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Research Containing: Human Research

Space radiation measurements on-board ISS–the DOSMAP experiment

by cfynanon 9 June 2015in Biology & Biotechnology No comment

The experiment 'Dosimetric Mapping' conducted as part of the science program of NASA's Human Research Facility (HRF) between March and August 2001 was designed to measure integrated total absorbed doses (ionising radiation and neutrons), heavy ion fluxes and its energy, mass and linear energy transfer (LET) spectra, time-dependent count rates of charged particles and their corresponding dose rates at different locations inside the US Lab at the International Space Station. Owing to the variety of particles and energies, a dosimetry package consisting of thermoluminescence dosemeter (TLD) chips and nuclear track detectors with and without converters (NTDPs), a silicon dosimetry telescope (DOSTEL), four mobile silicon detector units (MDUs) and a TLD reader unit (PILLE) with 12 TLD bulbs as dosemeters was used. Dose rates of the ionising part of the radiation field measured with TLD bulbs applying the PILLE readout system at different locations varied between 153 and 231 microGy d(-1). The dose rate received by the active devices fits excellent to the TLD measurements and is significantly lower compared with measurements for the Shuttle (STS) to MIR missions. The comparison of the absorbed doses from passive and active devices showed an agreement within +/- 10%. The DOSTEL measurements in the HRF location yielded a mean dose equivalent rate of 535 microSv d(-1). DOSTEL measurements were also obtained during the Solar Particle Event on 15 April 2001.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/16604663

Dosimetric mapping

by cfynanon 9 June 2015in Biology & Biotechnology No comment

The experiment Dosimetric Mapping flown as part of the science program of NASA’s Human Research Facility (HRF) is designed to measure at different locations inside the U.S. Lab integrated total absorbed doses (ionizing radiation and neutrons) and heavy ion fluences and its energy, mass and linear transfer (LET) spectra; time dependent fluence rates of charted particles and their corresponding dose rate. This will be achieved by using five nuclear track detector packages (NTDPs) consisting of thermoluminescence dosimeters (TLDs) and plastic nuclear track detectors, two DOSimetry TELscopes (DOSTELs) using two passive implanted planar silicon detectors, four Mobile Dosimetry Units (MDUs) using one passive implanted planar silicon detector with an Control and Interface Unit (CIU)and an onboard TLD system consisting of a small weight TLD Reader and twelve TLD-bulbs, which can be reused after each measurement. Detectors are spread over the whole U.S. Lab. Data are transferred during the mission via the HRF Laptop to the ground. Dose rated of the ionizing part of the radiation field measured with TLD-bulbs at different locations vary between 123 µGy/d and 226 µG/d. DOSTEL measurements are presented for quiet times and during the Solar Particle Event (SPE) on April 15, 2001. The DOSTEL dose rate for quiet times for 194 µGy/d fits excellent to the TLD measurements. Weighted with the radiation quality factor received from measured LET spectra the dose equivalent rate arrives at 504 µSv/d.

Related URLs:
http://dx.doi.org/10.2514/6.2001-4903

Psychological adaptation and salutogenesis in space: Lessons from a series of studies

by cfynanon 9 June 2015in Biology & Biotechnology No comment

Individuals who adapt positively to an inhospitable or extreme environment can derive benefit from their experiences. This positive effect may include an initial improvement in mental health as someone adjusts to the environment (adaptation) as well as more sustained personal growth during the mission (salutogenesis). We review relevant findings from our prior work, including two post-mission surveys of astronauts and cosmonauts, and three studies of crewmembers during missions in a space station simulator, the Mir space station, and the International Space Station (ISS). We also present new analyses showing evidence for adaptation to ISS missions. This finding replicates our previous results from the simulation study, but this effect was not found on the Mir. A better understanding of psychological adaptation and salutogenesis during space flight should help us develop strategies to enhance crewmembers’ in-flight stress tolerance and post-flight adjustment.

Related URLs:
http://www.sciencedirect.com/science/article/pii/S0094576506003067

Radiation Dosimetry in Space: A Systematic Review

by cfynanon 9 June 2015in Biology & Biotechnology No comment

This article presents the results of a systematic literature review to locate peer-reviewed journal articles that offer equivalent or absorbed radiation dose measurements for locations in outer space. The review utilized three separate keyword searches, one using MEDLINE and 2 using Google Scholar. The queries returned a total of 3,779 potential source documents, 819 of which were screened for inclusion. The final article set contained 43 articles. The articles were all in English though they were contributed by authors from 10 different nations. The United States was the most frequent contributor followed by Germany. The articles provided data from every manned US space program except Project Mercury, as well as from 3 Soviet space stations. The article pool displayed recency in publication, with a majority of the articles published in 1990 or later. It is speculated that this is due to a preference for reporting results in technical reports and conference abstracts in the 1960s and 1970s. The shift from research conducted by contractors to the National Aeronautics and Space Administration (NASA) to partnerships with civilian scientists at universities may be responsible for the increased frequency of publication in peer-reviewed journals. The collection of articles provides more than 550 dose measurements for spacecraft and extra-vehicular activity in 42 combinations of inclination and altitude in low Earth orbit. The articles also provide 57 measurements for lunar missions. The most often sampled locations were those that had space stations, followed by measurements taken aboard the Gemini capsules and the Space Shuttle fleet. This review demonstrates that dosimetric data exist in sufficient abundance that they might be further synthesized into useful dose estimation models and tools. Such tools could be of great utility in mission planning and epidemiological studies of the effects of space radiation on human health.

