Wilderness Medical Society Clinical Practice Guidelines for Prevention and Management of Avalanche and Nonavalanche Snow Burial Accidents: 2024 Update.

To provide guidance to the general public, clinicians, and avalanche professionals about best practices, the Wilderness Medical Society convened an expert panel to revise the evidence-based guidelines for the prevention, rescue, and resuscitation of avalanche and nonavalanche snow burial victims. The original panel authored the Wilderness Medical Society Practice Guidelines for Prevention and Management of Avalanche and Nonavalanche Snow Burial Accidents in 2017. A second panel was convened to update these guidelines and make recommendations based on quality of supporting evidence.

Surviving 20 Hours of Critical Avalanche Burial and a Core Temperature of 22.5 °C.

A 24-year-old male snowboarder was buried in an avalanche for 20 h and rescued on the next day at a depth of 2.3 m below the snow surface. A large air pocket was noted in front of his mouth and nose. He was responsive but moved restlessly and uncoordinatedly. The epitympanic temperature was 22.5 °C. He was bradycardic (35/min), and a right bundle branch block with Osborn waves was noted. Rewarming (1 °C/h) was initiated with continuous hemodialysis; core temperature raised to 29.8 °C within 4 h. At 30 °C he became conscious. With rewarming, the heart rate increased to 90 beats per minute and the ECG changes disappeared; nonfreezing cold injuries were noted. On the next day, his pulmonary function deteriorated-fluid overload of 9 L since admission was diagnosed. With spontaneous diuresis, the situation improved. On Day 4, the neurologist reported subtle polyneuropathy in both legs secondary to hypothermia, without tendency to regress. This case occurred more than 20 years ago but has not been reported yet. To this day, this is the third-longest critical avalanche burial ever reported. We discuss the circumstances of this accident, the clinical course, and how treatment has changed since 2000.

Many-Body Resonances in the Avalanche Instability of Many-Body Localization.

Many-body localized (MBL) systems fail to reach thermal equilibrium under their own dynamics, even though they are interacting, nonintegrable, and in an extensively excited state. One instability toward thermalization of MBL systems is the so-called "avalanche," where a locally thermalizing rare region is able to spread thermalization through the full system. The spreading of the avalanche may be modeled and numerically studied in finite one-dimensional MBL systems by weakly coupling an infinite-temperature bath to one end of the system. We find that the avalanche spreads primarily via strong many-body resonances between rare near-resonant eigenstates of the closed system. Thus we find and explore a detailed connection between many-body resonances and avalanches in MBL systems.

Scale free avalanches in excitatory-inhibitory populations of spiking neurons with conductance based synaptic currents.

We investigate spontaneous critical dynamics of excitatory and inhibitory (EI) sparsely connected populations of spiking leaky integrate-and-fire neurons with conductance-based synapses. We use a bottom-up approach to derive a single neuron gain function and a linear Poisson neuron approximation which we use to study mean-field dynamics of the EI population and its bifurcations. In the low firing rate regime, the quiescent state loses stability due to saddle-node or Hopf bifurcations. In particular, at the Bogdanov-Takens (BT) bifurcation point which is the intersection of the Hopf bifurcation and the saddle-node bifurcation lines of the 2D dynamical system, the network shows avalanche dynamics with power-law avalanche size and duration distributions. This matches the characteristics of low firing spontaneous activity in the cortex. By linearizing gain functions and excitatory and inhibitory nullclines, we can approximate the location of the BT bifurcation point. This point in the control parameter phase space corresponds to the internal balance of excitation and inhibition and a slight excess of external excitatory input to the excitatory population. Due to the tight balance of average excitation and inhibition currents, the firing of the individual cells is fluctuation-driven. Around the BT point, the spiking of neurons is a Poisson process and the population average membrane potential of neurons is approximately at the middle of the operating interval [Formula: see text]. Moreover, the EI network is close to both oscillatory and active-inactive phase transition regimes.

Avalanches during epithelial tissue growth; Uniform Growth and a drosophila eye disc model.

