Clinical trial NCT00719342: Effect of Breathing a Mixture of 92% Oxygen (O2) + 8% Carbon Dioxide (CO2) on Flicker Induced Blood Flow Changes in Ocular Perfusion
Official title: Effect of Breathing a Mixture of 92% O2 + 8% CO2 on Flicker Induced Blood Flow Changes in Ocular Perfusion
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Flicker-induced Vasodilatation
Keywords: Retinal vessel diameter
Flicker-induced vasodilatation
Optic nerve head blood flow
Ocular Physiology
Regional Blood Flow
Lead sponsor: Medical University of Vienna
Sponsor class: OTHER
First posted: 2008-07-21
Enrollment: 24
Sex: ALL
Minimum age (years): 18
Maximum age (years): 35
Standard ages: ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: CROSSOVER
Primary purpose: BASIC_SCIENCE

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 .


Eligibility 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

Primary outcomes:
measure: Optic nerve head blood flow
timeFrame: 1 hour
measure: Retinal vessel diameters
timeFrame: 1 hour
Secondary outcomes:
measure: blood pressure
timeFrame: 1 hour
measure: pulse rate
timeFrame: 1 hour
Other outcomes:
Locations:
city: Vienna
country: Austria
facility: Department of Clinical Pharmacology, Medical University of Vienna
Study officials:
affiliation: Department of Clinical Pharmacology, Medical University of Vienna
name: Michael Wolzt, MD
role: PRINCIPAL_INVESTIGATOR
References: