Can skin temperature recordings predict GLOC?

Background: Modern aerial combat manouevres are an enormous challenge for human physiology [1,2].To predict the probability of a g- force induced loss of consciousness (GLOC) has been subject of numerous studies. Changes in perfusion (NIRS) and/or function of the brain (EEG, evoked potentials) have been the primary focus searching a predictor while centrifugal reallocation of blood volume is the primary cause for this blackout.To determine the peripheral bloodflow skin temperature might be used [3]. We present a pilot study using fast measurements of peripheral temperatures to predict this peripheral pooling effect. Material & Methods: 9 of the 20 subjects suffered an almost loss of consciousness (ALOC). Peripheral temperatures tended to be higher in subjects with an almost blackout.The strongest effect regarding the difference of the two groups was recorded at the upper arm (p<0.05). 20 healthy subjects were tested using a combined lower body negative pressur/tilt table.The produced push-pull effect has been used to select pilots suited to fly a forth generation jet fighter. The complete procedure was split in two phases before, one phase during and one phase after the induced push-pull effect. Recording skin III temperatures proximal and distal of the upper and lower limbs allowed to quantify the effect of a peripheral perfusion change. Results & Discussion: The probability of ALOC in this experiment could be predicted recording peripheral temperatures. Higher peripheral temperatures before the push-pull phase might be an indicator for peripheral vasodilation or a lowered sympathetic activation [4]. However, to verify this effect, the experiment has to be repeated using more subjects and different hyper-g scenarios as the short and long arm centrifuge and real aircraft manoeuvres. References: 1. Hanousek, J, P Dosel, J Cmiral, and J Petricek. "Physiological Response of Pilots to the Load of Lower Body Negative Pressure." J Gravit Physiol 4, no. 2 (1997): P33-4 2. Dosel, P, J Hanousek, J Cmiral, and J Petricek. "Physiological Response of Pilots to the LBNP-, Flight-, and Centrifuge Load." J Gravit Physiol 5, no. 1 (1998): P41-2 3. Rubinstein, E H, and D I Sessler. "Skin-surface Temperature Gradients Correlate with Fingertip Blood Flow in Humans." Anesthesiology 73, no. 3 (1990): 541-5 4. Charkoudian, Nisha. "Skin Blood Flow in Adult Human Thermoregulation: How It Works, When It Does Not, and Why." Mayo Clinic proceedings. Mayo Clinic 78, no. 5 (2003): doi:10.4065/78.5.60

Can skin temperature measurement contribute to GLOC prediction?

Introduction: Modern aerial combat manouevres are an enormous challenge for human physiology (1,2). To predict the probability of a g-force induced loss of consciousness (GLOC) has been subject of numerous studies. Changes in perfusion (NIRS) and/or function of the brain (EEG, evoked potentials) have been the primary focus searching a predictor while centrifugal reallocation of blood volume is the primary cause for this blackout. To determine the peripheral bloodflow skin temperature might be used (3). We present a pilot study using fast measurements of peripheral temperatures to predict this peripheral pooling effect. Methods: 20 healthy subjects were tested using a combined lower body negative pressur/tilt table. The produced push-pull effect has been used to select pilots suited to fly a forth generation jet fighter. The complete procedure was split in two phases before, one phase during and one phase after the induced push-pull effect. Recording skin temperatures proximal and distal of the upper and lower limbs allowed to quantify the effect of a peripheral perfusion change. Results: 9 of the 20 subjects suffered an almost loss of consciousness (ALOC). Peripheral temperatures tended to be higher in subjects with an almost blackout. The strongest effect regarding the difference of the two groups was recorded at the upper arm (p<0.05). Discussion: The probability of ALOC in this experiment could be predicted recording peripheral temperatures. Higher peripheral temperatures before the push-pull phase might be an indicator for peripheral vasodilation or a lowered sympathetic activation (4). However, to verify this effect, the experiment has to be repeated using more subjects and different hyper-g scenarios as the short and long arm centrifuge and real aircraft manoeuvres

Schwerelosigkeit als Ursache für Schlafstörungen in der Raumfahrt?

