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Chronic Obstructive Pulmonary Disease (COPD)

CHRONIC OBSTRUCTIVE PULMONARY DISEASE:

File:Copd versus healthy lung.jpgChronic obstructive pulmonary disease (COPD) refers to chronic bronchitisand emphysema, a pair of two commonly co-existing diseases of the lungs in which theairways become narrowed.[1] This leads to a limitation of the flow of air to and from the lungs causing shortness of breath. In contrast to asthma, the limitation of airflow is poorly reversible and usually gets progressively worse over time.

COPD is caused by noxious particles or gas, most commonly from tobacco smoking, which triggers an abnormal inflammatory response in the lung.[2][3] The inflammatory response in the larger airways is known as chronic bronchitis, which is diagnosed clinically when people regularly cough up sputum. In the alveoli, the inflammatory response causes destruction of the tissues of the lung, a process known as emphysema. The natural course of COPD is characterized by occasional sudden worsenings of symptoms called acute exacerbations, most of which are caused by infections or air pollution.

“Enlarged view of lung tissue showing the difference between healthy lung and COPD”.

The diagnosis of COPD requires lung function tests. Important management strategies are smoking cessationvaccinationsrehabilitation, and drug therapy (often usinginhalers). Some patients go on to requiring long-term oxygen therapy or lung transplantation.[2]

ü  Worldwide, COPD ranked sixth as the cause of death in 1990. It is projected to be the third leading cause of death worldwide by 2020 due to an increase in smoking rates and demographic changes in many countries.[2] COPD is the 4th leading cause of death in the U.S., and the economic burden of COPD in the U.S. in 2007 was $42.6 billion in health care costs and lost productivity.[4][5]

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Signs and symptoms

One of the most common symptoms of COPD is shortness of breath (dyspnea). People with COPD commonly describe this as: “My breathing requires effort,” “I feel out of breath,” or “I can’t get enough air in”.[6]People with COPD typically first notice dyspnea during vigorous exercise when the demands on the lungs are greatest. Over the years, dyspnea tends to get gradually worse so that it can occur during milder, everyday activities such as housework. In the advanced stages of COPD, dyspnea can become so bad that it occurs during rest and is constantly present.

Other symptoms of COPD are a persistent cough, sputum or mucus production, wheezing, chest tightness, and tiredness.[7][8]

File:Centrilobular emphysema 865 lores.jpgPeople with advanced (very severe) COPD sometimes develop respiratory failure. When this happens, cyanosis, a bluish discoloration of the lips caused by a lack of oxygen in the blood, can occur. An excess of carbon dioxide in the blood can cause headaches, drowsiness or twitching (asterixis). A complication of advanced COPD is cor pulmonale, a strain on the heart due to the extra work required by the heart to pump blood through the affected lungs.[9] Symptoms of cor pulmonale are peripheral edema, seen as swelling of the ankles, and dyspnea.

There are a few signs of COPD that a healthcare worker may detect although they can be seen in other diseases. Some people have COPD and have none of these signs. Common signs are:

  • tachypnea, a rapid breathing rate
  • wheezing sounds or crackles in the lungs heard through a stethoscope
  • breathing out taking a longer time than breathing in
  • enlargement of the chest, particularly the front-to-back distance (hyperinflation)
  • active use of muscles in the neck to help with breathing
  • breathing through pursed lips
  • increased anteroposterior to lateral ratio of the chest (i.e. barrel chest).

