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Uryga A, Czosnyka M, Robba C, Nasr N, Kasprowicz M. The time constant of the cerebral arterial bed: exploring age-related implications. J Clin Monit Comput 2024:10.1007/s10877-024-01142-5. [PMID: 38573368 DOI: 10.1007/s10877-024-01142-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2024] [Accepted: 02/17/2024] [Indexed: 04/05/2024]
Abstract
The time constant of the cerebral arterial bed (τ) represents an estimation of the transit time of flow from the point of insonation at the level of the middle cerebral artery to the arteriolar-capillary boundary, during a cardiac cycle. This study assessed differences in τ among healthy volunteers across different age groups. Simultaneous recordings of transcranial Doppler cerebral blood flow velocity (CBFV) and arterial blood pressure (ABP) were performed on two groups: young volunteers (below 30 years of age), and older volunteers (above 40 years of age). τ was estimated using mathematical transformation of ABP and CBFV pulse waveforms. 77 healthy volunteers [52 in the young group, and 25 in the old group] were included. Pulse amplitude of ABP was higher [16.7 (14.6-19.4) mmHg] in older volunteers as compared to younger ones [12.5 (10.9-14.4) mm Hg; p < 0.001]. CBFV was lower in older volunteers [59 (50-66) cm/s] as compared to younger ones [72 (63-78) cm/s p < 0.001]. τ was longer in the younger volunteers [217 (168-237) ms] as compared to the older volunteers [183 (149-211) ms; p = 0.004]. τ significantly decreased with age (rS = - 0.27; p = 0.018). τ is potentially an integrative marker of the changes occurring in cerebral vasculature, as it encompasses the interplay between changes in compliance and resistance that occur with age.
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Affiliation(s)
- Agnieszka Uryga
- Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370, Wroclaw, Poland.
| | - Marek Czosnyka
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK
| | - Chiara Robba
- IRCCS Policlinico San Martino, Genoa, Italy
- Department of Surgical Sciences and Integrated Diagnostics (DISC), University of Genoa, Viale Benedetto XV 16, Genoa, Italy
| | - Nathalie Nasr
- Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370, Wroclaw, Poland
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK
- IRCCS Policlinico San Martino, Genoa, Italy
- Department of Surgical Sciences and Integrated Diagnostics (DISC), University of Genoa, Viale Benedetto XV 16, Genoa, Italy
- Department of Neurology, Poitiers University Hospital, Poitiers, Laboratoire de Neurosciences Expérimentales et Cliniques, University of Poitiers, U1084, Poitiers, France
| | - Magdalena Kasprowicz
- Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370, Wroclaw, Poland
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Olsen MH, Riberholt CG, Berg RMG, Møller K. Myths and methodologies: Assessment of dynamic cerebral autoregulation by the mean flow index. Exp Physiol 2024; 109:614-623. [PMID: 38376110 PMCID: PMC10988760 DOI: 10.1113/ep091327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Accepted: 01/17/2024] [Indexed: 02/21/2024]
Abstract
The mean flow index-usually referred to as Mx-has been used for assessing dynamic cerebral autoregulation (dCA) for almost 30 years. However, concerns have arisen regarding methodological consistency, construct and criterion validity, and test-retest reliability. Methodological nuances, such as choice of input (cerebral perfusion pressure, invasive or non-invasive arterial pressure), pre-processing approach and artefact handling, significantly influence mean flow index values, and previous studies correlating mean flow index with other established dCA metrics are confounded by inherent methodological flaws like heteroscedasticity, while the mean flow index also fails to discriminate individuals with presumed intact versus impaired dCA (discriminatory validity), and its prognostic performance (predictive validity) across various conditions remains inconsistent. The test-retest reliability, both within and between days, is generally poor. At present, no single approach for data collection or pre-processing has proven superior for obtaining the mean flow index, and caution is advised in the further use of mean flow index-based measures for assessing dCA, as current evidence does not support their clinical application.
