumothorax, in addition to pigtail or chest tube decompression, requires covering the open wound with an occlusive dressing taped on three sides to avoid reaccumulation of pleural air.

Hemothorax causing respiratory distress warrants immediate chest tube decompression and fluid replacement with prioritization of blood products as appropriate. (See "Causes of acute respiratory distress in children", section on 'Tension pneumothorax' and "Overview of intrathoracic injuries in children", section on 'Pneumo- and hemothorax'.)

Impending respiratory arrest — Typical signs of impending respiratory arrest include:

●Markedly impaired air entry

●Apnea

●Slow or irregular respirations

●Poor respiratory effort

Regardless of the underlying cause, children with respiratory failure should receive bag-mask ventilation and, if unsuccessful, placement of an artificial airway, ideally via endotracheal intubation or, if not possible, with a laryngeal mask airway or an alternative device. A rapid overview describes the steps in performing rapid sequence intubation (RSI) (table 3). (See "Technique of emergency endotracheal intubation in children" and "Rapid sequence intubation (RSI) in children for emergency medicine: Approach".)

Selected patients with respiratory failure may respond to noninvasive ventilation (high-flow nasal cannula [HFNC], continuous positive airway pressure [CPAP], or bilevel positive airway pressure [BiPAP]) if airway reflexes are preserved as discussed separately. (See "High-flow nasal cannula oxygen therapy in children" and "Noninvasive ventilation for acute and impending respiratory failure in children", section on 'Patient selection'.)

Acute cardiac tamponade — Acute cardiac tamponade abruptly presents with:

●Respiratory distress

●Tachypnea

●Jugular venous distension (rare in infants and toddlers)

●Hypotension

The child may also have chest pain and muffled heart sounds.

Whenever possible, bedside ultrasound should be used to rapidly identify fluid in the pericardial sac and to guide pericardiocentesis (figure 2 and figure 3 and figure 4). (See "Emergency pericardiocentesis" and "Causes of acute respiratory distress in children", section on 'Cardiac tamponade'.)

EVALUATION — The evaluation of a child with acute respiratory distress includes determining the severity as well as the underlying cause. Tachypnea and retractions are hallmarks of respiratory distress. Respiratory distress may manifest as inadequate respiratory effort, most often in those who have tired from attempts to compensate for respiratory compromise (eg, severe bronchiolitis), those with underlying neuromuscular disease, and those with disordered control of breathing (eg, seizure, opioid overdose). Prolonged tachypnea and decreased respiratory effort can lead to respiratory failure and/or arrest.

The emergency evaluation of the child with respiratory distress must first determine the severity of respiratory distress and the need for emergency intervention. Features of the history and physical examination will ideally localize the source as well as suggest the etiology and direct initial treatment (table 4). Ancillary studies can then be performed as indicated to confirm the diagnosis and guide management (table 5). The clinical features and evaluation of specific conditions that cause acute respiratory distress in children are discussed separately. (See "Causes of acute respiratory distress in children".)

Regardless of etiology, the initial management of respiratory distress in children requires immediate evaluation and supportive care of airway, breathing, and circulation. For some conditions, specific interventions (ie, bronchodilator therapy for asthma or decompression of a pneumothorax) may rapidly relieve symptoms. With prompt aggressive treatment of respiratory distress and its underlying cause, most children with respiratory distress recover uneventfully. Delay in respiratory support can lead to respiratory arrest, which is the leading cause of cardiopulmonary arrest in children.

History — A detailed history should be obtained once the child's condition is stabilized. (See "Initial assessment and stabilization of children with respiratory or circulatory compromise", section on 'Initial stabilization'.)

Helpful historical information includes:

●Symptoms

•Onset and duration– The abrupt onset of gagging or choking suggests upper airway conditions, such as an aspirated foreign body, allergy, or irritant exposure. A change in voice (either muffled or hoarse) also indicates an upper airway process. A child who suddenly complains of chest pain may have a spontaneous pneumothorax or, less likely, cardiac tamponade. A child who gradually develops tachypnea and retractions may have asthma, bronchopulmonary infection, lower airway foreign body, pleural effusion, a slowly enlarging pneumothorax, or heart failure.

•Associated symptoms – Fever suggests an infectious etiology. A child with tachypnea without fever, upper respiratory infection symptoms, or cough may be compensating for metabolic acidosis. A complaint of abdominal pain may indicate a gastrointestinal process (eg, appendicitis or bowel obstruction), diaphragmatic irritation from a pneumonic condition (as can occur with basilar pneumonia and/or pleural effusion), or a metabolic abnormality (eg, ketoacidosis from diabetes).

●Contributing history

•Trauma – A history of recent trauma suggests specific diagnoses, such as pneumothorax, pulmonary contusion, flail chest, cardiac tamponade, and intra-abdominal and/or central nervous system (CNS) injury.

•Exposures – Exposure to specific infections (including influenza and SARS-CoV-2), toxins (including medications, smoke inhalation, substances of abuse, and biologic, chemical, or nuclear agents), or allergens may suggest an etiology for respiratory distress.

•Recent travel – Approximately 20 percent of recent travelers develop respiratory infections, most of which are upper airway infections. The CDC website provides information on outbreaks and pathogens that, while rare in the United States, may be present in other countries and can cause serious respiratory compromise. The prevalence of coronavirus disease 2019 (COVID-19) and the causative variant differs by region. (See "COVID-19: Epidemiology, virology, and prevention".)

Influenza season in the Southern Hemisphere is April through September and peaks during June through August. In the tropics, influenza is a risk throughout the year. Measles can also cause respiratory distress due to croup, pneumonia, and/or bronchiolitis.

