Peter Gauger - Academia.edu (original) (raw)

Papers by Peter Gauger

Fragestellung: Teilbelastung ist Bestandteil vieler Therapieschemata in Orthopädie und Unfallchir... more Fragestellung: Teilbelastung ist Bestandteil vieler Therapieschemata in Orthopädie und Unfallchirurgie. Es ist jedoch unklar welche Deformierung die verschiedenen Arten der Teilbelastung am Knochen bewirken. Ziel dieser experimentellen Studie war es, die Verformung der menschlichen Tibia in vivo[zum vollständigen Text gelangen Sie über die oben angegebene URL]

Einleitung: Veranderungen der Kontraktilitat des Herzens in Mikrogravitation sind nicht vollstand... more Einleitung: Veranderungen der Kontraktilitat des Herzens in Mikrogravitation sind nicht vollstandig verstanden (1). Die Bestimmung systolischer Zeitintervalle (STI) bietet eine nichtinvasive und sichere Methode fur die Untersuchung der Myokardfunktion. Aktuell existiert keine optimale Moglichkeit zur STI-Erfassung im Weltraum. Fragestellung: Konstruktion und Bau eines Prototyps zur mobilen, wissenschaftlichen Aufzeichnung von STI auf Grundlage von kostengunstigen und frei verfugbaren Plattformen wie Arduino, BeagleBone oder Raspberry-Pi. Methodik: Auffinden der zweckdienlichsten Plattform. Bau des Prototyps auf Grundlage eines Raspberry-Pi und verfugbaren Modulen fur EKG und Photoplethysmographie. Implementierung von Phonokardiographie. Entwicklung notwendiger Software. Technische Tests an Probanden. Ergebnisse: Frei verfugbare Plattformen konnen zur kostengunstigen Konstruktion eines mobilen Gerates zur Bestimmung von STI dienen. Ein Einsatz des Prototyps im Rahmen von wissenschaft...

Einleitung: In Parabelflugen kommt es auf Grund der Ubergange zwischen doppelter Schwerkraft und ... more Einleitung: In Parabelflugen kommt es auf Grund der Ubergange zwischen doppelter Schwerkraft und Schwerelosigkeit zu Volumenverschiebungen innerhalb des Gefassystems und somit auch zu einer veranderten Pumpleistung des Herzens. Die Systolischen Zeitintervalle bieten eine nichtinvasive Variante zur Beurteilung der kardialen Funktion. Fragestellung: Wie verhalten sich die Systolischen Zeitintervalle im Parabelflug? Konnen Sie die Volumenverschiebungen widerspiegeln? Methodik: Zur Aufzeichnung der Systolischen Zeitintervalle wurde eine Kombination aus EKG, Phonokardiographie und kontinuierlichem Fingerblutdruck verwendet. Funf Probanden nahmen an dem Experiment teil und verbrachten jeweils 15 Parabeln liegender und 15 Parabeln stehender Korperposition. Ergebnisse: Erste Ergebnisse zeigen, dass die elektromechanische Systole nach einem stehenden Ubergang in Schwerelosigkeit deutlich kurzer ist als nach einem Liegenden. Auch das Verhaltnis zwischen Praejektionsperiode und linksventrikula...

Journal of the American Heart Association, 2020

Background Hypergravity may promote human hemostasis thereby increasing thrombotic risk. Future t... more Background Hypergravity may promote human hemostasis thereby increasing thrombotic risk. Future touristic suborbital spaceflight will expose older individuals with chronic medical conditions, who are at much higher thromboembolic risk compared with professional astronauts, to hypergravity. Therefore, we tested the impact of hypergravity on hemostasis in healthy volunteers undergoing centrifugation. Methods and Results We studied 20 healthy seated men before and after 15 minutes under 3 Gz hypergravity on a long‐arm centrifuge. We obtained blood samples for hemostasis testing before, immediately after, and 30 minutes after centrifugation. Tests included viscoelastic thromboelastometry, platelet impedance aggregometry, endothelial activation markers, blood rheology testing, microparticle analyses, and clotting factor analysis. Exposure to hypergravity reduced plasma volume by 12.5% ( P =0.002) and increased the red blood cell aggregation index ( P <0.05). With hypergravity, thrombe...

Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2013

The transthoracic impedance cardiogram (ICG) and the acceleration ballistocardiogram (BCG) measur... more The transthoracic impedance cardiogram (ICG) and the acceleration ballistocardiogram (BCG) measured close to the center of mass of the human body are generated by changes of blood distribution. The transthoracic ICG is an integrated signal covering the whole thorax and spatial resolution is poor. Comparison between both signals can be used to elucidate the source of the ICG signal. We recorded the ECG, ICG, and BCG simultaneously in healthy subjects under resting and microgravity conditions during parabolic flights. The time interval between the R-peak of the ECG and the maximum of the ICG (R-dZ/dtmax) and the time interval between the R-peak of the ECG and the I-peak in the BCG (R-I) differed significantly (p<0.0001). The I-peak in the BCG always occurred earlier during systole than dZ/dtmax. The delay of dZ/dtmax ranged between 23 and 28 ms at rest and was lowest under microgravity conditions (12 ± 4 ms, p<0.02). Our results suggest that both signals have different sources. ...