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Affiliation(s)
- Markus Harboe Olsen
- Department of Neuroanaesthesiology, The Neuroscience CentreCopenhagen University Hospital − RigshospitaletCopenhagenDenmark
| | - Christian Gunge Riberholt
- Department of Neuroanaesthesiology, The Neuroscience CentreCopenhagen University Hospital − RigshospitaletCopenhagenDenmark
- Department of Brain and Spinal Cord Injury, The Neuroscience CentreCopenhagen University Hospital − RigshospitaletCopenhagenDenmark
| | - Ronan M. G. Berg
- Department of Clinical Physiology and Nuclear MedicineCopenhagen University Hospital − RigshospitaletCopenhagenDenmark
- Centre for Physical Activity ResearchCopenhagen University Hospital − RigshospitaletCopenhagenDenmark
- Department of Biomedical Sciences, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
- Neurovascular Research Laboratory, Faculty of Life Sciences and EducationUniversity of South WalesPontypriddUK
| | - Kirsten Møller
- Department of Neuroanaesthesiology, The Neuroscience CentreCopenhagen University Hospital − RigshospitaletCopenhagenDenmark
- Department of Clinical Medicine, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
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Olsen MH, Riberholt C, Plovsing RR, Berg RMG, Møller K. Diagnostic and prognostic performance of Mxa and transfer function analysis-based dynamic cerebral autoregulation metrics. J Cereb Blood Flow Metab 2022; 42:2164-2172. [PMID: 36008917 PMCID: PMC9580178 DOI: 10.1177/0271678x221121841] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 07/19/2022] [Accepted: 07/29/2022] [Indexed: 11/16/2022]
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.
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Affiliation(s)
- Markus Harboe Olsen
- Department of Neuroanaesthesiology, Neuroscience Centre, Copenhagen University Hospital – Rigshospitalet, Denmark
| | - Christian Riberholt
- Department of Neuroanaesthesiology, Neuroscience Centre, Copenhagen University Hospital – Rigshospitalet, Denmark
- Department of Neurorehabilitation/Traumatic Brain Injury, Copenhagen University Hospital – Rigshospitalet, Denmark
| | - Ronni R Plovsing
- Department of Anaesthesia, Hvidovre Hospital, University of Copenhagen, Copenhagen, Denmark
- Institute of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Ronan MG Berg
- Department of Clinical Physiology, Nuclear Medicine & PET, Copenhagen University Hospital – Rigshospitalet, Denmark
- Centre for Physical Activity Research, Copenhagen University Hospital – Rigshospitalet, Denmark
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Pontypridd, UK
| | - Kirsten Møller
- Department of Neuroanaesthesiology, Neuroscience Centre, Copenhagen University Hospital – Rigshospitalet, Denmark
- Institute of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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Olsen MH, Riberholt CG, Mehlsen J, Berg RM, Møller K. Reliability and validity of the mean flow index (Mx) for assessing cerebral autoregulation in humans: A systematic review of the methodology. J Cereb Blood Flow Metab 2022; 42:27-38. [PMID: 34617816 PMCID: PMC8721771 DOI: 10.1177/0271678x211052588] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Cerebral autoregulation is a complex mechanism that serves to keep cerebral blood flow relatively constant within a wide range of cerebral perfusion pressures. The mean flow index (Mx) is one of several methods to assess dynamic cerebral autoregulation, but its reliability and validity have never been assessed systematically. The purpose of the present systematic review was to evaluate the methodology, reliability and validity of Mx.Based on 128 studies, we found inconsistency in the pre-processing of the recordings and the methods for calculation of Mx. The reliability in terms of repeatability and reproducibility ranged from poor to excellent, with optimal repeatability when comparing overlapping recordings. The discriminatory ability varied depending on the patient populations; in general, those with acute brain injury exhibited a higher Mx than healthy volunteers. The prognostic ability in terms of functional outcome and mortality ranged from chance result to moderate accuracy.Since the methodology was inconsistent between studies, resulting in varying reliability and validity estimates, the results were difficult to compare. The optimal method for deriving Mx is currently unknown.
