TY - JOUR T1 - Cerebral cortex blood flow, oxygen delivery and oxygenation during normoxic and hypoxic exercise in healthy humans JF - European Respiratory Journal JO - Eur Respir J VL - 40 IS - Suppl 56 SP - 3309 AU - Zafeiris Louvaris AU - Ioannis Vogiatzis AU - Helmut Habazettl AU - Vasileios Andrianopoulos AU - Harrieth Wagner AU - George Zakynthinos AU - Charis Roussos AU - Peter Wagner Y1 - 2012/09/01 UR - http://erj.ersjournals.com/content/40/Suppl_56/3309.abstract N2 - Background: During maximal hypoxic exercise a reduction in cerebral oxygen delivery may constitute a signal to terminate exercise.Aim: To investigate whether the rate of increase in cerebral cortex oxygen delivery is limited in hypoxic compared to normoxic exercise.Methods: We assessed frontal cerebral cortex blood flow using near infrared spectroscopy and the light-absorbing tracer indocyanine green dye, as well as frontal cortex oxygen saturation (StO2%) in 11 cyclists during incremental exercise to the limit of tolerance (WRmax) in normoxia and acute hypoxia (FIO2:0.12).Results: In normoxia, cerebral cortex blood flow and oxygen delivery increased (p<0.05) from baseline to sub-maximal exercise reaching peak values at near-maximal exercise (80%WRmax: 287±9W; 81±23% and 75±22% increase relative to baseline, respectively), both leveling off thereafter up to WRmax (382±10W). Cerebral cortex StO2% did not change from baseline (66±3%) throughout graded exercise. During hypoxic exercise, cerebral cortex blood flow increased from baseline to sub-maximal exercise peaking at 80%WRmax (213±6W; 60±15% relative increase) before declining towards baseline at WRmax (289±5W). Despite this, cerebral cortex oxygen delivery remained unchanged from baseline throughout graded exercise, being at WRmax lower than at comparable loads (287±9W) in normoxia (by 58±12%). Cerebral cortex StO2% fell from baseline (58±2%) on moderate exercise in parallel with arterial oxygen saturation, but then remained unchanged to exhaustion (47±1%).Conclusion: Cerebral cortex oxygen delivery is limited in hypoxia compared to normoxia, thus potentialy compromising maximal exercise capacity in hypoxia. ER -