Evolution of military evacuation activity in French Guiana over 10 years: a retrospective observational study

BACKGROUND

Three permanent military operations are established in French Guiana. The Cayenne medical unit is a French military search and rescue unit and provides MEDEVAC and CASEVAC for ill and injured soldiers. The main objective of this study was to describe the temporal trends of its evacuation missions over 10 years. The secondary purpose was to document the means used for these missions.

METHODS

This retrospective observational study included patients who were evacuated for a medical reason or an injury during military operations in French Guiana. We collected the data from the computerised registers the medical department had stored.

RESULTS

From 1 January 2010 to 31 December 2019, 1070 patients were included, representing a median annual incidence of 115 (IQR 91-122) evacuations. Of these, 602 (59%) were evacuated by helicopter, 214 (21%) by airplane, 182 (18%) by ambulance and 19 (2%) by pirogue.Reasons for evacuation were diseases in 664 (62%) patients, non-battle injuries in 389 (36%) patients and battle injuries in 17 (2%) patients. Finally, 286 (29%) evacuations were MEDEVAC and 712 (71%) were CASEVAC.Over the years, the increasing number of evacuations reached a maximum of 183 in 2018. Helicopter evacuations, once the primary mode of evacuation, have declined proportionately in favour of other means of evacuation.

CONCLUSION

Evacuation missions by the Cayenne medical unit increased over the 10-year study period, while helicopter use decreased. This evolution is a response to the constraints of adapting military operations to fight against illegal gold mining in the Amazonian Forest. Improvement of the means and procedures allows provision of the best care to patients while ensuring the ongoing conduct of military operations.

Low Temperature Dynamic Polaron Liquid in a Manganite Exhibiting Colossal Magnetoresistance

Polarons-fermionic charge carriers bearing a strong companion lattice deformation-exhibit a natural tendency for self-localization due to the recursive interaction between electrons and the lattice. While polarons are ubiquitous in insulators, how they evolve in transitions to metallic and superconducting states in quantum materials remains an open question. Here, we use resonant inelastic x-ray scattering to track the electron-lattice coupling in the colossal magneto-resistive bi-layer manganite La_{1.2}Sr_{1.8}Mn_{2}O_{7} across its metal-to-insulator transition. The response in the insulating high-temperature state features harmonic emissions of a dispersionless oxygen phonon at small energy transfer. Upon cooling into the metallic state, we observe a drastic redistribution of spectral weight from the region of these harmonic emissions to a broad high energy continuum. In concert with theoretical calculations, we show that this evolution implies a shift in electron-lattice coupling from static to dynamic lattice distortions that leads to a distinct polaronic ground state in the low temperature metallic phase-a dynamic polaron liquid.

Comparison of mannitol and hypertonic saline solution for the treatment of suspected brain herniation during prehospital management of traumatic brain injury patients

BACKGROUND AND IMPORTANCE

Occurrence of mydriasis during the prehospital management of traumatic brain injury (TBI) may suggest severe intracranial hypertension (ICH) subsequent to brain herniation. The initiation of hyperosmolar therapy to reduce ICH and brain herniation is recommended. Whether mannitol or hypertonic saline solution (HSS) should be preferred is unknown.

OBJECTIVES

The objective of this study is to assess whether HSS, compared with mannitol, is associated with improved survival in adult trauma patients with TBI and mydriasis.

DESIGN/SETTING AND PARTICIPANTS

A retrospective observational cohort study using the French Traumabase national registry to compare the ICU mortality of patients receiving either HSS or mannitol. Patients aged 16 years or older with moderate to severe TBI who presented with mydriasis during prehospital management were included.

OUTCOME MEASURES AND ANALYSIS

We performed propensity score matching on a priori selected variables [i.e. age, sex and initial Coma Glasgow Scale (GCS)] with a ratio of 1 : 3 to ensure comparability between the two groups. The primary outcome was ICU mortality. The secondary outcomes were regression of pupillary abnormality during prehospital management, pulsatility index and diastolic velocity on transcranial Doppler within 24 h after TBI, early ICU mortality (within 48 h), ICU and hospital length of stay.

RESULTS

Of 31 579 patients recorded in the registry between 2011 and 2021, 1417 presented with prehospital mydriasis and were included: 1172 (82.7%) received mannitol and 245 (17.3%) received HSS. After propensity score matching, 720 in the mannitol group matched 240 patients in the HSS group. Median age was 41 years [interquartile ranges (IQR) 26-60], 1058 were men (73%) and median GCS was 4 (IQR 3-6). No significant difference was observed in terms of characteristics and prehospital management between the two groups. ICU mortality was lower in the HSS group (45%) than in the mannitol group (54%) after matching [odds ratio (OR) 0.68 (0.5-0.9), P = 0.014]. No differences were identified between the groups in terms of secondary outcomes.

CONCLUSION

In this propensity-matched observational study, the prehospital osmotherapy with HSS in TBI patients with prehospital mydriasis was associated with a lower ICU mortality compared to osmotherapy with mannitol.

Controlled donation after circulatory death in post-cardiac arrest patients: Estimates from a large registry

BACKGROUND

Controlled donation after circulatory death (cDCD) in post-anoxic brain injury is a valuable source of organs that is still underused in some countries. We assessed the number of potential cDCD donors after out-of-hospital cardiac arrest (OHCA) in Paris and its suburbs and extrapolated the results to the French population.

METHODS

Using the large regional registry of the Great Paris area, we prospectively included all consecutive adults with OHCA with a stable return of spontaneous circulation (ROSC) who ultimately died in the intensive care unit (ICU) after withdrawal of life-sustaining treatments (WLST) due to post anoxic brain injury. The primary endpoint was potential for organ donation by cDCD in this population. The number of potential cDCD donors was calculated and extrapolated to the entire French population.

RESULTS

Between 2011 and 2018, 4638 patients with stable ROSC were admitted to ICUs after OHCA, and 3170 died in ICU, of which 1034 died after WLST due to post-anoxic brain injury. When considering French criteria, 421/1034 patients (41%) would have been potential cDCD donors (55 patients per year in a 4.67 million population). After standardization for age and sex, the potential for cDCD was 515 (95% CI 471-560) patients per year in France corresponding to an annual incidence of 1.18 per 100 000 inhabitants per year.

CONCLUSIONS

Organ donation by cDCD after cardiac arrest could provide a large pool of donors in France.

Psychological, cognitive, and physiological impact of hazards casualties' trainings on first responders: the example of a chemical and radiological training. An exploratory study

Background

First responders are among the first to respond to hazards casualties. They might operate in volatile, uncertain, complex, and ambiguous (VUCA) environments. While they have underlined the need to improve their knowledge and training to face these environments, there are few data regarding the stress induced by these trainings. Chemical, biological, radiological, and nuclear (CBRN) hazards casualties' trainings seem to be a good model of "in vivo" stress. First responders must operate in a hostile and encountered environment with a CBRN protective equipment that places demand on their psychological, cognitive, and physiological capacities. Current research recognizes that the activity of the parasympathetic system (PSS) can be used as an objective marker of stress adaptation, measured as heart rate variability (HRV).

Objectives

To compare between baseline and simulation the evolution of the parasympathetic activity (primary outcome), anxiety, emotions, cognitive load, and body posture awareness (secondary outcomes).

