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1.
Neurology ; 97(22): e2204-e2212, 2021 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-34635563

RESUMO

BACKGROUND AND OBJECTIVES: Aerobic exercise has become a useful method to assist with postconcussion management. Exercise can exacerbate concussion symptoms even when symptoms are not apparent at rest. Few studies have examined the reasons for symptom exacerbation during exercise following a concussion. We had 2 primary objectives: (1) to delineate cardiopulmonary and cerebrovascular responses to exercise in adolescents and young adults with a concussion and healthy controls and (2) to determine the association between cerebrovascular responses and symptom burden. METHODS: We recruited participants with a recent concussion from a sport concussion clinic between September 1, 2018, and February 22, 2020. They were included if their concussion occurred <3 weeks before initial testing and if they were symptomatic at rest. Participants were excluded if they sustained a concussion in the past year (excluding index injury), reported history of neurologic disorders, or were using medications/devices that may alter neurologic function. Participants completed a progressive, symptom-limited, submaximal exercise protocol on a stationary bicycle. We assessed heart rate, blood pressure, fraction of end tidal CO2 (FETCO2), and middle cerebral artery blood flow velocity (CBF) and cerebrovascular function (vasoactivity and autoregulation) at seated rest and during exercise. RESULTS: We conducted 107 exercise tests (40 concussed, 37 healthy participants initially; 30 concussed at follow-up). Concussed participants were tested initially (mean 17.6 ± 2.2 [SD] years of age; 55% female; mean 12.5 ± 4.7 days postconcussion) and again 8 weeks later (mean 73.3 ± 9.5 days postconcussion). Control participants (mean 18.3 ± 2.4 years; 62% female) were tested once. FETCO2 increased throughout the exercise protocol as heart rate increased, reached a plateau, and declined at higher exercise intensities. CO2 explained >25% of the variation in resting CBF (R 2 > 0.25; p < 0.01) in most (73% individuals). Within the concussion group, resting symptom severity and the heart rate at which FETCO2 reached a plateau explained ∼2/3s of variation in exercise-induced symptom exacerbation (R 2 = 0.65; FETCO2 ß = -1.210 ± 0.517 [SE], p < 0.05). There was a moderate, statistically significant relationship between cerebrovascular responses to CO2 at rest (cerebral vasoactivity) and cerebrovascular responses to exercise-induced changes in FETCO2 (R 2 = 0.13, p = 0.01). DISCUSSION: The arterial CO2 response and symptom exacerbation relationship during postconcussion aerobic exercise may be mediated by increased sensitivity of cerebral vasculature to exercise-related increase in CO2.

2.
Physiol Meas ; 42(9)2021 09 27.
Artigo em Inglês | MEDLINE | ID: mdl-34450608

RESUMO

Objective.We investigated the relation between prior concussion history and working memory (WM), self-reported cognitive symptom burden, and cerebrovascular function in adolescents and young adults (14-21 years old).Approach.We recruited 59 participants, 34 clinically diagnosed with a sports-related concussion and 25 controls. Concussed subjects were studied at baseline (within 28 days of their injury) and eight weeks after, while control subjects only had one assessment. We assessed WM (n-back task up to four-back), and neurovascular coupling (cerebrovascular responses at middle cerebral artery duringn-back tasks) using a transcranial Doppler ultrasonograph.Main results.There was no significant difference in WM between controls and concussed participants (p = 0.402). However, WM capacity was lower in those who had sustained ≥3 concussions (7.1% with WM capacity of four) compared to those with their first ever concussion (33.3%) and controls (28.0%, overallp = 0.025). At the sub-acute point (n = 24), self-reported cognitive symptom burden was mostly resolved in all but two participants. Despite the resolution of symptoms, WM performance was not different eight weeks post injury (p = 0.706). Neurovascular coupling was not different between controls and concussed participants regardless of prior concussion history.Significance. Up to 20% of concussed individuals experience covert sequelae lasting beyond the resolution of self-reported overt symptoms. How a prior history of concussion impacts the potential for sequelae is not well established, and the underlying mechanisms are unknown. Despite no alterations in neurovascular coupling, a history of prior concussion was associated with significant deficits in WM capacity, and lasted beyond self-reported cognitive symptom resolution.


