Occurrence Of Acute Mountain Sickness Research Articles

Neurofilament Light Chain Is Associated With Acute Mountain Sickness.

Neurological symptoms are common in acute mountain sickness (AMS); however, the extent of neuroaxonal damage remains unclear. Neurofilament light chain (NfL) is an established blood biomarker for neuroaxonal damage. To investigate whether plasma (p) NfL levels increase after simulated altitude exposure, correlate with the occurrence of AMS, and might be mitigated by preacclimatization. Healthy subjects were exposed to simulated high altitude (4500m) by the use of a normobaric hypoxic chamber at the University of Innsbruck two times, that is, within Cycle 1 (C1) over 12h, and within Cycle 2 (C2) for another 12h but with a random assignment to prior acclimatization or sham acclimatization. Before each cycle (measurement [M] 1 and 3) and after each cycle (M2 and M4), clinical data (arterial oxygen saturation [SaO2], heart rate, and Lake Louise AMS score [LLS]) and plasma samples were collected. pNfL was measured using single-molecule array (Simoa) technique. pNfL levels did not significantly change within each study cycle, but increased over the total study period (M1: 4.57 [3.34-6.39], M2: 4.58 [3.74-6.0], M3: 5.64, and M4: 6.53 [4.65-7.92] pg/mL, p<0.001). Subjects suffering from AMS during the study procedures showed higher pNfL levels at M4 (6.80 [6.19-8.13] vs. 5.75 [4.17-7.35], p=0.048), a higher total pNfL increase (2.88 [1.21-3.48] vs. 0.91 [0.53-1.48], p=0.022) compared to subjects without AMS. An effect of preacclimatization on pNfL levels could not be observed. pNfL increases alongside exposure to simulated altitude and is associated with AMS.

The application of supine bicycle exercise stress echocardiograph for identification of susceptibility to acute mountain sickness

Abstract Background Exposure to high altitude is likely to lead to acute mountain sickness (AMS). At present, there are no definite parameters that can accurately predict the occurrence of AMS. Objectives The purposes of this study are (1) to assess the relationship between stress echocardiographic parameters and AMS, (2) to identify the predictors of AMS at sea level by exercise stress echocardiography. Methods A total of 36 healthy adults were enrolled and underwent resting and exercise stress echocardiography on a supine bicycle at sea level. Heart rate (HR) and blood pressure (BP) were monitored during stress echocardiography. Left ventricular (LV) ejection fraction and E/e’ were calculated at rest and peak stage. Other right ventricular systolic function parameters and pulmonary artery pressure (PAP) were calculated at the same time, which included tricuspid regurgitation velocity (TRV), tricuspid annular peak systolic excursion (TAPSE), systolic PAP (sPAP), right ventricular (RV) dimension by 2D, right ventricular area at the end of diastole (RVAD), right ventricular area at the end of systolic (RVAS),RV fraction of area change (FAC), right ventricular outflow tract velocity time integral (RVOT VTI).Pulmonary vascular resistance (PVR) was calculated. All subjects ascended to 3600m within 24 hours by bus. AMS was identified by 2018 Lake Louise Questionnaire Score. Univariable and multivariable logistic regression analysis assessed independent factors associated with AMS. Results At the altitude of 3600m, 13 of 36 subjects had AMS, which defined as AMS (+) group. And the rest was AMS (-) group. There were no significant differences in HR, BP, and LV systolic and diastolic function between the two groups (P &amp;gt; 0.05). TRV, sPAP, and PVR were much higher at peak stage in AMS (+) group (P &amp;lt; 0.05). No significant differences were found in RV systolic function at rest and peak stage between the two groups. By multivariable logistic regression model, PVR and RVAD at peak stage were significantly associated with AMS occurrence (PVR-OR =1.962,95% CI: 0.689-0.973,p =0.002; RVAD-OR =1.962,95% CI: 0.638-0.967,p =0.005;). The cutoff value to predict AMS were 1.55 for PVR (AUC: 0.831) and 11.45 cm2 for RVAD (AUC: 0.802). Conclusions Supine bicycle exercise stress echocardiography is a useful and noninvasive technique to identify subjects susceptible to AMS. Subjects with higher PVR and RVAD at peak stage were associated with susceptibility to AMS.

