title: Retinal oxygen metabolism during normoxia and hyperoxia in healthy subjects.
abstract: OBJECTIVE
  To characterize retinal metabolism during normoxia and hyperoxia in healthy subjects.
  
  
  METHODS
  Forty-six healthy subjects were included in the present study, and data of 41 subjects could be evaluated. Retinal vessel diameters, as well as oxygen saturation in arteries and veins, were measured using the Dynamic Vessel Analyzer. In addition, retinal venous blood velocity was measured using bidirectional laser Doppler velocimetry, retinal blood flow was calculated, and oxygen and carbon dioxide partial pressures were measured from arterialized capillary blood from the earlobe. Measurements were done during normoxia and during 100% oxygen breathing.
  
  
  RESULTS
  Systemic hyperoxia caused a significant decrease in retinal venous diameter (-13.0% ± 4.5%) and arterial diameter (-12.1% ± 4.0%), in retinal blood velocity (-43.4% ± 7.7%), and in retinal blood flow (-57.0% ± 5.7%) (P < 0.001 for all). Oxygen saturation increased in retinal arteries (+4.4% ± 2.3%) and in retinal veins (+19.6% ± 6.2%), but the arteriovenous oxygen content difference significantly decreased (-29.4% ± 19.5%) (P < 0.001 for all). Blood oxygen tension in arterialized blood showed a pronounced increase from 90.2 ± 7.7 to 371.3 ± 92.7 mm Hg (P < 0.001). Calculated oxygen extraction in the eye decreased by as much as 62.5% ± 9.5% (P < 0.001).
  
  
  CONCLUSIONS
  Our data are compatible with the hypothesis that during 100% oxygen breathing a large amount of oxygen, consumed by the inner retina, comes from the choroid, which is supported by previous animal data. Interpretation of oxygen saturation data in retinal arteries and veins without quantifying blood flow is difficult. (ClinicalTrials.gov number, NCT01692821.).
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.
authors.forename: Stefan
authors.initials: S
authors.lastname: Palkovits
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Lasta
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Told
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
authors.forename: Doreen
authors.initials: D
authors.lastname: Schmidl
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
authors.forename: Agnes
authors.initials: A
authors.lastname: Boltz
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.
authors.forename: Katarzyna J
authors.initials: KJ
authors.lastname: Napora
authors.affiliation: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
authors.forename: René M
authors.initials: RM
authors.lastname: Werkmeister
authors.affiliation: Department of Ophthalmology, Emergency University Hospital, Bucharest, Romania.
authors.forename: Alina
authors.initials: A
authors.lastname: Popa-Cherecheanu
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Garhöfer
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
authors.forename: Leopold
authors.initials: L
authors.lastname: Schmetterer
mesh_terms: D000293:Adolescent; D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D064368:Healthy Volunteers; D006801:Humans; D018496:Hyperoxia / Q000378:metabolism* / Q000503:physiopathology; D017078:Laser-Doppler Flowmetry; D010092:Oximetry; D010100:Oxygen / Q000378:metabolism*; D012039:Regional Blood Flow / Q000502:physiology*; D012160:Retina / Q000378:metabolism* / Q000503:physiopathology; D012171:Retinal Vessels / Q000503:physiopathology*; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: oximetry; oxygen extraction; retinal blood flow