Epithelial tissues constitute an exotic type of active matter with non-linear properties reminiscent of amorphous materials. In the context of a proliferating epithelium, modeled by the quasistatic vertex model, we identify novel discrete tissue scale rearrangements, i.e. cellular rearrangement avalanches, which are a form of collective cell movement. During the avalanches, the vast majority of cells retain their neighbors, and the resulting cellular trajectories are radial in the periphery, a vortex in the core. After the onset of these avalanches, the epithelial area grows discontinuously. The avalanches are found to be stochastic, and their strength is correlated with the density of cells in the tissue. Overall, avalanches redistribute accumulated local spatial pressure along the tissue. Furthermore, the distribution of avalanche magnitudes is found to obey a power law, with an exponent consistent with sheer induced avalanches in amorphous materials. To understand the role of avalanches in organ development, we simulate epithelial growth of the Drosophila eye disc during the third instar using a computational model, which includes both chemical and mechanistic signaling. During the third instar, the morphogenetic furrow (MF), a ~10 cell wide wave of apical area constriction propagates through the epithelium. These simulations are used to understand the details of the growth process, the effect of the MF on the growth dynamics on the tissue scale, and to make predictions for experimental observations. The avalanches are found to depend on the strength of the apical constriction of cells in the MF, with a stronger apical constriction leading to less frequent and more pronounced avalanches. The results herein highlight the dependence of simulated tissue growth dynamics on relaxation timescales, and serve as a guide for in vitro experiments.

Survival in a Collapsed Stable for 37 Days After Avalanche Burial in 1755.

In 1755 in Bergemoletto, Italy, an avalanche buried 4 people (2 women, a girl, and a boy) and several animals in a stable. After 37 d in a pitch-dark confined space, 3 of the 4 people were rescued alive. The 3 survivors had only goat milk, a few chestnuts, a few kg of raw kid meat, and meltwater for nutrition. We describe the longest-known survival in an avalanche burial and discuss the medical and psychological problems of the survivors. The boy died. When they were extricated, all 3 survivors were exhausted, cachectic, and unable to stand or walk. They were severely malnourished and were experiencing tingling, tremors, and weakness in the legs; constipation; changes in taste; and amenorrhea. One of the women had persistent eye problems and developed symptoms consistent with post-traumatic stress disorder. The survivors were given slow refeeding. It took from 1 to 6 wk before they could walk. We compare this case to other long-duration burials, especially mining accidents, and describe the rescue and patient care after long-duration burials. This case demonstrates that people can overcome extremely adverse conditions and survive.

History of Avalanches in the Eastern Spanish Pyrenees.

Avalanches have caused injuries and deaths in mountain areas throughout history. We have examined the historical effects of avalanches on communities in the eastern Spanish Pyrenees. Surviving written records began in the year 1444 when an avalanche destroyed the village of Gessa. Many other avalanches since then have destroyed houses and other buildings and have caused injuries and deaths. In the 20th and 21st centuries, many villages evolved from agrarian areas to destinations for winter sports. The first known deaths during winter recreation likely occurred in 1930. Because of avalanche mitigation efforts, including relocating settlements, physical barriers, avalanche control measures, efforts to increase avalanche awareness, and avalanche warnings, avalanches now seldom affect inhabited areas in the eastern Spanish Pyrenees. Avalanche injuries and fatalities are now mainly limited to backcountry skiers and others traveling out of bounds near avalanche-controlled ski resorts.

Avalanche Airbag Usage and Risk Attitudes of Backcountry Skiers and Snowboarders in the American West.

INTRODUCTION: Backcountry skiers and snowboarders are increasingly using avalanche airbags to improve safety. New safety devices can cause risk compensation, the concept in which users take more risks given the larger safety margin provided by the device. This may limit overall benefits. We sought to elucidate attitudes toward risk-taking behaviors and risk compensation in backcountry users relating to avalanche airbags. METHODS: A convenience sample of 144 backcountry skiers and snowboarders was surveyed after a backcountry tour in the Wasatch Mountains of Utah and the Tetons of Wyoming during the winter 2020-21 season. Demographic and experiential data were compared with risk propensity scores and attitudes toward risk compensation. Respondents were stratified into high-, medium-, and low-risk groupings based on risk propensity scores and whether an airbag was carried. RESULTS: Thirty-two (22%) respondents carried an airbag. Airbag users were more likely to endorse risk compensation behavior, ski terrain over 30 degrees, and fall into the high-risk cohort. The high-risk cohort was also more likely to endorse risk compensation behavior than medium- and low-risk individuals. CONCLUSIONS: Risk compensation was more prevalent in 2 groups: 1) those carrying an airbag and 2) those falling within the high-risk cohort. Given the prevalence of avalanche airbags, risk compensation should be considered alongside other human factors in avalanche safety and education so that users can mitigate these effects. Although risk compensation appears to be occurring, the magnitude of this effect remains unknown and likely does not obviate the safety benefits of the airbag altogether.

