The effect of hypercapnia on static cerebral autoregulation

Update on vascular control of central chemoreceptors

At least four mechanisms have been proposed to elucidate how neurons in the retrotrapezoid (RTN) region sense changes in CO2 /H+ to regulate breathing (i.e., function as respiratory chemosensors). These mechanisms include: (1) intrinsic neuronal sensitivity to H+ mediated by TASK-2 and GPR4; (2) paracrine activation of RTN neurons by CO2 -responsive astrocytes (via a purinergic mechanism); (3) enhanced excitatory synaptic input or disinhibition; and (4) CO2 -induced vascular contraction. Although blood flow can influence tissue CO2 /H+ levels, there is limited understanding of how control of vascular tone in central CO2 chemosensitive regions might contribute to respiratory output. In this review, we focus on recent evidence that CO2 /H+ -induced purinergic-dependent vasoconstriction in the ventral parafacial region near RTN neurons supports respiratory chemoreception. This mechanism appears to be unique to the ventral parafacial region and opposite to other brain regions, including medullary chemosensor regions, where CO2 /H+ elicits vasodilatation. We speculate that this mechanism helps to maintain CO2 /H+ levels in the vicinity of RTN neurons, thereby maintaining the drive to breathe. Important next steps include determining whether disruption of CO2 /H+ vascular reactivity contributes to or can be targeted to improve breathing problems in disease states, such as Parkinson's disease.

Static autoregulation in humans

The process by which cerebral blood flow (CBF) remains approximately constant in response to short-term variations in arterial blood pressure (ABP) is known as cerebral autoregulation. This classic view, that it remains constant over a wide range of ABP, has however been challenged by a growing number of studies. To provide an updated understanding of the static cerebral pressure-flow relationship and to characterise the autoregulation curve more rigorously, we conducted a comprehensive literature research. Results were based on 143 studies in healthy individuals aged 18 to 65 years. The mean sensitivities of CBF to changes in ABP were found to be 1.47 ± 0.71%/% for decreased ABP and 0.37 ± 0.38%/% for increased ABP. The significant difference in CBF directional sensitivity suggests that cerebral autoregulation appears to be more effective in buffering increases in ABP than decreases in ABP. Regression analysis of absolute CBF and ABP identified an autoregulatory plateau of approximately 20 mmHg (ABP between 80 and 100 mmHg), which is much smaller than the widely accepted classical view. Age and sex were found to have no effect on autoregulation strength. This data-driven approach provides a quantitative method of analysing static autoregulation that can be easily updated as more experimental data become available.

Fiberoptic hemodynamic spectroscopy reveals abnormal cerebrovascular reactivity in a freely moving mouse model of Alzheimer's disease

Many Alzheimer's disease (AD) patients suffer from altered cerebral blood flow and damaged cerebral vasculature. Cerebrovascular dysfunction could play an important role in this disease. However, the mechanism underlying a vascular contribution in AD is still unclear. Cerebrovascular reactivity (CVR) is a critical mechanism that maintains cerebral blood flow and brain homeostasis. Most current methods to analyze CVR require anesthesia which is known to hamper the investigation of molecular mechanisms underlying CVR. We therefore combined spectroscopy, spectral analysis software, and an implantable device to measure cerebral blood volume fraction (CBVF) and oxygen saturation (SO2) in unanesthetized, freely-moving mice. Then, we analyzed basal CBVF and SO2, and CVR of 5-month-old C57BL/6 mice during hypercapnia as well as during basic behavior such as grooming, walking and running. Moreover, we analyzed the CVR of freely-moving AD mice and their wildtype (WT) littermates during hypercapnia and could find impaired CVR in AD mice compared to WT littermates. Our results suggest that this optomechanical approach to reproducibly getting light into the brain enabled us to successfully measure CVR in unanesthetized freely-moving mice and to find impaired CVR in a mouse model of AD.

Acute beetroot juice consumption does not alter cerebral autoregulation or cardiovagal baroreflex sensitivity during lower-body negative pressure in healthy adults

Introduction

Beetroot juice (BRJ) improves peripheral endothelial function and vascular compliance, likely due to increased nitric oxide bioavailability. It is unknown if BRJ alters cerebrovascular function and cardiovagal baroreflex control in healthy individuals.

Purpose

We tested the hypotheses that BRJ consumption improves cerebral autoregulation (CA) and cardiovagal baroreflex sensitivity (cBRS) during lower-body negative pressure (LBNP).

