Altered vestibular signaling and body unloading in microgravity results in sensory reweighting an... more Altered vestibular signaling and body unloading in microgravity results in sensory reweighting and adaptation. Microgravity effects are well-replicated in head-down tilt bed rest (HDBR). Artificial gravity (AG) is a potential countermeasure to mitigate effects of microgravity. We examined the effectiveness of daily AG for mitigating brain and/or behavioral changes in 60 days of HDBR. One group received AG for 30 minutes daily (AG; n=16) and a control group spent the same time in HDBR but received no AG (CTRL; n=8). All participants performed a sensorimotor adaptation task 5 times during fMRI scanning: twice prior to HDBR twice during HDBR, and once following HDBR. The AG group showed similar behavioral adaptation effects compared with the CTRLs. We identified decreased brain activation in the AG group from pre to late HDBR in the cerebellum for the task baseline portion and in the thalamus, calcarine, cuneus, premotor cortices, and superior frontal gyrus in the AG group during the e...
BACKGROUND Radiation and reduced gravity impose a major burden on health and performance during h... more BACKGROUND Radiation and reduced gravity impose a major burden on health and performance during human spaceflight. While radiation increases cancer risk and limits tissue regeneration, reduced gravity predisposes to musculoskeletal and cardiovascular deconditioning. Deconditioning could conceivably limit the recovery from radiation damage. Our aim was to develop a terrestrial ex vivo model that could be utilized to study the interaction between simulated reduced gravity using head-down-tilt bed rest and radiation on cellular DNA repair
Objectives Carbon dioxide (CO2) levels on board the International Space Station reach 10× those o... more Objectives Carbon dioxide (CO2) levels on board the International Space Station reach 10× those of outdoor terrestrial levels. We report here studies assessing whether increased levels of ambient CO2 contribute to elevated bone resorption characteristically observed with bed rest as an analog for skeletal unloading during spaceflight. Methods Data are reported from two ground-based studies which included 12 male and 7 female subjects placed in a strict −6° head-down tilt (HDT) position for 30 days at 0.5% ambient CO2 or 60 days with nominal environment (0.04% CO2). Subjects were neither afforded a pillow nor allowed to use an elbow while eating to increase headward fluid pressure. Bone mineral density (BMD) and bone mineral content (BMC) were measured with dual-energy X-ray absorptiometry. Blood and urine were collected before and during HDT for analysis. Results There was no change in BMD or BMC. Excretion of collagen crosslinks increased during HDT (p < 0.001) with no additive ...
The altered vestibular signaling and somatosensory unloading of microgravity result in sensory re... more The altered vestibular signaling and somatosensory unloading of microgravity result in sensory reweighting and adaptation to conflicting sensory inputs. Aftereffects of these adaptive changes are evident postflight as impairments in behaviors such as balance and gait. Microgravity also induces fluid shifts toward the head and an upward shift of the brain within the skull; these changes are well-replicated in strict head-down tilt bed rest (HDBR), a spaceflight analog environment. Artificial gravity (AG) is a potential countermeasure to mitigate these effects of microgravity. A previous study demonstrated that intermittent (six, 5-mins bouts per day) daily AG sessions were more efficacious at counteracting orthostatic intolerance in a 5 day HDBR study than continuous daily AG. Here we examined whether intermittent daily AG was also more effective than continuous dosing for mitigating brain and behavioral changes in response to 60 days of HDBR. Participants (n = 24) were split evenly ...
This is the first bed rest campaign examining sensorimotor adaptation and savings in response to ... more This is the first bed rest campaign examining sensorimotor adaptation and savings in response to the combined effect of HDBR + CO2 and to observe signs of spaceflight-associated neuro-ocular syndrome (SANS) in HDBR participants. Our findings suggest that HDBR + CO2 alters the way that individuals engage in sensorimotor processing. Individuals who developed signs of SANS seem to rely more on implicit rather than cognitive processing of adaptive behaviors than subjects who did not present signs of SANS.
