Heliox increases lower limb O(2)DEL and utilization during dynamic exercise in patients with moderate to severe COPD. These effects enhance exercise tolerance in this patient population.
The purpose of this study was to investigate whether helium-hyperoxia (HeHOx) would allow greater tolerance to maximal and submaximal exercise compared to hyperoxia (HOx) on isolation in hypoxaemic chronic obstructive pulmonary disease (COPD) patients under long-term oxygen therapy.In a double-blind study, 24 males in the Global Initiative for Chronic Obstructive Lung Disease functional class IV (forced expiratory volume in 1 s 35.2¡10.1% predicted and arterial oxygen tension 56.2¡7.5 mmHg) were submitted to incremental and constant load cycling at 70-80% peak work rate while breathing HOx (60% nitrogen and 40% oxygen) or HeHOx (60% helium and 40% oxygen).HeHOx improved resting airflow obstruction and lung hyperinflation in all but two patients (p,0.05). Peak work rate and time to exercise intolerance were higher with HeHOx than HOx in 17 (70.8%) out of 24 patients and 14 (66.6%) out of 21 patients, respectively (p,0.05). End-expiratory lung volumes were lower with HeHOx, despite a higher ventilatory response (p,0.05). HeHOx speeded on-exercise oxygen uptake kinetics by ,30%, especially in more disabled and hyperinflated patients. Fat-free mass was the only independent predictor of higher peak work rate with HeHOx (r 2 50.66, p,0.001); in contrast, none of the resting characteristics or exercise responses were related to improvements in time to exercise intolerance (p.0.05).Helium is a valuable ergogenic aid when added to HOx for most long-term oxygen therapy-dependent patients with advanced COPD. @ERSpublications Helium is a valuable ergogenic aid when added to hyperoxia for most advanced COPD patients on long-term oxygen therapy
This study addressed whether O(2) delivery during recovery from high-intensity, supra-gas exchange threshold exercise would be matched to O(2) utilization at the microvascular level in patients with mitochondrial myopathy (MM). Off-exercise kinetics of (1) pulmonary O(2) uptake VO(2P) (2) an index of fractional O(2) extraction by near-infrared spectroscopy (Δ[deoxy-Hb + Mb]) in the vastus lateralis and (3) cardiac output (Q'(T)) by impedance cardiography were assessed in 12 patients with biopsy-proven MM (chronic progressive external ophthalmoplegia) and 12 age- and gender-matched controls. Kinetics of VO(2P) were significantly slower in patients than controls (τ = 53.8 ± 16.5 vs. 38.8 ± 7.6 s, respectively; p < 0.05). Q'(T), however, declined at similar rates (τ = 64.7 ± 18.8 vs. 73.0 ± 21.6 s; p > 0.05) being typically slower than [Formula: see text] in both groups. Importantly, Δ[deoxy-Hb + Mb] dynamics (MRT) were equal to, or faster than, τVO(2P) in patients and controls, respectively. In fact, there were no between-group differences in τVO(2P)MRTΔ[deoxy-Hb + Mb] (1.1 ± 0.4 vs. 1.0 ± 0.2, p > 0.05) thereby indicating similar rates of microvascular O(2) delivery. These data indicate that the slower rate of recovery of muscle metabolism after high-intensity exercise is not related to impaired microvascular O(2) delivery in patients with MM. This phenomenon, therefore, seems to reflect the intra-myocyte abnormalities that characterize this patient population.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.