Assuntos
Concussão Encefálica , Acoplamento Neurovascular , Adolescente , Adulto , Concussão Encefálica/complicações , Cognição , Humanos , Memória de Curto Prazo , Testes Neuropsicológicos , Adulto Jovem
3.
Ann Neurol ; 90(1): 43-51, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33855730

RESUMO

OBJECTIVE: To assess acute cerebrovascular function in concussed adolescents (14-21 years of age), whether it is related to resting cerebral hemodynamics, and whether it recovers chronically. METHODS: Cerebral vasoreactivity and autoregulation, based on middle cerebral artery blood flow velocity, was assessed in 28 concussed participants (≤14 days of injury) and 29 matched controls. The participants in the concussion group returned for an 8-week follow-up assessment. Over the course of those 8-weeks, participants recorded aerobic exercise frequency and duration. RESULTS: Between groups, demographic, clinical, and hemodynamic variables were not significantly different. Vasoreactivity was significantly higher in the concussed group (p = 0.02). Within the concussed group, 60% of the variability in resting cerebral blood flow velocity was explained by vasoreactivity and two components of autoregulation - falling slope and effectiveness of autoregulation (adjusted R2  = 0.60, p < 0.001). Moreover, lower mean arterial pressure, lower responses to increases in arterial pressure, and lower vasoreactivity were significantly associated with larger symptom burden (adjusted R2  = 0.72, p < 0.01). By the 8-week timepoint, symptom burden, but not vasoreactivity, improved in all but four concussed participants (p < 0.01). 8-week change in vasoreactivity was positively associated with aerobic exercise volume (adjusted R2  = 0.19, p = 0.02). INTERPRETATION: Concussion resulted in changes in cerebrovascular regulatory mechanisms, which in turn explained the variability in resting cerebral blood flow velocity and acute symptom burden. Furthermore, these alterations persisted chronically despite symptom resolution, but was positively modified by aerobic exercise volume. These findings provide a mechanistic framework for further investigation into underlying cerebrovascular related symptomatology. ANN NEUROL 2021;90:43-51.


Assuntos
Concussão Encefálica/fisiopatologia , Circulação Cerebrovascular/fisiologia , Hemodinâmica/fisiologia , Neuroproteção/fisiologia , Adolescente , Velocidade do Fluxo Sanguíneo/fisiologia , Feminino , Seguimentos , Homeostase/fisiologia , Humanos , Masculino , Adulto Jovem
4.
PLoS One ; 16(3): e0247576, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33661958

RESUMO

Blood pressure regulation following spinal cord injury (SCI) is often compromised due to impaired vascular sympathetic control, leading to increased reliance on cardiovagal baroreflex sensitivity to maintain pressure. Whole-body exercise improves cardiovagal baroreflex sensitivity in uninjured individuals, though has not been explored in those with SCI. Our objective was to determine changes in cardiovagal baroreflex sensitivity following 6 months of high-intensity, whole-body exercise in individuals with SCI compared to lower-intensity, arms only exercise, or waitlist. This randomized controlled trial recruited individuals with SCI aged 18-40 years old. Sixty-one individuals were randomized, with 38 completing at least one cardiovagal baroreflex sensitivity assessment. Whole-body exercise was performed with hybrid functional electrical stimulation rowing prescribed as two to three times per week, for 30-60 minutes with a target heart rate of >75% of maximum. The arms only exercise group performed upper body rowing exercise with the same prescription as whole-body exercise. Waitlist controls were not enrolled in any explicit training regimen. After 6 months, those in arms only exercise or waitlist crossed over to whole-body exercise. Cardiovagal baroreflex sensitivity was assessed via the neck suction technique at baseline and at three-month intervals thereafter. Intention to treat analysis with a structured equation model demonstrated no significant effect of waitlist control or arms only exercise on cardiovagal baroreflex sensitivity. Whole-body exercise significantly improved cardiovagal baroreflex sensitivity at 6 months for those initially randomized (p = 0.03), as well as those who crossed over from arms only exercise or waitlist control (p = 0.03 for each). However, amount of exercise performed and aerobic gains (VO2max) each poorly correlated with increases in cardiovagal baroreflex sensitivity (R2<0.15). In post-hoc analyses, individuals with paraplegia made significantly greater gains in baroreflex sensitivity compared to those with tetraplegia (p = 0.02), though gains within this group were again poorly correlated to gains in aerobic capacity. Clinicaltrials.gov number NCT02139436.