●Past medical history, family history

•Previous episodes – Information regarding previous episodes of respiratory distress, including treatments that have been used and their effect, may guide interventions. As an example, an infant or child who is wheezing may have had previous episodes that responded to bronchodilators.

•Underlying medical conditions – Respiratory distress may be an acute manifestation of a process associated with a specific chronic medical condition (eg, acute chest syndrome in a child with sickle cell disease) or a complication of a chronic condition (eg, pneumothorax in a patient with cystic fibrosis or pulmonary embolus in a patient with a history of a deep vein thrombosis or inherited thrombophilia). (See "Causes of acute respiratory distress in children", section on 'Acute on chronic diseases'.)

•Family history – Family history of inheritable conditions (including asthma, cardiac disease, and diabetes mellitus) may give clues to possible undiagnosed etiologies of respiratory distress.

Physical examination — The initial physical examination of the child with severe respiratory distress should be completed rapidly, focusing on the respiratory and cardiovascular systems but recognizing that other organ system processes may be the etiology of respiratory distress [7]. (See 'Rapid assessment' above.)

After rapid assessment of airway, breathing, and circulation, vital signs including pulse oximetry and, whenever possible, measured weight (rather than estimated weight) should be obtained. Side-port capnography is helpful in detecting hypercarbia in selected patients. Once the child is stabilized, the clinician should perform a complete physical examination.

Vital signs — Respiratory rate, heart rate, blood pressure, temperature, and oxygen saturation give clues to the presence and etiology of respiratory distress.

●Respiratory rate – Normal respiratory rate varies by age (table 1). Tachypnea is one of the most important findings in children with respiratory conditions. Tachypnea may also occur due to fever, activity, crying, cardiac disease, metabolic acidosis, and hyperammonemia.

Study of the relationship between fever and respiratory rate, in over 91,400 febrile children <5 years of age without lower respiratory tract infection, revealed an increase of almost 3 breaths per minute per degree Celsius (range of 2.0 to 4.0 increased breaths per degree Celsius) depending on height of fever, with maximum increases between 38 and 39.9°C [7]. (See "Causes of acute respiratory distress in children", section on 'Causes'.)

Apnea and bradypnea in neonates and infants with respiratory disease is usually the result of respiratory muscle fatigue. In neonates, particularly premature neonates, central immaturity is a common cause of apnea. In young infants, apnea may be the initial manifestation of bronchiolitis or pertussis.

Other common etiologies of apnea in infants and young children include choking, breath holding, head trauma (including abusive head trauma), and poisoning.

●Heart rate – Tachycardia due to increased sympathetic tone is commonly present in children with respiratory distress. The magnitude in heart rate elevation is highly variable. With prolonged respiratory distress, tachycardia may reflect dehydration due, at least in part, to fever and/or tachypnea.

Bradycardia in a hypoxemic child is a late and ominous sign that often signals impending cardiopulmonary arrest.

●Pulsus paradoxus – Although not specific, the presence of pulsus paradoxus is an important indicator of severe respiratory distress and/or decreased cardiac output. In patients with lower airway disease, pulsus paradoxus (ie, >10 mmHg drop in systolic blood pressure during inspiration) correlates with the degree of airway obstruction that occurs as the result of accentuated swings in pleural pressure between inspiration and expiration. It also occurs when hyperinflation of the lungs limits inspiratory filling (and therefore left ventricular stroke volume of the heart).

In addition, pulsus paradoxus is seen in patients with cardiac tamponade. Accurate measurement of pulsus paradoxus is often difficult in young children. (See "Cardiac tamponade", section on 'Pulsus paradoxus'.)

●Oxygen saturation – A resting room air oxygen saturation persistently ≤97 percent by pulse oximetry is abnormal in full-term infants and children, although this measurement should not be considered in isolation in any individual patient [8]. Values ≤90 percent indicate significant tissue hypoxemia.

Both inadequate waveform capture and medical conditions may result in erroneous oxygen saturation readings (table 6). (See "Pulse oximetry", section on 'Troubleshooting sources of error'.)

Breathing — A detailed assessment of breathing consists of inspection, abnormal sounds, auscultation, palpation, and percussion.

●Inspection – Some of the most valuable information regarding the severity and etiology of respiratory distress is obtained by careful observation, noting:

•Position – Children will assume a position of comfort that best supports their respiratory effort:

-Sniffing position: Children with epiglottitis may position themselves with the neck extended forward (picture 1).

-Torticollis may be seen in children with retropharyngeal abscess.

-Upright position is usually assumed by patients with croup who have stridor.

-Tripoding: Children with severe upper or lower airway obstruction such as asthma may lean forward possibly with their weight on the hands of their extended arms and with their head in the sniffing position (picture 2).

•Respiratory pattern – Rate, depth, and rhythm of respiration may provide a clue to the etiology of respiratory distress:

-Rapid, shallow breathing with prolonged exhalation is typically seen with air trapping, as occurs with asthma, bronchiolitis, or an airway foreign body beyond the carina. It may also result from chest or abdominal pain or chest wall dysfunction.

-Kussmaul respirations (deep, regular, sighing breaths with any rate) suggest metabolic acidosis, particularly due to diabetic ketoacidosis.

-Cheyne-Stokes respirations (respirations with increasing then decreasing depth and rate alternating with periods of apnea) occur as the result of CNS immaturity in otherwise normal neonates, particularly during sleep. This pattern can also be seen in neonates, infants, and children with inadequate cerebral perfusion, brain injury, increased intracranial pressure, or central opioid depression.

