<prompt> All the following are true regarding COPD EXCEPTIncreased residual volumeIncreased total lung capacityDecreased residual volumetotal lung capacity ratioDecreased vital capacity  <response>: Ans. c Decreased residual volumetotal lung capacity ratio Ref. H-16,hpg. no. 1542-47 ; Table 242-1COPD Pulmonary function testing shows airflow obstruction with a reduction in FEV and FEVFVC. With worsening disease severity, lung volumes may increase, resulting in an increase in total lung capacity, functional residual capacity, and residual volume. In emphysema, the diffusing capacity may be reduced, reflecting the parenchymal destruction. Degree of airflow obstruction is imp prognostic factor in COPD and is the basis for GOLD disease classification. Computed tomography HRCT scan is the current definitive test for establishing the presence or absence of emphysema.Gold criteria for copd severityGold StageSeveritySymptomsSpirometry0At riskChronic cough, sputum productionNormalIMildWith or without chronic cough or sputum production predictedFEV1FVC 0.7 and FEV1 80IIAModerateWith or without chronic cough or sputum production 80 predictedFEV1FVC 0.7 and 50 FEV1IIISevereWith or without chronic cough or sputum production 50 predictedFEV1FVC 0.7 and 30FEV1IVVery severeWith or without chronic cough or sputum production predicted or FEV1 50 predicted with respiratory failure or signs of RHFFEV1FVC 0.7 and FEV1 30Clinical Correlation: Changes in lung Compliance ComplianceEmphysema Less elastic recoil of lungs, so FRC Chest wall expands and becomes barrel-shaped Also, RV, TLC,FVC, RawComplianceFibrosis, respiratory distress syndrome Tendency of lungs to collapse, so FRC Also, TLC, RV, FVC 