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Daher A, Payne S. The conducted vascular response as a mediator of hypercapnic cerebrovascular reactivity: A modelling study. Comput Biol Med 2024; 170:107985. [PMID: 38245966 DOI: 10.1016/j.compbiomed.2024.107985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 12/29/2023] [Accepted: 01/13/2024] [Indexed: 01/23/2024]
Abstract
It is well established that the cerebral blood flow (CBF) shows exquisite sensitivity to changes in the arterial blood partial pressure of CO2 ( [Formula: see text] ), which is reflected by an index termed cerebrovascular reactivity. In response to elevations in [Formula: see text] (hypercapnia), the vessels of the cerebral microvasculature dilate, thereby decreasing the vascular resistance and increasing CBF. Due to the challenges of access, scale and complexity encountered when studying the microvasculature, however, the mechanisms behind cerebrovascular reactivity are not fully understood. Experiments have previously established that the cholinergic release of the Acetylcholine (ACh) neurotransmitter in the cortex is a prerequisite for the hypercapnic response. It is also known that ACh functions as an endothelial-dependent agonist, in which the local administration of ACh elicits local hyperpolarization in the vascular wall; this hyperpolarization signal is then propagated upstream the vascular network through the endothelial layer and is coupled to a vasodilatory response in the vascular smooth muscle (VSM) layer in what is known as the conducted vascular response (CVR). Finally, experimental data indicate that the hypercapnic response is more strongly correlated with the CO2 levels in the tissue than in the arterioles. Accordingly, we hypothesize that the CVR, evoked by increases in local tissue CO2 levels and a subsequent local release of ACh, is responsible for the CBF increase observed in response to elevations in [Formula: see text] . By constructing physiologically grounded dynamic models of CBF and control in the cerebral vasculature, ones that integrate the available knowledge and experimental data, we build a new model of the series of signalling events and pathways underpinning the hypercapnic response, and use the model to provide compelling evidence that corroborates the aforementioned hypothesis. If the CVR indeed acts as a mediator of the hypercapnic response, the proposed mechanism would provide an important addition to our understanding of the repertoire of metabolic feedback mechanisms possessed by the brain and would motivate further in-vivo investigation. We also model the interaction of the hypercapnic response with dynamic cerebral autoregulation (dCA), the collection of mechanisms that the brain possesses to maintain near constant CBF despite perturbations in pressure, and show how the dCA mechanisms, which otherwise tend to be overlooked when analysing experimental results of cerebrovascular reactivity, could play a significant role in shaping the CBF response to elevations in [Formula: see text] . Such in-silico models can be used in tandem with in-vivo experiments to expand our understanding of cerebrovascular diseases, which continue to be among the leading causes of morbidity and mortality in humans.
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Affiliation(s)
- Ali Daher
- Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, United Kingdom.
| | - Stephen Payne
- Institute of Applied Mechanics, National Taiwan University, Taiwan
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Gaspar C, Rocha C, Balteiro J, Santos H. Effects of caffeine on cerebral blood flow. Nutrition 2024; 117:112217. [PMID: 37826937 DOI: 10.1016/j.nut.2023.112217] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 08/23/2023] [Accepted: 09/01/2023] [Indexed: 10/14/2023]
Abstract
OBJECTIVE The objective of the present study is to evaluate whether, after caffeine ingestion, there are variations in blood velocity of the middle cerebral arteries in clinically healthy young people as well as to evaluate whether this variation is dependent on the administered dose. METHODS We used transcranial Doppler ultrasonography to record blood velocities of the middle cerebral arteries in three groups of 15 clinically healthy young adults each: no caffeine, a45 mg, and 120 mg of caffeine groups. Transcranial Doppler ultrasonography provided simultaneous bilateral velocity of the middle cerebral arteries measurements while participants performed functional tests (hyperventilation and hypoventilation orders) and three cognitive activities (test 1, short-term memory; test 2, solving a vocabulary problem; and test 3, solving a math problem) each in 31-s tests with 1-min rests between them. Participants were assessed before and 30 min after caffeine ingestion. RESULTS There was a significant decrease in mean velocity, peak systolic velocity, end-diastolic velocity, and heart rate after high caffeine intake, except in hyperventilation, which was only observed in peak systolic velocity. With the intake of a lower dose, significant decreases were seen with hypoventilation and with test 1. In hyperventilation, there was only a significant decrease in end-diastolic velocity and heart rate; in test 2, it was found in mean velocity and peak systolic velocity; and in test 3, only in heart rate. CONCLUSION With this study, we conclude that caffeine influences the cardiovascular system acutely, interfering with the velocity of the middle cerebral arteries, causing its decrease. We also conclude that this acute effect causes vasodilation of the cerebral arteries, more accentuated with higher doses of caffeine.
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Affiliation(s)
- Catarina Gaspar
- Polytechnic Institute of Coimbra, Coimbra Health School, Rua 5 de Outubro - S. Martinho do Bispo, Apartado 7006, 3046-854 Coimbra, Portugal
| | - Clara Rocha
- Polytechnic Institute of Coimbra, Coimbra Health School, Rua 5 de Outubro - S. Martinho do Bispo, Apartado 7006, 3046-854 Coimbra, Portugal; INESC Coimbra, Department of Electrical and Computer Engineering, Polo 2, 3030-290 Coimbra, Portugal; Laboratory of Applied Health Research (LabinSaúde), Polytechnic Institute of Coimbra, Coimbra, Portugal.
| | - Jorge Balteiro
- Polytechnic Institute of Coimbra, Coimbra Health School, Rua 5 de Outubro - S. Martinho do Bispo, Apartado 7006, 3046-854 Coimbra, Portugal
| | - Helder Santos
- Polytechnic Institute of Coimbra, Coimbra Health School, Rua 5 de Outubro - S. Martinho do Bispo, Apartado 7006, 3046-854 Coimbra, Portugal
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Manferdelli G, Narang BJ, Bourdillon N, Giardini G, Debevec T, Millet GP. Impaired cerebrovascular CO 2 reactivity at high altitude in prematurely born adults. J Physiol 2023. [PMID: 38116893 DOI: 10.1113/jp285048] [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: 05/19/2023] [Accepted: 11/30/2023] [Indexed: 12/21/2023] Open
Abstract
Premature birth impairs cardiac and ventilatory responses to both hypoxia and hypercapnia, but little is known about cerebrovascular responses. Both at sea level and after 2 days at high altitude (3375 m), 16 young preterm-born (gestational age, 29 ± 1 weeks) and 15 age-matched term-born (40 ± 0 weeks) adults were exposed to two consecutive 4 min bouts of hyperoxic hypercapnic conditions (3% CO2 -97% O2 ; 6% CO2 -94% O2 ), followed by two periods of voluntary hyperventilation-induced hypocapnia. We measured middle cerebral artery blood velocity, end-tidal CO2 , pulmonary ventilation, beat-by-beat mean arterial pressure and arterialized capillary blood gases. Baseline middle cerebral artery blood velocity increased at high altitude compared with sea level in term-born (+24 ± 39%, P = 0.036), but not in preterm-born (-4 ± 27%, P = 0.278) adults. The end-tidal CO2 , pulmonary ventilation and mean arterial pressure were similar between groups at sea level and high altitude. Hypocapnic cerebrovascular reactivity was higher at high altitude compared with sea level in term-born adults (+173 ± 326%, P = 0.026) but not in preterm-born adults (-21 ± 107%, P = 0.572). Hypercapnic reactivity was altered at altitude only in preterm-born adults (+125 ± 144%, P < 0.001). Collectively, at high altitude, term-born participants showed higher hypocapnic (P = 0.012) and lower hypercapnic (P = 0.020) CO2 reactivity compared with their preterm-born peers. In conclusion, exposure to high altitude revealed different cerebrovascular responses in preterm- compared with term-born adults, despite similar ventilatory responses. These findings suggest a blunted cerebrovascular response at high altitude in preterm-born adults, which might predispose these individuals to an increased risk of high-altitude illnesses. KEY POINTS: Cerebral haemodynamics and cerebrovascular reactivity in normoxia are known to be similar between term-born and prematurely born adults. In contrast, acute exposure to high altitude unveiled different cerebrovascular responses to hypoxia, hypercapnia and hypocapnia. In particular, cerebral vasodilatation was impaired in prematurely born adults, leading to an exaggerated cerebral vasoconstriction. Cardiovascular and ventilatory responses to both hypo- and hypercapnia at sea level and at high altitude were similar between control subjects and prematurely born adults. Other mechanisms might therefore underlie the observed blunted cerebral vasodilatory responses in preterm-born adults at high altitude.
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Affiliation(s)
| | - Benjamin J Narang
- Department of Automatics, Biocybernetics and Robotics, Jožef Stefan Institute, Ljubljana, Slovenia
- Faculty of Sport, University of Ljubljana, Ljubljana, Slovenia
| | - Nicolas Bourdillon
- Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland
| | - Guido Giardini
- Mountain Medicine and Neurology Centre, Valle D'Aosta Regional Hospital, Aosta, Italy
| | - Tadej Debevec
- Department of Automatics, Biocybernetics and Robotics, Jožef Stefan Institute, Ljubljana, Slovenia
- Faculty of Sport, University of Ljubljana, Ljubljana, Slovenia
| | - Grégoire P Millet
- Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland
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Lv H, Xiong C, Wu B, Lan Z, Xu D, Duan D, Huang X, Guo J, Yu S. Effects of targeted mild hypercapnia versus normocapnia on cerebral oxygen saturation in patients undergoing laparoscopic hepatectomy under low central venous pressure: a prospective, randomized controlled study. BMC Anesthesiol 2023; 23:257. [PMID: 37525100 PMCID: PMC10388477 DOI: 10.1186/s12871-023-02220-y] [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: 03/06/2023] [Accepted: 07/26/2023] [Indexed: 08/02/2023] Open
Abstract
BACKGROUND Laparoscopic hepatectomy under low central venous pressure (LCVP) is associated with intraoperative organ hypoperfusion, including cerebral hypoperfusion. We hypothesized that a ventilation strategy designed to achieve targeted mild hypercapnia (TMH) (end-tidal carbon dioxide partial pressure [PetCO2] of 45 ± 5 mmHg) rather than targeted normocapnia (TN) (PetCO2 of 30 ± 5 mmHg) would increase regional cerebral oxygen saturation (rSO2) during laparoscopic hepatectomy under LCVP. METHODS Eighty patients undergoing laparoscopic hepatectomy under LCVP were randomly divided into the TMH group (n = 40) and the TN group (n = 40). Mechanical ventilation was adjusted to maintain the PetCO2 within the relevant range. Cerebral oxygenation was monitored continuously using the FORE-SIGHT system before anesthetic induction until the patient left the operating room. Patient and surgical characteristics, rSO2, intraoperative hemodynamic parameters (CVP, mean artery blood pressure [MAP], and heart rate), PetCO2, intraoperative blood gas analysis results, and postoperative complications were recorded. RESULTS No significant differences were observed in CVP, MAP, and heart rate between the two groups during surgery. The rSO2 was significantly lower in the TN group on both the left and right sides during the intraoperative period (P < 0.05), while the TMH group had a stable rSO2. In the TN group, the mean rSO2 decreased most during liver parenchymal transection when compared with the baseline value (P < 0.05). The mean (standard deviation) percentage change in rSO2 from baseline to parenchymal transection was - 7.5% (4.8%) on the left and - 7.1% (4.6%) on the right. The two groups had a similar incidence of postoperative complications (P > 0.05). CONCLUSION Our findings demonstrate that rSO2 is better maintained during laparoscopic hepatectomy under LCVP when patients are ventilated to a PetCO2 of 45 ± 5 mmHg (TMH) than a PetCO2 of 30 ± 5 mmHg (TN). TRIAL REGISTRATION ChiCTR2100051130(14/9/2021).
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Affiliation(s)
- Huayan Lv
- Department of Anesthesiology, Jinhua Hospital Affiliated to Zhejiang University School of Medicine, Jinhua, Zhejiang Province, People's Republic of China
| | - Chang Xiong
- Department of Anesthesiology, Jinhua Hospital Affiliated to Zhejiang University School of Medicine, Jinhua, Zhejiang Province, People's Republic of China
| | - Bo Wu
- Department of Hepatological Surgery, Jinhua Hospital Affiliated to Zhejiang University School of Medicine, Jinhua, Zhejiang Province, People's Republic of China
| | - Zhijian Lan
- Department of Anesthesiology, Jinhua Hospital Affiliated to Zhejiang University School of Medicine, Jinhua, Zhejiang Province, People's Republic of China
| | - Duojia Xu
- Department of Anesthesiology, Jinhua Hospital Affiliated to Zhejiang University School of Medicine, Jinhua, Zhejiang Province, People's Republic of China
| | - Dingnan Duan
- Department of Anesthesiology, Jinhua Hospital Affiliated to Zhejiang University School of Medicine, Jinhua, Zhejiang Province, People's Republic of China
| | - Xiaoxia Huang
- Department of Anesthesiology, Jinhua Hospital Affiliated to Zhejiang University School of Medicine, Jinhua, Zhejiang Province, People's Republic of China
| | - Jun Guo
- Department of Anesthesiology, Jinhua Hospital Affiliated to Zhejiang University School of Medicine, Jinhua, Zhejiang Province, People's Republic of China.
| | - Shian Yu
- Department of Hepatological Surgery, Jinhua Hospital Affiliated to Zhejiang University School of Medicine, Jinhua, Zhejiang Province, People's Republic of China.
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Hashitomi T, Hoshi D, Fukuie M, Tarumi T, Sugawara J, Watanabe K. Differences in the prefrontal cortex responses of healthy young men performing either water-based or land-based exercise at light to moderate intensity. Exp Brain Res 2023; 241:991-1000. [PMID: 36943454 PMCID: PMC10082107 DOI: 10.1007/s00221-023-06583-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Accepted: 02/24/2023] [Indexed: 03/23/2023]
Abstract
Cerebral blood flow increases more during water-based exercise than land-based exercise owing to the effects of end-tidal CO2 (PETCO2) and mean arterial pressure (MAP) changes due to water immersion. However, it is unclear whether oxygenated hemoglobin (oxy-Hb) concentrations in the prefrontal cortex (PFC) are increased more by water-based or land-based exercise. We hypothesized that oxy-Hb concentrations in the PFC are higher during water-based exercise than land-based exercise when the exercise intensity is matched. To test this hypothesis, 10 healthy participants (age: 24.2 ± 1.7 years; height: 1.75 ± 0.04 m; weight: 69.5 ± 5.2 kg) performed light- to moderate-intensity cycling exercise in water (water-based cycling (WC); chest-high water at 30 °C) and on land (LC). Stroke volume, cardio output, heart rate, MAP, respiratory rate, PETCO2, and oxy-Hb in the PFC were assessed during 15 min of exercise, with exercise intensity increased every 5 min. Both WC and LC significantly increased oxy-Hb concentrations in the PFC as exercise intensity was increased (intensity effect: p < 0.001). There was no significant difference in oxy-Hb concentrations during WC and LC in most prefrontal areas, although significant differences were found in areas corresponding to the left dorsolateral PFC (exercise effect: p < 0.001). Thus, WC and LC increase oxy-Hb concentrations in the PFC in a similar manner with increasing exercise intensity, but part of the PFC exhibits enhanced oxy-Hb levels during WC. The neural response of the PFC may differ during water-based and land-based exercise owing to differences in external information associated with water immersion.