Methods

Thirteen healthy adults (age: 26 ± 4 years; 5 women) performed oscillatory (O-LBNP) and static LBNP (S-LBNP) before (PRE) and 3 h after consuming 500 mL of BRJ (POST). Participants inhaled 3% CO2 (21% O2, 76% N2) during a 5 min baseline and throughout LBNP to attenuate reductions in end-tidal CO2 tension (PETCO2). O-LBNP was conducted at ∼0.02 Hz for six cycles (-70 mmHg), followed by a 3-min recovery before S-LBNP (-40 mmHg) for 7 min. Beat-to-beat middle cerebral artery blood velocity (MCAv) (transcranial Doppler) and blood pressure were continuously recorded. CA was assessed using transfer function analysis to calculate coherence, gain, and phase in the very-low-frequency (VLF; 0.020-0.070 Hz) and low-frequency bands (LF; 0.07-0.20 Hz). cBRS was calculated using the sequence method. Comparisons between POST vs. PRE are reported as mean ± SD.

Results

During O-LBNP, coherence VLF was greater at POST (0.55 ± 0.06 vs. 0.46 ± 0.08; P < 0.01), but phase VLF (P = 0.17) and gain VLF (P = 0.69) were not different. Coherence LF and phase LF were not different, but gain LF was lower at POST (1.03 ± 0.20 vs. 1.12 ± 0.30 cm/s/mmHg; P = 0.05). During S-LBNP, CA was not different in the VLF or LF bands (all P > 0.10). Up-cBRS and Down-cBRS were not different during both LBNP protocols.

Conclusion

These preliminary data indicate that CA and cBRS during LBNP in healthy, young adults is largely unaffected by an acute bolus of BRJ.

The Effect of CO2 on Resting-State Functional Connectivity: Isocapnia vs. Poikilocapnia

The normal variability in breath size and frequency results in breath-to-breath variability of end-tidal PCO₂ (P_ETCO₂), the measured variable, and arterial partial pressure of carbon dioxide (PaCO₂), the independent variable affecting cerebral blood flow (CBF). This study examines the effect of variability in PaCO₂ on the pattern of resting-state functional MRI (rs-fMRI) connectivity. A region of interest (ROI)-to-ROI and Seed-to-Voxel first-level bivariate correlation, hemodynamic response function (hrf)-weighted analysis for measuring rs-fMRI connectivity was performed during two resting-state conditions: (a) normal breathing associated with breath-to-breath variation in PaCO₂ (poikilocapnia), and (b) normal breathing with breath-to-breath variability of P_ETCO₂ dampened using sequential rebreathing (isocapnia). End-tidal PCO₂ (P_ETCO₂) was used as a measurable surrogate for fluctuations of PaCO₂. During poikilocapnia, enhanced functional connections were found between the cerebellum and inferior frontal and supramarginal gyrus (SG), visual cortex and occipital fusiform gyrus; and between the primary visual network (PVN) and the hippocampal formation. During isocapnia, these associations were not seen, rather enhanced functional connections were identified in the corticostriatal pathway between the putamen and intracalacarine cortex, supracalcarine cortex (SCC), and precuneus cortex. We conclude that vascular responses to variations in P_ETCO₂, account for at least some of the observed resting state synchronization of blood oxygenation level-dependent (BOLD) signals.

The Utility of Cerebrovascular Reactivity MRI in Brain Rehabilitation: A Mechanistic Perspective

Cerebrovascular control and its integration with other physiological systems play a key role in the effective maintenance of homeostasis in brain functioning. Maintenance, restoration, and promotion of such a balance are one of the paramount goals of brain rehabilitation and intervention programs. Cerebrovascular reactivity (CVR), an index of cerebrovascular reserve, plays an important role in chemo-regulation of cerebral blood flow. Improved vascular reactivity and cerebral blood flow are important factors in brain rehabilitation to facilitate desired cognitive and functional outcomes. It is widely accepted that CVR is impaired in aging, hypertension, and cerebrovascular diseases and possibly in neurodegenerative syndromes. However, a multitude of physiological factors influence CVR, and thus a comprehensive understanding of underlying mechanisms are needed. We are currently underinformed on which rehabilitation method will improve CVR, and how this information can inform on a patient's prognosis and diagnosis. Implementation of targeted rehabilitation regimes would be the first step to elucidate whether such regimes can modulate CVR and in the process may assist in improving our understanding for the underlying vascular pathophysiology. As such, the high spatial resolution along with whole brain coverage offered by MRI has opened the door to exciting recent developments in CVR MRI. Yet, several challenges currently preclude its potential as an effective diagnostic and prognostic tool in treatment planning and guidance. Understanding these knowledge gaps will ultimately facilitate a deeper understanding for cerebrovascular physiology and its role in brain function and rehabilitation. Based on the lessons learned from our group's past and ongoing neurorehabilitation studies, we present a systematic review of physiological mechanisms that lead to impaired CVR in aging and disease, and how CVR imaging and its further development in the context of brain rehabilitation can add value to the clinical settings.

