The Global Asthma Association (GAA) and the World Allergy Organization (WAO) recently issued statements stating that the small airway is caused by asthma and chronic obstructive pulmonary disease (COPD). Both pathogenesis and treatment play an important role. The small airway is an airway with diameter less than 2 mm and is one of the main sites where airflow obstruction occurs. Small particles (\<2 μm) and large particles are more likely to deposit in the distal airways, and have shown to have better effects on asthma and pulmonary obstruction. At the same time, real-life research has also shown that extra-fine particles provide better asthma control than large particles, and can better improve quality of life.The aim of the study is to compare the efficacy of asthma inhalers between extra-fine particles and non-extra-fine particles.