Related URLs:

Dissociation of peripheral and central cardiovascular adaptation during long term space flight

by cfynanon 9 June 2015in Biology & Biotechnology No comment

The device ”Pneumocard” was developed to obtain information on cardiovascular regulation in terms of hemodynamic measurements and heart rate variability during standardized tests aboard the International Space Station (ISS). We tested the hypothesis that cardiac function is well maintained during long term space flight based on different individual regulatory patterns including peripheral vasoconstriction. "Pneumocard" was used during in-flight experiments on ISS for autonomic function testing. ECG, photoplethysmography, respiration, impedance cardiography (ICG, modified four-electrode technique) and seismo cardiography were assessed in six male cosmonauts (age: 35-48 years; BMI: 23-30 kg/m*m; flight duration $>$6 month). Recordings and analysis were made prior to the flight, monthly in-flight as well as post-flight during spontaneous respiration and during maximum voluntary inspiratory apnea. HR remained stable during flight (pre-flight: 62underline{+}2 bpm, late in flight: 65underline{+}3 bpm). Respiratory frequency (RF) tended to decrease during flight (pre-flight: 15underline{+}1 min-1, late in flight: 13underline{+}1 min-1). Diastolic blood pressure (DBP) decreased during flight (pre-flight:77underline{+}2 mmHg, late in flight: 72underline{+}2 mmHg). Pulse wave transit time (PWTT) was shorter during flight compared to pre-flight values (pre-flight: 201underline{+}6 ms, late in flight: 195underline{+}7 ms). Interestingly, in individual astronauts the decrease of pulse wave transit time was more pronounced despite the relative increase of stroke volume. The highest HR, RF, DBP values and the lowest PWTT were measured after flight. Maximum voluntary apnea time was prolonged (pre-flight: 76underline{+}3 s, late in flight: 124underline{+}6 s) during flight. The maximum of the first time derivative of the ICG (dZ/dt), which is directly related to stroke volume, increased during flight (pre-flight: 1.66underline{+}0.15 $Omega$/s, late in flight: 2.36underline{+}0.25 $Omega$/s). Changes of dZ/dt during inspiratory apnea were more pronounced during flight, but the minimum value reached during inspiratory apnea was higher compared to preflight values. Post flight values of dZ/dt were similar compared to pre flight values. The increase of dZ/dt during flight at rest, the higher absolute values of dZ/dt during maximum voluntary apnea in-flight as well as the similar values after flight indicate well maintained cardiac function. The decrease of PWTT during flight may suggest increased peripheral vascular tone which may reflect dissociation between central and peripheral adaptational hemodynamic mechanisms to microgravity. Our results show profound inter-individual differences which may have influence on post flight autonomic dysfunction. The results indicate the possibility of an individual hemodynamic management during and after flight as well as before and after extravehicular activities.

Related URLs:

Pulmonary gas exchange is not impaired 24 h after extravehicular activity

by cfynanon 9 June 2015in Biology & Biotechnology No comment

Extravehicular activity (EVA) during spaceflight involves a significant decompression stress. Previous studies have shown an increase in the inhomogeneity of ventilation-perfusion ratio (V̇a/Q̇) after some underwater dives, presumably through the embolic effects of venous gas microemboli in the lung. Ground-based chamber studies simulating EVA have shown that venous gas microemboli occur in a large percentage of the subjects undergoing decompression, despite the use of prebreathe protocols to reduce dissolved N2 in the tissues. We studied eight crewmembers (7 male, 1 female) of the International Space Station who performed 15 EVAs (initial cabin pressure 748 mmHg, final suit pressure either ∼295 or ∼220 mmHg depending on the suit used) and who followed the denitrogenation procedures approved for EVA from the International Space Station. The intrabreath V̇a/Q̇ slope was calculated from the alveolar Po2 and Pco2 in a prolonged exhalation maneuver on the day after EVA and compared with measurements made in microgravity on days well separated from the EVA. There were no significant changes in intrabreath V̇a/Q̇ slope as a result of EVA, although there was a slight increase in metabolic rate and ventilation (∼9%) on the day after EVA. Vital capacity and other measures of pulmonary function were largely unaltered by EVA. Because measurements could only be performed on the day after EVA because of logistical constraints, we were unable to determine an acute effect of EVA on V̇a/Q̇ inequality. The results suggest that current denitrogenation protocols do not result in any major lasting alteration to gas exchange in the lung.

