People with COPD may have different types of inflammation that can be identified by measuring immune cells (for example, neutrophils or eosinophils) or proteins in sputum or different measures in exhaled air (FeNO). Recent improved understanding of these inflammation subtypes helps providers and drug developers target the best treatment approach.   In most people with COPD, the most common type of inflammation is neutrophilic inflammation, especially people who are or were smokers. But 20–40% have Type 2 inflammation that is associated with high eosinophils.[12] In clinical trials, people with higher eosinophil levels responded better to treatment with inhaled steroids.[13]