May 2004
Volume 45, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2004
Retinal arteriolar vascular reactivity response to hypercapnia in young normals assessed with the Canon Laser Blood Flowmeter
S.T. Venkataraman; C. Hudson; D. Priess; J. Fisher; J. Flanagan
Author Affiliations & Notes
  • S.T. Venkataraman
    School of Optometry, University of Waterloo, Waterloo, ON, Canada
  • C. Hudson
    School of Optometry, University of Waterloo, Waterloo, ON, Canada
    Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, ON, Canada
  • D. Priess
    Department of Anesthesiology, Toronto General Hospital, Toronto, ON, Canada
  • J. Fisher
    Department of Anesthesiology, Toronto General Hospital, Toronto, ON, Canada
  • J. Flanagan
    School of Optometry, University of Waterloo, Waterloo, ON, Canada
    Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, ON, Canada
  • Footnotes
    Commercial Relationships  S.T. Venkataraman, None; C. Hudson, None; D. Priess, None; J. Fisher, None; J. Flanagan, None.
  • Footnotes
    Support  CIHR, CFI
Investigative Ophthalmology & Visual Science May 2004, Vol.45, 2616. doi:
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      S.T. Venkataraman, C. Hudson, D. Priess, J. Fisher, J. Flanagan; Retinal arteriolar vascular reactivity response to hypercapnia in young normals assessed with the Canon Laser Blood Flowmeter . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2616.

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Abstract

Abstract: : Purpose: To determine the magnitude of change in retinal arteriolar diameter, blood velocity and flow using the Canon Laser Blood Flowmeter model 100 (CLBF) during hypercapnic provocation in a group of young normal subjects. Methods:The sample comprised eight normal subjects of mean age 26 years (SD 4.06). One eye of each subject was randomly selected. Participants were free from cardiovascular disease and any treatable respiratory disorders. A sequential re–breathing circuit (Hi–Ox SR, Viasys) was utilised to increase ETCO2 (i.e. the maximum concentration of CO2 in exhaled breath). In– and end–tidal gas concentrations were continuously recorded using a Cardiocap 5 (Datex–Ohmeda, USA) vital signs monitor. Baseline CLBF measurements were acquired when subjects breathed bottled air with gas flow set above minute ventilation (in order to artificially reduce ETCO2, thereby subsequently maintaining subject comfort). Hypercapnia was achieved by decreasing air flow relative to baseline until an approximate increase of 10% in ETCO2 was observed. CLBF measurements were acquired every minute during this procedure and also following hypercapnia. Blood pressure, heart and respiration rate were continuously monitored. Results: A stabilised group mean increase in ETCO2 of 12.77% (SD 2.8, range 9–18%) was achieved. Group mean arteriolar diameter, blood velocity and flow increased from 113.9 to 117.02µm (p=0.005), from 29.8 to 38.37µm/sec (p<0.001) and from 9.14 to 12.44µL/min (p<0.001) before and after provocation, respectively. There was a concomitant and significant decrease in inspired (p=0.001) and expired (p<0.001) oxygen concentration during hypercapnia. Conclusions:Retinal arteriolar blood flow, velocity and diameter significantly increased as a result of hypercapnic provocation. Hypercapnia results in a concomitant hypoxia and both of these factors will have impact upon retinal vascular reactivity.

Keywords: blood supply • retina • laser 
© 2004, The Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Permission to republish any abstract or part of an abstract in any form must be obtained in writing from the ARVO Office prior to publication.
Copyright © 2025 Association for Research in Vision and Ophthalmology.
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