Symptoms Of Acute Mountain Sickness Research Articles

Menstrual cycle does not impact the hypoxic ventilatory response and acute mountain sickness prediction

The relationship between the variations in ovarian hormones (i.e., estrogens and progesterone) and the hypoxic ventilatory response (HVR) remains unclear. HVR is a key adaptive mechanism to high altitude and has been proposed as a predictor for acute mountain sickness (AMS). This study aimed to explore the effects of hormonal changes across the menstrual cycle on HVR. Additionally, it assessed the predictive capacity of HVR for AMS and examined whether a particular menstrual phase could enhance its predictive accuracy. Thirteen eumenorrheic women performed a pure nitrogen breathing test near sea level, measuring HVR and cerebral oxygenation in early follicular, late follicular, and mid-luteal phases. Oxidative stress and ovarian hormone levels were also measured. AMS symptoms were evaluated after spending 14 h, including one overnight, at an altitude of 3,375 m. No differences in HVR, ventilation, peripheral oxygen saturation, or cerebral oxygenation were observed between the three menstrual cycle phases. Moreover, these parameters and the oxidative stress markers did not differ between the women with or without AMS (31% vs 69%), regardless of the menstrual cycle phase. In conclusion, ventilatory responses and cerebral oxygenation in normobaric hypoxia were consistent across the menstrual cycle. Furthermore, these parameters did not differentiate women with or without AMS.

Incidence and risk factors of acute mountain sickness during ascent to Hoh Xil and the physiological responses before and after acclimatization

Abstract OBJECTIVES: Ascending to altitudes >2500 m may lead to acute mountain sickness (AMS). METHODS: The demographics, height, weight, body mass index (BMI), smoking, and alcohol consumption of 104 healthy controls were collected in Chengdu (500 m). Heart rate (HR), saturation of pulse oxygen (SpO2), and AMS-related symptoms were collected in Hoh Xil (4200 m). A headache with Lake Louise score ≥3 was defined as AMS. RESULTS: The incidence of AMS was 60.58%. AMS group had a lower SpO2 and higher HR than non-AMS group. Alcohol consumption seemed a risk factor for AMS. There was no difference in the BMI, age, height, weight, and smoking between AMS and non-AMS groups. The most common AMS symptom was headache, followed by dyspnea, insomnia, dizziness, lassitude, and anorexia. Women were prone to suffer from dizziness. The value of SpO2 and HR was improved both in AMS and non-AMS groups after hypoxia acclimatization, and the value showed greater improvement in AMS group. Oxygen therapy decreased the AMS-induced tachycardia, which had no any effect on SpO2 and symptom alleviating time. CONCLUSION: Lower SpO2 and higher HR following exposure to high altitude were associated with AMS susceptibility. The anthropometric data changes were larger in AMS group than non-AMS group before and after hypoxia acclimatization.

