David B. Burbulys, MD
A 6-month-old boy has been coughing and breathing fast for the past day. This morning he refused feeding and has been irritable. On examination, the infant is fussy. He has an oxygen saturation of 92%, a respiratory rate of 60 breaths per minute, a pulse of 140 beats per minute, and a normal blood pressure and temperature. Additionally, he has nasal flaring, intercostal and supraclavicular retractions, and occasional grunting.
1. What are the causes of respiratory distress in infants and children?
2. What are the signs and symptoms of respiratory distress in infants and children?
3. What are the signs and symptoms of impending respiratory failure in infants and children?
4. What are the critical interventions for infants and children in respiratory distress?
Respiratory distress and respiratory failure may cause significant morbidity and mortality in infants and children. The signs and symptoms of respiratory compromise may be subtle, particularly in small infants and early on. Decompensation may occur rapidly if ventilation or oxygenation is inadequate but may be prevented by prompt recognition and management. Respiratory distress is defined as increased work of breathing, and it usually precedes respiratory failure. Respiratory failure occurs when ventilation or oxygenation is insufficient to meet the metabolic demands of the tissues (ie, oxygenation of the blood is inadequate or carbon dioxide is not eliminated). Respiratory failure may be caused by diseases of the airway, inadequate gas exchange in the lungs, or poor respiratory effort (Box 70.1). Respiratory failure may result in cardiopulmonary arrest if not corrected promptly.
Primary care physicians frequently care for children in respiratory distress in offices and emergency departments. Respiratory distress remains the most common reason for hospital admission. Such admissions usually involve young infants with acute infections, such as bronchiolitis or croup. Reactive airways disease (eg, asthma) is a common reason for respiratory distress-related admission in older children.
Increases in respiratory rate and work of breathing are the most common signs of respiratory disease. Tachycardia is often present; the presence of bradycardia, however, may be an ominous sign of impending cardiopulmonary failure and arrest. Effortless tachypnea (ie, Kussmaul breathing) may be a sign of respiratory compensation for metabolic acidosis rather than an indication of pulmonary pathology. Similarly, hypoxia that does not improve with supplemental oxygen may be suggestive of a primary cardiac lesion. Signs of poor oxygenation include alterations in mental status, head bobbing, and change in skin color. Pallor, mottling, and cyanosis are often late signs of respiratory failure and shock. The child with severe hypoxemia may initially appear dusky or pale. If the child is anemic, cyanosis may not be evident even in the presence of low oxygen saturation (Box 70.2).
The adequacy of respiration depends on the ability to move an adequate volume of gas in and out of the airways as well as effective gas exchange of carbon dioxide and oxygen. Infants and children generally breathe with minimal effort. In very young children, the diaphragm and abdominal musculature are primarily used for ventilation, and the tidal volume is approximately 6 to 8 mL/kg. If the tidal volume is decreased because of obstruction, children compensate by increasing the respiratory rate, thus attempting to maintain adequate minute ventilation (minute ventilation = rate × tidal volume). If the minute ventilation remains insufficient for adequate gas exchange or the child can no longer sustain the increased work of breathing, respiratory failure ensues. Respiratory failure may then result in acidosis, myocardial dysfunction, and shock and may progress to complete cardiopulmonary arrest.
Infants and children are more prone than adults to respiratory distress because of the differences between their respiratory systems (Box 70.3).
The differential diagnosis of children with respiratory distress can include abnormalities with the pulmonary, cardiovascular, nervous, or metabolic systems. It is also important to make an initial differentiation between upper and lower airway disease based on the presence or absence of stridor, rhonchi, rales, or wheezes on examination. Many common causes are listed in Box 70.1.
Box 70.1. Common Causes of Respiratory Distress in Infants and Children
•Aspirated foreign body
•Airway anomalies or immaturity
•Reactive airways disease (eg, asthma)
•Congenital heart disease
•Congestive heart failure
•Pericarditis or tamponade
•Chest wall injury
•Pneumothorax, hemothorax, or pulmonary contusion
•Toxin exposure or ingestion
Box 70.2. Respiratory Distress
•Increased respiratory rate
•Inability to speak in sentences
•Changes in tidal volume or minute ventilation
•Presence of retractions: intercostal, substernal, diaphragmatic, or supraclavicular
•Changes in inspiratory-expiratory ratio
•Production of sounds with respiration (eg, grunting, gurgling, stridor, rhonchi, rales, wheezes)
•Decreased or absent breath sounds
•Presence of pale or cyanotic skin
•Presence of central cyanosis
•Alterations in mental status
A brief history should be obtained while concomitant physical examination proceeds and initial treatment is begun (Box 70.4).
Before a complete assessment can proceed, critical interventions that may change a child’s clinical status should be undertaken. The child should be placed in a position of comfort if possible, and oxygen should be applied. Ventilation and oxygenation should be assessed. Nasal and/or oropharyngeal suctioning should be done if necessary.
Box 70.3. Comparison of Respiratory Systems in Children and Adults
•The head in children is proportionally larger and has less muscular support.
•The tongue in children is larger in relation to the mouth, is poorly controlled, and can cause airway obstruction.
•The airway diameter is smaller in children and collapses easily. Reductions in size resulting from secretions or inflammation cause greater resistance to air flow (resistance is proportional to 1/radius4).
•The larynx is higher and more anterior in children and the epiglottis is floppy, which makes visualization of the vocal cords more difficult.
•The narrowest part of the airway in children is at the cricoid ring, unlike in adults, in whom the narrowest point is at the vocal cords.
•The trachea in children is short. In newborns it is 4 cm long; in 18-month-old infants, 7 cm long; and in adults, 12 cm long.
•The major muscle of respiration in children is the diaphragm. Any interference with diaphragmatic motion in young children impedes respiratory function. Intercostal muscles are immature in children and fatigue easily.
•Children have less pulmonary reserve and higher metabolic demands.
•Normal respiratory rates are higher in children and vary by age.