title: Effect of helium breathing on intercostal and quadriceps muscle blood flow during exercise in COPD patients.
abstract: Emerging evidence indicates that, besides dyspnea relief, an improvement in locomotor muscle oxygen delivery may also contribute to enhanced exercise tolerance following normoxic heliox (replacement of inspired nitrogen by helium) administration in patients with chronic obstructive pulmonary disease (COPD). Whether blood flow redistribution from intercostal to locomotor muscles contributes to this improvement currently remains unknown. Accordingly, the objective of this study was to investigate whether such redistribution plays a role in improving locomotor muscle oxygen delivery while breathing heliox at near-maximal [75% peak work rate (WR(peak))], maximal (100%WR(peak)), and supramaximal (115%WR(peak)) exercise in COPD. Intercostal and vastus lateralis muscle perfusion was measured in 10 COPD patients (FEV(1) = 50.5 ± 5.5% predicted) by near-infrared spectroscopy using indocyanine green dye. Patients undertook exercise tests at 75 and 100%WR(peak) breathing either air or heliox and at 115%WR(peak) breathing heliox only. Patients did not exhibit exercise-induced hyperinflation. Normoxic heliox reduced respiratory muscle work and relieved dyspnea across all exercise intensities. During near-maximal exercise, quadriceps and intercostal muscle blood flows were greater, while breathing normoxic heliox compared with air (35.8 ± 7.0 vs. 29.0 ± 6.5 and 6.0 ± 1.3 vs. 4.9 ± 1.2 ml·min(-1)·100 g(-1), respectively; P < 0.05; mean ± SE). In addition, compared with air, normoxic heliox administration increased arterial oxygen content, as well as oxygen delivery to quadriceps and intercostal muscles (from 47 ± 9 to 60 ± 12, and from 8 ± 1 to 13 ± 3 mlO(2)·min(-1)·100 g(-1), respectively; P < 0.05). In contrast, normoxic heliox had neither an effect on systemic nor an effect on quadriceps or intercostal muscle blood flow and oxygen delivery during maximal or supramaximal exercise. Since intercostal muscle blood flow did not decrease by normoxic heliox administration, blood flow redistribution from intercostal to locomotor muscles does not represent a likely mechanism of improvement in locomotor muscle oxygen delivery. Our findings might not be applicable to patients who hyperinflate during exercise.
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, Greece.
authors.forename: Ioannis
authors.initials: I
authors.lastname: Vogiatzis
authors.forename: Helmut
authors.initials: H
authors.lastname: Habazettl
authors.forename: Andrea
authors.initials: A
authors.lastname: Aliverti
authors.forename: Dimitris
authors.initials: D
authors.lastname: Athanasopoulos
authors.forename: Zafeiris
authors.initials: Z
authors.lastname: Louvaris
authors.forename: Antonella
authors.initials: A
authors.lastname: LoMauro
authors.forename: Harrieth
authors.initials: H
authors.lastname: Wagner
authors.forename: Charis
authors.initials: C
authors.lastname: Roussos
authors.forename: Peter D
authors.initials: PD
authors.lastname: Wagner
authors.forename: Spyros
authors.initials: S
authors.lastname: Zakynthinos
mesh_terms: D000280:Administration, Inhalation; D015444:Exercise / Q000502:physiology*; D005260:Female; D006371:Helium / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D007866:Leg / Q000098:blood supply; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012039:Regional Blood Flow / Q000187:drug effects* / Q000502:physiology; D012132:Respiratory Muscles / Q000098:blood supply*
chemical_list: D006371:Helium; C038949:heliox; D010100:Oxygen