Lung function parameters are associated with acute mountain sickness and are improved at high and extreme altitude

At altitude, factors such as decreased barometric pressure, low temperatures, and acclimatization might affect lung function.The effects of exposure and acclimatization to high-altitude on lung function were assessed in 39 subjects by repetitive spirometry up to 6022 m during a high-altitude expedition. Subjects were classified depending on the occurrence of acute mountain sickness (AMS) and summit success to evaluate whether lung function relates to successful climb and risk of developing AMS.Peak expiratory flow (PEF), forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) increased with progressive altitude (max. +20.2 %pred, +9.3 %pred, and +6.7 %pred, all p<0.05). Only PEF improved with acclimatization (BC1 vs. BC2, +7.2 %pred, p=0.044). At altitude FEV1 (p=0.008) and PEF (p<0.001) were lower in the AMS group.The risk of developing AMS was associated with lower baseline PEF (p<0.001) and longitudinal changes in PEF (p=0.008) and FEV1 (p<0.001). Lung function was not related to summit success (7126 m). Improvement in PEF after acclimatization might indicate respiratory muscle adaptation.

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.

Mitochondrial DNA Variation Correlated With the High Altitude Intolerance in Chinese Young Han Males.

ObjectiveAcute exposure to hypobaric hypoxia can trigger acute mountain sickness (AMS), while the exact mechanism has not been fully revealed. The role of genetic factors in the susceptibility of various high-altitude diseases has also gained much interest. Previous studies have provided evidence for the link between AMS and certain nuclear genes or mitochondrial haplogroup. The correlation between point mutations of mitochondrial DNA (mtDNA) and AMS was further explored in the present study.MethodsA total of 84 young Han males residing at low altitude were taken to an elevation of 4,000 m within 40 h. We collected data of their heart rate, blood pressure, peripheral oxygen saturation (SaO2), and obtained blood samples, at sea level and at high altitude. AMS was diagnosed using the revised version of the Lake Louise Questionnaire Score. Sequencing was utilized to identify the association between mtDNA alleles and the occurrence of AMS. We also assessed the association between the presence of AMS and physiological variables, and provided a preliminary discussion of the association between genotypic and phenotypic variation.ResultsThe percentage of neutrophils [Odds ratio (OR): 1.06, 95% confidence interval (CI): 1.01–1.12, P = 0.034) and SaO2 level (OR: 0.87, 95% CI: 0.79–0.95, P = 0.004) were independently associated with the development of AMS. A4576G was a risk factor for AMS (OR: 6.27, 95% CI: 1.2–32.7). T11613C (OR: 0.10, 95% CI: 0.01–0.83), A8923G (OR: 0.15, 95% CI: 0.03–0.76), and T5543C (OR: 0.19, 95% CI: 0.04–0.95) were protective factors for AMS. The level of SaO2 was significantly lower in the individual with A4576G mutation as compared with the individual without A4576G mutation (68.1 ± 7.9 vs. 75.8 ± 6.1, P = 0.001). The level of serum sodium was significantly higher in the individual with A8923G mutation as compared to the individual without A8923G mutation (144.6 ± 1.9 vs. 143.2 ± 1.9, P = 0.027).ConclusionsThe increase in neutrophils and the disability to preserve oxygen saturation may be associated with the high altitude intolerance in young Chinese Han males. A4576G is the risk factor for AMS. T11613C, A8923G, and T5543C are protective factors for AMS. The role of A8923G mutation may correlate with the sodium and water balance and the role of the A4576G mutation may be related to the disability to maintain blood oxygen level after quickly entering the plateau.

The Impact of Nocebo and Placebo Effects on Reported Incidence of Acute Mountain Sickness.