Assuntos
Pressão Sanguínea/fisiologia , Terapia por Exercício/métodos , Exercício Físico/fisiologia , Traumatismos da Medula Espinal/terapia , Adolescente , Adulto , Barorreflexo/fisiologia , Feminino , Frequência Cardíaca/fisiologia , Humanos , Masculino , Avaliação de Resultados em Cuidados de Saúde , Consumo de Oxigênio/fisiologia , Estudos Prospectivos , Traumatismos da Medula Espinal/fisiopatologia , Fatores de Tempo , Adulto Jovem
5.
Am J Phys Med Rehabil ; 99(12): 1138-1144, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-32576743

RESUMO

OBJECTIVE: The aim of the study was to explore feasibility of smartphone-based digital phenotyping methods to examine depression and its relation to psychosocial well-being indicators after spinal cord injury. DESIGN: Smartphone research platform obtained smartphone sensor and survey data among community-living adult wheelchair users with spinal cord injury. Weekly measurements for 4 mos included Patient Health Questionnaire 8, Spinal Cord Injury-Quality of Life Satisfaction with and ability to participate in social roles and activities, global positioning system-derived community mobility metrics, health conditions, and physical activity. RESULTS: Forty-three individuals were enrolled. Study retention was higher among individuals offered financial incentives (78%) compared with participants enrolled before incentives (50%). Participants who dropped out more commonly had nontraumatic or acute spinal cord injury, were older, and had less satisfaction and lower participation in social roles and activities. Among 15 individuals with complete data, half had 1 wk or more of mild depression. Those with depression had frequent health issues, less satisfaction, and lower participation in social roles and activities. Those without depression experienced increased social engagement over time. Average community mobility was similar across depression groups. Relationships were typically in-phase but also varied by individual. CONCLUSIONS: Smartphone-based digital phenotyping of psychosocial well-being after spinal cord injury is feasible but not without attrition challenges. Individual differences in depression patterns highlight clinical utility of scaling these methods.


Assuntos
Depressão/diagnóstico , Aplicativos Móveis , Qualidade de Vida , Smartphone , Participação Social , Traumatismos da Medula Espinal/psicologia , Adulto , Depressão/etiologia , Estudos de Viabilidade , Feminino , Sistemas de Informação Geográfica , Humanos , Masculino , Pessoa de Meia-Idade , Satisfação Pessoal , Inquéritos e Questionários , Cadeiras de Rodas
6.
J Appl Physiol (1985) ; 124(2): 321-329, 2018 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-29025902

RESUMO

Postural changes impair the ability of the cerebrovasculature to buffer against dynamic pressure fluctuations, but the mechanisms underlying this impairment have not been elucidated. We hypothesized that autoregulatory impairment may reflect the impact of static central volume shifts on hemodynamic factors other than arterial pressure (AP). In 14 young volunteers, we assessed the relation of fluctuations in cerebral blood flow (CBF) to those in AP, cardiac output, and CO2, during oscillatory lower body pressure (LBP) (±20 mmHg at 0.01 and 0.06 Hz) at three static levels (-20, 0, and +20 mmHg). Static and dynamic changes in AP, cardiac output, and CO2 explained over 70% of the variation in CBF fluctuations. However, their contributions were different across frequencies and levels: dynamic AP changes explained a substantial proportion of the variation in faster CBF fluctuations (partial R2 = 0.75, standardized ß = 0.83, P < 0.01), whereas those in CO2 explained the largest portion of the variation in slow fluctuations (partial R2 = 0.43, ß = 0.51, P < 0.01). There was, however, a major contribution of slow dynamic AP changes during negative (ß = 0.43) but not neutral (ß = 0.05) or positive (ß = -0.07) LBP. This highlights the differences in contributions of systemic variables to dynamic and static autoregulation and has important implications for understanding orthostatic intolerance. NEW & NOTEWORTHY While fluctuations in blood pressure drive faster fluctuations in cerebral blood flow, overall level of CO2 and the magnitude of its fluctuations, along with cardiac output, determine the magnitude of slow ones. The effect of slow blood pressure fluctuations on cerebrovascular responses becomes apparent only during pronounced central volume shifts (such as when standing). This underlines distinct but interacting contributions of static and dynamic changes in systemic hemodynamic variables to the cerebrovascular regulation.


