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  • 1
    Online Resource
    Online Resource
    Graded lower body negative pressure induces intraventricular negative pressures and incremental diastolic suction: a pressure-volume study in a porcine model
    American Physiological Society ; 2022
    In:  Journal of Applied Physiology Vol. 133, No. 1 ( 2022-07-01), p. 20-26
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 133, No. 1 ( 2022-07-01), p. 20-26
    Abstract: Lower body negative pressure (LBNP) is a tool to study compensatory mechanisms to central hypovolemia for decades. However, the underlying hemodynamic mechanisms were mostly assessed noninvasively and remain unclear. We hypothesized that incremental LBNP reduces diastolic filling and thereby affects left ventricular (LV) diastolic suction (DS). Here, we investigated the impact of graded LBNP at three different levels of seal as well as during β-adrenergic stimulation by invasive pressure-volume (PV) analysis. Eight Landrace pigs were instrumented closed-chest for PV assessment. LBNP was applied at three consecutive locations: I) cranial, 10 cm below xiphoid process; II) medial, half-way between cranial and caudal; III) caudal, at the iliac spine. Level III was repeated under dobutamine infusion. At each level, baseline measurements were followed by application of incremental LBNP of −15, −30, and −45 mmHg. LBNP induced varying degrees of preload-dependent hemodynamic changes, with cranial LBNP inducing more pronounced effects than caudal. According to the Frank–Starling mechanism, graded LBNP progressively reduced LV stroke volume (LV SV) following a decrease in LV end-diastolic volume. Negative intraventricular minimal pressures were observed during dobutamine-infusion as well as higher levels of LBNP. Of note, incremental LV negative pressures were accompanied by increasing DS volumes, derived by extrapolating the volume at zero transmural pressure, the so-called equilibrium volume ( V 0 ), related to LV SV. In conclusion, graded preload reduction via LBNP shifts the PV loop to smaller volumes and end-systolic volume below V 0 , which induces negative LV pressures and increases LV suction. Accordingly, LBNP-induced central hypovolemia is associated with increased DS. NEW & NOTEWORTHY This study examined the effects of incremental lower body negative pressure (LBNP) from −15 to −45 mmHg on hemodynamic regulation using invasive pressure-volume assessment in closed-chest pigs. Graded preload reduction via LBNP induces negative left ventricular (LV) pressures while increasing LV suction and thus allowing the ventricle to eject below the equilibrium volume at the end of systole. Accordingly, LBNP-induced central hypovolemia is associated with increased diastolic suction.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/japplphysiol.00110.2022
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2022
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
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  • 2
    Online Resource
    Online Resource
    Lower Body Negative Pressure: Physiological Effects, Applications, and Implementation
    American Physiological Society ; 2019
    In:  Physiological Reviews Vol. 99, No. 1 ( 2019-01-01), p. 807-851
    Details
    In: Physiological Reviews, American Physiological Society, Vol. 99, No. 1 ( 2019-01-01), p. 807-851
    Abstract: This review presents lower body negative pressure (LBNP) as a unique tool to investigate the physiology of integrated systemic compensatory responses to altered hemodynamic patterns during conditions of central hypovolemia in humans. An early review published in Physiological Reviews over 40 yr ago (Wolthuis et al. Physiol Rev 54: 566–595, 1974) focused on the use of LBNP as a tool to study effects of central hypovolemia, while more than a decade ago a review appeared that focused on LBNP as a model of hemorrhagic shock (Cooke et al. J Appl Physiol (1985) 96: 1249–1261, 2004). Since then there has been a great deal of new research that has applied LBNP to investigate complex physiological responses to a variety of challenges including orthostasis, hemorrhage, and other important stressors seen in humans such as microgravity encountered during spaceflight. The LBNP stimulus has provided novel insights into the physiology underlying areas such as intolerance to reduced central blood volume, sex differences concerning blood pressure regulation, autonomic dysfunctions, adaptations to exercise training, and effects of space flight. Furthermore, approaching cardiovascular assessment using prediction models for orthostatic capacity in healthy populations, derived from LBNP tolerance protocols, has provided important insights into the mechanisms of orthostatic hypotension and central hypovolemia, especially in some patient populations as well as in healthy subjects. This review also presents a concise discussion of mathematical modeling regarding compensatory responses induced by LBNP. Given the diverse applications of LBNP, it is to be expected that new and innovative applications of LBNP will be developed to explore the complex physiological mechanisms that underline health and disease.