Bärtsch Peter. The impact of nocebo and placebo effects on reported incidence of acute mountain sickness. High Alt Med Biol. 23:8-17, 2022.-Well comparable studies reporting acute mountain sickness (AMS) in nonacclimatized, acutely exposed individuals performed at 3,450-3,650 m (9 studies) and 4,559-4,675 m (18 studies) at real altitude or in hypobaric or in normobaric hypoxic chambers were analyzed with the hypothesis that the study design impacts occurrence of AMS. Individual symptoms and overall scores of AMS were not different between the three modalities of exposure to a comparable degree of hypoxia, indicating that hypobaria has, if at all, minimal influence on AMS. Studies not focusing versus those focusing on AMS report lower scores and prevalence of AMS at 3,500 m, but not at 4,559 m, while frequent assessment may be associated with more severe AMS. These data suggest that focusing on AMS creates expectations of getting AMS (nocebo effects) and increases its prevalence, while not paying attention reduces negative expectations and thus AMS. On the other hand, interventions promising improvement may cause positive expectations (placebo effect). Information about purpose and dangers of a study, repeated assessments for AMS, previous experiences of AMS, and observation of illness in other study participants are major factors contributing to negative expectations and thus nocebo effects increasing AMS. They should be considered when designing studies and subject information and be reported in detail in publications of studies on AMS.

Echocardiographic Right Ventricular Outflow Track Notch Formation and the Incidence of Acute Mountain Sickness.

Yuan, Fangzhengyuan, Zhexue Qin, Chuan Liu, Shiyong Yu, Jie Yang, Jun Jin, Shizhu Bian, Xubin Gao, Jihang Zhang, Chen Zhang, Mingdong Hu, Jingbin Ke, Yuanqi Yang, Jingdu Tian, Chunyan He, Wenzhu Gu, Chun Li, Rongsheng Rao, and Lan Huang. Echocardiographic right ventricular outflow track notch formation and the incidence of acute mountain sickness. High Alt Med Biol. 22:263-273, 2021. Background: High-altitude exposure causes acute mountain sickness (AMS) and increases pulmonary arterial pressure (PAP). The notching of echocardiographic right ventricular outflow tract flow velocity envelope (right ventricular outflow tract [RVOT] notching), is related to increased PAP. We speculate that acute high-altitude exposure may trigger RVOT notching, which may be associated with AMS. Methods: All 130 subjects, ascended to 4,100 m from low altitude by bus within 7 days, underwent physiological and echocardiographic testing. The subjects with a total score of 3 or above and in the presence of a headache were diagnosed with AMS according to Lake Louise criteria. Results: After high-altitude exposure, the incidence of RVOT notching and AMS was 20% and 28.5%, respectively. The subjects with AMS had a higher incidence (37.8%) of RVOT notching than those without AMS (12.9%). Multivariate logistic regression analysis showed that RVOT notching was associated with systolic pulmonary artery pressure (SPAP) (odds ratio [OR], 1.11; 95% confidence interval [CI], 1.05-1.17; p < 0.001) and the occurrence of AMS (OR, 5.48; 95% CI, 1.96-15.35; p = 0.001). Although linear regression analysis showed a weak correlation between SPAP and Lake Louise AMS score in the overall population (r = 0.20, p = 0.020), this correlation was more pronounced in the subpopulation with RVOT notching (r = 0.44, p = 0.023) and SPAP was not related to Lake Louise AMS score in the subpopulation without RVOT notching (r = 0.03, p = 0.698). Among AMS symptoms, the incidence of headache and fatigue were higher in subjects with RVOT notching than those in subjects without RVOT notching. Conclusions: We first observe that high-altitude exposure triggers RVOT notching formation, which is associated with AMS occurrence. Clinical Trials.gov ID: ChiCTR-RCS-12002232.