Methods

A total of 28 first responders attended to three simulated scenarios requiring CBRN management of casualties. One day before simulation, we collected HRV data (baseline). The simulations' day (pre-, post-simulation) we collected anxiety score (STAI-Y B), emotions (SPANE), cognitive load (NASA TLX), body posture awareness (PAS) and HRV. The morning after we collected the PAS score (recovery). We compare data' evolution between different times of the simulation.

Results

(i) A high level of anxiety at baseline [Median 51 (46; 56)] which decreased between pre- and post-simulation (p = 0.04; F = 2.93); (ii) a post-simulation decrease in negative feelings (p = 0.03); (iii) a decrease in body awareness after simulation which returned to the initial level at recovery (p = 0.03; F = 3.48); (iv) a decrease in mean RR between baseline, pre- and post-simulation (p = 0.009; F = 5.11). There were no significant difference between times on others analysis of HRV.

Conclusion

Prior to simulation, participants experienced anticipatory anxiety. Simulations training practiced regularly could be one way to combat anticipatory anxiety.

Cumulative dose of epinephrine and mode of death after non-shockable out-of-hospital cardiac arrest: a registry-based study

BACKGROUND

Epinephrine increases the chances of return of spontaneous circulation (ROSC) in out-of-hospital cardiac arrest (OHCA), especially when the initial rhythm is non-shockable. However, this drug could also worsen the post-resuscitation syndrome (PRS). We assessed the association between epinephrine use during cardiopulmonary resuscitation (CPR) and subsequent intensive care unit (ICU) mortality in patients with ROSC after non-shockable OHCA.

METHODS

We used data prospectively collected in the Sudden Death Expertise Center (SDEC) registry (capturing OHCA data located in the Greater Paris area, France) between May 2011 and December 2021. All adults with ROSC after medical, cardiac and non-cardiac causes, non-shockable OHCA admitted to an ICU were included. The mode of death in the ICU was categorized as cardiocirculatory, neurological, or other.

RESULTS

Of the 2,792 patients analyzed, there were 242 (8.7%) survivors at hospital discharge, 1,004 (35.9%) deaths from cardiocirculatory causes, 1,233 (44.2%) deaths from neurological causes, and 313 (11.2%) deaths from other etiologies. The cardiocirculatory death group received more epinephrine (4.6 ± 3.8 mg versus 1.7 ± 2.8 mg, 3.2 ± 2.6 mg, and 3.5 ± 3.6 mg for survivors, neurological deaths, and other deaths, respectively; p < 0.001). The proportion of cardiocirculatory death increased linearly (R2 = 0.92, p < 0.001) with cumulative epinephrine doses during CPR (17.7% in subjects who did not receive epinephrine and 62.5% in those who received > 10 mg). In multivariable analysis, a cumulative dose of epinephrine was strongly associated with cardiocirculatory death (adjusted odds ratio of 3.45, 95% CI [2.01-5.92] for 1 mg of epinephrine; 12.28, 95% CI [7.52-20.06] for 2-5 mg; and 23.71, 95% CI [11.02-50.97] for > 5 mg; reference 0 mg; population reference: alive at hospital discharge), even after adjustment on duration of resuscitation. The other modes of death (neurological and other causes) were also associated with epinephrine use, but to a lesser extent.

CONCLUSIONS

In non-shockable OHCA with ROSC, the dose of epinephrine used during CPR is strongly associated with early cardiocirculatory death. Further clinical studies aimed at limiting the dose of epinephrine during CPR seem warranted. Moreover, strategies for the prevention and management of PRS should take this dose of epinephrine into consideration for future trials.

Transcription induces context-dependent remodeling of chromatin architecture during differentiation

Metazoan chromosomes are organized into discrete spatial domains (TADs), believed to contribute to the regulation of transcriptional programs. Despite extensive correlation between domain organization and gene activity, a direct mechanistic link is unclear, with perturbation studies often showing little effect. To follow chromatin architecture changes during development, we used Capture Hi-C to interrogate the domains around key differentially expressed genes during mouse thymocyte maturation, uncovering specific remodeling events. Notably, one TAD boundary was broadened to accommodate RNA polymerase elongation past the border, and subdomains were formed around some activated genes without changes in CTCF binding. The ectopic induction of some genes was sufficient to recapitulate domain formation in embryonic stem cells, providing strong evidence that transcription can directly remodel chromatin structure. These results suggest that transcriptional processes drive complex chromosome folding patterns that can be important in certain genomic contexts.

Improving EMS response times for out-of-hospital cardiac arrest in urban areas using drone-like vertical take-off and landing air ambulances: An international, simulation-based cohort study

BACKGROUND

Advances in vertical take-off and landing (VTOL) technologies may enable drone-like crewed air ambulances to rapidly respond to out-of-hospital cardiac arrest (OHCA) in urban areas. We estimated the impact of incorporating VTOL air ambulances on OHCA response intervals in two large urban centres in France and Canada.

METHODS

We included adult OHCAs occurring between Jan. 2017-Dec. 2018 within Greater Paris in France and Metro Vancouver in Canada. Both regions utilize tiered OHCA response with basic (BLS)- and advanced life support (ALS)-capable units. We simulated incorporating 1-2 ALS-capable VTOL air ambulances dedicated to OHCA response in each study region, and computed time intervals from call reception by emergency medical services (EMS) to arrival of the: (1) first ALS unit ("call-to-ALS arrival interval"); and (2) first EMS unit ("call-to-first EMS arrival interval").

RESULTS

There were 6,217 OHCAs included during the study period (3,760 in Greater Paris and 2,457 in Metro Vancouver). Historical median call-to-ALS arrival intervals were 21 min [IQR 16-29] in Greater Paris and 12 min [IQR 9-17] in Metro Vancouver, while median call-to-first EMS arrival intervals were 11 min [IQR 8-14] and 7 min [IQR 5-8] respectively. Incorporating 1-2 VTOL air ambulances improved median call-to-ALS arrival intervals to 7-9 min and call-to-first EMS arrival intervals to 6-8 min in both study regions (all P < 0.001).

CONCLUSION

VTOL air ambulances dedicated to OHCA response may improve EMS response intervals, with substantial improvements in ALS response metrics.

Trends in survival from out-of-hospital cardiac arrest with a shockable rhythm and its association with bystander resuscitation: a retrospective study

OBJECTIVE

Over 300 000 cases of out-of-hospital cardiac arrests (OHCAs) occur each year in the USA and Europe. Despite decades of investment and research, survival remains disappointingly low. We report the trends in survival after a ventricular fibrillation/pulseless ventricular tachycardia OHCA, over a 13-year period, in a French urban region, and describe the simultaneous evolution of the rescue system.

METHODS

We investigated four 18-month periods between 2005 and 2018. The first period was considered baseline and included patients from the randomised controlled trial 'DEFI 2005'. The three following periods were based on the Paris Sudden Death Expertise Center Registry (France). Inclusion criteria were non-traumatic cardiac arrests treated with at least one external electric shock with an automated external defibrillator from the basic life support team and resuscitated by a physician-staffed ALS team. Primary outcome was survival at hospital discharge with a good neurological outcome.