-Ataxic respirations (breaths of irregular depth interrupted irregularly by periods of apnea) suggest CNS infection, injury, or drug-induced depression.

-Thoracoabdominal dissociation or paradoxical breathing (chest collapses on inspiration, while abdomen protrudes) is a sign of respiratory fatigue or muscle weakness.

•Tracheal deviation – Tracheal deviation is a key finding in tension pneumothorax. Air accumulation between the visceral and parietal pleura on the affected side displaces the trachea to the side opposite of the pneumothorax.

Tracheal deviation may also be seen in patients with pulmonary emphysema, unilateral effusion, or a thoracic mass.

•Accessory muscle use – Accessory muscle use is an important indicator of respiratory distress in infants and children:

-Nasal flaring, exaggerated opening of the nostrils during inspiration, is a subtle form of severe accessory muscle use.

-Head bobbing, extension of the head and neck during inhalation and falling forward of the head during exhalation, is most likely to be seen in infants and can be easily overlooked.

-Retractions of the muscles of the chest wall result from high negative intrathoracic pressure generated by increased respiratory effort. Supraclavicular and suprasternal retractions are usually indicative of upper airway obstruction but may be seen with severe lower airway processes.

Intracostal and subcostal retractions are indicators of lower airway obstruction but can be seen in severe upper airway obstruction. Mild retractions may be normal in infants. Severe retractions of more than one muscle group indicate significant distress.

-Abdominal breathing, characterized by thoracoabdominal dissociation, in which the chest collapses and the abdomen protrudes on inspiration, may be normal in infants, but, beyond infancy or in patients with poor muscle tone, is concerning for respiratory muscle fatigue.

•Chest wall movement – Chest excursion with inspiration is an indication of tidal volume. Poor movement indicates inadequate ventilation. In addition, asymmetric movement suggests a localized process such as a pneumothorax or flail chest.

●Abnormal sounds — Many abnormal sounds can be appreciated without auscultation, including:

•Stertor – Stertor (snoring) due to nasal obstruction is most commonly caused by nasal congestion, tonsil and/or adenoid hypertrophy, or neuromuscular weakness.

•Gurgling – Gurgling, which may be inspiratory and/or expiratory, is due to secretions in the posterior oropharynx, trachea, and/or bronchi.

•Stridor – Stridor is a high-pitched inspiratory sound that localizes respiratory distress to the upper airway and can be caused by conditions such as croup, tracheitis, retropharyngeal abscess, and upper airway foreign body.

•Change in voice – An abnormal voice, most commonly hoarse or muffled, suggests upper airway obstruction.

•Aphonia – Aphonia results from complete upper airway obstruction or vocal cord dysfunction.

•Cough – Acute cough may be due to infection, inflammation, bronchospasm, and/or obstruction. The quality of the cough provides clues to etiology:

-A barky cough indicates subglottic tracheal obstruction, most commonly due to croup.

-A staccato cough suggests pneumonia caused by Chlamydia or Mycoplasma species.

-A dry, tight cough may occur in patients with wheezing due to asthma or bronchiolitis.

-A loose, wet cough may indicate tracheal secretions or bacterial pneumonia.

•Grunting – Grunting is an end expiratory sound that occurs as the result of exhalation against a partially closed glottis. It slows expiratory flow and increases lung volume and alveolar pressures.

Grunting is typically a sign of moderate to severe respiratory distress that occurs in infants and young children with lower airway disease, such as pneumonia, atelectasis, or pulmonary edema. It may also be heard in children with abdominal processes that limit respiratory effort due to pain and/or abdominal distension (eg, intra-abdominal injury or a perforated viscous).

●Auscultation – Lung auscultation provides important information regarding the etiology of respiratory distress and localization of the underlying condition. Every effort should be made to quiet the infant or child during auscultation, as these findings may be subtle and difficult to appreciate when the patient is crying.

The presence of the following should be noted:

•Wheezing – Diffuse expiratory wheezes are a sign of lower airway intrathoracic obstruction typically caused by asthma or bronchiolitis. The breath sounds are musical in tone. However, asthma may be so severe that air movement is poor, and wheezes may not be heard.

Unilateral wheezes may be appreciated if there is a foreign body in the lower airway.

Inspiratory wheezes can be from asthma, an upper airway extrathoracic obstruction, or a severe fixed intrathoracic obstruction such as laryngeal edema or a foreign body.

•Prolonged expiratory phase – A prolonged expiratory phase is a reliable sign of obstructed lower airways that can occur with or without wheezes. An expiratory phase that is longer than the inspiratory phase suggests obstruction even in the absence of wheezes.

•Upper airway sounds – Transmitted upper airway sounds are noted commonly in small children. Noises generated in the upper airway (ie, stertor due to nasal obstruction from congestion) are easily heard homogeneously throughout the lung fields, particularly in neonates and infants because of their small size and thin-walled chest. Inspiratory stridor suggests significant narrowing of the airway above the sternal notch.

While stridor does not result in lower airway sounds, etiologies that cause stridor may also impact the lungs. When stertor and stridor cannot be distinguished, auscultation over the nose and trachea is often helpful.

•Decreased breath sounds – Decreased breath sounds noted in localized lung fields may be the result of a pneumothorax, or from focal lower airway processes such as pneumonia, pleural effusion, or atelectasis.

•Crackles – Also known as rales, crackles are typically high-pitched sounds heard during inspiration, often late phase, as deflated small airways reinflate. Inspiratory crackles are heard in conditions such as bronchiolitis, pneumonia, or pulmonary edema. They may be particularly audible with deep inspirations.