Assuntos
Circulação Cerebrovascular , Hipotensão Ortostática/fisiopatologia , Adulto , Pressão Sanguínea , Débito Cardíaco , Deslocamentos de Líquidos Corporais , Voluntários Saudáveis , Homeostase , Humanos , Pressão Negativa da Região Corporal Inferior , Masculino , Adulto Jovem
7.
J Neurotrauma ; 34(19): 2700-2705, 2017 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-28537493

RESUMO

While pathophysiology underlying post-concussion symptom burden is unknown, data suggest that cerebrovascular dysfunction may be among the culprits. We sought to determine whether the degree of impairment in the ability of cerebrovasculature to buffer against changes in arterial gases (vasoreactivity) is associated with concussion symptoms. In 15 participants (19 ± 5 years, 1 week to 1 year post-injury) diagnosed with concussion, we assessed vasoreactivity from the slope of the linear relationship of beat-by-beat middle cerebral artery blood flow velocity (transcranial Doppler ultrasound) to end-tidal CO2 during progressive increases in end-tidal CO2 (air rebreathing). Symptom burden was assessed using the Post-Concussion Symptom Scale. Subsequently, we explored the relationship between vasoreactivity and the severity of post-concussion headache and cognitive difficulties by linear models. During rebreathing, CO2 increased from 32.6 ± 1.6 to 46.8 ± 1.8 mmHg and cerebrovascular conductance (i.e., flow velocity over pressure) increased from 0.48 ± 0.04 to 0.74 ± 0.06 cms-1 mmHg-1. There was a strong linear relationship between the increase in CO2 and in conductance (R2 = 0.81 ± 0.05; p < 0.05). On average, cerebral vasoreactivity was 0.018 ± 0.003 cm-1 s-1 mmHg CO2-1. Although vasoreactivity tended to be somewhat higher in the asymptotic participants (0.019 ± 0.003 vs. 0.015 ± 0.005 cm-1 s-1 mmHg CO2-1), this difference was not statistically significant (p = 0.48). Higher vasoreactivity was strongly associated with more severe headaches (R2 = 0.57; p < 0.01) and worse cognitive symptoms (R2 = 0.71; p < 0.01). Thus, cerebral vasoreactivity relates strongly to post-concussive headache and cognitive symptom burden. This has significant implications for understanding the pathophysiology underlying post-concussive symptom burden and for devising effective treatment options.


Assuntos
Circulação Cerebrovascular/fisiologia , Síndrome Pós-Concussão/fisiopatologia , Vasoconstrição/fisiologia , Vasodilatação/fisiologia , Adolescente , Encéfalo/irrigação sanguínea , Encéfalo/fisiopatologia , Estudos de Coortes , Estudos Transversais , Feminino , Humanos , Masculino , Adulto Jovem
9.
Am J Physiol Regul Integr Comp Physiol ; 304(11): R959-65, 2013 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-23576610