BackgroundCardiovascular risk may be increased in astronauts after long term space flights based ... more BackgroundCardiovascular risk may be increased in astronauts after long term space flights based on biomarkers indicating premature vascular aging. We tested the hypothesis that 60 days of strict 6° head down tilt bed rest (HDTBR), an established space analog, promotes vascular stiffening and that artificial gravity training ameliorates the response.MethodsWe studied 24 healthy participants (8 women, 24–55 years, BMI = 24.3 ± 2.1 kg/m2) before and at the end of 60 days HDTBR. 16 subjects were assigned to daily artificial gravity. We applied echocardiography to measure stroke volume and isovolumetric contraction time (ICT), calculated aortic compliance (stroke volume/aortic pulse pressure), and assessed aortic distensibility by MRI. Furthermore, we measured brachial-femoral pulse wave velocity (bfPWV) and pulse wave arrival times (PAT) in different vascular beds by blood pressure cuffs and photoplethysmography. We corrected PAT for ICT (cPAT).ResultsIn the pooled sample, diastolic bl...
Over the last decades a significant body of knowledge has been gained on the adaptation of the hu... more Over the last decades a significant body of knowledge has been gained on the adaptation of the human body going into near weightlessness conditions as well as for the re-adaptation to 1xg Earth conditions after an orbital space flight. Ground-based paradigms for microgravity simulation have been developed such as head down tilted bed rest or dry-immersion studies. In such systems adaptations of the human body to long term immobilization and increased upper-body fluid shifts bed have been studied. But could we learn something on human body adaptations to altered gravity conditions using centrifuges? How does the body adapt to a long duration (days, weeks or longer) exposure to a hypergravity environment? And, once the body has fully adapted to a hypergravity environment, how does it re-adapt going from a hypergravity condition to a relatively hypo-gravity condition of 1xg, or even going from centrifuge / hypergravity environment into a bed-rest setting? Can such transitions learn us ...
Abstract In 2017, the study, Vision Impairment and Intracranial Pressure and Psychological Enviha... more Abstract In 2017, the study, Vision Impairment and Intracranial Pressure and Psychological Envihab Research, dubbed VaPER, was conducted in the:envihab facility in Cologne, Germany to determine whether 30 days of bed rest at 6° head down tilt in an increased ambient CO2 (hypercapnic) environment contributes to the deterioration of ocular anatomy and to changes in musculoskeletal, nutritional, hematological, immunological, behavioral, and balance functions. A set of international standard measures were used to evaluate bone, muscle, and nutritional status, and to assess the function of the cardiovascular, sensorimotor, visual, and immune systems, and psychological state. Strict 6° head-down tilt bed rest in an elevated ambient CO2 environment induced mild immunological dysregulation. After bed rest, selenium, urinary iodine, and folate status were lower in the subjects of the VaPER study than they were in subjects of previous bed rest studies of similar duration, which likely reflects regional differences in diet and nutritional status. Bed rest induced optic disc edema in 5 of the 11 subjects. Interestingly, the subjects who were diagnosed with optic disc edema, as determined by fundoscopy imaging, also tended to exhibit higher body temperature and overall higher levels of anxiety and insomnia during bed rest.
Astronauts on board the International Space Station (ISS) must adapt to several environmental cha... more Astronauts on board the International Space Station (ISS) must adapt to several environmental challenges including microgravity, elevated carbon dioxide (CO2), and isolation while performing highly controlled movements with complex equipment. Head down tilt bed rest (HDBR) is an analog used to study spaceflight factors including body unloading and headward fluid shifts. We recently reported how HDBR with elevated CO2 (HDBR+CO2) affects visuomotor adaptation. Here we expand upon this work and examine the effects of HDBR+CO2 on brain activity during visuomotor adaptation. Eleven participants (34 ± 8 years) completed six functional MRI (fMRI) sessions pre-, during, and post-HDBR+CO2. During fMRI, participants completed a visuomotor adaptation task, divided into baseline, early, late and de-adaptation. Additionally, we compare brain activity between this NASA campaign (30-day HDBR+CO2) and a different campaign with a separate set of participants (60-day HDBR with normal atmospheric CO2 ...
ABSTRACTFollowing long-duration spaceflight, some astronauts exhibit ophthalmic structural change... more ABSTRACTFollowing long-duration spaceflight, some astronauts exhibit ophthalmic structural changes referred to as Spaceflight Associated Neuro-ocular Syndrome (SANS). Optic disc edema is a common sign of SANS. The origin and effects of SANS are not understood as signs of SANS have not manifested in previous spaceflight analog studies. In the current spaceflight analog study, eleven subjects underwent 30 days of strict head down-tilt bed rest in elevated ambient carbon dioxide (HDBR+CO2). Using functional magnetic resonance imaging (fMRI), we acquired resting-state fMRI data at 6 time points: before (2), during (2), and after (2) the HDBR+CO2 intervention. Five participants developed optic disc edema during the intervention (SANS subgroup) and 6 did not (NoSANS group). This occurrence allowed us to explore whether development of signs of SANS during the spaceflight analog impacted resting-state functional connectivity during HDBR+CO2. In light of previous work identifying genetic and...