Less commonly, crackles are heard during expiration. Crackles are an indication of inflammation or infection of small bronchi, bronchioles, and alveoli. Expiratory crackles may be heard in patients with bronchiolitis, asthma, cystic fibrosis, and lower airway foreign body. They can be accentuated by having infants and children exhale forcefully as if blowing out candles. Crackles that clear with coughing are usually not significant.

•Rhonchi – Rhonchi are harsh, low-pitched rattling sounds heard during inspiration or expiration due to airway obstruction from secretions, edema, or inflammation.

•Bronchophony, pectoriloquy, and egophony – With bronchophony, spoken diphthong syllables that start as one vowel and change to another, such as "toy boat" or "blue balloon," are heard more distinctly over an area of consolidation.

With pectoriloquy, the syllable, when whispered, is louder in the area of consolidation.

Egophony is a change in sound, such as "ee" to "ay" with consolidation.

These findings may be helpful in older, cooperative children but are less reliable findings in children younger than five years of age because breath sounds are easily transmitted throughout the chest.

•Pleural rub – A pleural rub is a low-pitched grating sound heard with inspiration and expiration caused by inflammation of pleural surfaces with friction as they move against each other during respiration. A pleural rub may be associated with pneumonia or a lung abscess.

•Pericardial rub – A pericardial rub occurs when inflamed parietal and visceral pericardial surfaces rub against each other. It is heard best between the apex and the sternum and may only be heard or be accentuated by having the patient lean forward. It may be difficult to distinguish from pleural rub.

Hamman's crunch or sign describes pericardial crackles heard near the heart in synchrony with the heartbeat. This finding results from the heart beating against air-filled tissues in patients with pneumomediastinum, pneumopericardium, tracheobronchial injury, or left-sided pneumothorax.

●Palpation and percussion – The following signs elicited by palpation and percussion of the chest indicate a respiratory tract etiology for respiratory distress, but absence of these findings does not exclude the associated conditions:

•Crepitus – Subcutaneous air due to an air leak (eg, pneumothorax, pneumomediastinum) causes crepitus, a crunching sensation beneath the skin during palpation over the neck and chest.

•Fremitus – Fremitus is palpable vibration of the thoracic wall. Tactile fremitus, vibration elicited by speaking diphthong phrases, such as "toy boat" or "blue balloons," is focally increased over an area of consolidation and decreased over pneumothorax or pleural effusion.

•Percussion – Hyperresonance with percussion of the chest wall may indicate air trapping in patients with asthma or bronchiolitis or air leak in patients with pneumothorax.

Dullness with percussion suggests an area of consolidation (eg, atelectasis, bronchopneumonia, pleural effusion).

The level of lung percussion during full inspiration and full expiration, used to assess diaphragmatic movement, suggests air trapping when elevation of the diaphragm is decreased during expiration and intra-abdominal distention, or organomegaly when downward movement of the diaphragm is decreased during inspiration.

Other organ systems — Findings in other organ systems can indicate an etiology for the child's respiratory distress other than pulmonary disease (see "Causes of acute respiratory distress in children", section on 'Other nontraumatic conditions'):

●Central nervous system – Altered mental status and abnormal respiratory rate and/or pattern may accompany a variety of pulmonary conditions. An altered mental status can also indicate serious CNS disease, such as infection, trauma, toxic ingestion, hyperammonemia, and/or seizure. (See "Evaluation of stupor and coma in children", section on 'Etiologies' and "Approach to the child with occult toxic exposure", section on 'Altered mental status'.)

●Heart – Respiratory distress in a patient with signs of cardiac compromise, such as a gallop murmur, jugular venous distention, or hepatomegaly, may be due to heart failure or cardiogenic shock. (See "Initial evaluation of shock in children", section on 'Circulation'.)

●Gastrointestinal tract – Rapid, shallow respirations and/or grunting in a child is a finding concerning for severe respiratory distress. If no pulmonary etiology is apparent, then the clinician should evaluate for an intra-abdominal process suggested by abdominal tenderness and/or distension, including intraabdominal injury or other pathologic condition with or without peritonitis. (See "Causes of acute abdominal pain in children and adolescents".)

●Metabolic – Metabolic acidosis resulting from an inborn error of metabolism or toxic ingestion (eg, methanol, ethylene glycol, salicylates) may cause significant tachypnea or Kussmaul breathing. Hyperammonemia may cause tachypnea due to brainstem stimulation. (See "Inborn errors of metabolism: Epidemiology, pathogenesis, and clinical features" and "Methanol and ethylene glycol poisoning: Pharmacology, clinical manifestations, and diagnosis" and "Salicylate (aspirin) poisoning: Clinical manifestations and evaluation".)

●Endocrine – Rapid, deep respirations in a child who has no evident pulmonary condition may be caused by severe metabolic acidosis in a child with diabetic ketoacidosis. Additional clinical findings include polydipsia, polyuria, weight loss, dehydration, fruity breath, and abdominal pain. (See "Diabetic ketoacidosis in children: Clinical features and diagnosis", section on 'Signs and symptoms'.)

●Allergy – Urticaria, facial swelling, and/or oropharyngeal edema suggest an anaphylactic reaction in patients with respiratory distress and stridor or wheezing. (See "Anaphylaxis: Acute diagnosis", section on 'Symptoms and signs'.)

Ancillary studies — The clinical evaluation is often all that is required to diagnose the etiology of respiratory distress. Diagnostic tests should be used selectively based upon clinical findings and the likelihood that the study results will change management (table 5).

Bedside evaluation — Children with respiratory distress should have hemoglobin oxygen saturation measured with pulse oximetry as early as possible during their evaluations. (See "Pulse oximetry".)