Wie und durch welche physiologischen Wege Isolation das Verhalten von Blutdruck beeinflusst, war ... more Wie und durch welche physiologischen Wege Isolation das Verhalten von Blutdruck beeinflusst, war unsere Fragestellung für MARS 520. Nach gegenwärtigem Wissenstand wird langfristige Blutdruckregulation hauptsächlich durch den Wasser-Elektrolyt-Haushalt betrieben, aber auch Umwelt-, psychosoziale und stressbedingte Einflüsse modulieren das Blutdruckverhalten. Langzeit-Isolationsstudien bieten dank des Wegfalls äußerlicher Reize eine außerordentliche Gelegenheit, das Zusammenspiel physiologischer Blutdruckdeterminanten unter kontrollierten Bedingungen zu untersuchen. Bei den sechs Probanden [Mittelwert (SD): 31.8 (4.5) Jahre; 80.3 (7.8) kg KG] der MARS520-Studie wurden insgesamt sechzehn 24h–Blutdruckmessungen durchgeführt (Ambulante Blutdruck (ABD) – Überwachungsmonitore, Spacelabs GmbH): einmal vor, 11 Mal während und 4 Mal nach 520 Tagen Isolation in der MARS 500 Anlage, IBMP, Moskau. Während der ersten 250 Tage wurde die diätetische Kochsalzzufuhr auf 12g, 9g, und 6g für jeweils 6 ...

Symposium on Spatial User Interaction, 2020

Considering human capability for spatial orientation and navigation, the visualization used to su... more Considering human capability for spatial orientation and navigation, the visualization used to support the localization of off-screen targets inevitably influences the visual-spatial processing that relies on two frameworks. So far it is not proven which frame of reference, egocentric or exocentric, contributes most to efficient viewpoint guidance in a head-mounted Augmented Reality environment. This could be justified by the lack of objectively assessing the allocation of attention and mental workload demanded by the guidance method. This paper presents a user study investigating the effect of egocentric and exocentric viewpoint guidance on visual attention and mental workload. In parallel to a localization task, participants had to complete a divided attention task using the oddball paradigm. During task fulfilment, the heart rate variability was measured to determine the physiological stress level. The objective assessment of mental workload was supplemented by subjective ratings using the NASA TLX. The results show that egocentric viewpoint guidance leads to most efficient target cueing in terms of faster localization, higher accuracy and slower self-reported workload. In addition, egocentric target cueing causes a slight decrease in physiological stress and enables faster recognition of simultaneous events, although visual attention seemed to be covertly oriented.

Einleitung: Ein schneller Aufstieg in grose Hohe fuhrt in den ersten 2-5 Tagen zur akuten Hohenkr... more Einleitung: Ein schneller Aufstieg in grose Hohe fuhrt in den ersten 2-5 Tagen zur akuten Hohenkrankheit (AHK), deren Mechanismen nur unzureichend verstanden sind. In Tierund klinischen Studien kam es durch Hypoxie und Inflammation zum Zusammenbruch der Gefasbarriere bestehend aus einer endothelialen Mikroschicht aus Proteoglykanen (Glycocalyx). Daraus folgte eine erhohte Gefaspermeabilitat mit Odembildung und Proteinurie. Die Glycocalyx erholte sich in einer dieser Studien innerhalb von 5 Tagen und zeigte damit eine vergleichbare zeitliche Dynamik wie die AHK. Im Rahmen der AHK ist das Verhalten der endothelialen Glycocalyx allerdings bisher nicht erforscht worden. Hypothesen: Eine 6-tagige Hohenexposition fuhrt zu Hypoxamie, Albuminurie, Bildung peripherer Odeme und einer Erhohung der Blutkonzentration der (endothelialen) Glycocalyxfragmente Syndecan-1, Heparansulfat, und Hyaluronan und des Inflammationsmarkers CRP im Vergleich zu den Ausgangswerten in Meereshohe. Methodik: Aktive...

Clinical Autonomic Research, 2020

Unfortunately, the first name of 8th author was incorrectly published in the original publication.

Since decades brief periods of microgravity have been generated using slightly modified commercia... more Since decades brief periods of microgravity have been generated using slightly modified commercial airliners during parabolic trajectory flights in the troposphere. These flights allow both cost-efficient scientific research under space analog conditions and astronaut training. Nowadays parabolic flights are also more and more used for commercial purposes and their number will further increase in the near future. Thus flight surgeons will have to deal incrementally with customers of very different age levels and health status wishing to pass their parabolic flight medical certificate.Therefore this survey focuses on the human cardiovascular system (HCS) in parabolic flights. The authors describe the particular behavior of the HCS during parabolic flights by reviewing the literature and stating their own research results thereby bringing together basic physiological research with applied flight medicine. It becomes clear that the impact of parabolic flights on HCS is closely correlat...

