CHAPTER 70

Respiratory Distress

David B. Burbulys, MD

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.

Epidemiology

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.

Clinical Presentation

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).

Pathophysiology

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).

Differential Diagnosis

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.

Evaluation

History

A brief history should be obtained while concomitant physical examination proceeds and initial treatment is begun (Box 70.4).

Physical Examination

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.

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