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Uryga A, Kasprowicz M, Budohoski K, Nasr N, Czosnyka M. Predictive value of cerebrovascular time constant for delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage. J Cereb Blood Flow Metab 2024; 44:1208-1217. [PMID: 38295872 PMCID: PMC11179618 DOI: 10.1177/0271678x241228512] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 12/06/2023] [Accepted: 01/02/2024] [Indexed: 06/13/2024]
Abstract
Time constant of the cerebral arterial bed (τ) is a transcranial Doppler (TCD) based metric that is expected to quantify the transit time of red blood cells from the insonation point to the arteriole-capillary boundary during a cardiac cycle. This study aims to assess the potential of τ as an early predictor of delayed cerebral ischemia (DCI). Consecutive patients (56 ± 15 years) treated for aneurysmal subarachnoid haemorrhage were included in the study. τ was assessed through a modelling approach that involved simultaneous recordings of arterial blood pressure and cerebral blood flow velocity (CBFV) from TCD's first recordings. 71 patients were included. 17 patients experienced DCI. τ was significantly shorter in patients who later developed DCI: 187 ± 64 ms vs. 249 ± 184 ms; p = 0.040 with moderate effect size (rG = 0.24). Logistic regression showed that there was a significant association between increased CBFV, shortened τ, and the development of DCI (χ2 = 11.54; p = 0.003) with AUC for the model 0.75. Patients who had both shortened τ and increased CBFV were 20 times more likely to develop DCI (OR = 20.4 (2.2-187.7)). Our results suggest that early alterations in τ are associated with DCI after aSAH. The highest performance of the model including both CBFV and τ may suggest the importance of both macrovascular and microvascular changes assessment.
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Affiliation(s)
- Agnieszka Uryga
- Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland
| | - Magdalena Kasprowicz
- Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland
| | - Karol Budohoski
- Department of Neurosurgery, Clinical Neurosciences Center, University of Utah, Salt Lake City, Utah, USA
- Department of Neurosurgery, University of Utah, Salt Lake City, Utah, USA
| | - Nathalie Nasr
- Department of Neurology, Poitiers University Hospital, Laboratoire de Neurosciences Expérimentales et Cliniques, University of Poitiers, Poitiers, France
| | - Marek Czosnyka
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke’s Hospital, University of Cambridge, Cambridge, UK
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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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Stickland RC, Zvolanek KM, Moia S, Ayyagari A, Caballero-Gaudes C, Bright MG. A practical modification to a resting state fMRI protocol for improved characterization of cerebrovascular function. Neuroimage 2021; 239:118306. [PMID: 34175427 PMCID: PMC8552969 DOI: 10.1016/j.neuroimage.2021.118306] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 06/18/2021] [Accepted: 06/23/2021] [Indexed: 12/22/2022] Open
Abstract
Cerebrovascular reactivity (CVR), defined here as the Blood Oxygenation Level Dependent (BOLD) response to a CO2 pressure change, is a useful metric of cerebrovascular function. Both the amplitude and the timing (hemodynamic lag) of the CVR response can bring insight into the nature of a cerebrovascular pathology and aid in understanding noise confounds when using functional Magnetic Resonance Imaging (fMRI) to study neural activity. This research assessed a practical modification to a typical resting-state fMRI protocol, to improve the characterization of cerebrovascular function. In 9 healthy subjects, we modelled CVR and lag in three resting-state data segments, and in data segments which added a 2–3 minute breathing task to the start of a resting-state segment. Two different breathing tasks were used to induce fluctuations in arterial CO2 pressure: a breath-hold task to induce hypercapnia (CO2 increase) and a cued deep breathing task to induce hypocapnia (CO2 decrease). Our analysis produced voxel-wise estimates of the amplitude (CVR) and timing (lag) of the BOLD-fMRI response to CO2 by systematically shifting the CO2 regressor in time to optimize the model fit. This optimization inherently increases gray matter CVR values and fit statistics. The inclusion of a simple breathing task, compared to a resting-state scan only, increases the number of voxels in the brain that have a significant relationship between CO2 and BOLD-fMRI signals, and improves our confidence in the plausibility of voxel-wise CVR and hemodynamic lag estimates. We demonstrate the clinical utility and feasibility of this protocol in an incidental finding of Moyamoya disease, and explore the possibilities and challenges of using this protocol in younger populations. This hybrid protocol has direct applications for CVR mapping in both research and clinical settings and wider applications for fMRI denoising and interpretation.
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Affiliation(s)
- Rachael C Stickland
- Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States.
| | - Kristina M Zvolanek
- Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States; Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, IL, United States
| | - Stefano Moia
- Basque Center on Cognition, Brain and Language, Donostia, Gipuzkoa, Spain; University of the Basque Country EHU/UPV, Donostia, Gipuzkoa, Spain
| | - Apoorva Ayyagari
- Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States; Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, IL, United States
| | | | - Molly G Bright
- Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States; Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, IL, United States
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Papaioannou VE, Budohoski KP, Placek MM, Czosnyka Z, Smielewski P, Czosnyka M. Association of transcranial Doppler blood flow velocity slow waves with delayed cerebral ischemia in patients suffering from subarachnoid hemorrhage: a retrospective study. Intensive Care Med Exp 2021; 9:11. [PMID: 33768351 PMCID: PMC7994457 DOI: 10.1186/s40635-021-00378-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Accepted: 02/17/2021] [Indexed: 11/25/2022] Open
Abstract
Background Cerebral vasospasm (VS) and delayed cerebral ischemia (DCI) constitute major complications following subarachnoid hemorrhage (SAH). A few studies have examined the relationship between different indices of cerebrovascular dynamics with the occurrence of VS. However, their potential association with the development of DCI remains elusive. In this study, we investigated the pattern of changes of different transcranial Doppler (TCD)-derived indices of cerebrovascular dynamics during vasospasm in patients suffering from subarachnoid hemorrhage, dichotomized by the presence of delayed cerebral ischemia. Methods A retrospective analysis was performed using recordings from 32 SAH patients, diagnosed with VS. Patients were divided in two groups, depending on development of DCI. Magnitude of slow waves (SWs) of cerebral blood flow velocity (CBFV) was measured. Cerebral autoregulation was estimated using the moving correlation coefficient Mxa. Cerebral arterial time constant (tau) was expressed as the product of resistance and compliance. Complexity of CBFV was estimated through measurement of sample entropy (SampEn). Results In the whole population (N = 32), magnitude of SWs of ipsilateral to VS side CBFV was higher during vasospasm (4.15 ± 1.55 vs before: 2.86 ± 1.21 cm/s, p < 0.001). Ipsilateral SWs of CBFV before VS had higher magnitude in DCI group (N = 19, p < 0.001) and were strongly predictive of DCI, with area under the curve (AUC) = 0.745 (p = 0.02). Vasospasm caused a non-significant shortening of ipsilateral values of tau and increase in SampEn in all patients related to pre-VS measurements, as well as an insignificant increase of Mxa in DCI related to non-DCI group (N = 13). Conclusions In patients suffering from subarachnoid hemorrhage, TCD-detected VS was associated with higher ipsilateral CBFV SWs, related to pre-VS measurements. Higher CBFV SWs before VS were significantly predictive of delayed cerebral ischemia.