Impact of Acute Short-term Hypobaric Hypoxia on Anterior Chamber Geometry

Précis: Hypobaric hypoxia, the major environmental factor at high altitudes, has been observed to induce pupil miosis and widening of the anterior chamber angle. This environment may be safe for individuals with narrow angle and deserves further study. Purpose: This study aimed to quantify anterior chamber biometric parameters before and after acute short-term, effortless exposure to hypobaric hypoxia (HH) in healthy lowlanders using swept-source anterior segment optical coherence tomography (SS AS-OCT). Methods: This prospective study included 25 healthy young lowlanders (50 eyes) who underwent SS AS-OCT measurements and intraocular pressure (IOP) assessments under baseline sea-level conditions (T1).They were then passively exposed to simulated 4000 m above sea level for 3 hours and underwent Acute mountain sickness (AMS) symptoms evaluation and IOP measurement after 2-hours exposure to HH (T2).Repeat SS AS-OCT measurements and IOP assessments were taken within 15 minutes after leaving the hypobaric chamber (T3). Anterior segment parameters including anterior chamber depth (ACD),lens vault (LV),angle opening distance (AOD500), trabecular-iris space area (TISA500), angle recess area (ARA500) at 500 μm from the scleral spur, iris curvature (IC), iris volume (IV), pupil diameter (PD), and central corneal thickness (CCT) were obtained through SS AS-OCT. These repeated measurements were compared using linear mixed model analysis. Results: In comparison to sea level, both IOP (16.4±3.4 vs. 14.9±2.4 mm Hg, P=0.029) and PD (5.36±0.77 vs. 4.78±0.89 mm, P=0.001) significantly decreased after exposure to HH. Significant post-HH changes (Mean difference (95% CI)) were observed in AOD500 (0.129 (0.006, 0.252), P=0.04), TISA500 (0.059 (0.008, 0.11), P=0.025), ARA500 (0.074 (0.008, 0.141), P=0.029), IV (1.623 (0.092, 3.154), P=0.038), and IC (−0.073 (−0.146, 0.001), P=0.047), while CCT, ACD, and LV remained stable. After adjusting for age, post-HH variations in AOD500 (Beta=0.553, 95% CI: 0.001, 1.105, P=0.048) and TISA500 (Beta=0.256, 95% CI: 0.02, 0.492, P=0.034) were associated with decreased IC but were not related to lowered arterial oxygen pressure or IV increase per millimeter of pupil miosis (IV/PD). These differences in anterior segment parameters were neither correlated with differences in IOP nor AMS. Conclusion: After short-term, effortless exposure to hypobaric hypoxia, pupil miosis occurred with widening of the anterior chamber angle and decreased IC. These changes in anterior chamber angle parameters were associated with decreased IC but did not correlate with the post-hypobaric variations in IV/PD, IOP, or AMS.

Female performance in skyrunning: biological and psychosocial aspects.

Skyrunning is a running sport performed in a mountain environment, characterized by reaching an altitude of at least 2000 meters above sea level, where symptoms of acute mountain sickness can appear. This sport has recently gained significant popularity, with an increasing number of participants. The purpose of this study was to analyze female performances in the different subdisciplines of skyrunning. The study considered official results of 173 races of the Italian Skyrunning Federation held in 2021 and 2022. Female and male biological sexes, as well as age and race time of 13,850 participants who crossed the finish line were analyzed. Female athletes represented 16% of finishers and showed a preference for competitions of medium distances (skyrace and skytrail). They were younger and more self-selected among the most talented in terms of performance compared to males (P<0.001). Males showed significantly faster race times than females in all the competitions (P<0.05). Race times of female winners were on average 123-144% higher than those of male counterparts. In both sexes, winners were predominantly young; female winners were more represented among the older age-groups in skyrace and vertical kilometer (P<0.05). Regardless of biological differences affecting female sporting performances, gender inequalities are still widely present despite the progress made in every sport. Since gender equality in sports cannot be separated from gender equality in the sociocultural sphere, it is necessary to invest economically and take proactive measures to achieve real equity, both in the macro-social and sports contexts.

Oral quercetin nanoparticles in hydrogel microspheres alleviate high-altitude sleep disturbance based on the gut-brain axis

High-altitude sleep disturbance is a common symptom of acute mountain sickness, which can be alleviated via modulation of the gut-brain axis. Quercetin (Que) is used to modulate gut microbiota and serves as a potential drug to regulate the gut-brain axis, but the poor solubility and bioavailability affect its biological functions. Here, Que nanoparticles (QNPs) were prepared with zein using an antisolvent method, and QNP-loaded calcium alginate hydrogel microspheres (QNP@HMs) were prepared using electrospinning technology to improve the gastrointestinal stability and intestinal adhesion of QNPs. In the mouse model of high-altitude sleep disturbance, oral administration of QNP@HMs before the mice entering high altitude prolonged sleep duration, improved blood cell recovery, spontaneous behavior and short-term memory, and reduced such inflammation factors as TNF-α and iNOS. Moreover, QNP@HMs enhanced the abundance of probiotics in the gut, including Lactobacillus and Lachnospira, and reduced intestinal inflammation. However, in the mice after gut sterilization by long-term oral antibiotics, QNP@HMs showed no therapeutic effect. QNP@HMs are a promising medication for the prevention of high-altitude sleep disturbance based on the gut-brain axis.

High myopia at high altitudes.

