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Richard W. Cheng, Joseph A. Fisher, James Duffin, John G. Flanagan, Tien Wong, Monica Jong, Sunni R. Patel, Alanna Adleman, Christopher Hudson; Retinal Arteriolar Reactivity Response Characteristics Assessed Using a Sinusoidal Hyperoxic Provocation. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6844.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the vascular reactivity response characteristics of the retinal arterioles to hyperoxic provocation.
Four healthy volunteers were subjected to steady baseline (PETO2 100mmHg) and then sinusoidal hyperoxic provocation (PETO2 varied according to a sinusoid waveform between 100 and 500mmHg) using the RespirActTM gas sequencer. The Canon Laser Blood Flowmeter (CLBF-100) was used to repeatedly measure retinal arteriole reactivity. Sinusoidal end-tidal O2 and retinal arteriole reactivity data were fitted with a sine wave curve. The fitting procedure was assisted by specially-written analysis programs (National Instruments Inc, LabVIEW) that used the Levenberg-Marquardt algorithm. The phase lag, time constant, response time, gain, and "cut-off period" of the arteriole reactivity measurements to the sinusoidal hyperoxic provocation was computed.
The average correlation coefficient for the sinusoidal hyperoxic and diameter fits were r=0.999±0.0009 and r=0.730±0.1735, respectively, while for velocity and blood flow the fit values were r=0.452±0.1687 and r=0.530±0.1621, respectively. For diameter, the mean phase lag, time constant and response time were 1.30±0.59 min, 1.30±0.59 min, and 3.89±1.78 min, respectively. The mean diameter "cutoff period", the sinusoidal period that gives the corresponding vascular response of the time constant during a 500 mmHg step change, was 8.15±3.72 min. The average gain defined by the mean maximal Δ diameter/Δ 100 mmHg O2 was -1.92±0.37. Based on the sinusoidal diameter fit, the average maximal change in diameter was -7.69±1.50 µm.
Assuming first order linear dynamics, we demonstrate a novel method of calculating the response time of the retinal arterioles to hyperoxic provocation.
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