Oxygen therapy improves cerebral oxygen delivery and neurovascular function in hypoxaemic chronic obstructive pulmonary disease patients.

Abstract

What is the central question of this study? How does oxygen therapy influence cerebral blood flow, cerebral oxygen delivery and neurovascular function in chronic obstructive pulmonary disease patients? What is the main finding and its importance? Oxygen therapy improves cerebral oxygen delivery and neurovascular function in chronic obstructive pulmonary disease patients. This improvement in cerebral oxygen delivery and neurovascular function might provide a physiological link between oxygen therapy and a reduced risk of cerebrovascular disease (e.g. stroke, mild cognitive impairment and dementia) in chronic obstructive pulmonary disease. We investigated the role of hypoxaemia in cerebral blood flow (CBF), oxygen delivery (CDO2 ) and neurovascular coupling (coupling of CBF to neural activity; NVC) in hypoxaemic chronic obstructive pulmonary disease (COPD) patients (n=14). Resting CBF (duplex ultrasound), peripheral oxyhaemoglobin saturation (SpO2; pulse-oximetry) and NVC (transcranial Doppler) were assessed before and after a 20min wash-in of supplemental oxygen (∼3lmin-1 ). The peripheral oxyhaemoglobin saturation increased from 91.0±3.3 to 97.4±3.0% (P<0.01), whereas CBF was unaltered (593.0±162.8 versus 590.1±138.5mlmin-1 ; P=0.91) with supplemental O2 . In contrast, both CDO2 (98.1±25.7versus 108.7±28.4mldl-1 ; P=0.02) and NVC were improved. Specifically, the posterior cerebral artery cerebrovascular conductance was increased to a greater extent after O2 normalization (+40%, from 20.4±9.9 to 28.0±10.4% increase in conductance; P=0.04), whereas the posterior cerebral artery cerebrovascular resistance decreased to a greater extent during O2 normalization (+22%, from -16.7±7.3 to -21.4±6.6% decrease in resistance; P=0.04). The cerebral vasculature of COPD patients appears insensitive to oxygen, because CBF was unaltered in response to O2 supplementation leading to improved CDO2 . In patients, the improvements in CDO2 and neurovascular function with supplemental O2 may underlie the cognitive benefits associated with O2 therapy.