Background: Optic nerve sheath diameter (ONSD) increases significantly at high altitudes, and is associated with the presence and severity of acute mountain sickness (AMS). Exposure to hypobaria, hypoxia, and coldness when hiking also impacts intraocular pressure (IOP). To date, little is known about ocular physiological responses in trekkers with myopia at high altitudes. This study aimed to determine changes in the ONSD and IOP between participants with and without high myopia (HM) during hiking and to test whether these changes could predict symptoms of AMS. Methods: Nine participants with HM and 18 without HM participated in a 3-day trek of Xue Mountain. The ONSD, IOP, and questionnaires were examined before and during the trek of Xue Mountain. Results: The ONSD values increased significantly in both HM (p = 0.005) and non-HM trekkers (p = 0.018) at an altitude of 1,700m. In the HM group, IOP levels were greater than those in the non-HM group (p = 0.034) on the first day of trekking (altitude: 3,150m). No statistically significant difference was observed between the two groups for the values of ONSD. Fractional changes in ONSD at an altitude of 1,700m were related to the development of AMS (r pb = 0.448, p = 0.019) and the presence of headache symptoms (r pb = 0.542, p = 0.004). The area under the ROC curve for the diagnostic performance of ONSD fractional changes at an altitude of 1,700m was 0.859 for predicting the development of AMS and 0.803 for predicting the presence of headache symptoms. Conclusion: Analysis of changes in ONSD at moderate altitude could predict AMS symptoms before an ascent to high altitude. Myopia may impact physiological accommodation at high altitudes, and HM trekkers potentially demonstrate suboptimal regulation of aqueous humor in such environments.

The impact of sleeping in an elevated upper body position during acclimatization to high altitude on acute mountain sickness and pulmonary artery systolic pressure

Background: The effect of sleeping positions during acclimatization to high altitude on Acute Mountain Sickness (AMS) and High Altitude Pulmonary Edema (HAPE) is unknown. We tested whether sleeping with the upper body raised by 5° reduces prevalence and severity of symptoms of AMS as well as of elevated pulmonary artery systolic pressure (PASP) values as a risk factor of HAPE. Methods: Randomly assigning trekking tourist volunteers n = 44 (25 m, 19 f; mean age 42.9 yr) sleeping at 4280 m or 5170 m to the experimental group (upper body elevated by 5°), or to the control group. After exclusion of other reasons for AMS-like symptoms those assumed to be related to AMS were rated by Lake Louise Score questionnaire in the evening and the following morning of the study. Transthoracic echocardiography was performed on both occasions to estimate PASP. Results: In the study group, symptoms of AMS were significantly reduced in younger subjects (p = 0.021), prevalence of AMS was reduced in women (p = 0.156), and PASP values were significantly reduced in older subjects and men (p = 0.032; p = 0.031 respectively). Conclusion: Results suggest that sleeping with the upper body in elevated position during a high altitude ascent may benefit those suffering from AMS or at risk of HAPE due to elevated PASP values.

Influence of Smoking and Alcohol Habits on Symptoms of Acute Mountain Sickness on Mount Fuji: A Questionnaire Survey-Based Pilot Study.

Horiuchi, Masahiro, Satomi Mitsui, and Tadashi Uno. Influence of smoking and alcohol habits on symptoms of acute mountain sickness on Mount Fuji: a questionnaire survey-based pilot study. High Alt Med Biol 00:000-000, 2024. Background: Acute cigarette smoking or alcohol intake would cause opposing vasculature effects that may influence acute mountain sickness (AMS). The present study aimed to investigate the effects of smoking and alcohol consumption behaviors, and acute smoking and consuming alcohol during ascent on AMS on Mount Fuji. Methods: This questionnaire survey study included 887 participants who climbed Mount Fuji and obtained information regarding sex, age, and smoking and alcohol habits, including behavior during ascent. Results: AMS prevalence was 45% for all participants. A univariate analysis revealed that younger participants (20-29 years) were associated with increased AMS prevalence (effect size [ES] = 0.102, p = 0.057) and severity (ES = 0.18, p = 0.01). A prediction model using multiple logistic regression indicated that several factors influenced AMS risk: younger age (p = 0.001), daily smoking habits (p = 0.021), no smoking (p = 0.033), or alcohol consumption during ascent (p = 0.096). Alcohol consumption during ascent had no effect on the increased AMS risk in younger participants (20-29 years), while alcohol consumption during ascent increased AMS risk for middle-age participants (50-59 years). Conclusion: Younger individuals are more likely to experience AMS. Smoking habits are associated with an increased AMS risk. It may be recommended that middle-aged climbers should ascend without consuming alcohol.