ABSTRACTAstronauts are exposed to microgravity and elevated CO2 levels onboard the International ... more ABSTRACTAstronauts are exposed to microgravity and elevated CO2 levels onboard the International Space Station. Little is known about how microgravity and elevated CO2 combine to affect the brain and sensorimotor performance during and after spaceflight. Here we examined changes in resting-state functional connectivity (FC) and sensorimotor behavior associated with a spaceflight analog environment. Participants underwent 30 days of strict 6° head-down tilt bed rest with elevated ambient CO2 (HDBR+CO2). Resting-state functional magnetic resonance imaging and sensorimotor assessments were collected 13 and 7 days prior to bed rest, on days 7 and 29 of bed rest, and 0, 5, 12, and 13 days following bed rest. We assessed the time course of FC changes from before, during, to after HDBR+CO2. We then compared the observed connectivity changes with those of a HDBR control group, which underwent HDBR in standard ambient air. Moreover, we assessed associations between post-HDBR+CO2 FC changes a...
In the context of space physiology, research is being conducted to understand the physiological e... more In the context of space physiology, research is being conducted to understand the physiological effects from radiation, hypogravity, spaceflight and planetary environments. The goal is to identify new methods to address the unique challenges in medical treatment, human factors, and behavioral health support on future exploration missions. As crew size is small and time is limited during actual missions, space agencies resort to addressing the effects of space travel in analog environments that have features similar to those of spaceflight. Head-down tilt bed rest (HDBR), for instance, is one of the established terrestrial models used to simulate some of the physiological changes experienced during spaceflight under weightless conditions and is therefore considered a valuable testbed to prepare for future long-duration exploration missions. HDBR studies are performed in extremely-well controlled laboratory settings, offering the possibility to test the effects of – what is in essence...
Cerebral hemodynamics and venous outflow from the brain may be altered during exposure to microgr... more Cerebral hemodynamics and venous outflow from the brain may be altered during exposure to microgravity or head-down tilt (HDT), an analog of microgravity, as well as by increased ambient CO2 exposure as experienced on the International Space Station. Six healthy subjects underwent baseline tilt table testing at 0°, 6°, 12°, 18°, 24°, and 30° HDT. The right internal jugular (IJ) vein cross-sectional area (CSA) was measured at four intervals from the submandibular to the clavicular level and IJ volume was calculated. Further measurements of the IJ vein were made after ∼26 h of 12° HDT bed rest with either ambient air or 0.5% CO2 exposure, and plasma and blood volume were assessed after 4 h, 24 h, and 28.5 h HDT. IJ vein CSA and volume increased with progressively steeper HDT angles during baseline tilt table testing, with more prominent filling of the IJ vein at levels closer to the clavicle. Exposure to 26 h of 12° HDT bed rest with or without increased CO2, however, had little addit...
Journal of applied physiology (Bethesda, Md. : 1985), Jan 30, 2017
Astronauts aboard the International Space Station (ISS) have exhibited hyperopic shifts, posterio... more Astronauts aboard the International Space Station (ISS) have exhibited hyperopic shifts, posterior eye globe flattening, dilated optic nerve sheaths, and even optic disc swelling from spaceflight. Elevated intracranial pressure (ICP) consequent to cephalad fluid shifts is commonly hypothesized as contributing to these ocular changes. Head-down tilt (HDT) is frequently utilized as an Earth-based analog to study similar fluid shifts. Sealed environments like the ISS also exhibit elevated carbon dioxide (CO2), a potent arteriolar vasodilator that could further affect cerebral blood volume and flow, intracranial compliance, and ICP. A collaborative pilot study between the National Space Biomedical Research Institute and the German Aerospace Center tested the hypotheses that: (1) HDT and elevated CO2 physiologically interact, and (2) cerebrovascular pulsatility is related to HDT and/or elevated CO2 In a double-blind crossover study (n=6), we measured cerebral blood volume (CBV) pulsatili...
