Working memory impacts endurance for dyspnea

Background: Exertional dyspnea is the primary symptom that limits exercise in patients with chronic lung diseases. Dyspnea is an unpleasant emotion and controlled by the prefrontal cortex of the brain. Repeated dyspnea during daily living is memorized as painful on the working memory of the prefrontal cortex. The purpose of this study is to examine the relationship between increasing dyspnea and brain activities of emotion and working memory in healthy people. Methods: This study was a prospective observational study. 26 healthy males performed three breath-holding tests. During breath-holding tests, subjects were measured oxyhemoglobin (oxy-Hb) value by functional near-infrared spectroscopy (fNIRS). The breath-holding test was symptom-limited and measured holding time and dyspnea. Dyspnea was measured by Borg scale. The fNIRS measured oxy-Hb value of brain regions of emotion and working memory. Result: The maximum dyspneas during three breath-holding tests were 7.4 sec (first), 7.7 sec (second), and 7.6 sec (third). Breath-holding time increased significantly with each repetition (37.8±16.1 sec, 41.3±15.7, 47.6±22.4, p<0.05). Oxy-Hb of emotion at maximum dyspnea increased significantly all three tests compared with no dyspnea. The Oxy-Hb (0.20±0.23 mMmm) of emotion at the third test was significantly lower than the first value (0.40±0.30 mMmm). Oxy-Hb of working memory related significantly Oxy-Hb of emotion at every three tests. Working memory at maximum dyspnea related significantly to breath-holding times (r= -0.49, p<0.05). Conclusion: Increasing dyspnea amplified the brain activities of emotion and working memory. Decreasing brain activity of working memory impacts higher endurance for dyspnea.