Exercise and hypoxia-induced hypercoagulability is counterbalanced in women in part by decreased platelet reactivity

Hypoxia plays an important role in several pathologies, e.g. chronic obstructive pulmonary disease and obstructive sleep apnea syndrome, and is linked to an increased thrombosis risk. Furthermore, oxygen deprivation is associated with hypercoagulability.In this study, we investigated the effect of gender and exercise on the coagulation potential under hypoxic conditions at high altitude by assessing thrombin generation (TG) and platelet activation. Hereto, ten healthy volunteers were included (50 % male, median age of 27.5 years). The measurements were conducted first at sea level and then twice at high altitude (3883 m), first after a passive ascent by cable car and second after an active ascent by a mountain hike.As expected, both the passive and active ascent resulted in a decreased oxygen saturation and an increased heart rate at high altitude. Acute mountain sickness symptoms were observed independently of the ascent method. After the active ascent, platelet, white blood cell and granulocyte count were increased, and lymphocytes were decreased, without a gender-related difference. FVIII and von Willebrand factor were significantly increased after the active ascent for both men and women. Platelet activation was reduced and delayed under hypobaric conditions, especially in women. TG analysis showed a prothrombotic trend at high altitude, especially after the active ascent. Women had a hypercoagulable phenotype, compared to men at all 3 timepoints, indicated by a higher peak height and endogenous thrombin potential (ETP), and shorter lag time and time-to-peak. In addition, ETP and peak inhibition by thrombomodulin was lower in women after the active ascent, compared to men. Interestingly, data normalisation for subject baseline values indicated an opposing effect of altitude-induced hypoxia on α2-macroglobulin levels and TG lag time between men and women, decreasing in men and increasing in women.We conclude that hypoxia increases TG, as well as FVIII and VWF levels in combination with exercise. In contrast, platelets lose their responsiveness at high altitude, which is most pronounced after heavy exercise. Women had a more pronounced prothrombotic phenotype compared to men, which we theorize is counterbalanced under hypobaric conditions by decreased platelet activation.

Potential Candidate Molecules of Past and Present for Combating High Altitude Hypoxia Induced Maladies

Hypobaric hypoxia occurs at high altitudes where barometric pressure is low causing insufficient supply of oxygen leading to many high-altitude illnesses like acute mountain sickness (AMS), high altitude pulmonary edema (HAPE), high altitude cerebral edema (HACE) etc.Medications have been applied to treat and prevent injuries caused by HBH, showing anti-inflammatory, anti-edemagenic, and antioxidant properties. AMS symptoms, such as headache, nausea, weariness, usually go away in 1-2 days. HACE causes brain swelling, elevated intracranial pressure, resulting in confusion, stupor, ataxia, and death.Acetazolamide, dexamethasone, nifedipine are the drugs used for treatment acting oncarbonic anhydrase enzyme, calcium channels.Acetazolamide increases arterial partial pressure of oxygen.Nifedipine relaxes vascular smooth muscles and increases blood flow. Some drugscause side effects also like dizziness, diuresis, nausea, malaise, etc. Hence, a new drug search is needed to find more targeted and fewer side effects for faster relief and better health at high altitudes.

Intermittent hypoxia training effectively protects against cognitive decline caused by acute hypoxia exposure.