RESUMO

Resting vascular sympathetic outflow is significantly increased during and beyond exposure to acute hypoxia without a parallel increase in either resistance or pressure. This uncoupling may indicate a reduction in the ability of sympathetic outflow to effect vascular responses (sympathetic transduction). However, the effect of hypoxia on sympathetic transduction has not been explored. We hypothesized that transduction would either remain unchanged or be reduced by isocapnic hypoxia. In 11 young healthy individuals, we measured beat-by-beat pressure, multiunit sympathetic nerve activity, and popliteal blood flow velocity at rest and during isometric handgrip exercise to fatigue, before and during isocapnic hypoxia (~80% SpO2), and derived sympathetic transduction for each subject via a transfer function that reflects Poiseuille's law of flow. During hypoxia, heart rate and sympathetic nerve activity increased, whereas pressure and flow remained unchanged. Both normoxic and hypoxic exercise elicited significant increases in heart rate, pressure, and sympathetic activity, although sympathetic responses to hypoxic exercise were blunted. Hypoxia slightly increased the gain relation between pressure and flow (0.062 ± 0.006 vs. 0.074 ± 0.004 cm·s(-1)·mmHg(-1); P = 0.04), but markedly increased sympathetic transduction (-0.024 ± 0.005 vs. -0.042 ± 0.007 cm·s(-1)·spike(-1); P < 0.01). The pressor response to isometric handgrip was similar during normoxic and hypoxic exercise due to the balance of interactions among the tachycardia, sympathoexcitation, and transduction. This indicates that the ability of sympathetic activity to affect vasoconstriction is enhanced during brief exposure to isocapnic hypoxia, and this appears to offset the potent vasodilatory stimulus of hypoxia.


Assuntos
Hipóxia/fisiopatologia , Transdução de Sinais/fisiologia , Sistema Nervoso Simpático/fisiopatologia , Doença Aguda , Adulto , Algoritmos , Pressão Sanguínea/fisiologia , Interpretação Estatística de Dados , Feminino , Mãos/irrigação sanguínea , Mãos/fisiologia , Força da Mão/fisiologia , Frequência Cardíaca/fisiologia , Hemodinâmica/fisiologia , Humanos , Contração Isométrica/fisiologia , Masculino , Fadiga Muscular/fisiologia , Fotopletismografia , Fluxo Sanguíneo Regional/fisiologia , Pele/irrigação sanguínea , Adulto Jovem
10.
J Gerontol A Biol Sci Med Sci ; 58(7): 626-30, 2003 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-12865478

RESUMO

BACKGROUND: Aging is associated with diminished baroreflex sensitivity (gain), which predisposes elderly people to orthostatic hypotension, syncope, and cardiovascular morbidity. Aging is also associated with systolic blood pressure (SBP) elevation and carotid artery stiffness, which may both affect baroreflex gain. METHODS: We examined the relation between SBP, carotid artery stiffness, and baroreflex gain in 34 healthy elderly (71 +/- 4 years) and 10 healthy young (31 +/- 3 years) subjects. SBP (Finapres) and carotid artery stiffness (ultrasound measures of relative carotid artery diameter changes during each blood pressure pulse) were measured. The gain of the transfer function relating the R-R interval to SBP fluctuations at a frequency of 0.05-0.15 Hz was used to assess cardiovagal baroreflex gain. RESULTS: Elderly subjects had higher carotid artery stiffness (14.2 +/- 5.1 vs 6.6 +/- 1.8, p <.05), higher SBP (146 +/- 24 vs 125 +/- 8 mmHg, p =.012), and lower baroreflex gain (8.2 +/- 6.4 vs 16.3 +/- 7.4, p <.05) than young subjects. Among all subjects, SBP and carotid artery stiffness both correlated with baroreflex gain (r = -.39, p =.02 for both). Although SBP was related to stiffness across all subjects, this relation was not present among the elderly subjects. Within the elderly group, only SBP was independently related to baroreflex gain (R(2) =.51, p =.009). CONCLUSIONS: SBP elevation in elderly people may affect the neural or cardiac response to blood pressure fluctuations, independent of the mechanical properties of barosensory regions in the carotid artery. Future studies should examine the effect of pharmacologic treatment of hypertension on baroreflex gain in elderly people.


Assuntos
Envelhecimento/fisiologia , Barorreflexo/fisiologia , Pressão Sanguínea/fisiologia , Artérias Carótidas/fisiologia , Adulto , Idoso , Elasticidade , Humanos , Sístole
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