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Affiliation(s)
- Tatsuya Hashitomi
- Doctoral Program in Sports Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan
| | - Daisuke Hoshi
- Doctoral Program in Sports Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan
- Human Informatics and Interaction Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan
| | - Marina Fukuie
- Human Informatics and Interaction Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan
| | - Takashi Tarumi
- Human Informatics and Interaction Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan
- Faculty of Health and Sports Sciences, University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki, 305-8577, Japan
| | - Jun Sugawara
- Human Informatics and Interaction Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan
- Faculty of Health and Sports Sciences, University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki, 305-8577, Japan
| | - Koichi Watanabe
- Faculty of Health and Sports Sciences, University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki, 305-8577, Japan.
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The Influence of Carbon Dioxide on Cerebral Autoregulation During Sevoflurane-based Anesthesia in Patients With Type 2 Diabetes. J Neurosurg Anesthesiol 2023; 35:65-73. [PMID: 34387283 DOI: 10.1097/ana.0000000000000794] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 07/06/2021] [Indexed: 02/07/2023]
Abstract
BACKGROUND Cerebral autoregulation (CA) continuously adjusts cerebrovascular resistance to maintain cerebral blood flow (CBF) constant despite changes in blood pressure. Also, CBF is proportional to changes in arterial carbon dioxide (CO 2 ) (cerebrovascular CO 2 reactivity). Hypercapnia elicits cerebral vasodilation that attenuates CA efficacy, while hypocapnia produces cerebral vasoconstriction that enhances CA efficacy. In this study, we quantified the influence of sevoflurane anesthesia on CO 2 reactivity and the CA-CO 2 relationship. METHODS We studied patients with type 2 diabetes mellitus (DM), prone to cerebrovascular disease, and compared them to control subjects. In 33 patients (19 DM, 14 control), end-tidal CO 2 , blood pressure, and CBF velocity were monitored awake and during sevoflurane-based anesthesia. CA, calculated with transfer function analysis assessing phase lead (degrees) between low-frequency oscillations in CBF velocity and mean arterial blood pressure, was quantified during hypocapnia, normocapnia, and hypercapnia. RESULTS In both control and DM patients, awake CO 2 reactivity was smaller (2.8%/mm Hg CO 2 ) than during sevoflurane anesthesia (3.9%/mm Hg; P <0.005). Hyperventilation increased CA efficacy more (3 deg./mm Hg CO 2 ) in controls than in DM patients (1.8 deg./mm Hg CO 2 ; P <0.001) in both awake and sevoflurane-anesthetized states. CONCLUSIONS The CA-CO 2 relationship is impaired in awake patients with type 2 DM. Sevoflurane-based anesthesia does not further impair this relationship. In patients with DM, hypocapnia induces cerebral vasoconstriction, but CA efficacy does not improve as observed in healthy subjects.
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Reed EL, Worley ML, Kueck PJ, Pietrafasa LD, Schlader ZJ, Johnson BD. Cerebral vascular function following the acute consumption of caffeinated artificially- and sugar sweetened soft drinks in healthy adults. Front Hum Neurosci 2022; 16:1063273. [PMID: 36618993 PMCID: PMC9815463 DOI: 10.3389/fnhum.2022.1063273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Accepted: 11/30/2022] [Indexed: 12/24/2022] Open
Abstract
Chronic consumption of sugar- and artificially-sweetened beverages (SSB and ASB) are associated with an increased risk of stroke but it is unclear how acute consumption influences cerebral vascular function. Purpose: We hypothesized that: (1) acute consumption of SSB and ASB would augment dynamic cerebral autoregulation (dCA) and attenuate cerebral vascular reactivity to hypercapnia (CVRCO2) compared to water; and (2) dCA and CVRCO2 would be attenuated with SSB compared to ASB and water. Methods: Twelve healthy adults (age: 23 ± 2 years, four females) completed three randomized trials where they drank 500 ml of water, SSB (Mountain Dew®), or ASB (Diet Mountain Dew®). We measured mean arterial pressure (MAP), middle and posterior cerebral artery blood velocities (MCAv and PCAv), and end-tidal CO2 tension (PETCO2). Cerebral vascular conductance was calculated as cerebral artery blood velocity/MAP (MCAc and PCAc). Twenty min after consumption, participants completed a 5 min baseline, and in a counterbalanced order, a CVRCO2 test (3%, 5%, and 7% CO2 in 3 min stages) and a dCA test (squat-stand tests at 0.10 Hz and 0.05 Hz for 5 min each) separated by 10 min. CVRCO2 was calculated as the slope of the linear regression lines of MCAv and PCAv vs. PETCO2. dCA was assessed in the MCA using transfer function analysis. Coherence, gain, and phase were determined in the low frequency (LF; 0.07-0.2 Hz) and very low frequency (VLF; 0.02-0.07 Hz). Results: MCAv and MCAc were lower after SSB (54.11 ± 12.28 cm/s, 0.58 ± 0.15 cm/s/mmHg) and ASB (51.07 ± 9.35 cm/s, 0.52 ± 1.0 cm/s/mmHg) vs. water (62.73 ± 12.96 cm/s, 0.67 ± 0.11 cm/s/mmHg; all P < 0.035), respectively. PCAc was also lower with the ASB compared to water (P = 0.007). MCA CVRCO2 was lower following ASB (1.55 ± 0.38 cm/s/mmHg) vs. water (2.00 ± 0.57 cm/s/mmHg; P = 0.011) but not after SSB (1.90 ± 0.67 cm/s/mmHg; P = 0.593). PCA CVRCO2 did not differ between beverages (P > 0.853). There were no differences between beverages for coherence (P ≥ 0.295), gain (P ≥ 0.058), or phase (P ≥ 0.084) for either frequency. Discussion: Acute consumption of caffeinated SSB and ASB resulted in lower intracranial artery blood velocity and conductance but had a minimal effect on cerebral vascular function as only MCA CVRCO2 was altered with the ASB compared to water.
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Affiliation(s)
- Emma L. Reed
- Human Integrative Physiology Lab, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, United States
| | - Morgan L. Worley
- Human Integrative Physiology Lab, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, United States
| | - Paul J. Kueck
- Human Integrative Physiology Lab, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, United States
| | - Leonard D. Pietrafasa
- Human Integrative Physiology Lab, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, United States
| | - Zachary J. Schlader
- H.H. Morris Human Performance Laboratories, Department of Kinesiology, Indiana University, Bloomington, IN, United States
| | - Blair D. Johnson
- Human Integrative Physiology Lab, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, United States,H.H. Morris Human Performance Laboratories, Department of Kinesiology, Indiana University, Bloomington, IN, United States,*Correspondence: Blair D. Johnson
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The impact of cerebral vasomotor reactivity on cerebrovascular diseases and cognitive impairment. J Neural Transm (Vienna) 2022; 129:1321-1330. [PMID: 36205784 PMCID: PMC9550758 DOI: 10.1007/s00702-022-02546-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Accepted: 09/19/2022] [Indexed: 11/10/2022]
Abstract
The regulation of cerebral blood flow (CBF) is a complex and tightly controlled function ensuring delivery of oxygen and nutrients and removal of metabolic wastes from brain tissue. Cerebral vasoreactivity (CVR) refers to the ability of the nervous system to regulate CBF according to metabolic demands or changes in the microenvironment. This can be assessed through a variety of nuclear medicine and imaging techniques and protocols. Several studies have investigated the association of CVR with physiological and pathological conditions, with particular reference to the relationship with cognitive impairment and cerebrovascular disorders (CVD). A better understanding of the interaction between CVR and cognitive dysfunction in chronic and particularly acute CVD could help improving treatment and rehabilitation strategies in these patients. In this paper, we reviewed current knowledge on CVR alterations in the context of acute and chronic CVD and cognitive dysfunction. Alterations in CVR and hemodynamics have been described in patients with both neurodegenerative and vascular cognitive impairment, and the severity of these alterations seems to correlate with CVR derailment. Furthermore, an increased risk of cognitive impairment progression has been associated with alterations in CVR parameters and hemodynamics. Few studies have investigated these associations in acute cerebrovascular disorders and the results are inconsistent; thus, further research on this topic is encouraged.
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Clough RH, Minhas JS, Haunton VJ, Hanby MF, Robinson TG, Panerai RB. Dynamics of the cerebral autoregulatory response to paced hyperventilation assessed using sub-component and time-varying analyses. J Appl Physiol (1985) 2022; 133:311-319. [PMID: 35736950 DOI: 10.1152/japplphysiol.00100.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cerebral blood flow (CBF) can be altered by a change in partial pressure of arterial CO2 (pCO2), being reduced during hyperventilation (HPV). Critical closing pressure (CrCP) and resistance area product (RAP) are parameters which can be studied to understand this change, but their dynamic response has not been investigated during paced HPV (PHPV). Seventy five participants had recordings at rest and during PHPV. Blood pressure (BP) (Finometer), bilateral CBF velocity (CBFV) (transcranial Doppler), end-tidal CO2 (capnography) and heart rate (HR) were recorded continuously. Subcomponent analysis (SCA) and time-varying CrCP, RAP and dynamic cerebral autoregulation (Autoregulation Index, ARI) were estimated comparing PHPV to poikilocapnia. PHPV caused a change in CBFV (p<0.01), EtCO2, (p<0.01), HR (p<0.001) and RAP (p<0.01). SCA demonstrated RAP was the main parameter explaining the changes in CBFV due to PHPV. The time-varying step responses for CBFV and RAP during PHPV demonstrated considerable non-stationarity compared to poikilocapnia (p<0.00001). Although time-varying ARI was temporarily depressed, after 60 s of PHPV it was significantly higher (6.81 ± 1.88) (p<0.0001) than in poikilocapnia (5.08 ± 1.86). The mean plateau of the RAP step response was -98.3 ± 58.8 % 60 s after the onset of PHPV but -71.7 ± 45.0 % for poikilocapnia (p=0.0026), with no corresponding changes in CrCP (p=0.6). Further work is needed to assess the role of sex and aging in our findings, and the potential for using RAP and CrCP to improve the sensitivity and specificity of CO2 reactivity studies in cerebrovascular conditions.
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Affiliation(s)
- Rebecca H Clough
- Cerebral Haemodynamics in Ageing and Stroke Medicine (CHiASM) Research Group, Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom
| | - Jatinder S Minhas
- Cerebral Haemodynamics in Ageing and Stroke Medicine (CHiASM) Research Group, Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom.,NIHR Leicester Biomedical Research Centre, British Heart Foundation Cardiovascular Research Centre, Glenfield Hospital, Leicester, United Kingdom
| | - Victoria J Haunton
- Cerebral Haemodynamics in Ageing and Stroke Medicine (CHiASM) Research Group, Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom.,NIHR Leicester Biomedical Research Centre, British Heart Foundation Cardiovascular Research Centre, Glenfield Hospital, Leicester, United Kingdom
| | - Martha Frances Hanby
- Cerebral Haemodynamics in Ageing and Stroke Medicine (CHiASM) Research Group, Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom
| | - Thompson G Robinson
- Cerebral Haemodynamics in Ageing and Stroke Medicine (CHiASM) Research Group, Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom.,NIHR Leicester Biomedical Research Centre, British Heart Foundation Cardiovascular Research Centre, Glenfield Hospital, Leicester, United Kingdom
| | - Ronney B Panerai
- Cerebral Haemodynamics in Ageing and Stroke Medicine (CHiASM) Research Group, Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom.,NIHR Leicester Biomedical Research Centre, British Heart Foundation Cardiovascular Research Centre, Glenfield Hospital, Leicester, United Kingdom
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Moriyama S, Ichinose M, Dobashi K, Matsutake R, Sakamoto M, Fujii N, Nishiyasu T. Hypercapnia elicits differential vascular and blood flow responses in the cerebral circulation and active skeletal muscles in exercising humans. Physiol Rep 2022; 10:e15274. [PMID: 35466573 PMCID: PMC9035754 DOI: 10.14814/phy2.15274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Accepted: 03/29/2022] [Indexed: 12/02/2022] Open
Abstract
The purpose of this study was to investigate the effects of a rise in arterial carbon dioxide pressure (PaCO2) on vascular and blood flow responses in the cerebral circulation and active skeletal muscles during dynamic exercise in humans. Thirteen healthy young adults (three women) participated in hypercapnia and normocapnia trials. In both trials, participants performed a two‐legged dynamic knee extension exercise at a constant workload that increased heart rate to roughly 100 beats min−1. In the hypercapnia trial, participants performed the exercise with spontaneous breathing while end‐tidal carbon dioxide pressure (PETCO2), an index of PaCO2, was held at 60 mmHg by inhaling hypercapnic gas (O2: 20.3 ± 0.1%; CO2: 6.0 ± 0.5%). In the normocapnia trial, minute ventilation during exercise was matched to the value in the hypercapnia trial by performing voluntary hyperventilation with PETCO2 clamped at baseline level (i.e., 40–45 mmHg) through inhalation of mildly hypercapnic gas (O2: 20.6 ± 0.1%; CO2: 2.7 ± 1.0%). Middle cerebral artery mean blood velocity and the cerebral vascular conductance index were higher in the hypercapnia trial than in the normocapnia trial. By contrast, vascular conductance in the exercising leg was lower in the hypercapnia trial than in the normocapnia trial. Blood flow to the exercising leg did not differ between the two trials. These results demonstrate that hypercapnia‐induced vasomotion in active skeletal muscles is opposite to that in the cerebral circulation. These differential vascular responses may cause a preferential rise in cerebral blood flow.