Intermittent hypoxia training (IHT) is a promising approach that has been used to induce acclimatization to hypoxia and subsequently lower the risk of developing acute mountain sickness (AMS). However, the effects of IHT on cognitive and cerebrovascular function after acute hypoxia exposure have not been characterized. In the present study, we first confirmed that the simplified IHT paradigm was effective at relieving AMS at 4300m. Second, we found that IHT improved participants' cognitive and neural alterations when they were exposed to hypoxia. Specifically, impaired working memory performance, decreased conflict control function, impaired cognitive control, and aggravated mental fatigue induced by acute hypoxia exposure were significantly alleviated in the IHT group. Furthermore, a reversal of brain swelling induced by acute hypoxia exposure was visualized in the IHT group using magnetic resonance imaging. An increase in cerebral blood flow (CBF) was observed in multiple brain regions of the IHT group after hypoxia exposure as compared with the control group. Based on these findings, the simplified IHT paradigm might facilitate hypoxia acclimatization, alleviate AMS symptoms, and increase CBF in multiple brain regions, thus ameliorating brain swelling and cognitive dysfunction.

Potential plasma biomarkers at low altitude for prediction of acute mountain sickness.

Ascending to high altitude can induce a range of physiological and molecular alterations, rendering a proportion of lowlanders unacclimatized. The prediction of acute mountain sickness (AMS) prior to ascent to high altitude remains elusive. A total of 40 participants were enrolled for our study in the discovery cohort, and plasma samples were collected from all individuals. The subjects were divided into severe AMS-susceptible (sAMS) group, moderate AMS-susceptible (mAMS) group and non-AMS group based on the Lake Louise Score (LLS) at both 5000m and 3700m. Proteomic analysis was conducted on a cohort of 40 individuals to elucidate differentially expressed proteins (DEPs) and associated pathways between AMS-susceptible group and AMS-resistant group at low altitude (1400m) and middle high-altitude (3700m). Subsequently, a validation cohort consisting of 118 individuals was enrolled. The plasma concentration of selected DEPs were quantified using ELISA. Comparative analyses of DEPs among different groups in validation cohort were performed, followed by Receiver Operating Characteristic (ROC) analysis to evaluate the predictive efficiency of DEPs for the occurrence of AMS. The occurrence of the AMS symptoms and LLS differed significantly among the three groups in the discovery cohort (p<0.05), as well as in the validation cohort. Comparison of plasma protein profiles using GO analysis revealed that DEPs were primarily enriched in granulocyte activation, neutrophil mediated immunity, and humoral immune response. The comparison of potential biomarkers between the sAMS group and non-AMS group at low altitude revealed statistically higher levels of AAT, SAP and LTF in sAMS group (p=0.01), with a combined area under the curve(AUC) of 0.965. Compared to the mAMS group at low altitude, both SAP and LTF were found to be significantly elevated in the sAMS group, with a combined AUC of 0.887. HSP90-α and SAP exhibited statistically higher levels in the mAMS group compared to the non-AMS group at low altitude, with a combined AUC of 0.874. Inflammatory and immune related biological processes were significantly different between AMS-susceptible and AMS-resistant groups at low altitude and middle high-altitude. SAP, AAT, LTF and HSP90-α were considered as potential biomarkers at low altitude for the prediction of AMS.

Prevention of Acute Mountain Sickness (AMS) with particular emphasis on hydration: a review

Acute mountain sickness (AMS) causes a number of symptoms within the human body, associated with staying at altitudes higher than 2,500 meters above sea level without prior acclimatization. The human body begins to adapt its functioning to the conditions of hypobaric hypoxia in order to maintain homeostasis. Its disturbance can lead to respiratory failure, pulmonary, or cerebral oedema, and, consequently, death. The best method of AMS prevention is slow acclimatization. A high-carbohydrate diet, thermal protection, and pharmacological agents could be listed as additional prevention measures. The development of AMS is influenced by many factors such as ambient temperature, wind speed, altitude, physical preparation of participants, and appropriate protection against adverse effects of these factors. Nevertheless, both dehydration and overhydration may worsen the AMS symptoms. The body’s exposure to altitude and dehydration alone reduces aerobic performance. Appropriate hydration throughout a climb is necessary due to both intense physical exercise and a hypoxic environment.

Effect of ubiquinol on cardiorespiratory fitness during high-altitude acclimatization and de-acclimatization in healthy adults: the Shigatse CARdiorespiratory fitness study design.