    Type of Medium: Online Resource
    ISSN: 0031-9333 , 1522-1210
    URL: Article
    DOI: 10.1152/physrev.00006.2018
    RVK:
    WA 15000
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2019
    detail.hit.zdb_id: 1471693-8
    SSG: 12
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  • 3
    Online Resource
    Online Resource
    Going against the flow: are venous thromboembolism and impaired cerebral drainage critical risks for spaceflight?
    American Physiological Society ; 2022
    In:  Journal of Applied Physiology Vol. 132, No. 1 ( 2022-01-01), p. 270-273
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 132, No. 1 ( 2022-01-01), p. 270-273
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/japplphysiol.00425.2021
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2022
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
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  • 4
    Online Resource
    Online Resource
    Teaching fluid shifts during orthostasis using a classic paper by Foux et al.
    American Physiological Society ; 2011
    In:  Advances in Physiology Education Vol. 35, No. 4 ( 2011-12), p. 330-335
    Details
    In: Advances in Physiology Education, American Physiological Society, Vol. 35, No. 4 ( 2011-12), p. 330-335
    Abstract: Hypovolemic and orthostatic challenge can be simulated in humans by the application of lower body negative pressure (LBNP), because this perturbation leads to peripheral blood pooling and, consequently, central hypovolemia. The classic paper by Foux and colleagues clearly shows the effects of orthostasis simulated by LBNP on fluid shifts and homeostatic mechanisms. The carefully carried out experiments reported in this paper show the interplay between different physiological control systems to ensure blood pressure regulation, failure of which could lead to critical decreases in cerebral blood flow and syncope. Here, a teaching seminar for graduate students is described that is designed in the context of this paper and aimed at allowing students to learn how Foux and colleagues have advanced this field by addressing important aspects of blood regulation. This seminar is also designed to put their research into perspective by including important components of LBNP testing and protocols developed in subsequent research in the field. Learning about comprehensive protocols and carefully controlled studies can reduce confounding variables and allow for an optimal analysis and elucidation of the physiological responses that are being investigated. Finally, in collaboration with researchers in mathematical modeling, in the future, we will incorporate the concepts of applicable mathematical models into our curriculum.
    Type of Medium: Online Resource
    ISSN: 1043-4046 , 1522-1229
    URL: Article
    DOI: 10.1152/advan.00071.2011
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2011
    detail.hit.zdb_id: 1477338-7
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  • 5
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    Online Resource
    Assessing formal teaching of ethics in physiology: an empirical survey, patterns, and recommendations
    American Physiological Society ; 2012
    In:  Advances in Physiology Education Vol. 36, No. 3 ( 2012-09), p. 188-191
    Details
    In: Advances in Physiology Education, American Physiological Society, Vol. 36, No. 3 ( 2012-09), p. 188-191
    Abstract: Ethics should be an important component of physiological education. In this report, we examined to what extent teaching of ethics is formally being incorporated into the physiology curriculum. We carried out an e-mail survey in which we asked the e-mail recipients whether their institution offered a course or lecture on ethics as part of the physiology teaching process at their institution, using the following query: “We are now doing an online survey in which we would like to know whether you offer a course or a lecture on ethics as part of your physiology teaching curriculum.” The response rate was 53.3%: we received 104 responses of a total of 195 sent out. Our responses came from 45 countries. While all of our responders confirmed that there was a need for ethics during medical education and scientific training, the degree of inclusion of formal ethics in the physiology curriculum varied widely. Our survey showed that, in most cases (69%), including at our Medical University of Graz, ethics in physiology is not incorporated into the physiology curriculum. Given this result, we suggest specific topics related to ethics and ethical considerations that could be integrated into the physiology curriculum. We present here a template example of a lecture “Teaching Ethics in Physiology” (structure, content, examples, and references), which was based on guidelines and case reports provided by experts in this area (e.g., Benos DJ. Ethics revisited. Adv Physiol Educ 25: 189–190, 2001). This lecture, which we are presently using in Graz, could be used as a base that could lead to greater awareness of important ethical issues in students at an early point in the educational process.
