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

Medical University of Vienna

Status

Completed

Conditions

Flicker-induced Vasodilatation

Treatments

Other: full field flickering light at 12.5 Hz

Drug: Oxygen + Carbondioxide

Study type

Interventional

Funder types

Other

Identifiers

NCT00719342

OPHT-030606

Details and patient eligibility

About

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 .

Enrollment

24 patients

Sex

All

Ages

18 to 35 years old

Volunteers

Accepts Healthy Volunteers

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