Histogenous Hypoxia in Depression: A Cross-Sectional Paired Study into Venous Blood Gases in Outpatients with Depression

Abstract Background: It has been suggested that oxidative stress is increased and antioxidant defenses are decreased in depression, and oxidative stress has a complex relationship with hypoxia. Is there a definite hypoxia index in patients with depression? Also, any other correlations between hypoxia indicators and the symptoms of depression remain unreported. Methods: In the present study, a cross-sectional design was undertaken with 1:1 pairs. Patients with depression and healthy participants were recruited from the Guangdong Province Hospital of Traditional Chinese Medicine. Both groups were assessed using the Hamilton Depression Scale (including five factors: anxiety/somatization, weight, cognition impairment, hysteresis and sleep) and had their venous blood gases analyzed. All data were analyzed using the PASW Statistics 18.0 data statistical package. Results were analyzed statistically using the paired t test, Pearson correlation analysis and multiple linear regression analysis. Results: In total 52 cases were recruited to each study group, including 15 (28.8%) males and 37 (71.2%) females. The values of the mean venous pH, PvO2, SvO2 and CvO2 in the depressed group of patients were higher than those of the control group. PvCO2 was also lower in the depressed than in the control group, and this difference was statistically significant. The total depressive score and cognitive impairment factor were related to PvO2, while the anxiety/somatization and sleep factors were related to the value of the venous pH. Age was positively correlated with venous pH in both study groups. Venous pH had a positive association with PVO2 in the depressed group (multiple linear regression analysis), but there was no significant correlation between these two factors in the non-depressed control group. Conclusion: Histogenous hypoxia is present in patients with depression and this is related to elevated venous pH; both of these are related to depression. Elevated venous pH and decreased PvCO2 may explain histogenous hypoxia in depression and venous blood gas concentrations potentially represent a biomarker for depression.