Avalanche Education Is Associated with Increased Avalanche Safety Practices in the New Hampshire Backcountry.

INTRODUCTION: Avalanche risk can be mitigated by adhering to certain safety practices. Previous studies of these practices have focused on western United States and European cohorts. We conducted a survey of backcountry users in the White Mountains of New Hampshire to determine local adherence to 5 previously studied avalanche safety practices. We assessed whether participants were carrying transceiver, probe, and shovel (TPS); had formal avalanche education; had awareness of the day's avalanche danger level; had a route plan; and were traveling in a group. METHODS: Backcountry users in the White Mountains were directed to an online survey from December 2020 to June 2021. The survey was completed individually and queried demographics and avalanche safety practices. RESULTS: A total of 133 users participated. Not all surveyed participants answered all questions. Avalanche training was reported by 87% of users, 86% checked the avalanche forecast prior to recreating, 93% had a travel plan, 87% traveled in a group, and 59% carried TPS. All 3 items were carried by all group members only 48% of the time. Only 28% of users met all 5 safety practices. CONCLUSIONS: White Mountains backcountry users are less likely to meet avalanche safety practices than users in previous studies. There is an association between meeting these defined safety practices and formal avalanche education.

Debris flow simulation and modeling of the 2021 flash flood hazard caused by a rock-ice avalanche in the Rishiganga River valley of Uttarakhand.

The high mountain ecosystem of the Indian Himalayas has frequently been experiencing primary hazards (like earthquakes, avalanches, and landslides). Often, these events are followed by the triggering of secondary hazards (like landslide dams, debris flows, and flooding), thereby posing massive risks to infrastructure and residents in the region. This study was taken up to understand the dynamics of an extraordinary debris flood disaster in the Rishiganga River valley, Chamoli district of Uttarakhand on 7th February 2021. Rapid mass movements (RAMMS)-debris flow software was employed to recreate the entire sequence of the hazard consisting of a rock-ice slide, mass deposition and erosion along the channel, and subsequent debris flood. Forty-nine scenarios were analyzed for accurate calibration of dry-Coulomb type friction coefficient (µ) and viscous-turbulent friction coefficient (ξ). Consequently, the geomorphologic characteristics of the debris flow were validated using high-resolution satellite image interpretation and field photographs. The volume of detached rock-ice mass was estimated to be 26.42 × 106 m3. At the same time, the RAMMS-derived model outputs for velocity, flow depth, and momentum were found in good agreement with the extent and height of actual debris on the ground. The study highlights an urgent need to identify the glaciers with a high risk of ice avalanches in the Indian Himalayas. The presented modeling approach may be applied in dynamic mountain ecosystems to simulate potential flash floods due to avalanches. Moreover, the information reported in this study can be vital input for improving the district-level disaster management plan.

Cardiolipin-Targeted NIR-II Fluorophore Causes "Avalanche Effects" for Re-Engaging Cancer Apoptosis and Inhibiting Metastasis.

