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Effects of oxygen supplementation on cerebral oxygenation during exercise in chronic obstructive pulmonary disease patients not entitled to long-term oxygen therapy
Authors:Oliveira Mayron F  Rodrigues Miguel K  Treptow Erika  Cunha Thúlio M  Ferreira Eloara M V  Neder J Alberto
Institution:Pulmonary Function and Clinical Exercise Physiology Unit, Division of Respiratory Diseases, Department of Medicine, Federal University of Sao Paulo, Sao Paulo, Brazil.
Abstract:Background: The rate of change (Δ) in cerebral oxygenation (COx) during exercise is influenced by blood flow and arterial O2 content (CaO2). It is currently unclear whether ΔCOx would (i) be impaired during exercise in patients with chronic obstructive pulmonary disease (COPD) who do not fulfil the current criteria for long‐term O2 therapy but present with exercise‐induced hypoxaemia and (ii) improve with hyperoxia (FIO2 = 0·4) in this specific sub‐population. Methods: A total of 20 non‐hypercapnic men (FEV1 = 47·2 ± 11·5% pred) underwent incremental cycle ergometer exercise tests under normoxia and hyperoxia with ΔCOx (fold‐changes from unloaded exercise in O2Hb) being determined by near‐infrared spectroscopy. Pulse oximetry assessed oxyhaemoglobin saturation (SpO2), and impedance cardiography estimated changes in cardiac output (ΔQT). Results: Peak work rate and ΔCOx in normoxia were lower in eight O2‘desaturators’ compared with 12 ‘non‐desaturators’ (P<0·05). Area under ΔCOx during sub‐maximal exercise was closely related to SpO2 decrements in ‘desaturators’ (r = 0·92, P<0·01). These patients showed the largest improvement in peak exercise capacity with hyperoxia (P<0·05). Despite a trend to lower sub‐maximal ΔQT and mean arterial pressure with active intervention, ΔCOx was significantly improved only in this group (0·57 ± 0·20 versus 2·09 ± 0·42 for ‘non‐desaturators’ and ‘desaturators’, respectively; P<0·05). Conclusions: ΔCOx was impaired in non‐hypoxaemic patients with COPD who desaturated during exercise. Hyperoxic breathing was able to correct for these abnormalities, an effect related to enhanced CaO2 rather than improved central haemodynamics. This indicates that O2 supplementation ameliorates exercise COx in patients with COPD who are not currently entitled to ambulatory O2 therapy.
Keywords:blood flow  cerebral oxygenation  chronic obstructive pulmonary disease  exertion  near‐infrared spectroscopy  oxygen
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