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Affiliation(s)
- Vasilios E Papaioannou
- Department of Intensive Care Medicine, Alexandroupolis Hospital, Democritus University of Thrace, 68100, Alexandoupolis, Greece. .,Academic Neurosurgery Unit, Brain Physics Lab, Addenbrooke's Hospital, Box 167, Cambridge, CB20QQ, UK.
| | - Karol P Budohoski
- Academic Neurosurgery Unit, Brain Physics Lab, Addenbrooke's Hospital, Box 167, Cambridge, CB20QQ, UK.,Department of Neurosurgery, Cambridge University Hospitals, Cambridge, CB20QQ, UK
| | - Michal M Placek
- Academic Neurosurgery Unit, Brain Physics Lab, Addenbrooke's Hospital, Box 167, Cambridge, CB20QQ, UK.,Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wrocław University of Science and Technology, 50-370, Wrocław, Poland
| | - Zofia Czosnyka
- Academic Neurosurgery Unit, Brain Physics Lab, Addenbrooke's Hospital, Box 167, Cambridge, CB20QQ, UK
| | - Peter Smielewski
- Academic Neurosurgery Unit, Brain Physics Lab, Addenbrooke's Hospital, Box 167, Cambridge, CB20QQ, UK
| | - Marek Czosnyka
- Academic Neurosurgery Unit, Brain Physics Lab, Addenbrooke's Hospital, Box 167, Cambridge, CB20QQ, UK
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Uryga A, Kaczmarska K, Burzyńska M, Czosnyka M, Kasprowicz M. A comparison of the time constant of the cerebral arterial bed using invasive and non-invasive arterial blood pressure measurements. Physiol Meas 2020; 41:075001. [PMID: 32526728 DOI: 10.1088/1361-6579/ab9bb6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE The time constant of the cerebral arterial bed (τ), which is an index of brain haemodynamics, can be estimated in patients using continuous monitoring of arterial blood pressure (ABP), transcranial Doppler cerebral blood flow velocity (CBFV) and intracranial pressure (ICP) if these measures are available. But, in some clinical scenarios invasive measurement of ABP is not feasible. Therefore, in this study we aimed to investigate whether invasive ABP can be replaced with non-invasive ABP, monitored using the Finapres photoplethysmograph (fABP). APPROACH Forty-six recordings of ICP, ABP, fABP, and CBFV in the right and left middle cerebral arteries were performed daily for approximately 30 min in 10 head injury patients. Two modelling approaches (constant flow forward [CFF, pulsatile blood inflow and steady blood outflow] and pulsatile flow forward [PFF, where both blood inflow and outflow are pulsatile]) were applied to estimate τ using either invasive ABP (τCFF, τPFF) or non-invasive ABP (fτCFF, fτPFF). MAIN RESULTS Bland-Altman analysis showed quite poor agreement between the fτ and τ methods of estimation. The fτ method produced significantly higher values than the τ method when calculated using both the CFF and PFF models (p < .001 for both). The correlation between fτCFF and τCFF was moderately high (r s = 0.63; p < .001), whereas that between fτPFF and τPFF was weaker (r s = 0.40; p = .009). SIGNIFICANCE Our results suggest that using non-invasive ABP for estimation of τ is inaccurate in head injury patients.
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Affiliation(s)
- Agnieszka Uryga
- Department of Biomedical Engineering, Wroclaw University of Science and Technology, Wroclaw, Poland
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Sahinovic MM, Vos JJ, Scheeren TWL. Journal of Clinical Monitoring and Computing 2019 end of year summary: monitoring tissue oxygenation and perfusion and its autoregulation. J Clin Monit Comput 2020; 34:389-395. [PMID: 32277310 PMCID: PMC7205776 DOI: 10.1007/s10877-020-00504-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 03/25/2020] [Indexed: 12/30/2022]
Abstract
Tissue perfusion monitoring is increasingly being employed clinically in a non-invasive fashion. In this end-of-year summary of the Journal of Clinical Monitoring and Computing, we take a closer look at the papers published recently on this subject in the journal. Most of these papers focus on monitoring cerebral perfusion (and associated hemodynamics), using either transcranial doppler measurements or near-infrared spectroscopy. Given the importance of cerebral autoregulation in the analyses performed in most of the studies discussed here, this end-of-year summary also includes a short description of cerebral hemodynamic physiology and its autoregulation. Finally, we review articles on somatic tissue oxygenation and its possible association with outcome.
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Affiliation(s)
- M M Sahinovic
- Department of Anesthesiology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, PO Box 30001, 9700RB, Groningen, Netherlands
| | - J J Vos
- Department of Anesthesiology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, PO Box 30001, 9700RB, Groningen, Netherlands
| | - T W L Scheeren
- Department of Anesthesiology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, PO Box 30001, 9700RB, Groningen, Netherlands.
