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Jarrard CP, Watso JC, Atkins WC, McKenna ZJ, Foster J, Huang M, Belval LN, Crandall CG. Sex Differences in Sympathetic Responses to Lower-Body Negative Pressure. Med Sci Sports Exerc 2024; 56:1056-1065. [PMID: 38233995 PMCID: PMC11187698 DOI: 10.1249/mss.0000000000003392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2024]
Abstract
INTRODUCTION Trauma-induced hemorrhage is a leading cause of death in prehospital settings. Experimental data demonstrate that females have a lower tolerance to simulated hemorrhage (i.e., central hypovolemia). However, the mechanism(s) underpinning these responses are unknown. Therefore, this study aimed to compare autonomic cardiovascular responses during central hypovolemia between the sexes. We hypothesized that females would have a lower tolerance and smaller increase in muscle sympathetic nerve activity (MSNA) to simulated hemorrhage. METHODS Data from 17 females and 19 males, aged 19-45 yr, were retrospectively analyzed. Participants completed a progressive lower-body negative pressure (LBNP) protocol to presyncope to simulate hemorrhagic tolerance with continuous measures of MSNA and beat-to-beat hemodynamic variables. We compared responses at baseline, at two LBNP stages (-40 and -50 mmHg), and at immediately before presyncope. In addition, we compared responses at relative percentages (33%, 66%, and 100%) of hemorrhagic tolerance, calculated via the cumulative stress index (i.e., the sum of the product of time and pressure at each LBNP stage). RESULTS Females had lower tolerance to central hypovolemia (female: 561 ± 309 vs male: 894 ± 304 min·mmHg [time·LBNP]; P = 0.003). At LBNP -40 and -50 mmHg, females had lower diastolic blood pressures (main effect of sex: P = 0.010). For the relative LBNP analysis, females exhibited lower MSNA burst frequency (main effect of sex: P = 0.016) accompanied by a lower total vascular conductance (sex: P = 0.028; main effect of sex). CONCLUSIONS Females have a lower tolerance to central hypovolemia, which was accompanied by lower diastolic blood pressure at -40 and -50 mmHg LBNP. Notably, females had attenuated MSNA responses when assessed as relative LBNP tolerance time.
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Affiliation(s)
- Caitlin P. Jarrard
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX
- Applied Clinical Research Department, University of Texas Southwestern Medical Center, Dallas TX
| | - Joseph C. Watso
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX
- Applied Clinical Research Department, University of Texas Southwestern Medical Center, Dallas TX
- College of Health and Human Sciences, Florida State University, Tallahassee, FL
| | - Whitley C. Atkins
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX
| | - Zachary J. McKenna
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX
| | - Josh Foster
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX
- Centre for Human and Applied Physiological Sciences, Faculty of Life Sciences and Medicine, Kings College London, London, UNITED KINGDOM
| | - Mu Huang
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX
- Office of Science, Medicine, and Health, American Heart Association, Dallas, TX
| | - Luke N. Belval
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX
| | - Craig G. Crandall
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX
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Katayama K, Shiozawa K, Lee JB, Seo N, Kondo H, Saito M, Ishida K, Millar PJ, Banno R, Ogoh S. Influence of sex on sympathetic vasomotor outflow responses to passive leg raising in young individuals. J Physiol Sci 2024; 74:19. [PMID: 38500058 PMCID: PMC10949681 DOI: 10.1186/s12576-024-00909-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Accepted: 02/23/2024] [Indexed: 03/20/2024]
Abstract
The purpose of this study was to clarify sex differences in the inhibition of sympathetic vasomotor outflow which is caused by the loading of cardiopulmonary baroreceptors. Ten young males and ten age-matched females participated. The participants underwent a passive leg raising (PLR) test wherein they were positioned supine (baseline, 0º), and their lower limbs were lifted passively at 10º, 20º, 30º, and 40º. Each angle lasted for 3 min. Muscle sympathetic nerve activity (MSNA) was recorded via microneurography of the left radial nerve. Baseline MSNA was lower in females compared to males. MSNA burst frequency was decreased during the PLR in both males (- 6.2 ± 0.4 bursts/min at 40º) and females (- 6.5 ± 0.4 bursts/min at 40º), but no significant difference was detected between the two groups (P = 0.61). These results suggest that sex has minimal influence on the inhibition of sympathetic vasomotor outflow during the loading of cardiopulmonary baroreceptors in young individuals.
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Affiliation(s)
- Keisho Katayama
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, 464-8601, Japan.
- Graduate School of Medicine, Nagoya University, Nagoya, 464-8601, Japan.
| | - Kana Shiozawa
- Graduate School of Medicine, Nagoya University, Nagoya, 464-8601, Japan
- Japan Society for the Promotion of Science, Tokyo, Japan
| | - Jordan B Lee
- Department of Physiology and Pharmacology, University of Calgary, Calgary, Canada
| | - Natsuki Seo
- Graduate School of Medicine, Nagoya University, Nagoya, 464-8601, Japan
| | - Haruna Kondo
- Graduate School of Medicine, Nagoya University, Nagoya, 464-8601, Japan
| | - Mitsuru Saito
- Applied Physiology Laboratory, Toyota Technological Institute, Nagoya, Japan
| | - Koji Ishida
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, 464-8601, Japan
- Graduate School of Medicine, Nagoya University, Nagoya, 464-8601, Japan
| | - Philip J Millar
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Canada
| | - Ryoichi Banno
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, 464-8601, Japan
- Graduate School of Medicine, Nagoya University, Nagoya, 464-8601, Japan
| | - Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, Kawagoe, Japan
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3
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Raberin A, Burtscher J, Citherlet T, Manferdelli G, Krumm B, Bourdillon N, Antero J, Rasica L, Malatesta D, Brocherie F, Burtscher M, Millet GP. Women at Altitude: Sex-Related Physiological Responses to Exercise in Hypoxia. Sports Med 2024; 54:271-287. [PMID: 37902936 PMCID: PMC10933174 DOI: 10.1007/s40279-023-01954-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/09/2023] [Indexed: 11/01/2023]
Abstract
Sex differences in physiological responses to various stressors, including exercise, have been well documented. However, the specific impact of these differences on exposure to hypoxia, both at rest and during exercise, has remained underexplored. Many studies on the physiological responses to hypoxia have either excluded women or included only a limited number without analyzing sex-related differences. To address this gap, this comprehensive review conducted an extensive literature search to examine changes in physiological functions related to oxygen transport and consumption in hypoxic conditions. The review encompasses various aspects, including ventilatory responses, cardiovascular adjustments, hematological alterations, muscle metabolism shifts, and autonomic function modifications. Furthermore, it delves into the influence of sex hormones, which evolve throughout life, encompassing considerations related to the menstrual cycle and menopause. Among these physiological functions, the ventilatory response to exercise emerges as one of the most sex-sensitive factors that may modify reactions to hypoxia. While no significant sex-based differences were observed in cardiac hemodynamic changes during hypoxia, there is evidence of greater vascular reactivity in women, particularly at rest or when combined with exercise. Consequently, a diffusive mechanism appears to be implicated in sex-related variations in responses to hypoxia. Despite well-established sex disparities in hematological parameters, both acute and chronic hematological responses to hypoxia do not seem to differ significantly between sexes. However, it is important to note that these responses are sensitive to fluctuations in sex hormones, and further investigation is needed to elucidate the impact of the menstrual cycle and menopause on physiological responses to hypoxia.
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Affiliation(s)
- Antoine Raberin
- Institute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Johannes Burtscher
- Institute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Tom Citherlet
- Institute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Giorgio Manferdelli
- Institute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Bastien Krumm
- Institute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Nicolas Bourdillon
- Institute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Juliana Antero
- Institut de Recherche Bio-Médicale Et d'Épidémiologie du Sport (EA 7329), French Institute of Sport, Paris, France
| | - Letizia Rasica
- Faculty of Kinesiology, University of Calgary, Calgary, Canada
| | - Davide Malatesta
- Institute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Franck Brocherie
- Laboratory Sport, Expertise and Performance (EA 7370), French Institute of Sport, Paris, France
| | - Martin Burtscher
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Grégoire P Millet
- Institute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland.
