The study is designed to develop models to predict site of collapse information using routine polysomnography. In an observational study, the investigators will study 1000 patients with obstructive sleep apnea (OSA) who have had a recent polysomnographic study and will undergo drug-induced sleep endoscopy (DISE) as part of their standard clinical care. Flow shape information from the polysomnographic study will be associated with the DISE results, and a set of prediction models will be developed and validated to detect the site, pattern and degree of upper airway collapse as seen during DISE.