Hypoxia Tolerance and Retinal Vein Occlusion: A Pilot Evaluation

Abstract

Purpose

To determine if hypoxia tolerance in patients with retinal vein occlusion (RVO) following exposure to transient hypoxia is different from the hypoxia tolerance of healthy patients without retinal vein occlusion.

Methods

Consecutive patients presenting with RVO following exposure to transient hypoxia (Group I) were compared with healthy subjects (Group II). In addition to cardiovascular and plasma tests, functional respiratory evaluation was performed at rest and during exercise at both normal oxygen levels (21% O₂) and in hypoxia (11.6% O₂). We used the Wilcoxon test for statistical analysis.

Results

Both groups of eight males had similar mean ages: Group I, 47.5 years and Group II, 53 years. In Group I, three patients had glucose or lipid abnormalities, one had hypertension, and one minor thalassanemia. In Group II, one patient had hypertension. At rest in hypoxia, the oxyhemoglobinic desaturation was significantly different (p=0.03) in Group I in comparison with Group II (-13.8 versus −9.3). At exercise in hypoxia, the oxyhemoglobinic desaturation was similar in both groups but there was a statistically significant increase in both systolic (189 versus 155 mmHg; p=0.01) and diastolic (94 versus 77 mmHg; p=0.03) blood pressure in Group I. Ventilation rate and increased heart rate during hypoxia were higher in Group I compared with Group II but were not statistically significant.

Conclusions

In our pilot study, patients with RVO following exposure to transient hypoxia demonstrated intolerance to hypoxia and were significantly different from healthy subjects in their response to hypoxia. A larger study is required to confirm these preliminary results.