True about obstructive lung disease is -

(A) Decrease FEV, and FEV1/FVC) (2158-H 18th, (673 - Davidson 21st)* Hall mark of COPD is air flow obstruction (Reduction in FEV, and FEV1/FVC)* 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,<80%predicted3.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 units/lOmmHg 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.