Purpose
To estimate the effects of oxygen therapy on retinal vessel oxygen saturation in patients with chronic obstructive pulmonary disease (COPD).
Methods
The Oxymap T1 retinal oximeter (Oxymap ehf., Reykjavik, Iceland) is based on a fundus camera and analysis software. It simultaneously captures images of the retinal vessels at 570 nm and 600 nm wavelengths for calculation of hemoglobin oxygen saturation. Eleven patients with severe COPD (stage 3 and 4) on long term oxygen treatment were included in the study. Mean oxygen saturation in retinal arterioles and venules of the right eye was measured during breathing of their daily supplemental oxygen and ambient air. Mean oxygen saturation of retinal arterioles was compared with finger pulse oximetry and radial artery oxygen saturation, the latter only during ambient air breathing.
Results
Oxygen saturation (%) in retinal arterioles and venules of right eye (n=10) and finger was significantly increased during oxygen breathing compared with ambient air breathing (see table). Arteriovenous difference was not significantly different between ambient air breathing and supplemental oxygen breathing. The figure illustrates mean oxygen saturation (%) of retinal arterioles, radial artery and finger (n=10) after breathing ambient air for 10 minutes. Oxygen saturation in retinal arterioles was 88±5% compared with 92±4% in radial artery (P= 0.07, paired t test) and 91±3% in finger (P=0.34).
Conclusions
Oxygen therapy increases oxygen saturation of retinal arterioles and venules in patients with severe COPD. The retinal arteriovenous difference is unaffected by the oxygen therapy. Oxygen saturation measurements are not statistically different between retinal oximetry, peripheral pulse oximetry and radial arterial blood gas analysis.
Keywords: 688 retina •
635 oxygen •
550 imaging/image analysis: clinical