Rapid Acclimatisation to High Altitude by Intermittent Hypoxia Training at Sea Level Role of Biochemical Markers

Rapid induction of soldiers to high altitude under emergency situation may lead to higher incidence of acute mountain sickness (AMS) and other high altitude illness. Intermittent Hypoxia Training (IHT) at sea level before going to high altitude is an approach for rapid acclimatisation. This approach may be helpful to reduce the occurrence of AMS and leads to better acclimatisation at high altitude in shorter duration. The present study evaluates the role of biochemical markers of acclimatisation after IHT before induction to actual high altitude. The study participants were Indian Army Personnel (n=30) and they were divided into two groups of control (n=16) and IHT exposed (n=14). The intermittent hypoxia training was administered at 12 per cent Oxygen for 4h/day for 4 days at sea level using normobaric hypoxia chamber and within 24 hrs - 48 hrs the subjects were airlifted to Leh, Ladakh, India at 11,700 ft. Preconditioning with IHT may be beneficial in maintaining antioxidant levels and ameliorate oxidative stress at high altitude. The hypoxia responsive proteins like Hemeoxygenase -1 (HO-1) and Vascular endothelial growth factor (VEGF) and the cytoprotective stress proteins, which facilitate the acclimatisation, may also get benefited by IHT exposure.

Physiological responses during ascent to high altitude and the incidence of acute mountain sickness.

Acute mountain sickness (AMS) occurs when there is failure of acclimatisation to high altitude. The aim of this study was to describe the relationship between physiological variables and the incidence of AMS during ascent to 5300 m. A total of 332 lowland‐dwelling volunteers followed an identical ascent profile on staggered treks. Self‐reported symptoms of AMS were recorded daily using the Lake Louise score (mild 3–4; moderate‐severe ≥5), alongside measurements of physiological variables (heart rate, respiratory rate (RR), peripheral oxygen saturation (SpO2) and blood pressure) before and after a standardised Xtreme Everest Step‐Test (XEST). The overall occurrence of AMS among participants was 73.5% (23.2% mild, 50.3% moderate–severe). There was no difference in gender, age, previous AMS, weight or body mass index between participants who developed AMS and those who did not. Participants who had not previously ascended >5000 m were more likely to get moderate‐to‐severe AMS. Participants who suffered moderate‐to‐severe AMS had a lower resting SpO2 at 3500 m (88.5 vs. 89.6%, p = 0.02), while participants who suffered mild or moderate‐to‐severe AMS had a lower end‐exercise SpO2 at 3500 m (82.2 vs. 83.8%, p = 0.027; 81.5 vs. 83.8%, p < 0.001 respectively). Participants who experienced mild AMS had lower end‐exercise RR at 3500 m (19.2 vs. 21.3, p = 0.017). In a multi‐variable regression model, only lower end‐exercise SpO2 (OR 0.870, p < 0.001) and no previous exposure to altitude >5000 m (OR 2.740, p‐value 0.003) predicted the development of moderate‐to‐severe AMS. The Xtreme Everest Step‐Test offers a simple, reproducible field test to help predict AMS, albeit with relatively limited predictive precision.

Sex-Dependent Association Between Early Morning Ambulatory Blood Pressure Variations and Acute Mountain Sickness.

BackgroundAcute high altitude (HA) exposure elicits blood pressure (BP) responses in most subjects, and some of them suffer from acute mountain sickness (AMS). However, a 24-h ambulatory BP (ABP) change and the correlation with the occurrence of AMS in different sexes are still unclear.ObjectivesThis prospective study aimed to investigate HA induced BP responses in males and females and the relationship between AMS and 24-h ABP.MethodsForty-six subjects were matched according to demographic parameters by propensity score matching with a ratio of 1:1. All the subjects were monitored by a 24-h ABP device; the measurement was one period of 24 h BP. 2018 Lake Louise questionnaire was used to evaluate AMS.ResultsBoth the incidence of AMS (14 [60.9%] vs. 5 [21.7%], P = 0.007) and headache (18 [78.3%] vs. 8 [34.8%], P = 0.003) were higher in females than in males. All subjects showed an elevated BP in the early morning [morning systolic BP (SBP), 114.72 ± 13.57 vs. 120.67 ± 11.10, P = 0.013]. The elevation of morning SBP variation was more significant in females than in males (11.95 ± 13.19 vs. −0.05 ± 14.49, P = 0.005), and a higher morning BP surge increase (4.69 ± 18.09 vs. −9.66 ± 16.96, P = 0.005) was observed after acute HA exposure in the female group. The increase of morning SBP was associated with AMS occurrence (R = 0.662, P < 0.001) and AMS score (R = 0.664, P = 0.001). Among the AMS symptoms, we further revealed that the incidence (R = 0.786, P < 0.001) and the severity of headache (R = 0.864, P < 0.001) are closely correlated to morning SBP.ConclusionsOur study demonstrates that females are more likely to suffer from AMS than males. AMS is closely associated with elevated BP in the early morning period, which may be correlated to higher headache incidence in subjects with higher morning SBP.

