The Cognition and Flow Study: A Feasibility Randomized Controlled Trial of the Effects of Cognitive Training on Cerebral Blood Flow

Dynamics of the cerebral autoregulatory response to paced hyperventilation assessed using sub-component and time-varying analyses

Cerebral blood flow (CBF) can be altered by a change in partial pressure of arterial CO₂ (pCO₂), being reduced during hyperventilation (HPV). Critical closing pressure (CrCP) and resistance area product (RAP) are parameters which can be studied to understand this change, but their dynamic response has not been investigated during paced HPV (PHPV). Seventy five participants had recordings at rest and during PHPV. Blood pressure (BP) (Finometer), bilateral CBF velocity (CBFV) (transcranial Doppler), end-tidal CO₂ (capnography) and heart rate (HR) were recorded continuously. Subcomponent analysis (SCA) and time-varying CrCP, RAP and dynamic cerebral autoregulation (Autoregulation Index, ARI) were estimated comparing PHPV to poikilocapnia. PHPV caused a change in CBFV (p<0.01), EtCO₂, (p<0.01), HR (p<0.001) and RAP (p<0.01). SCA demonstrated RAP was the main parameter explaining the changes in CBFV due to PHPV. The time-varying step responses for CBFV and RAP during PHPV demonstrated considerable non-stationarity compared to poikilocapnia (p<0.00001). Although time-varying ARI was temporarily depressed, after 60 s of PHPV it was significantly higher (6.81 ± 1.88) (p<0.0001) than in poikilocapnia (5.08 ± 1.86). The mean plateau of the RAP step response was -98.3 ± 58.8 % 60 s after the onset of PHPV but -71.7 ± 45.0 % for poikilocapnia (p=0.0026), with no corresponding changes in CrCP (p=0.6). Further work is needed to assess the role of sex and aging in our findings, and the potential for using RAP and CrCP to improve the sensitivity and specificity of CO₂ reactivity studies in cerebrovascular conditions.

The Cognition and Flow Study (CogFlowS): A Mixed Method Evaluation of a Randomized Feasibility Trial of Cognitive Training in Dementia

Background: Cognitive training (CT) may be beneficial in delaying the onset or slowing dementia progression. CT has been evaluated quantitatively and qualitatively, but none have used mixed methods approaches. Objective: The aim of this study was to use a mixed methods approach to identify those who may selectively benefit from CT. Methods: This was an explanatory sequential mixed methods study involving a quantitative randomized trial of 12 weeks multi-domain CT in healthy older adults (HC, n = 20), and people living with mild cognitive impairment (MCI; n = 12) and dementia (n = 24). Quantitative outcomes included: cognition, mood, quality of life, and activities of daily living. 28 (10 HC, 6 MCI, 12 dementia) training participants completed semi-structured interviews with their carer. Quantitative and qualitative data were integrated using joint displays. Results: Three participants dropped out from the training early-on, leaving 25 participants with follow-up data for full integration (10 HC, 6 MCI, 9 dementia). Dropouts and lower adherence to training were more common in dementia participants with greater non-modifiable barriers. High adherers were more resilient to negative emotions, and poorer or fluctuating performance. Integrated analysis found the majority of participants (n = 24) benefited across outcomes, with no clear profile of individuals who benefited more than others. Participants made a number of key recommendations to improve adherence and minimize dropout to CT. Conclusion: Reasons for dropout and low adherence were identified, with recommendations provided for the design of CT for dementia. An individual approach to training should be adopted and low adherence should not preclude engagement with CT.

Transcranial Doppler Ultrasound for Monitoring the Cerebral Hemodynamic Changes and Prognosticating Outcomes in Venoarterial Extracorporeal Membrane-Oxygenated Patients

OBJECTIVE

Patients receiving venoarterial extracorporeal membrane oxygenation (VA-ECMO) support may have cerebral hemodynamic changes whose impact on patient outcome are not fully elucidated. This study aims to evaluate the correlation between cerebral hemodynamic changes and prognostic outcome in patients during VA-ECMO.

METHODS

Transcranial Doppler (TCD) ultrasound examination was performed to attain the systolic velocity (Vs), diastolic velocity (Vd), mean velocity (Vm), and pulsatility index (PI) of patients undergoing VA-ECMO. Cardiac ultrasound was also performed to assess the correlation between the left ventricular outflow tract velocity time integral (LVOT VTI), left ventricular ejection fraction (LVEF), and middle cerebral artery (MCA) with the systolic peak. Moreover, we assessed the predictive value of LVOT VTI and LVEF in patients with the systolic peak. Patients were divided into survival and death groups according to the 28-day survival period. Clinical data were compared between the two groups to investigate the effects of cerebral hemodynamic changes on the prognosis of VA-ECMO patients.

RESULTS

We found that the patient's LVOT VTI and LVEF had high predictive values for the systolic peak of the right middle cerebral artery. The initial LVEF, Vs, Vd and PI, and lactate level as well as the MODS incidence rate difference were significantly different between the survival and death groups. In addition, the results showed that the initial Vs value was an independent risk factor for the prognosis of patients undergoing VA-ECMO.

CONCLUSIONS

Cerebral hemodynamic changes may occur in patients supported by VA-ECMO. In addition, a poor cerebral arterial pulsatile blood flow was closely correlated with an unfavorable outcome in these patients.

Qualitative Analysis of the Cognition and Flow (CoGFlowS) Study: An Individualized Approach to Cognitive Training for Dementia Is Needed

BACKGROUND

Cognitive training (CT) may have benefits for both healthy older adults (HC) and those with early cognitive disorders [mild cognitive impairment (MCI) and dementia]. However, few studies have qualitatively evaluated home-based, computerized CT programs.

OBJECTIVE

We present the qualitative arm of a feasibility randomized controlled trial evaluating a CT program for HC and people living with MCI or dementia.

METHODS

Participants underwent semi-structured interviews after 12 weeks of CT. Where possible, participants were interviewed with their carers. The interview schedule and analysis were underpinned by the health belief model. Interviews were audio-recorded, transcribed, open-coded, and categorized into themes. The analytical framework was developed, and themes were condensed under five major categories: benefits, barriers, threat, self-efficacy, and cues to action.

RESULTS

37 participants underwent interviews. CT was feasible and acceptable to participants. Benefits included: enjoyment, improved awareness, benchmarking cognitive function, reassurance of abilities and giving back control. Barriers were more prevalent among those with dementia: problems with technology, frustration, conflict between patients and carers, apathy and lack of insight, anxiety or low mood, and lack of portability. HC and MCI perceived the severity of dementia risk as high, partially mitigated by CT. Participants living with dementia valued a more individualized approach to training, accounting for baseline characteristics.

CONCLUSION

CT was a feasible intervention for HC and people living with dementia and MCI. Benefits were present, but the identified barriers need to be addressed for CT to be implemented successfully.