End-tidal carbon dioxide (EtCO₂) or transcutaneous carbon dioxide measurement, if available, can be used to assess ventilation in patients with findings of respiratory distress. (See "Initial assessment and stabilization of children with respiratory or circulatory compromise", section on 'Ancillary studies'.)

Laboratory testing — The extent of laboratory testing depends upon the severity of respiratory distress and the ability to diagnose the underlying etiology based upon clinical findings alone. For example, patients with moderate respiratory distress from an obvious etiology that responds to interventions (eg, children with status asthmaticus who improve after receiving bronchodilators and corticosteroids) usually do not require specific testing.

Patients who have findings of severe respiratory distress warrant measurement of a venous or arterial blood gas to assess ventilation and more accurately determine oxygenation. These measurements can be correlated with continuous noninvasive monitoring with pulse oximetry and EtCO₂ measurement and can help determine the need for further airway management, such as endotracheal intubation. (See "Initial assessment and stabilization of children with respiratory or circulatory compromise", section on 'Arterial blood gas/venous blood gas'.)

Other studies may be necessary depending upon clinical findings (table 5):

●Complete blood count with differential in patients with suspected infection or anemia

●Viral studies for COVID-19, influenza, or other respiratory viral pathogens, particularly in high-risk patients or those in extremis

●Rapid blood glucose, electrolytes, and blood gas in a patient with suspected diabetic ketoacidosis

●Troponin, brain natriuretic peptide (BNP) and/or D-dimer in patients with chest pain

●Blood, urine, and cerebrospinal fluid cultures in a child with fever and altered mental status

Imaging — While not all etiologies of respiratory distress require imaging for identification, selective imaging may establish the etiology for a patient's respiratory distress (table 5):

●Plain radiographs – Neck, chest, and/or abdominal radiographs may be informative.

•A soft tissue radiograph of the lateral neck may identify:

-Retropharyngeal abscess (image 1 and image 2) (see "Retropharyngeal infections in children")

-Bacterial tracheitis (image 3) (see "Bacterial tracheitis in children: Clinical features and diagnosis")

-Epiglottitis (image 4) (see "Epiglottitis (supraglottitis): Clinical features and diagnosis")

-Radiopaque foreign body (image 5) (see "Foreign bodies of the esophagus and gastrointestinal tract in children")

-Croup (typically a clinical diagnosis) (image 6 and image 7)

•Anteroposterior (AP) and lateral chest radiographs can localize and identify pulmonary and cardiac etiologies based on findings such as pulmonary consolidation, atelectasis, pleural and/or pericardial fluid, and air leak.

●Bilateral, lateral decubitus chest radiographs, or in the child able to cooperate for inspiratory and forced expiratory chest radiographs, asymmetric hyperinflation suggests a nonradiopaque foreign body on the hyperinflated side (image 8). If chest radiographs are equivocal, further evaluation depends upon the level of clinical suspicion (algorithm 4). (See "Airway foreign bodies in children".)

●Supine and upright, or lateral decubitus, abdominal radiographs may provide clues to an intra-abdominal etiology of respiratory distress (eg, perforated viscus or intestinal obstruction).

●Echocardiogram may be indicated in patients with cardiac compromise to diagnose structural and/or functional cardiac abnormalities.

●Ultrasound may be useful for diagnosis of pulmonary, cardiac, and abdominal causes of respiratory distress and can be performed to detect a limited number of conditions (eg, pneumothorax, pericardial effusion) at the bedside to expedite diagnosis and care.

•Pulmonary ultrasound can diagnose pneumothorax, pleural effusion, hemothorax, pneumonia, and pulmonary edema and can facilitate the timely performance of needle thoracostomy for tension pneumothorax and/or placement of a pigtail catheter or chest tube to decompress pneumothorax, pleural effusion, and hemothorax. (See "Community-acquired pneumonia in children: Clinical features and diagnosis", section on 'Other imaging techniques' and "Clinical presentation and diagnosis of pneumothorax", section on 'Diagnostic imaging'.)

•Cardiac ultrasound can identify cardiac structure and function, pericardial effusion, and cardiac tamponade and, when available, should be used to guide pericardiocentesis. (See "Trauma management: Approach to the unstable child", section on 'e-FAST (extended focused assessment with sonography for trauma)' and "Emergency pericardiocentesis", section on 'Ultrasound-guided pericardiocentesis technique'.)

•Abdominal ultrasound can identify free fluid, masses, appendicitis, intussusception, renal stone, and infectious processes that may cause respiratory compromise due to abdominal distension and/or pain that limit respiratory effort.

●Computed tomography (CT) or magnetic resonance imaging (MRI) of the neck, chest, or abdomen may be useful to diagnose intra- and extrathoracic structural abnormalities, masses, and vascular processes as discussed separately (see "Overview of common presenting signs and symptoms of childhood cancer" and "Emergency evaluation of the child with acute abdominal pain"). CT should be used judiciously to minimize radiation exposure.

Patients with a mediastinal mass are at risk for abrupt cardiorespiratory arrest when placed in the supine position. In most patients, definitive imaging should be delayed until appropriate airway management and specialized monitoring by an anesthesiologist or other experienced provider with similar skills can be arranged during imaging.

DIAGNOSTIC APPROACH — Stabilization precedes the diagnostic evaluation in the child with acute respiratory distress. The diagnostic approach to the causes of acute respiratory distress in children is based upon clinical findings (algorithm 1 and algorithm 5).

Upper airway disease — The diagnostic approach to upper airway disease is described in detail separately (algorithm 5). (See "Emergency evaluation of acute upper airway obstruction in children".)