Cardiorespiratory function influences exercise capacity and is an important determinant of high-altitude adaptation. Some studies have investigated the characteristics of changes in cardiorespiratory fitness during high-altitude acclimatization. However, studies on changes in cardiorespiratory fitness during high-altitude de-acclimatization are still lacking and have not yet been elucidated. Furthermore, few drugs have been studied to improve cardiorespiratory function during both processes. The Shigatse CARdiorespiratory Fitness (SCARF) study is a single-center, randomized, double-blind, placebo-control clinical trial to explore the effects of ubiquinol on cardiorespiratory fitness during high-altitude acclimatization and de-acclimatization in healthy adults. Participants will be randomly assigned 1:1 to ubiquinol 200 mg daily or a placebo for 14 days before departure until the end of data collection after return in 7 days. Cardiorespiratory fitness is the primary outcome, while acute mountain sickness and high-altitude de-acclimatization symptoms are secondary endpoints. In addition, laboratory measurements, including routine blood tests and serological measurements, will be performed. To the best of our knowledge, the SCARF study will be the first to reveal the changes in the cardiorespiratory fitness characteristics during high-altitude acclimatization and de-acclimatization. Furthermore, the results of this study will contribute to exploring whether ubiquinol supplementation could be beneficial for endurance exercise capacity at different altitudes and help improve adaptation to acute hypoxia and de-acclimatization. Clinical Trial Registration: This study has been registered in the Chinese Clinical Trial Register (www.chictr.org.cn) as ChiCTR2200059900 and ChiCTR2200066328.

SAFETY AND FEASIBILITY OF HYPOXIA EXPOSURE IN PATIENTS WITH PRIOR MYOCARDIAL INFARCTION

Objective: In mice, normobaric hypoxia exposure corresponding to 8,000 m altitude after myocardial infarction reactivated cardiomyocyte proliferation and improved left ventricular ejection fraction (LVEF). Translating these findings to patients might be limited by hypoxia-induced pulmonary hypertension and myocardial ischemia. Design and method: We conducted a feasibility and safety study at the: envihab facility in 4 patients who had experienced myocardial infarction with fully revascularized LAD-stenosis as culprit lesion 37-104 months prior study entry. Their peak VO2 ranged from 32 - 43 ml/kg/min. The study comprised a two-days baseline, 19 days normobaric hypoxia, and two-days recovery. We gradually lowered atmospheric oxygen to 0.118 FIO2, which is equivalent to 4500 m, and maintained that level for 4.5 days. We obtained transthoracic echocardiography, magnetic resonance imaging, and determined Troponin I, NTproBNP at baseline, during 0.118 FIO2, and recovery. Results: Except for symptoms of acute mountain sickness, hypoxia was well tolerated as severe adverse reactions did not occur and pulmonary hypertension rapidly abated during recovery. During the last 10 days of hypoxia, peripheral oxygen saturation was continuously &lt;90%. LVEF was 50.7±11.0 % (mean±SD) baseline, 57.6±11.2% at 0.118 FIO2, and 57.3±11.2% during recovery. Furthermore, echocardiographic LV global longitudinal strain was -15.28±5.4% at baseline and -17.28±7.56 % in recovery. Magnetic resonance imaging confirmed these findings. NTproBNP diminished (baseline: 203±209 pg/ml, 0.118 FIO2: 122±101/pg/ml, recovery: 85±66 pg/ml) and Troponin I concentrations remained in the reference range throughout the study. In the patient with the largest LVEF increase following hypoxia, an additional 12 weeks follow-up measurement showed stable improvements in LVEF (baseline: 36%, recovery: 48%, 12 weeks follow-up: 47%), left ventricular strain, NTproBNP, and exertional dyspnea. Conclusions: Our study provides evidence regarding safety and potential of hypoxia exposure after myocardial infarction and lays the foundation for future studies assessing hypoxia-influences on cardiac regeneration. However, our findings have to be interpreted with caution given the small sample size and the selected patient population.

Effect of different levels of acute hypoxia on subsequent oral glucose tolerance in males with overweight: A balanced cross-over pilot feasibility study.

