Chronic obstructive pulmonary disease (COPD) is a chronic respiratory disease associated with tobacco smoking that represents a significant economic burden on the global health care system. COPD affects both developed and developing countries. In 2010, the number of COPD cases worldwide was approximately 384 million, representing a prevalence of 11.7%. COPD is predicted to become the third leading cause of death by 2020.

X-ray is an important test in diagnosing respiratory diseases. Through chest X-ray images combined with other tests and medical history, an accurate conclusion about the disease can be drawn.

To accurately assess the condition of the lungs or monitor the response to treatment in patients, doctors often use respiratory function measurements. This is one of the methods that uses a machine to measure the flow of air when the patient inhales and exhales to calculate many important lung function indicators.

Respiratory index is a typical parameter of the respiratory function test to see if the airway is good or not. In addition, it is also used as a basis for diagnosing diseases such as: chronic obstructive pulmonary disease, bronchial asthma, pulmonary fibrosis...