Chronic obstructive pulmonary disease other diagnostic studies
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Chronic obstructive pulmonary disease Microchapters |
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Differentiating Chronic obstructive pulmonary disease from other Diseases |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Philip Marcus, M.D., M.P.H. [2]; Associate Editor(s)-In-Chief: Cafer Zorkun, M.D., Ph.D. [3]
Overview
Chronic obstructive pulmonary disease (COPD), also known as chronic obstructive airway disease (COAD), is a group of diseases characterized by the pathological limitation of airflow in the airway that is not fully reversible [1]. COPD is the umbrella term for chronic bronchitis, emphysema and a range of other lung disorders. It is most often due to tobacco smoking,[2] but can be due to other airborne irritants such as coal dust, asbestos or solvents, congenital conditions such as alpha-1-antitrypsin deficiency and as well as preserved meats containing nitrites.
Diagnosis
Spirometry
The diagnosis of COPD is confirmed by spirometry,[3] a test that measures the forced expiratory volume in one second (FEV1), which is the greatest volume of air that can be breathed out in the first second of a large breath. Spirometry also measures the forced vital capacity (FVC), which is the greatest volume of air that can be breathed out in a whole large breath. Normally, at least 70% of the FVC comes out in the first second (i.e. the FEV1/FVC ratio is >70%). A ratio less than normal defines the patient as having COPD. More specifically, the diagnosis of COPD is made when the FEV1/FVC ratio is <70%. The GOLD criteria also require that values are after bronchodilator medication has been given to make the diagnosis, and the NICE criteria also require FEV1%. According to the ERS criteria, it is FEV1% predicted that defines when a patient has COPD, that is, when FEV1% predicted is < 88% for men, or < 89% for women.
Spirometry can help to determine the severity of COPD.[3] The FEV1 (measured after bronchodilator medication) is expressed as a percentage of a predicted "normal" value based on a person's age, gender, height and weight:
| Severity of COPD (GOLD scale) | FEV1 % predicted |
|---|---|
| Mild (GOLD 1) | ≥80 |
| Moderate (GOLD 2) | 50–79 |
| Severe (GOLD 3) | 30–49 |
| Very severe (GOLD 4) | <30 or chronic respiratory failure symptoms |
The severity of COPD also depends on the severity of dyspnea and exercise limitation. These and other factors can be combined with spirometry results to obtain a COPD severity score that takes multiple dimensions of the disease into account.[4]
Other tests
On chest x-ray, the classic signs of COPD are overexpanded lung (hyperinflation), a flattened diaphragm, increased retrosternal airspace, and bullae.[5] It can be useful to help exclude other lung diseases, such as pneumonia, pulmonary edema or a pneumothorax.[5] Complete pulmonary function tests with measurements of lung volumes and gas transfer may also show hyperinflation and can discriminate between COPD with emphysema and COPD without emphysema. A high-resolution computed tomography scan of the chest may show the distribution of emphysema throughout the lungs and can also be useful to exclude other lung diseases.
A blood sample taken from an artery, i.e. Arterial Blood Gas (ABG), can be tested for blood gas levels which may show low oxygen (hypoxaemia) and/or high carbon dioxide (respiratory acidosis if pH is also decreased). A blood sample taken from a vein may show a high blood count (reactive polycythemia), a reaction to long-term hypoxemia.
References
- ↑ Mannino DM, Homa DM, Akinbami LJ, Ford ES, Redd SC (2002). "Chronic obstructive pulmonary disease surveillance--United States, 1971-2000". MMWR. Surveillance Summaries : Morbidity and Mortality Weekly Report. Surveillance Summaries / CDC. 51 (6): 1–16. PMID 12198919. Unknown parameter
|month=ignored (help);|access-date=requires|url=(help) - ↑ Devereux G. ABC of chronic obstructive pulmonary disease. Definition, epidemiology, and risk factors. BMJ 2006;332:1142-1144. PMID 16690673
- ↑ 3.0 3.1 Rabe KF, Hurd S, Anzueto A, Barnes PJ, Buist SA, Calverley P, Fukuchi Y, Jenkins C, Rodriguez-Roisin R, van Weel C, Zielinski J (2007). "Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease: GOLD executive summary". American Journal of Respiratory and Critical Care Medicine. 176 (6): 532–55. doi:10.1164/rccm.200703-456SO. PMID 17507545. Retrieved 2012-03-02. Unknown parameter
|month=ignored (help) - ↑ Celli BR, Cote CG, Marin JM; et al. (2004). "The body-mass index, airflow obstruction, dyspnea, and exercise capacity index in chronic obstructive pulmonary disease". N. Engl. J. Med. 350 (10): 1005–12. doi:10.1056/NEJMoa021322. PMID 14999112. Unknown parameter
|month=ignored (help) - ↑ 5.0 5.1 Torres M, Moayedi S (2007). "Evaluation of the acutely dyspneic elderly patient". Clin. Geriatr. Med. 23 (2): 307–25, vi. doi:10.1016/j.cger.2007.01.007. PMID 17462519. Unknown parameter
|month=ignored (help)