Einleitung: Die Bedingungen eines Raumfluges beeinflussen die Hamostase. Ebenso scheinen thromboz... more Einleitung: Die Bedingungen eines Raumfluges beeinflussen die Hamostase. Ebenso scheinen thrombozytare Mikropartikel (platelet-derived microparticle, PMP) die menschliche Blutgerinnung zu verandern. Es ist unklar, inwieweit erhohte Schwerkrafte einen Einfluss auf thrombozytare Mikropartikel ausuben. Fragestellung: Unter Berucksichtigung der aktuellen Studienlage ist es unklar, wie sich veranderte Gravitationskrafte auf die menschliche Hamostase auswirken. Hinweise aus Studien an Tiermodellen, Zellkulturstudien und Fallberichten deuten jedoch darauf hin, dass erhohte Schwerkraft das menschliche Gerinnungssystem im Sinne einer Hyperkoagulabilitat aktiviert. In diesem Zusammenhang scheinen PMP einen prokoagulatorischen Effekt zu vermitteln. Inwieweit sich erhohte g-Krafte auf PMP auswirken, war die Fragestellung der vorliegenden Studie. Methodik: Es wurden Messungen auf der humanen Langarm-Zentrifuge des DLR in Koln durchgefuhrt. Hierbei wurde an 20 gesunden Probanden der Einfluss eine...

The American Journal of Medicine, 2020

Clinical Autonomic Research, 2020

Journal of Clinical Medicine, 2019

We hypothesized that sympathetic baroreflex mediated uncoupling between neural sympathetic discha... more We hypothesized that sympathetic baroreflex mediated uncoupling between neural sympathetic discharge pattern and arterial pressure (AP) fluctuations at 0.1 Hz during baroreceptor unloading might promote orthostatic pre-syncope. Ten volunteers (32 ± 6 years) underwent electrocardiogram, beat-to-beat AP, respiratory activity and muscle sympathetic nerve activity (MSNA) recordings while supine (REST) and during 80° head-up tilt (HUT) followed by -10 mmHg stepwise increase of lower body negative pressure until pre-syncope. Cardiac and sympathetic baroreflex sensitivity were quantified. Spectrum analysis of systolic and diastolic AP (SAP and DAP) and calibrated MSNA (cMSNA) variability assessed the low frequency fluctuations (LF, ~0.1 Hz) of SAP, DAP and cMSNA variability. The squared coherence function (K2) quantified the coupling between cMSNA and DAP in the LF band. Analyses were performed while supine, during asymptomatic HUT (T1) and at pre-syncope onset (T2). During T2 we found tha...

Frontiers in Physiology, 2019

Orthostatic intolerance commonly occurs after prolonged bed rest, thus increasing the risk of syn... more Orthostatic intolerance commonly occurs after prolonged bed rest, thus increasing the risk of syncope and falls. Baroreflex-mediated adjustments of heart rate and sympathetic vasomotor activity (muscle sympathetic nerve activity-MSNA) are crucial for orthostatic tolerance. We hypothesized that prolonged bed rest deconditioning alters overall baroreceptor functioning, thereby reducing orthostatic tolerance in healthy volunteers. As part of the European Space Agency Medium-term Bed Rest protocol, 10 volunteers were studied before and after 21 days of −6° head down bed rest (HDBR). In both conditions, subjects underwent ECG, beat-by-beat blood pressure, respiratory activity, and MSNA recordings while supine (REST) and during a 15-min 80° head-up tilt (TILT) followed by a 3-min −10 mmHg stepwise increase of lower body negative pressure to pre-syncope. Cardiac baroreflex sensitivity (cBRS) was obtained in the time (sequence method) and frequency domain (spectrum and crossspectrum analyses of RR interval and systolic arterial pressure-SAP, variability). Baroreceptor modulation of sympathetic discharge activity to the vessels (sBRS) was estimated by the slope of the regression line between the percentage of MSNA burst occurrence and diastolic arterial pressure. Orthostatic tolerance significantly decreased after HDBR (12 ± 0.6 min) compared to before (21 ± 0.6 min). While supine, heart rate, SAP, and cBRS were unchanged before and after HDBR, sBRS gain was slightly depressed after than before HDBR (sBRS: −6.0 ± 1.1 versus −2.9 ± 1.5 burst% × mmHg −1 , respectively). During TILT, HR was higher after than before HDBR (116 ± 4 b/min versus 100 ± 4 b/min, respectively), SAP was unmodified in both conditions, and cBRS indexes were lower after HDBR (α index: 3.4 ± 0.7 ms/mmHg; BRS SEQ 4.0 ± 1.0) than before (α index: 6.4 ± 1.0 ms/mmHg; BRS SEQ 6.8 ± 1.2). sBRS gain was significantly more depressed after HDBR than before (sBRS: −2.3 ± 0.7 versus −4.4 ± 0.4 burst% × mmHg −1 , respectively). Our findings suggest that Barbic et al.

