Respiratory distress is one of the most common reasons for a child to present to the emergency department or a practitioner’s office. Respiratory distress can result from disorders in the respiratory system or in organ systems that control or influence respiration. Young children have an increased risk for respiratory distress because of their anatomy and physiology. Nearly 20% of all emergency department visits for children younger than 2 years are for respiratory disease.¹ The causes of respiratory distress are vast, and practitioners caring for children should have a systematic approach to its diagnosis and management. Cardiopulmonary arrest in children is largely due to respiratory failure (in adults, cardiac causes are most common). Rapid evaluation and management of severe pediatric respiratory disease may be necessary to prevent respiratory failure.

Understanding respiratory physiology can aid the practitioner in diagnosing the cause of respiratory symptoms. The main goals of respiration are oxygen uptake and elimination of carbon dioxide. Secondary goals include acid–base buffering, hormonal regulation, and host defense. To achieve the goals of respiration, three main functional components of the respiratory system are used: (1) mechanical structures (including chest wall, respiratory muscles, and pulmonary circulation), (2) membrane gas exchanger (interface between airspace and pulmonary circulation), and (3) regulatory system (network of chemical and mechanical sensors throughout the circulatory and respiratory systems). All three components are tightly integrated, and dysfunction of one can lead to respiratory distress or failure.

Respiratory function is tightly controlled by a complex network of central and peripheral chemoreceptors and mechanoreceptors responding to information from the body about the status of the respiratory system. This network modulates the neural output to the respiratory muscles, affecting the timing and force of respiratory effort. Central chemoreceptors in the ventral reticular nuclei of the medulla are sensitive to changes in pH and partial pressure of carbon dioxide (PCO₂) of cerebrospinal fluid. The intrinsic brain-stem function of the dorsal and ventral respiratory centers of the medulla controls inspiration and expiration, respectively. The apneustic center in the pons increases the depth and duration of inspiration, whereas the pneumotaxic center decreases depth and duration. The cerebellum, hypothalamus, motor cerebral cortex, and limbic system also play a role in mediating respiration. Carotid and aortic bodies are peripheral chemoreceptors sensitive to the partial pressure of oxygen (PO₂), PCO₂, and pH in arterial blood. Mechanoreceptors (stretch, juxtacapillary, and irritant reflex) distributed along the airways, lung parenchyma, and chest wall respond to lung volume, changes in pulmonary microvasculature, chest wall muscle activity, and environmental irritants.

Information from central and peripheral receptors is integrated in the brainstem, and efferent impulses are transmitted to alter respiratory function and maintain homeostasis. Even slight alterations in arterial pH, PO₂, or PCO₂ stimulate the respiratory centers to modify the respiratory pattern. Increased arterial PCO₂ and decreased arterial PO₂ lead to an increase in respiratory drive and increased neural output to respiratory muscles. The resulting increase in ventilation can be achieved by increases in tidal volume or respiratory rate, because the product of these two factors determines the minute ventilation. Respiratory insufficiency or the more severe entity, respiratory failure, occurs when regulatory systems or the effector organs (lungs, respiratory muscles) are impaired or overwhelmed. This results in diminished oxygenation (decreased arterial PO₂), retention of carbon dioxide (increased arterial PCO₂), and acidosis (decreased arterial pH).

Disruption of the mechanics of the lung or chest wall results in the majority of respiratory disease in children.² Obstructive or restrictive disease leads to increased work of breathing and increased energy demands on the respiratory muscles to meet the body’s needs. This increased work manifests itself clinically as respiratory distress, evidenced by increased work of breathing. When demand exceeds capability, the result is respiratory insufficiency, which can progress to respiratory failure. In respiratory muscle dysfunction, neural output is sent to the respiratory muscles but they are unable to respond adequately to increase respiratory effort. The physical signs of respiratory failure in this setting are more subtle, and the signs of increased work of breathing may not be present. When the difficulty involves the control of breathing, there is an inadequate neural response to hypoxemia or hypercarbia. Arterial hypoxemia or hypercarbia without an increase in respiratory effort should lead one to suspect an anomaly in the neural control of breathing caused by central nervous system injury, drug-induced inhibition, or dysfunction of spinal motor neurons or nerve fibers innervating the respiratory muscles.

The first priority in evaluating a child with respiratory distress is to assess the airway, breathing, and circulation (ABC’s). Rapid assessment and intervention can prevent the progression from respiratory compromise to respiratory failure. To assess the airway, determine whether it is patent, stable, and maintainable. If not, such an airway must be established (e.g. repositioning, instrumentation). Once these three criteria are met, the breathing process is evaluated by determining the respiratory rate, oxygen saturation, adequacy of breath sounds, and quality of respiratory effort (e.g. labored, use of accessory muscles). Determination of arterial blood gas levels may be needed if there is evidence of respiratory insufficiency or failure. If spontaneous ventilation is inadequate, assisted breathing with positive pressure, initially via a bag-mask device, is indicated. Assessment of the patient’s circulation and mental status are other key aspects of the initial evaluation. Based on this rapid assessment, the clinician obtains information about the severity of the patient’s condition and how rapidly interventions must be performed.

Providing supplemental oxygen is an important first step for a child presenting in distress, especially with hypoxemia demonstrated by oximetry. Oxygen can be delivered by multiple devices, and the choice depends on the child’s clinical status and oxygen needs (see Chapter 195). Some of these devices can agitate a child further, worsening respiratory compromise and increasing the metabolic demand for oxygen. Allow the child to remain with the parent as much as possible, and use the least noxious form of oxygen delivery necessary. In a small number of children, airway adjuncts such as a nasopharyngeal airway, oropharyngeal airway, or assisted ventilation are needed. An oropharyngeal airway holds the tongue forward to prevent airway obstruction, so it will not be tolerated in a conscious or semiconscious patient with an intact gag reflex, and it may induce vomiting. A nasopharyngeal airway can be used in a conscious or unconscious patient but should be avoided in those with facial trauma. Continuous positive airway pressure may assist inspiratory efforts as well as provide positive end-expiratory pressure (PEEP). PEEP provides resistance to expiration, which may help expand atelectatic portions of the lung and thereby reduce ventilation-perfusion mismatch. Bilevel positive airway pressure provides inspiratory and expiratory pressure via a firmly fitting facemask, which may be uncomfortable and not well tolerated in infants or young children (see Chapter 195).

Careful reevaluation after every intervention is critical to the care of a child with respiratory compromise. This confirms proper application of the intervention and monitors the patient’s response.

Therapeutic interventions in an ill child should not be delayed to perform a detailed history. A focused history includes an assessment of respiratory and systemic symptoms (Box 35-1). The history will guide the practitioner toward the diagnostic possibilities and appropriately focus the management. For children with special needs or chronic respiratory problems, ask about the child’s baseline respiratory status, how this episode is different, and what interventions have been successful in the past.