Effects of oxygen supplementation on cerebral oxygenation during exercise in chronic obstructive pulmonary disease patients not entitled to long-term oxygen therapy

Background: the rate of change (Delta) in cerebral oxygenation (COx) during exercise is influenced by blood flow and arterial O-2 content (CaO2). It is currently unclear whether Delta COx would (i) be impaired during exercise in patients with chronic obstructive pulmonary disease (COPD) who do not fulfil the current criteria for long-term O-2 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 Delta COx (fold-changes from unloaded exercise in O(2)Hb) being determined by near-infrared spectroscopy. Pulse oximetry assessed oxyhaemoglobin saturation (SpO(2)), and impedance cardiography estimated changes in cardiac output (Delta QT).Results: Peak work rate and Delta COx in normoxia were lower in eight O-2 'desaturators' compared with 12 'non-desaturators' (P<0.05). Area under Delta COx 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 Delta QT and mean arterial pressure with active intervention, Delta COx was significantly improved only in this group (0.57 +/- 0.20 versus 2.09 +/- 0.42 for 'non-desaturators' and 'desaturators', respectively; P