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Jardine DL. What lies beneath: cyclical giant bursts of SNA during vasovagal syncope. Clin Auton Res 2024; 34:213-217. [PMID: 38308177 DOI: 10.1007/s10286-023-01009-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Accepted: 12/09/2023] [Indexed: 02/04/2024]
Affiliation(s)
- D L Jardine
- Departments of Medicine and General Medicine, Christchurch Hospital, 2, Riccarton Ave, Christchurch, 4710, New Zealand.
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5
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Leach OK, Gifford JR, Mack GW. Rapid onset vasodilation during baroreceptor loading and unloading. Am J Physiol Regul Integr Comp Physiol 2023; 325:R568-R575. [PMID: 37694334 DOI: 10.1152/ajpregu.00116.2023] [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: 05/17/2023] [Revised: 08/21/2023] [Accepted: 09/05/2023] [Indexed: 09/12/2023]
Abstract
The purpose of these experiments was to determine if the increase in vascular conductance following a single muscle contraction (50% of maximal voluntary contraction) (6 male and 6 female subjects) was altered during baroceptor loading and unloading. Rapid onset vasodilation (ROV) was determined by measuring brachial artery blood flow (Doppler ultrasound) and blood pressure (Finapress monitor). Brachial artery vascular conductance was calculated by dividing blood flow by mean arterial pressure. ROV was described by the area under the Δvascular conductance (VC)-time curve during the 30 s following muscle contraction. ROV was determined using chamber pressures of +20, +10, 0, -10, -20, and -40 mmHg (lower body positive and negative pressure, LBPP, and LBNP). We tested the hypothesis that the impact of baroreceptor loading and unloading produces a proportion change in ROV. The level of ROV following each contraction was proportional to the peak force (r2 = 0.393, P = 0.0001). Peak force was therefore used as a covariate in further analysis. ROV during application of -40 mmHg LBNP (0.345 ± 0.229 mL·mmHg-1) was lower than that observed at Control (0.532 ± 0.284 mL·mmHg-1, P = 0.034) and +20 mmHg LBPP (0.658 ± 0.364 mL·mmHg-1, P = 0.0008). ROV was linearly related to chamber pressure from -40 to +20 mmHg chamber pressure (r2 = 0.512, P = 0.022, n = 69) and from -20 to +10 mmHg chamber pressure (r2= 0.973, P < 0.0425, n = 45), Overall, vasoconstrictor tone altered with physiologically relevant baroreceptor loading and unloading resulted in a proportion change in ROV.NEW & NOTEWORTHY Rapid onset vasodilation (ROV) was linearly related to the peak force of each single 1-s muscle contraction. In addition, ROV is reduced by baroreceptor unloading (LBNP: -10, -120, and -40 mmHg) and increased by baroreceptor loading (LBPP: +10 and +20 mmHg). Without accounting for peak force and the level of baroreceptor engagement makes comparison of ROV in subjects of differing muscle size or strength untenable.
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Affiliation(s)
- Olivia K Leach
- Department of Exercise Sciences, Brigham Young University, Provo, Utah, United States
| | - Jayson R Gifford
- Department of Exercise Sciences, Brigham Young University, Provo, Utah, United States
| | - Gary W Mack
- Department of Exercise Sciences, Brigham Young University, Provo, Utah, United States
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Nardone M, Katerberg C, Teixeira AL, Lee JB, Bommarito JC, Millar PJ. Sympathetic transduction of blood pressure during graded lower body negative pressure in young healthy adults. Am J Physiol Regul Integr Comp Physiol 2022; 322:R620-R628. [DOI: 10.1152/ajpregu.00034.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Sympathetic transduction of blood pressure (BP) is correlated negatively with resting muscle sympathetic nerve activity (MSNA) in cross-sectional data, but the acute effects of increasing MSNA are unclear. Sixteen (4 females) healthy adults (26±3 years) underwent continuous measurement of heart rate, BP, and MSNA at rest and during graded lower body negative pressure (LBNP) at -10, -20, and -30mmHg. Sympathetic transduction of BP was quantified in the time (signal averaging) and frequency (MSNA-BP gain) domains. The proportion of MSNA bursts firing within each tertile of BP were calculated. As expected, LBNP increased MSNA burst frequency (P<0.01) and burst amplitude (P<0.02), though the proportions of MSNA bursts firing across each BP tertile remained stable (all P>0.44). The MSNA-diastolic BP low frequency transfer function gain (P=0.25) was unchanged during LBNP; the spectral coherence was increased (P=0.03). Signal-averaged sympathetic transduction of diastolic BP was unchanged (from 2.1±1.0 at rest to 2.4±1.5, 2.2±1.3, and 2.3±1.4mmHg; P=0.43) during LBNP, but diastolic BP responses following non-burst cardiac cycles progressively decreased (from -0.8±0.4 at rest to -1.0±0.6, -1.2±0.6, and -1.6±0.9mmHg; P<0.01). As a result, the difference between MSNA burst and non-bursts diastolic BP responses was increased (from 2.9±1.4 at rest to 3.4±1.9, 3.4±1.9, and 3.9±2.1mmHg; P<0.01). In conclusion, acute increases in MSNA using LBNP did not alter traditional signal-averaged or frequency-domain measures of sympathetic transduction of BP or the proportion of MSNA bursts firing at different BP levels. The factors that determine changes in the firing of MSNA bursts relative to oscillations in BP require further investigation.
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Affiliation(s)
- Massimo Nardone
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Carlin Katerberg
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - André L. Teixeira
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Jordan B. Lee
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Julian C. Bommarito
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Philip J. Millar
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
- Toronto General Research Institute, Toronto General Hospital, Toronto, Ontario, Canada
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7
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Hockin BCD, Tang EZ, Lloyd MG, Claydon VE. Forearm vascular resistance responses to the Valsalva maneuver in healthy young and older adults. Clin Auton Res 2021; 31:737-753. [PMID: 34014418 DOI: 10.1007/s10286-021-00810-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 05/03/2021] [Indexed: 11/25/2022]
Abstract
PURPOSE Effective end-organ peripheral vascular resistance responses are critical to blood pressure control while upright, and prevention of syncope (fainting). The Valsalva maneuver (VM) induces blood pressure decreases that evoke baroreflex-mediated vasoconstriction. We characterized beat-to-beat forearm vascular resistance (FVR) responses to the VM in healthy adults, evaluated the impact of age and sex on these responses, and investigated their association with orthostatic tolerance (OT; susceptibility to syncope). We hypothesized that individuals with smaller FVR responses would be more susceptible to syncope. METHODS Healthy young (N = 36; 19 women; age 25.4 ± 4.6 years) and older (N = 21; 12 women; age 62.4 ± 9.6 years) adults performed a supine 40 mmHg, 20 s VM. Graded 60° head-up-tilt with combined lower body negative pressure continued to presyncope was used to determine OT. Non-invasive beat-to-beat blood pressure and heart rate (finger plethysmography) were recorded continuously. FVR was calculated as mean arterial pressure (MAP) divided by brachial blood flow velocity (Doppler ultrasound) relative to baseline. RESULTS The VM produces a distinctive FVR pattern that peaks (+137.1 ± 11.6%) in phase 2B (17.5 ± 0.3 s) as the baroreflex responds to low-pressure perturbations. This response increased with age overall (p < 0.001) and within male (p = 0.030) and female subgroups (p < 0.001). Maximum FVR during the VM was significantly correlated with maximal tilt FVR (r = 0.364; p = 0.0153) and with OT when expressed relative to the MAP decrease in phase 2A (Max FVR (%)/MAP2A-1; r = 0.337; p = 0.0206). CONCLUSION This is the first characterization of FVR responses to the VM. The VM elicits large baroreflex-mediated increases in FVR; small FVR responses to the VM may indicate susceptibility to syncope.
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Affiliation(s)
- Brooke C D Hockin
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada.,International Collaboration On Repair and Discoveries (ICORD), University of British Columbia, Vancouver, BC, Canada
| | - Eileen Z Tang
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada.,International Collaboration On Repair and Discoveries (ICORD), University of British Columbia, Vancouver, BC, Canada
| | - Matthew G Lloyd
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada.,International Collaboration On Repair and Discoveries (ICORD), University of British Columbia, Vancouver, BC, Canada
| | - Victoria E Claydon
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada. .,International Collaboration On Repair and Discoveries (ICORD), University of British Columbia, Vancouver, BC, Canada.
