Cerebral oxygen availability during exercise in COPD patients with cognitive impairment

Abstract

Insufficient cerebral blood flow regulation to meet increasing metabolic demand during physical exertion could be associated with cognitive impairment. We compared cerebral oxygen availability during exercise in cognitively impaired (CI) to cognitively normal (CN) COPD patients.

Fifty-two patients (FEV1: 51 ± 16%) were classified as CN or CI according to the Montreal Cognitive Assessment. Patients performed cycle-ergometry at 75% peak capacity with continuous measurement of Near-Infrared Spectroscopy frontal-cortex Tissue oxygen Saturation Index (TSI), cerebral haemoglobin indices (oxy/deoxy/total- Hb), transcutaneous carbon-dioxide partial pressure (TcPCO2), and arterial oxygen saturation (SpO2).

Twenty-one patients (40%) presented evidences of CI. During exercise, CN and CI patients exhibited mild to moderate SpO2decline (nadir[Δ]≥ −3 ± 2% and −5 ± 3%, respectively) but preserved baseline frontal-cortex TSI levels, whilst presenting small TcPCO2 perturbations and increased cerebral total-Hb (post [Δ]≥ 2.0 ± 3 μM sec−1).

CI patients preserve the capacity to adequately maintain cerebral oxygen availability during submaximal exercise. Therefore, rehabilitative exercise training in CI patients with COPD exhibiting mild to moderate exercise-induced SpO2 decline does not appear to lead to reduced cerebral oxygen availability.