Fragestellung: Dass Astronaut*innen im Weltall oftmals unter Schlafman- gel leiden, wurde inzwischen vielfach in Studien gezeigt. Als ursächlich werden u. a. die physiologischen Änderungen durch Schwerelosigkeit angenommen. Diese wurde im Rahmen der einer Langzeit-Bettruhestu- die, der sogenannten AGBRESA Studie (Artificial Gravity Bed Rest Study), durch zweimonatige Bettruhe in 6 Kopftieflage simuliert. Patienten und Methoden: Eingeschlossen waren 24 Proband*innen (16 davon männlich, 23 bis 54 Jahre). Für die Erhebung der objektiven Schlaf- parameter wurde an insgesamt sechs Studientagen (zweimal vor Eintritt in die Kopftieflage [Baseline Data Collection: BDC-10 und BDC-9]; vier- mal während [Head-Down Tilt: HDT1; HDT8; HDT30; HDT-58] und zweimal nach Ende der Bettruhe [Recovery: R + 1; R + 12]) [AD1] eine Polysomno- graphie durchgeführt. [EE2] Mit einer mixed ANOVA und post-hoc Stepdown-Bonferroni Adjustie- rung wurde auf signifikante Unterschiede zwischen Baseline (BDC-9) und HDT1, HDT58, R + 1 und R + 12 in der Anzahl an Arousals, Sleep onset la- tency (SOL), Total sleep time ( TST), Schlafeffizienz (SE), Wake after sleep onset ( WASO) und den Schlafstadien untersucht. Zusätzlich wurde eine gemischte lineare Regression dieser Parameter über den Zeitraum der Kopftieflage durchgeführt. Ergebnisse: Die Anzahl der Arousals war an Studientag HDT-58 (p = 0,0004), R + 1 (p = 0,0004) und R + 12 (p = 0,0004) im Vergleich zu BDC-9 erhöht, ebenso war die SOL in HDT-58 länger als in BDC-9 (p = 0,0207). Im Vergleich zu BDC-9 war die TST in HDT-1 ( TST: p = 0,0081) und HDT-58 (p = 0,0086) verkürzt und die SE in HDT-58 (p = 0,0150) gerin- ger [EE1]. Auch die Dauer von N3 [AD2] war verglichen mit BDC-9 in HDT-1 signifikant kürzer (p = 0,0234). Die Anzahl der Arousals (p < 0,0001) zeigte eine lineare Abnahme über die Zeit der Kopftieflage. Schlussfolgerungen: Die physiologischen Veränderungen, die mit der Umstellung der Körperposition auf Kopftieflage einhergehen, bewirkten eine Verkürzung der Schlafdauer und eine Verschlechterung der Schlafef- fizienz und -qualität. Die Schwerelosigkeit könnte somit ein wichtiger ur- sächlicher Faktor der beobachteten Schlafveränderungen bei Astronaut*- innen im All sein. Eine Adaption an die Kopftieflage im Sinne einer Verbesserung der Schlafdauer und -qualität über die Zeit zeigte sich nicht. Übertragen auf die Situation von Astronaut*innen können diese Schlaf- veränderungen ein Problem für die Sicherheit und Gesundheit darstellen

The oxidative burst reaction in mammalian cells depends on gravity

Gravity has been a constant force throughout the Earth's evolutionary history. Thus, one of the fundamental biological questions is if and how complex cellular and molecular functions of life on Earth require gravity. In this study, we investigated the influence of gravity on the oxidative burst reaction in macrophages, one of the key elements in innate immune response and cellular signaling. An important step is the production of superoxide by the NADPH oxidase, which is rapidly converted to H2O2 by spontaneous and enzymatic dismutation. The phagozytosis-mediated oxidative burst under altered gravity conditions was studied in NR8383 rat alveolar macrophages by means of a luminol assay. Ground-based experiments in "functional weightlessness" were performed using a 2 D clinostat combined with a photomultiplier (PMT clinostat). The same technical set-up was used during the 13th DLR and 51st ESA parabolic flight campaign. Furthermore, hypergravity conditions were provided by using the Multi-Sample Incubation Centrifuge (MuSIC) and the Short Arm Human Centrifuge (SAHC). The results demonstrate that release of reactive oxygen species (ROS) during the oxidative burst reaction depends greatly on gravity conditions. ROS release is 1.) reduced in microgravity, 2.) enhanced in hypergravity and 3.) responds rapidly and reversible to altered gravity within seconds. We substantiated the effect of altered gravity on oxidative burst reaction in two independent experimental systems, parabolic flights and 2D clinostat / centrifuge experiments. Furthermore, the results obtained in simulated microgravity (2D clinorotation experiments) were proven by experiments in real microgravity as in both cases a pronounced reduction in ROS was observed. Our experiments indicate that gravity-sensitive steps are located both in the initial activation pathways and in the final oxidative burst reaction itself, which could be explained by the role of cytoskeletal dynamics in the assembly and function of the NADPH oxidase complex