Lower body positive pressure affects systemic but not cerebral haemodynamics during incremental hyperthermia

Hyperthermia produces profound redistribution of blood and circulatory reflex function. We investigated the potential for lower body positive pressure (LBPP) to maintain or restore haemodynamics during graded hyperthermia. Eight healthy adults rested supine in a custom-made LBPP box, sealed distal to the iliac crest. Following 5 min of normothermic rest, 20 mmHg of LBPP was applied and repeated when core temperature (T_core ) had increased passively by +0.5 and +1°C. Primary dependent variables included mean middle cerebral artery blood velocity (MCAv_mean , transcranial Doppler), mean arterial blood pressure (MAP, finger photoplethysmography), heart rate (HR) and partial pressure of end-tidal carbon dioxide (P_ET CO₂ ). The absolute increase in MAP during LBPP was lower at T_core +1°C (2 ± 3 mmHg), compared with normothermia (7 ± 3 p = .01). The modest increase in MCAv_mean was unchanged by T_core (normothermia, 2 ± 3 cm/s; +0.5°C, 3 ± 3 cm/s and +1°C, 3 ± 4 cm/s, p = .74). By design, P_ET CO₂ was unchanged in all conditions from normothermic baseline (42 ± 1, p = .81). LBPP-induced changes in HR were greater at +0.5°C (-13 ± 4 b/min) and +1°C (-12 ± 6 b/min) compared with normothermia (-3 ± 3 b/min, p = .01 and p = .01, respectively). These data indicate that despite a significant attenuation in MAP to LBPP with moderate hyperthermia, MCAv_mean dynamics were unchanged among the thermal manipulations.

The effect of hypercapnia on regional cerebral blood flow regulation during progressive lower-body negative pressure

PURPOSE

Previous work indicates that dynamic cerebral blood flow (CBF) regulation is impaired during hypercapnia; however, less is known about the impact of resting hypercapnia on regional CBF regulation during hypovolemia. Furthermore, there is disparity within the literature on whether differences between anterior and posterior CBF regulation exist during physiological stressors. We hypothesized: (a) lower-body negative pressure (LBNP)-induced reductions in cerebral blood velocity (surrogate for CBF) would be more pronounced during hypercapnia, indicating impaired CBF regulation; and (b) the anterior and posterior cerebral circulations will exhibit similar responses to LBNP.

METHODS

In 12 healthy participants (6 females), heart rate (electrocardiogram), mean arterial pressure (MAP; finger photoplethosmography), partial pressure of end-tidal carbon dioxide (P_ETCO₂), middle cerebral artery blood velocity (MCAv) and posterior cerebral artery blood velocity (PCAv; transcranial Doppler ultrasound) were measured. Cerebrovascular conductance (CVC) was calculated as MCAv or PCAv indexed to MAP. Two randomized incremental LBNP protocols were conducted (- 20, - 40, - 60 and - 80 mmHg; three-minute stages), during coached normocapnia (i.e., room air), and inspired 5% hypercapnia (~ + 7 mmHg P_ETCO₂ in normoxia).

RESULTS

The main findings were: (a) static CBF regulation in the MCA and PCA was similar during normocapnic and hypercapnic LBNP trials, (b) MCA and PCA CBV and CVC responded similarly to LBNP during normocapnia, but (c) PCAv and PCA CVC were reduced to a greater extent at - 60 mmHg LBNP (P = 0.029; P < 0.001) during hypercapnia.

CONCLUSION

CBF regulation during hypovolemia was preserved in hypercapnia, and regional differences in cerebrovascular control may exist during superimposed hypovolemia and hypercapnia.