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Affiliation(s)
- Shodai Moriyama
- Faculty of Health and Sport Sciences University of Tsukuba Tsukuba City Ibaraki Japan
| | - Masashi Ichinose
- Human Integrative Physiology Laboratory School of Business Administration Meiji University Tokyo Japan
| | - Kohei Dobashi
- Faculty of Health and Sport Sciences University of Tsukuba Tsukuba City Ibaraki Japan
- Faculty of Education Hokkaido University of Education Hokkaido Japan
| | - Ryoko Matsutake
- Faculty of Health and Sport Sciences University of Tsukuba Tsukuba City Ibaraki Japan
| | - Mizuki Sakamoto
- Faculty of Health and Sport Sciences University of Tsukuba Tsukuba City Ibaraki Japan
| | - Naoto Fujii
- Faculty of Health and Sport Sciences University of Tsukuba Tsukuba City Ibaraki Japan
| | - Takeshi Nishiyasu
- Faculty of Health and Sport Sciences University of Tsukuba Tsukuba City Ibaraki Japan
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11
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Ruggiero L, Harrison SWD, Rice CL, McNeil CJ. Neuromuscular fatigability at high altitude: Lowlanders with acute and chronic exposure, and native highlanders. Acta Physiol (Oxf) 2022; 234:e13788. [PMID: 35007386 PMCID: PMC9286620 DOI: 10.1111/apha.13788] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 01/04/2022] [Accepted: 01/05/2022] [Indexed: 01/18/2023]
Abstract
Ascent to high altitude is accompanied by a reduction in partial pressure of inspired oxygen, which leads to interconnected adjustments within the neuromuscular system. This review describes the unique challenge that such an environment poses to neuromuscular fatigability (peripheral, central and supraspinal) for individuals who normally reside near to sea level (SL) (<1000 m; ie, lowlanders) and for native highlanders, who represent the manifestation of high altitude-related heritable adaptations across millennia. Firstly, the effect of acute exposure to high altitude-related hypoxia on neuromuscular fatigability will be examined. Under these conditions, both supraspinal and peripheral fatigability are increased compared with SL. The specific mechanisms contributing to impaired performance are dependent on the exercise paradigm and amount of muscle mass involved. Next, the effect of chronic exposure to high altitude (ie, acclimatization of ~7-28 days) will be considered. With acclimatization, supraspinal fatigability is restored to SL values, regardless of the amount of muscle mass involved, whereas peripheral fatigability remains greater than SL except when exercise involves a small amount of muscle mass (eg, knee extensors). Indeed, when whole-body exercise is involved, peripheral fatigability is not different to acute high-altitude exposure, due to competing positive (haematological and muscle metabolic) and negative (respiratory-mediated) effects of acclimatization on neuromuscular performance. In the final section, we consider evolutionary adaptations of native highlanders (primarily Himalayans of Tibet and Nepal) that may account for their superior performance at altitude and lesser degree of neuromuscular fatigability compared with acclimatized lowlanders, for both single-joint and whole-body exercise.
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Affiliation(s)
- Luca Ruggiero
- Laboratory of Physiomechanics of LocomotionDepartment of Pathophysiology and TransplantationUniversity of MilanMilanItaly
| | - Scott W. D. Harrison
- School of KinesiologyFaculty of Health SciencesThe University of Western OntarioLondonOntarioCanada
| | - Charles L. Rice
- School of KinesiologyFaculty of Health SciencesThe University of Western OntarioLondonOntarioCanada
- Department of Anatomy and Cell BiologySchulich School of Medicine and DentistryThe University of Western OntarioLondonOntarioCanada
| | - Chris J. McNeil
- Centre for Heart, Lung & Vascular HealthSchool of Health and Exercise SciencesUniversity of British ColumbiaKelownaBritish ColumbiaCanada
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12
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Darling AM, Richey RE, Akins JD, Saunders EFH, Matthew Brothers R, Greaney JL. Cerebrovascular reactivity is blunted in young adults with major depressive disorder: The influence of current depressive symptomology. J Affect Disord 2021; 295:513-521. [PMID: 34509066 PMCID: PMC8667006 DOI: 10.1016/j.jad.2021.08.061] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 08/20/2021] [Accepted: 08/24/2021] [Indexed: 11/19/2022]
Abstract
BACKGROUND In middle-aged adults with depression, cerebral vasodilatory reactivity is blunted; however, this has not been examined in treatment-naïve young adults with major depressive disorder (MDD). We tested the hypothesis that cerebrovascular reactivity would be blunted in young adults (18-30 yrs) with MDD compared to healthy non-depressed adults (HA) and would be attenuated to a greater extent in adults with symptomatic MDD (sMDD) compared to adults with MDD in remission (euthymic MDD; eMDD). METHODS Sixteen adults with MDD [21±3yrs; n = 8 sMDD (6 women); n = 8 eMDD (5 women)] and 14 HA (22±3yrs; 9 women) participated. End-tidal carbon dioxide concentration (PETCO2; capnograph), beat-to-beat mean arterial pressure (MAP; finger photoplethysmography), middle cerebral artery blood velocity (MCAv; transcranial Doppler ultrasound), and internal carotid artery (ICA) diameter and blood velocity (Doppler ultrasound) were continuously measured during baseline and rebreathing-induced hypercapnia. Cerebrovascular reactivity was calculated as the relative increase in vascular conductance during hypercapnia. RESULTS In adults with MDD, cerebrovascular reactivity in the MCA (∆39±9 HA vs. ∆31±13% MDD, p = 0.04), but not the ICA (∆36±24 HA vs. ∆34±18% MDD, p = 0.84), was blunted compared to HA. In the MCA, cerebrovascular reactivity was reduced in adults with sMDD compared to adults with eMDD (∆36±11 eMDD vs. ∆25±13% sMDD, p = 0.02). LIMITATIONS The cross-sectional nature approach limits conclusions regarding the temporal nature of this link. CONCLUSION These data indicate that MCA cerebrovascular reactivity is blunted in young adults with MDD and further modulated by current depressive symptomology, suggesting that the management of depressive symptomology may secondarily improve cerebrovascular health.
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Affiliation(s)
- Ashley M Darling
- Department of Kinesiology, The University of Texas at Arlington, 655W. Mitchell Street, Arlington, TX 76010, United States
| | - Rauchelle E Richey
- Department of Kinesiology, The University of Texas at Arlington, 655W. Mitchell Street, Arlington, TX 76010, United States; Department of Integrative Physiology, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX, United States
| | - John D Akins
- Department of Kinesiology, The University of Texas at Arlington, 655W. Mitchell Street, Arlington, TX 76010, United States
| | - Erika F H Saunders
- Department of Psychiatry and Behavioral Health, Penn State College of Medicine, Hershey, PA, United States
| | - R Matthew Brothers
- Department of Kinesiology, The University of Texas at Arlington, 655W. Mitchell Street, Arlington, TX 76010, United States
| | - Jody L Greaney
- Department of Kinesiology, The University of Texas at Arlington, 655W. Mitchell Street, Arlington, TX 76010, United States.
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13
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Park CG, Jung WS, Park HY, Kim HW, Kwak HJ, Jo YY. Comparison of the Effects of Normocapnia and Mild Hypercapnia on the Optic Nerve Sheath Diameter and Regional Cerebral Oxygen Saturation in Patients Undergoing Gynecological Laparoscopy with Total Intravenous Anesthesia. J Clin Med 2021; 10:jcm10204707. [PMID: 34682830 PMCID: PMC8540822 DOI: 10.3390/jcm10204707] [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] [Received: 09/10/2021] [Revised: 10/06/2021] [Accepted: 10/11/2021] [Indexed: 11/16/2022] Open
Abstract
Cerebral hemodynamics may be altered by hypercapnia during a lung-protective ventilation (LPV), CO2 pneumoperitoneum, and Trendelenburg position during general anesthesia. The purpose of this study was to compare the effects of normocapnia and mild hypercapnia on the optic nerve sheath diameter (ONSD), regional cerebral oxygen saturation (rSO2), and intraoperative respiratory mechanics in patients undergoing gynecological laparoscopy under total intravenous anesthesia (TIVA). Sixty patients (aged between 19 and 65 years) scheduled for laparoscopic gynecological surgery in the Trendelenburg position. Patients under propofol/remifentanil total intravenous anesthesia were randomly assigned to either the normocapnia group (target PaCO2 = 35 mmHg, n = 30) or the hypercapnia group (target PaCO2 = 50 mmHg, n = 30). The ONSD, rSO2, and respiratory and hemodynamic parameters were measured at 5 min after anesthetic induction (Tind) in the supine position, and at 10 min and 40 min after pneumoperitoneum (Tpp10 and Tpp40, respectively) in the Trendelenburg position. There was no significant intergroup difference in change over time in the ONSD (p = 0.318). The ONSD increased significantly at Tpp40 when compared to Tind in both normocapnia and hypercapnia groups (p = 0.02 and 0.002, respectively). There was a significant intergroup difference in changes over time in the rSO2 (p < 0.001). The rSO2 decreased significantly in the normocapnia group (p = 0.01), whereas it increased significantly in the hypercapnia group at Tpp40 compared with Tind (p = 0.002). Alveolar dead space was significantly higher in the normocapnia group than in the hypercapnia group at Tpp40 (p = 0.001). In conclusion, mild hypercapnia during the LPV might not aggravate the increase in the ONSD during CO2 pneumoperitoneum in the Trendelenburg position and could improve rSO2 compared to normocapnia in patients undergoing gynecological laparoscopy with TIVA.
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Affiliation(s)
| | | | | | | | - Hyun-Jeong Kwak
- Correspondence: (H.-J.K.); (Y.-Y.J.); Tel.: +82-322-460-3637 (H.-J.K.); +82-322-460-3651 (Y.-Y.J.); Fax: 82-32-469-6319 (H.-J.K. & Y.-Y.J.)
| | - Youn-Yi Jo
- Correspondence: (H.-J.K.); (Y.-Y.J.); Tel.: +82-322-460-3637 (H.-J.K.); +82-322-460-3651 (Y.-Y.J.); Fax: 82-32-469-6319 (H.-J.K. & Y.-Y.J.)
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14
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Tsakiris TS, Konstantopoulos AI, Bourdas DI. The Role of CO 2 on Respiration and Metabolism During Hypercapnic and Normocapnic Recovery From Exercise. RESEARCH QUARTERLY FOR EXERCISE AND SPORT 2021; 92:537-548. [PMID: 32657642 DOI: 10.1080/02701367.2020.1756196] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 04/11/2020] [Indexed: 06/11/2023]
Abstract
High intensity exercise can lead to depletion of CO2 from the body (hypocapnia). This disturbance becomes more noticeable during recovery or between seasons of intermittent exercise, putting the subject in a neural fatigue state. Objectives: A possible hypothesis to address this condition would be to provide high CO2 mixtures (hypercapnic) during the recovery period from exercise in order to relieve hypocapnia. Methods: Eight men (23.8 ± 1.2 yrs, VO2max = 45 ± 1.9 ml▪kg-1▪min-1) performed cycling exercise at 80%VO2max for 6-7 min. During recovery (23 min) they inhaled hypercapnic air (EXP-21%O2, 3%CO2, and 76%N2) or normal air (CON-21%O2, 0.003%CO2, and 79%N2). Respiratory parameters were collected with open spirometry and heart rate was measured. Results: Exercise caused mild hypocapnia {9.9 mmHg drop of CO2 end-expiratory partial pressure (PETCO2)} in CON condition after exercise (p < .005). PETCO2 elevated close to the rest values during the three hypercapnic phases in EXP condition (main effect of condition p < .001 between EXP and CON), but after hypercapnic breathing it returned to hypocapnia similarly with CON. The ventilatory response (VE▪PETCO2-1) and the exhaled volume of CO2 (VCO2) progressively increased during and also after ventilatory manipulations in EXP compared to CON condition (VE▪PETCO2-1: post hoc p < .001, VCO2: pVCO2: p < .05-.001), and VO2 became lower after the end of second hypercapnic manipulation (p < .05 between EXP and CON). Conclusion: It seems that hypercapnic breathing after exercise is not a good strategy to reverse exercise hypocapnia, because of great hyperventilation caused by CO2 and exercise mechanisms during the recovery period leading to increased CO2 removal from body. This intervention may also decrease O2 supply and muscles blood flow.
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15
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Sobczyk O, Fierstra J, Venkatraghavan L, Poublanc J, Duffin J, Fisher JA, Mikulis DJ. Measuring Cerebrovascular Reactivity: Sixteen Avoidable Pitfalls. Front Physiol 2021; 12:665049. [PMID: 34305634 PMCID: PMC8294324 DOI: 10.3389/fphys.2021.665049] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2021] [Accepted: 06/07/2021] [Indexed: 12/04/2022] Open
Abstract
An increase in arterial PCO2 is the most common stressor used to increase cerebral blood flow for assessing cerebral vascular reactivity (CVR). That CO2 is readily obtained, inexpensive, easy to administer, and safe to inhale belies the difficulties in extracting scientifically and clinically relevant information from the resulting flow responses. Over the past two decades, we have studied more than 2,000 individuals, most with cervical and cerebral vascular pathology using CO2 as the vasoactive agent and blood oxygen-level-dependent magnetic resonance imaging signal as the flow surrogate. The ability to deliver different forms of precise hypercapnic stimuli enabled systematic exploration of the blood flow-related signal changes. We learned the effect on CVR of particular aspects of the stimulus such as the arterial partial pressure of oxygen, the baseline PCO2, and the magnitude, rate, and pattern of its change. Similarly, we learned to interpret aspects of the flow response such as its magnitude, and the speed and direction of change. Finally, we were able to test whether the response falls into a normal range. Here, we present a review of our accumulated insight as 16 “lessons learned.” We hope many of these insights are sufficiently general to apply to a range of types of CO2-based vasoactive stimuli and perfusion metrics used for CVR.
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Affiliation(s)
- Olivia Sobczyk
- Department of Anaesthesia and Pain Management, University Health Network, University of Toronto, Toronto, ON, Canada.,Joint Department of Medical Imaging and the Functional Neuroimaging Laboratory, University Health Network, Toronto, ON, Canada
| | - Jorn Fierstra
- Department of Neurosurgery, University Hospital Zurich, Zürich, Switzerland
| | - Lakshmikumar Venkatraghavan
- Department of Anaesthesia and Pain Management, University Health Network, University of Toronto, Toronto, ON, Canada
| | - Julien Poublanc
- Joint Department of Medical Imaging and the Functional Neuroimaging Laboratory, University Health Network, Toronto, ON, Canada
| | - James Duffin
- Department of Anaesthesia and Pain Management, University Health Network, University of Toronto, Toronto, ON, Canada.,Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Joseph A Fisher
- Department of Anaesthesia and Pain Management, University Health Network, University of Toronto, Toronto, ON, Canada.,Department of Physiology, University of Toronto, Toronto, ON, Canada.,Institute of Medical Science, University of Toronto, Toronto, ON, Canada
| | - David J Mikulis
- Joint Department of Medical Imaging and the Functional Neuroimaging Laboratory, University Health Network, Toronto, ON, Canada.,Institute of Medical Science, University of Toronto, Toronto, ON, Canada
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16
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Oyanagi K, Tsubaki A. Effects of increased respiratory rate on cortical oxygenated hemoglobin during low-intensity exercise. Respir Physiol Neurobiol 2021; 291:103691. [PMID: 33992799 DOI: 10.1016/j.resp.2021.103691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2020] [Revised: 04/29/2021] [Accepted: 05/10/2021] [Indexed: 11/18/2022]
Abstract
This study aimed to examine whether the end-tidal partial pressure of CO2 (PEtCO2) affects the concentration of oxygenated hemoglobin (O2Hb) measured by near-infrared spectroscopy (NIRS). Participants were examined under the conditions of normal and increased ventilation. We measured O2Hb, mean blood pressure, skin blood flow, PEtCO2, respiratory rate, and minute volume at 30 % of the maximum oxygen uptake during exercise. ΔO2Hb and PEtCO2 during exercise were lower in the increased ventilation than in the normal ventilation condition. Pearson's product-moment correlation analysis showed a significant positive correlation between ΔO2Hb and ΔMAP, ΔSBF, and PEtCO2. Correlation coefficients were 0.249 (p < 0.001) for ΔMAP, 0.343 (p < 0.001) for ΔSBF, and 0.315 (p < 0.001) for PEtCO2. In conclusion, we identified increased ventilation during bicycle ergometer exercise as a significant factor associated with significantly low PEtCO2 and ΔO2Hb.
