Pulmonary hypeension in COPD is due to -

pulmonary hypeension in COPD is Category 3. Pulmonary hypeension associated with hypoxemic lung disease Key feature: chronic hypoxia with mild elevation of PAP Includes: * Chronic obstructive lung disease * Interstitial lung disease * Sleep-disordered breathing * Alveolar hypoventilation disorders * Chronic exposure to high altitude * Developmental abnormalities ref:Harrison&;s principles of internal medicine,ed 18,pg no 2078