title: Effects of hyperoxia on the dynamics of skeletal muscle oxygenation at the onset of heavy-intensity exercise in patients with COPD.
abstract: This study addressed whether hyperoxia (HiOX=50% O2), compared to normoxia, would improve peripheral muscle oxygenation at the onset of supra-gas exchange threshold exercise in patients with chronic obstructive pulmonary disease (COPD) who were not overtly hypoxemic (resting Pa O₂> 60 mmHg ). Despite faster cardiac output and improved blood oxygenation, HiOX did not significantly change pulmonary O2 uptake kinetics ( VO₂p ). Surprisingly, however, HiOX was associated with faster fractional O2 extraction ( approximately Delta[deoxy-Hb+Mb] by near-infrared spectroscopy) (p<0.05). In addition, an "overshoot" in Delta[deoxy-Hb+Mb] was found after the initial fast response only in HiOX (7/11 patients) thereby suggesting impaired intra-muscular O2 delivery ( Q'O ₂mv)-to-utilization. These data indicate that, despite improved "central" O2 delivery, Q'O₂mv adapted at a slower rate than muscle VO₂ under HiOX in non-hypoxaemic patients with COPD. Our results question the rationale of using supplemental O2 to improve muscle oxygenation during the transition to high-intensity exercise in this patient sub-population.
authors.affiliation: Pulmonary Function and Clinical Exercise Physiology Unit (SEFICE), Division of Respiratory Diseases, Department of Medicine, Federal University of Sao Paulo (UNIFESP), Rua Professor Francisco de Castro 54, Vila Clementino, CEP: 04020-050 São Paulo, SP, Brazil.
authors.forename: Ana Cristina B
authors.initials: AC
authors.lastname: Siqueira
authors.forename: Audrey
authors.initials: A
authors.lastname: Borghi-Silva
authors.forename: Daniela M
authors.initials: DM
authors.lastname: Bravo
authors.forename: Eloara M V
authors.initials: EM
authors.lastname: Ferreira
authors.forename: Gaspar R
authors.initials: GR
authors.lastname: Chiappa
authors.forename: J Alberto
authors.initials: JA
authors.lastname: Neder
mesh_terms: D000368:Aged; D002302:Cardiac Output / Q000502:physiology; D005081:Exercise Therapy / Q000379:methods*; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D006931:Hyperbaric Oxygenation; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology*; D010101:Oxygen Consumption / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology / Q000628:therapy*; D011659:Pulmonary Gas Exchange; D012129:Respiratory Function Tests; D019265:Spectroscopy, Near-Infrared