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LEARNING OBJECTIVES

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  1. Accurately identify the most likely etiology of a cough, through history, diagnostic tests, and appropriate patient findings on physical examination to enable the appropriate recommendation of effective treatment or referral to an appropriate provider.

  2. Use the knowledge of the pathophysiology, etiology, and usual presentation of common diseases with cough as a primary symptom to review prescription orders for appropriateness and to accurately educate patients about their disease and its treatment.

  3. Use the knowledge of the pathophysiology, etiology, and usual presentation of diseases with cough as a primary symptom to accurately interpret the diagnostic process to advise regarding the most appropriate prescription therapy.

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A cough is a natural protective process. Normal, healthy school-aged children experience 10 to 12 coughing episodes per day. Coughing has two main functions: (1) clearing the larynx, trachea, and bronchi of inhaled material, mucous, infectious agents, noxious substances, foreign particles, edema fluid, and pus and (2) increasing oxygenation in the blood via post-cough inspiration and breathing. These mechanisms are thought to partially contribute to the cough of exercise-induced asthma and the early morning cough typical of asthma.

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Mechanical and chemical cough receptors are located primarily in the epithelium of the upper and lower respiratory tracts, but are also found in the esophagus, diaphragm, stomach, and pericardium. When irritated, they initiate a reflex arc via the vagus nerve to the cough center in the medulla, which then causes a reflex arc via the vagus, phrenic and spinal motor nerves to initiate a four-step process. First, there is an inspiratory phase, followed by a forced expiratory phase against a closed glottis to build up intrathoracic pressure. Second, the glottis opens with rapid expiration and causes the cough sound, followed by a deep inspiration. Prolonged or violent coughing can cause vomiting, fractured ribs, muscle spasm, urinary incontinence, and syncope.

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ETIOLOGY

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The causes of a cough are numerous and can be due to disorders of the upper respiratory, lower respiratory, gastrointestinal, or cardiovascular systems. Viral upper respiratory infections, allergic rhinitis, and bacterial sinusitis all produce cough as an associated symptom, probably due to post-nasal drip of mucoid or purulent material. The lower respiratory tract is the primary source of cough as a symptom. Infections can be caused by viruses (acute bronchitis, viral pneumonia, and influenza), bacteria (pneumonia, tuberculosis, and whooping cough), or fungi (histoplasmosis, coccidioidomycosis, and candida). Inflammatory conditions of the lungs leading to cough include asthma, COPD, and smoking. Drug-induced pulmonary adverse effects also have cough as a major symptom complex. Gastroesophageal reflux disease (GERD) is an important gastrointestinal cause of cough. Various malignancies involving the respiratory tract may also present with a cough as the primary symptom. Finally, congestive heart failure is the most common cause of cough due to disorders of the cardiovascular system.

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DIAGNOSIS

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The diagnosis of the cause of a cough is complex and requires a careful ...

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