RESULTS

Of 21 781 patients under consideration, 3476 (16%) met the inclusion criteria. Over all study periods, survival at hospital discharge increased from 12% in 2005 to 25% in 2018 (p<0.001), and return of spontaneous circulation at hospital admission increased from 43% to 58% (p=0.004).Lay-rescuer cardiopulmonary resuscitation (CPR) and telephone CPR (T-CPR) rates increased significantly, but public defibrillator use remained limited.

CONCLUSION

In a two-tiered rescue system, survival from OHCA at hospital discharge doubled over a 13-year study period. Concomitantly, the system implemented an OHCA patient registry and increased T-CPR frequency, despite a consistently low rate of public defibrillator use.

FIRECARE: An Evidence-Based Prevention Program to Reduce Burnout among Prehospital Caregivers: Benefits of a Combined Mindfulness, Heart Coherence Training, and Positive Psychology Intervention

BACKGROUND

Burnout among emergency health care professionals is well-described, especially during the COVID-19 pandemic. Prevention interventions, such as mindfulness, focus on the management of stress.

OBJECTIVE

To evaluate the effects of the FIRECARE program (a mindfulness intervention, supplemented by heart coherence training and positive psychology workshops) on burnout, secondary stress, compassion fatigue, and mindfulness among advanced life support ambulance staff of the Paris Fire Brigade.

MATERIALS AND METHODS

We used a non-randomized, two-group quasi-experimental study design with a waitlist control and before-and-after measurements in each group. The intervention consisted of six, once-weekly, 2.5-h sessions that included individual daily meditation and cardiac coherence practice. The study compared intervention and waitlist control groups, and investigated baseline, post-program, and 3-month follow-up change on burnout (measuring using the ProQOL-5 scale) and mindfulness (measuring using the FMI scores). Baseline burnout (measured using the ProQOL-5) was evaluated and used in the analysis.

RESULTS

Seventy-four 74 participants volunteered to participate; 66 were included in the final analysis. Of these, 60% were classified as suffering from moderate burnout, the 'burnout cluster'. A comparison of intervention and waitlist control groups found a decrease in the burnout score in the burnout cluster (p = 0.0003; partial eta squared = 0.18). However, while secondary stress fell among the burnout cluster, it was only for participants in the intervention group; scores increased for those in the waitlist group (p = 0.003; partial eta squared = 0.12). The pre-post-intervention analysis of both groups also showed that burnout fell in the burnout cluster (p = 0.006; partial eta squared = 0.11). At 3-month follow-up, the burnout score was significantly reduced in the intervention group (p = 0.02; partial eta squared = 0.07), and both the acceptance (p = 0.007) and mindfulness scores (p = 0.05; partial eta squared = 0.05) were increased in the baseline burnout cluster.

CONCLUSION

FIRECARE may be a useful approach to preventing and reducing burnout among prehospital caregivers.

HP1-driven phase separation recapitulates the thermodynamics and kinetics of heterochromatin condensate formation

The spatial segregation of pericentromeric heterochromatin (PCH) into distinct, membrane-less nuclear compartments involves the binding of Heterochromatin Protein 1 (HP1) to H3K9me2/3-rich genomic regions. While HP1 exhibits liquid-liquid phase separation properties in vitro, its mechanistic impact on the structure and dynamics of PCH condensate formation in vivo remains largely unresolved. Here, using a minimal theoretical framework, we systematically investigate the mutual coupling between self-interacting HP1-like molecules and the chromatin polymer. We reveal that the specific affinity of HP1 for H3K9me2/3 loci facilitates coacervation in nucleo and promotes the formation of stable PCH condensates at HP1 levels far below the concentration required to observe phase separation in purified protein assays in vitro. These heterotypic HP1-chromatin interactions give rise to a strong dependence of the nucleoplasmic HP1 density on HP1-H3K9me2/3 stoichiometry, consistent with the thermodynamics of multicomponent phase separation. The dynamical cross talk between HP1 and the viscoelastic chromatin scaffold also leads to anomalously slow equilibration kinetics, which strongly depend on the genomic distribution of H3K9me2/3 domains and result in the coexistence of multiple long-lived, microphase-separated PCH compartments. The morphology of these complex coacervates is further found to be governed by the dynamic establishment of the underlying H3K9me2/3 landscape, which may drive their increasingly abnormal, aspherical shapes during cell development. These findings compare favorably to 4D microscopy measurements of HP1 condensate formation in live Drosophila embryos and suggest a general quantitative model of PCH formation based on the interplay between HP1-based phase separation and chromatin polymer mechanics.

Mobile blood depots in ground ambulances in compliance with French legislation: A feasibility study

BACKGROUND

Prehospital transfusion is a way of improving the management of hemorrhagic shock. In France, prehospital transfusion is struggling to develop, both because of logistical difficulties and particularly restrictive legislation. To comply with this, we propose to store the blood products (BPs) in ground ambulances with refrigerated boxes allowing remote continuous monitoring of storage conditions, called "NelumBox" (Tec4med Lifescience GmbH). To open them, the ambulance's team needs a code that is only given by the Transfusion Center if the request meets all required regulatory criteria.

STUDY DESIGN AND METHODS

We conducted a prospective simulation-based feasibility study using dummy BPs. Two ambulances were equipped. Simulations were triggered unexpectedly, including during on-call hours. The ability to quickly access the BPs was the main judgment criterion. The quality of hemovigilance during these simulations was also examined.

RESULTS

Twenty-two simulations were performed. The ambulance's team was able to access the BPs in 100% of cases. The average waiting time for receiving the unlocking code was 5 min 27 s (SD = 2 min 12 s, MAX = 12 min 00 s). The transfusion traceability was compliant with regulations in 100% of cases. The transfusion center was able to remotely monitor BPs storage conditions for the entire duration of their stockage in the NelumBox.

DISCUSSION

The present procedure is efficient, repeatable, and fast. It guarantees a strict transfusion safety without slowdown a severe trauma management, while complying with French regulations.

Biophysical ordering transitions underlie genome 3D re-organization during cricket spermiogenesis

Spermiogenesis is a radical process of differentiation whereby sperm cells acquire a compact and specialized morphology to cope with the constraints of sexual reproduction while preserving their main cargo, an intact copy of the paternal genome. In animals, this often involves the replacement of most histones by sperm-specific nuclear basic proteins (SNBPs). Yet, how the SNBP-structured genome achieves compaction and accommodates shaping remain largely unknown. Here, we exploit confocal, electron and super-resolution microscopy, coupled with polymer modeling to identify the higher-order architecture of sperm chromatin in the needle-shaped nucleus of the emerging model cricket Gryllus bimaculatus. Accompanying spermatid differentiation, the SNBP-based genome is strikingly reorganized as ~25nm-thick fibers orderly coiled along the elongated nucleus axis. This chromatin spool is further found to achieve large-scale helical twisting in the final stages of spermiogenesis, favoring its ultracompaction. We reveal that these dramatic transitions may be recapitulated by a surprisingly simple biophysical principle based on a nucleated rigidification of chromatin linked to the histone-to-SNBP transition within a confined nuclear space. Our work highlights a unique, liquid crystal-like mode of higher-order genome organization in ultracompact cricket sperm, and establishes a multidisciplinary methodological framework to explore the diversity of non-canonical modes of DNA organization.

