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.

Acute respiratory muscle unloading by normoxic helium–O2 breathing reduces the O2 cost of cycling and perceived exertion in obese adolescents

“…Although in normal subjects, this phenomenon may not happen during submaximal exercise (Wetter et al 1999), it could occur in obese patient population characterized by a substantially higher work of breathing and increased metabolic demands. Some previous studies in COPD patients (Louvaris et al 2012;Vogiatzis et al 2011) also demonstrated a reduced expiratory muscle activity during He-O 2 breathing, with consequent improvements in cardiac output and "central" hemodynamics and further increases in peripheral muscle O 2 delivery.…”

An Official American Thoracic Society/European Respiratory Society Statement: Update on Limb Muscle Dysfunction in Chronic Obstructive Pulmonary Disease

“…During strenuous exercise, peripheral vasoconstriction associated with the high demand for respiratory muscle blood flow appears to compromise limb muscle perfusion (261,425,426) and consequently enhance muscle fatigue (427). A blood redistribution phenomenon in favor of the respiratory muscles may also occur in COPD (428), and it has been hypothesized that strategies that reduce respiratory muscle work may alleviate limb muscle fatigue by restoring blood flow to the limb muscles (267,429). This hypothesis was supported by a study from Amann and coworkers, who gave a range of interventions designed to improve oxygenation (by supplemental oxygen) and/or reduce work of breathing (proportional-assist ventilation or helium or both) (267).…”

“…Recently, NIRS has been used in combination with the light-absorbing tracer indocyanine green dye to quantify regional blood flow in muscle and connective tissue during dynamic exercise in patients with COPD (352). Subsequent studies showed that respiratory muscle unloading improves locomotor muscle blood flow and oxygen delivery during exercise in patients with different patterns and degrees of dynamic hyperinflation (429,494). 31 P-NMR spectroscopy is a noninvasive method to evaluate high-energy compounds ATP, PCr, inorganic phosphate (Pi), and intracellular pH of single muscle groups during exercise and recovery (495).…”

Strategies of muscle training in very severe COPD patients

“…A recent study in patients with severe COPD [20] confirmed that heliox administration during constant-load exercise (at 75% of peak capacity) reduces total respiratory muscle power by unloading both inspiratory and expiratory muscles, as well as improving central haemodynamic responses (increase in stroke volume) and arterial oxygen content. These findings [20] confirmed those of a previous study showing faster cardio-dynamic responses…”

“…Enhanced oxygen delivery to peripheral muscles following administration of heliox during exercise in severe COPD may occur via a number of mechanisms, namely: 1) improved cardiac output secondary to reduced intra-thoracic pressures and/or pleural pressure swings; 2) improved arterial oxygen content; and 3) blood flow redistribution from respiratory to peripheral muscles secondary to reduction in the mechanical load of the respiratory muscles [19]. A recent study in patients with severe COPD [20] confirmed that heliox administration during constant-load exercise (at 75% of peak capacity) reduces total respiratory muscle power by unloading both inspiratory and expiratory muscles, as well as improving central haemodynamic responses (increase in stroke volume) and arterial oxygen content. These findings [20] confirmed those of a previous study showing faster cardio-dynamic responses…”