 The other terms are compliance and resistance and a lot of times you'll hear that when we talk about some critical care topics and we'll get into those here. So compliance first is the ease of lung expansion. So it's basically the ability of the lungs to inflate and deflate and that's the lung elasticity and again that chest wall recoil. Now when we have decreased compliance then it's difficult to inflate the lungs and there can be several causes that cause that. So the lungs are not easily expanded if there's fluid in the lungs such as in pneumonia, pulmonary edema or ARDS. If there's decreased elasticity of the lungs so when now the arveoli are not as pliable if you want to call it that and easily open and close such as in pulmonary fibrosis we have problems with decreased compliance or when there's decreased lung movement when now the lungs can't expand because there's fluid sitting in that pleural cavity due to a pleural infusion for example. So these are all causes for decreased compliance but the compliance can also be increased and that would be the destruction of arveoli such as we see in patients with COPD and Pizema where the arveoli are hyperextended and so now that lung the arveoli is always kind of like hyperinflated and that would be increased compliance. And the other term here is resistance. So resistance is when there is airflow difficulty during inspiration and expiration due to a change in airway diameter. So this is when we think about bronchoconstriction when for example in asthma patients all this inflammation makes the airways constricted and then causing a problem with resistance. So then there's more resistance and more force needed to get the air into the lungs and that can cause some problems here because of that airway diameter. And just so you know the triangle here means change. It's a very commonly used abbreviation in the medical field. I know we don't see much handwriting anymore but it's a very easy way of saying change and it's just something that I've been using over the years and just so you know that that's what that means.