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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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The Сerebrovascular Time Constant in Patients with Head Injury and Posttraumatic Cerebral Vasospasm. ACTA NEUROCHIRURGICA. SUPPLEMENT 2019. [PMID: 31407084 DOI: 10.1007/978-3-030-04615-6_30] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register]
Abstract
The aim of the study was to assess the time constant of cerebral arterial bed in TBI patients with cerebral vasospasm (CVS) with and without intracranial hematomas (ICH).We examined 84 patients with severe TBI (mean 35 ± 15 years, 53 men and 31 women). The first group included 41 patients without ICH and the second group included 43 patients with epidural (7) and subdural (36) hematomas.Perfusion computed tomography (PCT) was performed in 1-12 days after TBI in the first group and in 2-8 days after craniotomy in the second group. Arteriovenous amplitude of regional cerebral blood volume oscillation was calculated as the difference of arterial and venous blood volume in the "region of interest." Mean arterial pressure was measured and the flow rate of middle cerebral artery was recorded with Transcranial Doppler after PCT. Time constant was calculated by the formula modificated by M. Kasprowicz. Results and Conclusion: The τ was shorter (p < 0.005) in both first and second group in comparison with normal values. The τ in the second group on ipsilateral side former hematoma with CVS was shorter than in the first group and in the second group on contralateral side former hematoma without CVS (р = 0.024).
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Observed and calculated cerebral critical closing pressure are highly correlated in preterm infants. Pediatr Res 2019; 86:242-246. [PMID: 31003233 PMCID: PMC6658334 DOI: 10.1038/s41390-019-0403-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 04/04/2019] [Accepted: 04/11/2019] [Indexed: 11/28/2022]
Abstract
BACKGROUND Cerebrovascular critical closing pressure (CrCP) is the arterial blood pressure (ABP) at which cerebral blood flow ceases. Preterm ABP is low and close to CrCP. The diastolic closing margin (diastolic ABP minus CrCP) has been associated with intraventricular hemorrhage in preterm infants. CrCP is estimated from middle cerebral artery cerebral blood flow velocity (CBFV) and ABP waveforms. However, these estimations have not been validated due to a lack of gold standard. Direct observation of the CrCP in preterm infants with hypotension is an opportunity to validate synchronously estimated CrCP. METHODS ABP and CBFV tracings were obtained from 24 extremely low birth weight infants. Recordings where diastolic CBFV was zero were identified. The gold standard CrCP was delineated using piecewise regression of ABP and CBFV values paired by rank ordering and then estimated using a published formula. The measured and estimated values were compared using linear regression and Bland-Altman analysis. RESULTS Linear regression showed a high degree of correlation between measured and calculated CrCP (r2 = 0.93). CONCLUSIONS This is the first study to validate a calculated CrCP by comparing it to direct measurements of CrCP from preterm infants when ABP is lower than CrCP.
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Puppo C, Kasprowicz M, Steiner LA, Yelicich B, Lalou DA, Smielewski P, Czosnyka M. Hypocapnia after traumatic brain injury: how does it affect the time constant of the cerebral circulation? J Clin Monit Comput 2019; 34:461-468. [PMID: 31175502 PMCID: PMC7223592 DOI: 10.1007/s10877-019-00331-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2019] [Accepted: 05/30/2019] [Indexed: 11/09/2022]
Abstract
The time constant of the cerebral arterial bed (“tau”) estimates how fast the blood entering the brain fills the arterial vascular sector. Analogous to an electrical resistor–capacitor circuit, it is expressed as the product of arterial compliance (Ca) and cerebrovascular resistance (CVR). Hypocapnia increases the time constant in healthy volunteers and decreases arterial compliance in head trauma. How the combination of hyocapnia and trauma affects this parameter has yet to be studied. We hypothesized that in TBI patients the intense vasoconstrictive action of hypocapnia would dominate over the decrease in compliance seen after hyperventilation. The predominant vasoconstrictive response would maintain an incoming blood volume in the arterial circulation, thereby lengthening tau. We retrospectively analyzed recordings of intracranial pressure (ICP), arterial blood pressure (ABP), and blood flow velocity (FV) obtained from a cohort of 27 severe TBI patients [(39/30 years (median/IQR), 5 women; admission GCS 6/5 (median/IQR)] studied during a standard clinical CO2 reactivity test. The reactivity test was performed by means of a 50-min increase in ventilation (20% increase in respiratory minute volume). CVR and Ca were estimated from these recordings, and their product calculated to find the time constant. CVR significantly increased [median CVR pre-hypocapnia/during hypocapnia: 1.05/1.35 mmHg/(cm3/s)]. Ca decreased (median Ca pre-hypocapnia/during hypocapnia: 0.130/0.124 arbitrary units) to statistical significance (p = 0.005). The product of these two parameters resulted in a significant prolongation of the time constant (median tau pre-hypocapnia/during hypocapnia: 0.136 s/0.152 s, p ˂ .001). Overall, the increase in CVR dominated over the decrease in compliance, hence tau was longer. We demonstrate a significant increase in the time constant of the cerebral circulation during hypocapnia after severe TBI, and attribute this to an increase in cerebrovascular resistance which outweighs the decrease in cerebral arterial bed compliance.
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Affiliation(s)
- Corina Puppo
- Intensive Care Unit, Hospital de Clinicas, Universidad de la Republica, Av. Italia s/n, 11600, Montevideo, Uruguay.
