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Arieli R.,Israel Naval Medical Institute | Arieli U.,Tel Aviv University | Marmur A.,Technion - Israel Institute of Technology
Respiratory Physiology and Neurobiology | Year: 2015

Bubbles nucleate and develop after decompression at active spots on the luminal aspect of ovine large blood vessels. Series of bubbles were shown to detach from the active spot with a mean diameter of 0.7-1.0. mm in calm conditions. The effect of mechanical disturbance (striking the bowl containing the vessel or tangential flow) was studied on ovine blood vessels stretched on microscope slides and photographed after hyperbaric exposure. Diameter on detachment after a heavy blow to the bowl was 0.87. ±. 0.43. mm (mean. ±. SD), no different from bubbles which detached without striking the bowl (0.86. ±. 0.28. mm). Bubble diameter on detachment during pulsatile tangential flow at 234. cm/min, 0.99. ±. 0.36. mm, was not smaller than that seen in the same blood vessels in calm conditions (0.81. ±. 0.34. mm). The active spots were stained for lipids, proving their hydrophobicity. The most abundant active spots, which produced only a few bubbles, did not stain for lipids thereafter. The possibility that phospholipids were removed along with detached bubbles may correlate with acclimation to diving. The finding of bubble production at the active spots matches observed phenomena in divers: variable sensitivity to decompression, acclimation to diving, the effect of elevated gas load on increased bubble formation, a higher bubble score in the second dive on the same day, and unexplained neurological symptoms after decompression. Large bubbles released from the arterial circulation give serious cause for concern. © 2015 Elsevier B.V. Source


Arieli R.,Israel Naval Medical Institute | Marmur A.,Technion - Israel Institute of Technology
Respiratory Physiology and Neurobiology | Year: 2016

After decompression of ovine large blood vessels, bubbles nucleate and expand at active hydrophobic spots on their luminal aspect. These bubbles will be in the path of the blood flow within the vessel, which might replenish the supply of gas-supersaturated plasma in their vicinity and thus, in contrast with our previous estimations, enhance their growth. We used the data from our previous study on the effect of pulsatile flow in ovine blood vessels stretched on microscope slides and photographed after decompression from hyperbaric exposure. We measured the diameter of 46 bubbles in 4 samples taken from 3 blood vessels (pulmonary artery, pulmonary vein, and aorta) in which both a "multi-bubble active spot" (MBAS)-which produces several bubbles at a time, and at least one "single-bubble active spot" (SBAS)-which produces a single bubble at a time, were seen together. The linear expansion rate for diameter in SBAS ranged from 0.077 to 0.498 mm/min and in MBAS from 0.001 to 0.332 mm/min. There was a trend toward a reduced expansion rate for bubbles in MBAS compared with SBAS. The expansion rate for bubbles in an MBAS when it was surrounded by others was very low. Bubble growth is related to gas tension, and under a flow regime, bubbles expand from a diameter of 0.1 to 1 mm in 2-24 min at a gas supersaturation of 620 kPa and lower. There are two phases of bubble development. The slow and disperse initiation of active spots (from nanobubbles to gas micronuclei) continues for more than 1 h, whereas the fast increase in size (2-24 min) is governed by diffusion. Bubble-based decompression models should not artificially reduce diffusion constants, but rather take both phases of bubble development into consideration. © 2015 Published by Elsevier B.V. Source


Tal D.,Israel Naval Medical Institute | Gonen A.,Israel Naval Medical Institute | Wiener G.,Israel Naval Medical Institute | Bar R.,Israel Naval Medical Institute | And 5 more authors.
Otology and Neurotology | Year: 2012

Hypothesis: To investigate whether the projection of Earth-referenced scenes during provocative motion can alleviate motion sickness severity and prevent motion sickness-induced degradation of performance. Background: Exposure to unfamiliar motion patterns commonly results in motion sickness and decreased performance. Methods: Thirty subjects with moderate-to-severe motion sickness susceptibility were exposed to the recorded motion profile of a missile boat under moderate sea conditions in a 3-degrees-of-freedom ship motion simulator. During a 120-minute simulated voyage, the study participants were repeatedly put through a performance test battery and completed a motion sickness susceptibility questionnaire, while self-referenced and Earth-referenced visual scenes were projected inside the closed simulator cabin. Results: A significant decrease was found in the maximal motion sickness severity score, from 9.83 ± 9.77 (mean ± standard deviation) to 7.23 ± 7.14 (p < 0.03), when the visual display better approximated the full scale of the roll, pitch, and heave movements of the simulator. Although there was a significant decrease in sickness severity, substantial symptoms still persisted. Decision making, vision, concentration, memory, simple reasoning, and psychomotor skills all deteriorated under the motion conditions. However, no significant differences between the projection conditions could be found in the scores of any of the performance tests. Conclusion: Visual information regarding the vessel's movement provided by an artificial horizon device might decrease motion sickness symptoms. However, although this device might be suitable for passive transportation, the continued deterioration in performance measures indicates that it provides no significant advantage for personnel engaged in the active operation of modern vessels. © 2012, Otology & Neurotology, Inc. Source


