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Impressum
Retrobulbar Hemodynamics and Functional Effects after CO2 Breathing
Huber K., Adams H., Remky A., Arend O.
Universitäts-Augenklinik der RWTH-Aachen, Pauwelsstrasse 30, 52074 Aachen, Germany
Purpose: CO2 is known as a vasodilator in various brain regions.
In clinical routine the effect of gas mixtures (Carbogen) of CO2 and O2
are studied resulting in a wide interindividual respiratory response.
We investigated effects of CO2 on retrobulbar hemodynamics in young adults
to establish a vasodilatatory response test.
Methods: The largest healthy population to date of thirty healthy
adults (age 31 ± 7 years, from 21 to 48, 15 male, 15 female) were
studied under normo- and hypercapnic conditions. Color Doppler imaging
(Siemens Sonoline Sienna) was used to measure vasoreactivity in the ophthalmic
and central retinal artery. Therefore under both conditions the peak systolic
(PSV) and end-diastolic velocities (EDV) as well as Pourcelot index (PI)
were determined. Furthermore we studied contrast sensitivity (CSV 1000)
in lines per degree (cpd) under both condition.
Results: Hypercapnia lowered the intraocular pressure significantly
(p< 0.0001). Hypercapnia increased PSV by 17.1% and EDV by 23.3% in
the central retinal artery. In the ophthalmic artery PSV raised by 14%
and EDV by 21.1% under hypercapnia. There was no significant change of
the Pourcelot index of the central retinal and the ophthalmic artery.
Vasoreactivity in healthy subjects (velocity CO2-velocity baseline) was
independent of smoking habits or history of migraine headache. There was
a significant increase of contrast sensitivity under hypercapnia (contrast
3cpd: p< 0.0001; 6cpd: p< 0.0001; 12cpd: p< 0.0002; 18cpd: p<
0.03).
Conclusion: Hypercapnia showed functional improvements of contrast
sensitivity and led to decreased IOP. Flow velocity in the central retinal
and ophthalmic artery are effected by CO2. Responsiveness of vasoreactivity
could have an impact on therapy regimen therefore this test might be very
useful.