Factors associated with circulatory death after out-of-hospital cardiac arrest: a population-based cluster analysis

BACKGROUND

Out-of-hospital cardiac arrest (OHCA) is a common cause of death. Early circulatory failure is the most common reason for death within the first 48 h. This study in intensive care unit (ICU) patients with OHCA was designed to identify and characterize clusters based on clinical features and to determine the frequency of death from refractory postresuscitation shock (RPRS) in each cluster.

METHODS

We retrospectively identified adults admitted alive to ICUs after OHCA in 2011-2018 and recorded in a prospective registry for the Paris region (France). We identified patient clusters by performing an unsupervised hierarchical cluster analysis (without mode of death among the variables) based on Utstein clinical and laboratory variables. For each cluster, we estimated the hazard ratio (HRs) for RPRS.

RESULTS

Of the 4445 included patients, 1468 (33%) were discharged alive from the ICU and 2977 (67%) died in the ICU. We identified four clusters: initial shockable rhythm with short low-flow time (cluster 1), initial non-shockable rhythm with usual absence of ST-segment elevation (cluster 2), initial non-shockable rhythm with long no-flow time (cluster 3), and long low-flow time with high epinephrine dose (cluster 4). RPRS was significantly associated with this last cluster (HR, 5.51; 95% confidence interval 4.51-6.74).

CONCLUSIONS

We identified patient clusters based on Utstein criteria, and one cluster was strongly associated with RPRS. This result may help to make decisions about using specific treatments after OHCA.

Polarized tip-enhanced Raman spectroscopy at liquid He temperature in ultrahigh vacuum using an off-axis parabolic mirror

Tip-enhanced Raman spectroscopy (TERS) combines inelastic light scattering well below the diffraction limit down to the nanometer range and scanning probe microscopy and, possibly, spectroscopy. In this way, topographic and spectroscopic as well as single- and two-particle information may simultaneously be collected. While single molecules can now be studied successfully, bulk solids are still not meaningfully accessible. It is the purpose of the work presented here to outline approaches toward this objective. We describe a home-built, liquid helium cooled, ultrahigh vacuum TERS. The setup is based on a scanning tunneling microscope and, as an innovation, an off-axis parabolic mirror having a high numerical aperture of ∼0.85 and a large working distance. The system is equipped with a fast load-lock chamber, a chamber for the in situ preparation of tips, substrates, and samples, and a TERS chamber. Base pressure and temperature in the TERS chamber were ∼3 × 10-11 mbar and 15 K, respectively. Polarization dependent tip-enhanced Raman spectra of the vibration modes of carbon nanotubes were successfully acquired at cryogenic temperature. The new features described here including very low pressure and temperature and the external access to the light polarizations, thus the selection rules, may pave the way toward the investigation of bulk and surface materials.

4D epigenomics: deciphering the coupling between genome folding and epigenomic regulation with biophysical modeling

Recent experimental observations suggest a strong coupling between the 3D nuclear chromosome organization and epigenomics. However, the mechanistic and functional bases of such interplay remain elusive. In this review, we describe how biophysical modeling has been instrumental in characterizing how genome folding may impact the formation of epigenomic domains and, conversely, how epigenomic marks may affect chromosome conformation. Finally, we discuss how this mutual feedback loop between chromatin organization and epigenome regulation, via the formation of physicochemical nanoreactors, may represent a key functional role of 3D compartmentalization in the assembly and maintenance of stable - but yet plastic - epigenomic landscapes.

Geometric frustration of Jahn-Teller order in the infinite-layer lattice

The Jahn-Teller effect, in which electronic configurations with energetically degenerate orbitals induce lattice distortions to lift this degeneracy, has a key role in many symmetry-lowering crystal deformations¹. Lattices of Jahn-Teller ions can induce a cooperative distortion, as exemplified by LaMnO₃ (refs. ^2,3). Although many examples occur in octahedrally⁴ or tetrahedrally⁵ coordinated transition metal oxides due to their high orbital degeneracy, this effect has yet to be manifested for square-planar anion coordination, as found in infinite-layer copper^6,7, nickel^8,9, iron^10,11 and manganese oxides¹². Here we synthesize single-crystal CaCoO₂ thin films by topotactic reduction of the brownmillerite CaCoO_2.5 phase. We observe a markedly distorted infinite-layer structure, with ångström-scale displacements of the cations from their high-symmetry positions. This can be understood to originate from the Jahn-Teller degeneracy of the d_xz and d_yz orbitals in the d⁷ electronic configuration along with substantial ligand-transition metal mixing. A complex pattern of distortions arises in a [Formula: see text] tetragonal supercell, reflecting the competition between an ordered Jahn-Teller effect on the CoO₂ sublattice and the geometric frustration of the associated displacements of the Ca sublattice, which are strongly coupled in the absence of apical oxygen. As a result of this competition, the CaCoO₂ structure forms an extended two-in-two-out type of Co distortion following 'ice rules'¹³.

3DPolyS-LE: an accessible simulation framework to model the interplay between chromatin and loop extrusion

SUMMARY

Recent studies suggest that the loop extrusion activity of Structural Maintenance of Chromosomes complexes is central to proper organization of genomes in vivo. Polymer physics-based modeling of chromosome structure has been instrumental to assess which structures such extrusion can create. Only few laboratories however have the technical and computational expertise to create in silico models combining dynamic features of chromatin and loop extruders. Here, we present 3DPolyS-LE, a self-contained, easy to use modeling and simulation framework allowing non-specialists to ask how specific properties of loop extruders and boundary elements impact on 3D chromosome structure. 3DPolyS-LE also provides algorithms to compare predictions with experimental Hi-C data.

AVAILABILITY AND IMPLEMENTATION

Software available at https://gitlab.com/togop/3DPolyS-LE; implemented in Python and Fortran 2003 and supported on any Unix-based operating system (Linux and Mac OS).

SUPPLEMENTARY INFORMATION

Supplementary information are available at Bioinformatics online.

Differential Effect of Targeted Temperature Management Between 32 °C and 36 °C Following Cardiac Arrest According to Initial Severity of Illness: Insights From Two International Data Sets

BACKGROUND

Recent guidelines have emphasized actively avoiding fever to improve outcomes in patients who are comatose following resuscitation from cardiac arrest (ie, out-of-hospital cardiac arrest). However, whether targeted temperature management between 32 °C and 36 °C (TTM32-36) can improve neurologic outcome in some patients remains debated.

RESEARCH QUESTION

Is there an association between the use of TTM32-36 and outcome according to severity assessed at ICU admission using a previously derived risk score?

STUDY DESIGN AND METHODS

Data prospectively collected in the Sudden Death Expertise Center (SDEC) registry (France) between May 2011 and December 2017 and in the Resuscitation Outcomes Consortium Continuous Chest Compressions (ROC-CCC) trial (United States and Canada) between June 2011 and May 2015 were used for this study. Severity at ICU admission was assessed through a modified version of the Cardiac Arrest Hospital Prognosis (mCAHP) score, divided into tertiles of severity. The study explored associations between TTM32-36 and favorable neurologic status at hospital discharge by using multiple logistic regression as well as in tertiles of severity for each data set.

