Publications by authors named "Frauke Tillmans"

9 Publications

  • Page 1 of 1

Incidence of cardiac arrhythmias and left ventricular hypertrophy in recreational scuba divers.

Diving Hyperb Med 2021 Jun;51(2):190-198

Divers Alert Network, Durham, North Carolina, USA.

Introduction: The aims of this study were to investigate the potential impact of age, sex and body mass index (BMI) upon the incidence of arrhythmias pre- and post- diving, and to identify the prevalence of left ventricular hypertrophy (LVH) in older recreational divers.

Methods: Divers aged ≥ 40 years participating in group dive trips had ECG rhythm and echocardiograph recordings before and after diving. Arrhythmias were confirmed by an experienced human reader. LVH was identified by two-dimensional echocardiography. Weighted (0.5 fractional) values were used to account for participation by seven divers in 14 trips.

Results: Seventy-seven divers undertook 84 dive trips and recorded 677 dives. Among divers with no pre-trip arrhythmias (n = 55), we observed that 6.5 (12%) recorded post-trip arrhythmias and the median increase was 1.0 arrhythmia. In divers with pre-trip arrhythmias, 14.5 had a median of 1.0 fewer post-trip arrhythmias, 2.0 had no change and 5.5 had a median of 16.0 greater. Age, but neither sex nor BMI, was associated with change in the number of arrhythmias before and after dive trips (P = 0.02). The relative risk for experiencing a change in the frequency of arrhythmias after a diver trip, was 2.1 for each additional 10 years of age (95% CI 1.1, 4.0). Of the 60 divers with imaging of their heart, five had left ventricular hypertrophy.

Conclusions: We observed a higher than expected prevalence of arrhythmias. Divers with pre-trip arrhythmias tended to be older than divers without pre-trip arrhythmias (P = 0.02). The prevalence of LVH in our cohort was one quarter of that found post-mortem in scuba fatalities.
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http://dx.doi.org/10.28920/dhm51.2.190-198DOI Listing
June 2021

A fully automated method for late ventricular diastole frame selection in post-dive echocardiography without ECG gating.

Undersea Hyperb Med 2021 First Quarter;48(1):73-80

Joint Department of Biomedical Engineering, The University of North Carolina at Chapel Hill and North Carolina State University, Chapel Hill, North Carolina, U.S.

Venous gas emboli (VGE) are often quantified as a marker of decompression stress on echocardiograms. Bubble-counting has been proposed as an easy to learn method, but remains time-consuming, rendering large dataset analysis impractical. Computer automation of VGE counting following this method has therefore been suggested as a means to eliminate rater bias and save time. A necessary step for this automation relies on the selection of a frame during late ventricular diastole (LVD) for each cardiac cycle of the recording. Since electrocardiograms (ECG) are not always recorded in field experiments, here we propose a fully automated method for LVD frame selection based on regional intensity minimization. The algorithm is tested on 20 previously acquired echocardiography recordings (from the original bubble-counting publication), half of which were acquired at rest (Rest) and the other half after leg flexions (Flex). From the 7,140 frames analyzed, sensitivity was found to be 0.913 [95% CI: 0.875-0.940] and specificity 0.997 [95% CI: 0.996-0.998]. The method's performance is also compared to that of random chance selection and found to perform significantly better (p≺0.0001). No trend in algorithm performance was found with respect to VGE counts, and no significant difference was found between Flex and Rest (p>0.05). In conclusion, full automation of LVD frame selection for the purpose of bubble counting in post-dive echocardiography has been established with excellent accuracy, although we caution that high quality acquisitions remain paramount in retaining high reliability.
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March 2021

Ultrasound in decompression research: fundamentals, considerations, and future technologies.

Undersea Hyperb Med 2021 First Quarter;48(1):59-72

Joint Department of Biomedical Engineering, The University of North Carolina at Chapel Hill and North Carolina State University, Chapel Hill, North Carolina, U.S.

