title: Heliox increases quadriceps muscle oxygen delivery during exercise in COPD patients with and without dynamic hyperinflation.
abstract: Some reports suggest that heliox breathing during exercise may improve peripheral muscle oxygen availability in patients with chronic obstructive pulmonary disease (COPD). Besides COPD patients who dynamically hyperinflate during exercise (hyperinflators), there are patients who do not hyperinflate (non-hyperinflators). As heliox breathing may differently affect cardiac output in hyperinflators (by increasing preload and decreasing afterload of both ventricles) and non-hyperinflators (by increasing venous return) during exercise, it was reasoned that heliox administration would improve peripheral muscle oxygen delivery possibly by different mechanisms in those two COPD categories. Chest wall volume and respiratory muscle activity were determined during constant-load exercise at 75% peak capacity to exhaustion, while breathing room air or normoxic heliox in 17 COPD patients: 9 hyperinflators (forced expiratory volume in 1 s = 39 ± 5% predicted), and 8 non-hyperinflators (forced expiratory volume in 1 s = 48 ± 5% predicted). Quadriceps muscle blood flow was measured by near-infrared spectroscopy using indocyanine green dye. Hyperinflators and non-hyperinflators demonstrated comparable improvements in endurance time during heliox (231 ± 23 and 257 ± 28 s, respectively). At exhaustion in room air, expiratory muscle activity (expressed by peak-expiratory gastric pressure) was lower in hyperinflators than in non-hyperinflators. In hyperinflators, heliox reduced end-expiratory chest wall volume and diaphragmatic activity, and increased arterial oxygen content (by 17.8 ± 2.5 ml/l), whereas, in non-hyperinflators, heliox reduced peak-expiratory gastric pressure and increased systemic vascular conductance (by 11.0 ± 2.8 ml·min(-1)·mmHg(-1)). Quadriceps muscle blood flow and oxygen delivery significantly improved during heliox compared with room air by a comparable magnitude (in hyperinflators by 6.1 ± 1.3 ml·min(-1)·100 g(-1) and 1.3 ± 0.3 ml O(2)·min(-1)·100 g(-1), and in non-hyperinflators by 7.2 ± 1.6 ml·min(-1)·100 g(-1) and 1.6 ± 0.3 ml O(2)·min(-1)·100 g(-1), respectively). Despite similar increase in locomotor muscle oxygen delivery with heliox in both groups, the mechanisms of such improvements were different: 1) in hyperinflators, heliox increased arterial oxygen content and quadriceps blood flow at similar cardiac output, whereas 2) in non-hyperinflators, heliox improved central hemodynamics and increased systemic vascular conductance and quadriceps blood flow at similar arterial oxygen content.
authors.affiliation: Department of Critical Care Medicine and Pulmonary Services, Evangelismos Hospital, M. Simou and G.P. Livanos Laboratories, National and Kapodistrian University of Athens, Athens, Greece.
authors.forename: Zafeiris
authors.initials: Z
authors.lastname: Louvaris
authors.forename: Spyros
authors.initials: S
authors.lastname: Zakynthinos
authors.forename: Andrea
authors.initials: A
authors.lastname: Aliverti
authors.forename: Helmut
authors.initials: H
authors.lastname: Habazettl
authors.forename: Maroula
authors.initials: M
authors.lastname: Vasilopoulou
authors.forename: Vasileios
authors.initials: V
authors.lastname: Andrianopoulos
authors.forename: Harrieth
authors.initials: H
authors.lastname: Wagner
authors.forename: Peter
authors.initials: P
authors.lastname: Wagner
authors.forename: Ioannis
authors.initials: I
authors.lastname: Vogiatzis
mesh_terms: D001158:Arteries / Q000187:drug effects / Q000378:metabolism; D001696:Biomechanical Phenomena / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods; D045853:Exhalation / Q000187:drug effects / Q000502:physiology; D005260:Female; D005541:Forced Expiratory Volume / Q000187:drug effects; D006371:Helium / Q000008:administration & dosage* / Q000378:metabolism; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000187:drug effects; D010100:Oxygen / Q000008:administration & dosage* / Q000378:metabolism; D029424:Pulmonary Disease, Chronic Obstructive / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology*; D052097:Quadriceps Muscle / Q000098:blood supply / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology; D012132:Respiratory Muscles / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D035441:Thoracic Wall / Q000187:drug effects / Q000378:metabolism
chemical_list: D006371:Helium; C038949:heliox; D010100:Oxygen