Previous research has shown that ≤60 min hypoxic exposure improves subsequent glycaemic control, but the optimal level of hypoxia is unknown and data are lacking from individuals with overweight. We undertook a cross-over pilot feasibility study investigating the effect of 60-min prior resting exposure to different inspired oxygen fractions (CON FI O2 =0.209; HIGH FI O2 =0.155; VHIGH FI O2 =0.125) on glycaemic control, insulin sensitivity, and oxidative stress during a subsequent oral glucose tolerance test (OGTT) in males with overweight (mean (SD) BMI=27.6 (1.3) kg/m2 ; n=12). Feasibility was defined by exceeding predefined withdrawal criteria for peripheral blood oxygen saturation (SpO2 ), partial pressure of end-tidal oxygen or carbon dioxide and acute mountain sickness (AMS), and dyspnoea symptomology. Hypoxia reduced SpO2 in a stepwise manner (CON=97(1)%; HIGH=91(1)%; VHIGH=81(3)%, p < 0.001), but did not affect peak plasma glucose concentration (CON=7.5(1.8) mmol∙L-1 ; HIGH=7.7(1.1) mmol∙L-1 ; VHIGH=7.7(1.1) mmol∙L-1 ; p=0.777; η2 =0.013), plasma glucose area under the curve, insulin sensitivity, or metabolic clearance rate of glucose (p > 0.05). We observed no between-conditions differences in oxidative stress (p > 0.05), but dyspnoea and AMS symptoms increased in VHIGH (p < 0.05), with one participant meeting the withdrawal criteria. Acute HIGH or VHIGH exposure prior to an OGTT does not influence glucose homeostasis in males with overweight, but VHIGH is associated with adverse symptomology and reduced feasibility.

Circulating markers of intestinal barrier injury and inflammation following exertion in hypobaric hypoxia

ABSTRACT Hypoxia induced intestinal barrier injury, microbial translocation, and local/systemic inflammation may contribute to high-altitude associated gastrointestinal complications or symptoms of acute mountain sickness (AMS). Therefore, we tested the hypothesis that six-hours of hypobaric hypoxia increases circulating markers of intestinal barrier injury and inflammation. A secondary aim was to determine if the changes in these markers were different between those with and without AMS. Thirteen participants were exposed to six hours of hypobaric hypoxia, simulating an altitude of 4572 m. Participants completed two 30-minute bouts of exercise during the early hours of hypoxic exposure to mimic typical activity required by those at high altitude. Pre- and post-exposure blood samples were assessed for circulating markers of intestinal barrier injury and inflammation. Data below are presented as mean ± standard deviation or median [interquartile range]. Intestinal fatty acid binding protein (Δ251 [103-410] pg•mL−1; p = 0.002, d = 0.32), lipopolysaccharide binding protein (Δ2 ± 2.4 μg•mL−1; p = 0.011; d = 0.48), tumor necrosis factor-α (Δ10.2 [3-42.2] pg•mL−1; p = 0.005; d = 0.25), interleukin-1β (Δ1.5 [0-6.7] pg•mL−1 p = 0.042; d = 0.18), and interleukin-1 receptor agonist (Δ3.4 [0.4-5.2] pg•mL−1 p = 0.002; d = 0.23) increased from pre- to post-hypoxia. Six of the 13 participants developed AMS; however, the pre- to post-hypoxia changes for each marker were not different between those with and without AMS (p > 0.05 for all indices). These data provide evidence that high altitude exposures can lead to intestinal barrier injury, which may be an important consideration for mountaineers, military personnel, wildland firefighters, and athletes who travel to high altitudes to perform physical work or exercise.

Microcirculatory and Rheological Adaptive Mechanisms at High Altitude in European Lowlander Hikers and Nepalese Highlanders.