Related URLs:
http://jap.physiology.org/jap/99/6/2233.full.pdf

Comparison of knee motion on Earth and in space: an observational study

by cfynanon 9 June 2015in Biology & Biotechnology No comment

BACKGROUND: Spaceflight has been shown to cause atrophy, reduced functional capacity, and increased fatigue in lower-limb skeletal muscles. The mechanisms of these losses are not fully understood but are thought to result, in part, from alteration in muscle usage. METHODS: Knee-joint angles and lower-extremity muscle activity were measured continually, via elecrogoniometry and surface electromyography respectively, from two subjects during entire working days of activity on Earth and onboard the International Space Station (ISS). RESULTS: On Earth the distribution of angular positions of the knee was typically bimodal, with peaks of >75 degrees of flexion and in almost full extension (<15 degrees of flexion). However, on the ISS, a single peak in the mid-range of the available range of motion was seen. The knee joint was also moved through fewer excursions and the excursions were smaller in amplitude, resulting in a reduced span of angles traversed. The velocities of the excursions in space were lower than those used on Earth. CONCLUSION: These results demonstrate that, in space, overall knee-joint motion is reduced, and there is a transformation in the type of muscle action compared to that seen on Earth, with more isometric action at the expense of concentric and particularly eccentric action.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/16613607

Hemodynamic effects of midodrine after spaceflight in astronauts without orthostatic hypotension

by cfynanon 9 June 2015in Biology & Biotechnology No comment

INTRODUCTION: Orthostatic hypotension and presyncope are common and potentially serious risks for astronauts returning from space. Susceptible subjects fail to generate an adequate adrenergic response to upright posture. The alpha-1 adrenergic agonist, midodrine, may be an effective countermeasure. We tested the hypothesis that midodrine would have no negative hemodynamic effect on healthy astronauts returning from space. METHODS: Five male astronauts participated in preflight and post-flight tilt testing on a control flight as well as on the test flights, where midodrine (10 mg, orally) was administered after landing approximately 1 h before testing. RESULTS: None of these astronauts exhibited orthostatic hypotension or presyncope before or after either flight. Midodrine did not cause any untoward reactions in these subjects before or after flight; in fact, a modest beneficial effect was seen on postflight tachycardia (p = 0.036). DISCUSSION: These data show that midodrine protected against post-spaceflight increases in heart rate without having any adverse hemodynamic effects on non-presyncopal, male astronauts. Among these subjects, midodrine was a safe cardiovascular countermeasure.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/16676655

Midodrine prescribed to improve recurrent post-spaceflight orthostatic hypotension

by cfynanon 9 June 2015in Biology & Biotechnology No comment

Many astronauts exhibit post-spaceflight orthostatic hypotension due to inadequate norepinephrine release when in an upright posture. We hypothesized that an alpha1-adrenergic agonist, midodrine, would be an effective countermeasure. A female astronaut, who had problems with postflight orthostatic hypotension after a previous flight, consumed 10 mg midodrine after a subsequent flight, prior to her tilt test. Hemodynamic variables were compared between the two flights. Midodrine prevented severe falls in stroke volume, cardiac output and systolic pressure, and severe increases in heart rate without increasing vascular resistance, thus preventing orthostatic hypotension. This is the first report showing that midodrine has the potential to improve post-spaceflight orthostatic hypotension and suggesting that reduced venous return contributes to the etiology.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/15198285

Low Back Pain in Microgravity and Bed Rest Studies

by cfynanon 9 June 2015in Biology & Biotechnology No comment

Background: The prevalence of low back pain (LBP) for astronauts in space (68%) is higher than the 1-mo prevalence for the general population on Earth (39%). It is unclear whether differences occur between healthy subjects and astronauts with a history of LBP. Knowledge of this issue is important to assess whether a history of LBP could have an operational impact. Methods: We evaluated LBP prospectively during short duration spaceflight (15 d; N = 20) and compared this with similar data collected during two bed rest studies (N = 40). Astronauts completed a questionnaire 5–10 d preflight, during each flight day, and 5–10 d postflight. Results: All astronauts with a history of LBP also developed LBP in flight. These astronauts reported a significantly longer duration of LBP and a different pain location. LBP was most often experienced in the central area of the lower back during spaceflight with an incidence of 70% and a mean pain level of 3 (on a scale of 0–10). Pain resolved within 10 d of flight. No neurological signs were present. The most frequently reported countermeasure was assuming a “knees to chest (fetal tuck) position” combined with stretching. Greater LBP intensity was reported in spaceflight than bed rest with a trend indicating a greater number of days of pain during spaceflight. Discussion: The current study represents a prospective study of LBP in spaceflight. The results indicate that LBP is self-limiting in spaceflight and should not pose an operational risk. Prior LBP on Earth appears to be a risk factor for LBP in spaceflight.

Related URLs:
http://www.ingentaconnect.com/content/asma/amhp/2015/00000086/00000006/art00008
http://dx.doi.org/10.3357/AMHP.4169.2015

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