Effects of uvulopalatopharyngoplasty on sleep architecture and patterns of obstructed breathing. In this retrospective study, 72 obstructive sleep apnea patients with polysomnograms taken before and after uvulopalatopharyngoplasty were evaluated. Postoperatively, there was a significant improvement of sleep architecture and respiratory indices. In addition, a second group of 17 patients also had position recordings with their polysomnograms. Time spent in supine and lateral sleep positions changed postoperatively. There was significant decrease of the apnea plus hypopnea index in the lateral position. This study indicates that there is significant improvement of sleep architecture and respiratory indices in the majority of patients after uvulopalatopharyngoplasty, particularly in the lateral sleep position. 