RT Journal Article
SR Electronic
T1 Cerebral cortex oxygen delivery and exercise limitation in patients with COPD
JF European Respiratory Journal
JO Eur Respir J
FD European Respiratory Society
SP 3310
VO 40
IS Suppl 56
A1 Ioannis Vogiatzis
A1 Zafeiris Louvaris
A1 Helmut Habazettl
A1 Vasileios Andrianopoulos
A1 Harrieth Wagner
A1 George Zakynthinos
A1 Charis Roussos
A1 Peter Wagner
YR 2012
UL http://erj.ersjournals.com/content/40/Suppl_56/3310.abstract
AB Background: During hypoxic exercise in healthy humans, limited frontal cerebral cortex oxygen delivery may signal the brain to cease exercise.Aim: Whether in patients with COPD experiencing exercise-induced arterial O2 desaturation, frontal cerebral cortex oxygen delivery is reduced, remains unknown.Methods: By near infrared spectroscopy, we measured both frontal cerebral cortex blood flow (CBF) using indocyanine green dye, and cerebrovascular O2 saturation (%StO2) in 12 COPD patients during constant-load exercise at 75% of peak capacity. Subjects exercised breathing air, 100% O2 or normoxic heliox, the latter two in balanced order. Results: Time to exhaustion breathing air was less than for oxygen or heliox (394±35 vs. 670±43 and 637±46 sec, respectively). In each condition, CBF increased from rest to exhaustion. At exhaustion, CBF was higher breathing air and heliox than oxygen (30.9±2.3 and 31.3±3.5 vs. 26.6±3.2 ml.min-1.100g-1, respectively), compensating lower arterial O2 content (CaO2) in air and heliox, and leading to similar frontal cerebral cortex oxygen delivery (air: 5.3±0.4, O2: 5.5±0.6 and heliox: 5.6±1.0 ml.O2.min-1.100g-1). In contrast, end-exercise %StO2 was greater breathing oxygen compared to air or heliox (67±4 vs. 57±3 and 53±3%, respectively), reflecting CaO2 rather than frontal cerebral cortex oxygen delivery.Conclusion: Prolonged time to exhaustion by oxygen and heliox despite similar cerebral cortex oxygen delivery as in air, lower %StO2 with heliox than oxygen, yet similar endurance time, and similar %StO2 on air and heliox despite greater endurance with heliox, do not support the hypothesis that cortical oxygen delivery is important in limiting exercise capacity in COPD.