TY - JOUR
T1 - Inhaled carbon monoxide increases retinal and choroidal blood flow in healthy humans
AU - Resch, Hemma
AU - Zawinka, Claudia
AU - Weigert, Günther
AU - Schmetterer, Leopold
AU - Garhöfer, Gerhard
PY - 2005/11
Y1 - 2005/11
N2 - PURPOSE. It has been hypothesized that carbon monoxide (CO) acts as an important vascular paracrine factor and plays a role in blood flow regulation in several tissues. The present study investigated the effect of inhaled CO on retinal and choroidal blood flow. METHODS. Fifteen healthy male volunteers were studied in a randomized, double-masked, placebo-controlled design with washout periods of at least 1 week between study days. CO in a dose of 500 ppm or placebo (synthetic air without CO) was inhaled for 60 minutes. Ocular hemodynamics were measured at baseline and at 30 and 60 minutes after start of inhalation. Retinal vessel diameters were measured with a retinal vessel analyzer. RBC velocity was assessed using bidirectional laser Doppler velocimetry. Retinal blood flow was calculated based on retinal vessel diameters and RBC velocity. Fundus pulsation amplitude (FPA) was measured using laser interferometry, and submacular choroidal blood flow using laser Doppler flow-metry. RESULTS. Breathing of CO significantly increased carboxyhemoglobine, from 1.2 ± 0.5% to 8.5 ± 0.9% and 9.4 ± 0.6% at the two time points, respectively (P < 0.01). The diameter of retinal arteries increased by +3.5 ± 3.8% and +4.2 ± 3.9% (P < 0.01) in response to CO inhalation. In retinal veins, CO also induced an increase in diameter of +4.3 ± 3.0% and +4.8 ± 5.0%, respectively (P < 0.01). By contrast, placebo did not influence retinal vessel diameter. RBC velocity tended to increase during CO inhalation (+8 ± 22%), but this effect did not reach the level of significance (P = 0.1). Calculated retinal blood flow increased significantly by +12 ± 5% (P < 0.02). FPA increased after breathing CO by +20 ± 20% and +26 ± 21% at the two time points, respectively (P < 0.01). Subfoveal choroidal blood flow increased by +14 ± 9% and +15 ± 9% during breathing of CO (P < 0.01). CONCLUSIONS. This experiment demonstrated that retinal and choroidal blood flow increase during inhalation of CO. Whether this increase is caused by tissue hypoxia or a yet unknown mechanism has to be clarified.
AB - PURPOSE. It has been hypothesized that carbon monoxide (CO) acts as an important vascular paracrine factor and plays a role in blood flow regulation in several tissues. The present study investigated the effect of inhaled CO on retinal and choroidal blood flow. METHODS. Fifteen healthy male volunteers were studied in a randomized, double-masked, placebo-controlled design with washout periods of at least 1 week between study days. CO in a dose of 500 ppm or placebo (synthetic air without CO) was inhaled for 60 minutes. Ocular hemodynamics were measured at baseline and at 30 and 60 minutes after start of inhalation. Retinal vessel diameters were measured with a retinal vessel analyzer. RBC velocity was assessed using bidirectional laser Doppler velocimetry. Retinal blood flow was calculated based on retinal vessel diameters and RBC velocity. Fundus pulsation amplitude (FPA) was measured using laser interferometry, and submacular choroidal blood flow using laser Doppler flow-metry. RESULTS. Breathing of CO significantly increased carboxyhemoglobine, from 1.2 ± 0.5% to 8.5 ± 0.9% and 9.4 ± 0.6% at the two time points, respectively (P < 0.01). The diameter of retinal arteries increased by +3.5 ± 3.8% and +4.2 ± 3.9% (P < 0.01) in response to CO inhalation. In retinal veins, CO also induced an increase in diameter of +4.3 ± 3.0% and +4.8 ± 5.0%, respectively (P < 0.01). By contrast, placebo did not influence retinal vessel diameter. RBC velocity tended to increase during CO inhalation (+8 ± 22%), but this effect did not reach the level of significance (P = 0.1). Calculated retinal blood flow increased significantly by +12 ± 5% (P < 0.02). FPA increased after breathing CO by +20 ± 20% and +26 ± 21% at the two time points, respectively (P < 0.01). Subfoveal choroidal blood flow increased by +14 ± 9% and +15 ± 9% during breathing of CO (P < 0.01). CONCLUSIONS. This experiment demonstrated that retinal and choroidal blood flow increase during inhalation of CO. Whether this increase is caused by tissue hypoxia or a yet unknown mechanism has to be clarified.
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U2 - 10.1167/iovs.05-0417
DO - 10.1167/iovs.05-0417
M3 - Article
C2 - 16249508
AN - SCOPUS:33644666612
SN - 0146-0404
VL - 46
SP - 4275
EP - 4280
JO - Investigative Ophthalmology and Visual Science
JF - Investigative Ophthalmology and Visual Science
IS - 11
ER -