In hypobaric hypoxia (HH) at high altitude, the immune responses are changed probably due to oxidative stress-induced production of free radicals and nonradicals. Vitamin E is an antioxidant and protects the cells from oxidative damage. The present study was carried out to study the antioxidant role of vitamin E on the immune changes induced by oxidative stress in HH at high altitude. Select immune responses (phagocytic activity of white blood cell [WBC], cytotoxic activity of splenic mononuclear cells [MNCs], and delayed type of hypersensitivity [DTH]) and hematological changes (total count and differential count [DC] of WBC) were measured in male rats exposed to intermittent HH (at 5486.4 m in a simulated chamber for 8 hours/d for 6 consecutive days) and in normobaric condition with and without p.o. administration of vitamin E in three different doses (20, 40, and 60 mg/kg body weight). The increase of phagocytic activity of blood WBC, and reduction of cytotoxic activity of splenic MNC and DTH response were observed in rats exposed to HH. After the administration of vitamin E at different doses, the immune changes were blocked in a dose-dependent manner. Exposure to HH also led to the elevation of serum corticosterone (CORT), which was arrested after administration of vitamin E. The results indicate that the immune changes in HH at high altitude are probably mediated by the production of free radicals and nonradicals, and vitamin E can block these immune changes by its reactive oxygen species quenching effects.
Aims: Changes in emotions associated with mountain treks have rarely been reported. This study examined emotional state changes in sixth-grade elementary school students before and after a 3-day high-altitude mountain trek from the trailhead (2140 m) to Xue Mountain (3886 m) in Taiwan. Methods: In June 2011, 201 students participated in the trek. The round-trip distance was 21.8 km. The age, gender, blood group, and family configuration of the participants were documented before the trek. A 36-item short-form survey instrument, including the Mood and Anxiety Symptom Questionnaire and the Positive and Negative Affect Scale for Children, was used to evaluate the participants' emotional states (happiness, anticipation, sadness, and anger). The participants answered the questionnaires 1 month before and 1 week after the trek. A Likert scale was used to evaluate individual items (range 1–4; from strongly disagree to strongly agree). We calculated scores for each index before and after the trek. The incidence and presentation of acute mountain sickness (AMS) among the participants was also studied and published previously. Results: In total, 187 (112 boys and 75 girls) participants (mean age 11.9 ± 0.4 years) completed the trek and the survey. The sadness and anger scores (negative emotions) were significantly lower after than before the trek (39.5 vs. 36.6; p < 0.01). The happiness and anticipation scores (positive emotions) before and after the trek did not differ significantly (49.9 vs. 48.9; p = 0.11). No participant used AMS prophylaxis, while 78 participants met the AMS criteria. Negative emotions decreased more in those with AMS than without AMS (−4.6 vs. −1.8; p = 0.04), and the use of medications or acetazolamide did not alter the emotions. Conclusions: A 3-day high-altitude mountain trek can reduce children's negative emotions. Negative emotions decreased more in those with AMS, whereas medications or acetazolamide did not alter their emotions.
Background: Because of the limited evidence available, recommendations for defibrillation of hypothermic patients vary among published guidelines. Aim: To report successful defibrillation of four severely hypothermic patients with witnessed cardiac arrest. Results: During a four-year period from 2014 to 2017, four of five hypothermic patients admitted to our institution with a history of sudden, unexpected ventricular fibrillation (core temperature: 24°C–27°C) were successfully defibrillated. Restoration of spontaneous circulation (ROSC) was possible after a single defibrillator shock (two patients) or during prolonged advanced life support cardiopulmonary resuscitation (two patients). Our patients and additional cases identified in the literature indicate that successful defibrillation is predominantly found in hypothermic patients with a core temperature above 24°C. Conclusions: Our data demonstrate that successful defibrillation and ROSC are possible in selected patients with severe accidental hypothermia and are perhaps more common than widely believed. These findings are of particular importance for mountain and wilderness rescue missions when transfer of an arrested patient to the nearest hospital providing extracorporeal rewarming is not possible. An automatic external defibrillator should be part of the medical equipment on any search or mountain rescue mission, in which the victim may have sustained accidental hypothermia.
