DARK ADAPTATION DURING SYSTEMIC HYPOXIA INDUCED BY CHRONIC RESPIRATORY INSUFFICIENCY.

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Abstract

PURPOSE: To investigate dark adaptation during hypoxia in chronic respiratory failure patients. METHODS: At three visits, dark adaptation was recorded by computerized dark adaptometry in thirteen patients with chronic respiratory insufficiency treated by long term oxygen therapy (LTOT). At visits 1 and 3, the patients were on their usual oxygen supplement. At visit 2, no oxygen was given. Each visit, an analysis of arterial blood gases measured pH, partial pressure of O2 (PaO2), partial pressure of CO2 (PaCO2), base excess (BE), standard bicarbonate (HCO3), and arterial oxygen saturation. Pulse oximetry (POX) was also recorded. RESULTS: Significant differences were recorded between visit 1 and 2 and between visit 2 and 3 for PaO2, arterial oxygen saturation, and POX; no differences were found for pH, PaCO2, BE, or HCO3. No differences were seen between visit 1 and 3 for any of the laboratory parameters. All patients had normal and unchanged dark adaptation at the three visits. CONCLUSIONS: Hypoxia in chronic respiratory insufficiency was associated with normal dark adaptation, in contrast to hypoxia in healthy individuals at high altitudes, which is known to produce impaired dark adaptation. Our result may partly reflect the influence of PaCO2 on the lumen of both choroidal and retinal vessels. At high altitudes, with hypocapnic vasoconstriction the oxygen supply to the retina is further compromised, resulting in reduced dark adaptation. We hypothesize that respiratory insufficiency with hyper- or normocapnia will have larger choroidal and retinal vessel lumens, added to by further dilation of retinal vessels during hypoxia. The tentative net effect would be preserved dark adaptation.

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  • Ophthalmology
Original languageEnglish
Pages (from-to)1307-1312
JournalInvestigative Ophthalmology & Visual Science
Volume50
StatePublished - 2009
Publication categoryResearch
Peer-reviewedYes