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

Abstract

This study investigated the effect of 92% oxygen administration on 2-back task performance, blood oxygen saturation (SpO(2) [%]), 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. SpO(2) 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 SpO(2) during the Task phase. This showed that due to sufficient oxygen supply necessary for cognitive processing, SpO(2) 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.