RESULTS

A total of 2,723 patients were analyzed in the SDEC data set and 4,202 patients in the ROC-CCC data set. A favorable neurologic status at hospital discharge occurred in 728 (27%) patients in the French data set and in 1,239 (29%) patients in the North American data set. Among the French data set, TTM32-36 was independently associated with better neurologic outcome in the tertile of patients with low (adjusted OR, 1.63; 95% CI, 1.15-2.30; P = .006) and high (adjusted OR, 1.94; 95% CI, 1.06-3.54; P = .030) severity according to mCAHP at ICU admission. Similar results were observed in the North American data set (adjusted ORs of 1.36 [95% CI, 1.05-1.75; P = .020] and 2.42 [95% CI, 1.38-4.24; P = .002], respectively). No association was observed between TTM32-36 and outcome in the moderate groups of the two data sets.

INTERPRETATION

TTM32-36 was significantly associated with a better outcome in patients with low and high severity at ICU admission assessed according to the mCAHP score. Further studies are needed to evaluate individualized temperature control following out-of-hospital cardiac arrest.

Dynamical modeling of the H3K27 epigenetic landscape in mouse embryonic stem cells

The Polycomb system via the methylation of the lysine 27 of histone H3 (H3K27) plays central roles in the silencing of many lineage-specific genes during development. Recent experimental evidence suggested that the recruitment of histone modifying enzymes like the Polycomb repressive complex 2 (PRC2) at specific sites and their spreading capacities from these sites are key to the establishment and maintenance of a proper epigenomic landscape around Polycomb-target genes. Here, to test whether such mechanisms, as a minimal set of qualitative rules, are quantitatively compatible with data, we developed a mathematical model that can predict the locus-specific distributions of H3K27 modifications based on previous biochemical knowledge. Within the biological context of mouse embryonic stem cells, our model showed quantitative agreement with experimental profiles of H3K27 acetylation and methylation around Polycomb-target genes in wild-type and mutants. In particular, we demonstrated the key role of the reader-writer module of PRC2 and of the competition between the binding of activating and repressing enzymes in shaping the H3K27 landscape around transcriptional start sites. The predicted dynamics of establishment and maintenance of the repressive trimethylated H3K27 state suggest a slow accumulation, in perfect agreement with experiments. Our approach represents a first step towards a quantitative description of PcG regulation in various cellular contexts and provides a generic framework to better characterize epigenetic regulation in normal or disease situations.

Painters in chromatin: a unified quantitative framework to systematically characterize epigenome regulation and memory

In eukaryotes, many stable and heritable phenotypes arise from the same DNA sequence, owing to epigenetic regulatory mechanisms relying on the molecular cooperativity of 'reader-writer' enzymes. In this work, we focus on the fundamental, generic mechanisms behind the epigenome memory encoded by post-translational modifications of histone tails. Based on experimental knowledge, we introduce a unified modeling framework, the painter model, describing the mechanistic interplay between sequence-specific recruitment of chromatin regulators, chromatin-state-specific reader-writer processes and long-range spreading mechanisms. A systematic analysis of the model building blocks highlights the crucial impact of tridimensional chromatin organization and state-specific recruitment of enzymes on the stability of epigenomic domains and on gene expression. In particular, we show that enhanced 3D compaction of the genome and enzyme limitation facilitate the formation of ultra-stable, confined chromatin domains. The model also captures how chromatin state dynamics impact the intrinsic transcriptional properties of the region, slower kinetics leading to noisier expression. We finally apply our framework to analyze experimental data, from the propagation of γH2AX around DNA breaks in human cells to the maintenance of heterochromatin in fission yeast, illustrating how the painter model can be used to extract quantitative information on epigenomic molecular processes.

Characteristics and factors associated to patients discharging from hospital without an implantable cardioverter defibrillator after out-of-hospital cardiac arrest

AIMS

Guidelines recommend that in the absence of reversible cause for sudden cardiac arrest (SCA), implantable cardioverter defibrillator (ICD) should be performed to prevent further fatal event. We sought to describe the frequency and characteristics of patients discharged from the hospital without ICD after the SCA in the daily practice.

METHODS AND RESULTS

From 2011 to 2018, all SCAs related to a cardiac cause admitted alive across the 48 hospitals of Great Paris Area were prospectively enrolled. Two investigators thoroughly reviewed each medical report to ensure accuracy of the assigned diagnosis towards identifying the cause of SCA and ICD implantation. Out of the 4314 SCA admitted alive at hospital admission, 1064 cardiac-related SCA survivors were discharged alive from hospital, including 356 patients (33.5%) with an ICD and 708 (66.5%) without. The principal underlying cause of SCA among those discharged without an ICD was acute coronary syndrome (ACS; 602, 85%), chronic coronary artery disease (41, 5.8%), structural non-ischaemic heart disease (48, 6.8%), and non-structural heart disease (17, 2.4%). Among ACS-related SCA, 93.8% (602/642) discharged without an ICD. The unique factor associated with non-ICD implantation in the setting of ACS was immediate coronary angioplasty (odds ratio 4.22, 95% confidence interval 1.86-9.30, P < 0.001).

CONCLUSION

Two-thirds of SCA survivors were discharged without an ICD, mainly in the setting of ACS. The unique factor associated with non-ICD implantation among ACS was immediate coronary angioplasty emphasizing the fact that ACS definition must be precise since associated with ICD implantation or not.

Lack of Early Etiologic Investigations in Young Sudden Cardiac Death

BACKGROUND

Since majority of sudden cardiac arrest (SCA) victims die in the intensive care unit (ICU), early etiologic investigations may improve understanding of SCA and targeted prevention.

METHODS

In this prospective, population-based registry all SCA admitted alive across the 48 hospitals of the Paris area were enrolled. We investigated the extent of early etiologic work-up among young SCD cases (<45 years) eventually dying within the ICU.

RESULTS

From May 2011 to May 2018, 4,314 SCA patients were admitted alive. Among them, 3,044 died in ICU, including 484 (15.9%) young patients. SCA etiology was established in 233 (48.1%) and remained unexplained in 251 (51.9%). Among unexplained (compared to explained) cases, coronary angiography (17.9 vs. 49.4%, P<0.001), computed tomography scan (24.7 vs. 46.8%, P<0.001) and trans-thoracic echocardiography (31.1 vs. 56.7%, P<0.001) were less frequently performed. Only 22 (8.8%) patients with unexplained SCD underwent all three investigations. SCDs with unexplained status decreased significantly over the 7 years of the study period (from 62.9 to 35.2%, P=0.005). While specialized TTE and CT scan performances have increased significantly, performance of early coronary angiography did not change. Autopsy, genetic analysis and family screening were performed in only 48 (9.9%), 5 (1.0%) and 14 cases (2.9%) respectively.

CONCLUSIONS

More than half of young SCD dying in ICU remained etiologically unexplained; this was associated with a lack of early investigations. Improving early diagnosis may enhance both SCA understanding and prevention, including for relatives. Failure to identify familial conditions may result in other preventable deaths within these families.

Prehospital Lyophilized Plasma Transfusion for Trauma-Induced Coagulopathy in Patients at Risk for Hemorrhagic Shock: A Randomized Clinical Trial

IMPORTANCE

Blood transfusion is a mainstay of therapy for trauma-induced coagulopathy, but the optimal modalities for plasma transfusion in the prehospital setting remain to be defined.

OBJECTIVE

To determine whether lyophilized plasma transfusion can reduce the incidence of trauma-induced coagulopathy compared with standard care consisting of normal saline infusion.