Lower airway disease — The physical examination provides a working differential diagnosis for children with lower airway disease and nonpulmonary causes of respiratory distress (algorithm 1). In selected patients, the suspected diagnosis should be confirmed by appropriate studies. (See 'Ancillary studies' above.)

Trauma — Injured children with respiratory distress may have sustained serious thoracic injury. Evaluation and treatment should be in accordance with advanced trauma life support guidelines (table 7) (see "Trauma management: Approach to the unstable child"). Bedside ultrasound to diagnosis pulmonary, cardiac, and abdominal trauma can expedite diagnosis and management of life-threatening conditions. The initial stabilization and evaluation of thoracic trauma in children is discussed in detail separately. (See "Thoracic trauma in children: Initial stabilization and evaluation".)

No trauma — Diagnosis of nontraumatic lower airway processes can be guided by breath sounds, cardiac examination, and the presence or absence of fever as follows:

Wheezes and/or crackles with fever — The presence of wheezes and/or rales with fever is consistent with infectious processes:

●Pneumonia – Focal crackles are typical findings in children with bacterial pneumonia. These breath sounds are often transmitted throughout the chest of a small child, which may mask focality. Asymmetric and decreased breath sounds with dullness to percussion suggest empyema or a pleural effusion. Diffuse crackles and/or wheezing suggest viral or atypical pneumonia. However, the absence of crackles or wheezes does not exclude the diagnosis of pneumonia.

Chest radiographs often establish the diagnosis of pneumonia, although findings may be subtle or absent in patients with a short duration of illness and infiltrates may be difficult to distinguish from atelectasis. (See "Community-acquired pneumonia in children: Clinical features and diagnosis", section on 'Clinical evaluation' and "Community-acquired pneumonia in children: Clinical features and diagnosis", section on 'Radiologic evaluation'.)

●Bronchiolitis – Bronchiolitis occurs primarily in infants younger than two years of age. Typical clinical features include fever, nasal congestion, increased secretions, and retractions with diffuse wheezing and scattered crackles. Chest radiograph is not recommended for diagnosis and should only be obtained if there are clinical findings suggestive of other potential diagnoses or in patients with bronchiolitis and moderate to severe respiratory distress. (See "Bronchiolitis in infants and children: Clinical features and diagnosis", section on 'Clinical features'.)

●Asthma with a febrile illness – A child with asthma who has fever and wheezing most commonly has a viral illness. If hypoxemia is also present, then they may have pneumonia or atelectasis. Upper respiratory tract infections, which do not generally cause respiratory distress (eg, the common cold), may trigger an asthma exacerbation in children. A chest radiograph to evaluate for pneumonia may be helpful for patients with an asthma exacerbation, fever, and focal breath sounds that do not resolve with treatment. (See "Trigger control to enhance asthma management", section on 'Respiratory infections' and "Acute asthma exacerbations in children younger than 12 years: Emergency department management", section on 'Indications for chest radiograph'.)

●Foreign body – Pneumonia may develop around or distal to an aspirated foreign body, and foreign body should be suspected in patients with fever, focal wheeze, and/or crackles. It should also be suspected in patients with chronic cough, recurrent dyspnea, wheezing, or pneumonia. (See "Airway foreign bodies in children", section on 'Delayed diagnosis'.)

●Myocarditis with heart failure – Children with viral myocarditis may have fever and respiratory distress due to compromised cardiac function. Coxsackie B is the most common cause of myocarditis in children. COVID-19 infection and COVID-19 RNA vaccination have also been associated with myocarditis in children. (See "COVID-19: Multisystem inflammatory syndrome in children (MIS-C) clinical features, evaluation, and diagnosis" and "COVID-19: Vaccines", section on 'Myocarditis'.)

Tachypnea may be the only respiratory indication of myocarditis. Crackles suggest pulmonary edema. Tachycardia with or without respiratory findings, particularly if unresponsive to fluids, should increase the suspicion for myocarditis. A new cardiac murmur or gallop may also be present. Elevated troponin and characteristic findings on electrocardiogram and echocardiograph help confirm the diagnosis. (See "Clinical manifestations and diagnosis of myocarditis in children", section on 'Clinical manifestations'.)

Wheezes and/or crackles without fever — The etiology of respiratory distress in afebrile children with wheezes and/or crackles may be infectious or noninfectious, and, while most commonly intrapulmonary, may arise from cardiac or mediastinal conditions (see "Evaluation of wheezing in infants and children"):

●Asthma – Asthma is the most common cause of respiratory distress and wheezing in afebrile children. Children with severe symptoms should receive aggressive pharmacologic therapy as well as evaluation for associated conditions, including pneumothorax or pneumonia as clinically indicated. (See "Acute asthma exacerbations in children younger than 12 years: Emergency department management".)

●Bronchiolitis – Although commonly associated with wheezing and fever, children with bronchiolitis may be afebrile. (See "Bronchiolitis in infants and children: Clinical features and diagnosis", section on 'Clinical features'.)

●Anaphylaxis – Anaphylaxis can cause bronchospasm as well as upper airway obstruction. Exposure to a known trigger, facial edema, and an urticarial rash are common features. The treatment of anaphylaxis is detailed in the table and discussed separately (table 8). (See "Anaphylaxis: Emergency treatment".)

●Chronic pulmonary disease exacerbation – Children who are experiencing an exacerbation of a chronic pulmonary disease, such as bronchopulmonary dysplasia or cystic fibrosis, often have respiratory distress with abnormal breath sounds, such as wheezes or rales, along with increased cough and changes in sputum.