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Affiliation(s)
- Keiichi Oyanagi
- Department of Rehabilitation, Kobe City Medical Center General Hospital, Kobe, Japan.
| | - Atsuhiro Tsubaki
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan
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17
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Worley ML, O'Leary MC, Sackett JR, Schlader ZJ, Willer B, Leddy JJ, Johnson BD. Preliminary Evidence of Orthostatic Intolerance and Altered Cerebral Vascular Control Following Sport-Related Concussion. Front Neurol 2021; 12:620757. [PMID: 33897587 PMCID: PMC8062862 DOI: 10.3389/fneur.2021.620757] [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: 10/23/2020] [Accepted: 03/08/2021] [Indexed: 11/13/2022] Open
Abstract
Concussions have been shown to result in autonomic dysfunction and altered cerebral vascular function. We tested the hypothesis that concussed athletes (CA) would have altered cerebral vascular function during acute decreases and increases in blood pressure compared to healthy controls (HC). Ten CA (age: 20 ± 2 y, 7 females) and 10 HC (age: 21 ± 2 y, 6 females) completed 5 min of lower body negative pressure (LBNP; −40 mmHg) and 5 min of lower body positive pressure (LBPP; 20 mmHg). Protocols were randomized and separated by 10 min. Mean arterial pressure (MAP) and middle cerebral artery blood velocity (MCAv) were continuously recorded. Cerebral vascular resistance (CVR) was calculated as MAP/MCAv. Values are reported as change from baseline to the last minute achieved (LBNP) or 5 min (LBPP). There were no differences in baseline values between groups. During LBNP, there were no differences in the change for MAP (CA: −23 ± 18 vs. HC: −21 ± 17 cm/s; P = 0.80) or MCAv (CA: −13 ± 8 vs. HC: −18 ± 9 cm/s; P = 0.19). The change in CVR was different between groups (CA: −0.08 ± 0.26 vs. HC: 0.18 ± 0.24 mmHg/cm/s; P = 0.04). Total LBNP time was lower for CA (204 ± 92 s) vs. HC (297 ± 64 s; P = 0.04). During LBPP, the change in MAP was not different between groups (CA: 13 ± 6 vs. HC: 10 ± 7 mmHg; P = 0.32). The change in MCAv (CA: 7 ± 6 vs. HC: −4 ± 13 cm/s; P = 0.04) and CVR (CA: −0.06 ± 0.27 vs. HC: 0.38 ± 0.41 mmHg/cm/s; P = 0.03) were different between groups. CA exhibited impaired tolerance to LBNP and had a different cerebral vascular response to LBPP compared to HC.
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Affiliation(s)
- Morgan L Worley
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, United States
| | - Morgan C O'Leary
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, United States
| | - James R Sackett
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, United States
| | - Zachary J Schlader
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, United States.,Human Integrative Physiology Laboratory, Department of Kinesiology, School of Public Health, Indiana University, Bloomington, IN, United States
| | - Barry Willer
- Department of Psychiatry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, United States
| | - John J Leddy
- UBMD Department of Orthopaedics and Sports Medicine, University at Buffalo, Buffalo, NY, United States
| | - Blair D Johnson
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, United States.,Human Integrative Physiology Laboratory, Department of Kinesiology, School of Public Health, Indiana University, Bloomington, IN, United States
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18
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Convertino VA, Koons NJ, Suresh MR. Physiology of Human Hemorrhage and Compensation. Compr Physiol 2021; 11:1531-1574. [PMID: 33577122 DOI: 10.1002/cphy.c200016] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Hemorrhage is a leading cause of death following traumatic injuries in the United States. Much of the previous work in assessing the physiology and pathophysiology underlying blood loss has focused on descriptive measures of hemodynamic responses such as blood pressure, cardiac output, stroke volume, heart rate, and vascular resistance as indicators of changes in organ perfusion. More recent work has shifted the focus toward understanding mechanisms of compensation for reduced systemic delivery and cellular utilization of oxygen as a more comprehensive approach to understanding the complex physiologic changes that occur following and during blood loss. In this article, we begin with applying dimensional analysis for comparison of animal models, and progress to descriptions of various physiological consequences of hemorrhage. We then introduce the complementary side of compensation by detailing the complexity and integration of various compensatory mechanisms that are activated from the initiation of hemorrhage and serve to maintain adequate vital organ perfusion and hemodynamic stability in the scenario of reduced systemic delivery of oxygen until the onset of hemodynamic decompensation. New data are introduced that challenge legacy concepts related to mechanisms that underlie baroreflex functions and provide novel insights into the measurement of the integrated response of compensation to central hypovolemia known as the compensatory reserve. The impact of demographic and environmental factors on tolerance to hemorrhage is also reviewed. Finally, we describe how understanding the physiology of compensation can be translated to applications for early assessment of the clinical status and accurate triage of hypovolemic and hypotensive patients. © 2021 American Physiological Society. Compr Physiol 11:1531-1574, 2021.
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Affiliation(s)
- Victor A Convertino
- Battlefield Healthy & Trauma Center for Human Integrative Physiology, United States Army Institute of Surgical Research, JBSA San Antonio, Texas, USA
| | - Natalie J Koons
- Battlefield Healthy & Trauma Center for Human Integrative Physiology, United States Army Institute of Surgical Research, JBSA San Antonio, Texas, USA
| | - Mithun R Suresh
- Battlefield Healthy & Trauma Center for Human Integrative Physiology, United States Army Institute of Surgical Research, JBSA San Antonio, Texas, USA
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19
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Slessarev M, Mahmoud O, McIntyre CW, Ellis CG. Cerebral Blood Flow Deviations in Critically Ill Patients: Potential Insult Contributing to Ischemic and Hyperemic Injury. Front Med (Lausanne) 2021; 7:615318. [PMID: 33553208 PMCID: PMC7854569 DOI: 10.3389/fmed.2020.615318] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Accepted: 12/14/2020] [Indexed: 11/27/2022] Open
Abstract
Background: Ischemic and hyperemic injury have emerged as biologic mechanisms that contribute to cognitive impairment in critically ill patients. Spontaneous deviations in cerebral blood flow (CBF) beyond ischemic and hyperemic thresholds may represent an insult that contributes to this brain injury, especially if they accumulate over time and coincide with impaired autoregulation. Methods: We used transcranial Doppler to measure the proportion of time that CBF velocity (CBFv) deviated beyond previously reported ischemic and hyperemic thresholds in a cohort of critically ill patients with respiratory failure and/or shock within 48 h of ICU admission. We also assessed whether these CBFv deviations were more common during periods of impaired dynamic autoregulation, and whether they are explained by concurrent variations in mean arterial pressure (MAP) and end-tidal PCO2 (PetCO2). Results: We enrolled 12 consecutive patients (three females) who were monitored for a mean duration of 462.6 ± 39.8 min. Across patients, CBFv deviated by more than 20–30% from its baseline for 17–24% of the analysis time. These CBFv deviations occurred equally during periods of preserved and impaired autoregulation, while concurrent variations in MAP and PetCO2 explained only 13–21% of these CBFv deviations. Conclusion: CBFv deviations beyond ischemic and hyperemic thresholds are common in critically ill patients with respiratory failure or shock. These deviations occur irrespective of the state of dynamic autoregulation and are not explained by changes in MAP and CO2. Future studies should explore mechanisms responsible for these CBFv deviations and establish whether their cumulative burden predicts poor neurocognitive outcomes.
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Affiliation(s)
- Marat Slessarev
- Department of Medicine, Western University, London, ON, Canada.,Department of Medical Biophysics, Western University, London, ON, Canada.,Brain & Mind Institute, Western University, London, ON, Canada
| | - Ossama Mahmoud
- Department of Computer Science, Western University, London, ON, Canada
| | - Christopher W McIntyre
- Department of Medicine, Western University, London, ON, Canada.,Department of Medical Biophysics, Western University, London, ON, Canada
| | - Christopher G Ellis
- Department of Medical Biophysics, Western University, London, ON, Canada.,Robarts Research Institute, Western University, London, ON, Canada
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20
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Comparisons of the Nonlinear Relationship of Cerebral Blood Flow Response and Cerebral Vasomotor Reactivity to Carbon Dioxide under Hyperventilation between Postural Orthostatic Tachycardia Syndrome Patients and Healthy Subjects. J Clin Med 2020; 9:jcm9124088. [PMID: 33352894 PMCID: PMC7767239 DOI: 10.3390/jcm9124088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 12/16/2020] [Accepted: 12/16/2020] [Indexed: 11/29/2022] Open
Abstract
Postural orthostatic tachycardia syndrome (POTS) typically occurs in youths, and early accurate POTS diagnosis is challenging. A recent hypothesis suggests that upright cognitive impairment in POTS occurs because reduced cerebral blood flow velocity (CBFV) and cerebrovascular response to carbon dioxide (CO2) are nonlinear during transient changes in end-tidal CO2 (PETCO2). This novel study aimed to reveal the interaction between cerebral autoregulation and ventilatory control in POTS patients by using tilt table and hyperventilation to alter the CO2 tension between 10 and 30 mmHg. The cerebral blood flow velocity (CBFV), partial pressure of end-tidal carbon dioxide (PETCO2), and other cardiopulmonary signals were recorded for POTS patients and two healthy groups including those aged >45 years (Healthy-Elder) and aged <45 years (Healthy-Youth) throughout the experiment. Two nonlinear regression functions, Models I and II, were applied to evaluate their CBFV-PETCO2 relationship and cerebral vasomotor reactivity (CVMR). Among the estimated parameters, the curve-fitting Model I for CBFV and CVMR responses to CO2 for POTS patients demonstrated an observable dissimilarity in CBFVmax (p = 0.011), mid-PETCO2 (p = 0.013), and PETCO2 range (p = 0.023) compared with those of Healthy-Youth and in CBFVmax (p = 0.015) and CVMRmax compared with those of Healthy-Elder. With curve-fitting Model II for POTS patients, the fit parameters of curvilinear (p = 0.036) and PETCO2 level (p = 0.033) displayed significant difference in comparison with Healthy-Youth parameters; range of change (p = 0.042), PETCO2 level, and CBFVmax also displayed a significant difference in comparison with Healthy-Elder parameters. The results of this study contribute toward developing an early accurate diagnosis of impaired CBFV responses to CO2 for POTS patients.
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Shoemaker LN, Wilson LC, Lucas SJE, Machado L, Walker RJ, Cotter JD. Indomethacin markedly blunts cerebral perfusion and reactivity, with little cognitive consequence in healthy young and older adults. J Physiol 2020; 599:1097-1113. [DOI: 10.1113/jp280118] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Accepted: 11/05/2020] [Indexed: 12/11/2022] Open
Affiliation(s)
- L. N. Shoemaker
- School of Physical Education, Sport and Exercise Sciences University of Otago Dunedin New Zealand
| | - L. C. Wilson
- Department of Medicine Otago Medical School ‐ Dunedin Campus University of Otago Dunedin New Zealand
| | - S. J. E. Lucas
- Department of Physiology University of Otago Dunedin New Zealand
- School of Sport, Exercise and Rehabilitation Sciences College of Life and Environmental Sciences University of Birmingham Birmingham UK
- Centre for Human Brain Health University of Birmingham Birmingham UK
| | - L. Machado
- Department of Psychology University of Otago Dunedin New Zealand
| | - R. J. Walker
- Department of Medicine Otago Medical School ‐ Dunedin Campus University of Otago Dunedin New Zealand
| | - J. D. Cotter
- School of Physical Education, Sport and Exercise Sciences University of Otago Dunedin New Zealand
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Strapazzon G, Gatterer H, Falla M, Dal Cappello T, Malacrida S, Turner R, Schenk K, Paal P, Falk M, Schweizer J, Brugger H. Hypoxia and hypercapnia effects on cerebral oxygen saturation in avalanche burial: A pilot human experimental study. Resuscitation 2020; 158:175-182. [PMID: 33249253 DOI: 10.1016/j.resuscitation.2020.11.023] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 11/04/2020] [Accepted: 11/17/2020] [Indexed: 10/22/2022]
Abstract
BACKGROUND A sufficient supply of oxygen is crucial to avoid hypoxic cardiac arrest and brain damage within 30 min in completely-buried avalanche victims. Snow density influences levels of hypoxia and hypercapnia. The goal of this study was to investigate the effects of hypoxia and hypercapnia on cerebral oxygenation (ScO2) in humans breathing into an artificial air pocket. METHODS Each subject breathed into a closed system (air-tight face mask - plastic tube - snow air-pocket of 4 L) up to 30 min. Each subject performed three tests in different snow densities. ScO2 was measured by a near-infrared spectroscopy (NIRS) device. Measurements included peripheral oxygen saturation (SpO2), end-tidal carbon dioxide (ETCO2), air pocket gases and blood gases. Snow density was assessed via standard methods and micro-computed tomography. Based on predetermined criteria, tests were classified based on whether they were terminated before 30 min and the reason for termination. The categories were: completed tests (30 min), tests terminated before 30 min when SpO2 dropped to ≤75% and tests that were terminated before 30 min by requests of the subjects. General linear models were used to compare termination groups for changes in ScO2, ETCO2, SpO2 and air pocket gases, and a multivariate analysis was used to detect factor independent effects on ScO2. RESULTS ScO2 was decreased in the group in which the tests were terminated for SpO2 ≤ 75% caused by a decrease in oxygen supply in high snow densities. In the completed tests, an increase in ScO2 occurred despite decreased oxygen supply and decreased carbon dioxide removal. CONCLUSIONS Our data show that ScO2 determined by NIRS was not always impaired in humans breathing into an artificial air pocket despite decreased oxygen supply and decreased carbon dioxide removal. This may indicate that in medium to low snow densities brain oxygenation can be sufficient, which may reflect the initial stage of the triple H (hypothermia, hypoxia, and hypercapnia) syndrome. In high snow densities, ScO2 showed a significant decrease caused by a critical decrease in oxygen supply. This could lead to a higher risk of hypoxic cardiac arrest and brain damage.