Aim: High altitude exposure alters biochemical, metabolic, and physiological features of heart and skeletal muscles, and hence has pathological consequences in these tissues. Central to these hypoxia-associated biochemical/metabolic shuffling are energy deficit accumulation of free radicals and ensuing oxidative damage in the tissue. Recent preclinical/clinical studies indicate sphingosine-1-phosphate (S1P) axis, comprising S1P G protein coupled receptors (S1PR 1–5 ) and its synthesizing enzyme—sphingosine kinase (SphK) to have key regulatory roles in homeostatic cardiac and skeletal muscle biology. In view of this, the aim of the present study was to chart the initiation and progression of biochemical/metabolic shuffling and assess the coincident differential modulation of S1PR (1–5) expression and total SphK activity in cardiac and skeletal muscles from rats exposed to progressive hypobaric hypoxia (HH; 21,000 feet for 12, 24, and 48 hours). Results: HH-associated responses were evident as raised damage markers in plasma, oxidative stress, decreased total tissue protein, imbalance of intermediate metabolites, and aerobic/anaerobic enzyme activities in cardiac and skeletal muscles (gastrocnemius and soleus) culminating as energy deficit. Conclusion: Cardiac and gastrocnemius muscles were more susceptible to hypoxic environment than soleus muscle. These differential responses were directly and indirectly coincident with temporal expression of S1PR (1–5) and SphK activity.
High altitude-induced gastrointestinal (GI) problems are potentially life-threatening. GI tract bleeding and inflammation are the major problems induced by hypobaric hypoxia (HH). In this study, effects of acute exposure to HH up to 14 days at 7620 m on GI immune function have been studied. To fulfill these objectives, Sprague-Dawley (SD) rats were divided into five groups namely Control and HH exposed (1, 3, 7, and 14 days). All groups except control were exposed to 7620 m of HH in an animal decompression chamber for the respective time intervals. Different degrees of intestinal mucosal damage in terms of increased mucosal permeability and disruption of intestinal villi were observed for different time intervals. HH exposure also upregulated secretory immunoglobulin A (sIgA) and proinflammatory cytokines in GI lavage along with proinflammatory markers such as toll-like receptor 4 (TLR4) and inducible nitric oxide synthase (iNOS). HH exposure of rats for 7 days significantly increased interleukin-17 (IL-17) and natural killer (NK) cell and dendritic cell populations compared with unexposed control rats. However, the number of naive T cells was significantly decreased in Peyer's patches. Our results connect HH to GI immune axis and highlight Th17 cells and proinflammatory molecules as potential therapeutic targets to counteract HH-induced GI dysfunction.
Introduction: Educational projects in mountain rescue in Nepal have a long tradition. They are usually led by Western experts who train their Nepalese colleagues using teams of people with diverse cultural background. To better understand the challenges of these encounters, we conducted a prospective cohort study during the first mountain rescue instructor course in Nepal. Methods: Western instructors (WIs) and Nepalese instructor candidates (NICs) were asked to self-assess their intercultural competence with the help of questionnaires. The responses were compared and analyzed for differences between WIs and NICs and differences in a pre–post assessment of the WIs. In addition, semistructured interviews were conducted with randomly selected NICs. Results: We found significant differences in communication styles between NICs and WIs: NICs showed a preference to establish relationships before discussing business and not to speak openly in conflict situations. WIs were much more direct and preferred dispassionate exchanges. In an assessment after the course, WIs had changed their attitude toward the host culture. Conclusions: We found differences in communication styles between WIs and NICs that are relevant to globalized medical education. Faculty members should be prepared before implementing medical training abroad and should have time to experience the host culture.
