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 erj00163-2012
DO 10.1183/09031936.00016312
A1 Ioannis Vogiatzis
A1 Zafeiris Louvaris
A1 Helmut Habazettl
A1 Vasileios Andrianopoulos
A1 Harrieth Wagner
A1 Charis Roussos
A1 Peter D. Wagner
A1 Spyros Zakynthinos
YR 2012
UL http://erj.ersjournals.com/content/early/2012/05/02/09031936.00016312.abstract
AB In healthy humans, cerebral oxygen desaturation during exercise affects motor unit recruitment, whilst oxygen supplementation enhances cerebral oxygenation and work capacity. It remains unknown whether in patients with COPD the well documented improvement in exercise tolerance with oxygen supplementation may also be partly due to the increase in cerebral oxygenation.By near infrared spectroscopy, we measured both frontal cerebral cortex blood flow (CBF) using indocyanine green dye and cerebrovascular oxygen saturation (%StO2) in 12 COPD patients during constant-load exercise to exhaustion at 75% of peak capacity. Subjects exercised breathing air, 100% O2 or normoxic heliox, the latter two in balanced order.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−1.100·g−1, respectively), compensating lower arterial O2 content (CaO2) in air and heliox, and leading to similar cerebral cortex oxygen delivery (CQO2, air: 5.3±0.4; O2: 5.5±0.6 and heliox: 5.6±1.0 mL O2·min−1 100·g−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 CQO2.Prolonged time to exhaustion by oxygen and heliox despite similar CQO2 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 an improvement in cerebral cortex oxygen availability plays a contributing role in increasing exercise capacity with oxygen or heliox in patients with COPD.