Feasibility of Integrated Transcranial Doppler Ultrasound-Near-Infrared Spectroscopy to Measure Cerebral Haemodynamics in Dementia, Delirium, and Depression (the VESPAR Project): A Pilot Study

Transcranial Doppler ultrasonography (TCD) and near-infrared spectroscopy (NIRS) are indirect measures of neurovascular coupling (NVC). No studies have assessed the feasibility of an integrated TCD-NIRS approach to measure NVC in patients with dementia, delirium, and depression. TCD-NIRS was trialled in 10 healthy volunteers, 11 patients with depression, 8 with dementia, and 5 with delirium. Participants underwent continuous cerebral blood velocity measurements, measured from the dominant middle cerebral artery (MCAv) and non-dominant posterior cerebral artery (PCAv), at rest and in response to four cognitive tasks. Heart rate (HR), end-tidal carbon dioxide (EtCO 2 ), blood pressure (BP), prefrontal oxygenated (HbO 2 ) and deoxygenated (HbR) haemoglobin levels were measured. Resting mean MCAv differed significantly between groups (healthy volunteers: 53.9 (SD=8.09) cm/s, depression: 41.9 (9.31) cm/s ( p =0.041), dementia: 42.5 (13.7) cm/s, (0.150) delirium: 32.6 (7.48) cm/s ( p =0.002), after correction for age and BP ( p =0.012). There were no significant differences in resting PCAv, BP, EtCO 2 , HR, or prefrontal oxygenation. Participants with delirium were unable to complete the task-activated section of the protocol. All four tasks evoked indirect changes in NVC in healthy volunteers, and in patients with depression and dementia; only HbR differed in the depression group relative to the dementia group ( p =0.021). Comparison with existing methods While these techniques have been used individually in the different patient groups, they have not been used in conjunction to assess differences in NVC between all three groups. An integrated TCD-NIRS protocol in this pilot study was feasible in these patient groups to measure NVC, but not in delirium. • Dementia, delirium, and depression are common in older people and often co-exist. • Changes in cerebral haemodynamics are common in all three disorders. • Resting cerebral blood velocity was reduced in dementia, depression, and delirium. • Cerebral blood velocity was not different between groups with task activation. • This study was feasible in depression but was amended for dementia and delirium.