Restoring innate apoptosis and simultaneously inhibiting metastasis by a molecular drug is an effective cancer therapeutic approach. Herein, a large rigid and V-shaped NIR-II dye, DUT850, is rationally designed for potential cardiolipin (CL)-targeted chemo-phototheranostic application. DUT850 displays moderate NIR-II fluorescence, excellent photodynamic therapy (PDT) and photothermal therapy (PTT) performance, and ultra-high photostability. More importantly, the unique rigid V-shaped backbone, positive charge, and lipophilicity of DUT850 afford its specific recognition and efficient binding to CL; such an interaction of DUT850-CL induced a spectrum of physiological disruptions, including translocation of cytochrome c, Ca2+ overload, reactive oxygen species burst, and ATP depletion, which not only activated cancer cell apoptosis but also inhibited tumor metastasis both in vitro and in vivo. Furthermore, the tight binding of DUT850-CL improves the phototoxicity of DUT850 toward cancer cells (IC50 as low as 90 nM) under safe 808 nm laser irradiation (330 mW cm-2). Upon encapsulation into bovine serum albumin (BSA), DUT850@BSA exerted a synergetic chemo-PDT-PTT effect on the 4T1 tumor mouse model, eventually leading to solid tumor annihilation and metastasis inhibition, which could be followed in real time with the NIR-II fluorescence of DUT850. This work contributed a promising approach for simultaneously re-engaging cancer cell apoptotic networks and activating the anti-metastasis pathway by targeting a pivotal upstream effector, which will bring a medical boon for inhibition of tumor proliferation and metastasis.

Avalanche criticality in individuals, fluid intelligence, and working memory.

The critical brain hypothesis suggests that efficient neural computation can be achieved through critical brain dynamics. However, the relationship between human cognitive performance and scale-free brain dynamics remains unclear. In this study, we investigated the whole-brain avalanche activity and its individual variability in the human resting-state functional magnetic resonance imaging (fMRI) data. We showed that though the group-level analysis was inaccurate because of individual variability, the subject wise scale-free avalanche activity was significantly associated with maximal synchronization entropy of their brain activity. Meanwhile, the complexity of functional connectivity, as well as structure-function coupling, is maximized in subjects with maximal synchronization entropy. We also observed order-disorder phase transitions in resting-state brain dynamics and found that there were longer times spent in the subcritical regime. These results imply that large-scale brain dynamics favor the slightly subcritical regime of phase transition. Finally, we showed evidence that the neural dynamics of human participants with higher fluid intelligence and working memory scores are closer to criticality. We identified brain regions whose critical dynamics showed significant positive correlations with fluid intelligence performance and found that these regions were located in the prefrontal cortex and inferior parietal cortex, which were believed to be important nodes of brain networks underlying human intelligence. Our results reveal the possible role that avalanche criticality plays in cognitive performance and provide a simple method to identify the critical point and map cortical states on a spectrum of neural dynamics, ranging from subcriticality to supercriticality.

Temporal evolution of failure avalanches of the fiber bundle model on complex networks.

We investigate how the interplay of the topology of the network of load transmitting connections and the amount of disorder of the strength of the connected elements determines the temporal evolution of failure cascades driven by the redistribution of load following local failure events. We use the fiber bundle model of materials' breakdown assigning fibers to the sites of a square lattice, which is then randomly rewired using the Watts-Strogatz technique. Gradually increasing the rewiring probability, we demonstrate that the bundle undergoes a transition from the localized to the mean field universality class of breakdown phenomena. Computer simulations revealed that both the size and the duration of failure cascades are power law distributed on all network topologies with a crossover between two regimes of different exponents. The temporal evolution of cascades is described by a parabolic profile with a right handed asymmetry, which implies that cascades start slowly, then accelerate, and eventually stop suddenly. The degree of asymmetry proved to be characteristic of the network topology gradually decreasing with increasing rewiring probability. Reducing the variance of fibers' strength, the exponents of the size and the duration distribution of cascades increase in the localized regime of the failure process, while the localized to mean field transition becomes more abrupt. The consistency of the results is supported by a scaling analysis relating the characteristic exponents of the statistics and dynamics of cascades.

Electromagnetic Interference from Heated Gloves May Compromise Avalanche Transceiver Function.

INTRODUCTION: Rapid location of avalanche victims by companions using avalanche transceivers is of utmost importance to prevent asphyxiation. The objective was to determine whether electromagnetic interference from heating elements in gloves worn by rescuers or victims can impair the receiving or transmitting function of avalanche beacons. METHODS: Commercially available heated gloves from 3 different manufacturers were examined during a simulated search with 3 common brands of avalanche transceivers. Distance to target beacon at first signal detection and accuracy of direction to target, as indicated by the arrow from the direction indicator, were evaluated. RESULTS: Preliminary tests showed that transmitting and receiving signals are degraded by electromagnetic interference caused by rectangular pulses emitted by activated heating elements. Field tests revealed significantly reduced distances of first signal detection when heated gloves were turned on near receiving avalanche transceivers (P<0.001; Wilcoxon signed-rank test). Decreased distance to target beacon ranged between 1.9 m (5%) and 41.5 m (94%) at first detection, depending on the avalanche transceiver used. CONCLUSIONS: Avalanche transceivers are susceptible to electromagnetic interference from gloves with electric heating elements. We do not recommend using heated gloves when performing a transceiver search for avalanche victims because it can lead to a delay in rescue.

