LUNG CAPACITY CHANGE? In my previous post I talked a little bit about how I perceived that my breathing changed just hours after taking my first round of Trikafta. Was it all placebo effect? Maybe. However, my FEV1 (a measure of lung capacity) did go up a whole 1% since my previous appointment one month ago. Whether or not this was due to my increased effort in blowing, or simply because of my increased dedication to my breathing treatments is unknown.