Cerebral blood flow regulation in end-stage kidney disease

Patients with chronic kidney disease (CKD) and end-stage kidney disease (ESKD) experience an increased risk of cerebrovascular disease and cognitive dysfunction. Hemodialysis (HD), a major modality of renal replacement therapy in ESKD, can cause rapid changes in blood pressure, osmolality, and acid-base balance that collectively present a unique stress to the cerebral vasculature. This review presents an update regarding cerebral blood flow (CBF) regulation in CKD and ESKD and how the maintenance of cerebral oxygenation may be compromised during HD. Patients with ESKD exhibit decreased cerebral oxygen delivery due to anemia, despite cerebral hyperperfusion at rest. Cerebral oxygenation further declines during HD due to reductions in CBF, and this may induce cerebral ischemia or "stunning." Intradialytic reductions in CBF are driven by decreases in cerebral perfusion pressure that may be partially opposed by bicarbonate shifts during dialysis. Intradialytic reductions in CBF have been related to several variables that are routinely measured in clinical practice including ultrafiltration rate and blood pressure. However, the role of compensatory cerebrovascular regulatory mechanisms during HD remains relatively unexplored. In particular, cerebral autoregulation can oppose reductions in CBF driven by reductions in systemic blood pressure, while cerebrovascular reactivity to CO₂ may attenuate intradialytic reductions in CBF through promoting cerebral vasodilation. However, whether these mechanisms are effective in ESKD and during HD remain relatively unexplored. Important areas for future work include investigating potential alterations in cerebrovascular regulation in CKD and ESKD and how key regulatory mechanisms are engaged and integrated during HD to modulate intradialytic declines in CBF.

Vascular control of the CO2/H+-dependent drive to breathe

Respiratory chemoreceptors regulate breathing in response to changes in tissue CO2/H+. Blood flow is a fundamental determinant of tissue CO2/H+, yet little is known regarding how regulation of vascular tone in chemoreceptor regions contributes to respiratory behavior. Previously, we showed in rat that CO2/H+-vasoconstriction in the retrotrapezoid nucleus (RTN) supports chemoreception by a purinergic-dependent mechanism (Hawkins et al., 2017). Here, we show in mice that CO2/H+ dilates arterioles in other chemoreceptor regions, thus demonstrating CO2/H+ vascular reactivity in the RTN is unique. We also identify P2Y2 receptors in RTN smooth muscle cells as the substrate responsible for this response. Specifically, pharmacological blockade or genetic deletion of P2Y2 from smooth muscle cells blunted the ventilatory response to CO2, and re-expression of P2Y2 receptors only in RTN smooth muscle cells fully rescued the CO2/H+ chemoreflex. These results identify P2Y2 receptors in RTN smooth muscle cells as requisite determinants of respiratory chemoreception.

The influence of age and sex on cerebrovascular reactivity and ventilatory response to hypercapnia in children and adults

NEW FINDINGS

What is the central question of this study? In this study, we investigated intracranial cerebrovascular and ventilatory reactivity to 6% CO₂ in children and adults and explored dynamic ventilatory and cerebrovascular onset responses. What is the main finding and its importance? We showed that cerebrovascular reactivity was similar in children and adults, but the intracranial blood velocity onset response was markedly attenuated in children. Sex differences were apparent, with greater increases in intracranial blood velocity in females and lower ventilatory reactivity in adult females. Our study confirms the importance of investigating dynamic onset responses when assessing the influence of development on cerebrovascular regulation.

ABSTRACT

The purpose of this study was to compare the integrated intracranial cerebrovascular reactivity (CVR) and hypercapnic ventilatory response between children and adults and to explore the dynamic response of the middle cerebral artery mean velocity (MCA_V ). Children (n = 20; 9.9 ± 0.7 years of age) and adults (n = 21; 24.4 ± 2.0 years of age) completed assessment of CVR over 240 s using a fixed fraction of inspired CO₂ (0.06). Baseline MCA_V was higher in the adult females compared with the males (P ≤ 0.05). The MCA_V was greater in female children compared with male children (P ≤ 0.05) and in female adults compared with male adults (P ≤ 0.05) with hypercapnia. Relative CVR was similar in children and adults (3.71 ± 1.06 versus 4.12 ± 1.32% mmHg^-1 ; P = 0.098), with absolute CVR being higher in adult females than males (3.27 ± 0.86 versus 2.53 ± 0.70 cm s^-1  mmHg^-1 ; P ≤ 0.001). Likewise, the hypercapnic ventilatory response did not differ between the children and adults (1.89 ± 1.00 versus 1.77 ± 1.34 l min^-1  mmHg^-1 ; P = 0.597), but was lower in adult females than males (1.815 ± 0.37 versus 2.33 ± 1.66 l min^-1  mmHg^-1 ; P ≤ 0.05). The heart rate response to hypercapnia was greater in children than in adults (P = 0.001). A monoexponential regression model was used to characterize the dynamic onset, consisting of a delay term, amplitude and time constant (τ). The results revealed that MCA_V τ was faster in adults than in children (34 ± 18 versus 74 ± 28 s; P = 0.001). Our study provides new insight into the impact of age and sex on CVR and the dynamic response of the MCA_V to hypercapnia.

