Changes of 2-back task performance and physiological signals in ADHD children due to transient increase in oxygen level

This study investigated the effect of 92% oxygen administration on 2-back task performance, blood oxygen saturation (SpO2 [%]), and heart rate (HR [bpm]) of Attention Deficit Hyperactivity Disorder (ADHD) children. Subjects were thirteen boys (mean 12.9 ± 1.3 years) who were diagnosed as ADHD and are under treatment, having no disease or abnormality in a respiratory system or a periphery vascular flow system. The experiment consisted of two runs: one was a 2-back task under normal air (21% oxygen) condition and the other under hyperoxic air (92% oxygen) condition. The experiment sequence in each run consisted of three phases, which included the Adaptation phase (1 min) after oxygen administration, the Control phase (2 min) that maintained a stable condition before the task, and the Task phase (2 min) that performed 2-back task. SpO2 and HR were measured during each phase. The analysis of cognitive performance with 92% oxygen administration when compared to 21% oxygen revealed that the response time decreased. When 92% oxygen in the air was supplied, the blood oxygen saturation increased while the heart rate decreased compared to those under the 21% oxygen condition. The response time also decreased for the subjects with a high SpO2 during the Task phase. This showed that due to sufficient oxygen supply necessary for cognitive processing, SpO2 increased and heart rate decreased. Therefore, an increase in cognitive ability such as a decrease in response time was observed in a transient period for ADHD children.

► Highly concentrated oxygen induced the reduction of response time in ADHD children.
► Highly concentrated oxygen induced an increase in blood oxygen saturation for ADHD.
► Highly concentrated oxygen induced a decrease in heart rate for ADHD.
► ADHD children with high blood oxygen saturation showed a shorter response time.