Sunday, September 22, 2013

Cough and its management


Cough is the most frequent symptom of respiratory disease. It is caused by stimulation of sensory nerves in the mucosa of the pharynx, larynx, trachea and bronchi. Acute sensitisation of the normal cough reflex occurs in a number of conditions, and it is typically induced by changes in air temperature or exposure to irritants such as cigarette smoke or perfumes. The characteristics of cough originating at various levels of the respiratory tract are detailed in The explosive quality of a normal cough is lost in patients with respiratory muscle paralysis or vocal cord palsy. Paralysis of a single vocal cord gives rise to a prolonged, low-pitched, inefficient ‘bovine’ cough accompanied by hoarseness. Coexistence of an inspiratory noise (stridor) indicates partial obstruction of a major airway (e.g. laryngeal oedema, tracheal tumour, scarring, compression or inhaled foreign body) and requires urgent investigation and treatment. Sputum production is common in patients with acute or chronic cough, and its nature and appearance can provide clues to the aetiology

Causes of cough
Acute transient cough is most commonly caused by viral lower respiratory tract infection, post-nasal drip resulting from rhinitis or sinusitis, aspiration of a foreign body or throat-clearing secondary to laryngitis or pharyngitis. When it occurs in the context of more serious diseases such as pneumonia, aspiration, congestive heart failure or pulmonary embolism, it is usually easy to diagnose from other clinical features. Patients with chronic cough present more of a diagnostic challenge, especially when physical examination, chest X-ray and lung function studies are normal. In this context, it is most often explained by cough-variant asthma (where cough may be the principal or exclusive clinical manifestation), post-nasal drip secondary to nasal or sinus disease, or gastro-oesophageal reflux with aspiration. Diagnosis of the latter may require ambulatory pH monitoring or a prolonged trial of antireflux therapy . Between 10 and 15% of patients (particularly women) taking angiotensin-converting enzyme (ACE) inhibitors develop a drug-induced chronic cough. Bordetella pertussis infection in adults  can also result in protracted cough and should be suspected in those in close contact with children. While most patients with a bronchogenic carcinoma have an abnormal chest X-ray on presentation, fibreoptic bronchoscopy or thoracic CT is advisable in most adults (especially smokers) with otherwise unexplained cough of recent onset, as this may reveal a small endobronchial tumour or unexpected foreign body .In a small percentage of patients, dry cough may be the presenting feature of interstitial lung disease.