    Type of Medium: Online Resource
    ISSN: 1043-4046 , 1522-1229
    URL: Article
    DOI: 10.1152/advan.00010.2012
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2012
    detail.hit.zdb_id: 1477338-7
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  • 6
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    Online Resource
    Coagulation changes induced by lower-body negative pressure in men and women
    American Physiological Society ; 2019
    In:  Journal of Applied Physiology Vol. 126, No. 5 ( 2019-05-01), p. 1214-1222
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 126, No. 5 ( 2019-05-01), p. 1214-1222
    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.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/japplphysiol.00940.2018
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2019
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
    Location Call Number Limitation Availability
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  • 7
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    Online Resource
    Cardiovascular effects of air pollution: current evidence from animal and human studies
    American Physiological Society ; 2021
    In:  American Journal of Physiology-Heart and Circulatory Physiology Vol. 320, No. 4 ( 2021-04-01), p. H1417-H1439
    Details
    In: American Journal of Physiology-Heart and Circulatory Physiology, American Physiological Society, Vol. 320, No. 4 ( 2021-04-01), p. H1417-H1439
    Abstract: Air pollution is a global health concern. Particulate matter (PM) 2.5 , a component of ambient air pollution, has been identified by the World Health Organization as one of the pollutants that poses the greatest threat to public health. Cardiovascular health effects have been extensively documented, and these effects are still being researched to provide an overview of recent literature regarding air pollution-associated cardiovascular morbidity and mortality in humans. Additionally, potential mechanisms through which air pollutants affect the cardiovascular system are discussed based on human and additional animal studies. We used the strategy of a narrative review to summarize the scientific literature of studies that were published in the past 7 yr. Searches were carried out on PubMed and Web of Science using predefined search queries. We obtained an initial set of 800 publications that were filtered to 78 publications that were relevant to include in this review. Analysis of the literature showed significant associations between air pollution, especially PM 2.5 , and the risk of elevated blood pressure (BP), acute coronary syndrome, myocardial infarction (MI), cardiac arrhythmia, and heart failure (HF). Prominent mechanisms that underlie the adverse effects of air pollution include oxidative stress, systemic inflammation, endothelial dysfunction, autonomic imbalance, and thrombogenicity. The current review underscores the relevance of air pollution as a global health concern that affects cardiovascular health. More rigorous standards are needed to reduce the cardiovascular disease burden imposed by air pollution. Continued research on the health impact of air pollution is needed to provide further insight.
    Type of Medium: Online Resource
    ISSN: 0363-6135 , 1522-1539
    URL: Article
    DOI: 10.1152/ajpheart.00706.2020
    RVK:
    WA 15000
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2021
    detail.hit.zdb_id: 1477308-9
    SSG: 12
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  • 8
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    Online Resource
    Developing a “dry lab” activity using lower body negative pressure to teach physiology
    American Physiological Society ; 2021
    In:  Advances in Physiology Education Vol. 45, No. 3 ( 2021-09-01), p. 445-453
    Details
    In: Advances in Physiology Education, American Physiological Society, Vol. 45, No. 3 ( 2021-09-01), p. 445-453
    Abstract: In this paper we assessed how lower body negative pressure (LBNP) can be used to teach students the physiological effects of central hypovolemia in the absence of the LBNP and/or a medical monitor using a “dry lab” activity using LBNP data that have been previously collected. This activity was performed using published LBNP papers, with which students could explore LBNP as an important tool to study physiological responses to central hypovolemia as well as consider issues in performing an LBNP experiment and interpreting experimental results. The activity was performed at the All India Institute of Medical Sciences, New Delhi, with 31 graduate students and 4 teachers of physiology. Both students and teachers were provided with a set of questionnaires that inquired about aspects related to the structure of the activity and how this activity integrated research and knowledge, as well as aspects related to motivation of the students and teachers to perform the activity. Our results from student and teacher surveys suggest that a “dry lab” activity using LBNP to teach physiology can be an important tool to expose students to the basics of systems physiology as well as to provide useful insights into how research is performed. Providing insight into research includes formulating a research question and then designing (including taking into account confounding variables), implementing, conducting, and interpreting research studies. Finally, developing such an activity using LBNP can also serve as a basis for developing research capacities and interests of students even early in their medical studies.
