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

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 20 min wash-in of supplemental oxygen (∼3 l min⁻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 ± 138.5 ml min⁻¹ ; P = 0.91) with supplemental O₂ . In contrast, both CDO₂ (98.1 ± 25.7 versus 108.7 ± 28.4 ml dl⁻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.