title: Cardiovascular responses to dynamic exercise with acute anemia in humans.
abstract: We hypothesized that reducing arterial O2 content (CaO2) by lowering the hemoglobin concentration ([Hb]) would result in a higher blood flow, as observed with a low PO2, and maintenance of O2 delivery. Seven young healthy men were studied twice, at rest and during two-legged submaximal and peak dynamic knee extensor exercise in a control condition (mean control [Hb] 144 g/l) and after 1-1.5 liters of whole blood had been withdrawn and replaced with albumin [mean drop in [Hb] 29 g/l (range 19-38 g/l); low [Hb]]. Limb blood flow (LBF) was higher (P < 0.01) with low [Hb] during submaximal exercise (i.e., at 30 W, LBF was 2.5 +/- 0.1 and 3.0 +/- 0.1 l/min for control [Hb] and low [Hb], respectively; P < 0.01), resulting in a maintained O2 delivery and O2 uptake for a given workload. However, at peak exercise, LBF was unaltered (6.5 +/- 0.4 and 6.6 +/- 0.6 l/min for control [Hb] and low [Hb], respectively), which resulted in an 18% reduction in O2 delivery (P < 0.01). This occurred despite peak cardiac output in neither condition reaching >75% of maximal cardiac output (approximately 26 l/min). It is concluded that a low CaO2 induces an elevation in submaximal muscle blood flow and that O2 delivery to contracting muscles is tightly regulated.
authors.affiliation: The Copenhagen Muscle Research Center, Rigshospitalet, Denmark.
authors.forename: M D
authors.initials: MD
authors.lastname: Koskolou
authors.forename: R C
authors.initials: RC
authors.lastname: Roach
authors.forename: J A
authors.initials: JA
authors.lastname: Calbet
authors.forename: G
authors.initials: G
authors.lastname: Rådegran
authors.forename: B
authors.initials: B
authors.lastname: Saltin
mesh_terms: D000208:Acute Disease; D000328:Adult; D000740:Anemia / Q000097:blood / Q000503:physiopathology*; D002302:Cardiac Output / Q000502:physiology; D002319:Cardiovascular System / Q000503:physiopathology*; D015444:Exercise; D005268:Femoral Vein; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D007866:Leg / Q000098:blood supply; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology; D012039:Regional Blood Flow / Q000502:physiology
chemical_list: D006454:Hemoglobins; D010100:Oxygen