| | - Magdalena Kasprowicz
- Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, wybrzeże Stanisława Wyspiańskiego 27, 50-370, Wroclaw, Poland
| | - Luzius A Steiner
- Surgical Intensive Care, Prehospital Emergency Medicine and Pain Therapy, University Hospital Basel, University of Basel, Spitalstrasse 21, 4031, Basel, Switzerland
| | - Bernardo Yelicich
- Intensive Care Unit, Hospital de Clinicas, Universidad de la Republica, Av. Italia s/n, 11600, Montevideo, Uruguay
| | - Despina Afrodite Lalou
- Division of Academic Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Hills Rd, Cambridge, CB2 0QQ, UK
| | - Peter Smielewski
- Division of Academic Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Hills Rd, Cambridge, CB2 0QQ, UK
| | - Marek Czosnyka
- Division of Academic Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Hills Rd, Cambridge, CB2 0QQ, UK
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Tgavalekos K, Pham T, Krishnamurthy N, Sassaroli A, Fantini S. Frequency-resolved analysis of coherent oscillations of local cerebral blood volume, measured with near-infrared spectroscopy, and systemic arterial pressure in healthy human subjects. PLoS One 2019; 14:e0211710. [PMID: 30753203 PMCID: PMC6372153 DOI: 10.1371/journal.pone.0211710] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Accepted: 01/19/2019] [Indexed: 01/18/2023] Open
Abstract
We report a study on twenty-two healthy human subjects of the dynamic relationship between cerebral hemoglobin concentration ([HbT]), measured with near-infrared spectroscopy (NIRS) in the prefrontal cortex, and systemic arterial blood pressure (ABP), measured with finger plethysmography. [HbT] is a measure of local cerebral blood volume (CBV). We induced hemodynamic oscillations at discrete frequencies in the range 0.04-0.20 Hz with cyclic inflation and deflation of pneumatic cuffs wrapped around the subject's thighs. We modeled the transfer function of ABP and [HbT] in terms of effective arterial (K(a)) and venous (K(v)) compliances, and a cerebral autoregulation time constant (τ(AR)). The mean values (± standard errors) of these parameters across the twenty-two subjects were K(a) = 0.01 ± 0.01 μM/mmHg, K(v) = 0.09 ± 0.05 μM/mmHg, and τ(AR) = 2.2 ± 1.3 s. Spatially resolved measurements in a subset of eight subjects reveal a spatial variability of these parameters that may exceed the inter-subject variability at a set location. This study sheds some light onto the role that ABP and cerebral blood flow (CBF) play in the dynamics of [HbT] measured with NIRS, and paves the way for new non-invasive optical studies of cerebral blood flow and cerebral autoregulation.
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Affiliation(s)
- Kristen Tgavalekos
- Department of Biomedical Engineering, Tufts University, Medford, Massachusetts, United States of America
| | - Thao Pham
- Department of Biomedical Engineering, Tufts University, Medford, Massachusetts, United States of America
| | - Nishanth Krishnamurthy
- Department of Biomedical Engineering, Tufts University, Medford, Massachusetts, United States of America
| | - Angelo Sassaroli
- Department of Biomedical Engineering, Tufts University, Medford, Massachusetts, United States of America
| | - Sergio Fantini
- Department of Biomedical Engineering, Tufts University, Medford, Massachusetts, United States of America
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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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13
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Schaafsma A. A new method for correcting middle cerebral artery flow velocity for age by calculating Z-scores. J Neurosci Methods 2018; 307:1-7. [DOI: 10.1016/j.jneumeth.2018.06.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2018] [Revised: 06/13/2018] [Accepted: 06/15/2018] [Indexed: 10/14/2022]
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14
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Uryga A, Kasprowicz M, Calviello L, Diehl RR, Kaczmarska K, Czosnyka M. Assessment of cerebral hemodynamic parameters using pulsatile versus non-pulsatile cerebral blood outflow models. J Clin Monit Comput 2018; 33:85-94. [DOI: 10.1007/s10877-018-0136-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 03/29/2018] [Indexed: 11/28/2022]
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15
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Cerebral Critical Closing Pressure: Is the Multiparameter Model Better Suited to Estimate Physiology of Cerebral Hemodynamics? Neurocrit Care 2017; 25:446-454. [PMID: 27389005 DOI: 10.1007/s12028-016-0288-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
BACKGROUND Cerebral critical closing pressure (CrCP) is the level of arterial blood pressure (ABP) at which small brain vessels close and blood flow stops. This value is always greater than intracranial pressure (ICP). The difference between CrCP and ICP is explained by the tone of the small cerebral vessels (wall tension). CrCP value is used in several dynamic cerebral autoregulation models. However, the different methods for calculation of CrCP show frequent negative values. These findings are viewed as a methodological limitation. We intended to evaluate CrCP in patients with severe traumatic brain injury (TBI) with a new multiparameter impedance-based model and compare it with results found earlier using a transcranial Doppler (TCD)-ABP pulse waveform-based method. METHODS Twelve severe TBI patients hospitalized during September 2005-May 2007. Ten men, mean age 32 years (16-61). Four had decompressive craniectomies (DC); three presented anisocoria. Patients were monitored with TCD cerebral blood flow velocity (FV), invasive ABP, and ICP. Data were acquired at 50 Hz with an in-house developed data acquisition system. We compared the earlier studied "first harmonic" method (M1) results with results from a new recently developed (M2) "multiparameter method." RESULTS M1: In seven patients CrCP values were negative, reaching -150 mmHg. M2: All positive values; only one lower than ICP (ICP 60 mmHg/ CrCP 57 mmHg). There was a significant difference between M1 and M2 values (M1 < M2) and between ICP and M2 (M2 > ICP). CONCLUSION M2 results in positive values of CrCP, higher than ICP, and are physiologically interpretable.
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Trofimov A, Kalentiev G, Gribkov A, Voennov O, Grigoryeva V. Cerebrovascular Time Constant in Patients with Head Injury. ACTA NEUROCHIRURGICA. SUPPLEMENT 2017; 121:295-7. [PMID: 26463964 DOI: 10.1007/978-3-319-18497-5_51] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
The cerebrovascular time constant (τ) theoretically estimates how fast the cerebral arterial bed is filled by blood volume after a sudden change in arterial blood pressure during one cardiac cycle. The aim of this study was to assess the time constant of the cerebral arterial bed in patients with traumatic brain injury (TBI) with and without intracranial hematomas (IH). We examined 116 patients with severe TBI (mean 35 ± 15 years, 61 men, 55 women). The first group included 58 patients without IH and the second group included 58 patients with epidural (7), subdural (48), and multiple (3) hematomas. Perfusion computed tomography (PCT) was performed 1-12 days after TBI in the first group and 2-8 days after surgical evacuation of the hematoma in the second group. Arteriovenous amplitude of regional cerebral blood volume oscillation was calculated as the difference between arterial and venous blood volume in the "region of interest" of 1 cm(2). Mean arterial pressure was measured and the flow rate of the middle cerebral artery was recorded with transcranial Doppler ultrasound after PCT. The time constant was calculated by the formula modified by Kasprowicz. The τ was shorter (p = 0.05) in both groups 1 and 2 in comparison with normal data. The time constant in group 2 was shorter than in group 1, both on the side of the former hematoma (р = 0.012) and on the contralateral side (р = 0.044). The results indicate failure of autoregulation of cerebral capillary blood flow in severe TBI, which increases in patients with polytrauma and traumatic IH.
