Comparison of different hyperoxic paradigms to induce vasoconstriction: implications for the investigation of retinal vascular reactivity. Gilmore, E. D, Hudson, C., Venkataraman, S. T, Preiss, D., & Fisher, J. Investigative Ophthalmology & Visual Science, 45(9):3207--12, September, 2004.
Comparison of different hyperoxic paradigms to induce vasoconstriction: implications for the investigation of retinal vascular reactivity [link]Paper  doi  abstract   bibtex   
PURPOSE: To compare the impact of three different techniques used to induce hyperoxia on end-tidal CO2 (PETCO2). The relationship between change in PETCO2 and retinal hemodynamics was also assessed to determine the clinical research relevance of this parameter. METHODS: The sample comprised 10 normal subjects (mean age, 25 years; range, 21-49 years). Each subject attended for three sessions. At each session, subjects initially breathed air followed by O2 only; O2 plus CO2, using a nonrebreathing circuit (with CO2 flow continually adjusted to negate drift of PETCO2); or air followed by O2, using a sequential rebreathing circuit. In addition, using a separate sample of eight normal subjects (mean age, 26.5 years; range, 24-36 years), a methodology that initially raised PETCO2 and then returned to homeostatic levels was used to determine the impact, if any, of perturbation of PETCO2 on retinal hemodynamics. RESULTS: The difference in group mean PETCO2 between baseline and elevated O2 breathing was significantly different (t-test, P = 0.0038) for O2-only administration with a nonrebreathing system. The sequential rebreathing technique resulted in a significantly lower difference (i.e., before and during hyperoxia) of individual PETCO2 (t-test, P = 0.0317). The PETCO2 perturbation resulted in a significant (P \textless 0.005) change of retinal arteriolar diameter, blood velocity, and blood flow. CONCLUSIONS: The sequential rebreathing technique resulted in a reduced variability of PETCO2. A relatively modest change in PETCO2 resulted in a significant change in retinal hemodynamics. Rigorous control of PETCO2 is necesssary to attain standardized, reproducible hyperoxic stimuli for the assessment of retinal vascular reactivity.
@article{gilmore_comparison_2004,
	title = {Comparison of different hyperoxic paradigms to induce vasoconstriction: implications for the investigation of retinal vascular reactivity},
	volume = {45},
	issn = {0146-0404},
	shorttitle = {Comparison of different hyperoxic paradigms to induce vasoconstriction},
	url = {http://www.ncbi.nlm.nih.gov/pubmed/15326142},
	doi = {10.1167/iovs.03-1223},
	abstract = {PURPOSE: To compare the impact of three different techniques used to induce hyperoxia on end-tidal CO2 (PETCO2). The relationship between change in PETCO2 and retinal hemodynamics was also assessed to determine the clinical research relevance of this parameter. METHODS: The sample comprised 10 normal subjects (mean age, 25 years; range, 21-49 years). Each subject attended for three sessions. At each session, subjects initially breathed air followed by O2 only; O2 plus CO2, using a nonrebreathing circuit (with CO2 flow continually adjusted to negate drift of PETCO2); or air followed by O2, using a sequential rebreathing circuit. In addition, using a separate sample of eight normal subjects (mean age, 26.5 years; range, 24-36 years), a methodology that initially raised PETCO2 and then returned to homeostatic levels was used to determine the impact, if any, of perturbation of PETCO2 on retinal hemodynamics. RESULTS: The difference in group mean PETCO2 between baseline and elevated O2 breathing was significantly different (t-test, P = 0.0038) for O2-only administration with a nonrebreathing system. The sequential rebreathing technique resulted in a significantly lower difference (i.e., before and during hyperoxia) of individual PETCO2 (t-test, P = 0.0317). The PETCO2 perturbation resulted in a significant (P {\textless} 0.005) change of retinal arteriolar diameter, blood velocity, and blood flow. CONCLUSIONS: The sequential rebreathing technique resulted in a reduced variability of PETCO2. A relatively modest change in PETCO2 resulted in a significant change in retinal hemodynamics. Rigorous control of PETCO2 is necesssary to attain standardized, reproducible hyperoxic stimuli for the assessment of retinal vascular reactivity.},
	number = {9},
	urldate = {2009-02-13},
	journal = {Investigative Ophthalmology \& Visual Science},
	author = {Gilmore, Edward D and Hudson, Chris and Venkataraman, Subha T and Preiss, David and Fisher, Joe},
	month = sep,
	year = {2004},
	pmid = {15326142},
	keywords = {hyperoxia, LDF, retina},
	pages = {3207--12},
	file = {gilmore2004.pdf:/Users/nickb/Zotero/storage/PFSDRXBX/gilmore2004.pdf:application/pdf;PubMed Snapshot:/Users/nickb/Zotero/storage/SJ4PSBMI/entrez.html:text/html}
}
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