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Affiliation(s)
- Markus Harboe Olsen
- Department of Neuroanaesthesiology, 53146Rigshospitalet, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Christian Gunge Riberholt
- Department of Neuroanaesthesiology, 53146Rigshospitalet, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.,Department of Neurorehabilitation/Traumatic Brain Injury Unit, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Jesper Mehlsen
- Surgical Pathophysiology Unit, 53146Rigshospitalet, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Ronan Mg Berg
- Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.,Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Pontypridd, UK
| | - Kirsten Møller
- Department of Neuroanaesthesiology, 53146Rigshospitalet, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.,Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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Zienkiewicz A, Favre M, Ferdinando H, Iring S, Serrador J, Myllylä T. Blood pressure wave propagation - a multisensor setup for cerebral autoregulation studies. Physiol Meas 2021; 42. [PMID: 34731844 DOI: 10.1088/1361-6579/ac3629] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 11/03/2021] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Cerebral autoregulation is critically important to maintain proper brain perfusion and supply the brain with oxygenated blood. Non-invasive measures of blood pressure (BP) are critical in assessing cerebral autoregulation. Wave propogation velocity may be a useful technique to estimate BP but the effect of the location of the sensors on the readings has not been thoroughly examined. In this paper, we were interested to study if propagation velocity of the pressure wave in the direction from the heart to the brain may differ compared with propagation from the heart to the periphery, as well as across different physiological tasks and/or health conditions. Using non-invasive sensors simultaneously placed on different locations of the human body allow for the study of how propagation velocity of the pressure wave, based on pulse transit time (PTT), varies across different directions. APPROACH We present multi-sensor BP wave propagation measurement setup aimed for cerebral autoregulation studies. The presented sensor setup consists of three sensors, one each placed on the neck, chest and finger, allowing simultaneous measurement of changes in BP propagation velocity towards the brain and to the periphery. We show how commonly tested physiological tasks affect the relative changes of PTT and correlations with BP. MAIN RESULTS We observed that during maximal blow, valsalva and breath hold breathing tasks, the relative changes of PTT were higher when PTT was measured in the direction from the heart to the brain than from the heart to the peripherals. In contrast, during a deep breathing task, the relative change in PTT from the heart to the brain was lower. In addition, we present a short literature review of PTT methods used in brain research. SIGNIFICANCE These preliminary data suggest that physiological task and direction of PTT measurement may affect relative PTT changes. Presented three-sensor setup provides an easy and neuroimaging compatible method for cerebral autoregulation studies by allowing to measure BP wave propagation velocity towards the brain vs. towards the periphery.
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Affiliation(s)
- Aleksandra Zienkiewicz
- Optoelectronics and Measurement Techniques Research Unit, University of Oulu, Oulu, FINLAND
| | - Michelle Favre
- Department of Pharmacology, Physiology & Neuroscience, Rutgers The State University of New Jersey, Newark, New Jersey, UNITED STATES
| | - Hany Ferdinando
- Research Unit of Medical Imaging, Physics and Technology, University of Oulu, Oulu, Pohjois-Pohjanmaa, FINLAND
| | - Stephanie Iring
- Department of Pharmacology, Physiology & Neuroscience, Rutgers The State University of New Jersey, Newark, New Jersey, UNITED STATES
| | - Jorge Serrador
- Department of Pharmacology, Physiology & Neuroscience, Rutgers The State University of New Jersey, Newark, New Jersey, UNITED STATES
| | - Teemu Myllylä
- Optoelectronics and Measurement Techniques Research Unit, University of Oulu, Oulu, FINLAND
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Kaczmarska K, Uryga A, Placek MM, Calviello L, Kasprowicz M, Varsos GV, Czosnyka Z, Koźniewska E, Sierzputowski T, Koszewski W, Czosnyka M. Critical closing pressure during experimental intracranial hypertension: comparison of three calculation methods. Neurol Res 2020; 42:387-397. [DOI: 10.1080/01616412.2020.1733323] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Katarzyna Kaczmarska
- Department of Neurosurgery, Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland
- Institute of Electronic Systems, Faculty of Electronics and Information Technology, Warsaw University of Technology, Warsaw, Poland
| | - Agnieszka Uryga
- Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland
| | - Michał M. Placek
- Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Leanne Calviello
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Magdalena Kasprowicz
- Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland
| | - Georgios V. Varsos
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Zofia Czosnyka
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Ewa Koźniewska
- Department of Neurosurgery, Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland
| | | | - Waldemar Koszewski
- Department of Neurosurgery, Second Faculty of Medicine, Medical University of Warsaw, Warsaw, Poland
| | - Marek Czosnyka
- Institute of Electronic Systems, Faculty of Electronics and Information Technology, Warsaw University of Technology, Warsaw, Poland