DESIGN, SETTING, AND PARTICIPANTS

This randomized clinical trial was performed at multiple centers in France involving prehospital medical teams. Participants included 150 adults with trauma who were at risk for hemorrhagic shock and associated coagulopathy between April 1, 2016, and September 30, 2019, with a 28-day follow-up. Data were analyzed from November 1, 2019, to July 1, 2020.

INTERVENTION

Patients were randomized in a 1:1 ratio to receive either plasma or standard care with normal saline infusion (control).

MAIN OUTCOMES AND MEASURES

The primary outcome was the international normalized ratio (INR) on arrival at the hospital. Secondary outcomes included the need for massive transfusion and 30-day survival. As a safety outcome, prespecified adverse events included thrombosis, transfusion-related acute lung injury, and transfusion-associated circulatory overload.

RESULTS

Among 150 randomized patients, 134 were included in the analysis (median age, 34 [IQR, 26-49] years; 110 men [82.1%]), with 68 in the plasma group and 66 in the control group. Median INR values were 1.21 (IQR, 1.12-1.49) in the plasma group and 1.20 (IQR, 1.10-1.39) in the control group (median difference, -0.01 [IQR, -0.09 to 0.08]; P = .88). The groups did not differ significantly in the need for massive transfusion (7 [10.3%] vs 4 [6.1%]; relative risk, 1.78 [95% CI, 0.42-8.68]; P = .37) or 30-day survival (hazard ratio for death, 1.07 [95% CI, 0.44-2.61]; P = .89). In the full intention-to-treat population (n = 150), the groups did not differ in the rates of any of the prespecified adverse events.

CONCLUSIONS AND RELEVANCE

In this randomized clinical trial including severely injured patients at risk for hemorrhagic shock and associated coagulopathy, prehospital transfusion of lyophilized plasma was not associated with significant differences in INR values vs standard care with normal saline infusion. Nevertheless, these findings show that lyophilized plasma transfusion is a feasible and safe procedure for this patient population.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02736812.

Does age influence out-of-hospital cardiac arrest incidence and outcomes among women? Insights from the Paris SDEC

AIMS

Age and sex disparities in out-of-hospital cardiac arrest (OHCA) have been described. Reproductive age may have a protected effect on females vs. males, although results are conflicting. We aimed to clarify this using the Paris Sudden Death Expertise Centre (SDEC) registry.

METHODS AND RESULTS

The Paris SDEC registry collects OHCAs occurring in the Greater Paris Area. We included all OHCAs of presumed cardiac causes occurring between 2013 and 2018. Patients were divided into age groups: 1-13, 13-50, 50-75, and >75 years. Sex and age disparities in OHCA incidence and outcomes were analysed using multivariable negative binomial and logistic regression models. There were 19 782 OHCAs meeting inclusion criteria: 0.37% aged 1-13 years, 12.4% aged 13-50 years, 40.4% aged 50-75 years, and 46.9% aged >75 years. Adjusted incidence rate ratios (IRRs) in females vs. males were for the youngest to the older age groups: 1.29 [95% confidence interval (CI) 0.78-2.13], 0.54 [0.49-0.59], 0.60 [0.56-0.64], and 0.75 [0.67-0.84]. At reproductive age, females were more likely than males to have a return of spontaneous circulation [adjusted odds ratio (OR) 1.60 (1.27-2.02)], to be alive at hospital admission [OR: 1.49 (1.18-1.89)]. In both sexes, patients aged 13-50 years were more likely to survive at hospital discharge than those aged 50-75 years [males: OR 1.81 (1.49-2.20), females: 2.24 (1.54-3.25)]. However, at reproductive age, no sex disparity was observed in survival at hospital discharge [OR: 1.16 (0.75-1.80)].

CONCLUSION

Incidence rate ratios were similar between pre- and post-menopausal aged patients. At reproductive age, no sex disparity in survival at hospital discharge was observed, suggesting that menopausal status may not influence OHCA occurrence and prognosis.

Organ donation after out-of-hospital cardiac arrest: a population-based study of data from the Paris Sudden Death Expertise Center

BACKGROUND

Organ shortage is a major public health issue, and patients who die after out-of-hospital cardiac arrest (OHCA) could be a valuable source of organs. Here, our objective was to identify factors associated with organ donation after brain death complicating OHCA, in unselected patients entered into a comprehensive real-life registry covering a well-defined geographic area.

METHODS

We prospectively analyzed consecutive adults with OHCA who were successfully resuscitated, but died in intensive care units in the Paris region in 2011-2018. The primary outcome was organ donation after brain death. Independent risk factors were identified using logistic regression analysis. One-year graft survival was assessed using Cox and log-rank tests.

RESULTS

Of the 3061 included patients, 136 (4.4%) became organ donors after brain death, i.e., 28% of the patients with brain death. An interaction between admission pH and post-resuscitation shock was identified. By multivariate analysis, in patients with post-resuscitation shock, factors associated with organ donation were neurological cause of OHCA (odds ratio [OR], 14.5 [7.6-27.4], P < 0.001), higher pH (OR/0.1 increase, 1.3 [1.1-1.6], P < 0.001); older age was negatively associated with donation (OR/10-year increase, 0.7 [0.6-0.8], P < 0.001). In patients without post-resuscitation shock, the factor associated with donation was neurological cause of OHCA (OR, 6.9 [3.0-15.9], P < 0.001); higher pH (OR/0.1 increase, 0.8 [0.7-1.0], P = 0.04) and OHCA at home (OR, 0.4 [0.2-0.7], P = 0.006) were negatively associated with organ donation. One-year graft survival did not differ according to Utstein characteristics of the donor.

CONCLUSIONS

4% of patients who died in ICU after OHCA led to organ donation. Patients with OHCA constitute a valuable source of donated organs, and special attention should be paid to young patients with OHCA of neurological cause.

Association between prehospital shock index and mortality among patients with COVID-19 disease

Background

There exists a need for prognostic tools for the early identification of COVID-19 patients requiring intensive care unit (ICU) admission and mortality. Here we investigated the association between a clinical (initial prehospital shock index (SI)) and biological (initial prehospital lactatemia) tool and the ICU admission and 30-day mortality among COVID-19 patients cared for in the prehospital setting.

Methods

We retrospectively analysed COVID-19 patients initially cared for by a Paris Fire Brigade advanced (ALS) or basic life support (BLS) team in the prehospital setting between 2020, March 08th and 2020, May 30th. We assessed the association between prehospital SI and prehospital lactatemia and ICU admission and mortality using logistic regression model analysis after propensity score matching with Inverse Probability Treatment Weighting (IPTW) method. Covariates included in the IPTW propensity analysis were: age, sex, body mass index (BMI), initial respiratory rate (iRR), initial pulse oximetry without (SpO2i) and with oxygen supplementation (SpO2i.O2), initial Glasgow coma scale (GCSi) value, initial prehospital SI and initial prehospital lactatemia.

Results

We analysed 410 consecutive COVID-19 patients [254 males (62%); mean age, 64 ± 18 years].

Fifty-seven patients (14%) deceased on the scene, of whom 41 (72%) were male and were significantly older (71 ± 12 years vs. 64 ± 19 years; P 〈10⁻³).

Fifty-three patients (15%) were admitted in ICU and 39 patients (11%) were deceased on day-30.

