Cough results from stimulation of irritant receptors in the airway mucosa. Acute cough generally is associated with respiratory infections or irritant exposure (smoke) and subsides as the infection resolves or the exposure is eliminated. The characteristics of the cough and the circumstances under which the cough occurs help in determining the cause. Sudden onset after a choking episode suggests foreign body aspiration. Morning cough may be due to the accumulation of excessive secretions during the night from sinusitis, allergic rhinitis, or bronchial infection. Nighttime coughing is a hallmark of asthma and can also be caused by gastroesophageal reflux disease. Cough exacerbated by lying flat may be due to postnasal drip, sinusitis, allergic rhinitis, or reflux. Recurrent coughing with exercise is suggestive of exercise-induced asthma/bronchospasm. Paroxysmal cough suggests pertussis or foreign body aspiration. A repetitive, staccato cough occurs in chlamydial infections in infants. A harsh, brassy, seal-like cough suggests croup, tracheomalacia, or psychogenic (habit) cough. The last, which is most common in teenagers, disappears during sleep. Younger children can develop a throat-clearing habit cough, which also disappears during sleep.
Chronic cough is defined as a daily cough lasting longer than 3 weeks. Common causes of chronic cough are asthma, postnasal drip (allergic rhinitis, sinusitis), and postinfectious tussive syndromes. It can also be caused by gastroesophageal reflux disease, swallowing dysfunction (infants), anatomic abnormalities (tracheoesophageal fistula, tracheomalacia), and chronic infection. Persistent cough may also be caused by exposure to irritants (tobacco and wood stove smoke) or foreign body aspiration, or it may be psychogenic in origin.
During the first several years of life, children experience frequent viral respiratory infections, especially if they have multiple older siblings or attend day care or preschool. Cough that resolves promptly and is clearly associated with a viral infection does not require further diagnostic workup. However, cough persisting longer than 3 weeks warrants further evaluation.
Chest radiographs are useful in assessing respiratory disease in children. In addition to determining lung abnormalities, they provide information about the bony thorax (rib or vertebral abnormalities), the heart (cardiomegaly, pericardial effusion), and the great vessels (right aortic arch/vascular rings, rib notching). Chest radiographs should be obtained in both the posteroanterior (PA) and lateral projections and, if possible, following a full inspiration. Estimation of lung hyperinflation based on a single PA view is unreliable; flattened diaphragms and an increased AP diameter on lateral projection is a better indicator of hyperinflation. Crowding of the blood vessels with poor inspiration can be misinterpreted as increased markings or infiltrates. External skin folds, rotation, and motion may produce distorted or unclear images. Expiratory views and fluoroscopy may detect partial bronchial obstruction due to an aspirated foreign body that results in regional hyperinflation, because the affected lung or lobe does not deflate on exhalation. Fluoroscopy can also be used to evaluate diaphragm movement.
A barium esophagram may be valuable in diagnosing disorders of swallowing (dysphagia) and esophageal motility, vascular rings (esophageal compression), tracheoesophageal fistulas, and, to a lesser extent, gastroesophageal reflux. When evaluating for a tracheoesophageal fistula, contrast material must be instilled under pressure via a catheter with the distal tip situated in the esophagus (see Chapter 128).