Exposure to high altitude activates several complex and adaptive mechanisms aiming to protect human homeostasis from extreme environmental conditions, such as hypoxia and low temperatures. Short-term exposure is followed by transient hyperglycemia, mainly triggered by the activation of the sympathetic system, whereas long-term exposure results in lower plasma glucose concentrations, mediated by improved insulin sensitivity and augmented peripheral glucose disposal. An inverse relationship between altitude, diabetes, and obesity has been well documented. This is the result of genetic and physiological adaptations principally to hypoxia that favorably affect glucose metabolism; however, the contribution of financial, dietary, and other life-style parameters may also be important. According to existing evidence, people with diabetes are capable of undertaking demanding physical challenges even at extreme altitudes. Still, a number of issues should be taken into account, including the increased physical activity leading to changes in insulin demands and resistance, the performance of measurement systems under extreme weather conditions and the potential deterioration of metabolic control during climbing expeditions. The aim of this review is to present available evidence in the field in a comprehensive way, beginning from the physiology of glucose homeostasis adaptation mechanisms to high altitudes and ending to what real life experience has taught us.
Introduction: Hypothermia and frostbite occur when there is a significant decrease in central and peripheral body temperature in individuals exposed to cold windy conditions, often at high altitude or in a mountain environment. Portable hyperbaric chambers increase the barometric pressure and thereby the partial pressure of oxygen inside the chamber, and their use is a well-known treatment for altitude illness. This study aims to show that a portable hyperbaric chamber could also be used to treat hypothermia and frostbite in the field, when rescue or descent is impossible or delayed. Methods: During a European research program (SOS-MAM, Flow Pulse study) measurements were taken from 27 healthy nonacclimatized voluntary subjects (21 men, 6 women, mean age 41 ± 17) at an altitude of 3800 m (Chamonix Mountain Lab, Aiguille du Midi, France) right before and immediately after spending 1 hour in a portable hyperbaric chamber at 300 mbar. We measured digital cutaneous temperature (Tcut), digital cutaneous blood flow (Fcut), digital tissue oxygenation (T c PO 2 ), blood oxygen saturation (S p O 2 ), heart rate, and core temperature. Air temperature inside the chamber (Tchamb) was measured throughout the whole session. Results: We observed significant increases in Tchamb: 9.3°C compared with the outside temperature, Tcut: +7.5°C (±6.2°C 71%), Fcut: +58 PU (±89) (+379%), T c PO 2 : +18 mmHg (±11.9) (304%), and S p O 2 : 13%. Conclusion: This study shows that a portable hyperbaric chamber can be used to treat frostbite and/or hypothermia in the field at altitude when descent or rescue is impossible or even simply delayed.
Understanding the process of successful adaptation to high altitude provides valuable insight into the pathogenesis of conditions associated with impaired oxygen uptake and utilization. Prepubertal children residing at low altitude show a reduced cerebrovascular response to exercise in comparison to adults, and a transient uncoupling of cerebral blood flow to changes in the partial pressure of end-tidal CO 2 (P ET CO 2 ); however, little is known about the cerebrovascular response to exercise in high-altitude native children. We sought to compare the cerebral hemodynamic response to acute exercise between prepubertal children residing at high and low altitude. Prepubertal children ( n = 32; 17 female) of Sherpa descent (Sherpa children [SC]) at high altitude (3800 m, Nepal) and maturational-matched ( n = 32; 20 female) children (lowland children [LLC]) residing at low altitude (342 m, Canada). Ventilation, peripheral oxygen saturation (S p O 2 ), P ET CO 2, and blood velocity in the middle and posterior cerebral arteries (MCA v and PCA v ) were continuously measured during a graded cycling exercise test to exhaustion. At baseline (BL), P ET CO 2 (−19 ± 4 mmHg, p 0.001), but not in LLC ( R 2 = 0.03, p = 0.10). Our findings demonstrate a similar increase in intra-cranial perfusion during exercise in prepubertal SC, despite differential BL values and changes in P ET CO 2 and S p O 2 .