The mean prehospital SI value was 1.5 ± 0.4 and the mean prehospital lactatemia was 2.0 ± 1.7 mmol.l⁻¹.

Multivariate logistic regression analysis on matched population after IPTW propensity analysis reported a significant association between ICU admission and age (adjusted Odd-Ratio (aOR), 0.90; 95% confidence interval (95%CI): 0.93–0.98;p = 10⁻³), SpO2i.O2 (aOR, 1.10; 95%CI: 1.02–1.20;p = 0.002) and BMI (aOR, 1.09; 95% CI: 1.03–1.16;p = 0.02). 30-day mortality was significantly associated with SpO2i.O2 (aOR, 0.92; 95% CI: 0.87–0.98;p = 0.01 P < 10⁻³) and GCSi (aOR, 0.90; 95% CI: 0.82–0.99;p = 0.04).

Neither prehospital SI nor prehospital lactatemia were associated with ICU admission and 30-day mortality.

Conclusion

Neither prehospital initial SI nor lactatemia were associated with ICU admission and 30-day mortality among COVID-19 patients initially cared for by a Paris Fire Brigade BLS or ALS team. Further prospective studies are needed to confirm these preliminary results.

Advances in prehospital hemorrhagic shock management since Paris' terrorist attacks in 2015: A before-and-after retrospective study

BACKGROUND

In France, in 2015, prehospital emergency doctors were faced with civilian casualties in hemorrhagic shock resulting from terrorist attacks with automatic rifle fire and explosive weapons. The present study aimed to evaluate the impact of these attacks on the advanced life support (ALS) team's practices and equipment and on physician training in the prehospital management of traumatic hemorrhagic shock.

METHODS

This before-and-after multicenter study evaluated professional practices based on a questionnaire sent to emergency department heads and medical practitioners in 370 ALS teams in metropolitan France.

RESULTS

We analyzed 672 responses from 209 (56.5 percent) ALS teams in 91 of 95 emergency medical services (EMS) headquarters. Of these 91, 73 (80.2 percent) had a protocol in use for managing traumatic hemorrhagic shock after the attacks, compared with 45 (49.5 percent) who had protocols in use before the attacks (p < 0.001). Ultrasound equipment was available in 49 (53.8 percent) of the EMS headquarters after the attacks, compared to 39 (42.9 percent) before (p < 0.001). Limb tourniquets were available in 90 (98.9 percent) EMS headquarters after the attacks, versus 27 (29.7 percent) before (p < 0.001). Tranexamic acid was available in 88 (96.7 percent) EMS headquarters after the attacks, versus 71 (78 percent) before (p < 0.001). During the post-attack period, training in war medicine did not affect individual practices, neither for using the shock index or the Focused Assessment with Sonography for Trauma (FAST) nor the tourniquet. However, this training was associated with more frequent use of hemostatic dressings (p = 0.002).

CONCLUSION

Following the attacks in Paris and Nice, ALS teams received additional equipment and training to prepare for future mass causality events.

Assessment of emergency physicians' performance in identifying shockable rhythm in out-of-hospital cardiac arrest: an observational simulation study

BACKGROUND

Emergency physicians can use a manual or an automated defibrillator to provide defibrillation of patients who had out-of-hospital cardiac arrest (OHCA). Performance of emergency physicians in identifying shockable rhythm with a manual defibrillator has been poorly explored whereas that of automated defibrillators is well known (sensitivity 0.91-1.00, specificity 0.96-0.99). We conducted this study to estimate the sensitivity/specificity and speed of shock/no-shock decision-making by prehospital emergency physicians for shockable or non-shockable rhythm, and their preference for manual versus automated defibrillation.

METHODS

We developed a web application that simulates a manual defibrillator (https://simul-shock.firebaseapp.com/). In 2019, all (262) emergency physicians of six French emergency medical services were invited to participate in a study in which 60 ECG rhythms from real OHCA recordings were successively presented to the physicians for determination of whether they would or would not administer a shock. Time to decision was recorded. Answers were compared with a gold standard (concordant answers of three experts). We report sensitivity for shockable rhythms (decision to shock) and specificity for non-shockable rhythms (decision not to shock). Physicians were also asked whether they preferred manual or automated defibrillation.

RESULTS

Among 215 respondents, we were able to analyse results for 190 physicians. 57% of emergency physicians preferred manual defibrillation. Median (IQR) sensitivity for a shock delivery for shockable rhythm was 0.91 (0.81-1.00); median specificity for no-shock delivery for non-shockable rhythms was 0.91 (0.80-0.96). More precisely, sensitivities for shock delivery for ventricular tachycardia (VT) and coarse ventricular fibrillation (VF) were both 1.0 (1.0-1.0); sensitivity for fine VF was 0.6 (0.2-1). Specificity for not shocking a pulseless electrical activity (PEA) was 0.83 (0.72-0.86), and for asystole, specificity was 0.93 (0.86-1). Median speed of decision-making (in seconds) were: VT 2.0 (1.6-2.7), coarse VF 2.1 (1.7-2.9), asystole 2.4 (1.8-3.5), PEA 2.8 (2.0-4.2) and fine VF 2.8 (2.1-4.3).

CONCLUSIONS

Global sensitivity and specificity were comparable with published automated external defibrillator studies. Shockable rhythms with the best clinical prognoses (VT and coarse VF) were very rapidly recognised with very good sensitivity. The decision-making for fine VF or asystole and PEA was less accurate.

Polymer Modeling of 3D Epigenome Folding: Application to Drosophila

Mechanistic modeling in biology allows to investigate, based on first principles, if putative hypotheses are compatible with observations and to drive further experimental works. Along this line, polymer modeling has been instrumental in 3D genomics to better understand the impact of key mechanisms on the spatial genome organization. Here, I describe how polymer-based models can be practically used to study the role of epigenome in chromosome folding. I illustrate this methodology in the context of Drosophila epigenome folding.

Live imaging and biophysical modeling support a button-based mechanism of somatic homolog pairing in Drosophila

Three-dimensional eukaryotic genome organization provides the structural basis for gene regulation. In Drosophila melanogaster, genome folding is characterized by somatic homolog pairing, where homologous chromosomes are intimately paired from end to end; however, how homologs identify one another and pair has remained mysterious. Recently, this process has been proposed to be driven by specifically interacting 'buttons' encoded along chromosomes. Here, we turned this hypothesis into a quantitative biophysical model to demonstrate that a button-based mechanism can lead to chromosome-wide pairing. We tested our model using live-imaging measurements of chromosomal loci tagged with the MS2 and PP7 nascent RNA labeling systems. We show solid agreement between model predictions and experiments in the pairing dynamics of individual homologous loci. Our results strongly support a button-based mechanism of somatic homolog pairing in Drosophila and provide a theoretical framework for revealing the molecular identity and regulation of buttons.

