Derivation of Mortal Injury Metric for Studies of Rapid Decompression of Depth-Acclimated Physostomous Fish

AbstractThe biochemical mechanisms of oxygen poisoning are discussed together with the signs and symptoms produced clinically. Investigation of 35 subjects performing work (mean 02 consumption 1.4 l./min) for 40 minutes in a pressure chamber at simulated depths of 20 to 47 feet of sea water showed that this degree of exercise markedly reduced the oxygen exposure tolerance of the subjects. This investigation also showed that rapid decompression of subjects breathing oxygen can produce an exacerbation of existing symptoms and these results are discussed.It is stressed that any breathing mixture containing a partial pressure of oxygen in excess of 150 torr constitutes an environment which is hyperbaric with respect to oxygen and caution is advised in the administration of oxygen to any patient.

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Hearing Aids Performance in Hypobaric Environments

Aerospace Medicine and Human Performance ◽

10.3357/amhp.5893.2021 ◽

2021 ◽

Vol 92 (9) ◽

pp. 738-743

Author(s):

Marco Lucertini ◽

Filippo Sanjust ◽

Roberto Manca ◽

Luigi Cerini ◽

Lorenzo Lucertini ◽

...

Keyword(s):

High Altitude ◽

Hearing Aids ◽

Ambient Air ◽

Recording System ◽

Simulated Altitude ◽

Acoustic Transducers ◽

Before And After ◽

Rapid Decompression ◽

Pressure Changes ◽

First Session

OBJECTIVE: High altitudes imply exposure to a decreased ambient air pressure. Such a situation may also alter the performance of acoustic transducers using vibrating diaphragms due to air rarefaction. This study aimed at analyzing the performance at high altitude of hearing aids (HAs) where mechano-electric and electro-mechanic transducers are used. METHODS: A hypobaric chamber was used to perform two separated experimental sessions. In the first one two commercial models of HAs were exposed to a simulated altitude of 25,000 ft (7620 m) and to a subsequent rapid decompression profile, with a rapid climb (< 3 s) from 8000 (2438 m) to 25,000 ft. The second session separately analyzed the performance of microphone and receiver at an altitude of 9000 and 15,000 ft (2743 and 4572 m). Before and after the first session, the HAs were tested with an electronic ear while a dedicated recording system was used in the second session. RESULTS: No HA damage or dysfunction was detected during the first session. In the second one, the microphone showed a mild decrease of its output, while the receiver exhibited a much higher reduction of its output. CONCLUSION: Our findings highlight the safe use of HAs even under extreme environmental pressure changes. For altitudes exceeding 10,000 ft (3048 m), a recalibration of the HAs output via a dedicated program may be suggested. Lucertini M, Sanjust F, Manca R, Cerini L, Lucertini L, Sisto R. Hearing aids performance in hypobaric environments. Aerosp Med Hum Perform. 2021; 92(9):738743.

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Loss of cabin pressure and rapid decompression

Handbook of Aviation and Space Medicine ◽

10.1201/9780429021657-12 ◽

2019 ◽

pp. 77-82

Author(s):

Nicholas Green ◽

Steven Gaydos ◽

Hutchison Ewan ◽

Edward Nicol

Keyword(s):

Rapid Decompression

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Transient Hyperemia Immediately after Rapid Decompression of Chronic Subdural Hematoma

Neurosurgery ◽

10.1097/00006123-199909000-00014 ◽

1999 ◽

Vol 45 (3) ◽

pp. 484-489 ◽

Cited By ~ 47

Author(s):

Kuniaki Ogasawara ◽

Keiji Koshu ◽

Takashi Yoshimoto ◽

Akira Ogawa

Keyword(s):

Subdural Hematoma ◽

Chronic Subdural Hematoma ◽

Rapid Decompression

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A Rare Complication of Chronic Subdural Hematoma Evacuation: Brain Stem Hemorrhage: A Case Report

Romanian Neurosurgery ◽

10.2478/romneu-2018-0057 ◽

2018 ◽

Vol 32 (3) ◽

pp. 462-465 ◽

Cited By ~ 1

Author(s):

Ghassen Gader ◽

Mouna Rkhami ◽

Maher Ben Salem ◽

Mohamed Badri ◽

Kamel Bahri ◽

...