It is widely accepted that bubbles are a necessary but insufficient condition for the development of decompression sickness. However, open questions remain regarding the precise formation and behavior of these bubbles after an ambient pressure reduction (decompression), primarily due to the inherent difficulty of directly observing this phenomenon in vivo. In decompression research, information about these bubbles after a decompression is gathered via means of ultrasound acquisitions. The ability to draw conclusions regarding decompression research using ultrasound is highly influenced by the variability of the methodologies and equipment utilized by different research groups. These differences play a significant role in the quality of the data and thus the interpretation of the results. The purpose of this review is to provide a technical overview of the use of ultrasound in decompression research, particularly Doppler and brightness (B)-mode ultrasound. Further, we will discuss the strengths and limitations of these technologies and how new advancements are improving our ability to understand bubble behavior post-decompression.
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March 2021

Hyperoxia Alters Ultrastructure and Induces Apoptosis in Leukemia Cell Lines.

Biomolecules 2020 02 12;10(2). Epub 2020 Feb 12.

Environmental & Occupational Physiology Laboratory, Haute Ecole Bruxelles-Brabant, 1180 Brussels, Belgium.

Oxygenation conditions are crucial for growth and tumor progression. Recent data suggests a decrease in cancer cell proliferation occurring after exposure to normobaric hyperoxia. Those changes are associated with fractal dimension. The purpose of this research was to study the impact of hyperoxia on apoptosis and morphology of leukemia cell lines. Two hematopoietic lymphoid cancer cell lines (a T-lymphoblastoid line, JURKAT and a B lymphoid line, CCRF-SB) were tested under conditions of normobaric hyperoxia (FiO > 60%, ± 18h) and compared to a standard group (FiO = 21%). We tested for apoptosis using a caspase-3 assay. Cell morphology was evaluated by cytospin, microphotography after coloration, and analysis by a fractal dimension calculation software. Our results showed that exposure of cell cultures to transient normobaric hyperoxia induced apoptosis (elevated caspase-3) as well as significant and precocious modifications in cell complexity, as highlighted by increased fractal dimensions in both cell lines. These features are associated with changes in structure (pycnotic nucleus and apoptosis) recorded by microscopic analysis. Such morphological alterations could be due to several molecular mechanisms and rearrangements in the cancer cell, leading to cell cycle inhibition and apoptosis as shown by caspase-3 activity. T cells seem less resistant to hyperoxia than B cells.
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http://dx.doi.org/10.3390/biom10020282DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7072400PMC
February 2020

Effect of hyperoxia on the immune status of oxygen divers and endurance athletes.

Free Radic Res 2019 May 23;53(5):522-534. Epub 2019 May 23.

a Naval Institute for Maritime Medicine , Kronshagen , Germany.

Physical activity, particularly that, exerted by endurance athletes, impacts the immune status of the human body. Prolonged duration and high-intensity endurance training lead to increased production of reactive oxygen species (ROS) and thereby to oxidative stress. Military combat swimmers (O-divers) are regularly exposed to hyperbaric hyperoxia (HBO) in addition to intensive endurance training intervals. They are, therefore, exposed to extreme levels of oxidative stress. Several studies support that the intensity of oxidative stress essentially determines the effect on immune status. The aim of this study was to comparatively characterise peripheral blood mononuclear cells (PBMCs) of O-divers (military combat swimmers), endurance athletes (amateur triathletes), and healthy control volunteers with respect to DNA fragmentation, immune status and signs of inflammation. Furthermore, it was investigated how PBMCs from these groups responded acutely to exposure to HBO. We showed that DNA fragmentation was comparable in PBMCs of all three groups under basal conditions directly after HBO exposure. However, significantly higher DNA fragmentation was observed in O-divers 18 hours after HBO, possibly indicating a slower recovery. O-divers also exhibited a proinflammatory immune status exemplified by an elevated number of CD4CD25 T cells, elevated expression of proinflammatory cytokine IL-12, and diminished expression of anti-inflammatory TGF-β1 compared to controls. Supported by a decreased basal gene expression and prolonged upregulation of anti-oxidative HO-1, these data suggest that higher oxidative stress levels, as present under intermitted hyperbaric hyperoxia, e.g. through oxygen diving, promote a higher inflammatory immune status than oxidative stress through endurance training alone.
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http://dx.doi.org/10.1080/10715762.2019.1612890DOI Listing
May 2019

Decompression illness with hypovolemic shock and neurological failure symptoms after two risky dives: a case report.