Avalanche Preparedness and Accident Analysis Among Backcountry Skier, Sidecountry, and Snowmobile Fatalities in the United States: 2009 to 2019.

INTRODUCTION: While avalanche fatalities have remained relatively steady per year, data suggest a possible increase in sidecountry use and snowmobile fatalities. Limited information is known regarding the accident details and preparedness among different groups of backcountry users including snowmobiles, sidecountry, and backcountry skiers, and what specific factors could contribute to their fatalities. METHODS: Avalanche fatality reports covering all US states posted by the Colorado Avalanche Information Center available online for 10 seasons (2009-2010 through 2018-2019 seasons) were analyzed for group size, specific equipment carried, burial depth, burial time, and other details. Only reports in the 3 following categories were included in the analysis: backcountry ski/snowboard, sidecountry ski/snowboard, and snowmobile/snowbike. These aspects were compared among the 3 tourer types using statistical analyses (ANOVA). RESULTS: Two hundred and five fatalities were analyzed (n=32 sidecountry, n=91 skier/snowboard, n=82 snowmobile/snowbike). Using 2 preparedness scores, the ski/snowboard group had the greatest distribution of high scores when evaluated by equipment carried and group size, with significant differences per group (P<0.01). Of the fatalities that were buried, burial time was related to the tourer group (P=0.04), with the ski/snowboard group having the highest proportion of burials <15 min. Burial depth was significantly different among the 3 tourer groups, with snowmobiles buried the deepest on average (P<0.01). CONCLUSIONS: Despite limited data available on fatalities, an analysis of preparedness suggests that backcountry skiers and snowboarders are more prepared for avalanche accidents compared to snowmobiles and sidecountry users when evaluated by equipment carried and group size.

Perceptions Among Backcountry Skiers During the COVID-19 Pandemic: Avalanche Safety and Backcountry Habits of New and Established Skiers.

INTRODUCTION: The coronavirus disease 2019 (COVID-19) pandemic impacted the ski industry worldwide by closing or limiting access to ski resorts. Subsequently, anecdotal reports of increased backcountry use emerged in the press, with concerns of inexperienced skiers causing or having problems in the backcountry. This study attempted to quantify this and identify motivations for new backcountry skiers. METHODS: Self-identified backcountry skiers and snowboarders (aged ≥18 y) in the United States and Canada completed an anonymous 29-question online survey distributed by regional avalanche centers, education providers, and skiing organizations (n=4792). Respondents were stratified by backcountry experience, defining "newcomers" who began backcountry skiing from 2019 to 2021, coincident with the COVID-19 pandemic. Percentages of ski days spent in the backcountry were compared before and during the COVID-19 pandemic using paired t-tests and across cohorts using repeated-measures analysis of variance. Avalanche education was compared using unpaired χ2 tests. RESULTS: Of established skiers, 81% noticed more people in the backcountry and 27% reported increasing their own use. Participants reported spending 17% (95% CI, 15.8-17.9) more of their days in the backcountry during the COVID-19 pandemic, with newcomers increasing their time spent by 36% and established skiers increasing their time spent by 13% (P<0.0001). Of newcomers, 27% cited the COVID-19 pandemic as motivation to enter the backcountry and 24% lacked formal avalanche education, which is significantly higher than the 14% of established skiers (P<0.0001). CONCLUSIONS: Influenced by factors related to COVID-19, reported backcountry use increased during the pandemic. Newcomers had a lower level of avalanche education and less confidence in evaluating terrain. Because 80% of participants were recruited from avalanche safety or education websites, this likely underestimates skiers lacking avalanche awareness or education and is further limited by the nature of online surveys.