Frontiers in Physiology, 2019

Recent studies are elucidating the interrelation between sleep, cranial perfusion, and cerebrospi... more Recent studies are elucidating the interrelation between sleep, cranial perfusion, and cerebrospinal fluid (CSF) circulation. Head down tilt (HDT) as a simulation of microgravity reduces cranial perfusion. Therefore, our aim was to assess whether HDT is affecting sleep (clinicaltrials.gov; identifier NCT 02976168). 11 male subjects were recruited for a cross-over designed study. Each subject participated in two campaigns each comprising 3 days and 2 nights. Intervention started on the second campaign day and consisted of maintenance of horizontal position or −12 • HDT for 21 h. Ultrasound measurements were performed before, at the beginning and the end of intervention. Polysomnographic measurements were assessed in the second night which was either spent in horizontal posture or at −12 • HDT. Endpoints were sleep efficiency, sleep onset latency, number of sleep state changes and arousals, percentages of N3, REM, light sleep stages and subjective sleep parameters. N3 and REM sleep reduced by 25.6 and 19.1 min, respectively (P = 0.002, g =-0.898; P = 0.035, g =-0.634) during −12 • HDT. Light sleep (N1/2) increased by 33.0 min at −12 • HDT (P = 0.002, g = 1.078). On a scale from 1 to 9 subjective sleep quality deteriorated by 1.3 points during −12 • HDT (P = 0.047, g =-0.968). Ultrasonic measurement of the venous system showed a significant increase of the minimum (P = 0.009, P < 0.001) and maximum (P = 0.004, P = 0.002) cross-sectional area of the internal jugular vein at −12 • HDT. The minimum cross-sectional area of the external jugular vein differed significantly between conditions over time (P = 0.001) whereas frontal skin tissue thickness was not significantly different between conditions (P = 0.077, P = 0.811). Data suggests venous congestion at −12 • HDT. Since subjects felt comfortable with lying in −12 • HDT under our experimental conditions, this posture only moderately deteriorates sleep. Obviously, the human body can almost compensate the several fold effects of gravity in HDT posture like an affected CSF circulation, airway obstruction, unusual patterns of propioception and effects on the cardiovascular system.

Clinical autonomic research : official journal of the Clinical Autonomic Research Society, 2018

Since manned missions to the Moon and Mars are planned, we conducted active standing tests with l... more Since manned missions to the Moon and Mars are planned, we conducted active standing tests with lunar, Martian, terrestrial, and 1.8 loads of inertial resistance (+G) modeled through defined parabolic flight maneuvers. We hypothesized that the cardiovascular response to active standing is proportional to the +G load. During partial-+G parabolic flights, 14 healthy test subjects performed active stand-up maneuvers under 1 +G, lunar (0.16 +G), Martian (0.38 +G), and hyper inertial resistance (1.8 +G) while heart rate and finger blood pressure were continuously monitored. We quantified amplitudes and timing of orthostatic response immediately following standing up. The maximum early heart rate increase was 21 (SD ± 10) bpm with lunar, 23 (± 11) bpm with Martian, 34 (± 17) bpm with terrestrial +G, and 40 (± 11) bpm hyper +G. The time to maximum heart rate increased gradually with increasing loads of inertial resistance. The transient blood pressure reduction was most pronounced with hyp...

Injury, 2016

Introduction: Partial weight bearing is part of treatment schemes in orthopedic surgery and traum... more Introduction: Partial weight bearing is part of treatment schemes in orthopedic surgery and traumatology. The aim of the present study was to explore to what degree ground reaction forces during partial weight bearing of the lower leg are related to given instructions and to tibia deformation. Materials and methods: Tibia deformation (torsion, medio-lateral and anterio-posterior bending) was measured for rear foot and forefoot loading, 10 kg, 20 kg and half body weight instructions compared to full loading in five healthy male subjects using the "Optical Segment Tracking" approach, a motioncapturing based method that uses monocortically fixed bone screws. Results: 1. Ground reaction force was a good indicator of tibia deformation. 2. Participants significantly under-loaded during half-body weight instructions (P < 0.001) while they overloaded when loading the forefoot only. 3. Partial-loading instructions led to a highly significant and systematic reduction in peak ground reaction force (GRFpk) in all three types of tibia deformation with substantial variation between measurements. 4. Forefoot usage was associated with significant, albeit moderate increases in GRFpk (P = 0.0031), in AP-bending (P = 0.0027) and in torsion (P < 0.001), compared to rear foot loading. Discussion: These findings result in the following clinical "lessons learned": 1. GRF is a good reflection of loading-induced deformation of the tibia. 2. GRFs are hard to control by subjects/patients. 3. The expectation that forefoot-loading results in larger tibia deformation could not be confirmed in our study. 4. When aiming at a reduction in tibia deformation, rear-foot loading is more preferable than forefoot loading.