Altered vestibular signaling and body unloading in microgravity results in sensory reweighting an... more Altered vestibular signaling and body unloading in microgravity results in sensory reweighting and adaptation. Microgravity effects are well-replicated in head-down tilt bed rest (HDBR). Artificial gravity (AG) is a potential countermeasure to mitigate effects of microgravity. We examined the effectiveness of daily AG for mitigating brain and/or behavioral changes in 60 days of HDBR. One group received AG for 30 minutes daily (AG; n=16) and a control group spent the same time in HDBR but received no AG (CTRL; n=8). All participants performed a sensorimotor adaptation task 5 times during fMRI scanning: twice prior to HDBR twice during HDBR, and once following HDBR. The AG group showed similar behavioral adaptation effects compared with the CTRLs. We identified decreased brain activation in the AG group from pre to late HDBR in the cerebellum for the task baseline portion and in the thalamus, calcarine, cuneus, premotor cortices, and superior frontal gyrus in the AG group during the e...
BACKGROUND Radiation and reduced gravity impose a major burden on health and performance during h... more BACKGROUND Radiation and reduced gravity impose a major burden on health and performance during human spaceflight. While radiation increases cancer risk and limits tissue regeneration, reduced gravity predisposes to musculoskeletal and cardiovascular deconditioning. Deconditioning could conceivably limit the recovery from radiation damage. Our aim was to develop a terrestrial ex vivo model that could be utilized to study the interaction between simulated reduced gravity using head-down-tilt bed rest and radiation on cellular DNA repair
Objectives Carbon dioxide (CO2) levels on board the International Space Station reach 10× those o... more Objectives Carbon dioxide (CO2) levels on board the International Space Station reach 10× those of outdoor terrestrial levels. We report here studies assessing whether increased levels of ambient CO2 contribute to elevated bone resorption characteristically observed with bed rest as an analog for skeletal unloading during spaceflight. Methods Data are reported from two ground-based studies which included 12 male and 7 female subjects placed in a strict −6° head-down tilt (HDT) position for 30 days at 0.5% ambient CO2 or 60 days with nominal environment (0.04% CO2). Subjects were neither afforded a pillow nor allowed to use an elbow while eating to increase headward fluid pressure. Bone mineral density (BMD) and bone mineral content (BMC) were measured with dual-energy X-ray absorptiometry. Blood and urine were collected before and during HDT for analysis. Results There was no change in BMD or BMC. Excretion of collagen crosslinks increased during HDT (p < 0.001) with no additive ...
The altered vestibular signaling and somatosensory unloading of microgravity result in sensory re... more The altered vestibular signaling and somatosensory unloading of microgravity result in sensory reweighting and adaptation to conflicting sensory inputs. Aftereffects of these adaptive changes are evident postflight as impairments in behaviors such as balance and gait. Microgravity also induces fluid shifts toward the head and an upward shift of the brain within the skull; these changes are well-replicated in strict head-down tilt bed rest (HDBR), a spaceflight analog environment. Artificial gravity (AG) is a potential countermeasure to mitigate these effects of microgravity. A previous study demonstrated that intermittent (six, 5-mins bouts per day) daily AG sessions were more efficacious at counteracting orthostatic intolerance in a 5 day HDBR study than continuous daily AG. Here we examined whether intermittent daily AG was also more effective than continuous dosing for mitigating brain and behavioral changes in response to 60 days of HDBR. Participants (n = 24) were split evenly ...
This is the first bed rest campaign examining sensorimotor adaptation and savings in response to ... more This is the first bed rest campaign examining sensorimotor adaptation and savings in response to the combined effect of HDBR + CO2 and to observe signs of spaceflight-associated neuro-ocular syndrome (SANS) in HDBR participants. Our findings suggest that HDBR + CO2 alters the way that individuals engage in sensorimotor processing. Individuals who developed signs of SANS seem to rely more on implicit rather than cognitive processing of adaptive behaviors than subjects who did not present signs of SANS.