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Affiliation(s)
- Giacomo Strapazzon
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy; Department of Anaesthesiology and Intensive Care Medicine, Medical University Innsbruck, Innsbruck, Austria.
| | - Hannes Gatterer
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Marika Falla
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy; Centre for Mind/Brain Sciences - CIMeC, University of Trento, Rovereto (TN), Italy
| | - Tomas Dal Cappello
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Sandro Malacrida
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Rachel Turner
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Kai Schenk
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Peter Paal
- Department of Anaesthesiology and Intensive Care Medicine, Hospitallers Brothers Hospital, Teaching Hospital of the Paracelsus Medical University, Salzburg, Austria
| | - Markus Falk
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Jürg Schweizer
- WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland
| | - Hermann Brugger
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy; Department of Anaesthesiology and Intensive Care Medicine, Medical University Innsbruck, Innsbruck, Austria
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Tomoto T, Riley J, Turner M, Zhang R, Tarumi T. Cerebral vasomotor reactivity during hypo- and hypercapnia across the adult lifespan. J Cereb Blood Flow Metab 2020; 40:600-610. [PMID: 30764704 PMCID: PMC7026853 DOI: 10.1177/0271678x19828327] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Age is the strongest risk factor for cerebrovascular disease; however, age-related changes in cerebrovascular function are still not well understood. The objective of this study was to measure cerebral vasomotor reactivity (CVMR) during hypo- and hypercapnia across the adult lifespan. One hundred fifty-three healthy participants (21-80 years) underwent measurements of cerebral blood flow velocity (CBFV) via transcranial Doppler, mean arterial pressure (MAP) via plethysmograph, and end-tidal CO2 (EtCO2) via capnography during hyperventilation (hypocapnia) and a modified rebreathing protocol (hypercapnia). Cerebrovascular conductance (CVCi) and resistance (CVRi) indices were calculated from the ratios of CBFV and MAP. CVMRs were assessed by the slopes of CBFV and CVCi in response to changes in EtCO2. The baseline CBFV and CVCi decreased and CVRi increased with age. Advanced age was associated with progressive declines in CVMR during hypocapnia indicating reduced cerebral vasoconstriction, but increases in CVMR during hypercapnia indicating increased vasodilation. A negative correlation between hypo- and hypercapnic CVMRs was observed across all subjects (CBFV%/ EtCO2: r = -0.419, CVCi%/ EtCO2: r = -0.442, P < 0.0001). Collectively, these findings suggest that aging is associated with decreases in CBFV, increases in cerebrovascular resistance, reduced vasoconstriction during hypocapnia, but increased vasodilatory responsiveness during hypercapnia.
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Affiliation(s)
- Tsubasa Tomoto
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX, USA.,Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jonathan Riley
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX, USA
| | - Marcel Turner
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX, USA
| | - Rong Zhang
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX, USA.,Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX, USA.,Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Takashi Tarumi
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX, USA.,Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX, USA.,Human Informatics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan
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Tucker WJ, Thomas BP, Puzziferri N, Samuel TJ, Zaha VG, Lingvay I, Almandoz J, Wang J, Gonzales EA, Brothers RM, Nelson MD. Impact of bariatric surgery on cerebral vascular reactivity and cognitive function: a non-randomized pilot study. Pilot Feasibility Stud 2020; 6:21. [PMID: 32082607 PMCID: PMC7017515 DOI: 10.1186/s40814-020-00569-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Accepted: 02/06/2020] [Indexed: 01/03/2023] Open
Abstract
Background Bariatric surgery is an effective long-term weight loss strategy yielding improvements in neurocognitive function; however, the mechanism(s) responsible for these improvements remains unclear. Here, we assessed the feasibility of using magnetic resonance imaging (MRI) to evaluate whether cerebral vascular reactivity (CVR) is impaired in severely obese bariatric surgery candidates compared with normal weight healthy controls and whether CVR improves following bariatric surgery. We also investigated whether changes in CVR were associated with changes in cognitive function. Methods Bariatric surgery candidates (n = 6) were compared with normal weight healthy controls of a similar age (n = 10) at baseline, and then reassessed 2 weeks and 14 weeks following sleeve gastrectomy bariatric surgery. Young reference controls (n = 7) were also studied at baseline to establish the range of normal for each outcome measure. Microvascular and macrovascular CVR to hypercapnia (5% CO2) were assessed using blood-oxygen-level-dependent (BOLD) MRI, and changes in the middle cerebral artery (MCA) cross-sectional area, respectively. Cognitive function was assessed using a validated neurocognitive software. Results Compliance with the CVR protocol was high. Both macro- and micro-cerebrovascular function were highest in the young reference controls. Cognitive function was lower in obese bariatric surgery candidates compared with normal weight controls, and improved by 17% at 2 weeks and 21% by 14 weeks following bariatric surgery. To our surprise, whole-brain CVR BOLD did not differ between obese bariatric surgery candidates and normal weight controls of similar age (0.184 ± 0.101 vs. 0.192 ± 0.034 %BOLD/mmHgCO2), and did not change after bariatric surgery. In contrast, we observed vasoconstriction of the MCA during hypercapnia in 60% of the obese patients prior to surgery, which appeared to be abolished following bariatric surgery. Improvements in cognitive function were not associated with improvements in either CVR BOLD or MCA vasodilation after bariatric surgery. Conclusions Assessing CVR responses to a hypercapnic challenge with MRI was feasible in severely obese bariatric patients. However, no changes in whole-brain BOLD CVR were observed following bariatric surgery despite improvements in cognitive function. We recommend that future large trials assess CVR responses to cognitive tasks (rather than hypercapnia) to better define the mechanisms responsible for cognitive function improvements following bariatric surgery.
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Affiliation(s)
- Wesley J Tucker
- 1Applied Physiology and Advanced Imaging Laboratory, Department of Kinesiology, University of Texas at Arlington, Science & Engineering Innovation & Research Building, 701 S. Nedderman Drive, Room 105, Arlington, TX 76019 USA.,2Department of Nutrition & Food Sciences, Texas Woman's University, Houston, TX USA
| | - Binu P Thomas
- 3Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX USA.,4Department of Bioengineering, University of Texas at Arlington, Arlington, TX USA
| | - Nancy Puzziferri
- 5Department of Surgery, Oregon Health & Science University, Portland, OR USA
| | - T Jake Samuel
- 1Applied Physiology and Advanced Imaging Laboratory, Department of Kinesiology, University of Texas at Arlington, Science & Engineering Innovation & Research Building, 701 S. Nedderman Drive, Room 105, Arlington, TX 76019 USA
| | - Vlad G Zaha
- 3Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX USA.,6Division of Cardiology, University of Texas Southwestern Medical Center, Dallas, TX USA
| | - Ildiko Lingvay
- 7Division of Endocrinology, Diabetes, and Metabolism, University of Texas Southwestern Medical Center, Dallas, TX USA
| | - Jaime Almandoz
- 7Division of Endocrinology, Diabetes, and Metabolism, University of Texas Southwestern Medical Center, Dallas, TX USA
| | - Jing Wang
- 8College of Nursing and Health Innovation, University of Texas at Arlington, Arlington, TX USA
| | - Edward A Gonzales
- 1Applied Physiology and Advanced Imaging Laboratory, Department of Kinesiology, University of Texas at Arlington, Science & Engineering Innovation & Research Building, 701 S. Nedderman Drive, Room 105, Arlington, TX 76019 USA.,8College of Nursing and Health Innovation, University of Texas at Arlington, Arlington, TX USA
| | - R Matthew Brothers
- 1Applied Physiology and Advanced Imaging Laboratory, Department of Kinesiology, University of Texas at Arlington, Science & Engineering Innovation & Research Building, 701 S. Nedderman Drive, Room 105, Arlington, TX 76019 USA
| | - Michael D Nelson
- 1Applied Physiology and Advanced Imaging Laboratory, Department of Kinesiology, University of Texas at Arlington, Science & Engineering Innovation & Research Building, 701 S. Nedderman Drive, Room 105, Arlington, TX 76019 USA.,4Department of Bioengineering, University of Texas at Arlington, Arlington, TX USA
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25
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Hypercapnia Impairs Vasoreactivity to Changes in Blood Pressure and Intraocular Pressure in Rat Retina. Optom Vis Sci 2020; 96:470-476. [PMID: 31274734 DOI: 10.1097/opx.0000000000001400] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
SIGNIFICANCE The balance between oxygen and carbon dioxide sets the resting tone (or diameter) of retinal blood vessels. Eyes that are hypercapnic use up their "vasodilatory reserve" and therefore fail to respond adequately to changes in intraocular or blood pressure. PURPOSE Retinal vessels are regulated by both myogenic and metabolic mechanisms. We considered whether alteration of metabolic status would modify the vascular response to ocular perfusion pressure (OPP) lowering in rat retina. METHODS In pentobarbital anesthetized adult Brown-Norway rats, normocapnia or hypercapnia was achieved by artificially ventilating animals with air or 5% carbon dioxide in ~30% oxygen, respectively. Ocular perfusion pressure was gradually reduced to ~20 mmHg by either lowering blood pressure (slowly drawing blood from a femoral artery/vein) or manometrically increasing intraocular pressure under normocapnic or hypercapnic conditions. In all four groups (n = 7 eyes for each), a confocal scanning laser ophthalmoscope was used to acquire image sequences centered on the optic nerve throughout pressure modification. The diameter of arterioles and venules at various OPP levels was measured and expressed as percentage relative to their own baseline. The response of arterioles and venules to OPP lowering was compared between normocapnic and hypercapnic groups. RESULTS Average arterial carbon dioxide partial pressures were 36.9 ± 2.6 mmHg in normocapnic and 64.1 ± 5.9 mmHg in hypercapnic (P < .001) animals. In the normocapnic groups, blood pressure lowering and intraocular pressure elevation resulted in significant vasodilation of both arterioles and venules (P < .0001). In the hypercapnic groups, OPP lowering-induced vasodilation was significantly attenuated compared with the corresponding normocapnic groups (P < .0001 for both, two-way analysis of variance). CONCLUSION Hypercapnia significantly modified myogenic vascular autoregulation in response to OPP reduction.
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Brothers RM, Fadel PJ, Keller DM. Racial disparities in cardiovascular disease risk: mechanisms of vascular dysfunction. Am J Physiol Heart Circ Physiol 2019; 317:H777-H789. [PMID: 31397168 DOI: 10.1152/ajpheart.00126.2019] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cardiovascular disease (CVD) accounts for a third of all deaths in the United States making it the leading cause of morbidity and mortality. Although CVD affects individuals of all races/ethnicities, the prevalence of CVD is highest in non-Hispanic black (BL) individuals relative to other populations. The mechanism(s) responsible for elevated CVD risk in the BL population remains incompletely understood. However, impaired vascular vasodilator capacity and exaggerated vascular vasoconstrictor responsiveness are likely contributing factors, both of which are present even in young, otherwise healthy BL individuals. Within this review, we highlight some historical and recent data, collected from our laboratories, of impaired vascular function, in terms of reduced vasodilator capacity and heightened vasoconstrictor responsiveness, in the peripheral and cerebral circulations in BL individuals. We provide data that such impairments may be related to elevated oxidative stress and subsequent reduction in nitric oxide bioavailability. In addition, divergent mechanisms of impaired vasodilatory capacity between BL men and women are discussed. Finally, we propose several directions where future research is needed to fill in knowledge gaps, which will allow for better understanding of the mechanisms contributing to impaired vascular function in this population. Ultimately, this information will allow for better lifestyle and therapeutic approaches to be implemented in an effort to minimize the increased CVD burden in the BL population.
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Affiliation(s)
- R Matthew Brothers
- Department of Kinesiology, University of Texas at Arlington, Arlington, Texas
| | - Paul J Fadel
- Department of Kinesiology, University of Texas at Arlington, Arlington, Texas
| | - David M Keller
- Department of Kinesiology, University of Texas at Arlington, Arlington, Texas
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Rivas E, Allie KN, Salvador PM. Progressive dry to humid hyperthermia alters exercise cerebral blood flow. J Therm Biol 2019; 84:398-406. [PMID: 31466779 DOI: 10.1016/j.jtherbio.2019.07.036] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Revised: 07/27/2019] [Accepted: 07/29/2019] [Indexed: 11/27/2022]
Abstract
INTRODUCTION Exercising in hot conditions may increase the risk for exertional heat-related illness due to reduction in cerebral blood flow (CBF); however, the acute effect of exercise-induced changes on CBF during compensable and uncompensable heat stress remain unclear. We tested the hypothesis that exercising in hot dry and humid conditions would have different CBF responses. METHODS Nine healthy active males completed a 30 min baseline rest then 60 min of low intensity self-paced exercise (12 rating of perceived exertion) in a 1) control compensable neutral dry (CN; 23.7 ± 0.7 °C; 10.7 ± 0.8%Rh) and 2) compensable hot dry (CH; 42.3 ± 0.3 °C; 10.7 ± 1.8%Rh) that progressively increased to an uncompensable hot humid (UCH; 42.3 ± 0.3 °C; 55.2 ± 7.7%Rh) environment in random order separated by at least 4 days. RESULTS We observed that during CN environments from rest through 60 min of exercise, middle cerebral velocity (MCAvmean) and conductance (MCAvmean CVC) remained unchanged. In contrast, during CH, MCAvmean, MCAvmean CVC, and cardiac output (Q) increased and systemic vascular resistance (SVR) decreased. However, under UCH, MCAvmean, MCAvmean CVC, and Q was reduced. No difference in mean arterial pressure or ventilation was observed during any condition. Only during UCH, end-tidal PO2 increased and PCO2 decreased. The redistribution of blood to the skin for thermoregulation (heart rate, skin blood flow and sweat rate) remained higher during exercise in UCH environments. CONCLUSIONS Collectively, exercise cerebral blood flow is altered by an integrative physiological manner that differs in CN, CH, and UCH environments. The control of CBF may be secondary to thermoregulatory control which may provide an explanation for the cause of exertional heat illness.
