Title {1}	Effect of post-extubation high-flow nasal cannula combined with respiratory training versus conventional oxygen therapy on postoperative pulmonary complications in patients after major abdominal surgery: protocol for a single-centre randomized controlled trial
Trial registration {2a and 2b}.	ChiCTR2100047146. Registered on 8 June 2021. http://www.chictr.org.cn/index.aspx
Protocol version {3}	Version 1 of 14–04-2021
Funding {4}	The trial is supported by “The Seventh Affiliated Hospital, Sun Yat-sen University Clinical Research 735 Program”.
Author details {5a}	Department of Intensive Care, The Seventh Affiliated Hospital,Sun Yet-sen University, ShenZhen, China.
Name and contact information for the trial sponsor {5b}	Liang Luo, Department of Intensive Care, The Seventh Affiliated Hospital, Sun Yet-sen University, ShenZhen, China. luoliang@mail.sysu.edu.cn
Role of sponsor {5c}	Liang Luo all contributed to the design and management of the study protocol.