Tal D.,Israel Naval Medical Institute | Wiener G.,Israel Naval Medical Institute | Shupak A.,Israel Naval Medical Institute | Shupak A.,Rothschild | Shupak A.,Technion - Israel Institute of Technology
Journal of Vestibular Research: Equilibrium and Orientation | Year: 2014

BACKGROUND: Exposure to unfamiliar motion patterns commonly results in motion sickness and a false perception of motion, termed mal de debarquement, on the return to stable conditions. OBJECTIVE: To investigate whether motion sickness severity is correlated with the duration and severity of mal de debarquement; to study the possible preventive effect of projecting earth-referenced scenes (an artificial horizon) during exposure to motion on the development of mal de debarquement. METHODS: Thirty subjects were exposed to the recorded motion profile of a boat in a 3-degrees-of-freedom ship motion simulator. During the simulated voyage, the study participants were repeatedly put through a performance test battery and completed a motion sickness susceptibility questionnaire, while self-referenced and earth-referenced scenes were projected inside the simulator cabin. Six hours post disembarkation, subjects completed a questionnaire on mal de debarquement duration and severity. RESULTS: Mal de debarquement, mostly of mild severity, was reported following 59% of the exposures to the provocative motion profile, and in 79% of cases lasted less than 6 hours. The incidence of mal de debarquement, its duration, and the severity of symptoms did not differ between the various artificial horizon projection modes. Significant correlations were found between motion sickness severity and the duration and severity of the mal de debarquement that followed. CONCLUSIONS: The significant correlations found between motion sickness severity and mal de debarquement duration and severity imply that both syndromes might stem from a failure to adapt to new motion conditions. There is a disparity between the previously reported reduction in motion sickness symptoms by an artificial horizon, and its failure to influence the duration and symptoms of mal de debarquement. This might be explained by the different response in the two syndromes, physical versus cognitive. © 2014 - IOS Press and the authors. Source


Arieli R.,Israel Naval Medical Institute | Daskalovic Y.,Israel Naval Medical Institute | Ertracht O.,Israel Naval Medical Institute | Arieli Y.,Israel Naval Medical Institute | And 3 more authors.
American Journal of Emergency Medicine | Year: 2011

Humidification of inspired gas is critical in ventilated patients, usually achieved by heat and moisture exchange devices (HMEs). HME and the endotracheal tube (ETT) add airflow resistance. Ventilated patients are sometimes treated in hyperbaric chambers. Increased gas density may increase total airway resistance, peak pressures (PPs), and mechanical work of breathing (WOB). We tested the added WOB imposed by HMEs and various sizes of ETT under hyperbaric conditions. We mechanically ventilated 4 types of HMEs and 3 ETTs at 6 minute ventilation volumes (7-19.5 L/min) in a hyperbaric chamber at pressures of 1 to 6 atmospheres absolute (ATA). Peak pressure increased with increasing chamber pressure with an HME alone, from 2 cm H 2O at 1 ATA to 6 cm H 2O at 6 ATA. Work of breathing was low at 1 ATA (0.2 J/L) and increased to 1.2 J/L at 6 ATA at minute ventilation = 19.5 L/min. Connecting the HME to an ETT increased PP as a function of peak flow and chamber pressure. Reduction of the ETT diameter (9 > 8 > 7.5 mm) and increase in chamber pressure increased the PP up to 27.7 cm H 2O, resistance to 33.2 cmH 2O*s/L, and WOB to 3.76 J/L at 6 ATA with a 7.5-mm EET. These are much greater than the usually accepted critical peak pressures of 25 cm H 2O and WOB of 1.5 to 2.0 J/L. Endotracheal tubes less than 8 mm produce significant added WOB and airway pressure swings under hyperbaric conditions. The hyperbaric critical care clinician is advised to use the largest possible ETT. The tested HMEs add negligible resistance and WOB in the chamber. © 2011 Elsevier Inc. Source

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