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MESH Headings
- Adolescent
- Adult
- Aged
- Arterial Pressure
- Cerebrovascular Circulation
- Female
- Hematoma, Epidural, Cranial/diagnostic imaging
- Hematoma, Epidural, Cranial/physiopathology
- Hematoma, Subdural, Intracranial/diagnostic imaging
- Hematoma, Subdural, Intracranial/physiopathology
- Humans
- Intracranial Hemorrhages/diagnostic imaging
- Intracranial Hemorrhages/physiopathology
- Male
- Middle Aged
- Middle Cerebral Artery/diagnostic imaging
- Middle Cerebral Artery/physiopathology
- Perfusion Imaging
- Time Factors
- Tomography, X-Ray Computed
- Ultrasonography, Doppler, Transcranial
- Vascular Resistance
- Young Adult
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Affiliation(s)
- Alex Trofimov
- Department of Polytrauma and Critical Care, Regional Hospital named after N.A. Semashko, 190, Rodionov str, Nizhny Novgorod, 603126, Russian Federation.
- Department of Neurosurgery, Nizhniy Novgorod State Medical Academy, Nizhniy Novgorod, Russian Federation.
| | - George Kalentiev
- Department of Critical Care, Regional Hospital named after N.A. Semashko, 190, Rodionov str, Nizhniy Novgorod, Russian Federation
| | - Alexander Gribkov
- Department of Critical Care, Regional Hospital named after N.A. Semashko, 190, Rodionov str, Nizhniy Novgorod, Russian Federation
| | - Oleg Voennov
- Department of Critical Care, Regional Hospital named after N.A. Semashko, 190, Rodionov str, Nizhniy Novgorod, Russian Federation
| | - Vera Grigoryeva
- Department of Neurosurgery, Nizhniy Novgorod State Medical Academy, Nizhniy Novgorod, Russian Federation
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17
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Uryga A, Placek MM, Wachel P, Szczepański T, Czosnyka M, Kasprowicz M. Phase shift between respiratory oscillations in cerebral blood flow velocity and arterial blood pressure. Physiol Meas 2017; 38:310-324. [PMID: 28099160 DOI: 10.1088/1361-6579/38/2/310] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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18
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Rhee CJ, Kaiser JR, Rios DR, Kibler KK, Easley RB, Andropoulos DB, Czosnyka M, Smielewski P, Varsos GV, Rusin CG, Gauss CH, Williams DK, Brady KM. Elevated Diastolic Closing Margin Is Associated with Intraventricular Hemorrhage in Premature Infants. J Pediatr 2016; 174:52-6. [PMID: 27112042 PMCID: PMC4925245 DOI: 10.1016/j.jpeds.2016.03.066] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Revised: 03/11/2016] [Accepted: 03/24/2016] [Indexed: 11/19/2022]
Abstract
OBJECTIVE To determine whether the diastolic closing margin (DCM), defined as diastolic blood pressure minus critical closing pressure, is associated with the development of early severe intraventricular hemorrhage (IVH). STUDY DESIGN A reanalysis of prospectively collected data was conducted. Premature infants (gestational age 23-31 weeks) receiving mechanical ventilation (n = 185) had ∼1-hour continuous recordings of umbilical arterial blood pressure, middle cerebral artery cerebral blood flow velocity, and PaCO2 during the first week of life. Models using multivariate generalized linear regression and purposeful selection were used to determine associations with severe IVH. RESULTS Severe IVH (grades 3-4) was observed in 14.6% of the infants. Irrespective of the model used, Apgar score at 5 minutes and DCM were significantly associated with severe IVH. A clinically relevant 5-mm Hg increase in DCM was associated with a 1.83- to 1.89-fold increased odds of developing severe IVH. CONCLUSION Elevated DCM was associated with severe IVH, consistent with previous animal data showing that IVH is associated with hyperperfusion. Measurement of DCM may be more useful than blood pressure in defining cerebral perfusion in premature infants.
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Affiliation(s)
- Christopher J Rhee
- Section of Neonatology, Department of Pediatrics, Texas Children's Hospital/Baylor College of Medicine, Houston, TX.
