What Is Cough?

Cough is a reflex to remove mucus and other material from the airways that is triggered by stimulation of receptors located between the pharynx and terminal bronchioles. Afferent signals from cough receptors are sent via the vagus and glossopharyngeal nerves to the cough centers in the brainstem and pons. Efferent signals travel through the vagus, phrenic, and spinal motor nerves to the larynx, diaphragm, and muscles of the chest wall, abdomen, and pelvic floor.

What Causes Acute Cough?

In children, acute cough (< 3 weeks) is usually the result of infection. Most of these are viral upper respiratory illnesses. The cough from a viral respiratory illness usually improves within 1 week. Asthma is the next most common cause of cough, but distinguishing between asthma and viral respiratory infections can be difficult initially because exacerbations of asthma in children are often associated with upper respiratory infections. Bronchiolitis or bronchopneumonia from respiratory syncytial virus and other viruses tends to occur in seasonal epidemics and affects young infants most severely. Bacterial pneumonias in infants and children are less common than viral infections, and the patient with bacterial pneumonia usually appears more ill and has crackles, higher fever, and more tachypnea.

What Causes Chronic Cough?

Chronic cough persists for more than 3 weeks in children (Table 25-1). Asthma is the most common cause. Many of these children will have chronic asthma, but even intermittent asthmatic patients can have a lingering cough from an acute exacerbation of asthma that lasts longer than 3 weeks. Infectious etiologies include bacterial or viral pneumonias, although most pneumonias cause acute cough. Both Bordetella pertussis (whooping cough) and Mycoplasma pneumonia (walking pneumonia) are particularly well known for causing cough that can last for more than 2 months. A history of exposure to adults who have chronic cough may suggest these two infections.

Table 25-1 Causes of Chronic Cough in Children

What Are Key History and Examination Findings?

Table 25-2 lists pertinent history and physical examination findings for common causes of cough in children.

Table 25-2 History and Physical Examination in the Evaluation of Cough