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
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Assessment of Baroreflex Sensitivity Using Time-Frequency Analysis during Postural Change and Hypercapnia. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2019; 2019:4875231. [PMID: 30863454 PMCID: PMC6377966 DOI: 10.1155/2019/4875231] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Revised: 12/16/2018] [Accepted: 01/06/2019] [Indexed: 01/09/2023]
Abstract
Baroreflex is a mechanism of short-term neural control responsible for maintaining stable levels of arterial blood pressure (ABP) in an ABP-heart rate negative feedback loop. Its function is assessed by baroreflex sensitivity (BRS)—a parameter which quantifies the relationship between changes in ABP and corresponding changes in heart rate (HR). The effect of postural change as well as the effect of changes in blood O2 and CO2 have been the focus of multiple previous studies on BRS. However, little is known about the influence of the combination of these two factors on dynamic baroreflex response. Furthermore, classical methods used for BRS assessment are based on the assumption of stationarity that may lead to unreliable results in the case of mostly nonstationary cardiovascular signals. Therefore, we aimed to investigate BRS during repeated transitions between squatting and standing in normal end-tidal CO2 (EtCO2) conditions (normocapnia) and conditions of progressively increasing EtCO2 with a decreasing level of O2 (hypercapnia with hypoxia) using joint time and frequency domain (TF) approach to BRS estimation that overcomes the limitation of classical methods. Noninvasive continuous measurements of ABP and EtCO2 were conducted in a group of 40 healthy young volunteers. The time course of BRS was estimated from TF representations of pulse interval variability and systolic pressure variability, their coherence, and phase spectra. The relationship between time-variant BRS and indices of ABP and HR was analyzed during postural change in normocapnia and hypercapnia with hypoxia. In normocapnia, observed trends in all measures were in accordance with previous studies, supporting the validity of presented TF method. Similar but slightly attenuated response to postural change was observed in hypercapnia with hypoxia. Our results show the merits of the nonstationary methods as a tool to study the cardiovascular system during short-term hemodynamic changes.
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Uryga A, Kasprowicz M, Burzyńska M, Calviello L, Kaczmarska K, Czosnyka M. Cerebral arterial time constant calculated from the middle and posterior cerebral arteries in healthy subjects. J Clin Monit Comput 2018; 33:605-613. [PMID: 30291539 DOI: 10.1007/s10877-018-0207-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 10/01/2018] [Indexed: 10/28/2022]
Abstract
The cerebral arterial blood volume changes (∆CaBV) during a single cardiac cycle can be estimated using transcranial Doppler ultrasonography (TCD) by assuming pulsatile blood inflow, constant, and pulsatile flow forward from large cerebral arteries to resistive arterioles [continuous flow forward (CFF) and pulsatile flow forward (PFF)]. In this way, two alternative methods of cerebral arterial compliance (Ca) estimation are possible. Recently, we proposed a TCD-derived index, named the time constant of the cerebral arterial bed (τ), which is a product of Ca and cerebrovascular resistance and is independent of the diameter of the insonated vessel. In this study, we aim to examine whether the τ estimated by either the CFF or the PFF model differs when calculated from the middle cerebral artery (MCA) and the posterior cerebral artery (PCA). The arterial blood pressure and TCD cerebral blood flow velocity (CBFVa) in the MCA and in the PCA were non-invasively measured in 32 young, healthy volunteers (median age: 24, minimum age: 18, maximum age: 31). The τ was calculated using both the PFF and CFF models from the MCA and the PCA and compared using a non-parametric Wilcoxon signed-rank test. Results are presented as medians (25th-75th percentiles). The cerebrovascular time constant estimated in both arteries using the PFF model was shorter than when using the CFF model (ms): [64.83 (41.22-104.93) vs. 178.60 (160.40-216.70), p < 0.001 in the MCA, and 44.04 (17.15-81.17) vs. 183.50 (153.65-204.10), p < 0.001 in the PCA, respectively]. The τ obtained using the PFF model was significantly longer from the MCA than from the PCA, p = 0.004. No difference was found in the τ when calculated using the CFF model. Longer τ from the MCA might be related to the higher Ca of the MCA than that of the PCA. Our results demonstrate MCA-PCA differences in the τ, but only when the PFF model was applied.
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Affiliation(s)
- Agnieszka Uryga
- Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370, Wrocław, Poland.
| | - Magdalena Kasprowicz
- Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370, Wrocław, Poland
| | - Małgorzata Burzyńska
- Department of Anesthesiology and Intensive Care, Wroclaw Medical University, Wrocław, Poland
| | - Leanne Calviello
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Katarzyna Kaczmarska
- Department of Neurosurgery, Mossakowski Medical Research Centre Polish Academy of Sciences, Warsaw, Poland.,Institute of Electronic Systems, Faculty of Electronics and Information Technology, Warsaw University of Technology, Warsaw, Poland
| | - Marek Czosnyka
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.,Institute of Electronic Systems, Faculty of Electronics and Information Technology, Warsaw University of Technology, Warsaw, Poland
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