Assessment of middle cerebral artery diameter during hypocapnia and hypercapnia in humans using ultra-high-field MRI

Verbree, Jasper; Bronzwaer, Anne-Sophie G. T.; Ghariq, Eidrees; Versluis, Mieke; Daemen, Mat J.A.P.; Buchem, Mark A. van; Dahan, Albert; Lieshout, Johannes J. van; Osch, Matthias J.P. van

doi:10.1152/japplphysiol.00651.2014

Cited by 259 publications

(274 citation statements)

References 26 publications

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“…The observation that RAP is not influenced by age either, is also noteworthy since changes in RAP have been associated with the myogenic control of small blood vessels as one of the main mechanisms responsible for an active CA (Panerai et al 2005). On the other hand our results agree with the wellknown increase in BP and HR with age and previously reported reductions in CBFV and EtCO2 in older subjects (Mancia et al 1980, Verbree et al 2014. Taken together, these results suggest that estimates of ARI, phase or RAP do not need to be corrected for age.…”

Section: Influence Of Agesupporting

confidence: 90%

The Leicester cerebral haemodynamics database: normative values and the influence of age and sex

et al. 2016

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Normative values of physiological parameters hold significance in modern day clinical decision-making. Lack of such normative values has been a major hurdle in the translation of research into clinical practice. A large database containing uniform recordings was constructed to allow more robust estimates of normative ranges and also assess the influence of age and sex.Doppler recordings were performed on healthy volunteers in the same laboratory, using similar protocols and equipment. Beat-to-beat blood pressure, heart-rate, electrocardiogram, and end-tidal CO2 were measured continuously. Bilateral insonation of the middle cerebral arteries (MCAs) was performed using TCD following a 15-minute stabilisation, and a 5-minute baseline recording.Good quality Doppler recordings for both MCAs were obtained in 129 participants (57 female) with a median age of 57 years (range 20-82). Age was found to influence baseline haemodynamic and transfer function analysis parameters. Cerebral blood flow velocity and critical closing pressure were the only sex-related differences found, which was significantly higher in females than males.Normative values for cerebral haemodynamic parameters have been defined in a large, healthy population. Such age/sex-defined normal values can be used to reduce the burden of collecting additional control data in future studies, as well as to identify disease-associated changes. Key wordsCerebral haemodynamics, cerebral autoregulation, ageing, sex differences, cerebral blood

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Section: Influence Of Agesupporting

confidence: 90%

The Leicester cerebral haemodynamics database: normative values and the influence of age and sex

et al. 2016

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“…Middle cerebral artery mean velocity and CBF have in the past been shown to being highly correlated. 38 However, recent studies have reported changes in vessel diameter in response to hypercapnia and hypoxia 3,18,19 albeit of greater magnitude, than those induced in the present study. In the present study, PetCO 2 was elevated 10 mm Hg above resting values, whereas changes in MCA diameter have been reported only with increases in 15 mm Hg or more.…”

Section: Discussioncontrasting

confidence: 70%

Cerebrovascular Reactivity is Increased with Acclimatization to 3,454 M Altitude

Flück

Siebenmann

Keiser

et al. 2015

J Cereb Blood Flow Metab

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Controversy exists regarding the effect of high-altitude exposure on cerebrovascular CO 2 reactivity (CVR). Confounding factors in previous studies include the use of different experimental approaches, ascent profiles, duration and severity of exposure and plausibly environmental factors associated with altitude exposure. One aim of the present study was to determine CVR throughout acclimatization to high altitude when controlling for these. Middle cerebral artery mean velocity (MCAv mean ) CVR was assessed during hyperventilation (hypocapnia) and CO 2 administration (hypercapnia) with background normoxia (sea level (SL)) and hypoxia (3,454 m) in nine healthy volunteers (26 ± 4 years (mean ± s.d.)) at SL, and after 30 minutes (HA0), 3 (HA3) and 22 (HA22) days of high-altitude (3,454 m) exposure. At altitude, ventilation was increased whereas MCAv mean was not altered. Hypercapnic CVR was decreased at HA0 (1.16% ± 0.16%/mm Hg, mean ± s.e.m.), whereas both hyper-and hypocapnic CVR were increased at HA3 (3.13% ± 0.18% and 2.96% ± 0.10%/mm Hg) and HA22 (3.32% ± 0.12% and 3.24% ± 0.14%/mm Hg) compared with SL (1.98% ± 0.22% and 2.38% ± 0.10%/mm Hg; Po0.01) regardless of background oxygenation. Cerebrovascular conductance (MCAv mean /mean arterial pressure) CVR was determined to account for blood pressure changes and revealed an attenuated response. Collectively our results show that hypocapnic and hypercapnic CVR are both elevated with acclimatization to high altitude.

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“…It is now clear that the diameter of the MCA (and hence possibly the PCA) is influenced by marked changes in arterial PCO 2 (>8 mmHg above or below resting) and arterial PO 2 (<50 mmHg) 84,96 (reviewed in literature 9,97 ). It is less clear that changes in blood pressure will affect the diameter of these intra-cranial arteries.…”

Section: Transcranial Dopplermentioning

confidence: 99%

Neurovascular coupling in humans: Physiology, methodological advances and clinical implications

Phillips

Chan

Zheng

et al. 2015

J Cereb Blood Flow Metab

338

364

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Neurovascular coupling reflects the close temporal and regional linkage between neural activity and cerebral blood flow. Although providing mechanistic insight, our understanding of neurovascular coupling is largely limited to nonphysiological ex vivo preparations and non-human models using sedatives/anesthetics with confounding cerebrovascular implications. Herein, with particular focus on humans, we review the present mechanistic understanding of neurovascular coupling and highlight current approaches to assess these responses and the application in health and disease. Moreover, we present new guidelines for standardizing the assessment of neurovascular coupling in humans. To improve the reliability of measurement and related interpretation, the utility of new automated software for neurovascular coupling is demonstrated, which provides the capacity for coalescing repetitive trials and time intervals into single contours and extracting numerous metrics (e.g., conductance and pulsatility, critical closing pressure, etc.) according to patterns of interest (e.g., peak/minimum response, time of response, etc.). This versatile software also permits the normalization of neurovascular coupling metrics to dynamic changes in arterial blood gases, potentially influencing the hyperemic response. It is hoped that these guidelines, combined with the newly developed and openly available software, will help to propel the understanding of neurovascular coupling in humans and also lead to improved clinical management of this critical physiological function.

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Assessment of middle cerebral artery diameter during hypocapnia and hypercapnia in humans using ultra-high-field MRI

Cited by 259 publications

References 26 publications

The Leicester cerebral haemodynamics database: normative values and the influence of age and sex

The Leicester cerebral haemodynamics database: normative values and the influence of age and sex

Cerebrovascular Reactivity is Increased with Acclimatization to 3,454 M Altitude

Neurovascular coupling in humans: Physiology, methodological advances and clinical implications

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