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Seeley AD, Giersch GEW, Charkoudian N. Post-exercise Body Cooling: Skin Blood Flow, Venous Pooling, and Orthostatic Intolerance. Front Sports Act Living 2021; 3:658410. [PMID: 34079934 PMCID: PMC8165173 DOI: 10.3389/fspor.2021.658410] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Accepted: 04/16/2021] [Indexed: 12/28/2022] Open
Abstract
Athletes and certain occupations (e.g., military, firefighters) must navigate unique heat challenges as they perform physical tasks during prolonged heat stress, at times while wearing protective clothing that hinders heat dissipation. Such environments and activities elicit physiological adjustments that prioritize thermoregulatory skin perfusion at the expense of arterial blood pressure and may result in decreases in cerebral blood flow. High levels of skin blood flow combined with an upright body position augment venous pooling and transcapillary fluid shifts in the lower extremities. Combined with sweat-driven reductions in plasma volume, these cardiovascular alterations result in levels of cardiac output that do not meet requirements for brain blood flow, which can lead to orthostatic intolerance and occasionally syncope. Skin surface cooling countermeasures appear to be a promising means of improving orthostatic tolerance via autonomic mechanisms. Increases in transduction of sympathetic activity into vascular resistance, and an increased baroreflex set-point have been shown to be induced by surface cooling implemented after passive heating and other arterial pressure challenges. Considering the further contribution of exercise thermogenesis to orthostatic intolerance risk, our goal in this review is to provide an overview of post-exercise cooling strategies as they are capable of improving autonomic control of the circulation to optimize orthostatic tolerance. We aim to synthesize both basic and applied physiology knowledge available regarding real-world application of cooling strategies to reduce the likelihood of experiencing symptomatic orthostatic intolerance after exercise in the heat.
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Affiliation(s)
- Afton D Seeley
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, MA, United States.,Oak Ridge Institute of Science and Education, Belcamp, MD, United States
| | - Gabrielle E W Giersch
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, MA, United States.,Oak Ridge Institute of Science and Education, Belcamp, MD, United States
| | - Nisha Charkoudian
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, MA, United States
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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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Zabriskie HA, Kerksick CM, Jagim AR. Active women demonstrate acute autonomic and hemodynamic shifts following exercise in heat and humidity: A pilot study. Temperature (Austin) 2021; 8:64-79. [PMID: 33553506 DOI: 10.1080/23328940.2020.1796242] [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: 10/23/2022] Open
Abstract
The purpose of this study was to assess autonomic and hemodynamic recovery in women who performed moderate-intensity exercise in heat. Seven women (31.7 ± 7.6 years, 67.5 ± 4.4 kg, 25.7 ± 5.6% Fat, 43.9 ± 5.1 mL/kg/min) completed two identical bouts of graded treadmill walking (~60% VO2peak). One bout was hot (37.5 ± 1.4°C, 46.5 ± 4.6% relative humidity (RH)), and the other was moderate (20.7 ± 1.1°C, 29.9 ± 4.1% RH). For 24 h before and one h after each bout, participants had heart rate variability monitored. After each exercise bout HR and BP were measured during 30 min of supine recovery and 10 min of orthostatic challenge. HF power and RMSSD were lower and LF power and LF:HF ratio greater following exercise in the heat and remained different from the moderate condition for 30 min (p < 0.05). During supine recovery, heat exposure led to higher HR (p = 0.002) and lower DBP (p = 0.016). SBP (p = 0.037) and DBP (p = 0.008) were both lower after 10 min of supine recovery following hot exercise than after moderate temperature. Average response did not reveal orthostatic hypotension despite heat causing a higher HR (p = 0.011) and lower SBP (p = 0.026) after 10 min of orthostatic exposure. Trained women exhibit an autonomic shift toward sympathetic dominance for at least 30 min after exercise in heat. Women who exercise in heat should be wary of an exacerbated HR response after exercise and low recovery blood pressures.
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Affiliation(s)
| | - Chad M Kerksick
- Exercise and Performance Nutrition Laboratory, Department of Exercise Science, Lindenwood University, St. Charles, MO, USA
| | - Andrew R Jagim
- Sports Medicine Research, Mayo Clinic Health Systems, Onalaska, WI, USA
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11
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Miller AJ, Cui J, Luck JC, Sinoway LI, Muller MD. Age and sex differences in sympathetic and hemodynamic responses to hypoxia and cold pressor test. Physiol Rep 2020; 7:e13988. [PMID: 30659773 PMCID: PMC6339536 DOI: 10.14814/phy2.13988] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Accepted: 12/13/2018] [Indexed: 11/24/2022] Open
Abstract
Emerging evidence suggests that sympathetic vasoconstriction is lower in young women. We hypothesized that increases in muscle sympathetic nerve activity (MSNA) during acute physiological stressors induce less vasoconstriction in young women compared to young men. Healthy young men (n = 10, 27 ± 1 years), young women (n = 12, 25 ± 1 years), and older women (n = 10, 63 ± 6 years) performed the cold pressor test (hand in ice for 2 min) and continuous hypoxia (10% O2 , 90% N2 ) for 5 min. MSNA, femoral blood flow velocity, heart rate, and blood pressure were acquired continuously. Femoral artery diameter was obtained every minute and used to calculate femoral blood flow, and femoral vascular resistance and conductance. MSNA responses to cold pressor test (P = 0.345) and hypoxia (P = 0.969) were not different between groups. Young women had greater femoral blood flow (P = 0.002) and vascular conductance (P = 0.041) responses to cold pressor test compared with young men. The femoral blood flow response to hypoxia was not different between the two sexes but the increase in femoral flow was attenuated in older women compared with younger women (P = 0.036). These data show that young women had paradoxical vasodilation to cold pressor test. The mechanisms responsible for the attenuated sympathetic vasoconstriction or for enhanced vasodilation in young women during the CPT require further investigation.
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Affiliation(s)
- Amanda J Miller
- Penn State Heart and Vascular Institute, Penn State University College of Medicine, Hershey, Pennsylvania
| | - Jian Cui
- Penn State Heart and Vascular Institute, Penn State University College of Medicine, Hershey, Pennsylvania
| | - J Carter Luck
- Penn State Heart and Vascular Institute, Penn State University College of Medicine, Hershey, Pennsylvania
| | - Lawrence I Sinoway
- Penn State Heart and Vascular Institute, Penn State University College of Medicine, Hershey, Pennsylvania
| | - Matthew D Muller
- Penn State Heart and Vascular Institute, Penn State University College of Medicine, Hershey, Pennsylvania
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12
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Shimizu K, Shiozawa K, Ishida K, Saito M, Mizuno S, Akima H, Katayama K. Blood pressure and limb blood flow responses during hyperpnoea are not affected by menstrual cycle phase in young women. Respir Physiol Neurobiol 2020; 275:103387. [PMID: 31945516 DOI: 10.1016/j.resp.2020.103387] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 01/11/2020] [Accepted: 01/11/2020] [Indexed: 12/18/2022]
Abstract
The purpose of this study was to clarify whether the menstrual cycle affects the cardiovascular and limb blood flow responses during hyperpnoea. Fifteen young female subjects participated. An incremental respiratory endurance test was performed at the early follicular (EF) and midluteal (ML) phases. Target minute ventilation was initially set at 30 % of maximal voluntary ventilation (MVV12) and was increased by 10 %MVV12 every 3 min. The test was terminated when the subjects no longer maintained the target ventilation. Mean arterial blood pressure (MBP) and mean blood flow in the brachial artery were continuously measured. There were no significant differences in the increase in MBP (EF: +13.0 ± 7.9 mmHg vs. ML: + 15.4 ± 12.9 mmHg during the test, F = 0.70, P = 0.59) and the decrease in brachial blood flow between the phases. These results suggest that menstrual cycle does not affect respiratory muscle-induced metaboreflex in young women.
