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Effect of Breathing a Mixture of 92% Oxygen (O2) + 8% Carbon Dioxide (CO2) on Flicker Induced Blood Flow Changes in Ocular Perfusion

This study has been completed.
Sponsor:
ClinicalTrials.gov Identifier:
NCT00719342
First Posted: July 21, 2008
Last Update Posted: November 14, 2014
The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details.
Information provided by (Responsible Party):
Gerhard Garhofer, Medical University of Vienna
  Purpose
It has been shown that diffuse luminance flicker increases retinal and optic nerve head blood flow. This indicates that a neuro-vascular coupling between neural activity and blood flow exists in the retina as described previously for the brain. Although a lot of mediators such as NO, pO2, pCO2, H+ and K+ have been proposed, the mechanism of this coupling is still a matter of controversy. However, it has been shown in an animal experiment, that an increase in blood flow, evoked by diffuse luminance flicker stimulation is paralleled by decrease in pO2 in the tissue. In a recently performed study we could show that breathing of 100% O2 did not influence flicker induced changes in the retina and optic nerve head. However, breathing of 100% oxygen also leads to a pronounced vasoconstriction of the retinal vessels and in turn to a increased tension of the vessel wall. Recent evidence indicates that a combination of 92% O2 and 8% CO2 can, at least partially, counteract the vasoconstrictory effect of O2 and increases tissue pO2. Thus, in this study the investigators set out to investigate the flicker light induced increase in blood flow under a mixture of O2/CO2 .

Condition Intervention
Flicker-induced Vasodilatation Drug: Oxygen + Carbondioxide Other: full field flickering light at 12.5 Hz

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double (Participant, Investigator)
Primary Purpose: Basic Science
Official Title: Effect of Breathing a Mixture of 92% O2 + 8% CO2 on Flicker Induced Blood Flow Changes in Ocular Perfusion

Resource links provided by NLM:


Further study details as provided by Gerhard Garhofer, Medical University of Vienna:

Primary Outcome Measures:
  • Optic nerve head blood flow [ Time Frame: 1 hour ]
  • Retinal vessel diameters [ Time Frame: 1 hour ]

Secondary Outcome Measures:
  • blood pressure [ Time Frame: 1 hour ]
  • pulse rate [ Time Frame: 1 hour ]

Enrollment: 24
Study Start Date: July 2008
Study Completion Date: December 2009
Primary Completion Date: May 2009 (Final data collection date for primary outcome measure)
Intervention Details:
    Drug: Oxygen + Carbondioxide
    Mixture of 92 % oxygen and 8 % carbon dioxide for inhalation
    Other Names:
    • O² + CO²
    • Oxymix
    Other: full field flickering light at 12.5 Hz
    1 minute stimulation with full field flickering light at 12.5 Hz during measurement of vessel diameters and measurement of blood flow.
  Eligibility

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Ages Eligible for Study:   18 Years to 35 Years   (Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes
Criteria

Inclusion Criteria:

  • Men and Women aged between 18 and 35 years, nonsmokers
  • Body mass index between 15th and 85th percentile
  • Normal findings in the medical history and physical examination unless the investigator considers an abnormality to be clinically irrelevant
  • Normal laboratory values unless the investigator considers an abnormality to be clinically irrelevant
  • Normal ophthalmic findings, ametropy < 3 Dpt.

Exclusion Criteria:

  • Regular use of medication, abuse of alcoholic beverages, participation in a clinical trial in the 3 weeks preceding the study
  • Treatment in the previous 3 weeks with any drug
  • Symptoms of a clinically relevant illness in the 3 weeks before the first study day
  • Blood donation during the previous 3 weeks
  Contacts and Locations
Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT00719342


Locations
Austria
Department of Clinical Pharmacology, Medical University of Vienna
Vienna, Austria, 1090
Sponsors and Collaborators
Medical University of Vienna
Investigators
Principal Investigator: Michael Wolzt, MD Department of Clinical Pharmacology, Medical University of Vienna
  More Information

Responsible Party: Gerhard Garhofer, Assoc. Prof. Priv. - Doz. Dr, Medical University of Vienna
ClinicalTrials.gov Identifier: NCT00719342     History of Changes
Other Study ID Numbers: OPHT-030606
First Submitted: July 1, 2008
First Posted: July 21, 2008
Last Update Posted: November 14, 2014
Last Verified: November 2014

Keywords provided by Gerhard Garhofer, Medical University of Vienna:
Retinal vessel diameter
Flicker-induced vasodilatation
Optic nerve head blood flow
Ocular Physiology
Regional Blood Flow