Changes in prefrontal cerebral oxygenation and microvascular blood volume in hypoxia and possible association with acute mountain sickness.

What is the central question of this study? The role of the cerebral haemodynamic response to either normobaric or hypobaric hypoxia in people susceptible to acute mountain sickness (AMS) is still under debate. Prefrontal cortex near-infrared spectroscopy-derived parameters were monitored in normobaric hypoxia at rest and during moderate-intensity exercise in AMS-prone and non-AMS individuals. What is the main finding and its importance? The AMS-prone individuals did not increase microvascular blood volume and showed lower prefrontal cerebral oxygenation in normobaric hypoxia both at rest and during exercise compared with non-AMS subjects, suggesting that these changes might underpin later development of AMS at altitude. The aim of this study was to evaluate changes in prefrontal cerebral oxygenation and microvascular blood volume during exercise in normobaric hypoxia and to investigate possible associations with the occurrence of acute mountain sickness (AMS) at altitude. Twenty-two healthy individuals (age, 26±4years; peak oxygen uptake, 42±4mlkg-1 min-1 ) were tested in two different conditions: normoxia (NORM) and normobaric hypoxia (fraction of inspired O2 =0.13; HYPO). Data were collected at rest and during submaximal constant-speed exercise. The peripheral oxyhaemoglobin saturation was measured by finger pulse oximeter. Changes in prefrontal cerebral oxygenation (ΔHbO2 ), deoxygenation (ΔHHb) and microvascular blood volume (ΔHbtot ) were obtained by near-infrared spectroscopy. Within 2weeks after laboratory testing, subjects rapidly ascended to 3647m a.s.l., and AMS was evaluated using the Lake Louise scale. Eight subjects were AMS+ , whereas 14 were AMS- . During NORM, near-infrared spectroscopy variables did not change from baseline values both at rest and during exercise, with similar results in AMS+ and AMS- subjects. During HYPO, ΔHHb increased to a similar extent in both groups, both at rest and during exercise. The ΔHbO2 was significantly less in AMS+ compared with AMS- subjects, both at rest [-3.23±5.90 versus 1.44±2.14μm, P=0.04, effect size (ES)=1.1, respectively] and during exercise (-6.56±5.51versus 0.37±4.36μm,P<0.01,ES=1.2, respectively). Total haemoglobin did not change from baseline, both at rest (-1.67±9.53μm) and during exercise (-0.96±9.12μm) in AMS+ subjects, which was significantly different from the AMS- group (5.49±3.99μm, P=0.03, ES=1.0 and 8.17±7.34μm, P=0.02, ES=1.0, respectively). Individuals prone to AMS seem to be unable to increase microvascular blood volume and to maintain oxygenation at the cerebral level during exercise in acute normobaric hypoxia, suggesting that these changes might underpin later development of AMS.

