What Are the Common Pathophysiology of COPD Exacerbations?

I was curious if you might have an operational definition for what constitutes an exacerbation to you. And then kind of a follow up to that would be if there's a common pathophysiology that we should be familiar with in regards to those exacerbations. What I've been telling patients is that if they have a change from their baseline of shortness of breath, cough or sputum, then you know, they're having an acute exacerbation of COPD. The gold guidelines allow stratification of COPD by, you know, greater than or equal to two exacerbations a year or one hospitalization.