Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) COPD ?
    ### Response:
    COPD (chronic obstructive pulmonary disease) makes it hard for you to breathe. The two main types are chronic bronchitis and emphysema. The main cause of COPD is long-term exposure to substances that irritate and damage the lungs. This is usually cigarette smoke.
    