Flicker-induced Vasodilatation
Conditions
Keywords
Retinal vessel diameter, Flicker-induced vasodilatation, Optic nerve head blood flow, Ocular Physiology, Regional Blood Flow
Brief summary
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 .
Interventions
DRUGOxygen + Carbondioxide
Mixture of 92 % oxygen and 8 % carbon dioxide for inhalation
OTHERfull 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.
Sponsors
Medical University of Vienna
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
DOUBLE (Subject, Investigator)
Eligibility
Sex/Gender
ALL
Age
18 Years to 35 Years
Healthy volunteers
Yes
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
Design outcomes
Primary
| Measure | Time frame |
|---|---|
| Optic nerve head blood flow | 1 hour |
| Retinal vessel diameters | 1 hour |
Secondary
| Measure | Time frame |
|---|---|
| blood pressure | 1 hour |
| pulse rate | 1 hour |
Countries
Austria
Outcome results
None listed