title: Blood volume and its relation to peak O(2) consumption and physical activity in patients with chronic fatigue.
abstract: Individuals with chronic fatigue syndrome (CFS) experience a number of somatic complaints including severe, disabling fatigue, and exercise intolerance. We hypothesized that hypovolemia, through its interaction with central hemodynamics, would contribute to the exercise intolerance associated with this disorder. We examined blood volume, peak aerobic power, habitual physical activity, fatigue level, and their interrelations to understand the physiological basis of this disorder. Seventeen patients who met the Centers for Disease Control criteria for CFS and 17 age-matched controls participated in the study. Blood volume was assessed using a single bolus injection of Evans blue dye. Peak oxygen consumption was measured during exercise on an upright cycle ergometer. Supine cardiac output and stroke volumes were measured using CO(2) rebreathing. Questionnaires were used to assess habitual physical activity and fatigue. Patients displayed a trend for a 9% lower blood volume (58.3 +/- 2.1 vs. 64.2 +/- 2.5 ml/kg, P = 0.084) and had a 35% lower peak oxygen consumption (22.0 +/- 1.2 vs. 33.6 +/- 1.9 ml/kg, P < 0.001). These two variables were highly related within the patients (r = 0.835, P < 0.001) and the controls (r = 0.850, P < 0.001). Peak ventilation and habitual physical activity were significantly lower in the patients. Fatigue level was not related to any of the measured physiological parameters within the CFS group. In conclusion, individuals with CFS have a significantly lower peak oxygen consumption and an insignificant trend toward lower blood volume compared with controls. These variables were highly related in both subject groups, indicating that blood volume is a strong physiological correlate of peak oxygen consumption in patients with CFS.
authors.affiliation: Center for Autonomic and Peripheral Nerve Disorders, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
authors.forename: William B
authors.initials: WB
authors.lastname: Farquhar
authors.forename: Brian E
authors.initials: BE
authors.lastname: Hunt
authors.forename: J Andrew
authors.initials: JA
authors.lastname: Taylor
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Darling
authors.forename: Roy
authors.initials: R
authors.lastname: Freeman
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001794:Blood Pressure; D001810:Blood Volume / Q000502:physiology*; D002302:Cardiac Output; D015444:Exercise / Q000502:physiology*; D005221:Fatigue / Q000503:physiopathology; D015673:Fatigue Syndrome, Chronic / Q000097:blood / Q000503:physiopathology*; D005260:Female; D006339:Heart Rate; D006400:Hematocrit; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D012016:Reference Values; D012720:Severity of Illness Index; D013318:Stroke Volume; D011795:Surveys and Questionnaires