Monday, March 14, 2011

Cough and Sputum Production

Cough and Sputum Production

A cough is a sudden, usually involuntary, expulsion of air from the lungs with a characteristic and easily recognizable sound. Although it is known as the most common symptom of respiratory disorders, it serves the functions of defending the respiratory tract against noxious substances and maintaining airway patency by removing excessive secretions from the air passages. Expectoration or sputum production is the act of coughing up and spitting out the material produced in the respiratory tract.

Clinical Significance

As a cardinal manifestation of respiratory diseases, coughing is one of the most common symptoms encountered in clinical medicine. Being a physiologic reflex, the cough also occurs without any demonstrable evidence of disease when triggered by the stimulation of the irritant receptors. Moreover, it may be a voluntary act or may result from nervous habit. Although the clinical significance of coughing in many instances is trivial, it may be an indication of a serious intrathoracic disease. Pathologic conditions causing the cough are usually the ones that irritate the airways, increase their irritability, result in their deformation, or increase the tracheobronchial secretions. These factors may operate singly or in various combinations. Sputum production with coughing occurs when the respiratory tract secretions are beyond the ability of the mucociliary mechanism to deal with them.

The most common cause of the acute cough of clinical significance is viral tracheobronchitis. The cough in this transient and self-limited condition is, at the beginning, nonproductive and quite annoying; later it becomes productive of mucous or mucopurulent sputum before it begins to subside. Inflammation of the respiratory tract mucosa, from infectious or noninfectious causes, results in hyper-reactivity of the cough receptors. This results from the alteration of the surface epithelium, making them more sensitive to the cough-producing effect of commonly occurring mild irritants such as cold air, respiratory pollutants, deep or fast respiration, and excessive use of the larynx. At times, the mechanical irritation of coughing itself brings about more coughing. Inflammation, in addition, increases the secretions. In acute viral respiratory tract infection, post-nasal drip may be another cause for triggering the cough. Other infectious, as well as noninfectious, diseases of upper or lower respiratory tract are known for their propensity in causing the cough as a part of their clinical

Anatomic Classification of Causes of Cough.
A chronic cough, defined as a cough lasting for a minimum duration of 3 weeks, is usually indicative of structural changes in the respiratory tract or the persistence of other cough-stimulating factors. By far the most common cause of a chronic cough in developed nations is tobacco smoking, which is the most important factor in the etiology of chronic bronchitis. In this disease, the cough is productive of a fairly large amount of sputum that varies from mucous to mucopurulent. Patients with chronic bronchitis, well accustomed and often oblivious to their symptoms, become concerned when the characteristics of their cough and sputum production change. The most frequent cause for the change is the intercurrence of an infection; however, it may indicate the occurrence of a neoplasm.
Since the decline of tuberculosis in developed nations, lung cancer has become most feared among the people with a chronic cough. The cough in lung cancer may develop de novo when there is no underlying chronic bronchitis and may be its only manifestation. As chronic bronchitis and lung cancer are very uncommon among nonsmokers, a chronic persistent cough has a different significance in this population. Airway hyperreactivity, the hallmark of bronchial asthma, is a rather common condition in which the cough may be the predominant or even the sole manifestation. Patients with hyperreactive airways, without other manifestations of asthma, may have a chronic cough for as long as several years until the condition is suspected, accurately diagnosed, and properly treated. Chronic postnasal drip, a frequent symptom of allergic or nonallergic rhinitis and/or sinusitis, is implicated in many instances of a chronic cough. A sensation of secretions dripping down into the throat and the feeling of a need to clear the throat are very suggestive of this disorder.
The chronic cough may be a manifestation of many other pathologic conditions involving the intra- and extrathoracic organs . Left-sided heart failure not only results in a cough with acute pulmonary edema but also may be a cause of a chronic nocturnal cough. Recurrent aspiration is another condition in which the cough characteristically occurs in a supine position. Foreign-body aspiration should always be considered in the differential diagnosis of the chronic cough. After the initial coughing or choking episode at the time of its aspiration, the cough may restart and continue long after the incident. Other, less common intraluminal or compressing lesions of the tracheobronchial tree, chronic inflammatory or fibrosing lung diseases, and extrapulmonary lesions may have cough as their predominant symptom. Tumors of the mediastinum, enlarged heart chambers, and pleural disease may manifest with cough. A psychogenic or intentional cough for personal gain should be seriously considered only when other causes are properly excluded. The angiotensin-converting enzyme inhibitors such as captopril and enalapril, used for the treatment of hypertension and congestive heart failure, are being increasingly recognized as a cause of a dry, annoying, and often incessant cough, which disappears only after the discontinuation of these agents.
Characteristics of expectorated sputum often suggest the diagnosis of its cause. Chronic expectoration of large amounts of purulent and foul-smelling sputum is strongly suggestive of bronchiectasis. Sudden production of such a sputum in a febrile patient indicates a lung abscess. Rust-colored purulent sputum in pneumococcal pneumonia, currant jelly and sticky sputum in klebsiella pneumonia, and blood-tinged foamy sputum in pulmonary edema are other examples in which the diagnosis of the underlying disease is strongly suggested.

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