title: Cerebral and muscle deoxygenation, hypoxic ventilatory chemosensitivity and cerebrovascular responsiveness during incremental exercise.
abstract: To examine if cerebral (frontal cortex) and skeletal muscle (m. vastus lateralis) deoxygenation and cerebral blood flow velocity (V(mean)) in the middle cerebral artery differentiated between normoxic and hypoxic (end-tidal P(O)(2) 71 mmHg) conditions, and if they were associated with hypoxic ventilatory chemosensitivity and cerebrovascular responsiveness, 8 men performed incremental cycling trials (30W/min ramp) under normoxic (T1-N) and hypoxic (T1-H) conditions until volitional fatigue, or until arterial O2 saturation decreased below 80%. The tests were repeated (T2-N; T2-H) on another day with supplemental O2 (Sup-O2) at the end of exercise. The V(mean) response was similar in normoxia and hypoxia. In hypoxia compared to normoxia, cerebral deoxygenation ( upward arrow deoxyhemoglobin concentration (Delta[HHb]) and downward arrow tissue oxygenation index (TOI)) was greater at a given work rate. A strong hypoxic ventilatory chemosensitivity was associated with a rapid reduction of cerebral TOI (r=0.94, P<0.001). Muscle deoxygenation was similar in normoxia and hypoxia suggesting greater muscle blood flow in hypoxia compared to normoxia and thus the existence of control features that match muscle perfusion and O2 delivery tightly with O2 demand during exercise. Sup-O2 reduced both cerebral and muscle deoxygenation, at least transiently.
authors.affiliation: Unit for Sports and Exercise Medicine, Institute of Clinical Medicine, University of Helsinki, Paasikivenkatu 4, 00250 Helsinki, Finland. juha.peltonen@helsinki.fi
authors.forename: Juha E
authors.initials: JE
authors.lastname: Peltonen
authors.forename: Donald H
authors.initials: DH
authors.lastname: Paterson
authors.forename: J Kevin
authors.initials: JK
authors.lastname: Shoemaker
authors.forename: Darren S
authors.initials: DS
authors.lastname: Delorey
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Dumanoir
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Petrella
authors.forename: John M
authors.initials: JM
authors.lastname: Kowalchuk
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D002540:Cerebral Cortex / Q000098:blood supply / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D000860:Hypoxia / Q000473:pathology* / Q000503:physiopathology; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology; D018482:Muscle, Skeletal / Q000098:blood supply / Q000503:physiopathology*; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology; D012123:Pulmonary Ventilation / Q000502:physiology*; D012129:Respiratory Function Tests; D019265:Spectroscopy, Near-Infrared; D055815:Young Adult
chemical_list: D006454:Hemoglobins; D010100:Oxygen