Oxygen administration is recommended for patients with hypoxemia to achieve a target S pO2 range. Strategies to achieve this in clinical practice are suboptimal. We investigated automatic oxygen titration using a novel nasal high-flow device with closed-loop oxygen control. The objective of this proof-of-concept study was to determine whether closed-loop control was able to respond to desaturation and subsequent recovery in a controlled laboratory-based environment. We conducted a single-blind

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... andomized crossover trial in adults with chronic respiratory disease who had a resting S pO2 ≥ 92% and desaturated to < 90% during a 6-min walk test (6MWT). Nasal high-flow was administered during a 6MWT and a subsequent 10-min rest period with either room air, a fixed concentration of 28% oxygen, or oxygen titrated automatically using closed-loop control. The study involved 42 subjects. Closed-loop control maintained S pO2 within the target range of 92-96% for a mean (SD) duration of 54.4 ± 30.1% of the 6MWT and 67.3 ± 26.8% of the recovery period. The proportion of time spent with an S pO2 in the target range during the 6MWT was significantly greater for closed-loop control compared to room air, with a difference of 26.0% (95% CI 17.7-34.2, P < .001); this proportion of time was not significantly different compared to the fixed concentration of 28% oxygen, with a difference of -8.2% (95% CI -16.5 to 0.1, P = .052). The proportion of time spent in the target range during the rest period was significantly greater compared to 28% oxygen, with a difference of 19.3% (95% CI 8.9-29.7, P < .001); this proportion of time was not significantly different compared to room air, with a difference of -9.3% (95% CI -19.7 to 1.0, P = .08). This study provides proof-of-concept evidence that the novel nasal high-flow device with closed-loop control can respond to changes in S pO2 outside a target saturation range using a model of exercise-induced desaturation and subsequent recovery.