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Cause

Smoking
The primary risk factor for COPD is chronic tobacco smoking. In the United States, 80 to 90% of cases of COPD are due to smoking.[11][dead link][12] Exposure to cigarette smoke is measured in pack-years[13], the average number of packages of cigarettes smoked daily multiplied by the number of years of smoking. The likelihood of developing COPD increases with age and cumulative smoke exposure, and almost all life-long smokers will develop COPD, provided that smoking-related, extrapulmonary diseases (cardiovascular, diabetes, cancer) do not claim their lives beforehand. [14]
Occupational exposures
Intense and prolonged exposure to workplace dusts found in coal mining, gold mining, and the cotton textile industry and chemicals such as cadmium, isocyanates, and fumes from welding have been implicated in the development of airflow obstruction, even in nonsmokers.[15] Workers who smoke and are exposed to these particles and gases are even more likely to develop COPD. Intense silica dust exposure causessilicosis, a restrictive lung disease distinct from COPD; however, less intense silica dust exposures have been linked to a COPD-like condition.[16] The effect of occupational pollutants on the lungs appears to be substantially less important than the effect of cigarette smoking.[17]
Air pollution
Studies in many countries have found that people who live in large cities have a higher rate of COPD compared to people who live in rural areas.[18] Urban air pollution may be a contributing factor for COPD as it is thought to slow the normal growth of the lungs although the long-term research needed to confirm the link has not been done. In many developing countries indoor air pollution from cooking fire smoke (often usingbiomass fuels such as wood and animal dung) is a common cause of COPD, especially in women.[19]
Genetics
Some factor in addition to heavy smoke exposure is required for a person to develop COPD. This factor is probably a genetic susceptibility. COPD is more common among relatives of COPD patients who smoke than unrelated smokers.[20] The genetic differences that make some peoples’ lungs susceptible to the effects of tobacco smoke are mostly unknown. Alpha 1-antitrypsin deficiency is a genetic condition that is responsible for about 2% of cases of COPD. In this condition, the body does not make enough of a protein, alpha 1-antitrypsin. Alpha 1-antitrypsin protects the lungs from damage caused by protease enzymes, such as elastaseand trypsin, that can be released as a result of an inflammatory response to tobacco smoke.[21]
Other risk factors
A tendency to sudden airway constriction in response to inhaled irritants, bronchial hyperresponsiveness, is a characteristic of asthma. Many people with COPD also have this tendency. In COPD, the presence of bronchial hyperresponsiveness predicts a worse course of the disease.[17] It is not known if bronchial hyperresponsiveness is a cause or a consequence of COPD. Other risk factors such as repeated lung infectionand possibly a diet high in cured meats may be related to the development of COPD.

 

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Prognosis

COPD usually gradually gets worse over time and can lead to death. The rate at which it gets worse varies between individuals. The factors that predict a poorer prognosis are:[2]

  • Severe airflow obstruction (low FEV1)
  • Poor exercise capacity
  • Shortness of breath
  • Significantly underweight or overweight
  • Complications like respiratory failure or cor pulmonale
  • Continued smoking
  • Frequent acute exacerbations

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Footnotes

  1. ^ U.S. National Heart Lung and Blood Institute – What is COPD
  2. a b c d e f g h i j k l m Rabe KF, Hurd S, Anzueto A, et al. (2007). “Global Strategy for the Diagnosis, Management, and Prevention of Chronic Obstructive Pulmonary Disease: GOLD Executive Summary”. Am. J. Respir. Crit. Care Med. 176 (6): 532–55. doi:10.1164/rccm.200703-456SOPMID 17507545.
  3. ^ Hogg JC, Chu F, Utokaparch S, et al. (2004). “The Nature of Small-Airway Obstruction in Chronic Obstructive Pulmonary Disease”. New England Journal of Medicine 350 (26): 2645–53. doi:10.1056/NEJMoa032158PMID 15215480.
  4. ^ http://www.plosmedicine.org/article/info%3Adoi%2F10.1371%2Fjournal.pmed.0030442
  5. ^ COPD (Chronic Obstructive Pulmonary Disease)
  6. ^ “2007 NHLBI Morbidity and Mortality Chart Book” (PDF). Retrieved 2008-06-06.
  7. ^ Mahler DA (2006). “Mechanisms and measurement of dyspnea in chronic obstructive pulmonary disease”. Proceedings of the American Thoracic Society 3 (3): 234–8. doi:10.1513/pats.200509-103SFPMID 16636091.
  8. ^ U.S. National Heart Lung and Blood Institute – Signs and Symptoms

January 27, 2010 - Posted by | Blood, Cancers, Cells, Lungs, Muscles, Thyroid

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