Diagnostic and prognostic performance of Mxa and transfer function analysis-based dynamic cerebral autoregulation metrics

Abstract

Dynamic cerebral autoregulation is often assessed by continuously recorded arterial blood pressure (ABP) and transcranial Doppler-derived mean cerebral blood flow velocity followed by analysis in the time and frequency domain, respectively. Sequential correlation (in the time domain, yielding e.g., the measure mean flow index, Mxa) and transfer function analysis (TFA) (in the frequency domain, yielding, e.g., normalised and non-normalised gain as well as phase in the low frequency domain) are commonly used approaches. This study investigated the diagnostic and prognostic performance of these metrics. We included recordings from 48 healthy volunteers, 19 patients with sepsis, 36 with traumatic brain injury (TBI), and 14 patients admitted to a neurorehabilitation unit. The diagnostic (between healthy volunteers and patients) and prognostic performance (to predict death or poor functional outcome) of Mxa and the TFA measures were assessed by area under the receiver-operating characteristic (AUROC) curves. AUROC curves generally indicated that the measures were ‘no better than chance’ (AUROC ∼0.5) both for distinguishing between healthy volunteers and patient groups, and for predicting outcomes in our cohort. No metric emerged as superior for distinguishing between healthy volunteers and different patient groups, for assessing the effect of interventions, or for predicting mortality or functional outcome.

Effect of controlled blood pressure increase on cerebral blood flow velocity and oxygenation in patients with subarachnoid haemorrhage

“…Moreover, this study was limited by not having a direct measure of the dynamic cerebral autoregulation. Unfortunately, in studies run in parallel to the present study, we found the preplanned measure of cerebral autoregulation – mean flow index – to be unreliable and invalid 24–27 . Finally, as mentioned above we measured MCAv as a surrogate of global CBF.…”

“…Unfortunately, in studies run in parallel to the present study, we found the preplanned measure of cerebral autoregulationmean flow indexto be unreliable and invalid. [24][25][26][27] Finally, as mentioned above we measured MCAv as a surrogate of global CBF.…”

Myths and methodologies: Assessment of dynamic cerebral autoregulation by the mean flow index

“…Thus, in general higher values were measured ipsilateral to the injury; however, side differences were also reported in healthy volunteers (Yam et al, 2005) and patients without unilateral damage (Jochum et al, 2010;Reinhard et al, 2007). Of note, our expected behaviour is based on other methods, which are in their own way flawed or not thoroughly investigated in terms of physiolometrics (Claassen et al, 2021;Olsen, Riberholt, Plovsing et al, 2022), and furthermore do not correlate well with each other (Caldas et al, 2022;Ortega-Gutierrez et al, 2014;Pochard et al, 2020;Tzeng et al, 2012).…”

“…indicating that it has a limited value as a biomarker (Hartmann et al, 2023;Olsen, Riberholt, Plovsing et al, 2022).…”

“…According to the available data on the methodology as well as construct and criterion validity reviewed above, every step from raw data collection to the pre-processing approach and artefact handling as well as the choice of dichotomous threshold (if any) influences the conclusion that can be drawn regarding dCA when based on mean flow index methodology (Olsen, Riberholt, Plovsing et al, 2022).…”