If there's peripheral cyanosis due to peripheral vascular disease and central cyanosis due to heart disease simultaneously how to know each cause?

Combination . Various testing and history and exams. Blue babies are generally central. Some older persons have blocked vessels, bad lungs, and other signs and symptoms. A rare person will have both and several causes: congestive heart failure, smoker- COPD, atherosclerosis and DVT etc. One needs to evaluate multi system.