Fragestellung: Teilbelastung ist Bestandteil vieler Therapieschemata in Orthopädie und Unfallchir... more Fragestellung: Teilbelastung ist Bestandteil vieler Therapieschemata in Orthopädie und Unfallchirurgie. Es ist jedoch unklar welche Deformierung die verschiedenen Arten der Teilbelastung am Knochen bewirken. Ziel dieser experimentellen Studie war es, die Verformung der menschlichen Tibia in vivo[zum vollständigen Text gelangen Sie über die oben angegebene URL]

Einleitung: Veranderungen der Kontraktilitat des Herzens in Mikrogravitation sind nicht vollstand... more Einleitung: Veranderungen der Kontraktilitat des Herzens in Mikrogravitation sind nicht vollstandig verstanden (1). Die Bestimmung systolischer Zeitintervalle (STI) bietet eine nichtinvasive und sichere Methode fur die Untersuchung der Myokardfunktion. Aktuell existiert keine optimale Moglichkeit zur STI-Erfassung im Weltraum. Fragestellung: Konstruktion und Bau eines Prototyps zur mobilen, wissenschaftlichen Aufzeichnung von STI auf Grundlage von kostengunstigen und frei verfugbaren Plattformen wie Arduino, BeagleBone oder Raspberry-Pi. Methodik: Auffinden der zweckdienlichsten Plattform. Bau des Prototyps auf Grundlage eines Raspberry-Pi und verfugbaren Modulen fur EKG und Photoplethysmographie. Implementierung von Phonokardiographie. Entwicklung notwendiger Software. Technische Tests an Probanden. Ergebnisse: Frei verfugbare Plattformen konnen zur kostengunstigen Konstruktion eines mobilen Gerates zur Bestimmung von STI dienen. Ein Einsatz des Prototyps im Rahmen von wissenschaft...

Einleitung: In Parabelflugen kommt es auf Grund der Ubergange zwischen doppelter Schwerkraft und ... more Einleitung: In Parabelflugen kommt es auf Grund der Ubergange zwischen doppelter Schwerkraft und Schwerelosigkeit zu Volumenverschiebungen innerhalb des Gefassystems und somit auch zu einer veranderten Pumpleistung des Herzens. Die Systolischen Zeitintervalle bieten eine nichtinvasive Variante zur Beurteilung der kardialen Funktion. Fragestellung: Wie verhalten sich die Systolischen Zeitintervalle im Parabelflug? Konnen Sie die Volumenverschiebungen widerspiegeln? Methodik: Zur Aufzeichnung der Systolischen Zeitintervalle wurde eine Kombination aus EKG, Phonokardiographie und kontinuierlichem Fingerblutdruck verwendet. Funf Probanden nahmen an dem Experiment teil und verbrachten jeweils 15 Parabeln liegender und 15 Parabeln stehender Korperposition. Ergebnisse: Erste Ergebnisse zeigen, dass die elektromechanische Systole nach einem stehenden Ubergang in Schwerelosigkeit deutlich kurzer ist als nach einem Liegenden. Auch das Verhaltnis zwischen Praejektionsperiode und linksventrikula...

Journal of the American Heart Association, 2020

Background Hypergravity may promote human hemostasis thereby increasing thrombotic risk. Future t... more Background Hypergravity may promote human hemostasis thereby increasing thrombotic risk. Future touristic suborbital spaceflight will expose older individuals with chronic medical conditions, who are at much higher thromboembolic risk compared with professional astronauts, to hypergravity. Therefore, we tested the impact of hypergravity on hemostasis in healthy volunteers undergoing centrifugation. Methods and Results We studied 20 healthy seated men before and after 15 minutes under 3 Gz hypergravity on a long‐arm centrifuge. We obtained blood samples for hemostasis testing before, immediately after, and 30 minutes after centrifugation. Tests included viscoelastic thromboelastometry, platelet impedance aggregometry, endothelial activation markers, blood rheology testing, microparticle analyses, and clotting factor analysis. Exposure to hypergravity reduced plasma volume by 12.5% ( P =0.002) and increased the red blood cell aggregation index ( P <0.05). With hypergravity, thrombe...

Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2013

The transthoracic impedance cardiogram (ICG) and the acceleration ballistocardiogram (BCG) measur... more The transthoracic impedance cardiogram (ICG) and the acceleration ballistocardiogram (BCG) measured close to the center of mass of the human body are generated by changes of blood distribution. The transthoracic ICG is an integrated signal covering the whole thorax and spatial resolution is poor. Comparison between both signals can be used to elucidate the source of the ICG signal. We recorded the ECG, ICG, and BCG simultaneously in healthy subjects under resting and microgravity conditions during parabolic flights. The time interval between the R-peak of the ECG and the maximum of the ICG (R-dZ/dtmax) and the time interval between the R-peak of the ECG and the I-peak in the BCG (R-I) differed significantly (p<0.0001). The I-peak in the BCG always occurred earlier during systole than dZ/dtmax. The delay of dZ/dtmax ranged between 23 and 28 ms at rest and was lowest under microgravity conditions (12 ± 4 ms, p<0.02). Our results suggest that both signals have different sources. ...

