June 2013
Volume 54, Issue 15
Free
ARVO Annual Meeting Abstract  |   June 2013
Assessment of Total Retinal Blood Flow under Systemic Hypercapnia and Hypocapnia
Author Affiliations & Notes
  • Ayda Shahidi
    Ophthalmology & Vision Science, University Health Network, Toronto, ON, Canada
  • Sunni Patel
    Ophthalmology & Vision Science, University Health Network, Toronto, ON, Canada
  • John Flanagan
    Ophthalmology & Vision Science, University Health Network, Toronto, ON, Canada
    Optometry & Vision Science, University of Waterloo, Waterloo, ON, Canada
  • Ou Tan
    Ophthalmology, Oregon Health and Science University, Portland, OR
  • David Huang
    Ophthalmology, Oregon Health and Science University, Portland, OR
  • Christopher Hudson
    Ophthalmology & Vision Science, University Health Network, Toronto, ON, Canada
    Optometry & Vision Science, University of Waterloo, Waterloo, ON, Canada
  • Footnotes
    Commercial Relationships Ayda Shahidi, None; Sunni Patel, None; John Flanagan, Heidelberg Engineering (C), Heidelberg Engineering (R), Heidleberg Engineering (F), Carl Zeiss Meditec (C), Carl Zeiss Meditiec (R), Carl Zeiss Meditiec (R), Alcon Pharmaceuticals (R), Alcon Pharmaceuticals (R), Optovue Inc (F), Optovue Inc (F), Photon etc (F), Photon etc (F); Ou Tan, Optovue (F), Optovue (P), Carl Zeiss Meditec (P); David Huang, Optovue (F), Optovue (I), Optovue (P), Optovue (R), Carl Zeiss Meditec (P); Christopher Hudson, Opovue Inc (F)
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2013, Vol.54, 4637. doi:
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    • Get Citation

      Ayda Shahidi, Sunni Patel, John Flanagan, Ou Tan, David Huang, Christopher Hudson, ; Assessment of Total Retinal Blood Flow under Systemic Hypercapnia and Hypocapnia. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4637.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: To investigate the effect of change in systemic partial pressure of CO2 on total retinal blood flow (TRBF) as measured by Doppler Fourier-domain optical coherence tomography (OCT)

Methods: TRBF scans were captured in nine healthy individuals (mean age ± standard deviation: 27±4, 6 males) using the RTVue™ OCT double ring blood flow protocol. Measurements were captured during homeostatic PETCO2 levels, hypercapnia (+5/+10/+15 mmHg PETCO2), back to baseline and hypocapnia (-5/-10/-15 mmHg PETCO2) using a custom-designed computer controlled gas blender (RespirAct™) with a sequential gas delivery rebreathing system. The order for hyper- and hypo-capnia conditions was randomized. Repeated measure analysis of variance (reANOVA) and Tukey’s post-hoc analysis were used to compare Doppler OCT measurements amongst breathing conditions. The effect of end-tidal CO2 on the outcomes was investigated using regression models.

Results: TRBF (45.9 ± 10.9, vs 60.9 ± 12.1 µl/min), superior RBF (24.0 ± 9.3 vs 33.8 ± 9.5 µl/min) , arterial (14.1 ± 2.7 vs 19.9 ± 4.5 mm/s) and venous (12.5 ± 1.7 vs 15.6 ± 1.3 mm/s) velocities were significantly different between baseline measurements and extreme hypercapnia (p<0.0001). There were general trends towards reduced retinal blood flow parameters during hypocapnia but the differences with the baseline, except for the superior arterial vessel area (p=0.006), were not statistically significant. Increased PETCO2 had a significant effect on the outcomes (p<0.002 for all states).

Conclusions: In healthy individuals, a 15% increase in end tidal CO2 significantly raised TRBF and vessel velocity, while, hypocapnia significantly reduced retinal hemodynamics only in the superior arterial area.

Keywords: 550 imaging/image analysis: clinical • 436 blood supply • 688 retina  
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