Physical activity at high-altitudes is increasingly widespread, both for tourist trekking and for the growing tendency to carry out sports and training activities at high-altitudes. Acute exposure to this hypobaric-hypoxic condition induces several complex adaptive mechanisms involving the cardiovascular, respiratory and endocrine systems. A lack of these adaptive mechanisms in microcirculation may cause the onset of symptoms of acute mountain sickness, a frequent disturbance after acute exposure at high altitudes. The aim of our study was to evaluate the microcirculatory adaptive mechanisms at different altitudes, from 1350 to 5050 m a.s.l., during a scientific expedition in the Himalayas. The main haematological parameters, blood viscosity and erythrocyte deformability were assessed at different altitudes on eight European lowlanders and on a group of eleven Nepalese highlanders. The microcirculation network was evaluated in vivo by conjunctival and periungual biomicroscopy. Europeans showed a progressive and significant reduction of blood filterability and an increase of whole blood viscosity which correlate with the increase of altitude (p < 0.02). In the Nepalese highlanders, haemorheological changes were already present at their residence altitude, 3400 m a.s.l. (p < 0.001 vs. Europeans). With the increase in altitude, a massive interstitial oedema appeared in all participants, associated with erythrocyte aggregation phenomena and slowing of the flow rate in the microcirculation. High altitude causes important and significant microcirculatory adaptations. These changes in microcirculation induced by hypobaric-hypoxic conditions should be considered when planning training and physical activity at altitude.

Diagnosis and Management of Mountain Sickness - A Review

Acute mountain sickness (AMS) is the most common form of illness at high altitude; however, it is still unclear whether age is a protective factor or a risk factor for the development of AMS in travellers. The condition generally occurs at altitudes higher than 8,000 feet (ft), or 2,500 meters (m), and is usually due to a lack of oxygen. A person who is not used to high altitudes is most at risk of developing altitude sickness. Mountain sickness is also called high altitude sickness, referring to the impact of environment on the body health at high elevation. Altitude illness is divided into 3 syndromes: acute mountain sickness, high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE). Mountain climbers are at risk of developing altitude sickness. Altitude sickness is caused by ascending too rapidly, which doesn't allow the body enough time to adjust to reduced oxygen and changes in air pressure. Symptoms include headache, vomiting, insomnia and reduced performance and coordination. Generally, it is classified into three categories based on the onset condition, namely acute mountain sickness, high-altitude cerebral edema (HACE) and high-altitude pulmonary edema (HAPE). Hypoxic sleep disruption contributes to the symptoms of acute mountain sickness. Hypoxemia at high altitude is most severe during sleep. The sickness signifies that the human body has yet to adapt to the environment at 2500 meters or above in elevation, where low air pressure and oxygen will impair body functions. Mild cases can be treated according to symptoms (such as with painkillers for a headache), which usually go away on their own within a few days. Medicines specific for altitude sickness are also available. Acetazolamide is used to prevent and reduce the symptoms of altitude sickness. This medication can decrease headache, tiredness, nausea, dizziness, and shortness of breath that can occur when you climb quickly to high altitudes.

Retinal microvasculature is a potential biomarker for acute mountain sickness.

Increased cerebral blood flow resulting from altered capillary level autoregulation at high altitudes leads to capillary overperfusion and then vasogenic cerebral edema, which is the leading hypothesis of acute mountain sickness (AMS). However, studies on cerebral blood flow in AMS have been mostly restricted to gross cerebrovascular endpoints as opposed to the microvasculature. This study aimed to investigate ocular microcirculation alterations, the only visualized capillaries in the central neural system (CNS), during early-stage AMS using a hypobaric chamber. This study found that after high altitude simulation, the optic nerve showed retinal nerve fiber layer thickening (P=0.004-0.018) in some locations, and the area of the optic nerve subarachnoid space (P=0.004) enlarged. Optical coherence tomography angiography (OCTA) showed increased retinal radial peripapillary capillary (RPC) flow density (P=0.003-0.046), particularly on the nasal side of the nerve. The AMS-positive group had the largest increases in RPC flow density in the nasal sector (AMS-positive, Δ3.21±2.37; AMS-negative, Δ0.01±2.16, P=0.004). Among multiple ocular changes, OCTA increase in RPC flow density was associated with simulated early-stage AMS symptoms (beta=0.222, 95%CI, 0.009-0.435, P=0.042). The area under the receiver operating characteristics curve (AUC) for the changes in RPC flow density to predict early-stage AMS outcomes was 0.882 (95%CI, 0.746-0.998). The results further confirmed that overperfusion of microvascular beds is the key pathophysiologic change in early-stage AMS. RPC OCTA endpoints may serve as a rapid, noninvasive potential biomarker for CNS microvascular changes and AMS development during risk assessment of individuals at high altitudes.