Wie und durch welche physiologischen Wege Isolation das Verhalten von Blutdruck beeinflusst, war ... more Wie und durch welche physiologischen Wege Isolation das Verhalten von Blutdruck beeinflusst, war unsere Fragestellung für MARS 520. Nach gegenwärtigem Wissenstand wird langfristige Blutdruckregulation hauptsächlich durch den Wasser-Elektrolyt-Haushalt betrieben, aber auch Umwelt-, psychosoziale und stressbedingte Einflüsse modulieren das Blutdruckverhalten. Langzeit-Isolationsstudien bieten dank des Wegfalls äußerlicher Reize eine außerordentliche Gelegenheit, das Zusammenspiel physiologischer Blutdruckdeterminanten unter kontrollierten Bedingungen zu untersuchen. Bei den sechs Probanden [Mittelwert (SD): 31.8 (4.5) Jahre; 80.3 (7.8) kg KG] der MARS520-Studie wurden insgesamt sechzehn 24h–Blutdruckmessungen durchgeführt (Ambulante Blutdruck (ABD) – Überwachungsmonitore, Spacelabs GmbH): einmal vor, 11 Mal während und 4 Mal nach 520 Tagen Isolation in der MARS 500 Anlage, IBMP, Moskau. Während der ersten 250 Tage wurde die diätetische Kochsalzzufuhr auf 12g, 9g, und 6g für jeweils 6 ...

Symposium on Spatial User Interaction, 2020

Considering human capability for spatial orientation and navigation, the visualization used to su... more Considering human capability for spatial orientation and navigation, the visualization used to support the localization of off-screen targets inevitably influences the visual-spatial processing that relies on two frameworks. So far it is not proven which frame of reference, egocentric or exocentric, contributes most to efficient viewpoint guidance in a head-mounted Augmented Reality environment. This could be justified by the lack of objectively assessing the allocation of attention and mental workload demanded by the guidance method. This paper presents a user study investigating the effect of egocentric and exocentric viewpoint guidance on visual attention and mental workload. In parallel to a localization task, participants had to complete a divided attention task using the oddball paradigm. During task fulfilment, the heart rate variability was measured to determine the physiological stress level. The objective assessment of mental workload was supplemented by subjective ratings using the NASA TLX. The results show that egocentric viewpoint guidance leads to most efficient target cueing in terms of faster localization, higher accuracy and slower self-reported workload. In addition, egocentric target cueing causes a slight decrease in physiological stress and enables faster recognition of simultaneous events, although visual attention seemed to be covertly oriented.

Einleitung: Ein schneller Aufstieg in grose Hohe fuhrt in den ersten 2-5 Tagen zur akuten Hohenkr... more Einleitung: Ein schneller Aufstieg in grose Hohe fuhrt in den ersten 2-5 Tagen zur akuten Hohenkrankheit (AHK), deren Mechanismen nur unzureichend verstanden sind. In Tierund klinischen Studien kam es durch Hypoxie und Inflammation zum Zusammenbruch der Gefasbarriere bestehend aus einer endothelialen Mikroschicht aus Proteoglykanen (Glycocalyx). Daraus folgte eine erhohte Gefaspermeabilitat mit Odembildung und Proteinurie. Die Glycocalyx erholte sich in einer dieser Studien innerhalb von 5 Tagen und zeigte damit eine vergleichbare zeitliche Dynamik wie die AHK. Im Rahmen der AHK ist das Verhalten der endothelialen Glycocalyx allerdings bisher nicht erforscht worden. Hypothesen: Eine 6-tagige Hohenexposition fuhrt zu Hypoxamie, Albuminurie, Bildung peripherer Odeme und einer Erhohung der Blutkonzentration der (endothelialen) Glycocalyxfragmente Syndecan-1, Heparansulfat, und Hyaluronan und des Inflammationsmarkers CRP im Vergleich zu den Ausgangswerten in Meereshohe. Methodik: Aktive...

Clinical Autonomic Research, 2020

Unfortunately, the first name of 8th author was incorrectly published in the original publication.

Since decades brief periods of microgravity have been generated using slightly modified commercia... more Since decades brief periods of microgravity have been generated using slightly modified commercial airliners during parabolic trajectory flights in the troposphere. These flights allow both cost-efficient scientific research under space analog conditions and astronaut training. Nowadays parabolic flights are also more and more used for commercial purposes and their number will further increase in the near future. Thus flight surgeons will have to deal incrementally with customers of very different age levels and health status wishing to pass their parabolic flight medical certificate.Therefore this survey focuses on the human cardiovascular system (HCS) in parabolic flights. The authors describe the particular behavior of the HCS during parabolic flights by reviewing the literature and stating their own research results thereby bringing together basic physiological research with applied flight medicine. It becomes clear that the impact of parabolic flights on HCS is closely correlat...

