<prompt> True about obstructive lung disease is -Decreased FEV1 and FEV1FVCFEV1FVC normal or increasedDecreases RVDecrease total lung capacity  <response>: A Decrease FEV, and FEV1FVC 2158-H 18th, 673 - Davidson 21st Hall mark of COPD is air flow obstruction Reduction in FEV, and FEV1FVC Lung volume may increase, resulting in an increase in total lung capacity TLC, functional residual capacity FRC and residual volume RV. More recently it has been shown that a multifunctional index incorporating airflow obstruction - exercise performance, dyspnea, and body mass index is a better predictive of mortality rate than pulmonary function alone.Gold criteria for COPD severity1.MildFEV1 FEV 0.7 and FEV 80 predicted2.ModerateFEV1 FVC 0.7 and 50 FEV,80predicted3.SevereFEV1 FVC 0.7 and 30 FEV,50 predicted4.Very severeFEV1 FVC 0.7 and FEV, 30 predictedorFEV1 50 predicted with respiratory failure or signs of right heart failure. The change in pH with PCO2 is 0.08 unitslOmmHg actively and 0.03 units lOmmHg in the chronic state. Increase hematocrit suggests the presence of chronic hypoxemia as does the presence of signs of right ventricular hypertrophy. CT scan is the current definitive test for establishing the presence or absence of emphysema in living subjects. Recent guidelines have suggested testing for a a,AT deficiency in all subjects with COPD or asthma with chronic airflow obstruction. 