| | - Jeffrey R Kaiser
- Section of Neonatology, Department of Pediatrics, Texas Children's Hospital/Baylor College of Medicine, Houston, TX; Department of Obstetrics and Gynecology, Texas Children's Hospital/Baylor College of Medicine, Houston, TX
| | - Danielle R Rios
- Section of Neonatology, Department of Pediatrics, Texas Children's Hospital/Baylor College of Medicine, Houston, TX
| | - Kathleen K Kibler
- Department of Anesthesiology, Texas Children's Hospital/Baylor College of Medicine, Houston, TX; Department of Critical Care Medicine, Texas Children's Hospital/Baylor College of Medicine, Houston, TX; Department of Pediatrics, Texas Children's Hospital/Baylor College of Medicine, Houston, TX
| | - R Blaine Easley
- Department of Anesthesiology, Texas Children's Hospital/Baylor College of Medicine, Houston, TX; Department of Critical Care Medicine, Texas Children's Hospital/Baylor College of Medicine, Houston, TX; Department of Pediatrics, Texas Children's Hospital/Baylor College of Medicine, Houston, TX
| | - Dean B Andropoulos
- Department of Anesthesiology, Texas Children's Hospital/Baylor College of Medicine, Houston, TX; Department of Critical Care Medicine, Texas Children's Hospital/Baylor College of Medicine, Houston, TX; Department of Pediatrics, Texas Children's Hospital/Baylor College of Medicine, Houston, TX
| | - Marek Czosnyka
- Department of Academic Neurosurgery, Addenbrooke's Hospital, University of Cambridge, Cambridge, United Kingdom
| | - Peter Smielewski
- Department of Academic Neurosurgery, Addenbrooke's Hospital, University of Cambridge, Cambridge, United Kingdom
| | - Georgios V Varsos
- Department of Academic Neurosurgery, Addenbrooke's Hospital, University of Cambridge, Cambridge, United Kingdom
| | - Craig G Rusin
- Section of Cardiology, Department of Pediatrics, Texas Children's Hospital/Baylor College of Medicine, Houston, TX
| | - C Heath Gauss
- Department of Biostatistics, University of Arkansas for Medical Sciences, Little Rock, AR
| | - D Keith Williams
- Department of Biostatistics, University of Arkansas for Medical Sciences, Little Rock, AR
| | - Ken M Brady
- Department of Anesthesiology, Texas Children's Hospital/Baylor College of Medicine, Houston, TX; Department of Critical Care Medicine, Texas Children's Hospital/Baylor College of Medicine, Houston, TX; Department of Pediatrics, Texas Children's Hospital/Baylor College of Medicine, Houston, TX
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19
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Magdalena K, Czosnyka M, Diehl RR, Haubrich C. The Interaction Between Heart Systole and Cerebral Circulation During Lower Body Negative Pressure Test. ACTA NEUROCHIRURGICA. SUPPLEMENT 2016; 122:137-41. [PMID: 27165894 DOI: 10.1007/978-3-319-22533-3_28] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
The time constant (τ[s]) estimates how fast the arterial part of the cerebrovascular bed fills with blood volume during the cardiac cycle, whereas a product of τ and heart rate (HR) (τ*HR[%]) assesses how this period of arterial filling is related to an entire heart cycle. In this study we aimed to investigate cerebral hemodynamics using τ and τ*HR during a progressive lower body negative pressure (LBNP) test.Transcranial Doppler cerebral blood flow velocity (CBFV), Finapres arterial blood pressure (ABP), and HR, along with end-tidal CO2, were simultaneously recorded in 38 healthy volunteers during an LBNP test. The τ was estimated using mathematical transformation of ABP and CBFV pulse waveforms. After a gradual shortening of τ from baseline (0.20 ± 0.06 s) to maximal LBNP before the onset of presyncope (0.15 ± 0.05 s), we observed a significant increase in τ at presyncope (0.24 ± 0.15 s; p = 0.0001). In the course of LBNP, the τ*HR did not significantly change from baseline (25.6 ± 5.7 % vs 26.6 ± 8.9 %, p = n.s.) except for presyncope, when it increased to 40.4 ± 21.1 % (p < 0.000001). Because the time needed to fill the arterial part of the cerebrovascular bed with blood is prolonged during presyncope, an increased part of the heart cycle seems to be spent on the cerebral blood supply.
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Affiliation(s)
- Kasprowicz Magdalena
- Department of Biomedical Engineering, Wroclaw University of Technology, Plac Grunwaldzki 13 (D1), Wroclaw, 50-377, Poland.
| | - Marek Czosnyka
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Rolf R Diehl
- Department of Neurology, Alfried-Krupp-Krankenhaus, Essen, Germany
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20
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Kasprowicz M, Czosnyka M, Poplawska K, Reinhard M. Cerebral Arterial Time Constant Recorded from the MCA and PICA in Normal Subjects. ACTA NEUROCHIRURGICA. SUPPLEMENT 2016; 122:211-4. [PMID: 27165908 DOI: 10.1007/978-3-319-22533-3_42] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cerebral arterial time constant (τ) estimates how quickly the cerebral arterial bed distal to the point of insonation is filled with arterial blood following a cardiac contraction. It is not known how τ behaves in different vascular territories in the brain. We therefore investigated the differences in τ of two cerebral arteries: the posterior inferior cerebellar artery (PICA) and the middle cerebral artery (MCA).Transcranial Doppler cerebral blood flow velocity (CBFV) in the PICA and left MCA along with Finapres arterial blood pressure (ABP) were simultaneously recorded in 35 young healthy volunteers. τ was estimated using mathematical transformations of pulse waveforms of ABP and the CBFV of the MCA and the PICA. Since τ is independent from the vessel radius, its comparison in different cerebral arteries was feasible. Mean ABP was 76.1 ± 9.6 mmHg. The CBFV of the MCA was higher than that of the PICA (59.7 ± 7.7 vs. 41.0 ± 4.5 cm/s; p < 0.000001). τ of the PICA was shorter than that of the MCA (0.15 ± 0.03 vs. 0.18 ± 0.03 s; p < 0.000001). The MCA-supplied vascular bed has a longer distal average length, measured from the place of insonation up to the small arterioles, than the PICA-supplied vascular bed. Therefore, a longer time is needed to fill it with arterial blood volume. This study thus confirms the physiological validity of the τ concept.
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Affiliation(s)
- Magdalena Kasprowicz
- Department of Biomedical Engineering, Wroclaw University of Technology, Wroclaw, Poland.
| | - Marek Czosnyka
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Karolina Poplawska
- Department of Biomedical Engineering, Wroclaw University of Technology, Wroclaw, Poland
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21
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Acosta S, Penny DJ, Rusin CG. An effective model of blood flow in capillary beds. Microvasc Res 2015; 100:40-7. [PMID: 25936622 DOI: 10.1016/j.mvr.2015.04.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Revised: 04/24/2015] [Accepted: 04/24/2015] [Indexed: 12/25/2022]
Abstract
In this article we derive applicable expressions for the macroscopic compliance and resistance of microvascular networks. This work yields a lumped-parameter model to describe the hemodynamics of capillary beds. Our derivation takes into account the multiscale nature of capillary networks, the influence of blood volume and pressure on the effective resistance and compliance, as well as, the nonlinear interdependence between these two properties. As a result, we obtain a simple and useful model to study hypotensive and hypertensive phenomena. We include two implementations of our theory: (i) pulmonary hypertension where the flow resistance is predicted as a function of pulmonary vascular tone. We derive from first-principles the inverse proportional relation between resistance and compliance of the pulmonary tree, which explains why the RC factor remains nearly constant across a population with increasing severity of pulmonary hypertension. (ii) The critical closing pressure in pulmonary hypotension where the flow rate dramatically decreases due to the partial collapse of the capillary bed. In both cases, the results from our proposed model compare accurately with experimental data.