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Affiliation(s)
- Kaori Shimizu
- Graduate School of Education and Human Development, Nagoya University, Nagoya, Japan
| | - Kana Shiozawa
- Graduate School of Medicine, Nagoya University, Nagoya, Japan
| | - Koji Ishida
- Graduate School of Medicine, Nagoya University, Nagoya, Japan; Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan
| | - Mitsuru Saito
- Applied Physiology Laboratory, Toyota Technological Institute, Nagoya, Japan
| | - Sahiro Mizuno
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan; Research Fellow of Japan Society for the Promotion of Science, Japan
| | - Hiroshi Akima
- Graduate School of Education and Human Development, Nagoya University, Nagoya, Japan; Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan
| | - Keisho Katayama
- Graduate School of Medicine, Nagoya University, Nagoya, Japan; Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan.
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13
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Cvirn G, Waha JE, Brix B, Rössler A, Jantscher A, Schlagenhauf A, Koestenberger M, Wonisch W, Wagner T, Goswami N. Coagulation changes induced by lower-body negative pressure in men and women. J Appl Physiol (1985) 2019; 126:1214-1222. [DOI: 10.1152/japplphysiol.00940.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
We investigated whether lower-body negative pressure (LBNP) application leads to coagulation activation in whole blood (WB) samples in healthy men and women. Twenty-four women and 21 men, all healthy young participants, with no histories of thrombotic disorders and not on medications, were included. LBNP was commenced at −10 mmHg and increased by −10 mmHg every 5 min until a maximum of −40 mmHg. Recovery up to 10 min was also monitored. Blood samples were collected at baseline, at end of LBNP, and end of recovery. Hemostatic profiling included comparing the effects of LBNP on coagulation values in both men and women using standard coagulation tests, calibrated automated thrombogram, thrombelastometry, impedance aggregometry, and markers of thrombin formation. LBNP led to coagulation activation determined in both plasma and WB samples. At baseline, women were hypercoagulable compared with men, as evidenced by their shorter “lag times” and higher thrombin peaks and by shorter “coagulation times” and “clot formation times.” Moreover, men were more susceptible to LBNP, as reflected in their elevated factor VIII levels and decreased lag times following LBNP. LBNP-induced coagulation activation was not accompanied by endothelial activation. Women appear to be relatively hypercoagulable compared with men, but men are more susceptible to coagulation changes during LBNP. The application of LBNP might be a useful future tool to identify individuals with an elevated risk for thrombosis, in subjects with or without history of thrombosis.NEW & NOTEWORTHY LBNP led to coagulation activation determined in both plasma and whole blood samples. At baseline, women were hypercoagulable compared with men. Men were, however, more susceptible to coagulation changes during LBNP. LBNP-induced coagulation activation was not accompanied by endothelial activation. The application of LBNP might be a useful future tool to identify individuals with an elevated risk for thrombosis, in subjects with or without history of thrombosis.
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Affiliation(s)
- Gerhard Cvirn
- Physiological Chemistry Division, Otto Loewi Research Center, Medical University of Graz, Graz, Austria
| | - James E. Waha
- Physiology Division, Otto Loewi Research Center, Medical University of Graz, Graz, Austria
| | - Bianca Brix
- Physiology Division, Otto Loewi Research Center, Medical University of Graz, Graz, Austria
| | - Andreas Rössler
- Physiology Division, Otto Loewi Research Center, Medical University of Graz, Graz, Austria
| | - Andreas Jantscher
- Physiology Division, Otto Loewi Research Center, Medical University of Graz, Graz, Austria
| | - Axel Schlagenhauf
- Department of Pediatric Cardiology, Medical University of Graz, Graz, Austria
| | | | - Willibald Wonisch
- Physiological Chemistry Division, Otto Loewi Research Center, Medical University of Graz, Graz, Austria
| | - Thomas Wagner
- Department of Blood Group Serology and Transfusion Medicine, Medical University of Graz, Graz, Austria
| | - Nandu Goswami
- Physiology Division, Otto Loewi Research Center, Medical University of Graz, Graz, Austria
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14
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Opatz O, Nordine M, Habazettl H, Ganse B, Petricek J, Dosel P, Stahn A, Steinach M, Gunga HC, Maggioni MA. Limb Skin Temperature as a Tool to Predict Orthostatic Instability. Front Physiol 2018; 9:1241. [PMID: 30233412 PMCID: PMC6134950 DOI: 10.3389/fphys.2018.01241] [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: 02/23/2018] [Accepted: 08/16/2018] [Indexed: 11/20/2022] Open
Abstract
Orthostatic instability is one of the main consequences of weightlessness or gravity challenge and plays as well a crucial role in public health, being one of the most frequent disease of aging. Therefore, the assessment of effective countermeasures, or even the possibility to predict, and thus prevent orthostatic instability is of great importance. Heat stress affects orthostatic stability and may lead to impaired consciousness and decrease in cerebral perfusion, specifically during the exposure to G-forces. Conversely, peripheral cooling can prevent orthostatic intolerance – even in normothermic healthy subjects. Indicators of peripheral vasodilation, as elevated skin surface temperatures, may mirror blood decentralization and an increased risk of orthostatic instability. Therefore, the aim of this study was to quantify orthostatic instability risk, by assessing in 20 fighter jet pilot candidates’ cutaneous limb temperatures, with respect to the occurrence of G-force-induced almost loss of consciousness (ALOC), before and during exposure to a push-pull maneuver, i.e., head-down tilt, combined with lower body negative pressure. Peripheral skin temperatures from the upper and lower (both proximal and distal) extremities and core body temperature via heat-flux approach (i.e., the Double Sensor), were continuously measured before and during the maneuver. The 55% of subjects that suffered an ALOC during the procedure had higher upper arm and thigh temperatures at baseline compared to the 45% that remained stable. No difference in baseline core body temperature and distal limbs (both upper and lower) skin temperatures were found between the two groups. Therefore, peripheral skin temperature data could be considered a predicting factor for ALOC, prior to rapid onset acceleration. Moreover, these findings could also find applications in patient care settings such as in intensive care units.