Einleitung: Die Bedingungen eines Raumfluges beeinflussen die Hamostase. Ebenso scheinen thromboz... more Einleitung: Die Bedingungen eines Raumfluges beeinflussen die Hamostase. Ebenso scheinen thrombozytare Mikropartikel (platelet-derived microparticle, PMP) die menschliche Blutgerinnung zu verandern. Es ist unklar, inwieweit erhohte Schwerkrafte einen Einfluss auf thrombozytare Mikropartikel ausuben. Fragestellung: Unter Berucksichtigung der aktuellen Studienlage ist es unklar, wie sich veranderte Gravitationskrafte auf die menschliche Hamostase auswirken. Hinweise aus Studien an Tiermodellen, Zellkulturstudien und Fallberichten deuten jedoch darauf hin, dass erhohte Schwerkraft das menschliche Gerinnungssystem im Sinne einer Hyperkoagulabilitat aktiviert. In diesem Zusammenhang scheinen PMP einen prokoagulatorischen Effekt zu vermitteln. Inwieweit sich erhohte g-Krafte auf PMP auswirken, war die Fragestellung der vorliegenden Studie. Methodik: Es wurden Messungen auf der humanen Langarm-Zentrifuge des DLR in Koln durchgefuhrt. Hierbei wurde an 20 gesunden Probanden der Einfluss eine...

The American Journal of Medicine, 2020

Clinical Autonomic Research, 2020

Journal of Clinical Medicine, 2019

We hypothesized that sympathetic baroreflex mediated uncoupling between neural sympathetic discha... more We hypothesized that sympathetic baroreflex mediated uncoupling between neural sympathetic discharge pattern and arterial pressure (AP) fluctuations at 0.1 Hz during baroreceptor unloading might promote orthostatic pre-syncope. Ten volunteers (32 ± 6 years) underwent electrocardiogram, beat-to-beat AP, respiratory activity and muscle sympathetic nerve activity (MSNA) recordings while supine (REST) and during 80° head-up tilt (HUT) followed by -10 mmHg stepwise increase of lower body negative pressure until pre-syncope. Cardiac and sympathetic baroreflex sensitivity were quantified. Spectrum analysis of systolic and diastolic AP (SAP and DAP) and calibrated MSNA (cMSNA) variability assessed the low frequency fluctuations (LF, ~0.1 Hz) of SAP, DAP and cMSNA variability. The squared coherence function (K2) quantified the coupling between cMSNA and DAP in the LF band. Analyses were performed while supine, during asymptomatic HUT (T1) and at pre-syncope onset (T2). During T2 we found tha...

Frontiers in Physiology, 2019

Orthostatic intolerance commonly occurs after prolonged bed rest, thus increasing the risk of syn... more Orthostatic intolerance commonly occurs after prolonged bed rest, thus increasing the risk of syncope and falls. Baroreflex-mediated adjustments of heart rate and sympathetic vasomotor activity (muscle sympathetic nerve activity-MSNA) are crucial for orthostatic tolerance. We hypothesized that prolonged bed rest deconditioning alters overall baroreceptor functioning, thereby reducing orthostatic tolerance in healthy volunteers. As part of the European Space Agency Medium-term Bed Rest protocol, 10 volunteers were studied before and after 21 days of −6° head down bed rest (HDBR). In both conditions, subjects underwent ECG, beat-by-beat blood pressure, respiratory activity, and MSNA recordings while supine (REST) and during a 15-min 80° head-up tilt (TILT) followed by a 3-min −10 mmHg stepwise increase of lower body negative pressure to pre-syncope. Cardiac baroreflex sensitivity (cBRS) was obtained in the time (sequence method) and frequency domain (spectrum and crossspectrum analyses of RR interval and systolic arterial pressure-SAP, variability). Baroreceptor modulation of sympathetic discharge activity to the vessels (sBRS) was estimated by the slope of the regression line between the percentage of MSNA burst occurrence and diastolic arterial pressure. Orthostatic tolerance significantly decreased after HDBR (12 ± 0.6 min) compared to before (21 ± 0.6 min). While supine, heart rate, SAP, and cBRS were unchanged before and after HDBR, sBRS gain was slightly depressed after than before HDBR (sBRS: −6.0 ± 1.1 versus −2.9 ± 1.5 burst% × mmHg −1 , respectively). During TILT, HR was higher after than before HDBR (116 ± 4 b/min versus 100 ± 4 b/min, respectively), SAP was unmodified in both conditions, and cBRS indexes were lower after HDBR (α index: 3.4 ± 0.7 ms/mmHg; BRS SEQ 4.0 ± 1.0) than before (α index: 6.4 ± 1.0 ms/mmHg; BRS SEQ 6.8 ± 1.2). sBRS gain was significantly more depressed after HDBR than before (sBRS: −2.3 ± 0.7 versus −4.4 ± 0.4 burst% × mmHg −1 , respectively). Our findings suggest that Barbic et al.

