TY - JOUR T1 - Blood flow does not redistribute from respiratory to leg muscles during exercise breathing heliox or oxygen in COPD JF - European Respiratory Journal JO - Eur Respir J VL - 44 IS - Suppl 58 SP - 1392 AU - Zafeiris Louvaris AU - Ioannis Vogiatzis AU - Andrea Aliverti AU - Helmut Habazettl AU - Harrieth Wagner AU - Peter Wagner AU - Spyros Zakynthinos Y1 - 2014/09/01 UR - http://erj.ersjournals.com/content/44/Suppl_58/1392.abstract N2 - In COPD, one of the proposed mechanisms for improving exercise tolerance, when work of breathing is experimentally reduced, is redistribution of blood flow from the respiratory to locomotor muscles. We investigated whether exercise capacity is improved on the basis of blood flow redistribution whilst breathing heliox (designed to reduce work of breathing) and oxygen (O2) (designed to enhance systemic O2 delivery). Intercostal, abdominal and vastus-lateralis muscle perfusion was simultaneously measured in 10 patients (FEV1:46±12% pred.) by NIRS using indocyanine green dye. Measurements were performed during constant-load exercise at 75% peak workload to exhaustion while breathing room air, and then at the same workload, breathing either normoxic heliox (helium 79% and oxygen 21%) or 100% O2, the latter two in balanced order. Times to exhaustion whilst breathing heliox and O2 did not differ (659±42 and 696±48 sec, respectively), but both exceeded that on air (406±36 sec, p<0.001). At exhaustion, intercostal and abdominal muscle blood flow during heliox (9.5±0.6 and 8.0±0.7 ml/min/100g, respectively) was greater compared to air (6.8±0.5 and 6.0±0.5 ml/min/100g, respectively; p<0.05), whilst neither intercostal nor abdominal muscle blood flow differed between O2 and air. Quadriceps muscle blood flow was greater with heliox compared to air (30.2±4.1 versus 25.4±2.9 ml/min/100g; p<0.01), but did not differ between air and O2. While our findings confirm that reducing the burden on respiration by heliox or O2 prolongs exercise tolerance in COPD, they do not support the hypothesis that redistribution of blood flow from the respiratory to locomotor muscles is the explanation. ER -