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Affiliation(s)
- Eric Rivas
- Exercise & Thermal Integrative Physiology Laboratory, Texas Tech University, Lubbock, TX, USA; Department of Kinesiology & Sport Management, Texas Tech University, Lubbock, TX, USA.
| | - Kyleigh N Allie
- Exercise & Thermal Integrative Physiology Laboratory, Texas Tech University, Lubbock, TX, USA; Department of Kinesiology & Sport Management, Texas Tech University, Lubbock, TX, USA
| | - Paolo M Salvador
- Exercise & Thermal Integrative Physiology Laboratory, Texas Tech University, Lubbock, TX, USA; Department of Kinesiology & Sport Management, Texas Tech University, Lubbock, TX, USA
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Hoiland RL, Fisher JA, Ainslie PN. Regulation of the Cerebral Circulation by Arterial Carbon Dioxide. Compr Physiol 2019; 9:1101-1154. [DOI: 10.1002/cphy.c180021] [Citation(s) in RCA: 101] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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The effect of severe and moderate hypoxia on exercise at a fixed level of perceived exertion. Eur J Appl Physiol 2019; 119:1213-1224. [PMID: 30820661 PMCID: PMC6469630 DOI: 10.1007/s00421-019-04111-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2018] [Accepted: 02/21/2019] [Indexed: 02/08/2023]
Abstract
Purpose The purpose of this study was to determine the primary cues regulating perceived effort and exercise performance using a fixed-RPE protocol in severe and moderate hypoxia. Methods Eight male participants (26 ± 6 years, 76.3 ± 8.6 kg, 178.5 ± 3.6 cm, 51.4 ± 8.0 mL kg− 1 min− 1\documentclass[12pt]{minimal}
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\begin{document}$$\dot {V}$$\end{document}V˙O2max) completed three exercise trials in environmental conditions of severe hypoxia (FIO2 0.114), moderate hypoxia (FIO2 0.152), and normoxia (FIO2 0.202). They were instructed to continually adjust their power output to maintain a perceived effort (RPE) of 16, exercising until power output declined to 80% of the peak 30-s power output achieved. Results Exercise time was reduced (severe hypoxia 428 ± 210 s; moderate hypoxia 1044 ± 384 s; normoxia 1550 ± 590 s) according to a reduction in FIO2 (P < 0.05). The rate of oxygen desaturation during the first 3 min of exercise was accelerated in severe hypoxia (− 5.3 ± 2.8% min− 1) relative to moderate hypoxia (− 2.5 ± 1.0% min− 1) and normoxia (− 0.7 ± 0.3% min− 1). Muscle tissue oxygenation did not differ between conditions (P > 0.05). Minute ventilation increased at a faster rate according to a decrease in FIO2 (severe hypoxia 27.6 ± 6.6; moderate hypoxia 21.8 ± 3.9; normoxia 17.3 ± 3.9 L min− 1). Moderate-to-strong correlations were identified between breathing frequency (r = − 0.718, P < 0.001), blood oxygen saturation (r = 0.611, P = 0.002), and exercise performance. Conclusions The primary cues for determining perceived effort relate to progressive arterial hypoxemia and increases in ventilation.
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Minhas JS, Kennedy C, Robinson TG, Panerai RB. Different strategies to initiate and maintain hyperventilation: their effect on continuous estimates of dynamic cerebral autoregulation. Physiol Meas 2019; 40:015003. [PMID: 30577035 DOI: 10.1088/1361-6579/aafab6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
OBJECTIVE Capnography is a key monitoring intervention in several neurologically vulnerable clinical states. Cerebral autoregulation (CA) describes the ability of the cerebrovascular system to maintain a near constant cerebral blood flow throughout fluctuations in systemic arterial blood pressure, with the partial pressure of arterial carbon dioxide known to directly influence CA. Previous work has demonstrated dysautoregulation lasting around 30 s prior to the anticipated augmentation of hyperventilation-associated hypocapnia. In order assess to potential benefit of hypocapnic interventions in an acute stroke setting, minimisation of dysregulation is paramount. APPROACH Hyperventilation strategies to induce and maintain hypocapnia were performed in 61 healthy participants, effects on temporal estimates of dynamic cerebral autoregulation (autoregulation index, ARI) were assessed to validate the most effective strategy for inducing and maintaining hypocapnia. MAIN RESULTS The extent of initial decrease was significantly smaller in the continuous metronome strategy compared to the delayed metronome and voluntary strategies (▵ARI 0.33 ± 1.18, 2.80 ± 3.33 and 3.69 ± 2.79 respectively, p < 0.017). SIGNIFICANCE The use of a continuous metronome to induce hypocapnia rather than the sudden inception of an auditory stimulus appears to reduce the initial decrease in autoregulatory capacity seen in previous studies. Dysautoregulation can be minimised by continuous metronome use during hyperventilation-induced hypocapnia. This advancement in understanding of the behaviour of CA during hypocapnia permits safer delivery of CA targeted interventions, particularly in neurologically vulnerable patient populations.
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Affiliation(s)
- Jatinder S Minhas
- Department of Cardiovascular Sciences, Cerebral Haemodynamics in Ageing and Stroke Medicine (CHIASM) Cardiovascular Sciences Research Group, University of Leicester, Leicester, United Kingdom. Department of Cardiovascular Sciences, University of Leicester, Leicester LE2 7LX, United Kingdom. Author to whom any correspondence should be addressed
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Crandall CG, Rickards CA, Johnson BD. Impact of environmental stressors on tolerance to hemorrhage in humans. Am J Physiol Regul Integr Comp Physiol 2018; 316:R88-R100. [PMID: 30517019 DOI: 10.1152/ajpregu.00235.2018] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hemorrhage is a leading cause of death in military and civilian settings, and ~85% of potentially survivable battlefield deaths are hemorrhage-related. Soldiers and civilians are exposed to a number of environmental and physiological conditions that have the potential to alter tolerance to a hemorrhagic insult. The objective of this review is to summarize the known impact of commonly encountered environmental and physiological conditions on tolerance to hemorrhagic insult, primarily in humans. The majority of the studies used lower body negative pressure (LBNP) to simulate a hemorrhagic insult, although some studies employed incremental blood withdrawal. This review addresses, first, the use of LBNP as a model of hemorrhage-induced central hypovolemia and, then, the effects of the following conditions on tolerance to LBNP: passive and exercise-induced heat stress with and without hypohydration/dehydration, exposure to hypothermia, and exposure to altitude/hypoxia. An understanding of the effects of these environmental and physiological conditions on responses to a hemorrhagic challenge, including tolerance, can enable development and implementation of targeted strategies and interventions to reduce the impact of such conditions on tolerance to a hemorrhagic insult and, ultimately, improve survival from blood loss injuries.
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Affiliation(s)
- Craig G Crandall
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center , Dallas, Texas
| | - Caroline A Rickards
- Department of Physiology and Anatomy, University of North Texas Health Science Center , Fort Worth, Texas
| | - Blair D Johnson
- Department of Exercise and Nutrition Sciences, University at Buffalo , Buffalo, New York
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Prokopiou PC, Pattinson KTS, Wise RG, Mitsis GD. Modeling of dynamic cerebrovascular reactivity to spontaneous and externally induced CO 2 fluctuations in the human brain using BOLD-fMRI. Neuroimage 2018; 186:533-548. [PMID: 30423427 DOI: 10.1016/j.neuroimage.2018.10.084] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 10/09/2018] [Accepted: 10/31/2018] [Indexed: 11/30/2022] Open
Abstract
In this work, we investigate the regional characteristics of the dynamic interactions between arterial CO2 and BOLD (dynamic cerebrovascular reactivity - dCVR) during normal breathing and hypercapnic, externally induced step CO2 challenges. To obtain dCVR curves at each voxel, we use a custom set of basis functions based on the Laguerre and gamma basis sets. This allows us to obtain robust dCVR estimates both in larger regions of interest (ROIs), as well as in individual voxels. We also implement classification schemes to identify brain regions with similar dCVR characteristics. Our results reveal considerable variability of dCVR across different brain regions, as well as during different experimental conditions (normal breathing and hypercapnic challenges), suggesting a differential response of cerebral vasculature to spontaneous CO2 fluctuations and larger, externally induced CO2 changes that are possibly associated with the underlying differences in mean arterial CO2 levels. The clustering results suggest that anatomically distinct brain regions are characterized by different dCVR curves that in some cases do not exhibit the standard, positive valued curves that have been previously reported. They also reveal a consistent set of dCVR cluster shapes for resting and forcing conditions, which exhibit different distribution patterns across brain voxels.
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Affiliation(s)
- Prokopis C Prokopiou
- Integrated Program in Neuroscience, McGill University, Montreal Neurological Institude, H3A 2B4, QC, Canada
| | - Kyle T S Pattinson
- Nuffield Department of Anaesthetics, University of Oxford, John Radcliffe Hospital, Oxford, OX3 9DU, UK
| | - Richard G Wise
- CUBRIC, School of Psychology, University of Cardiff, CF10 3AT, UK
| | - Georgios D Mitsis
- Department of Bioengineering, McGill Univesity, Montreal, QC, H3A 0C3, Canada; Integrated Program in Neuroscience, McGill University, Montreal Neurological Institude, H3A 2B4, QC, Canada.
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Ochi G, Kanazawa Y, Hyodo K, Suwabe K, Shimizu T, Fukuie T, Byun K, Soya H. Hypoxia-induced lowered executive function depends on arterial oxygen desaturation. J Physiol Sci 2018; 68:847-853. [PMID: 29536370 PMCID: PMC10717617 DOI: 10.1007/s12576-018-0603-y] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Accepted: 03/04/2018] [Indexed: 01/20/2023]
Abstract
Although it has been traditionally thought that decreasing SpO2 with ascent to high altitudes not only induces acute mountain sickness but also can decrease executive function, the relationship between decreased SpO2 levels and hypoxia-induced lowered executive function is still unclear. Here we aimed to clarify whether hypoxia-induced lowered executive function was associated with arterial oxygen desaturation, using 21 participants performing the color-word Stroop task under normoxic and three hypoxic conditions (FIO2 = 0.165, 0.135, 0.105; corresponding to altitudes of 2000, 3500, and 5000 m, respectively). Stroop interference significantly increased under severe hypoxic condition (FIO2 = 0.105) compared with the other conditions. Moreover, there was a negative correlation between Stroop interference and SpO2. In conclusion, acute exposure to severe hypoxic condition decreased executive function and this negative effect was associated with decreased SpO2. We initially implicated an arterial oxygen desaturation as a potential physiological factor resulting in hypoxia-induced lowered executive function.
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Affiliation(s)
- Genta Ochi
- Laboratory of Exercise Biochemistry and Neuroendocrinology, Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba 305-8574, Ibaraki, Japan
- Sports Neuroscience Division, Advanced Research Initiative for Human High Performance (ARIHHP), Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba 305-8574, Ibaraki, Japan
| | - Yusuke Kanazawa
- Laboratory of Exercise Biochemistry and Neuroendocrinology, Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba 305-8574, Ibaraki, Japan
| | - Kazuki Hyodo
- Laboratory of Exercise Biochemistry and Neuroendocrinology, Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba 305-8574, Ibaraki, Japan
- Physical Fitness Research Institute, Meiji Yasuda Life Foundation of Health and Welfare, Tokyo, Japan
| | - Kazuya Suwabe
- Laboratory of Exercise Biochemistry and Neuroendocrinology, Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba 305-8574, Ibaraki, Japan
- Sports Neuroscience Division, Advanced Research Initiative for Human High Performance (ARIHHP), Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba 305-8574, Ibaraki, Japan
| | - Takeshi Shimizu
- Sports Research and Development Core, University of Tsukuba, Tsukuba 305-8574, Ibaraki, Japan
| | - Takemune Fukuie
- Laboratory of Exercise Biochemistry and Neuroendocrinology, Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba 305-8574, Ibaraki, Japan
- Sports Neuroscience Division, Advanced Research Initiative for Human High Performance (ARIHHP), Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba 305-8574, Ibaraki, Japan
| | - Kyeongho Byun
- Laboratory of Exercise Biochemistry and Neuroendocrinology, Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba 305-8574, Ibaraki, Japan
- Sports Neuroscience Division, Advanced Research Initiative for Human High Performance (ARIHHP), Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba 305-8574, Ibaraki, Japan
| | - Hideaki Soya
- Laboratory of Exercise Biochemistry and Neuroendocrinology, Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba 305-8574, Ibaraki, Japan.
- Sports Neuroscience Division, Advanced Research Initiative for Human High Performance (ARIHHP), Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba 305-8574, Ibaraki, Japan.
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Patik JC, Tucker WJ, Curtis BM, Nelson MD, Nasirian A, Park S, Brothers RM. Fast-food meal reduces peripheral artery endothelial function but not cerebral vascular hypercapnic reactivity in healthy young men. Physiol Rep 2018; 6:e13867. [PMID: 30221831 PMCID: PMC6139709 DOI: 10.14814/phy2.13867] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 07/20/2018] [Accepted: 08/13/2018] [Indexed: 12/02/2022] Open
Abstract
Consumption of a representative fast-food meal (FFMeal) acutely impairs peripheral conduit artery vascular function; however, the effect on cerebral vascular function remains unknown. This study tested the hypothesis that a FFMeal would impair cerebral vascular function as indexed by an attenuated increase in cerebral vascular conductance (CVCI) in the middle cerebral artery (MCA) during a hypercapnic challenge. Ten healthy men (age: 24 ± 3 years, BMI: 24.3 ± 3.8 kg/m2 ) were studied under two conditions; a standardized FFMeal (990 kcals, 50% fat, 36% carbohydrate, 14% protein, and 2120 mg sodium) and a fasting control condition. Basal hemodynamics, cerebral vasomotor reactivity (CVMR), and brachial artery flow-mediated dilation (BA FMD) were completed after an overnight fast (Pre) and again 2 h and 4 h later both days. To assess CVMR, subjects rebreathed from a 5-L bag while MCA velocity (MCAVmean ) was measured using transcranial Doppler (TCD) ultrasound and converted into CVCI (MCAVmean /mean arterial pressure). Peripheral artery endothelial function was assessed via BA FMD following a standard 5-min occlusion protocol. As expected, BA FMD was reduced at 2 h (Pre: 6.6 ± 1.7% vs. 5.2 ± 1.8%, P = 0.01). However, despite significant impairment in BA FMD, neither peak CVCI%baseline nor CVMR was affected by the FFMeal (Control-Pre: 1.9 ± 1.1, 2 h: 2.1 ± 1.1, 4 h: 1.7 ± 1.1 ∆CVCI%·∆PET CO2-1 vs. FFMeal-Pre: 2.1 ± 1.1, 2 h: 2.2 ± 0.7, 4 h: 1.9 ± 0.9 ∆CVCI%·∆PET CO2-1 , time × condition P = 0.88). These results suggest that cerebral vascular reactivity to hypercapnia in healthy young men is not altered by an acute FFMeal.
