Comparison of different hyperoxic paradigms to induce vasoconstriction: implications for the investigation of retinal vascular reactivity.
Invest Ophthalmol Vis Sci
; 45(9): 3207-12, 2004 Sep.
Article
em En
| MEDLINE
| ID: mdl-15326142
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 < 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.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Vasos Retinianos
/
Vasoconstrição
/
Hiperóxia
Limite:
Adult
/
Female
/
Humans
/
Male
/
Middle aged
Idioma:
En
Revista:
Invest Ophthalmol Vis Sci
Ano de publicação:
2004
Tipo de documento:
Article