BackgroundCardiovascular risk may be increased in astronauts after long term space flights based ... more BackgroundCardiovascular risk may be increased in astronauts after long term space flights based on biomarkers indicating premature vascular aging. We tested the hypothesis that 60 days of strict 6° head down tilt bed rest (HDTBR), an established space analog, promotes vascular stiffening and that artificial gravity training ameliorates the response.MethodsWe studied 24 healthy participants (8 women, 24–55 years, BMI = 24.3 ± 2.1 kg/m2) before and at the end of 60 days HDTBR. 16 subjects were assigned to daily artificial gravity. We applied echocardiography to measure stroke volume and isovolumetric contraction time (ICT), calculated aortic compliance (stroke volume/aortic pulse pressure), and assessed aortic distensibility by MRI. Furthermore, we measured brachial-femoral pulse wave velocity (bfPWV) and pulse wave arrival times (PAT) in different vascular beds by blood pressure cuffs and photoplethysmography. We corrected PAT for ICT (cPAT).ResultsIn the pooled sample, diastolic bl...
Over the last decades a significant body of knowledge has been gained on the adaptation of the hu... more Over the last decades a significant body of knowledge has been gained on the adaptation of the human body going into near weightlessness conditions as well as for the re-adaptation to 1xg Earth conditions after an orbital space flight. Ground-based paradigms for microgravity simulation have been developed such as head down tilted bed rest or dry-immersion studies. In such systems adaptations of the human body to long term immobilization and increased upper-body fluid shifts bed have been studied. But could we learn something on human body adaptations to altered gravity conditions using centrifuges? How does the body adapt to a long duration (days, weeks or longer) exposure to a hypergravity environment? And, once the body has fully adapted to a hypergravity environment, how does it re-adapt going from a hypergravity condition to a relatively hypo-gravity condition of 1xg, or even going from centrifuge / hypergravity environment into a bed-rest setting? Can such transitions learn us ...
Abstract In 2017, the study, Vision Impairment and Intracranial Pressure and Psychological Enviha... more Abstract In 2017, the study, Vision Impairment and Intracranial Pressure and Psychological Envihab Research, dubbed VaPER, was conducted in the:envihab facility in Cologne, Germany to determine whether 30 days of bed rest at 6° head down tilt in an increased ambient CO2 (hypercapnic) environment contributes to the deterioration of ocular anatomy and to changes in musculoskeletal, nutritional, hematological, immunological, behavioral, and balance functions. A set of international standard measures were used to evaluate bone, muscle, and nutritional status, and to assess the function of the cardiovascular, sensorimotor, visual, and immune systems, and psychological state. Strict 6° head-down tilt bed rest in an elevated ambient CO2 environment induced mild immunological dysregulation. After bed rest, selenium, urinary iodine, and folate status were lower in the subjects of the VaPER study than they were in subjects of previous bed rest studies of similar duration, which likely reflects regional differences in diet and nutritional status. Bed rest induced optic disc edema in 5 of the 11 subjects. Interestingly, the subjects who were diagnosed with optic disc edema, as determined by fundoscopy imaging, also tended to exhibit higher body temperature and overall higher levels of anxiety and insomnia during bed rest.
Astronauts on board the International Space Station (ISS) must adapt to several environmental cha... more Astronauts on board the International Space Station (ISS) must adapt to several environmental challenges including microgravity, elevated carbon dioxide (CO2), and isolation while performing highly controlled movements with complex equipment. Head down tilt bed rest (HDBR) is an analog used to study spaceflight factors including body unloading and headward fluid shifts. We recently reported how HDBR with elevated CO2 (HDBR+CO2) affects visuomotor adaptation. Here we expand upon this work and examine the effects of HDBR+CO2 on brain activity during visuomotor adaptation. Eleven participants (34 ± 8 years) completed six functional MRI (fMRI) sessions pre-, during, and post-HDBR+CO2. During fMRI, participants completed a visuomotor adaptation task, divided into baseline, early, late and de-adaptation. Additionally, we compare brain activity between this NASA campaign (30-day HDBR+CO2) and a different campaign with a separate set of participants (60-day HDBR with normal atmospheric CO2 ...
ABSTRACTFollowing long-duration spaceflight, some astronauts exhibit ophthalmic structural change... more ABSTRACTFollowing long-duration spaceflight, some astronauts exhibit ophthalmic structural changes referred to as Spaceflight Associated Neuro-ocular Syndrome (SANS). Optic disc edema is a common sign of SANS. The origin and effects of SANS are not understood as signs of SANS have not manifested in previous spaceflight analog studies. In the current spaceflight analog study, eleven subjects underwent 30 days of strict head down-tilt bed rest in elevated ambient carbon dioxide (HDBR+CO2). Using functional magnetic resonance imaging (fMRI), we acquired resting-state fMRI data at 6 time points: before (2), during (2), and after (2) the HDBR+CO2 intervention. Five participants developed optic disc edema during the intervention (SANS subgroup) and 6 did not (NoSANS group). This occurrence allowed us to explore whether development of signs of SANS during the spaceflight analog impacted resting-state functional connectivity during HDBR+CO2. In light of previous work identifying genetic and...
