Effects of non-intubation anesthesia based on a fentanyl-reduced regimen on hypoxemia during bronchoscopy for older patients: study protocol for a randomized controlled trial - Xie, An; Zhang, Xianjie; Han, Jia; Zhou, Rui (Journal of Thoracic Disease; Vol 17, No 7 (July 31, 2025): Journal of Thoracic Disease, 2025)