<prompt> Pulmonary hypeension in COPD is due to -Constriction of pulm vesselsHypoxiaInterstitial fibrosisBronchoconstriction  <response>: 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 