When you breathe, your lungs take in oxygen from the air and deliver it to the bloodstream. The cells in your body need oxygen to work and grow. During a normal day, you breathe nearly 25,000 times. People with lung disease have difficulty breathing. Millions of people in the U.S. have lung disease. If all types of lung disease are lumped together, it is the number three killer in the United States. The term lung disease refers to many disorders affecting the lungs, such as asthma , chronic obstructive pulmonary disease , infections like influenza , pneumonia and tuberculosis , lung cancer , and many other breathing problems .