Hypocapnia induced vasoconstriction significantly inhibits the neurovascular coupling in humans

Szabó, Katalin; Lako, Eva; Juhász, Tünde; Rosengarten, Bernhard; Csiba, László; Oláh, László

doi:10.1016/j.jns.2011.07.026

Cited by 39 publications

(57 citation statements)

References 29 publications

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“…on cerebral hemodynamics and oxygenation, i.e., an increase of the frequency and/or volume of breathing (hyperventilation) causes a decrease in PaCO2 (hypercapnia) which leads to a reduction in CBF by cerebral vasoconstriction [10]. This effect is also associated with characteristic changes of the NIRS-derived signals: [O2Hb] ↓, [HHb] ↑, [tHb] ↓, and StO2 ↓.…”

Section: Discussionmentioning

confidence: 99%

The Effect of Inner Speech on Arterial CO2 and Cerebral Hemodynamics and Oxygenation: A Functional NIRS Study

Scholkmann

Wolf²,

Wolf

2013

Oxygen Transport to Tissue XXXV

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The aim of the present study was (i) to investigate the effect of inner speech on cerebral hemodynamics and oxygenation, and (ii) to analyze if these changes could be the result of alternations of the arterial carbon dioxide pressure (PaCO2). To this end, in seven adult volunteers, we measured changes of cerebral absolute [O2Hb], [HHb], [tHb] concentrations and tissue oxygen saturation (StO2) (over the left and right anterior prefrontal cortex (PFC)), as well as changes in end-tidal CO2 (PETCO2), a reliable and accurate estimate of PaCO2. Each subject performed three different tasks (inner recitation of hexameter (IRH) or prose (IRP) verses) and a control task (mental arithmetic (MA)) on different days according to a randomized crossover design. Statistical analysis was applied to the differences between pre-baseline, two tasks, and four post-baseline periods. The two brain hemispheres and three tasks were tested separately. During the tasks, we found (i) PETCO2 decreased significantly (p < 0.05) during the IRH ( 3 mmHg) and MA ( 0.5 mmHg) task. (ii) [O2Hb] and StO2 decreased significantly during IRH ( 1.5 M; 2 %), IRP ( 1 M; 1.5 %), and MA ( 1 M; 1.5 %) tasks. During the post-baseline period, [O2Hb] and [tHb] of the left PFC decreased significantly after the IRP and MA task ( 1 M and 2 M, respectively). In conclusion, the study showed that inner speech affects PaCO2, probably due to changes in respiration. Although a decrease in PaCO2 is causing cerebral vasoconstriction and could potentially explain the decreases of [O2Hb] and StO2 during inner speech, the changes in PaCO2 were significantly different between the three tasks (no change in PaCO2 for MA) but led to very similar changes in [O2Hb] and StO2. Thus, the cerebral changes cannot solely be explained by PaCO2. Abstract: The aim of the present study was (i) to investigate the effect of inner speech on cerebral hemodynamics and oxygenation, and (ii) to analyze if these changes could be the result of alternations of the arterial carbon dioxide pressure (Pa-CO2). To this end, in seven adult volunteers, we measured changes of cerebral absolute [O2Hb], [HHb], [tHb] concentrations and tissue oxygen saturation (StO2) (over the left and right anterior prefrontal cortex (PFC)), as well as changes in end-tidal CO2 (PETCO2), a reliable and accurate estimate of PaCO2. Each subject performed three different tasks (inner recitation of hexameter (IRH) or prose (IRP) verses) and a control task (mental arithmetic (MA)) on different days according to a randomized crossover design. Statistical analysis was applied to the differences between pre-baseline, two tasks, and four postbaseline periods. The two brain hemispheres and three tasks were tested separately. During the tasks, we found (i) PETCO2 decreased significantly (p < 0.05) during the IRH (~3 mmHg) and MA (~0.5 mmHg) task. (ii) [O2Hb] and StO2 decreased significantly during IRH (~1.5 μM; ~2 %), IRP (~1 μM; ~1.5 %), and MA (~1 μM; ~1.5 %) tasks. During the post-baseline period, [O2Hb] and [tHb] of t...

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Section: Discussionmentioning

confidence: 99%

The Effect of Inner Speech on Arterial CO2 and Cerebral Hemodynamics and Oxygenation: A Functional NIRS Study

Scholkmann

Wolf²,

Wolf

2013

Oxygen Transport to Tissue XXXV

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“…E.g. a decrease in PaCO 2 (hypocapnia) leads to a reduction in CBF and CBV by vasoconstriction (Poeppel et al, 2007;Szabo et al, 2011). How PaCO 2 affects fNIRI signals was reviewed by Scholkmann et al (2013) and how to model the coupling between PaCO 2 , blood pressure (BP) and cerebral hemodynamics/oxygenation can be found in (Payne et al, 2011).…”

Section: Classification Of Signal Componentsmentioning

confidence: 99%

A review on continuous wave functional near-infrared spectroscopy and imaging instrumentation and methodology