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Affiliation(s)
- Sebastian Acosta
- Department of Pediatrics - Cardiology, Baylor College of Medicine, Houston TX, USA; Department of Pediatric Medicine - Cardiology, Texas Children's Hospital, Houston TX, USA.
| | - Daniel J Penny
- Department of Pediatrics - Cardiology, Baylor College of Medicine, Houston TX, USA; Department of Pediatric Medicine - Cardiology, Texas Children's Hospital, Houston TX, USA.
| | - Craig G Rusin
- Department of Pediatrics - Cardiology, Baylor College of Medicine, Houston TX, USA; Department of Pediatric Medicine - Cardiology, Texas Children's Hospital, Houston TX, USA.
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22
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Varsos GV, Kasprowicz M, Smielewski P, Czosnyka M. Model-based indices describing cerebrovascular dynamics. Neurocrit Care 2015; 20:142-57. [PMID: 24091657 DOI: 10.1007/s12028-013-9868-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Understanding the dynamic relationship between cerebral blood flow (CBF) and the circulation of cerebrospinal fluid (CSF) can facilitate management of cerebral pathologies. For this reason, various hydrodynamic models have been introduced in order to simulate the phenomena governing the interaction between CBF and CSF. The identification of hydrodynamic models requires an array of signals as input, with the most common of them being arterial blood pressure, intracranial pressure, and cerebral blood flow velocity; monitoring all of them is considered as a standard practice in neurointensive care. Based on these signals, physiological parameters like cerebrovascular resistance, compliances of cerebrovascular bed, and CSF space could then be estimated. Various secondary model-based indices describing cerebrovascular dynamics have been introduced, like the cerebral arterial time constant or critical closing pressure. This review presents model-derived indices that describe cerebrovascular phenomena, the nature of which is both physiological (carbon dioxide reactivity and arterial hypotension) and pathological (cerebral artery stenosis, intracranial hypertension, and cerebral vasospasm). In a neurointensive environment, real-time monitoring of a patient with these indices may be able to provide a detection of the onset of a cerebrovascular phenomenon, which could have otherwise been missed. This potentially "early warning" indicator may then prove to be important for the therapeutic management of the patient.
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Affiliation(s)
- Georgios V Varsos
- Neurosurgical Unit, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK,
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23
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Trofimov AO, Kalent'ev GV, Agarkova DI. Cerebrovascular resistance in patients with severe combined traumatic brain injury. ZHURNAL VOPROSY NEIROKHIRURGII IMENI N. N. BURDENKO 2015; 79:28-33. [PMID: 26528610 DOI: 10.17116/neiro201579528-33] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
UNLABELLED Cerebrovascular resistance is an important parameter of the microcirculation. The main objective of cerebrovascular resistance is to maintain the constancy of cerebral blood flow and protect downstream vessels when changing perfusion pressure. The purpose of the study was to assess cerebrovascular resistance (CVR) in patients with severe combined traumatic brain injury (CTBI) with and without intracranial hematomas (IHs). MATERIAL AND METHODS We analyzed treatment outcomes in 70 patients with severe CTBI (42 males and 28 females). The mean age was 35.5 ± 14.8 years (min 15 years; max 73 years). All patients were divided into 2 groups, depending on the presence of intracranial hemorrhage. The first group included 34 patients without IH, and the second group included 36 patients with epidural (6), subdural (26), and multiple (4) hematomas. The GCS score was 10.4 ± 2.6 in the first group and 10.6 ± 2.8 in the second group. The ISS severity injury score was 32 ± 8 in the first group and 31 ± 11 in the second group. All patients were operated on within the first 3 days, with 30 (83.3%) patients being operated on during the first day. Perfusion computed tomography (PCT) of the brain was performed within 1-14 days after TBI in the first group and within 2-8 days after surgical evacuation of hematoma in the second group. After PCT, the mean arterial pressure was measured, and the blood flow rate in the middle cerebral artery was determined using transcranial dopplerography. Cerebrovascular resistance was calculated using the formula modificated by P. Scheinberg. Comparisons between the groups were performed using the Student t-test and χ² criterion. RESULTS The mean CVR values in each group (both with and without hematomas) were statistically significantly higher than the mean normal value of this parameter. Intergroup comparison of CVR values demonstrated a statistically significant increase in the CVR level in group 2 on the side of removed hematoma compared to group 1 (p=0.037). CVR in the perifocal zone of removed hematoma remained significantly higher compared to the symmetrical zone of the contralateral hemisphere (p=0.0009). CONCLUSION Cerebrovascular resistance in patients with combined traumatic brain injury is significantly increased compared to the normal value. Cerebrovascular resistance in the perifocal zone after evacuation of hematoma in patients with multiple injury remains significantly increased compared to the symmetrical zone in the contralateral hemisphere.