●Foreign body – Although breath sounds are classically asymmetric with foreign body in the lower airway, breath sounds may be symmetric because the foreign body is small and/or because breath sounds are transmitted across the chest of small children. Bilateral decubitus or inspiratory and forced expiratory chest radiographs may identify hyperaeration distal to the obstructing foreign body (image 8). If chest radiographs are equivocal, further evaluation depends upon the level of clinical suspicion (algorithm 4). (See "Airway foreign bodies in children", section on 'Suspected foreign body aspiration'.)

●Mediastinal mass – An intrathoracic mass such as a tumor, hemangioma, bronchogenic cyst, or enlarged lymph node that compresses the airway can result in wheeze and/or cough. Chest radiography typically identifies this diagnosis. Further evaluation of a mediastinal mass in children is discussed separately. (See "Overview of common presenting signs and symptoms of childhood cancer", section on 'Mediastinal masses'.)

●Heart failure – Children in respiratory distress from heart failure classically have rales on lung exam as well as other signs of heart disease, such as abnormal heart sounds, edema (periorbital in infants and pretibial in older children and adolescents), and organomegaly. Electrocardiogram, chest radiograph, and echocardiography help to confirm the diagnosis in patients with suggestive clinical findings. (See "Cardiac causes of cyanosis in the newborn", section on 'Left-sided obstructive lesions' and "Heart failure in children: Etiology, clinical manifestations, and diagnosis", section on 'Diagnostic evaluation'.)

●Pulmonary edema – Noncardiogenic pulmonary edema is a rare finding in children. Causes including upper airway obstruction, severe central nervous system (CNS) insult, submersion injury, acute salicylate toxicity, and pulmonary irritants. (See "Noncardiogenic pulmonary edema".)

●Atypical pneumonia – Atypical pneumonia is most commonly due to mycoplasma species in school-age children and Chlamydia species in infants born to infected mothers. Patients with atypical pneumonia typically have a dry or staccato cough. These patients may also have nasal congestion, conjunctivitis (chlamydia infection), shortness of breath, chest tightness, rales, and wheezes (mycoplasma infection). Fever may or may not be present. (See "Mycoplasma pneumoniae infection in children", section on 'Clinical manifestations' and "Pneumonia caused by Chlamydia pneumoniae in children", section on 'Clinical features'.)

●Atelectasis – The physical findings of atelectasis in children tend to be minimal since areas of non-atelectatic lung may expand to fill space left by atelectasis obscuring decreased or absent breath sounds in the atelectatic lung. In most cases, there are no changes in the physical examination, although occasionally fever may be present. Crackles and/or wheezes may be heard over areas of obstructive atelectasis if the airway obstruction is incomplete and allows some airflow. (See "Atelectasis in children", section on 'Chest examination'.)

Tachypnea with fever — In patients without wheeze or crackles, tachypnea may be the only indicator of respiratory distress, particularly in those younger than six months of age. The presence of fever suggests an infectious etiology within or outside the respiratory system, such as:

●Pneumonia – Breath sounds may be normal with lobar pneumonia or empyema, particularly in small children. Etiology may be bacterial or viral. Decreased pulse oximetry or abnormalities on chest radiographs help to establish the diagnosis. (See "Community-acquired pneumonia in children: Clinical features and diagnosis", section on 'Diagnosis'.)

●COVID-19 – COVID-19/severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) should also be considered in acutely ill children, particularly in regions with a high prevalence or for children with known exposure. In addition to fever and tachypnea, respiratory symptoms may include 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. Findings typical of other viral respiratory infections (eg, hyperinflation, peribronchial markings) are unusual. (See "COVID-19: Clinical manifestations and diagnosis in children", section on 'Severe disease in children'.)

●Atelectasis – Atelectasis is not uncommon in ill or injured patients who are less mobile than usual or not breathing as deeply. In febrile children with respiratory compromise, atelectasis may be difficult to distinguish from bacterial pneumonia on bedside ultrasound or chest radiograph.

●Sepsis – Respiratory distress manifested as tachypnea may occur in patients with severe sepsis to compensate for metabolic acidosis. Respiratory status may be further compromised by decreased cardiac output and/or pulmonary capillary leak. (See "Sepsis in children: Definitions, epidemiology, clinical manifestations, and diagnosis", section on 'Clinical manifestations'.)

●Encephalitis or meningitis – Patients with encephalitis may have respiratory depression or tachypnea. Those with meningitis may have respiratory depression with or without signs of distress.

●Pulmonary tuberculosis – Although rare in developed countries, worldwide tuberculosis is common in children. Clinical findings are nonspecific. Cough present for more than three weeks and not improving, fever >38°C for more than two weeks, night sweats, and weight loss or failure to thrive should raise suspicion, especially in children with known exposure and/or who live in endemic environments. Intrathoracic adenopathy on chest radiograph is the most common radiographic finding and may be present without clinical findings in exposed children. (See "Tuberculosis disease in children: Epidemiology, clinical manifestations, and diagnosis".)

Tachypnea without fever — In afebrile patients with tachypnea, viral or mycoplasma pneumonia and noninfectious etiologies should be suspected:

●Viral or mycoplasma pneumonia – Pneumonia due to viral pathogens or mycoplasma can present with tachypnea alone but is usually associated with cough. SARS-CoV-2 can also present with tachypnea without fever as well as hypoxemia, shortness of breath, chest pain, and/or cough as respiratory findings. (See "Community-acquired pneumonia in children: Clinical features and diagnosis", section on 'Clues to etiology' and "Mycoplasma pneumoniae infection in children", section on 'Clinical manifestations'.)

