Dr. Mieno and colleagues have presented a well-written and interesting article (see page 1960) concerning other potential benefits derived from lung volume reduction surgery (LVRS) besides improvement in dyspnea and pulmonary function test results. Prior to accepting the conclusion of any study, its methodology must be critically scrutinized and questioned.
The study by Mieno and colleagues is retrospective cohort study that spans a 4-year period. This lengthy time frame lends itself to treatment bias. It may introduce some biases since treatment strategies can change, but it is unlikely that many significant changes were made.