Characteristic of obstructive pulmonary disease are all except: March 2007
Correct Answer: Reduced residual volume
Description: Ans. C: Reduced residual volume The diagnosis of COPD is confirmed by spirometry. Spirometry 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%). In COPD, FEV1 is reduced and hence FEV1/FVC ratio is less than normal, (i.e. FEV/FVC ratio is With worsening disease severity, lung volumes may increase resulting in an increase in total lung capacity, functional residual capacity and residual volume. In emphysema, diffusing capacity may be reduced, reflecting the parenchymal destruction characteristic of the disease. An x-ray of the chest may show an over-expanded lung (hyperinflation). A high-resolution computed tomography scan of the chest may show the distribution of emphysema throughout the lungs. A blood sample taken from an aery can be tested for blood gas levels which may show low oxygen levels (hypoxemia) and/or high carbon dioxide levels (respiratory acidosis). A blood sample taken from a vein may show a high blood count (reactive polythycaemia), a reaction to long-term hypoxemia.
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