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MESH Headings
- Adolescent
- Adult
- Aged
- Brain Hemorrhage, Traumatic/diagnosis
- Brain Hemorrhage, Traumatic/physiopathology
- Brain Injuries/diagnosis
- Brain Injuries/physiopathology
- Cerebrovascular Circulation/physiology
- Female
- Glasgow Coma Scale
- Hematoma, Epidural, Cranial/diagnosis
- Hematoma, Epidural, Cranial/physiopathology
- Humans
- Image Processing, Computer-Assisted
- Male
- Middle Aged
- Multiple Trauma/diagnosis
- Multiple Trauma/physiopathology
- Tomography, X-Ray Computed
- Ultrasonography, Doppler, Transcranial
- Vascular Resistance/physiology
- Young Adult
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Affiliation(s)
- A O Trofimov
- The N.A. Semashko Nizhny Novgorod Regional Hospital
| | | | - D I Agarkova
- The N.A. Semashko Nizhny Novgorod Regional Hospital
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Yaraghi A, Golparvar M, Talakoub R, Sateie H, Mehrabi A. Hypercapnic hyperventilation shortens emergence time from Propofol and Isoflurane anesthesia. J Res Pharm Pract 2014; 2:24-8. [PMID: 24991600 PMCID: PMC4076894 DOI: 10.4103/2279-042x.114085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
Objective: The aim of this study is to compare the effects of hypercapnic hyperventilation and normocapnic normoventilation on emergence time from propofol and isoflurane anesthesia. Methods: In this clinical trial, the differences in emergence time were evaluated in 80 patients undergoing elective abdominal surgery in Alzahra University hospital, Isfahan, Iran, in 2011-2012. Patients were randomly divided into four groups (groups 1-4) receiving isoflurane hypercapnic hyperventilation, isoflurane normocapnic normoventilation, propofol hypercapnic hyperventilation, and propofol normocapnic normoventilation, respectively. Hypercapnia was maintained by adding CO2 to the patient's inspired gas during hyperventilation. The emergence time and the duration of stay in recovery room in the four groups were measured and compared by one-way analysis of variance (ANOVA) and least significant difference tests. Findings: The average emergence time in groups 1, 2, 3, and 4 were (11.3 ± 3.2), (15.2 ± 3.8), (9 ± 4.2) and (11.8 ± 5.3) min, respectively. These differences were significant (P = 0.001). In patients receiving propofol hypercapnic hyperventilation, the emergence time was faster than in other groups. There was also a significant difference in duration of stay in recovery room between the groups (P = 0.004). Patients who received isoflurane hypercapnic hyperventilation had a shortest length of stay in the recovery room. Conclusion: The emergence time after intravenous anesthesia with propofol can be shortened significantly by using hyperventilation and hypercapnia, without any side effects.
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Affiliation(s)
- Ahmad Yaraghi
- Department of Anesthesia and Critical Care, Anesthesia and Critical Care Research Center, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Mohammad Golparvar
- Department of Anesthesia and Critical Care, Anesthesia and Critical Care Research Center, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Reihanak Talakoub
- Department of Anesthesia and Critical Care, Anesthesia and Critical Care Research Center, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Hossein Sateie
- Department of Anesthesia and Critical Care, Anesthesia and Critical Care Research Center, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Ali Mehrabi
- Department of Anesthesia and Critical Care, Anesthesia and Critical Care Research Center, Isfahan University of Medical Sciences, Isfahan, Iran
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Capel C, Kasprowicz M, Czosnyka M, Baledent O, Smielewski P, Pickard JD, Czosnyka Z. Cerebrovascular time constant in patients suffering from hydrocephalus. Neurol Res 2014; 36:255-61. [PMID: 24512019 DOI: 10.1179/1743132813y.0000000282] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2024]
Abstract
OBJECTIVES We studied possible link between cerebrospinal fluid (CSF) compensation and indices describing pulsatile inflow of cerebral arterial blood. METHODS A total of 50 infusion tests performed in patients with symptoms of normal pressure hydrocephalus (NPH) were examined retrospectively. Waveforms of CSF pressure, noninvasive arterial blood pressure (ABP), and transcranial Doppler (TCD) cerebral blood flow velocity (CBFV) were used to estimate relative changes in cerebral arterial compliance (Ca) and cerebrovascular resistance (CVR). Product of Ca and CVR, called cerebral arterial time constant (τ, unit: seconds), was calculated at the baseline and plateau phase of the test and compared with CSF compensatory parameters such as resistance to CSF outflow, elasticity, slope of amplitude-pressure line, and pulse amplitude of CSF pressure. RESULTS Neither of CSF compensatory parameters correlated with hemodynamic indices. However, the change in cerebral perfusion pressure (CPP) provoked change in τ (R = 0.33; P = 0.017) secondary to a change in CVR (R = 0.81; P < 0.0001). Changes in CVR and Ca had a reciprocal character (R = -0.64; P < 0.0001) with magnitude of variation in CVR (68%) prevailing over magnitude of changes in Ca (49%). DISCUSSION Hemodynamics of pulsatile inflow of cerebral arterial blood assessed by cerebral arterial time constant is not directly linked to dynamics of CSF circulation and pressure-volume compensation but is sensitive to changes in CPP during infusion test.
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Varsos GV, Richards H, Kasprowicz M, Budohoski KP, Brady KM, Reinhard M, Avolio A, Smielewski P, Pickard JD, Czosnyka M. Critical closing pressure determined with a model of cerebrovascular impedance. J Cereb Blood Flow Metab 2013; 33:235-43. [PMID: 23149558 PMCID: PMC3564193 DOI: 10.1038/jcbfm.2012.161] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Revised: 09/13/2012] [Accepted: 10/01/2012] [Indexed: 02/02/2023]
Abstract
Critical closing pressure (CCP) is the arterial blood pressure (ABP) at which brain vessels collapse and cerebral blood flow (CBF) ceases. Using the concept of impedance to CBF, CCP can be expressed with brain-monitoring parameters: cerebral perfusion pressure (CPP), ABP, blood flow velocity (FV), and heart rate. The novel multiparameter method (CCPm) was compared with traditional transcranial Doppler (TCD) calculations of CCP (CCP1). Digital recordings of ABP, intracranial pressure (ICP), and TCD-based FV from previously published studies of 29 New Zealand White rabbits were reanalyzed. Overall, CCP1 and CCPm showed correlation across wide ranges of ABP, ICP, and PaCO2 (R=0.93, P<0.001). Three physiological perturbations were studied: increase in ICP (n=29) causing both CCP1 and CCPm to increase (P<0.001 for both); reduction of ABP (n=10) resulting in decrease of CCP1 (P=0.006) and CCPm (P=0.002); and controlled increase of PaCO2 (n=8) to hypercapnic levels, which decreased CCP1 and CCPm, albeit insignificantly (P=0.123 and P=0.306 respectively), caused by a spontaneous significant increase in ABP (P=0.025). Multiparameter mathematical model of critical closing pressure explains the relationship of CCP on brain-monitoring variables, allowing the estimation of CCP during cases such as hypercapnia-induced hyperemia, where traditional calculations, like CCP1, often reach negative non-physiological values.
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Affiliation(s)
- Georgios V Varsos
- Neurosurgical Unit, Department of Clinical Neurosciences, Division of Neurosurgery, Addenbrooke's Hospital, Cambridge, UK.
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