Respiratory Distress

Published on 06/06/2015 by admin

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Last modified 06/06/2015

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3 Respiratory Distress

Respiratory distress is defined as an alteration in the normal biomechanical and physiologic mechanisms of respiration. Respiratory distress is manifested by complaints of difficulty breathing and a variety of findings on physical examination showing increased respiratory effort. The degree of these findings can vary from mild to severe. Respiratory distress is one of the most common conditions for which children present for acute care. In contrast to adults, children experience significant morbidity and mortality as a result of respiratory conditions because of their different anatomy and physiology as well as decreased pulmonary reserve. Rapid assessment and appropriate management of children with respiratory distress is imperative, given that patients who cannot be adequately managed in the acute setting may progress to acute cardiopulmonary failure and ultimately death.

Etiology and Pathogenesis

The main function of the respiratory system is to supply sufficient oxygen to meet metabolic demands and to remove carbon dioxide. A variety of processes, including ventilation (gas delivery to and from the lungs), perfusion (amount of venous blood brought to the pulmonary bed), and diffusion (the movement of gases across the alveolar membrane), are involved in tissue oxygenation and carbon dioxide removal. Abnormalities in any one of these mechanisms, including hypoventilation, diffusion impairment, intrapulmonary shunt (when alveoli are perfused but not ventilated), and ventilation/perfusion mismatch (a disparity between gas delivery and pulmonary venous blood delivery), can lead to respiratory failure.

Respiratory distress can either be a manifestation of a primary respiratory problem or a secondary effect resulting from the disruption of another organ system. The pathogenesis and resultant signs and symptoms are directly linked to the underlying cause. In general, causes of respiratory distress may be classified as involving (1) the airway; (2) the lungs, chest wall, or both; (3) the central nervous system (CNS) respiratory drive or control; or (4) the neuromuscular system. Alternatively, the respiratory system may be compromised by dysfunction in other organ systems (i.e., cardiovascular, gastrointestinal, endocrine, hematologic) that affect respiratory function or trigger respiratory compensatory mechanisms.

Observed manifestations of distress reflect attempts by the patient to address the underlying inadequacies of their current respiratory status. Several core principles can explain these manifestations depending on the underlying cause:

Clinical Presentation

Treatment attempted Respiratory symptoms Systemic or associated symptoms Past medical history Exposures or environmental factors Trauma Immunization status Last oral intake

Physical Examination

Vital Signs

Vital signs, including temperature, heart rate, blood pressure, respiratory rate, and pain score, should be promptly obtained in all patients with respiratory distress. Pulse oximetry, although not classically part of the vital signs, should also be noted to detect hypoxia. Tachypnea (rapid breathing) is one of the most consistent findings among children with respiratory distress and may be caused by fever, hypoxemia, hypercarbia, metabolic acidosis, pain, or anxiety (Table 3-2). However, many children with significant respiratory disease may have normal respiratory rates. Bradypnea may also occur in response to hypoxia in younger infants or from respiratory fatigue, CNS depression, or increased intracranial pressure. Pulsus paradoxus, an exaggeration of the normal decrease in blood pressure during inspiration, of greater than 10 mm Hg correlates well with the degree of airway obstruction but is very difficult to assess in children and therefore not routinely measured.

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