Keyword(s):

Brain Stem ◽

Subdural Hematoma ◽

Rare Complication ◽

Chronic Subdural Hematoma ◽

The Elderly ◽

Burr Hole ◽

Sudden Increase ◽

Vascular Disruption ◽

Rapid Decompression ◽

Surgical Modality

Abstract Chronic subdural hematoma (CSDH), which commonly affects the elderly, is one of the most frequent, but also benign neurosurgical pathologies. Burr hole drainage is the standard surgical modality for evacuation of a CSDH. This technique is known to be safe, with low morbidity and mortality rates. However, postoperative complications have occasionally been reported. We report the case of a 70-year-old man who presented a fatal brain stem hemorrhage after burr-hole drainage for unilateral chronic subdural hematoma. Asymmetrical and rapid decompression were thought to be leading to vascular disruption or sudden increase in cerebral blood flow, was probably responsible for the secondary brain stem bleeding. Therefore, a slow rate of evacuation of chronic subdural hematomas, as well as rigorous postoperative reanimation, are recommended in order to prevent serious complications.

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Bubbles and element clusters in rock melts: A chicken and egg problem

10.5194/egusphere-egu21-60 ◽

2021 ◽

Author(s):

Renelle Dubosq ◽

Pia Pleše ◽

Brian Langelier ◽

Baptiste Gault ◽

David Schneider

Keyword(s):

Heterogeneous Nucleation ◽

Homogeneous Nucleation ◽

Growth Dynamics ◽

Gas Bubbles ◽

Atom Probe ◽

Bubble Nucleation ◽

Interface Element ◽

Rich Cluster ◽

Heterogeneous Distribution ◽

Rapid Decompression

<p>The nucleation and growth dynamics of gas bubbles and crystals play a vital function in determining the eruptive behaviour of a magma. Their rate and relative timing, among other factors, are controlled by the magma&#8217;s ascent rate. Investigating the kinetics of decompression-induced degassing and crystallization processes can thus give us insight into the rheology of magmas. For example, the rapid decompression of magmas inhibits microlite crystallization and bubble nucleation during ascent leading to crystallization and degassing at shallow levels. This results in a drastic increase in viscosity and an over pressured system, which can lead to violent eruptions. Although many experiments and numerical simulations of magma decompression have been carried out, nascent and initial bubble nucleation remain poorly understood. It is widely accepted that there are two ways bubbles can nucleate within a melt: heterogeneous (on a pre-existing surface) and homogeneous nucleation (within the melt), where homogeneous nucleation requires a higher volatile supersaturation. It has since been tentatively suggested that homogeneous nucleation is simply a variety of heterogeneous nucleation where nucleation occurs on the surface of submicroscopic crystals. However, evidence of these crystals is equivocal. Thus, we have combined novel 2D and 3D structural and chemical microscopy techniques including scanning transmission electron microscopy (STEM), electron energy-loss spectroscopy (EELS) mapping, and atom probe tomography (APT) to investigate the presence of sub-nanometer scale chemical heterogeneities in the vicinity of gas bubbles within an experimental andesitic melt. The combined STEM and EELS data reveal a heterogeneous distribution of bubbles within the melt ranging between 20-100 nm in diameter, some of which have Fe and/or Ca element clusters at the bubble-melt interface. Element clusters enriched in Fe, Ca, and Na are also observed heterogeneously distributed within the melt. The reconstructed APT data reveals bubbles as low ionic density regions overlain by a Na-, Ca-, and K-rich cluster and heterogeneously distributed Fe clusters within the bulk of the melt. Based on these observations, our data demonstrate the existence of nano-scale chemical heterogeneities within the melt and at the bubble-melt interface of bubbles that were previously interpreted to be nucleated homogeneously within the melt, therefore contributing to the proposed hypothesis that homogeneous nucleation could in fact be a variety of heterogeneous nucleation. These results highlight the need to redefine homogeneous nucleation and revisit whether bubbles or crystals occur first within volcanic melts.&#160;</p>

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