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Affiliation(s)
- Jordan C. Patik
- Department of KinesiologyThe University of Texas at ArlingtonArlingtonTexas
- College of Nursing and Health InnovationThe University of Texas at ArlingtonArlingtonTexas
| | - Wesley J. Tucker
- Department of KinesiologyThe University of Texas at ArlingtonArlingtonTexas
- College of Nursing and Health InnovationThe University of Texas at ArlingtonArlingtonTexas
| | - Bryon M. Curtis
- Department of KinesiologyThe University of Texas at ArlingtonArlingtonTexas
- College of Nursing and Health InnovationThe University of Texas at ArlingtonArlingtonTexas
| | - Michael D. Nelson
- Department of KinesiologyThe University of Texas at ArlingtonArlingtonTexas
- College of Nursing and Health InnovationThe University of Texas at ArlingtonArlingtonTexas
| | - Aida Nasirian
- Department of KinesiologyThe University of Texas at ArlingtonArlingtonTexas
- College of Nursing and Health InnovationThe University of Texas at ArlingtonArlingtonTexas
| | - Suwon Park
- College of Nursing and Health InnovationThe University of Texas at ArlingtonArlingtonTexas
| | - Robert M. Brothers
- Department of KinesiologyThe University of Texas at ArlingtonArlingtonTexas
- College of Nursing and Health InnovationThe University of Texas at ArlingtonArlingtonTexas
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Minhas JS, Panerai RB, Robinson TG. Modelling the cerebral haemodynamic response in the physiological range of PaCO2. Physiol Meas 2018; 39:065001. [DOI: 10.1088/1361-6579/aac76b] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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Different ventilation techniques and hemodynamic optimization to maintain regional cerebral oxygen saturation (rScO 2) during laparoscopic bariatric surgery: a prospective randomized interventional study. J Anesth 2018; 32:394-402. [PMID: 29626267 DOI: 10.1007/s00540-018-2493-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2017] [Accepted: 03/26/2018] [Indexed: 10/17/2022]
Abstract
PURPOSE The purpose of this study was to assess the changes in regional cerebral oxygen saturation (rScO2) in response to different ventilation strategies: inspired oxygen concentration (FiO2), end-tidal carbon dioxide (EtCO2), and positive end expiratory pressure (PEEP) in addition to optimizing mean arterial pressure (MAP) in obese patients subjected to laparoscopic bariatric surgery in the reverse trendelenburg position. METHODS 50 obese patients were randomly assigned into one of two groups. Each group is 25 patients. Control patients subjected to a ventilation strategy aimed to maintain FiO2 0.4 and EtCO2 30 mmHg without PEEP. Study patients were assigned to specific protocol; T0, baseline rScO2; T1, 5 min following induction; T2, PP/RTP (10 min after pneumoperitoneum and reverse trendelenburg position); T3, PEEP 10 cmH2O; T4, FiO2 1.0; T5, EtCO2 40 mmHg and T6, MAP/BL; MAP back to baseline in both groups. MAIN RESULTS 10 min after PP/RTP, there was a significant decrease in rScO2 in both groups. At T4, with FiO2 1.0, there was significant improvement in rScO2 when compared to T2. At T5, with EtCO2 40 mmHg, rScO2 significantly enhanced when compared to EtCO2 30 mmHg. At T4 and T5, we observed highly significance difference between both groups. At the end of the procedure and when MAP increased back to baseline (T6) in both groups, rScO2 statistically increased in both groups when compared to T2. CONCLUSION In obese patients, subjected to laparoscopic bariatric surgery in reverse trendelenburg position, adjustment of ventilation strategies and hemodynamic optimization succeeded to improve rScO2.
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Christou GA, Christou KA, Kiortsis DN. Pathophysiology of Noncardiac Syncope in Athletes. Sports Med 2018; 48:1561-1573. [PMID: 29605837 DOI: 10.1007/s40279-018-0911-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The most frequent cause of syncope in young athletes is noncardiac etiology. The mechanism of noncardiac syncope (NCS) in young athletes is neurally-mediated (reflex). NCS in athletes usually occurs either as orthostasis-induced, due to a gravity-mediated reduced venous return to the heart, or in the context of exercise. Exercise-related NCS typically occurs after the cessation of an exercise bout, while syncope occurring during exercise is highly indicative of the existence of a cardiac disorder. Postexercise NCS appears to result from hypotension due to impaired postexercise vasoconstriction, as well as from hypocapnia. The mechanisms of postexercise hypotension can be divided into obligatory (which are always present and include sympathoinhibition, histaminergic vasodilation, and downregulation of cardiovagal baroreflex) and situational (which include dehydration, hyperthermia and gravitational stress). Regarding postexercise hypocapnia, both hyperventilation during recovery from exercise and orthostasis-induced hypocapnia when recovery occurs in an upright posture can produce postexercise cerebral vasoconstriction. Athletes have been shown to exhibit differential orthostatic responses compared with nonathletes, involving augmented stroke volume and increased peripheral vasodilation in the former, with possibly lower propensity to orthostatic intolerance.
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Affiliation(s)
- Georgios A Christou
- Laboratory of Physiology, Medical School, University of Ioannina, 45110, Ioannina, Greece.
| | | | - Dimitrios N Kiortsis
- Laboratory of Physiology, Medical School, University of Ioannina, 45110, Ioannina, Greece
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Abstract
Breath-hold diving is practiced by recreational divers, seafood divers, military divers, and competitive athletes. It involves highly integrated physiology and extreme responses. This article reviews human breath-hold diving physiology beginning with an historical overview followed by a summary of foundational research and a survey of some contemporary issues. Immersion and cardiovascular adjustments promote a blood shift into the heart and chest vasculature. Autonomic responses include diving bradycardia, peripheral vasoconstriction, and splenic contraction, which help conserve oxygen. Competitive divers use a technique of lung hyperinflation that raises initial volume and airway pressure to facilitate longer apnea times and greater depths. Gas compression at depth leads to sequential alveolar collapse. Airway pressure decreases with depth and becomes negative relative to ambient due to limited chest compliance at low lung volumes, raising the risk of pulmonary injury called "squeeze," characterized by postdive coughing, wheezing, and hemoptysis. Hypoxia and hypercapnia influence the terminal breakpoint beyond which voluntary apnea cannot be sustained. Ascent blackout due to hypoxia is a danger during long breath-holds, and has become common amongst high-level competitors who can suppress their urge to breathe. Decompression sickness due to nitrogen accumulation causing bubble formation can occur after multiple repetitive dives, or after single deep dives during depth record attempts. Humans experience responses similar to those seen in diving mammals, but to a lesser degree. The deepest sled-assisted breath-hold dive was to 214 m. Factors that might determine ultimate human depth capabilities are discussed. © 2018 American Physiological Society. Compr Physiol 8:585-630, 2018.
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Tsuji B, Filingeri D, Honda Y, Eguchi T, Fujii N, Kondo N, Nishiyasu T. Effect of hypocapnia on the sensitivity of hyperthermic hyperventilation and the cerebrovascular response in resting heated humans. J Appl Physiol (1985) 2018; 124:225-233. [DOI: 10.1152/japplphysiol.00232.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Elevating core temperature at rest causes increases in minute ventilation (V̇e), which lead to reductions in both arterial CO2 partial pressure (hypocapnia) and cerebral blood flow. We tested the hypothesis that in resting heated humans this hypocapnia diminishes the ventilatory sensitivity to rising core temperature but does not explain a large portion of the decrease in cerebral blood flow. Fourteen healthy men were passively heated using hot-water immersion (41°C) combined with a water-perfused suit, which caused esophageal temperature (Tes) to reach 39°C. During heating in two separate trials, end-tidal CO2 partial pressure decreased from the level before heating (39.4 ± 2.0 mmHg) to the end of heating (30.5 ± 6.3 mmHg) ( P = 0.005) in the Control trial. This decrease was prevented by breathing CO2-enriched air throughout the heating such that end-tidal CO2 partial pressure did not differ between the beginning (39.8 ± 1.5 mmHg) and end (40.9 ± 2.7 mmHg) of heating ( P = 1.00). The sensitivity to rising Tes (i.e., slope of the Tes − V̇E relation) did not differ between the Control and CO2-breathing trials (37.1 ± 43.1 vs. 16.5 ± 11.1 l·min−1·°C−1, P = 0.31). In both trials, middle cerebral artery blood velocity (MCAV) decreased early during heating (all P < 0.01), despite the absence of hyperventilation-induced hypocapnia. CO2 breathing increased MCAV relative to Control at the end of heating ( P = 0.005) and explained 36.6% of the heat-induced reduction in MCAV. These results indicate that during passive heating at rest ventilatory sensitivity to rising core temperature is not suppressed by hypocapnia and that most of the decrease in cerebral blood flow occurs independently of hypocapnia. NEW & NOTEWORTHY Hyperthermia causes hyperventilation and concomitant hypocapnia and cerebral hypoperfusion. The last may underlie central fatigue. We are the first to demonstrate that hyperthermia-induced hyperventilation is not suppressed by the resultant hypocapnia and that hypocapnia explains only 36% of cerebral hypoperfusion elicited by hyperthermia. These new findings advance our understanding of the mechanisms controlling ventilation and cerebral blood flow during heat stress, which may be useful for developing interventions aimed at preventing central fatigue during hyperthermia.
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Affiliation(s)
- Bun Tsuji
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Ibaraki, Japan
- Department of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
| | - Davide Filingeri
- Environmental Ergonomics Research Centre, Loughborough Design School, Loughborough University, Loughborough, United Kingdom
| | - Yasushi Honda
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Ibaraki, Japan
| | - Tsubasa Eguchi
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Ibaraki, Japan
| | - Naoto Fujii
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Ibaraki, Japan
| | - Narihiko Kondo
- Faculty of Human Development, Kobe University, Kobe, Japan
| | - Takeshi Nishiyasu
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Ibaraki, Japan
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Mueller PJ, Clifford PS, Crandall CG, Smith SA, Fadel PJ. Integration of Central and Peripheral Regulation of the Circulation during Exercise: Acute and Chronic Adaptations. Compr Physiol 2017; 8:103-151. [DOI: 10.1002/cphy.c160040] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Beaudin AE, Hartmann SE, Pun M, Poulin MJ. Human cerebral blood flow control during hypoxia: focus on chronic pulmonary obstructive disease and obstructive sleep apnea. J Appl Physiol (1985) 2017; 123:1350-1361. [DOI: 10.1152/japplphysiol.00352.2017] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Revised: 08/01/2017] [Accepted: 08/07/2017] [Indexed: 01/06/2023] Open
Abstract
The brain is a vital organ that relies on a constant and adequate blood flow to match oxygen and glucose delivery with the local metabolic demands of active neurons. Thus exquisite regulation of cerebral blood flow (CBF) is particularly important under hypoxic conditions to prevent a detrimental decrease in the partial pressure of oxygen within the brain tissues. Cerebrovascular sensitivity to hypoxia, assessed as the change in CBF during a hypoxic challenge, represents the capacity of cerebral vessels to respond to, and compensate for, a reduced oxygen supply, and has been shown to be impaired or blunted in a number of conditions. For instance, this is observed with aging, and in clinical conditions such as untreated obstructive sleep apnea (OSA) and in healthy humans exposed to intermittent hypoxia. This review will 1) provide a brief overview of cerebral blood flow regulation and results of pharmacological intervention studies which we have performed to better elucidate the basic mechanisms of cerebrovascular regulation in humans; and 2) present data from studies in clinical and healthy populations, using a translational physiology approach, to investigate human CBF control during hypoxia. Results from studies in patients with chronic obstructive pulmonary disease and OSA will be presented to identify the effects of the disease processes on cerebrovascular sensitivity to hypoxia. Data emerging from experimental human models of intermittent hypoxia during wakefulness will also be reviewed to highlight the effects of intermittent hypoxia on the brain.
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Affiliation(s)
- Andrew E. Beaudin
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Sara E. Hartmann
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Matiram Pun
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Marc J. Poulin
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada; and
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
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Hurr C, Patik JC, Kim K, Brothers RM. Blunted cerebral vascular responsiveness to hypercapnia in obese individuals. Exp Physiol 2017; 102:1300-1308. [DOI: 10.1113/ep086446] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Accepted: 07/18/2017] [Indexed: 11/08/2022]
Affiliation(s)
- Chansol Hurr
- Department of Kinesiology and Health Education; University of Texas at Austin; Austin TX USA
- Department of Pharmacology and Physiology; George Washington University; DC USA
| | - Jordan C. Patik
- Department of Kinesiology and Health Education; University of Texas at Austin; Austin TX USA
- Department of Kinesiology; University of Texas at Arlington; Arlington TX USA
| | - KiYoung Kim
- Department of Kinesiology and Health Education; University of Texas at Austin; Austin TX USA
- Department of Pathology; University of Alabama at Birmingham; Birmingham AL USA
| | - R. Matthew Brothers
- Department of Kinesiology and Health Education; University of Texas at Austin; Austin TX USA
- Department of Kinesiology; University of Texas at Arlington; Arlington TX USA
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Bronzwaer ASGT, Verbree J, Stok WJ, Daemen MJAP, van Buchem MA, van Osch MJP, van Lieshout JJ. The cerebrovascular response to lower-body negative pressure vs. head-up tilt. J Appl Physiol (1985) 2017; 122:877-883. [PMID: 28082333 DOI: 10.1152/japplphysiol.00797.2016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Revised: 01/05/2017] [Accepted: 01/05/2017] [Indexed: 11/22/2022] Open
Abstract
Lower-body negative pressure (LBNP) has been proposed as a MRI-compatible surrogate for orthostatic stress. Although the effects of LBNP on cerebral hemodynamic behavior have been considered to reflect those of orthostatic stress, a direct comparison with actual orthostasis is lacking. We assessed the effects of LBNP (-50 mmHg) vs. head-up tilt (HUT; at 70°) in 10 healthy subjects (5 female) on transcranial Doppler-determined cerebral blood flow velocity (CBFv) in the middle cerebral artery and cerebral perfusion pressure (CPP) as estimated from the blood pressure signal (finger plethysmography). CPP was maintained during LBNP but decreased after 2 min in response to HUT, leading to an ~15% difference in CPP between LBNP and HUT (P ≤ 0.020). Mean CBFv initially decreased similarly in response to LBNP and for HUT, but, from minute 3 on, the decline became ~50% smaller (P ≤ 0.029) during LBNP. The reduction in end-tidal Pco2 partial pressure (PetCO2 ) was comparable but with an earlier return toward baseline values in response to LBNP but not during HUT (P = 0.008). We consider the larger decrease in CBFv during HUT vs. LBNP attributable to the pronounced reduction in PetCO2 and to gravitational influences on CPP, and this should be taken into account when applying LBNP as an MRI-compatible orthostatic stress modality.NEW & NOTEWORTHY Lower-body negative pressure (LBNP) has the potential to serve as a MRI-compatible surrogate of orthostatic stress but a comparison with actual orthostasis was lacking. This study showed that the pronounced reduction in end-tidal Pco2 together with gravitational effects on the brain circulation lead to a larger decline in cerebral blood flow velocity in response to head-up tilt than during lower-body negative pressure. This should be taken into account when employing lower-body negative pressure as MRI-compatible alternative to orthostatic stress.
