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Chronic obstructive pulmonary disease: COPD

COPD is characterized by decreased maximal expiratory flow and delayed lung emptying which are fairly stable over a period of a few months. Flow limitation increases in time and is largely irreversible (see references). The most important pathological features are:

COPD is usually accompanied by chronic cough and phlegm, i.e. 3 months a year for at least two consecutive years. It is often also associated with some extent of bronchial hyperreactivity to various stimuli. There is usually only a minimal response to bronchodilator drugs. The physician is usually first consulted because of progressive dyspnea and chronic cough; the previous history often reveals wheezing, and particularly during the winter time there are repeated episodes of respiratory infections. Chronic cough is often productive and worse in the morning; sputum volume may increase during exacerbations, and it may be blood-streaked. Large volumes of sputum, particularly if purulent, are a feature of bronchiectasis.

Chronic bronchitis is accompanied by chronic hypersecretion, which in turn bears little relation to the presence of airflow limitation.
It may be difficult to differentiate COPD from persistent asthma in older subjects. A history of heavy smoking, radiological evidence of lung emphysema, chronic hypoxemia and diminished diffusing capacity are points in favor of COPD. Marked improvement in spirometric indices with administration of bronchodilators or corticosteroids, and atopy, favor the diagnosis of asthma.

The diagnosis is confirmed by a combination of clinical symptoms and evidence of airways obstruction, i.e. an abnormally low FEV1/FVC or preferably low FEV1/IVC ratio. The GOLD group intended to make life easier for physicians by adopting a fixed ratio of 0.7 as the lower limit of normal of the FEV1/FVC ratio at 0.7. Apart from the fact that all lung function equipment automatically generates a lower limit of normal, so that there is no need at all for a simple rule of thumb, adopting this fixed ratio as a lower limit leads to considerable overdiagnosis in those older than 45 years, because the lower limit is at 0.7 at that age and declines further with ageing. See also the Open Letter to the GOLD group and "The GOLD controversy". There is overwhelming evidence that a diagnosis of COPD based on the fixed ratio is not associated with mortality, hospitalisation, exacerbations, decreased qualityof life, etc.

References COPD
Apart from textbooks, consult these sources of information:
1 ERS Consensus statement. Optimal assessment and management of chronic obstructive pulmonary disease (COPD). Eur Respir J 1995; 8: 1398-1420.
2 ATS Statement. Standards for the diagnosis and care of patients with chronic obstructive pulmonary disease. Am J Respir Crit Care Med 1995; 152: S77-S120.
3 NHG-Standaard COPD (Derde herziening). Snoeck-Stroband JB, Schermer TRJ, Van Schayck CP, Muris JW, Van der Molen T, In ’t Veen JCCM, Chavannes NH, Broekhuizen BDL, Barnhoorn MJM, Smeele I, Geijer RMM, Tuut MK. Huisarts Wet 2015;58(4):198-211. Manuscript
4 BTS. Diagnosis and management of stable COPD. Thorax 1997; 52: S2-S15.
5 Quanjer PH, Ruppel G, Brusasco V, Pérez-Padilla R, Fragoso CA, Culver BH, Swanney MP, Miller MR, Thompson B, Morgan M, Hughes M, Graham BL, Pellegrino R, Enright P, Buist AS, Burney P. COPD (confusion over proper diagnosis) in the zone of maximum uncertainty. Eur Respir J 2015; 46(5): 1523-1524. Abstract
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