Logistical Challenge With Prehospital Use of High-Flow Nasal Oxygen Therapy in COVID-19-Induced Respiratory Distress: A Case Report

Background Although commonly used inside hospitals, no previous case report has been published on high-flow nasal oxygen (HFNO) therapy in an adult in the prehospital setting. Case Report A 46-year-old nonsmoking man presented with a cough and fever. He deteriorated suddenly 5 days later. When the basic life support team arrived, his peripheral oxygen saturation (SpO₂) in ambient air was 56% and respiratory rate was 46 breaths/min. The man was weak with thoracoabdominal asynchrony. An emergency medical team with a physician was dispatched. As France was still under lockdown for the SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) pandemic, COVID-19 (coronavirus disease 2019) was suspected. In spite of 15 L/min of oxygen delivered with a nonrebreathing mask, the patient's SpO₂ tended to drop below 90% at the slightest effort and during transport from home to the ambulance. It was therefore decided to start HFNO therapy. The patient was transferred to an intensive care unit, where HFNO was continued. Why Should an Emergency Physician Be Aware of This? As the trend in emergency medical services may move toward prehospital HFNO, this case report is an opportunity to question the feasibility of HFNO therapy in the prehospital setting.

[Fighting against unexplained sudden death]

Sudden cardiac death, mostly related to ventricular arrhythmia, is a major public health issue, with still very poor survival at hospital discharge. Although coronary artery disease remains the leading cause, other etiologies should be systematically investigated. Exhaustive and standardized exploration is required to eventually offer specific therapeutics and management to the patient as well as his/her family members in case of inherited cardiac disease. Identification and establishing direct causality of the detected cardiac anomaly may remain challenging, underlying the need for a multidisciplinary and experimented team.

RNA polymerase backtracking results in the accumulation of fission yeast condensin at active genes

Using both experiments and mathematical modelling, the authors show that RNA polymerase backtracking contributes to the accumulation of condensin in the termination zone of active genes.

The mechanisms leading to the accumulation of the SMC complexes condensins around specific transcription units remain unclear. Observations made in bacteria suggested that RNA polymerases (RNAPs) constitute an obstacle to SMC translocation, particularly when RNAP and SMC travel in opposite directions. Here we show in fission yeast that gene termini harbour intrinsic condensin-accumulating features whatever the orientation of transcription, which we attribute to the frequent backtracking of RNAP at gene ends. Consistent with this, to relocate backtracked RNAP2 from gene termini to gene bodies was sufficient to cancel the accumulation of condensin at gene ends and to redistribute it evenly within transcription units, indicating that RNAP backtracking may play a key role in positioning condensin. Formalization of this hypothesis in a mathematical model suggests that the inclusion of a sub-population of RNAP with longer dwell-times is essential to fully recapitulate the distribution profiles of condensin around active genes. Taken together, our data strengthen the idea that dense arrays of proteins tightly bound to DNA alter the distribution of condensin on chromosomes.

Automatic external defibrillator provided by unmanned aerial vehicle (drone) in Greater Paris: A real world-based simulation

AIM

To reduce the delay in defibrillation of out-of-hospital cardiac arrest (OHCA) patients, recent publications have shown that drones equipped with an automatic external defibrillator (AED) appear to be effective in sparsely populated areas. To study the effectiveness of AED-drones in high-density urban areas, we developed an algorithm based on emergency dispatch parameters for the rate and detection speed of cardiac arrests and technical and meteorological parameters.

METHODS

We ran a numerical simulation to compare the actual time required by the Basic Life Support team (BLSt) for OHCA patients in Greater Paris in 2017 to the time required by an AED-drone. Endpoints were the proportion of patients with "AED-drone first" and the defibrillation time gained. We built an open-source website (https://airborne-aed.org/) to allow modelling by modifying one or more parameters and to help other teams model their own OHCA data.

RESULTS

Of 3014 OHCA patients, 72.2 ± 0.7% were in the "no drone flight" group, 25.8 ± 0.2% in the "AED-drone first" group, and 2.1 ± 0.2% in the "BLSt-drone first" group. When a drone flight was authorized, it arrived an average 190 s before BLSt in 93% of cases. The possibility of flying the drone during the aeronautical night improved the results of the "AED-drone first" group the most (+60%).

CONCLUSIONS

In our very high-density urban model, at most 26% of OHCA patients received an AED from an AED-drone before BLSt. The flexible parameters of our website model allows evaluation of the impact of each choice and concrete implementation of the AED-drone.

Temporal Trends of Out-of-Hospital Cardiac Arrests Without Resuscitation Attempt by Emergency Medical Services

BACKGROUND

Significant improvements in survival from out-of-hospital cardiac arrest (OHCA) have been reported; however, these are based only on data from OHCA in whom resuscitation is initiated by emergency medical services (EMS). We aimed to assess the characteristics and temporal trends of OHCA without resuscitation attempt by EMS.

METHODS

Prospective population-based study between 2011 and 2016 in the Greater Paris area (6.7 million inhabitants). All cases of OHCA were included in collaboration with EMS units, 48 different hospitals, and forensic units.

RESULTS

Among 15 207 OHCA (mean age 70.7±16.9 years, 61.6% male), 5486 (36.1%) had no resuscitation attempt by EMS. Factors that were independently associated with increase in likelihood of no resuscitation attempt included: age of patients (odds ratio, 1.06 per year [95% CI, 1.05-1.06], P<0.001), female sex (odds ratio, 1.21 [95% CI, 1.10-1.32], P=0.002), OHCA at home location (odds ratio, 3.38 [95%CI, 2.86-4.01], P<0.001), and absence of bystander (odds ratio, 1.94 [95% CI, 1.74-2.16], P<0.001). Overall, the annual number of OHCA increased by 9.1% (from 2923 to 3189, P=0.028). This increase was related to an increase of the annual number of OHCA without resuscitation attempt by EMS by 26.3% (from 993 to 1253, P=0.012), while the annual number of OHCA with resuscitation attempt by EMS did not significantly change (from 1930 to 1936, P=0.416). Considering only cases with resuscitation attempt, survival rate at hospital discharge increased (from 7.3% to 9.5%, P=0.02). However, when considering all OHCA, survival improvement did not reach statistical significance (from 4.8% to 5.7%, P=0.17).

CONCLUSIONS

We demonstrated an increase of the total number of OHCA related to an increase of the number of OHCA without resuscitation attempt by EMS. This increasing proportion of OHCA without resuscitation attempt attenuates improvement in survival rates achieved in EMS-treated patients.

Polymer modelling unveils the roles of heterochromatin and nucleolar organizing regions in shaping 3D genome organization in Arabidopsis thaliana

The 3D genome is characterized by a complex organization made of genomic and epigenomic layers with profound implications on gene regulation and cell function. However, the understanding of the fundamental mechanisms driving the crosstalk between nuclear architecture and (epi)genomic information is still lacking. The plant Arabidopsis thaliana is a powerful model organism to address these questions owing to its compact genome for which we have a rich collection of microscopy, chromosome conformation capture (Hi-C) and ChIP-seq experiments. Using polymer modelling, we investigate the roles of nucleolus formation and epigenomics-driven interactions in shaping the 3D genome of A. thaliana. By validation of several predictions with published data, we demonstrate that self-attracting nucleolar organizing regions and repulsive constitutive heterochromatin are major mechanisms to regulate the organization of chromosomes. Simulations also suggest that interphase chromosomes maintain a partial structural memory of the V-shapes, typical of (sub)metacentric chromosomes in anaphase. Additionally, self-attraction between facultative heterochromatin regions facilitates the formation of Polycomb bodies hosting H3K27me3-enriched gene-clusters. Since nucleolus and heterochromatin are highly-conserved in eukaryotic cells, our findings pave the way for a comprehensive characterization of the generic principles that are likely to shape and regulate the 3D genome in many species.