Cerebral venous volume changes and pressure autoregulation in critically ill infants

OBJECTIVE

To determine whether ventilator-related fluctuations in cerebral blood volume (CBV) are associated with cerebral pressure passivity.

STUDY DESIGN

In a prospective study of newborns undergoing positive-pressure ventilation, we calculated coherence between continuous mean arterial pressure (MAP) and cerebral near-infrared spectroscopy hemoglobin difference (HbD). Significant HbD-MAP coherence indicated cerebral pressure passivity. CBV changes were measured as the spectral power of total hemoglobin (S_HbT) at the ventilator frequency. A regression model tested whether S_HbT predicts cerebral pressure passivity and/or death/brain injury, controlling for birth gestational age and other factors.

RESULTS

We studied 68 subjects with prematurity (n = 19), congenital heart disease (n = 11), and hypoxic-ischemic encephalopathy (n = 38). S_HbT, sedative use, and pCO₂ were positively associated, and circulating hemoglobin negatively associated, with cerebral pressure passivity (p < 0.001), which was positively associated with brain injury (p < 0.001).

CONCLUSION

In sick newborns, ventilator-related CBV fluctuations may predispose to cerebral pressure passivity, which may predispose to an adverse neonatal outcome.

Cerebrovascular Reactivity and Central Arterial Stiffness in Habitually Exercising Healthy Adults

Reduced cerebrovascular reactivity to a vasoactive stimulus is associated with age-related diseases such as stroke and cognitive decline. Habitual exercise is protective against cognitive decline and is associated with reduced stiffness of the large central arteries that perfuse the brain. In this context, we evaluated the age-related differences in cerebrovascular reactivity in healthy adults who habitually exercise. In addition, we sought to determine the association between central arterial stiffness and cerebrovascular reactivity. We recruited 22 young (YA: age = 27 ± 5 years, range 18–35 years) and 21 older (OA: age = 60 ± 4 years, range 56–68 years) habitual exercisers who partake in at least 150 min of structured aerobic exercise each week. Middle cerebral artery velocity (MCAv) was recorded using transcranial Doppler ultrasound. In order to assess cerebrovascular reactivity, MCAv, end-tidal carbon dioxide (ETCO₂), and mean arterial pressure (MAP) were continuously recorded at rest and during stepwise elevations of 2, 4, and 6% inhaled CO₂. Cerebrovascular conductance index (CVCi) was calculated as MCAv/MAP. Central arterial stiffness was assessed using carotid–femoral pulse wave velocity (PWV). Older adults had higher PWV (YA: 6.2 ± 1.2 m/s; OA: 7.5 ± 1.3 m/s; p < 0.05) compared with young adults. MCAv and CVCi reactivity to hypercapnia were not different between young and older adults (MCAv reactivity, YA: 2.0 ± 0.2 cm/s/mmHg; OA: 2.0 ± 0.2 cm/s/mmHg; p = 0.77, CVCi reactivity, YA: 0.018 ± 0.002 cm/s/mmHg²; OA: 0.015 ± 0.001 cm/s/mmHg²; p = 0.27); however, older adults demonstrated higher MAP reactivity to hypercapnia (YA: 0.4 ± 0.1 mmHg/mmHg; OA: 0.7 ± 0.1 mmHg/mmHg; p < 0.05). There were no associations between PWV and cerebrovascular reactivity (range: r = 0.00–0.39; p = 0.07–0.99). Our results demonstrate that cerebrovascular reactivity was not different between young and older adults who habitually exercise; however, MAP reactivity was augmented in older adults. This suggests an age-associated difference in the reliance on MAP to increase cerebral blood flow during hypercapnia.

