title: Blood flow does not redistribute from respiratory to leg muscles during exercise breathing heliox or oxygen in COPD.
abstract: In patients with chronic obstructive pulmonary disease (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. Accordingly, we investigated whether exercise capacity is improved on the basis of blood flow redistribution during exercise while subjects are breathing heliox (designed to primarily reduce the mechanical work of breathing) and during exercise with oxygen supplementation (designed to primarily enhance systemic oxygen delivery but also to reduce mechanical work of breathing). Intercostal, abdominal, and vastus lateralis muscle perfusion were simultaneously measured in 10 patients with COPD (forced expiratory volume in 1 s: 46 ± 12% predicted) by near-infrared spectroscopy using indocyanine green dye. Measurements were performed during constant-load exercise at 75% of peak capacity to exhaustion while subjects breathed room air and, then at the same workload, breathed either normoxic heliox (helium 79% and oxygen 21%) or 100% oxygen, the latter two in balanced order. Times to exhaustion while breathing heliox and oxygen did not differ (659 ± 42 s with heliox and 696 ± 48 s with 100% O2), but both exceeded that on room air (406 ± 36 s, P < 0.001). At exhaustion, intercostal and abdominal muscle blood flow during heliox (9.5 ± 0.6 and 8.0 ± 0.7 ml · min(-1)·100 g(-1), respectively) was greater compared with room air (6.8 ± 0.5 and 6.0 ± 0.5 ml·min(-1)·100 g·, respectively; P < 0.05), whereas neither intercostal nor abdominal muscle blood flow differed between oxygen and air breathing. Quadriceps muscle blood flow was also greater with heliox compared with room air (30.2 ± 4.1 vs. 25.4 ± 2.9 ml·min(-1)·100 g(-1); P < 0.01) but did not differ between air and oxygen breathing. Although our findings confirm that reducing the burden on respiration by heliox or oxygen breathing prolongs time to exhaustion (at 75% of maximal capacity) in patients with COPD, they do not support the hypothesis that redistribution of blood flow from the respiratory to locomotor muscles is the explanation.
authors.affiliation: First Department of Critical Care Medicine and Pulmonary Services, GP Livanos and M Simou Laboratories, Medical School of Athens University, Evangelismos Hospital, Athens, Greece; National and Kapodistrian University of Athens, Department of Physical Education and Sports Sciences, Athens, Greece;
authors.forename: Zafeiris
authors.initials: Z
authors.lastname: Louvaris
authors.affiliation: First Department of Critical Care Medicine and Pulmonary Services, GP Livanos and M Simou Laboratories, Medical School of Athens University, Evangelismos Hospital, Athens, Greece; National and Kapodistrian University of Athens, Department of Physical Education and Sports Sciences, Athens, Greece; University of the West of Scotland, Institute of Clinical Exercise and Health Sciences, Hamilton, United Kingdom;
authors.forename: Ioannis
authors.initials: I
authors.lastname: Vogiatzis
authors.affiliation: Dipartimento di Biongegneria, Politecnico di Milano, Milano Italy;
authors.forename: Andrea
authors.initials: A
authors.lastname: Aliverti
authors.affiliation: Institute of Physiology, Charite Campus Benjamin Franklin, Berlin, Germany; Institute of Anesthesiology, German Heart Institute, Berlin, Germany;
authors.forename: Helmut
authors.initials: H
authors.lastname: Habazettl
authors.affiliation: Department of Medicine, University of California San Diego, La Jolla, California.
authors.forename: Harrieth
authors.initials: H
authors.lastname: Wagner
authors.affiliation: Department of Medicine, University of California San Diego, La Jolla, California.
authors.forename: Peter
authors.initials: P
authors.lastname: Wagner
authors.affiliation: First Department of Critical Care Medicine and Pulmonary Services, GP Livanos and M Simou Laboratories, Medical School of Athens University, Evangelismos Hospital, Athens, Greece; szakynthinos@yahoo.com.
authors.forename: Spyros
authors.initials: S
authors.lastname: Zakynthinos
mesh_terms: D000368:Aged; D001945:Breathing Exercises / Q000379:methods; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods; D017079:Exercise Tolerance / Q000502:physiology; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006371:Helium / Q000378:metabolism*; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D007866:Leg / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism / Q000503:physiopathology*; D010100:Oxygen / Q000378:metabolism*; D029424:Pulmonary Disease, Chronic Obstructive / Q000378:metabolism / Q000503:physiopathology*; D012039:Regional Blood Flow / Q000502:physiology*; D019265:Spectroscopy, Near-Infrared / Q000379:methods
chemical_list: D006371:Helium; C038949:heliox; D010100:Oxygen
keywords: abdominal muscle; chronic obstructive pulmonary disease; exercise; near-infrared spectroscopy; perfusion