    Type of Medium: Online Resource
    ISSN: 1043-4046 , 1522-1229
    URL: Article
    DOI: 10.1152/advan.00123.2020
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2021
    detail.hit.zdb_id: 1477338-7
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  • 9
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    Online Resource
    Bridging different perspectives of the physiological and mathematical disciplines
    American Physiological Society ; 2012
    In:  Advances in Physiology Education Vol. 36, No. 4 ( 2012-12), p. 265-274
    Details
    In: Advances in Physiology Education, American Physiological Society, Vol. 36, No. 4 ( 2012-12), p. 265-274
    Abstract: The goal of this report is to discuss educational approaches for bridging the different perspectives of the physiological and mathematical disciplines. These approaches can enhance the learning experience for physiology, medical, and mathematics students and simultaneously act to stimulate mathematical/physiological/clinical interdisciplinary research. While physiology education incorporates mathematics, via equations and formulas, it does not typically provide a foundation for interdisciplinary research linking mathematics and physiology. Here, we provide insights and ideas derived from interdisciplinary seminars involving mathematicians and physiologists that have been conducted over the last decade. The approaches described here can be used as templates for giving physiology and medical students insights into how sophisticated tools from mathematics can be applied and how the disciplines of mathematics and physiology can be integrated in research, thereby fostering a foundation for interdisciplinary collaboration. These templates are equally applicable to linking mathematical methods with other life and health sciences in the educational process.
    Type of Medium: Online Resource
    ISSN: 1043-4046 , 1522-1229
    URL: Article
    DOI: 10.1152/advan.00074.2012
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2012
    detail.hit.zdb_id: 1477338-7
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  • 10
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    Online Resource
    The relationship between brain cortical activity and brain oxygenation in the prefrontal cortex during hypergravity exposure
    American Physiological Society ; 2013
    In:  Journal of Applied Physiology Vol. 114, No. 7 ( 2013-04-01), p. 905-910
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 114, No. 7 ( 2013-04-01), p. 905-910
    Abstract: Artificial gravity has been proposed as a method to counteract the physiological deconditioning of long-duration spaceflight; however, the effects of hypergravity on the central nervous system has had little study. The study aims to investigate whether there is a relationship between prefrontal cortex brain activity and prefrontal cortex oxygenation during exposure to hypergravity. Twelve healthy participants were selected to undergo hypergravity exposure aboard a short-arm human centrifuge. Participants were exposed to hypergravity in the +Gz axis, starting from 0.6 +Gz for women, and 0.8 +Gz for men, and gradually increasing by 0.1 +Gz until the participant showed signs of syncope. Brain cortical activity was measured using electroencephalography (EEG) and localized to the prefrontal cortex using standard low-resolution brain electromagnetic tomography (LORETA). Prefrontal cortex oxygenation was measured using near-infrared spectroscopy (NIRS). A significant increase in prefrontal cortex activity ( P 〈 0.05) was observed during hypergravity exposure compared with baseline. Prefrontal cortex oxygenation was significantly decreased during hypergravity exposure, with a decrease in oxyhemoglobin levels ( P 〈 0.05) compared with baseline and an increase in deoxyhemoglobin levels ( P 〈 0.05) with increasing +Gz level. No significant correlation was found between prefrontal cortex activity and oxy-/deoxyhemoglobin. It is concluded that the increase in prefrontal cortex activity observed during hypergravity was most likely not the result of increased +Gz values resulting in a decreased oxygenation produced through hypergravity exposure. No significant relationship between prefrontal cortex activity and oxygenation measured by NIRS concludes that brain activity during exposure to hypergravity may be difficult to measure using NIRS. Instead, the increase in prefrontal cortex activity might be attributable to psychological stress, which could pose a problem for the use of a short-arm human centrifuge as a countermeasure.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/japplphysiol.01426.2012
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2013
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
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