Pre-dive Whole-Body Vibration Better Reduces Decompression-Induced Vascular Gas Emboli than Oxygenation or a Combination of Both

Purpose: Since non-provocative dive profiles are no guarantor of protection against decompression sickness, novel means including pre-dive “preconditioning” interventions, are proposed for its prevention. This study investigated and compared the effect of pre-dive oxygenation, pre-dive whole body vibration or a combination of both on post-dive bubble formation. Methods: Six healthy volunteers performed 6 no-decompression dives each, to a depth of 33 mfw for 20 min (3 control dives without preconditioning and 1 of each preconditioning protocol) with a minimum interval of 1 week between each dive. Post-dive bubbles were counted in the precordium by two-dimensional echocardiography, 30 and 90 min after the dive, with and without knee flexing. Each diver served as his own control. Results: Vascular gas emboli (VGE) were systematically observed before and after knee flexing at each post-dive measurement. Compared to the control dives, we observed a decrease in VGE count of 23.8 ± 7.4% after oxygen breathing (p < 0.05), 84.1 ± 5.6% after vibration (p < 0.001), and 55.1 ± 9.6% after vibration combined with oxygen (p < 0.001). The difference between all preconditioning methods was statistically significant. Conclusions: The precise mechanism that induces the decrease in post-dive VGE and thus makes the diver more resistant to decompression stress is still not known. However, it seems that a pre-dive mechanical reduction of existing gas nuclei might best explain the beneficial effects of this strategy. The apparent non-synergic effect of oxygen and vibration has probably to be understood because of different mechanisms involved

Oxygen Microbubbles Improve Radiotherapy Tumor Control in a Rat Fibrosarcoma Model – A Preliminary Study

Cancer affects 39.6% of Americans at some point during their lifetime. Solid tumor microenvironments are characterized by a disorganized, leaky vasculature that promotes regions of low oxygenation (hypoxia). Tumor hypoxia is a key predictor of poor treatment outcome for all radiotherapy (RT), chemotherapy and surgery procedures, and is a hallmark of metastatic potential. In particular, the radiation therapy dose needed to achieve the same tumor control probability in hypoxic tissue as in normoxic tissue can be up to 3 times higher. Even very small tumors (<2–3 mm3) comprise 10–30% of hypoxic regions in the form of chronic and/or transient hypoxia fluctuating over the course of seconds to days. We investigate the potential of recently developed lipid-stabilized oxygen microbubbles (OMBs) to improve the therapeutic ratio of RT. OMBs, but not nitrogen microbubbles (NMBs), are shown to significantly increase dissolved oxygen content when added to water in vitro and increase tumor oxygen levels in vivo in a rat fibrosarcoma model. Tumor control is significantly improved with OMB but not NMB intra-tumoral injections immediately prior to RT treatment and effect size is shown to depend on initial tumor volume on RT treatment day, as expected

Ultrasound Measurement of Vascular Density to Evaluate Response to Anti-angiogenic Therapy in Renal Cell Carcinoma

Background: Functional and molecular changes often precede gross anatomical changes, so early assessment of a tumor's functional and molecular response to therapy can help reduce a patient's exposure to the side effects of ineffective chemotherapeutics or other treatment strategies. Objective: Our intent was to test the hypothesis that an ultrasound microvascular imaging approach might provide indications of response to therapy prior to assessment of tumor size. Methods: Mice bearing clear-cell renal cell carcinoma xenograft tumors were treated with antiangiogenic and Notch inhibition therapies. An ultrasound measurement of microvascular density was used to serially track the tumor response to therapy. Results: Data indicated that ultrasound-derived microvascular density can indicate response to therapy a week prior to changes in tumor volume and is strongly correlated with physiological characteristics of the tumors as measured by histology (ρ = 0.75). Furthermore, data demonstrated that ultrasound measurements of vascular density can determine response to therapy and classify between-treatment groups with high sensitivity and specificity. Conclusion/Significance: Results suggests that future applications utilizing ultrasound imaging to monitor tumor response to therapy may be able to provide earlier insight into tumor behavior from metrics of microvascular density rather than anatomical tumor size measurements

Computational and experimental techniques towards optimising the cardiovascular risk assessment of hyperbaric decompression stress caused by circulatory bubble dynamics

