The investigators plan is to retrospectively evaluate spirometry on patients with severe asthma who have undergone bronchial thermoplasty. The procedure will have been done according to the recommended protocol of three separate sessions. For each patient all available spirometric data obtained before and after thermoplasty will be used. Data will be collected from two centers, OU Medical Center and St. Francis Hospital in Tulsa, OK. All procedures done at St. Francis have been performed by a single physician and he is providing their spirometric data for the investigators study. The following data will be collected for all participants undergoing bronchial thermoplasty: Age, height, sex, weight, medical history, smoking history, baseline spirometry before and after bronchodilators, post thermoplasty spirometry before and after bronchodilators.
