Assessment of acute mild hypoxia on retinal oxygen saturation using snapshot retinal oximetry.
PURPOSE
To study the effect of acute mild hypoxia on retinal oxygen saturation.


METHODS
Spectral retinal images were acquired under normoxic and hypoxic conditions for 10 healthy human volunteers (six male, four female, aged 25 ± 5 years [mean ± SD]) using a modified fundus camera fitted with an image-replicating imaging spectrometer (IRIS). Acute, mild hypoxia was induced by changing the oxygen saturation of inhaled air from 21% to 15% using a hypoxia generator with subjects breathing the hypoxic gas mixture for 10 minutes. Peripheral arterial oxygen saturation of the subjects was monitored using fingertip-pulse oximetry. Images were processed to calculate oxygen saturation, arteriovenous difference in oxygen saturation, and vessel diameter. Data are presented as mean ± SD and were analyzed using paired sample t-test with significance accepted at P < 0.05.


RESULTS
The retinal arterial and venous oxygen saturation was 98.5% ± 1.6% and 70.7% ± 2.7% during normoxia. A reduction in the fraction of inspired oxygen resulted in a decline (P < 0.001) in both retinal-arterial and venous oxygen saturation to 90.3% ± 2.0% and 62.4% ± 2.2%, respectively. The arteriovenous oxygen saturation difference in normoxia (27.8% ± 2.9%) and hypoxia (27.9% ± 2.1%) did not change. Retinal arteriolar and venular diameters increased (P < 0.001) by 4% and 3%, respectively, under hypoxia.


CONCLUSIONS
The acute inhalation of a hypoxic gas mixture resulted in a decline in both retinal-arterial and venous saturation, while arteriovenous oxygen difference was maintained with an accompanying significant increase in retinal vessel diameter. This may suggest an autoregulatory response to acute mild hypoxia.
['Choudhary|Tushar R|TR|', 'Ball|Derek|D|', 'Fernandez Ramos|Javier|J|', 'McNaught|Andrew I|AI|', 'Harvey|Andrew R|AR|']
D000208:Acute Disease D000328:Adult D005260:Female D005451:Fluorescein Angiography D005654:Fundus Oculi D006801:Humans D000860:Hypoxia D008297:Male D010092:Oximetry D010101:Oxygen Consumption D012016:Reference Values D012160:Retina D012171:Retinal Vessels
hypoxia oximetry autoregulation hemoglobin retina spectral imaging