Scholkmann¹,

Kleiser²,

Metz³

et al. 2014

NeuroImage

1,531

1,394

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This year marks the 20th anniversary of functional near-infrared spectroscopy and imaging (fNIRS/fNIRI). As the vast majority of commercial instruments developed until now are based on continuous wave technology, the aim of this publication is to review the current state of instrumentation and methodology of continuous wave fNIRI. For this purpose we provide an overview of the commercially available instruments and address instrumental aspects such as light sources, detectors and sensor arrangements. Methodological aspects, algorithms to calculate the concentrations of oxy-and deoxyhemoglobin and approaches for data analysis are also reviewed. From the single-location measurements of the early years, instrumentation has progressed to imaging initially in two dimensions (topography) and then three (tomography). The methods of analysis have also changed tremendously, from the simple modified Beer-Lambert law to sophisticated image reconstruction and data analysis methods used today. Due to these advances, fNIRI has become a modality that is widely used in neuroscience research and several manufacturers provide commercial instrumentation. It seems likely that fNIRI will become a clinical tool in the foreseeable future, which will enable diagnosis in single subjects. This year marks the 20th anniversary of functional near-infrared spectroscopy and imaging (fNIRS/fNIRI). As the vast majority of commercial instruments developed until now are based on continuous wave technology, the aim of this publication is to review the current state of instrumentation and methodology of continuous wave fNIRI. For this purpose we provide an overview of the commercially available instruments and address instrumental aspects such as light sources, detectors and sensor arrangements. Methodological aspects, algorithms to calculate the concentrations of oxy-and deoxyhemoglobin and approaches for data analysis are also reviewed. From the single-location measurements of the early years, instrumentation has progressed to imaging initially in two dimensions (topography) and then three (tomography). The methods of analysis have also changed tremendously, from the simple modified Beer-Lambert law to sophisticated image reconstruction and data analysis methods used today. Due to these advances, fNIRI has become a modality that is widely used in neuroscience research and several manufacturers provide commercial instrumentation. It seems likely that fNIRI will become a clinical tool in the foreseeable future, which will enable diagnosis in single subjects. Contents

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“…The capacity to increase cerebral perfusion during cognitive activation may be modulated by reductions in baseline CBF [i.e., the level at the onset of the cognitive/neuronal activation (435)], but it appears that cerebral functioning is preserved as long as the baseline reduction is modest and the subsequent cognitive task is associated with a similar "activation response" (delta increase in CBF). Thus, Schlader et al (389) reported that moderate hyperthermia (1.3 • C elevation in core temperature induced by passive heat stress) had no influence on working memory test performance and although MCAv at the onset of the test was reduced by 11%, the ability to increase regional CBF (delta increase in MCAv) during the cognitive activation was not impaired in those settings.…”

Section: Effects Of Cerebral Blood Flow Metabolism and Oxygenationmentioning

confidence: 99%

Cerebral Vascular Control and Metabolism in Heat Stress

Bain

Nybo

Ainslie

2015

Comprehensive Physiology

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This review provides an in-depth update on the impact of heat stress on cerebrovascular functioning. The regulation of cerebral temperature, blood flow, and metabolism are discussed. We further provide an overview of vascular permeability, the neurocognitive changes, and the key clinical implications and pathologies known to confound cerebral functioning during hyperthermia. A reduction in cerebral blood flow (CBF), derived primarily from a respiratory-induced alkalosis, underscores the cerebrovascular changes to hyperthermia. Arterial pressures may also become compromised because of reduced peripheral resistance secondary to skin vasodilatation. Therefore, when hyperthermia is combined with conditions that increase cardiovascular strain, for example, orthostasis or dehydration, the inability to preserve cerebral perfusion pressure further reduces CBF. A reduced cerebral perfusion pressure is in turn the primary mechanism for impaired tolerance to orthostatic challenges. Any reduction in CBF attenuates the brain's convective heat loss, while the hyperthermic-induced increase in metabolic rate increases the cerebral heat gain. This paradoxical uncoupling of CBF to metabolism increases brain temperature, and potentiates a condition whereby cerebral oxygenation may be compromised. With levels of experimentally viable passive hyperthermia (up to 39.5-40.0 °C core temperature), the associated reduction in CBF (∼ 30%) and increase in cerebral metabolic demand (∼ 10%) is likely compensated by increases in cerebral oxygen extraction. However, severe increases in whole-body and brain temperature may increase blood-brain barrier permeability, potentially leading to cerebral vasogenic edema. The cerebrovascular challenges associated with hyperthermia are of paramount importance for populations with compromised thermoregulatory control--for example, spinal cord injury, elderly, and those with preexisting cardiovascular diseases.

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Hypocapnia induced vasoconstriction significantly inhibits the neurovascular coupling in humans

Cited by 39 publications

References 29 publications

The Effect of Inner Speech on Arterial CO2 and Cerebral Hemodynamics and Oxygenation: A Functional NIRS Study

The Effect of Inner Speech on Arterial CO2 and Cerebral Hemodynamics and Oxygenation: A Functional NIRS Study

A review on continuous wave functional near-infrared spectroscopy and imaging instrumentation and methodology

Cerebral Vascular Control and Metabolism in Heat Stress

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