ABSTRACTAstronauts are exposed to microgravity and elevated CO2 levels onboard the International ... more ABSTRACTAstronauts are exposed to microgravity and elevated CO2 levels onboard the International Space Station. Little is known about how microgravity and elevated CO2 combine to affect the brain and sensorimotor performance during and after spaceflight. Here we examined changes in resting-state functional connectivity (FC) and sensorimotor behavior associated with a spaceflight analog environment. Participants underwent 30 days of strict 6° head-down tilt bed rest with elevated ambient CO2 (HDBR+CO2). Resting-state functional magnetic resonance imaging and sensorimotor assessments were collected 13 and 7 days prior to bed rest, on days 7 and 29 of bed rest, and 0, 5, 12, and 13 days following bed rest. We assessed the time course of FC changes from before, during, to after HDBR+CO2. We then compared the observed connectivity changes with those of a HDBR control group, which underwent HDBR in standard ambient air. Moreover, we assessed associations between post-HDBR+CO2 FC changes a...
In the context of space physiology, research is being conducted to understand the physiological e... more In the context of space physiology, research is being conducted to understand the physiological effects from radiation, hypogravity, spaceflight and planetary environments. The goal is to identify new methods to address the unique challenges in medical treatment, human factors, and behavioral health support on future exploration missions. As crew size is small and time is limited during actual missions, space agencies resort to addressing the effects of space travel in analog environments that have features similar to those of spaceflight. Head-down tilt bed rest (HDBR), for instance, is one of the established terrestrial models used to simulate some of the physiological changes experienced during spaceflight under weightless conditions and is therefore considered a valuable testbed to prepare for future long-duration exploration missions. HDBR studies are performed in extremely-well controlled laboratory settings, offering the possibility to test the effects of – what is in essence...
Cerebral hemodynamics and venous outflow from the brain may be altered during exposure to microgr... more Cerebral hemodynamics and venous outflow from the brain may be altered during exposure to microgravity or head-down tilt (HDT), an analog of microgravity, as well as by increased ambient CO2 exposure as experienced on the International Space Station. Six healthy subjects underwent baseline tilt table testing at 0°, 6°, 12°, 18°, 24°, and 30° HDT. The right internal jugular (IJ) vein cross-sectional area (CSA) was measured at four intervals from the submandibular to the clavicular level and IJ volume was calculated. Further measurements of the IJ vein were made after ∼26 h of 12° HDT bed rest with either ambient air or 0.5% CO2 exposure, and plasma and blood volume were assessed after 4 h, 24 h, and 28.5 h HDT. IJ vein CSA and volume increased with progressively steeper HDT angles during baseline tilt table testing, with more prominent filling of the IJ vein at levels closer to the clavicle. Exposure to 26 h of 12° HDT bed rest with or without increased CO2, however, had little addit...
Journal of applied physiology (Bethesda, Md. : 1985), Jan 30, 2017
Astronauts aboard the International Space Station (ISS) have exhibited hyperopic shifts, posterio... more Astronauts aboard the International Space Station (ISS) have exhibited hyperopic shifts, posterior eye globe flattening, dilated optic nerve sheaths, and even optic disc swelling from spaceflight. Elevated intracranial pressure (ICP) consequent to cephalad fluid shifts is commonly hypothesized as contributing to these ocular changes. Head-down tilt (HDT) is frequently utilized as an Earth-based analog to study similar fluid shifts. Sealed environments like the ISS also exhibit elevated carbon dioxide (CO2), a potent arteriolar vasodilator that could further affect cerebral blood volume and flow, intracranial compliance, and ICP. A collaborative pilot study between the National Space Biomedical Research Institute and the German Aerospace Center tested the hypotheses that: (1) HDT and elevated CO2 physiologically interact, and (2) cerebrovascular pulsatility is related to HDT and/or elevated CO2 In a double-blind crossover study (n=6), we measured cerebral blood volume (CBV) pulsatili...
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Papers by Edwin Mulder