Physiol Rep 2017 Mar;5(6)

Section for Maritime Medicine, Institute of Experimental Medicine Christian-Albrechts-University Kiel c/o German Naval Medical Institute, Kopperpahler Allee 120, Kronshagen, 24119, Germany.

Hypovolemia is known to be a predisposing factor of decompression illness (DCI) while diving. The typical clinically impressive neurological symptoms of DCI may distract from other symptoms such as an incipient hypovolemic shock. We report the case of a 61-year-old male Caucasian, who presented with an increasing central and peripheral neural failure syndrome and massive hypovolemia after two risky dives. Computed tomography (CT) scans of the chest and Magnetic resonance imaging scans of the head revealed multiple cerebral and pulmonary thromboembolisms. Transesophageal echocardiography showed a patent foramen ovale (PFO). Furthermore, the patient displayed hypotension as well as prerenal acute kidney injury with elevated levels of creatinine and reduced renal clearance, indicating a hypovolemic shock. Early hyperbaric oxygen (HBO) therapy reduced the neurological deficits. After volume expansion of 11 liters of electrolyte solution (1000 mL/h) the cardiopulmonary and renal function normalized. Hypovolemia increases the risk of DCI during diving and that of hypovolemic shock. Early HBO therapy and fluid replacement is crucial for a favorable outcome.
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http://dx.doi.org/10.14814/phy2.13094DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5371546PMC
March 2017

Call for a multicenter study on the intra-subject variability of venous gas emboli.

Undersea Hyperb Med 2017 Sept-Oct;44(5):377

Divers Alert Network, Durham, NC, U.S.

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July 2018

From theory to bench confirmation or from bench to theory.

Intensive Care Med Exp 2016 Dec 9;4(1):39. Epub 2016 Dec 9.

Département de Réanimation Médicale et de Médecine Hyperbare, Centre Hospitalier Universitaire, Angers, Cedex 9, 49933, France.

In this commentary, the authors discuss two possible approaches in experimental studies. The first approach is to replicate an experimentation in order to confirm or not previously published results. The second one is more theoretical and consists in estimating the expected effect of all the components of the problem. When theoretical calculations suggest a theoretical failure that contradicts previous published results, investigators are between a rock and a hard place. Indeed, how can already published data and theoretical likelihood of failure be reconciled?
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http://dx.doi.org/10.1186/s40635-016-0113-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5148755PMC
December 2016

Dark chocolate reduces endothelial dysfunction after successive breath-hold dives in cool water.

Eur J Appl Physiol 2013 Dec;113(12):2967-75

Objective: The aim of this study is to observe the effects of dark chocolate on endothelial function after a series of successive apnea dives in non-thermoneutral water.

Methods: Twenty breath-hold divers were divided into two groups: a control group (8 males and 2 females) and a chocolate group (9 males and 1 female). The control group was asked to perform a series of dives to 20 m adding up to 20 min in the quiet diving pool of Conflans-Ste-Honorine (Paris, France), water temperature was 27 °C. The chocolate group performed the dives 1 h after ingestion of 30 g of dark chocolate. Flow-mediated dilatation (FMD), digital photoplethysmography, nitric oxide (NO), and peroxynitrite ONOO−) levels were measured before and after each series of breath-hold dives.

Results: A significant decrease in FMD was observed in the control group after the dives (95.28 ± 2.9 % of pre-dive values, p < 0.001) while it was increased in the chocolate group (104.1 ± 2.9 % of pre-dive values, p < 0.01). A decrease in the NO level was observed in the control group (86.76 ± 15.57 %, p < 0.05) whereas no difference was shown in the chocolate group (98.44 ± 31.86 %, p > 0.05). No differences in digital photoplethysmography and peroxynitrites were observed between before and after the dives.

Conclusion: Antioxidants contained in dark chocolate scavenge free radicals produced during breath-hold diving. Ingestion of 30 g of dark chocolate 1 h before the dive can thus prevent endothelial dysfunction which can be observed after a series of breath-hold dives.
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http://dx.doi.org/10.1007/s00421-013-2732-6DOI Listing
December 2013
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