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Affiliation(s)
- Anne-Sophie G T Bronzwaer
- Department of Internal Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.,Laboratory for Clinical Cardiovascular Physiology, Center for Heart Failure Research, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
| | - Jasper Verbree
- Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands
| | - Wim J Stok
- Laboratory for Clinical Cardiovascular Physiology, Center for Heart Failure Research, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.,Department of Anatomy, Embryology and Physiology, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
| | - Mat J A P Daemen
- Department of Pathology, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands; and
| | - Mark A van Buchem
- Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands
| | | | - Johannes J van Lieshout
- Department of Internal Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands; .,Laboratory for Clinical Cardiovascular Physiology, Center for Heart Failure Research, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.,Department of Anatomy, Embryology and Physiology, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.,Medical Research Center/Arthritis Research United Kingdom Centre for Musculoskeletal Ageing Research, School of Life Sciences, University of Nottingham Medical School, Queen's Medical Centre, Nottingham, United Kingdom
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Skytioti M, Søvik S, Elstad M. Internal carotid artery blood flow in healthy awake subjects is reduced by simulated hypovolemia and noninvasive mechanical ventilation. Physiol Rep 2016; 4:e12969. [PMID: 27702883 PMCID: PMC5064133 DOI: 10.14814/phy2.12969] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 08/20/2016] [Accepted: 08/22/2016] [Indexed: 02/02/2023] Open
Abstract
Intact cerebral blood flow (CBF) is essential for cerebral metabolism and function, whereas hypoperfusion in relation to hypovolemia and hypocapnia can lead to severe cerebral damage. This study was designed to assess internal carotid artery blood flow (ICA-BF) during simulated hypovolemia and noninvasive positive pressure ventilation (PPV) in young healthy humans. Beat-by-beat blood velocity (ICA and aorta) were measured by Doppler ultrasound during normovolemia and simulated hypovolemia (lower body negative pressure), with or without PPV in 15 awake subjects. Heart rate, plethysmographic finger arterial pressure, respiratory frequency, and end-tidal CO2 (ETCO2) were also recorded. Cardiac index (CI) and ICA-BF were calculated beat-by-beat. Medians and 95% confidence intervals and Wilcoxon signed rank test for paired samples were used to test the difference between conditions. Effects on ICA-BF were modeled by linear mixed-effects regression analysis. During spontaneous breathing, ICA-BF was reduced from normovolemia (247, 202-284 mL/min) to hypovolemia (218, 194-271 mL/min). During combined PPV and hypovolemia, ICA-BF decreased by 15% (200, 152-231 mL/min, P = 0.001). Regression analysis attributed this fall to concurrent reductions in CI (β: 43.2, SE: 17.1, P = 0.013) and ETCO2 (β: 32.8, SE: 9.3, P = 0.001). Mean arterial pressure was maintained and did not contribute to ICA-BF variance. In healthy awake subjects, ICA-BF was significantly reduced during simulated hypovolemia combined with noninvasive PPV Reductions in CI and ETCO2 had additive effects on ICA-BF reduction. In hypovolemic patients, even low-pressure noninvasive ventilation may cause clinically relevant reductions in CBF, despite maintained arterial blood pressure.
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Affiliation(s)
- Maria Skytioti
- Division of Physiology, Institute of Basic Medical Sciences University of Oslo, Oslo, Norway
| | - Signe Søvik
- Deptartment of Anaesthesia and Intensive Care, Akershus University Hospital, Lørenskog, Norway
| | - Maja Elstad
- Division of Physiology, Institute of Basic Medical Sciences University of Oslo, Oslo, Norway
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Abstract
Cerebral blood flow (CBF) regulation is an indicator of cerebrovascular health increasingly recognized as being influenced by physical activity. Although regular exercise is recommended during healthy pregnancy, the effects of exercise on CBF regulation during this critical period of important blood flow increase and redistribution remain incompletely understood. Moreover, only a few studies have evaluated the effects of human pregnancy on CBF regulation. The present work summarizes current knowledge on CBF regulation in humans at rest and during aerobic exercise in relation to healthy pregnancy. Important gaps in the literature are highlighted, emphasizing the need to conduct well-designed studies assessing cerebrovascular function before, during and after this crucial life period to evaluate the potential cerebrovascular risks and benefits of exercise during pregnancy.
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Weiler M, Agosta F, Canu E, Copetti M, Magnani G, Marcone A, Pagani E, Balthazar MLF, Comi G, Falini A, Filippi M. Following the Spreading of Brain Structural Changes in Alzheimer's Disease: A Longitudinal, Multimodal MRI Study. J Alzheimers Dis 2016; 47:995-1007. [PMID: 26401778 DOI: 10.3233/jad-150196] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND Longitudinal MRI studies in Alzheimer's disease (AD) are one of the most reliable way to track brain changes along the course of the disease. OBJECTIVE To investigate the evolution of grey matter (GM) atrophy and white matter (WM) damage in AD patients, and to assess the relationships of MRI changes with baseline clinical and cognitive variables and their evolution over time. METHODS Clinical, neuropsychological, and MRI assessments (T1-weighted and diffusion tensor [DT]-MRI) were obtained from 14 patients with AD at baseline and after a 16 ± 3 month period. Lumbar puncture was obtained at study entry. At baseline, AD patients were compared to 37 controls. GM atrophy progression was assessed with tensor-based morphometry and GM volumes of interest, and WM damage progression using tract-based spatial statistics and tractography. RESULTS At baseline, patients showed cortical atrophy in the medial temporal and parietal regions and a widespread pattern of WM damage involving the corpus callosum, cingulum, and temporo-occipital, parietal, and frontal WM tracts. During follow up, AD patients showed total GM atrophy, while total WM volume did not change. GM tissue loss was found in frontal, temporal, and parietal regions. In addition, AD patients showed a progression of WM microstructural damage to the corpus callosum, cingulum, fronto-parietal and temporo-occipital connections bilaterally. Patients with higher baseline cerebrospinal fluid total tau showed greater WM integrity loss at follow up. GM and WM changes over time did not correlate with each other nor with cognitive evolution. CONCLUSION In AD, GM atrophy and WM tract damage are likely to progress, at least partially, independently. This study suggests that a multimodal imaging approach, which includes both T1-weighted and DT MR imaging, may provide additional markers to monitor disease progression.
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Affiliation(s)
- Marina Weiler
- Neuroimaging Research Unit, Institute of Experimental Neurology, Division of Neuroscience, San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milan, Italy.,Laboratory of Neuroimaging, University of Campinas, Campinas, Brazil
| | - Federica Agosta
- Neuroimaging Research Unit, Institute of Experimental Neurology, Division of Neuroscience, San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milan, Italy
| | - Elisa Canu
- Neuroimaging Research Unit, Institute of Experimental Neurology, Division of Neuroscience, San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milan, Italy
| | - Massimiliano Copetti
- Biostatistics Unit, IRCCS-Ospedale Casa Sollievo della Sofferenza, San Giovanni Rotondo, Foggia, Italy
| | - Giuseppe Magnani
- Department of Neurology, Institute of Experimental Neurology, Division of Neuroscience, San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milan, Italy
| | - Alessandra Marcone
- Department of Clinical Neurosciences, Division of Neuroscience, San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milan, Italy
| | - Elisabetta Pagani
- Neuroimaging Research Unit, Institute of Experimental Neurology, Division of Neuroscience, San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milan, Italy
| | | | - Giancarlo Comi
- Department of Neurology, Institute of Experimental Neurology, Division of Neuroscience, San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milan, Italy
| | - Andrea Falini
- Department of Neuroradiology and CERMAC, Division of Neuroscience, San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milan, Italy
| | - Massimo Filippi
- Neuroimaging Research Unit, Institute of Experimental Neurology, Division of Neuroscience, San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milan, Italy.,Department of Neurology, Institute of Experimental Neurology, Division of Neuroscience, San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milan, Italy
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47
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Maa T, Yeates KO, Moore-Clingenpeel M, O'Brien NF. Age-related carbon dioxide reactivity in children after moderate and severe traumatic brain injury. J Neurosurg Pediatr 2016; 18:73-8. [PMID: 27035550 DOI: 10.3171/2016.1.peds15564] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECTIVE The objective of this study is to assess carbon dioxide reactivity (CO2R) in children following traumatic brain injury (TBI). METHODS This prospective observational study enrolled children younger than 18 years old following moderate and severe TBI. Thirty-eight mechanically ventilated children had daily CO2R testing performed by measuring changes in their bilateral middle cerebral artery flow velocities using transcranial Doppler ultrasonography (TCD) after a transient increase in minute ventilation. The cohort was divided into 3 age groups: younger than 2 years (n = 12); 2 to 5 years old (n = 9); and older than 5 years (n = 17). RESULTS Children younger than 2 years old had a lower mean CO2R over time. The 2-5-year-old age group had higher mean CO2R than younger patients (p = 0.01), and the highest CO2R values compared with either of the other age groups (vs > 5 years old, p = 0.046; vs < 2 years old, p = 0.002). Having a lower minimum CO2R had a statistically significant negative effect on outcome at discharge (p = 0.0413). Impaired CO2R beyond Postinjury Day 4 trended toward having an effect on outcome at discharge (p = 0.0855). CONCLUSIONS Abnormal CO2R is prevalent in children following TBI, and the degree of impairment varies by age. No clinical or laboratory parameters were identified as risk factors for impaired CO2R. Lower minimum CO2R values are associated with worse outcome at discharge.
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Jeong SM, Kim SO, DeLorey DS, Babb TG, Levine BD, Zhang R. Lack of correlation between cerebral vasomotor reactivity and dynamic cerebral autoregulation during stepwise increases in inspired CO2 concentration. J Appl Physiol (1985) 2016; 120:1434-41. [PMID: 27103653 DOI: 10.1152/japplphysiol.00390.2015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Accepted: 04/18/2016] [Indexed: 11/22/2022] Open
Abstract
Cerebral vasomotor reactivity (CVMR) and dynamic cerebral autoregulation (CA) are measured extensively in clinical and research studies. However, the relationship between these measurements of cerebrovascular function is not well understood. In this study, we measured changes in cerebral blood flow velocity (CBFV) and arterial blood pressure (BP) in response to stepwise increases in inspired CO2 concentrations of 3 and 6% to assess CVMR and dynamic CA in 13 healthy young adults [2 women, 32 ± 9 (SD) yr]. CVMR was assessed as percentage changes in CBFV (CVMRCBFV) or cerebrovascular conductance index (CVCi, CVMRCVCi) in response to hypercapnia. Dynamic CA was estimated by performing transfer function analysis between spontaneous oscillations in BP and CBFV. Steady-state CBFV and CVCi both increased exponentially during hypercapnia; CVMRCBFV and CVMRCVCi were greater at 6% (3.85 ± 0.90 and 2.45 ± 0.79%/mmHg) than at 3% CO2 (2.09 ± 1.47 and 0.21 ± 1.56%/mmHg, P = 0.009 and 0.005, respectively). Furthermore, CVMRCBFV was greater than CVMRCVCi during either 3 or 6% CO2 (P = 0.017 and P < 0.001, respectively). Transfer function gain and coherence increased in the very low frequency range (0.02-0.07 Hz), and phase decreased in the low-frequency range (0.07-0.20 Hz) when breathing 6%, but not 3% CO2 There were no correlations between the measurements of CVMR and dynamic CA. These findings demonstrated influences of inspired CO2 concentrations on assessment of CVMR and dynamic CA. The lack of correlation between CVMR and dynamic CA suggests that cerebrovascular responses to changes in arterial CO2 and BP are mediated by distinct regulatory mechanisms.
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Affiliation(s)
- Sung-Moon Jeong
- Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas and University of Texas Southwestern Medical Center, Dallas, Texas; Department of Anesthesiology and Pain Medicine, College of Medicine, University of Ulsan, Asan Medical Center, Seoul, Korea
| | - Seon-Ok Kim
- Department of Clinical Epidemiology and Biostatistics, College of Medicine, University of Ulsan, Asan Medical Center, Seoul, Korea; and
| | - Darren S DeLorey
- Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Tony G Babb
- Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas and University of Texas Southwestern Medical Center, Dallas, Texas
| | - Benjamin D Levine
- Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas and University of Texas Southwestern Medical Center, Dallas, Texas
| | - Rong Zhang
- Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas and University of Texas Southwestern Medical Center, Dallas, Texas;
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50
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Hoiland RL, Tymko MM, Bain AR, Wildfong KW, Monteleone B, Ainslie PN. Carbon dioxide-mediated vasomotion of extra-cranial cerebral arteries in humans: a role for prostaglandins? J Physiol 2016; 594:3463-81. [PMID: 26880615 DOI: 10.1113/jp272012] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 02/01/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Cerebral blood flow increases during hypercapnia and decreases during hypocapnia; it is unknown if vasomotion of the internal carotid artery is implicated in these responses. Indomethacin, a non-selective cyclooxygenase inhibitor (used to inhibit prostaglandin synthesis), has a unique ability to blunt cerebrovascular carbon dioxide reactivity, while other cyclooxygenase inhibitors have no effect. We show significant dilatation and constriction of the internal carotid artery during hypercapnia and hypocapnia, respectively. Indomethacin, but not ketorolac or naproxen, reduced the dilatatory response of the internal carotid artery to hypercapnia The differential effect of indomethacin compared to ketorolac and naproxen suggests that indomethacin inhibits vasomotion of the internal carotid artery independent of prostaglandin synthesis inhibition. ABSTRACT Extra-cranial cerebral blood vessels are implicated in the regulation of cerebral blood flow during changes in arterial CO2 ; however, the mechanisms governing CO2 -mediated vasomotion of these vessels in humans remain unclear. We determined if cyclooxygenase inhibition with indomethacin (INDO) reduces the vasomotor response of the internal carotid artery (ICA) to changes in end-tidal CO2 (P ETC O2). Using a randomized single-blinded placebo-controlled study, participants (n = 10) were tested on two occasions, before and 90 min following oral INDO (1.2 mg kg(-1) ) or placebo. Concurrent measurements of beat-by-beat velocity, diameter and blood flow of the ICA were made at rest and during steady-state stages (4 min) of iso-oxic hypercapnia (+3, +6, +9 mmHg P ETC O2) and hypocapnia (-3, -6, -9 mmHg P ETC O2). To examine if INDO affects ICA vasomotion independent of cyclooxygenase inhibition, two participant subsets (each n = 5) were tested before and following oral ketorolac (post 45 min, 0.25 mg kg(-1) ) or naproxen (post 90 min, 4.2 mg kg(-1) ). During pre-drug testing in the INDO trial, the ICA dilatated during hypercapnia at +6 mmHg (4.72 ± 0.45 vs. 4.95 ± 0.51 mm; P < 0.001) and +9 mmHg (4.72 ± 0.45 mm vs. 5.12 ± 0.47 mm; P < 0.001), and constricted during hypocapnia at -6 mmHg (4.95 ± 0.33 vs. 4.88 ± 0.27 mm; P < 0.05) and -9 mmHg (4.95 ± 0.33 vs. 4.82 ± 0.27 mm; P < 0.001). Following INDO, vasomotor responsiveness of the ICA to hypercapnia was reduced by 67 ± 28% (0.045 ± 0.015 vs. 0.015 ± 0.012 mm mmHg P ETC O2(-1) ). There was no effect of the drug in the ketorolac and naproxen trials. We conclude that: (1) INDO markedly reduces the vasomotor response of the ICA to changes in P ETC O2; and (2) INDO may be reducing CO2 -mediated vasomotion via a mechanism(s) independent of cyclooxygenase inhibition.
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Affiliation(s)
- Ryan L Hoiland
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, Kelowna, BC, Canada
| | - Michael M Tymko
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, Kelowna, BC, Canada
| | - Anthony R Bain
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, Kelowna, BC, Canada
| | - Kevin W Wildfong
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, Kelowna, BC, Canada
| | - Brad Monteleone
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, Kelowna, BC, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, Kelowna, BC, Canada
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