Cerebral Oximetry and Autoregulation during Cardiopulmonary Bypass: A Review

Postoperative neurological complications (PNCs) following cardiac surgery with cardiopulmonary bypass (CPB) is a detrimental complication, contributing to increased mortality rates and health care costs. To prevent intraoperative cerebral desaturations associated with PNC, continuous brain monitoring using near-infrared spectroscopy has been advocated. However, clear evidence for a defined desaturation threshold requiring intervention during CPB is still lacking. Since cerebral oximetry readings are nonspecific, cerebral tissue oxygenation values need to be interpreted with caution and in the context of all available clinical information. Therefore, maintaining an intact autoregulatory activity during CPB rather than solely focusing on regional cerebral oxygen saturation measurements will collectively contribute to optimization of patient care during CPB.

How to build a lower-body differential pressure chamber integrated on a tilt-table: A pedagogy tool to demonstrate the cardiovagal baroreflex

The cardiovagal baroreflex is an important physiological reflex that is commonly taught in health-related university physiology courses. This reflex is responsible for the rapid maintenance of blood pressure through dynamic changes in heart rate (HR) and vascular resistance. The use of lower-body negative pressure (LBNP) and lower-body positive pressure (LBPP) can manipulate these stretch sensitive baroreceptors. High performance and relatively inexpensive homemade LBNP and LBPP chambers can be easily constructed providing a valuable tool for both research and teaching purposes. There has been previous documentation of how to build a LBNP chamber; however, the information available usually lacks appropriate construction details, and there is currently no literature on how to build a chamber that can accommodate both LBNP and LBPP. In addition, a recently developed novel LBNP/LBPP chamber positioned on a 360° tilt-table provided the unique utility of superimposing both LBNP/LBPP and body position as independent or combined stressors to alter central blood volume. The primary purposes of this manuscript are to (1) provide step-by-step instructions on how to build a tilt-table LBNP/LBPP chamber, and (2) demonstrate the effectiveness of a tilt-table LBNP/LBPP chamber to facilitate undergraduate and graduate learning in the laboratory by effectively demonstrating the cardiovagal baroreflex.

Hypercapnia: clinical relevance and mechanisms of action

PURPOSE OF REVIEW

Multiple clinical and laboratory studies have been conducted to illustrate the effects of hypercapnia in a range of injuries, and to understand the mechanisms underlying these effects. The aim of this review is to highlight and interpret information obtained from these recent reports and discuss how they may inform the clinical context.

RECENT FINDINGS

In the last decade, several important articles have addressed key elements of how carbon dioxide interacts in critical illness states. Among them the most important insights relate to how hypercapnia affects critical illness and include the effects and mechanisms of carbon dioxide in pulmonary hypertension, infection, inflammation, diaphragm dysfunction, and cerebral ischemia. In addition, we discuss molecular insights that apply to multiple aspects of critical illness.

SUMMARY

Experiments involving hypercapnia have covered a wide range of illness models with varying degrees of success. It is becoming evident that deliberate hypercapnia in the clinical setting should seldom be used, except wherever necessitated to avoid ventilator-associated lung injury. A more complete understanding of the molecular mechanisms must be established.

High-intensity interval exercise and cerebrovascular health: curiosity, cause, and consequence

Exercise is a uniquely effective and pluripotent medicine against several noncommunicable diseases of westernised lifestyles, including protection against neurodegenerative disorders. High-intensity interval exercise training (HIT) is emerging as an effective alternative to current health-related exercise guidelines. Compared with traditional moderate-intensity continuous exercise training, HIT confers equivalent if not indeed superior metabolic, cardiac, and systemic vascular adaptation. Consequently, HIT is being promoted as a more time-efficient and practical approach to optimize health thereby reducing the burden of disease associated with physical inactivity. However, no studies to date have examined the impact of HIT on the cerebrovasculature and corresponding implications for cognitive function. This review critiques the implications of HIT for cerebrovascular function, with a focus on the mechanisms and translational impact for patient health and well-being. It also introduces similarly novel interventions currently under investigation as alternative means of accelerating exercise-induced cerebrovascular adaptation. We highlight a need for studies of the mechanisms and thereby also the optimal dose-response strategies to guide exercise prescription, and for studies to explore alternative approaches to optimize exercise outcomes in brain-related health and disease prevention. From a clinical perspective, interventions that selectively target the aging brain have the potential to prevent stroke and associated neurovascular diseases.