Noise and Breakdown Characterization of SPAD Detectors with Time-Gated Photon-Counting Operation.

Being ready-to-detect over a certain portion of time makes the time-gated single-photon avalanche diode (SPAD) an attractive candidate for low-noise photon-counting applications. A careful SPAD noise and performance characterization, however, is critical to avoid time-consuming experimental optimization and redesign iterations for such applications. Here, we present an extensive empirical study of the breakdown voltage, as well as the dark-count and afterpulsing noise mechanisms for a fully integrated time-gated SPAD detector in 0.35-µm CMOS based on experimental data acquired in a dark condition. An "effective" SPAD breakdown voltage is introduced to enable efficient characterization and modeling of the dark-count and afterpulsing probabilities with respect to the excess bias voltage and the gating duration time. The presented breakdown and noise models will allow for accurate modeling and optimization of SPAD-based detector designs, where the SPAD noise can impose severe trade-offs with speed and sensitivity as is shown via an example.

An Ultrafast Active Quenching Active Reset Circuit with 50% SPAD Afterpulsing Reduction in a 28 nm FD-SOI CMOS Technology Using Body Biasing Technique.

An ultrafast Active Quenching-Active Reset (AQAR) circuit is presented for the afterpulsing reduction in a Single Photon Avalanche Diode (SPAD). The proposed circuit is designed in a 28 nm Fully Depleted Silicon On Insulator (FD-SOI) CMOS technology. By exploiting the body biasing technique, the avalanche is detected very quickly and, consequently, is quenched very fast. The fast quenching decreases the avalanche charges, therefore resulting in the afterpulsing reduction. Both post-layout and experimental results are presented and are highly in accordance with each other. It is shown that the proposed AQAR circuit is able to detect the avalanche in less than 40 ps and reduce the avalanche charge and the afterpulsing up to 50%.

Single Photon Avalanche Diode Arrays for Time-Resolved Raman Spectroscopy.

The detection of peaks shifts in Raman spectroscopy enables a fingerprint reconstruction to discriminate among molecules with neither labelling nor sample preparation. Time-resolved Raman spectroscopy is an effective technique to reject the strong fluorescence background that profits from the time scale difference in the two responses: Raman photons are scattered almost instantaneously while fluorescence shows a nanoseconds time constant decay. The combination of short laser pulses with time-gated detectors enables the collection of only those photons synchronous with the pulse, thus rejecting fluorescent ones. This review addresses time-gating issues from the sensor standpoint and identifies single photon avalanche diode (SPAD) arrays as the most suitable single-photon detectors to be rapidly and precisely time-gated without bulky, complex, or expensive setups. At first, we discuss the requirements for ideal Raman SPAD arrays, particularly focusing on the design guidelines for optimized on-chip processing electronics. Then we present some existing SPAD-based architectures, featuring specific operation modes which can be usefully exploited for Raman spectroscopy. Finally, we highlight key aspects for future ultrafast Raman platforms and highly integrated sensors capable of undistorted identification of Raman peaks across many pixels.

Witnessed Cardiac Arrest in a Hypothermic Avalanche Victim Completely Buried for 2 Hours.

A 34-y-old skier triggered a wind slab avalanche and was completely buried for over 2 h. After extrication by rescuers, the victim was breathing and conscious. Despite directions from the rescuers against standing up, the victim struggled to free himself and ultimately stood upright before collapsing in cardiac arrest. The rescuers performed cardiopulmonary resuscitation during transport to a nearby trailhead, where a helicopter emergency medical services crew found that the victim was in ventricular fibrillation. After further resuscitative efforts, including advanced life support, the victim was declared dead at the scene. Afterdrop and circumrescue collapse were the most likely triggers of cardiac arrest. This case highlights a need for rescuers, emergency medical services, and hospitals to be prepared to care for victims with hypothermia. To prevent circumrescue collapse, victims with hypothermia should be extricated gently, should not be allowed to stand, and should be placed flat. This may be difficult or impossible, as in this case. Hypothermic victims in cardiac arrest may require prolonged cardiopulmonary resuscitation, preferably with mechanical compressions, during transport to a hospital that has protocols for rewarming using extracorporeal life support. Resuscitation from hypothermic cardiac arrest should not be terminated before the victim has been rewarmed.