{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,13]],"date-time":"2026-02-13T17:00:16Z","timestamp":1771002016853,"version":"3.50.1"},"reference-count":61,"publisher":"American Physiological Society","issue":"10","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Journal of Applied Physiology"],"published-print":{"date-parts":[[2014,11,15]]},"abstract":"<jats:p> Chronic fatigue syndrome (CFS) with orthostatic intolerance is characterized by neurocognitive deficits and impaired working memory, concentration, and information processing. In CFS, upright tilting [head-up tilt (HUT)] caused decreased cerebral blood flow velocity (CBFv) related to hyperventilation\/hypocapnia and impaired cerebral autoregulation; increasing orthostatic stress resulted in decreased neurocognition. We loaded the baroreflex with phenylephrine to prevent hyperventilation and performed n-back neurocognition testing in 11 control subjects and 15 CFS patients. HUT caused a significant increase in heart rate (109.4 \u00b1 3.9 vs. 77.2 \u00b1 1.6 beats\/min, P &lt; 0.05) and respiratory rate (20.9 \u00b1 1.7 vs. 14.2 \u00b1 1.2 breaths\/min, P &lt; 0.05) and decrease in end-tidal CO<jats:sub>2<\/jats:sub> (ETCO<jats:sub>2<\/jats:sub>; 42.8 \u00b1 1.2 vs. 33.9 \u00b1 1.1 Torr, P &lt; 0.05) in CFS vs. control. HUT caused CBFv to decrease 8.7% in control subjects but fell 22.5% in CFS. In CFS, phenylephrine prevented the HUT-induced hyperventilation\/hypocapnia and the significant drop in CBFv with HUT (\u22128.1% vs. \u221222.5% untreated). There was no difference in control subject n-back normalized response time (nRT) comparing supine to HUT (106.1 \u00b1 6.9 vs. 97.6 \u00b1 7.1 ms at n = 4), and no difference comparing control to CFS while supine (97.1 \u00b1 7.1 vs 96.5 \u00b1 3.9 ms at n = 4). However, HUT of CFS subjects caused a significant increase in nRT (148.0 \u00b1 9.3 vs. 96.4 \u00b1 6.0 ms at n = 4) compared with supine. Phenylephrine significantly reduced the HUT-induced increase in nRT in CFS to levels similar to supine (114.6 \u00b1 7.1 vs. 114.6 \u00b1 9.3 ms at n = 4). Compared with control subjects, CFS subjects are more sensitive both to orthostatic challenge and to baroreflex\/chemoreflex-mediated interventions. Increasing blood pressure with phenylephrine can alter CBFv. In CFS subjects, mitigation of the HUT-induced CBFv decrease with phenylephrine has a beneficial effect on n-back outcome. <\/jats:p>","DOI":"10.1152\/japplphysiol.00527.2014","type":"journal-article","created":{"date-parts":[[2014,10,2]],"date-time":"2014-10-02T22:38:37Z","timestamp":1412289517000},"page":"1157-1164","source":"Crossref","is-referenced-by-count":22,"title":["Phenylephrine alteration of cerebral blood flow during orthostasis: effect on <i>n<\/i>-back performance in chronic fatigue syndrome"],"prefix":"10.1152","volume":"117","author":[{"given":"Marvin S.","family":"Medow","sequence":"first","affiliation":[{"name":"Department of Pediatrics, New York Medical College, Valhalla, New York; and"},{"name":"Department of Physiology, New York Medical College, Valhalla, New York"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Shilpa","family":"Sood","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, New York Medical College, Valhalla, New 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