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Affiliation(s)
- Oliver Opatz
- Charité - Universitätsmedizin Berlin, Institute of Physiology, Center for Space Medicine and Extreme Environments Berlin, Berlin, Germany
| | - Michael Nordine
- Charité - Universitätsmedizin Berlin, Institute of Physiology, Center for Space Medicine and Extreme Environments Berlin, Berlin, Germany
| | - Helmut Habazettl
- Charité - Universitätsmedizin Berlin, Institute of Physiology, Center for Space Medicine and Extreme Environments Berlin, Berlin, Germany
| | - Bergita Ganse
- German Aerospace Center (DLR- Deutsches Zentrum für Luft- und Raumfahrt), Institute of Aerospace Medicine (Institut für Luft- und Raumfahrtmedizin), Cologne, Germany
| | - Jan Petricek
- Institute of Aviation Medicine, Military University Hospital Prague, Prague, Czechia
| | - Petr Dosel
- Institute of Aviation Medicine, Military University Hospital Prague, Prague, Czechia
| | - Alexander Stahn
- Charité - Universitätsmedizin Berlin, Institute of Physiology, Center for Space Medicine and Extreme Environments Berlin, Berlin, Germany.,Division of Sleep and Chronobiology, Department of Psychiatry, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States
| | - Mathias Steinach
- Charité - Universitätsmedizin Berlin, Institute of Physiology, Center for Space Medicine and Extreme Environments Berlin, Berlin, Germany
| | - Hanns-Christian Gunga
- Charité - Universitätsmedizin Berlin, Institute of Physiology, Center for Space Medicine and Extreme Environments Berlin, Berlin, Germany
| | - Martina A Maggioni
- Charité - Universitätsmedizin Berlin, Institute of Physiology, Center for Space Medicine and Extreme Environments Berlin, Berlin, Germany.,Department of Biomedical Sciences for Health, Università degli Studi di Milano, Milan, Italy
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15
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Masatli Z, Nordine M, Maggioni MA, Mendt S, Hilmer B, Brauns K, Werner A, Schwarz A, Habazettl H, Gunga HC, Opatz OS. Gender-Specific Cardiovascular Reactions to +Gz Interval Training on a Short Arm Human Centrifuge. Front Physiol 2018; 9:1028. [PMID: 30108517 PMCID: PMC6079353 DOI: 10.3389/fphys.2018.01028] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Accepted: 07/11/2018] [Indexed: 11/13/2022] Open
Abstract
Cardiovascular deconditioning occurs in astronauts during microgravity exposure, and may lead to post-flight orthostatic intolerance, which is more prevalent in women than men. Intermittent artificial gravity is a potential countermeasure, which can effectively train the cardiovascular mechanisms responsible for maintaining orthostatic integrity. Since cardiovascular responses may differ between women and men during gravitational challenges, information regarding gender specific responses during intermittent artificial gravity exposure plays a crucial role in countermeasure strategies. This study implemented a +Gz interval training protocol using a ground based short arm human centrifuge, in order to assess its effectiveness in stimulating the components of orthostatic integrity, such as diastolic blood pressure, heart rate and vascular resistance amongst both genders. Twenty-eight participants (12 men/16 women) underwent a two-round graded +1/2/1 Gz profile, with each +Gz phase lasting 4 min. Cardiovascular parameters from each phase (averaged last 60 sec) were analyzed for significant changes with respect to baseline values. Twelve men and eleven women completed the session without interruption, while five women experienced an orthostatic event. These women had a significantly greater height and baseline mean arterial pressure than their counterparts. Throughout the +Gz interval session, women who completed the session exhibited significant increases in heart rate and systemic vascular resistance index throughout all +Gz phases, while exhibiting increases in diastolic blood pressure during several +Gz phases. Men expressed significant increases from baseline in diastolic blood pressure throughout the session with heart rate increases during the +2Gz phases, while no significant changes in vascular resistance were recorded. Furthermore, women exhibited non-significantly higher heart rates over men during all phases of +Gz. Based on these findings, this protocol proved to consistently stimulate the cardiovascular systems involved in orthostatic integrity to a larger extent amongst women than men. Thus the +Gz gradients used for this interval protocol may be beneficial for women as a countermeasure against microgravity induced cardiovascular deconditioning, whereas men may require higher +Gz gradients. Lastly, this study indicates that gender specific cardiovascular reactions are apparent during graded +Gz exposure while no significant differences regarding cardiovascular responses were found between women and men during intermittent artificial gravity training.
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Affiliation(s)
- Zeynep Masatli
- Center for Space Medicine and Extreme Environments Berlin, Institute of Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Michael Nordine
- Center for Space Medicine and Extreme Environments Berlin, Institute of Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Martina A Maggioni
- Center for Space Medicine and Extreme Environments Berlin, Institute of Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany.,Department of Biomedical Sciences for Health, Università degli Studi di Milano, Milan, Italy
| | - Stefan Mendt
- Center for Space Medicine and Extreme Environments Berlin, Institute of Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Ben Hilmer
- Center for Space Medicine and Extreme Environments Berlin, Institute of Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Katharina Brauns
- Center for Space Medicine and Extreme Environments Berlin, Institute of Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Anika Werner
- Center for Space Medicine and Extreme Environments Berlin, Institute of Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Anton Schwarz
- Central Medical School, Monash University, Melbourne, VIC, Australia
| | - Helmut Habazettl
- Center for Space Medicine and Extreme Environments Berlin, Institute of Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Hanns-Christian Gunga
- Center for Space Medicine and Extreme Environments Berlin, Institute of Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Oliver S Opatz
- Center for Space Medicine and Extreme Environments Berlin, Institute of Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
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16
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Evans JM, Knapp CF, Goswami N. Artificial Gravity as a Countermeasure to the Cardiovascular Deconditioning of Spaceflight: Gender Perspectives. Front Physiol 2018; 9:716. [PMID: 30034341 PMCID: PMC6043777 DOI: 10.3389/fphys.2018.00716] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 05/24/2018] [Indexed: 12/11/2022] Open
Abstract
Space flight-induced physiological deconditioning resulting from decreased gravitational input, decreased plasma volume, and disruption of regulatory mechanisms is a significant problem in returning astronauts as well as in normal aging. Here we review effects of a promising countermeasure on cardiovascular systems of healthy men and women undergoing Earth-based models of space-flight. This countermeasure is produced by a centrifuge and called artificial gravity (AG). Numerous studies have determined that AG improves orthostatic tolerance (as assessed by various protocols) of healthy ambulatory men, of men deconditioned by bed rest or by immersion (both wet and dry) and, in one case, following spaceflight. Although a few studies of healthy, ambulatory women and one study of women deconditioned by furosemide, have reported improvement of orthostatic tolerance following exposure to AG, studies of bed-rested women exposed to AG have not been conducted. However, in ambulatory, normovolemic subjects, AG training was more effective in men than women and more effective in subjects who exercised during AG than in those who passively rode the centrifuge. Acute exposure to an AG protocol, individualized to provide a common stimulus to each person, also improved orthostatic tolerance of normovolemic men and women and of furosemide-deconditioned men and women. Again, men's tolerance was more improved than women's. In both men and women, exposure to AG increased stroke volume, so greater improvement in men vs. women was due in part to their different vascular responses to AG. Following AG exposure, resting blood pressure (via decreased vascular resistance) decreased in men but not women, indicating an increase in men's vascular reserve. Finally, in addition to counteracting space flight deconditioning, improved orthostatic tolerance through AG-induced improvement of stroke volume could benefit aging men and women on Earth.
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Affiliation(s)
- Joyce M. Evans
- Department of Biomedical Engineering, University of Kentucky, Lexington, KY, United States
| | - Charles F. Knapp
- Department of Biomedical Engineering, University of Kentucky, Lexington, KY, United States
| | - Nandu Goswami
- Physiology, Otto Loewi Research Center for Vascular Biology, Immunology and Inflammation, Medical University of Graz, Graz, Austria
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17
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Katayama K, Smith JR, Goto K, Shimizu K, Saito M, Ishida K, Koike T, Iwase S, Harms CA. Elevated sympathetic vasomotor outflow in response to increased inspiratory muscle activity during exercise is less in young women compared with men. Exp Physiol 2018; 103:570-580. [DOI: 10.1113/ep086817] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2017] [Accepted: 01/11/2018] [Indexed: 01/01/2023]
Affiliation(s)
- Keisho Katayama
- Research Center of Health, Physical Fitness and Sports; Nagoya University; Nagoya Japan
- Graduate School of Medicine; Nagoya University; Nagoya Japan
| | - Joshua R. Smith
- Department of Cardiovascular Diseases; Mayo Clinic; Rochester MN USA
| | - Kanako Goto
- Graduate School of Medicine; Nagoya University; Nagoya Japan
| | - Kaori Shimizu
- Graduate School of Education and Human Development; Nagoya University; Nagoya Japan
| | - Mitsuru Saito
- Applied Physiology Laboratory; Toyota Technological Institute; Nagoya Japan
| | - Koji Ishida
- Research Center of Health, Physical Fitness and Sports; Nagoya University; Nagoya Japan
- Graduate School of Medicine; Nagoya University; Nagoya Japan
| | - Teruhiko Koike
- Research Center of Health, Physical Fitness and Sports; Nagoya University; Nagoya Japan
- Graduate School of Medicine; Nagoya University; Nagoya Japan
| | - Satoshi Iwase
- Department of Physiology, School of Medicine; Aichi Medical University; Nagakute Japan
| | - Craig A. Harms
- Department of Kinesiology; Kansas State University; Manhattan KS USA
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18
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19
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Siamwala JH, Macias BR, Lee PC, Hargens AR. Gender differences in tibial microvascular flow responses to head down tilt and lower body negative pressure. Physiol Rep 2017; 5:5/4/e13143. [PMID: 28242824 PMCID: PMC5328775 DOI: 10.14814/phy2.13143] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 01/05/2017] [Accepted: 01/08/2017] [Indexed: 11/24/2022] Open
Abstract
The purpose of the investigation was to study lower body negative pressure recovery in response to head down tilt position in men and women. The study examined the primary hypothesis that tibial bone microvascular flow responses to HDT and lower body negative pressure (LBNP) differ in women and men. Nine women and nine men between 20 to 30 years of age participated in the study. Tibial microvascular flow, head and tibial oxygenation and calf circumference were measured using photoplethysmography (PPG), near‐infrared spectroscopy (NIRS) and strain gauge plethysmography (SGP), respectively, during sitting (control baseline), supine, 15° HDT, and 15° HDT with 25 mmHg LBNP. Tibial microvascular flow with HDT increased by 57% from supine position (from 1.4V ± 0.7 to 2.2V ± 1.0 HDT; ANOVA P < 0.05) in men but there is no significant difference between supine and HDT in women. Ten minutes of LBNP during 15oHDT restored tibial bone microvascular flows to supine levels, (from 2.2V±1.0 HDT to 1.1V ± 0.7 supine; ANOVA P < 0.05) in men but not in women. These data support the concept that there are gender specific microvascular responses to a fluid‐shift countermeasure such as LBNP. Thus, gender differences should be considered while developing future countermeasure strategies to headward fluid shifts in microgravity.
