Aviat Space Envir Md
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Aviat Space Envir Md · Dec 2009
Randomized Controlled TrialPre-dive vibration effect on bubble formation after a 30-m dive requiring a decompression stop.
The preconditioning of divers to reduce post-dive decompression sickness (DCS) has gained increased interest in diving medical research over the last few years. The beneficial effects of physical exercise, oxygen breathing, hyperbaric exposure, heat exposure, hyperhydration, or nitroglycerin administration before the dive are only a few examples of ongoing research. In this work, we investigated the effects of pre-dive whole-body vibration on post-dive bubble formation. ⋯ As there was no observed change in FMD after vibration, we do not believe a nitric oxide mediated mechanism is involved; rather, a mechanical dislodgement or enhanced lymphatic elimination of gas nuclei is hypothesized.
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Aviat Space Envir Md · Dec 2009
Hyperventilation in response to progressive reduction in central blood volume to near syncope.
There is little evidence to support the usefulness in monitoring respiration during casualty triage and transport as an early indicator of hemorrhage severity and trauma patient outcome. We, therefore, tested the hypothesis that hyperventilation can be elicited by progressive reductions in central blood volume independent of metabolic stimuli. ⋯ Increased V(E) at LBNP(max) combined with reduced E(T)co2 in the absence of changes in blood and systemic metabolic stimuli support the hypothesis that severe reductions in central blood volume drive hyperventilation. The endogenous "respiratory pump" may be a protective strategy to optimize cardiac filling in conditions of central hypovolemic hypotension, but its late appearance indicates that respiratory parameters may not be useful as a clinical metric for early prediction of patient outcome during hemorrhage.
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Aviat Space Envir Md · Dec 2009
Bed rest and cognition: effects on executive functioning and reaction time.
Executive functions are high-order aspects of cognition heavily dependent upon the prefrontal cortex. Both prefrontal cortex activity and executive function task performance are enhanced by participation in aerobic physical activity, suggesting that a lack of such activity during the bed rest model of prolonged weightlessness might induce executive function deficits. ⋯ Our results provide some evidence for a detrimental effect of bed rest on executive functioning. Whether this stems from a lack of aerobic physical activity and/or changes in the prefrontal cortex remains to be determined. Cognitive effects of bed rest could have implications for the planned human exploration of Mars, and for medical and lifestyle conditions with inadequate levels of aerobic physical activity.