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Inhaled carbon monoxide increases retinal and choroidal blood flow in healthy humans.
Invest Ophthalmol Vis Sci. 2005 Nov; 46(11):4275-80.IO

Abstract

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 flowmetry.

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.

Authors+Show Affiliations

Medical University of Vienna [corrected]No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Randomized Controlled Trial
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

16249508

Citation

Resch, Hemma, et al. "Inhaled Carbon Monoxide Increases Retinal and Choroidal Blood Flow in Healthy Humans." Investigative Ophthalmology & Visual Science, vol. 46, no. 11, 2005, pp. 4275-80.
Resch H, Zawinka C, Weigert G, et al. Inhaled carbon monoxide increases retinal and choroidal blood flow in healthy humans. Invest Ophthalmol Vis Sci. 2005;46(11):4275-80.
Resch, H., Zawinka, C., Weigert, G., Schmetterer, L., & Garhöfer, G. (2005). Inhaled carbon monoxide increases retinal and choroidal blood flow in healthy humans. Investigative Ophthalmology & Visual Science, 46(11), 4275-80.
Resch H, et al. Inhaled Carbon Monoxide Increases Retinal and Choroidal Blood Flow in Healthy Humans. Invest Ophthalmol Vis Sci. 2005;46(11):4275-80. PubMed PMID: 16249508.
* Article titles in AMA citation format should be in sentence-case
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 - 2005/10/27/pubmed PY - 2005/12/22/medline PY - 2005/10/27/entrez SP - 4275 EP - 80 JF - Investigative ophthalmology & visual science JO - Invest Ophthalmol Vis Sci VL - 46 IS - 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 flowmetry. 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. SN - 0146-0404 UR - https://www.unboundmedicine.com/medline/citation/16249508/Inhaled_carbon_monoxide_increases_retinal_and_choroidal_blood_flow_in_healthy_humans_ DB - PRIME DP - Unbound Medicine ER -