This work focuses on developing new techniques towards the quantification of hyperbaric decompression stress. Instead of just preventing decompression sickness (DCS), the aim is to go towards developing an environmental cardiovascular personalised stress index, especially as sub-clinical long terms effects of even recreational scuba diving have been demonstrated. From an engineering perspective, despite the longevity of the research field, a number of fundamental issues that remain unknown have prevented efficient modelling. The aim of this thesis is to directly tackle the research methodology by developing three tailored tools. Firstly, we develop a simulation platform in MatLab to model the diving process by optimizing the implementation of dissolved gas phase tracking decompression algorithms. This platform can be used to simulate diving scenarios, but also analyse real dive profiles. From a first analysis on real profiles provided to us by the European Divers Alert Network database, we find as expected that these existing models are poor predictors of accidents, but also demonstrate that ascent rate seems to be an important predictor of DCS for the range of profiles considered. Secondly, a fundamental issue for modelling the decompression phenomenon is that the precise formation site and growth mechanism of decompression bubbles in vivo remains unknown. We develop a novel experimental set-up and analysis code for the real-time optical study of decompression induced bubble growth dynamics. Looking at bubble growth from a gas saturated solution on ex-vivo muscle and fat tissues, we show that the role of the substrate from which bubble detach plays a significant role. Bubble density, nucleation threshold, detachment size and coalescence behaviour are shown significantly different for the two substrates, whereas growth rates after a critical size are governed by diffusion as expected, and a competition for dissolved gas between adjacent multiple bubbles is demonstrated. These findings are not accounted for in current modelling efforts so our experimental set-up could be used in the development of a more physiologically relevant decompression model. Thirdly, an important question in terms of decompression modelling optimisation is the precise definition of the evaluation endpoint. Vascular circulating bubbles are normally assessed semi-quantitatively by trained human raters who grade the severity on echocardiograms. We show statistically that this is highly rater-dependent compared to a new counting methodology which is found to perform significantly better but is more time-consuming. We then use image processing techniques to semi-automate this new counting methodology with good comparison to human raters, significantly reducing the time needed for the assessment. This new method could be added to decompression model validation protocols, as well as used in physiology experiments looking at predictive parameters for, or preventive measures against, circulating gas bubbles post-dive. The proposed experimental and computational techniques could be used towards optimising the cardiovascular risk assessment of hyperbaric decompression stress caused by circulatory bubble dynamics.Open Acces

ULTRASONOGRAPHIC ASSESSMENT OF NECK MUSCULAR SIZE AND RANGE OF MOTION IN RUGBY PLAYERS.

World Rugby Union laws are constantly evolving towards stringent injury-prevention, particularly for contested scrums, since front row players are most at risk of cervical spine injuries. Recently, some countries have also introduced tailored training programs and minimum performance requirements for playing in the front row. Nevertheless, these approaches lack an objective assessment of each cervical muscle that would provide protective support.info:eu-repo/semantics/publishe

Recreational diving today: decompression habits, DAN Europe database insights.

info:eu-repo/semantics/publishe

Pre-dive Whole-Body Vibration Better Reduces Decompression-Induced Vascular Gas Emboli than Oxygenation or a Combination of Both.

Purpose: Since non-provocative dive profiles are no guarantor of protection against decompression sickness, novel means including pre-dive "preconditioning" interventions, are proposed for its prevention. This study investigated and compared the effect of pre-dive oxygenation, pre-dive whole body vibration or a combination of both on post-dive bubble formation. Methods: Six healthy volunteers performed 6 no-decompression dives each, to a depth of 33 mfw for 20 min (3 control dives without preconditioning and 1 of each preconditioning protocol) with a minimum interval of 1 week between each dive. Post-dive bubbles were counted in the precordium by two-dimensional echocardiography, 30 and 90 min after the dive, with and without knee flexing. Each diver served as his own control. Results: Vascular gas emboli (VGE) were systematically observed before and after knee flexing at each post-dive measurement. Compared to the control dives, we observed a decrease in VGE count of 23.8 ± 7.4% after oxygen breathing (p < 0.05), 84.1 ± 5.6% after vibration (p < 0.001), and 55.1 ± 9.6% after vibration combined with oxygen (p < 0.001). The difference between all preconditioning methods was statistically significant. Conclusions: The precise mechanism that induces the decrease in post-dive VGE and thus makes the diver more resistant to decompression stress is still not known. However, it seems that a pre-dive mechanical reduction of existing gas nuclei might best explain the beneficial effects of this strategy. The apparent non-synergic effect of oxygen and vibration has probably to be understood because of different mechanisms involved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

DecoBubbles.com: The first crowdsourcing initiative to expedite VGE counting in 2D-ultrasound recordings and provide labels for machine learning

Introduction/Background Venous gas emboli (VGE) detected with echocardi­ography post-dive are often used as a marker of decompression stress. The very time-consuming analysis of the acquired videos can help elucidate inter- and intrasubject variability in VGE, and DCS susceptibility. This collaborative project aims to reduce the time needed to count and analyze cardiac ultrasound videos and help train an Al to complete the task. To accomplish this, an interactive web platform 'www.decobubbles.com' was developed that allows crowdsourcing the counting process to lay persons without previous expertise in ultrasound analysis. Materials and Methods Volunteers from around the world are encouraged to register on the website to help with this initiative. After registration the volunteer is prompted to watch an eight-minute training tutorial teaching them how to choose suitable frames in the videos, count VGE and submit their assessment. A volunteer is allowed to participate in the project once they have succeeded in completing a number of training videos in which they need to agree with the counts of professional graders. A database of 204 de-identified post-dive ultrasound videos of variable quality have been uploaded to the application. Results The application on www.decobubbles.com is active since February 2021 and at the beginning of March 2021 had registered 153 unique raters, 587 submitted ratings, and 34% of the 204 videos in the database were fully rated, which means that three independent raters agreed in their counting. Summary/Conclusion This collaborative platform will allow refinement of an Al to count VGE in post-dive echocardiography recordings and advance the knowledge about inter­and intrasubjectVGE variability in divers. Future implications include the possibility for researchers to use the platform to directly analyze their own datasets - with no obligation to add these to our database, although we welcome more videos from other sources and collaborators. This research is funded through the Divers Alert Network (#DAN-UNC-1) and the Office of Naval Research (ONR #N00014-20-1-2590)