High altitude is the most intriguing natural laboratory to study human physiological response to hypoxic conditions. In this study, we investigated changes in reactive oxygen species (ROS) and oxidative stress biomarkers during exposure to hypobaric hypoxia in 16 lowlanders. Moreover, we looked at the potential relationship between ROS related cellular damage and optic nerve sheath diameter (ONSD) as an indirect measurement of intracranial pressure. Baseline measurement of clinical signs and symptoms, biological samples and ultrasonography were assessed at 262 m and after passive ascent to 3830 m (9, 24 and 72 h). After 24 h the imbalance between ROS production (+141%) and scavenging (−41%) reflected an increase in oxidative stress related damage of 50–85%. ONSD concurrently increased, but regression analysis did not infer a causal relationship between oxidative stress biomarkers and changes in ONSD. These results provide new insight regarding ROS homeostasis and potential pathophysiological mechanisms of acute exposure to hypobaric hypoxia, plus other disease states associated with oxidative-stress damage as a result of tissue hypoxia.

Breathing under snow, e.g. while buried by a snow avalanche, is possible in the presence of an air pocket, but limited in time as hypoxia and hypercapnia rapidly develop. Snow properties influence levels of hypoxia and hypercapnia, but their effects on ventilation and oxygenation in humans are not fully elucidated yet. We report that in healthy subjects breathing into snow with an artificial air pocket, snow density had a direct influence on ventilation, oxygenation and exhaled CO₂. We found that a rapid decline in O₂ and increase in CO₂ were mainly associated with higher snow densities and led to premature interruption due to critical hypoxia (SpO₂ ≤ 75%). However, subjects in the low snow density group demonstrated a higher frequency of test interruptions than expected, due to clinical symptoms related to a rapid CO₂ accumulation in the air pocket. Snow properties determine the oxygen support by diffusion from the surrounding snow and the clearance of CO₂ by diffusion and absorption. Thus, snow properties are co-responsible for survival during avalanche burial.

Epitympanic temperature (Tty) measured with thermistor probes correlates with core body temperature (Tcore), but the reliability of measurements at low ambient temperature is unknown. The aim of this study was to determine if commercially-available thermistor-based Tty reflects Tcore in low ambient temperature and if Tty is influenced by insulation of the ear. Thirty-one participants (two females) were exposed to room (23.2 ± 0.4 °C) and low (−18.7 ± 1.0 °C) ambient temperature for 10 min using a randomized cross-over design. Tty was measured using an epitympanic probe (M1024233, GE Healthcare Finland Oy) and oesophageal temperature (Tes) with an oesophageal probe (M1024229, GE Healthcare Finland Oy) inserted into the lower third of the oesophagus. Ten participants wore ear protectors (Arton 2200, Emil Lux GmbH & Co. KG, Wermelskirchen, Switzerland) to insulate the ear from ambient air. During exposure to room temperature, mean Tty increased from 33.4 ± 1.5 to 34.2 ± 0.8 °C without insulation of the ear and from 35.0 ± 0.8 to 35.5 ± 0.7 °C with insulation. During exposure to low ambient temperature, mean Tty decreased from 32.4 ± 1.6 to 28.5 ± 2.0 °C without insulation and from 35.6 ± 0.6 to 35.2 ± 0.9 °C with insulation. The difference between Tty and Tes at low ambient temperature was reduced by 82 % (from 7.2 to 1.3 °C) with insulation of the ear. Epitympanic temperature measurements are influenced by ambient temperature and deviate from Tes at room and low ambient temperature. Insulating the ear with ear protectors markedly reduced the difference between Tty and Tes and improved the stability of measurements. The use of models to correct Tty may be possible, but results should be validated in larger studies.

Climbing has become an increasingly popular sport, and the number of accidents is increasing in parallel. We aim at describing the characteristics of climbing accidents leading to severe (multisystem) trauma using data from the International Alpine Trauma Registry (IATR) and at reporting the results of a systematic review of the literature on the epidemiology, injury pattern, severity and prevention of climbing accidents. We found that climbing accidents are a rare event, since approximately 10% of all mountain accidents are climbing related. Climbing accidents mainly affect young men and mostly lead to minor injuries. Fall is the most common mechanism of injury. Extremities are the most frequently injured body part. However, in multisystem climbing-related trauma, the predominant portion of injuries are to head/neck, chest and abdomen. The fatality rate of climbing accidents reported in the literature varies widely. Data on climbing accidents in general are very heterogeneous as they include different subspecialties of this sport and report accidents from different regions. A number of risk factors are accounted for in the literature. Appropriate training, preparation and adherence to safety standards are key in reducing the incidence and severity of climbing accidents.