●Pulmonary irritant – Inhaled biological or chemical agents or smoke from fire can cause irritation and/or inflammation that results in tachypnea. Agents of biologic warfare, particularly nerve gases, often impact children first because these gases are heavier than air, and thus more concentrated at the level at which children breathe, and because children breathe more rapidly than adults. (See "Chemical terrorism: Rapid recognition and initial medical management".)

●Intrapulmonary mass – Children with a tumor, bronchogenic cyst, or congenital diaphragmatic hernia may present with isolated tachypnea as an initial or later finding. Patients with chest mass may also present with pleural effusion, which may be bilateral.

●Spontaneous pneumothorax – Risk factors for spontaneous pneumothorax include tall, thin body habitus or high intrapulmonary pressure generated by smoking drugs, particularly marijuana. Clinical findings include chest pain, decreased breath sounds on the affected side, and hyperresonance to percussion. Bedside ultrasound can be useful for prompt diagnosis. In stable patients, an upright chest radiograph also supports clinical findings. (See "Spontaneous pneumothorax in children", section on 'Clinical features' and "Clinical presentation and diagnosis of pneumothorax", section on 'Diagnostic imaging'.)

●Pulmonary embolism – Pulmonary embolism classically causes respiratory distress with chest pain. Fever and hypoxia are often but not always present. Pulmonary embolism is rare in children, occurring most commonly in adolescents. Risk factors for pulmonary embolism include surgery, trauma, immobility, obesity, pregnancy, central vascular access devices, an underlying inherited or acquired hypercoagulable condition, heart, kidney or autoimmune disease, disseminated intravascular coagulation, malignancy, COVID-19, and medications, most notably oral contraceptives containing estrogen. (See "Venous thrombosis and thromboembolism (VTE) in children: Risk factors, clinical manifestations, and diagnosis", section on 'Clinical manifestations'.)

●Cardiac disease – Tachypnea with normal breath sounds and no fever may be a sign of cardiac disease. Cardiac conditions that cause heart failure include congenital structural lesions, arrhythmias, myocarditis, and pericardial effusion. Heart sounds often are abnormal but can be normal depending upon the underlying cardiac condition. Pain as the result of pericarditis may result in splinting with respiration. Cardiac biomarkers (eg, troponin), electrocardiogram, and, in selected settings, echocardiography can be helpful in establishing a specific diagnosis. (See "Cardiac causes of cyanosis in the newborn", section on 'Left-sided obstructive lesions' and "Clinical manifestations and diagnosis of myocarditis in children" and "Clinical features and diagnosis of supraventricular tachycardia (SVT) in children", section on 'Heart failure' and "Cardiac tamponade".)

●Metabolic derangement, endocrine disorder, and hemoglobin abnormality – Tachypnea and/or an abnormal respiratory pattern may occur as a compensatory response to metabolic acidosis (as in shock, diabetic ketoacidosis, or inborn error of metabolism), CNS stimulation (as with hyperammonemia), abnormalities associated with hemoglobin (ie, severe anemia, carboxyhemoglobin, or methemoglobin), conditions that increase metabolic rate (ie, hyperthyroidism or fever), splinting from pain, or a thoracic mass or deformity. (See "Urea cycle disorders: Clinical features and diagnosis", section on 'Clinical features' and "Approach to the child with metabolic acidosis".)

DIFFERENTIAL DIAGNOSIS — The differential diagnosis of acute respiratory distress in children is discussed in more detail separately (table 9). (See "Causes of acute respiratory distress in children".)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Airway management in children".)

SUMMARY AND RECOMMENDATIONS

●Rapid assessment – In children, respiratory distress is typically characterized by signs of increased work of breathing, such as tachypnea, use of accessory muscles, nasal flaring, and/or retractions. Head bobbing and grunting are additional signs more commonly seen in infants and young children. A respiratory rate that is inappropriately slow for the child's age and clinical condition may also be a sign of respiratory distress and impending respiratory arrest (table 1). (See 'Rapid assessment' above.)

●Initial stabilization – Respiratory distress in children must be promptly recognized and treated. Delay may result in respiratory failure, cardiopulmonary arrest, and death. Airway management in patients with signs of impending respiratory failure should be initiated prior to full evaluation. Initial management should focus on rapid patient assessment and support of airway, breathing, and circulation as described above. (See 'Initial stabilization' above.)

●Emergency conditions – Several conditions that cause acute respiratory distress require immediate, life-saving interventions as described in the table and discussed in detail separately (table 2):

•Acute upper airway obstruction (see "Emergency evaluation of acute upper airway obstruction in children" and "The difficult pediatric airway for emergency medicine")

•Tension pneumothorax (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')

•Impending respiratory arrest (see "Technique of emergency endotracheal intubation in children" and "Rapid sequence intubation (RSI) in children for emergency medicine: Approach")

•Acute cardiac tamponade (see "Emergency pericardiocentesis" and "Causes of acute respiratory distress in children", section on 'Cardiac tamponade')

●Evaluation – In children with respiratory distress, features of the history and physical examination will ideally localize the source as well as suggest the etiology and direct initial treatment (table 4). Ancillary studies can then be performed as indicated to confirm the diagnosis and guide management (table 5). (See 'Evaluation' above.)

The clinical features and evaluation of specific conditions that cause acute respiratory distress in children (table 9) are discussed separately. (See "Causes of acute respiratory distress in children".)

●Diagnostic approach – The diagnostic approach to the causes of acute respiratory distress in children is based upon clinical findings (algorithm 1 and algorithm 5). (See 'Diagnostic approach' above and "Emergency evaluation of acute upper airway obstruction in children".)