Locomotion during ascent requires higher energy consumption than on flat terrain. Locomotion efficiency decreases in snowy terrain, with changes in the biomechanical pattern of walking. This study aims to evaluate differences in both cardiorespiratory responses and energy expenditure between locomotion over snowy terrain with an established footstep pathway (FP) and fresh snow (FS) that has not previously been compacted. Fifteen volunteers with experience in mountain activities at a competition level and a regular training schedule of up to 10 hours a week participated in the study. Estimated maximal theoretical oxygen consumption showed a mild increase (2.6%, 95% confidence interval: 0.9%–4.5%, t = 3.2, p = 0.005) when subjects followed the FP compared with FS. More time was necessary to complete locomotion in FS (256 ± 30 seconds) than FP (225 ± 29 seconds; p = 0.01). Uphill walking velocity increased by 0.43 ± 0.11 km/h ( t = 4.2, p = 0.01) in FP compared with FS; and the FS respiratory rate was higher (by 2.3 ± 2.4 beats/min, t = 4.0, p = 0.001). For a same itinerary, locomotion in snow that has not been compacted before requires more time and represents a higher energetic cost, either at maximal or submaximal intensities. This should be considered in scheduling mountain ascents as part of the safety strategies. Climbing on virgin snow impedes developing maximal aerobic power, so athletes must regard the value of strength work of lower limbs to improve performance. Indirect calculation of maximal oxygen consumption based on time to complete locomotion in FP can have practical application as a field test.
We examined the hypothesis that an expiratory resistance mask containing a small amount of dead space (ER/DS) would reduce the apnea–hypopnea index (AHI) during sleep, attenuate the severity of acute mountain sickness (AMS), and offset decrements in cognitive function compared with a sham mask. In a double-blinded, randomized, sham-controlled, crossover design, 19 volunteers were exposed to two nights of normobaric hypoxia (F I O 2 = 0.125), using a ER/DS mask (3.5 mm restrictive expiratory orifice; 125 mL DS volume) and sham mask (zero-flow resistance; 50 mL DS volume). Cognitive function, AMS, and ventilatory acclimatization were assessed before and after the 12-hour normobaric hypoxia exposure. Polysomnography was conducted during sleep. AHI was reduced using the ER/DS sleep mask compared with the sham (30.1 ± 23.9 events·hr −1 vs. 58.9 ± 34.4 events·hr −1 , respectively; p = 0.01). Likewise, oxygen desaturation index and headache severity were reduced (both p < 0.05). There were also benefits on limiting the hypoxia-induced reductions in select measures of reaction speed and attention ( p < 0.05). Our study indicates that a simple noninvasive and portable ER/DS mask resulted in reductions (49%) in AHI, and reduced headache severity and aspects of cognitive decline. The field applications of this ER/DS mask should be investigated before recommendations can be made to support its benefit for travel to high altitude.
We compared the decrease in maximal heart rate (HRmax) from normoxia to normobaric (NH) and hypobaric (HH) hypoxia, respectively, in trained and untrained subjects ( n = 187). HRmax data in normoxia and NH ( n = 55) or HH ( n = 26) were collected from 81 publications. No study directly compared HRmax in NH and HH. Concomitant arterial oxygen saturation (SaO 2 ) and HRmax data were found in 60 studies. Overall, the results showed that the higher the desaturation, the greater the decrease in HRmax. Since desaturation appeared to be slightly higher during HH versus NH and was higher in trained than in untrained subjects, the decrease in HRmax tended ( p = 0.07) to be higher in trained subjects in HH than in NH (e.g., −12.7 bpm vs. −8.6 bpm at 4000 m), whereas in untrained subjects the difference was negligible (−9.9 bpm vs. −8.3 bpm). To conclude, when compared with normoxia, the decrease in HRmax was slightly higher in HH than in NH in trained subjects. However, this result has to be confirmed and from a practical point of view, one may question the significance of this difference as well as the relevance of using different HR values for prescribing training intensity during exercise performed in NH or in HH.