Frontiers in Physiology, 2019

Recent studies are elucidating the interrelation between sleep, cranial perfusion, and cerebrospi... more Recent studies are elucidating the interrelation between sleep, cranial perfusion, and cerebrospinal fluid (CSF) circulation. Head down tilt (HDT) as a simulation of microgravity reduces cranial perfusion. Therefore, our aim was to assess whether HDT is affecting sleep (clinicaltrials.gov; identifier NCT 02976168). 11 male subjects were recruited for a cross-over designed study. Each subject participated in two campaigns each comprising 3 days and 2 nights. Intervention started on the second campaign day and consisted of maintenance of horizontal position or −12 • HDT for 21 h. Ultrasound measurements were performed before, at the beginning and the end of intervention. Polysomnographic measurements were assessed in the second night which was either spent in horizontal posture or at −12 • HDT. Endpoints were sleep efficiency, sleep onset latency, number of sleep state changes and arousals, percentages of N3, REM, light sleep stages and subjective sleep parameters. N3 and REM sleep reduced by 25.6 and 19.1 min, respectively (P = 0.002, g =-0.898; P = 0.035, g =-0.634) during −12 • HDT. Light sleep (N1/2) increased by 33.0 min at −12 • HDT (P = 0.002, g = 1.078). On a scale from 1 to 9 subjective sleep quality deteriorated by 1.3 points during −12 • HDT (P = 0.047, g =-0.968). Ultrasonic measurement of the venous system showed a significant increase of the minimum (P = 0.009, P < 0.001) and maximum (P = 0.004, P = 0.002) cross-sectional area of the internal jugular vein at −12 • HDT. The minimum cross-sectional area of the external jugular vein differed significantly between conditions over time (P = 0.001) whereas frontal skin tissue thickness was not significantly different between conditions (P = 0.077, P = 0.811). Data suggests venous congestion at −12 • HDT. Since subjects felt comfortable with lying in −12 • HDT under our experimental conditions, this posture only moderately deteriorates sleep. Obviously, the human body can almost compensate the several fold effects of gravity in HDT posture like an affected CSF circulation, airway obstruction, unusual patterns of propioception and effects on the cardiovascular system.

Clinical autonomic research : official journal of the Clinical Autonomic Research Society, 2018

Since manned missions to the Moon and Mars are planned, we conducted active standing tests with l... more Since manned missions to the Moon and Mars are planned, we conducted active standing tests with lunar, Martian, terrestrial, and 1.8 loads of inertial resistance (+G) modeled through defined parabolic flight maneuvers. We hypothesized that the cardiovascular response to active standing is proportional to the +G load. During partial-+G parabolic flights, 14 healthy test subjects performed active stand-up maneuvers under 1 +G, lunar (0.16 +G), Martian (0.38 +G), and hyper inertial resistance (1.8 +G) while heart rate and finger blood pressure were continuously monitored. We quantified amplitudes and timing of orthostatic response immediately following standing up. The maximum early heart rate increase was 21 (SD ± 10) bpm with lunar, 23 (± 11) bpm with Martian, 34 (± 17) bpm with terrestrial +G, and 40 (± 11) bpm hyper +G. The time to maximum heart rate increased gradually with increasing loads of inertial resistance. The transient blood pressure reduction was most pronounced with hyp...

Injury, 2016

Introduction: Partial weight bearing is part of treatment schemes in orthopedic surgery and traum... more Introduction: Partial weight bearing is part of treatment schemes in orthopedic surgery and traumatology. The aim of the present study was to explore to what degree ground reaction forces during partial weight bearing of the lower leg are related to given instructions and to tibia deformation. Materials and methods: Tibia deformation (torsion, medio-lateral and anterio-posterior bending) was measured for rear foot and forefoot loading, 10 kg, 20 kg and half body weight instructions compared to full loading in five healthy male subjects using the "Optical Segment Tracking" approach, a motioncapturing based method that uses monocortically fixed bone screws. Results: 1. Ground reaction force was a good indicator of tibia deformation. 2. Participants significantly under-loaded during half-body weight instructions (P < 0.001) while they overloaded when loading the forefoot only. 3. Partial-loading instructions led to a highly significant and systematic reduction in peak ground reaction force (GRFpk) in all three types of tibia deformation with substantial variation between measurements. 4. Forefoot usage was associated with significant, albeit moderate increases in GRFpk (P = 0.0031), in AP-bending (P = 0.0027) and in torsion (P < 0.001), compared to rear foot loading. Discussion: These findings result in the following clinical "lessons learned": 1. GRF is a good reflection of loading-induced deformation of the tibia. 2. GRFs are hard to control by subjects/patients. 3. The expectation that forefoot-loading results in larger tibia deformation could not be confirmed in our study. 4. When aiming at a reduction in tibia deformation, rear-foot loading is more preferable than forefoot loading.