Simultaneous reduction of flow and fraction of inspired oxygen (FiO2) versus reduction of flow first or FiO2 first in patients ready to be weaned from high-flow nasal cannula oxygen therapy: study protocol for a randomized controlled trial (SLOWH trial)

Background High-flow nasal cannula (HFNC) oxygen therapy has been widely used in critically ill patients. Despite the effectiveness of HFNC as a treatment, optimal methods to withdraw HFNC after recovery from preexisting conditions have not been investigated to date. In this study, we will evaluate the safety and efficacy of simultaneous reduction of flow and fraction of inspired oxygen (FiO(2)) compared with sequential reduction of either flow first or FiO(2) reduction first in patients with HFNC. Methods/design This is a prospective, investigator-initiated, randomized controlled trial with three experimental intervention groups. A total of 100 adult patients receiving HFNC and satisfying weaning criteria will be enrolled and randomly assigned to one of the following groups: flow reduction (FR) first, FiO(2) reduction (OR) first, or simultaneous reduction (SR). In the FR group, flow will be reduced first by 10 L/min/h. When it reaches 20 L/min, FiO(2) will then be reduced by 0.1 /h until it reaches 0.3. In the OR group, the FiO(2) will be gradually reduced first by 0.1 /h until it reaches 0.3, then flow will be reduced by 10 L/min until it reaches 20 L/min. Finally, in the SR group, both the flow and FiO(2) will be gradually reduced simultaneously by 10 L/min and 0.1/h, respectively. Weaning will proceed only when patients satisfy the weaning criteria at every weaning point. When the HFNC weaning-off targets are reached (20 L/min and 0.3 for flow and FiO(2,) respectively), the patient will be transferred to conventional oxygen therapy (mainly low-flow nasal prongs). The primary outcome is the time to successful weaning from HFNC for 24 h. Secondary outcomes will include the success or failure rate in weaning off HFNC and changes in arterial blood gas analyses, intolerance rate, length of hospital stay, and in-hospital mortality. Discussion This study will be the first clinical trial to investigate the safety and efficacy of three different methods of weaning in adult patients receiving HFNC. Once this study is completed, we expect to be able to suggest the better strategy for withdrawal of HFNC based on the results.