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Affiliation(s)
- Jamila H Siamwala
- Department of Orthopedic Surgery, University of California, San Diego, California
| | - Brandon R Macias
- Department of Orthopedic Surgery, University of California, San Diego, California
| | - Paul C Lee
- Department of Orthopedic Surgery, University of California, San Diego, California
| | - Alan R Hargens
- Department of Orthopedic Surgery, University of California, San Diego, California
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20
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Usselman CW, Nielson CA, Luchyshyn TA, Gimon TI, Coverdale NS, Van Uum SHM, Shoemaker JK. Hormone phase influences sympathetic responses to high levels of lower body negative pressure in young healthy women. Am J Physiol Regul Integr Comp Physiol 2016; 311:R957-R963. [PMID: 27733385 DOI: 10.1152/ajpregu.00190.2016] [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: 05/09/2016] [Revised: 09/28/2016] [Accepted: 10/11/2016] [Indexed: 01/03/2023]
Abstract
We tested the hypothesis that sympathetic responses to baroreceptor unloading may be affected by circulating sex hormones. During lower body negative pressure at -30, -60, and -80 mmHg, muscle sympathetic nerve activity (MSNA), heart rate, and blood pressure were recorded in women who were taking (n = 8) or not taking (n = 9) hormonal contraceptives. All women were tested twice, once during the low-hormone phase (i.e., the early follicular phase of the menstrual cycle and the placebo phase of hormonal contraceptive use), and again during the high-hormone phase (i.e., the midluteal phase of the menstrual cycle and active phase of contraceptive use). During baroreceptor unloading, the reductions in stroke volume and resultant increases in MSNA and total peripheral resistance were greater in high-hormone than low-hormone phases in both groups. When normalized to the fall in stroke volume, increases in MSNA were no longer different between hormone phases. While stroke volume and sympathetic responses were similar between women taking and not taking hormonal contraceptives, mean arterial pressure was maintained during baroreceptor unloading in women not taking hormonal contraceptives but not in women using hormonal contraceptives. These data suggest that differences in sympathetic activation between hormone phases, as elicited by lower body negative pressure, are the result of hormonally mediated changes in the hemodynamic consequences of negative pressure, rather than centrally driven alterations to sympathetic regulation.
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Affiliation(s)
- Charlotte W Usselman
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada
| | - Chantelle A Nielson
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada
| | - Torri A Luchyshyn
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada
| | - Tamara I Gimon
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada
| | - Nicole S Coverdale
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada
| | - Stan H M Van Uum
- Department of Medicine, Western University, London, Ontario, Canada.,Lawson Health Research Institute, Western University, London, Ontario, Canada; and
| | - J Kevin Shoemaker
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada; .,Department of Physiology and Pharmacology, Western University, London, Ontario, Canada
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21
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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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22
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Carter JR, Cooke WH. Sympathetic nerve activity and blood pressure: who leads, who follows and why sex matters. J Physiol 2016; 594:4705-6. [PMID: 27581565 DOI: 10.1113/jp272569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Jason R Carter
- Department of Kinesiology and Integrative Physiology, Michigan Technological University, Houghton, MI, 49931, USA.
| | - William H Cooke
- Department of Kinesiology, Health, and Nutrition, University of Texas at San Antonio, San Antonio, TX, USA
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23
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Evans JM, Ribeiro LC, Moore FB, Wang S, Zhang Q, Kostas V, Ferguson CR, Serrador J, Falvo M, Stenger MB, Goswami N, Rask JC, Smith JD, Knapp CF. Hypovolemic men and women regulate blood pressure differently following exposure to artificial gravity. Eur J Appl Physiol 2015; 115:2631-40. [PMID: 26438067 DOI: 10.1007/s00421-015-3261-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 09/06/2015] [Indexed: 11/29/2022]
Abstract
PURPOSE In addition to serious bone, vestibular, and muscle deterioration, space flight leads to cardiovascular dysfunction upon return to gravity. In seeking a countermeasure to space flight-induced orthostatic intolerance, we previously determined that exposure to artificial gravity (AG) training in a centrifuge improved orthostatic tolerance of ambulatory subjects. This protocol was more effective in men than women and more effective when subjects exercised. METHODS We now determine the orthostatic tolerance limit (OTL) of cardiovascularly deconditioned (furosemide) men and women on one day following 90 min of AG compared to a control day (90 min of head-down bed rest, HDBR). RESULTS There were three major findings: a short bout of artificial gravity improved orthostatic tolerance of hypovolemic men (30 %) and women (22 %). Men and women demonstrated different mechanisms of cardiovascular regulation on AG and HDBR days; women maintained systolic blood pressure the same after HDBR and AG exposure while men's systolic pressure dropped (11 ± 2.9 mmHg) after AG. Third, as presyncopal symptoms developed, men's and women's cardiac output and stroke volume dropped to the same level on both days, even though the OTL test lasted significantly longer on the AG day, indicating cardiac filling as a likely variable to trigger presyncope. CONCLUSIONS (1) Even with gender differences, AG should be considered as a space flight countermeasure to be applied to astronauts before reentry into gravity, (2) men and women regulate blood pressure during an orthostatic stress differently following exposure to artificial gravity and (3) the trigger for presyncope may be cardiac filling.
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Affiliation(s)
- Joyce M Evans
- Department of Biomedical Engineering, University of Kentucky, 514G, Robotics and Manufacturing Building, 143 Graham Avenue, Lexington, KY, 40506, USA.
| | | | | | - Siqi Wang
- Department of Biomedical Engineering, University of Kentucky, 514G, Robotics and Manufacturing Building, 143 Graham Avenue, Lexington, KY, 40506, USA
| | - Qingguang Zhang
- Department of Biomedical Engineering, University of Kentucky, 514G, Robotics and Manufacturing Building, 143 Graham Avenue, Lexington, KY, 40506, USA
| | - Vladimir Kostas
- Department of Biomedical Engineering, University of Kentucky, 514G, Robotics and Manufacturing Building, 143 Graham Avenue, Lexington, KY, 40506, USA
| | - Connor R Ferguson
- Department of Biomedical Engineering, University of Kentucky, 514G, Robotics and Manufacturing Building, 143 Graham Avenue, Lexington, KY, 40506, USA
| | - Jorge Serrador
- Veterans Affairs New Jersey Health Care System, East Orange, NJ, USA
| | - Michael Falvo
- Veterans Affairs New Jersey Health Care System, East Orange, NJ, USA
| | | | | | - Jon C Rask
- NASA Ames Research Center, Moffett Field, CA, USA
| | | | - Charles F Knapp
- Department of Biomedical Engineering, University of Kentucky, 514G, Robotics and Manufacturing Building, 143 Graham Avenue, Lexington, KY, 40506, USA
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Carter R, Hinojosa-Laborde C, Convertino VA. Sex comparisons in muscle sympathetic nerve activity and arterial pressure oscillations during progressive central hypovolemia. Physiol Rep 2015; 3:3/6/e12420. [PMID: 26109186 PMCID: PMC4510624 DOI: 10.14814/phy2.12420] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Increased tolerance to central hypovolemia is generally associated with greater sympathoexcitation, high-frequency oscillatory patterns of mean arterial pressure (MAP), and tachycardia. On average, women are less tolerant to central hypovolemia than men; however, the autonomic mechanisms governing these comparisons are not fully understood. We tested the hypothesis that women with relatively high tolerance (HT) to central hypovolemia would display similar physiological reserve capacity for sympathoexcitation and oscillations in MAP at presyncope compared to HT men. About 10 men and five women were exposed to progressive lower body negative pressure (LBNP) until the presence of presyncopal symptoms. Based on our previous classification system, all subjects were classified as HT because they completed at least −60 mmHg LBNP. Muscle sympathetic serve activity (MSNA) was measured directly from the peroneal nerve via microneurography and arterial pressure (AP) was measured at the finger by photoplethysmography. LBNP time to presyncope was less (P < 0.01) in women (1727 ± 70 sec) than in men (2022 ± 201 sec). At presyncope, average MSNA in men (50 ± 12 bursts/min) and women (51 ± 7 bursts/min) was similar (P = 0.87). Coincident with similar stroke volume (SV) at presyncope, women had similar MAP and heart rates. However, women had less physiological reserve capacity for SV, AP-MSNA coherence, and oscillations in the high-frequency (HF) components of arterial pressure compared to men. Contrary to our hypothesis, lower tolerance to central hypovolemia in women was not associated with sympathoexcitation, but can be explained, in part by lower physiological reserve to elicit oscillatory patterns in AP, maintenance of AP-MSNA coherence and SV when compared to men.
