Reproducibility and sensitivity of scanning laser Doppler flowmetry during graded changes in Po2
- Karin Strenna,
- Rupert Menapacea,
- Georg Rainera,
- Oliver Findla,
- Michael Wolztb,
- Leopold Schmettererb,c
- aDepartment of Ophthalmology B, University of Vienna, Vienna, Austria, bDepartment of Clinical Pharmacology, University of Vienna, Vienna, Austria, cInstitute of Medical Physics, University of Vienna, Vienna, Austria
- L Schmetterer, Department of Clinical Pharmacology, Währinger Gürtel 18–20, A-1090 Vienna, Austria.
- Accepted 13 January 1997
Abstract
AIMS/BACKGROUND Recently a commercially available scanning laser Doppler flowmeter has been produced, which provides two dimensional maps of the retinal perfusion. The aim of the present study was to investigate the reproducibility and the sensitivity of these measurements.
METHODS 16 healthy subjects were randomised to inhale different gas mixtures of oxygen and nitrogen in a double blind crossover study. The following gas mixtures of oxygen and nitrogen were administered: 100% oxygen + 0% nitrogen, 80% oxygen + 20% nitrogen, 60% oxygen + 40% nitrogen, 40% oxygen + 60% nitrogen, 30% oxygen + 70% nitrogen, 20% oxygen + 80% nitrogen, 15% oxygen + 85% nitrogen, and 10% oxygen + 90% nitrogen. Retinal haemodynamic variables and systemic haemodynamics were measured during all inhalation periods. Recordings under resting conditions were performed three times to calculate intraclass coefficients.
RESULTS In two subjects we did not obtain technically adequate results. A dose dependent change in retinal blood flow during graded oxygen breathing was observed (p < 0.001). During 100% oxygen breathing blood flow decrease was between 29% and 33%, whereas blood flow increase was between 28% and 33% during inhalation of 10% oxygen + 90% nitrogen.
CONCLUSIONS Scanning laser Doppler flowmetry has an acceptable reproducibility and is appropriate for description of the effect of graded changes in Po 2 on retinal haemodynamics. The main problems with the system are the large zero offset, the fixation during retinal scanning, and the neglect of blood flow changes during the cardiac cycle.