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Affiliation(s)
- Robert Carter
- US Army Institute of Surgical Research JBSA Fort Sam Houston, Houston, Texas
| | | | - Victor A Convertino
- US Army Institute of Surgical Research JBSA Fort Sam Houston, Houston, Texas
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Sex differences in heart rate variability: a longitudinal study in international elite cross-country skiers. Eur J Appl Physiol 2015; 115:2107-14. [PMID: 26002403 DOI: 10.1007/s00421-015-3190-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Accepted: 05/09/2015] [Indexed: 10/23/2022]
Abstract
PURPOSE Exercise-related sudden cardiac deaths (SCD) occur with a striking male predominance. A higher sympathetic tone in men has been suggested as risk factor for SCD. Elite athletes have the highest risk for exercise-related SCD. We aimed to analyze the autonomic nervous system of elite cross-country skiers from Norway, Russia and Switzerland in supine position and after orthostatic challenge in various training periods (TP). METHOD Measurements of heart rate variability (HRV) were performed on a weekly basis over 1 year using an orthostatic challenge test with controlled breathing. Main outcome parameters were the high-frequency power in supine position (HFsupine) as marker of cardiac parasympathetic activity and the low-frequency/high-frequency power ratio after orthostatic challenge (LF/HFstand) as marker of cardiac sympathetic activation. Training intensity and duration were recorded daily and expressed as training strain. The training year was divided into three TPs. An average of weekly HRV measurements was calculated for each TP. RESULT Female (n = 19, VO2max 62.0 ± 4.6 ml kg(-1) min(-1), age 25.8 ± 4.3 years) and male (n = 16, VO2max 74.3 ± 6.3 ml kg(-1) min(-1), age 24.4 ± 4.2 years) athletes were included. Training strain was comparable between sexes (all p > 0.05) and changed between TPs (all p < 0.05) while no HRV parameters changed over time. There were no sex differences in HFsupine while the LF/HFstand was significantly higher in male athletes in all TPs. CONCLUSION For a comparable amount of training, male athletes showed constantly higher markers of sympathetic activity after a provocation maneuver. This may explain part of the male predominance in sports-related SCD.
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26
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Stickford ASL, VanGundy TB, Levine BD, Fu Q. Menstrual cycle phase does not affect sympathetic neural activity in women with postural orthostatic tachycardia syndrome. J Physiol 2015; 593:2131-43. [PMID: 25656420 DOI: 10.1113/jp270088] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Accepted: 01/20/2015] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Women with the postural orthostatic tachycardia syndrome (POTS) report fluctuations in orthostatic tolerance throughout the menstrual cycle. The mechanism(s) underlying blood pressure control across the menstrual cycle in women with POTS are unknown. The findings of the present study indicate that the menstrual cycle does not affect muscle sympathetic nerve activity but modulates blood pressure and vasoconstriction in POTS women during orthostatic stress. Factors other than sympathetic neural activity are likely responsible for the symptoms of orthostatic intolerance across the menstrual cycle in women with POTS. ABSTRACT Patients with the postural orthostatic tachycardia syndrome (POTS) are primarily premenopausal women, which may be attributed to female sex hormones. We tested the hypothesis that hormonal fluctuations of the menstrual cycle alter sympathetic neural activity and orthostatic tolerance in POTS women. Ten POTS women were studied during the early follicular (EF) and mid-luteal (ML) phases of the menstrual cycle. Haemodynamics and muscle sympathetic nerve activity (MSNA) were measured when supine, during 60 deg upright tilt for 45 min or until presyncope, and during the cold pressor test (CPT) and Valsalva manoeuvres. Blood pressure and total peripheral resistance were higher during rest and tilting in the ML than EF phase; however, heart rate, stroke volume and cardiac output were similar between phases. There were no mean ± SD differences in MSNA burst frequency (8 ± 8 EF phase vs. 10 ± 10 bursts min(-1) ML phase at rest; 34 ± 15 EF phase vs. 36 ± 16 bursts min(-1) ML phase at 5 min tilt), burst incidence or total activity, nor any differences in the cardiovagal and sympathetic baroreflex sensitivities between phases under any condition. The incidence of presyncope was also the same between phases. There were no differences in haemodynamic or sympathetic responses to CPT or Valsalva. These results suggest that the menstrual cycle does not affect sympathetic neural activity but modulates blood pressure and vasoconstriction in POTS women during tilting. Thus, factors other than sympathetic neural activity are probably responsible for the symptoms of orthostatic intolerance across the menstrual cycle in women with POTS.
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Affiliation(s)
- Abigail S L Stickford
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX, USA; University of Texas Southwestern Medical Center, Dallas, TX, USA
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Reulecke S, Charleston-Villalobos S, Voss A, González-Camarena R, Gaitán-González MJ, González-Hermosillo J, Hernández-Pacheco G, Aljama-Corrales T. Gender differences in cardiovascular and cardiorespiratory coupling in healthy subjects during head-up tilt test by Joint Symbolic Dynamics. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2015; 2014:3402-5. [PMID: 25570721 DOI: 10.1109/embc.2014.6944353] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Gender related-differences in the autonomic regulation of the cardiovascular and cardiorespiratory systems have been studied mainly by hemodynamic responses during different physical stressors. In this study, the influence of gender on the autonomic response to an orthostatic challenge was investigated by obtaining the cardiovascular and cardiorespiratory coupling using the nonlinear technique known as joint symbolic dynamics (JSD) representation. This study includes 24 healthy young subjects. Males (N=12) and age-matched females (N=12) were enrolled in a head-up tilt (HUT) test, breathing normally, including 5 minutes of supine position (baseline) and 25-40 minutes of 70° orthostatic phase. The cardiovascular and cardiorespiratory couplings were obtained at baseline, early and middle orthostatic phases. Although in baseline there were some gender differences, parameters from JSD showed highly significant (p=0.0004) differences in specific cardiovascular coupling patterns in the early tilt phase. Furthermore, JSD analysis revealed that in males, due to increased sympathetic activity, exist a lower degree of cardiovascular coupling accompanied with an increased occurrence of tachycardic patterns. On the other hand, the cardiorespiratory coupling revealed only very few slightly significant differences in all three phases.
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Joyner MJ, Barnes JN, Hart EC, Wallin BG, Charkoudian N. Neural control of the circulation: how sex and age differences interact in humans. Compr Physiol 2015; 5:193-215. [PMID: 25589269 PMCID: PMC4459710 DOI: 10.1002/cphy.c140005] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The autonomic nervous system is a key regulator of the cardiovascular system. In this review, we focus on how sex and aging influence autonomic regulation of blood pressure in humans in an effort to understand general issues related to the cardiovascular system as a whole. Younger women generally have lower blood pressure and sympathetic activity than younger men. However, both sexes show marked interindividual variability across age groups with significant overlap seen. Additionally, while men across the lifespan show a clear relationship between markers of whole body sympathetic activity and vascular resistance, such a relationship is not seen in young women. In this context, the ability of the sympathetic nerves to evoke vasoconstriction is lower in young women likely as a result of concurrent β2-mediated vasodilation that offsets α-adrenergic vasoconstriction. These differences reflect both central sympatho-inhibitory effects of estrogen and also its influence on peripheral vasodilation at the level of the vascular smooth muscle and endothelium. By contrast postmenopausal women show a clear relationship between markers of whole body sympathetic traffic and vascular resistance, and sympathetic activity rises progressively in both sexes with aging. These major findings in humans are discussed in the context of differences in population-based trends in blood pressure and orthostatic intolerance. The many areas where there is little sex-specific data on how the autonomic nervous system participates in the regulation of the human cardiovascular system are highlighted.
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Affiliation(s)
| | - Jill N. Barnes
- Department of Anesthesiology, Mayo Clinic, Rochester, MN
| | - Emma C. Hart
- School of Physiology and Pharmacology, University of Bristol, Bristol UK
| | - B. Gunnar Wallin
- Institute of Neuroscience and Physiology, The Sahlgren Academy at Gothenburg University, Goteborg, Sweden
| | - Nisha Charkoudian
- Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA
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Usselman CW, Gimon TI, Nielson CA, Luchyshyn TA, Coverdale NS, Van Uum SHM, Shoemaker JK. Menstrual cycle and sex effects on sympathetic responses to acute chemoreflex stress. Am J Physiol Heart Circ Physiol 2014; 308:H664-71. [PMID: 25527774 DOI: 10.1152/ajpheart.00345.2014] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
This study aimed to examine the effects of sex (males vs. females) and sex hormones (menstrual cycle phases in women) on sympathetic responsiveness to severe chemoreflex activation in young, healthy individuals. Muscle sympathetic nerve activity (MSNA) was measured at baseline and during rebreathing followed by a maximal end-inspiratory apnea. In women, baseline MSNA was greater in the midluteal (ML) than early-follicular (EF) phase of the menstrual cycle. Baseline MSNA burst incidence was greater in men than women, while burst frequency and total MSNA were similar between men and women only in the ML phase. Chemoreflex activation evoked graded increases in MSNA burst frequency, amplitude, and total activity in all participants. In women, this sympathoexcitation was greater in the EF than ML phase. The sympathoexcitatory response to chemoreflex stimulation of the EF phase in women was also greater than in men. Nonetheless, changes in total peripheral resistance were similar between sexes and menstrual cycle phases. This indicates that neurovascular transduction was attenuated during the EF phase during chemoreflex activation, thereby offsetting the exaggerated sympathoexcitation. Chemoreflex-induced increases in mean arterial pressure were similar across sexes and menstrual cycle phases. During acute chemoreflex stimulation, reduced neurovascular transduction could provide a mechanism by which apnea-associated morbidity might be attenuated in women relative to men.
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Affiliation(s)
- Charlotte W Usselman
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada
| | - Tamara I Gimon
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada
| | - Chantelle A Nielson
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada
| | - Torri A Luchyshyn
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada
| | - Nicole S Coverdale
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada
| | - Stan H M Van Uum
- Department of Medicine, Western University, London, Ontario, Canada; Lawson Health Research Institute, Western University, London, Ontario, Canada; and
| | - J Kevin Shoemaker
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada; Department of Physiology and Pharmacology, Western University, London, Ontario, Canada
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Hart ECJ, Charkoudian N. Sympathetic neural regulation of blood pressure: influences of sex and aging. Physiology (Bethesda) 2014; 29:8-15. [PMID: 24382867 DOI: 10.1152/physiol.00031.2013] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Sex and age have important influences on sympathetic neural control of blood pressure in humans. Young women are relatively protected against risk of hypertension due to greater peripheral vasodilator influences compared with young men and older people. This protective effect is lost at menopause. Older men and women have higher sympathetic nerve activity and tighter coupling between SNA and blood pressure, contributing to the increased risk of hypertension with aging.
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Affiliation(s)
- E C J Hart
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom; and
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Hinojosa-Laborde C, Shade RE, Muniz GW, Bauer C, Goei KA, Pidcoke HF, Chung KK, Cap AP, Convertino VA. Validation of lower body negative pressure as an experimental model of hemorrhage. J Appl Physiol (1985) 2013; 116:406-15. [PMID: 24356525 DOI: 10.1152/japplphysiol.00640.2013] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Lower body negative pressure (LBNP), a model of hemorrhage (Hem), shifts blood to the legs and elicits central hypovolemia. This study compared responses to LBNP and actual Hem in sedated baboons. Arterial pressure, pulse pressure (PP), central venous pressure (CVP), heart rate, stroke volume (SV), and +dP/dt were measured. Hem steps were 6.25%, 12.5%, 18.75%, and 25% of total estimated blood volume. Shed blood was returned, and 4 wk after Hem, the same animals were subjected to four LBNP levels which elicited equivalent changes in PP and CVP observed during Hem. Blood gases, hematocrit (Hct), hemoglobin (Hb), plasma renin activity (PRA), vasopressin (AVP), epinephrine (EPI), and norepinephrine (NE) were measured at baseline and maximum Hem or LBNP. LBNP levels matched with 6.25%, 12.5%, 18.75%, and 25% hemorrhage were -22 ± 6, -41 ± 7, -54 ± 10, and -71 ± 7 mmHg, respectively (mean ± SD). Hemodynamic responses to Hem and LBNP were similar. SV decreased linearly such that 25% Hem and matching LBNP caused a 50% reduction in SV. Hem caused a decrease in Hct, Hb, and central venous oxygen saturation (ScvO2). In contrast, LBNP increased Hct and Hb, while ScvO2 remained unchanged. Hem caused greater elevations in AVP and NE than LBNP, while PRA, EPI, and other hematologic indexes did not differ between studies. These results indicate that while LBNP does not elicit the same effect on blood cell loss as Hem, LBNP mimics the integrative cardiovascular response to Hem, and validates the use of LBNP as an experimental model of central hypovolemia associated with Hem.
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Patel HM, Heffernan MJ, Ross AJ, Muller MD. Sex differences in forearm vasoconstrictor response to voluntary apnea. Am J Physiol Heart Circ Physiol 2013; 306:H309-16. [PMID: 24322616 DOI: 10.1152/ajpheart.00746.2013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Clinical evidence indicates that obstructive sleep apnea is more common and more severe in men compared with women. Sex differences in the vasoconstrictor response to hypoxemia-induced sympathetic activation might contribute to this clinical observation. In the current laboratory study, we determined sex differences in the acute physiological responses to maximal voluntary end-expiratory apnea (MVEEA) during wakefulness in healthy young men and women (26 ± 1 yr) as well as healthy older men and women (64 ± 2 yr). Mean arterial pressure (MAP), heart rate (HR), brachial artery blood flow velocity (BBFV, Doppler ultrasound), and cutaneous vascular conductance (CVC, laser Doppler flowmetry) were measured, and changes in physiological parameters from baseline were compared between groups. The breath-hold duration and oxygen-saturation nadir were similar between groups. In response to MVEEA, young women had significantly less forearm vasoconstriction compared with young men (ΔBBFV: 2 ± 7 vs. -25 ± 6% and ΔCVC: -5 ± 4 vs. -31 ± 4%), whereas ΔMAP (12 ± 2 vs. 16 ± 3 mmHg) and ΔHR (4 ± 2 vs. 6 ± 3 bpm) were comparable between groups. The attenuated forearm vasoconstriction in young women was not observed in postmenopausal women (ΔBBFV -21 ± 5%). We concluded that young women have blunted forearm vasoconstriction in response to MVEEA compared with young men, and this effect is not evident in older postmenopausal women. These data suggest that female sex hormones dampen neurogenic vasoconstriction in response to apnea-induced hypoxemia.
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Affiliation(s)
- Hardikkumar M Patel
- Pennsylvania State University College of Medicine, Penn State Hershey Heart and Vascular Institute, Hershey, Pennsylvania
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