EDN1 gene potentially involved in the development of acute mountain sickness

Previous investigations have indicated that environmental and genetic factors collectively contribute to the development of acute mountain sickness (AMS), but whether the EDN1 gene is involved in AMS remains to be elucidated. A total of 356 healthy male soldiers who had not traveled to high altitudes in the previous 12 months were enrolled in our study. All participants were taken by plane from 500 m (Chengdu in Sichuan Province) to a 3700 m highland (Lhasa) within 2 hours. Clinical data were collected within 24 hours, and pulmonary function parameters were completed simultaneously. Genotypes were obtained by using iMLDR genotyping assays. A total of 237 soldiers (66.57%) presented AMS symptoms, including headache, dizziness, gastrointestinal upset and fatigue. Soldiers with AMS showed an increase in heart rate (HR), plasma tryptophan and serotonin, and a decrease in SaO2, FEV1, PEF, FVC, V75, V50, V25 and MMF (all P < 0.01). Notably, allele T in single nucleotide polymorphism (SNP) rs2070699 showed a positive correlation with the occurrence of AMS. A general linear regression analysis showed that rs2060799, Mean Arterial Pressure (MAP), SaO2, FVC, tryptophan and serotonin were independent predictors for the occurrence of AMS. Importantly, the area under the curve (AUC) values for tryptophan (0.998), serotonin (0.912) and FVC (0.86) had diagnostic specificity and sensitivity. Our results demonstrated that AMS is accompanied by changes in lung function parameters, increased plasma tryptophan and serotonin levels, and that the EDN1 polymorphism is a potential risk factor for AMS.

Effect of Intermittent Normobaric Hypoxia Exposures on Acute Mountain Sickness During Acute Ascent to 3500 m in Indian Military Personnel

&lt;p&gt;In emergencies/war like situations, rapid deployment of army personnel into high altitude occurs without proper acclimatization. Rapid deployment of unacclimatized soldiers to high mountainous environments may cause debilitating effects on operational capabilities and development of acute mountain sickness (AMS). Altitude acclimatization is the best strategy for the prevention of AMS Use of pharmacological intervention for prevention of AMS is a common practice. The use of intermittent hypoxic exposure (IHE) is an alternative approach for altitude acclimatization and it reduces occurrence and severity of AMS is. But, the use of intermittent normobaric hypoxia exposure at sea level on occurrence of AMS after acute ascent to 3500m altitude in Indian army personnel has not been tested yet.&lt;strong&gt;&lt;/strong&gt;&lt;/p&gt;

Three-Minute Step Test for Predicting Acute Mountain Sickness: A Post Hoc Analysis of Rhodiola Crenulata Extract for Prevention of Acute Mountain Sickness, a Randomized, Double-Blind, Placebo-Controlled, Crossover Trial.

Acute mountain sickness (AMS) often occurs in individuals who rapidly travel above 2,500 m. As the convenience of traveling and the development of mountain sports increase, AMS will become an increasingly important public health problem. However, no method to effectively predict AMS before it occurs is currently available. This post hoc study investigated whether the 3-Minute Step Test (3MST), which evaluates physical fitness, is predictive of AMS development. The data collected in "Rhodiola crenulata extract for prevention of AMS: a randomized, double-blind, placebo-controlled, crossover trial" was used in the analysis. This study collected 204 observations of 102 participants who made two ascents of Hehuan Mountain (3,100 m) by bus within a 3-month period. Participants completed the 3MST at 250 m (before ascent) and 3,100 m (on Hehuan Mountain). The presence of AMS was accessed using the Lake Louise scoring system. AMS was identified in 124 observations (60.78%). In the univariate analysis, the pre-departure 3MST score (at 250 m) was not significantly associated with AMS (p = 0.498), but the 3MST score measured at 3,100 m, ascent number, pulse rate at 3,100 m, and saturation of peripheral oxygen (SpO2) measured at 3,100 m were significantly correlated with the occurrence of AMS (p = 0.002, 0.039, 0.005, < 0.001, respectively). In a further multivariate analysis, only SpO2 measured at 3,100 m had a significant association with AMS (p = 0.016 and 0.006, respectively). The trend analysis showed that for every 1-point increase in the 3MST score at 3,100 m, the AMS decreased by 4% (adjusted odds ratio [AOR] = 0.96, 95% confidence interval [CI] = 0.92-1.01). The 3MST score cannot be a predictor of AMS, but it may have a potential role in predicting ascent safety in high-altitude areas.

A longitudinal study of cerebral blood flow under hypoxia at high altitude using 3D pseudo-continuous arterial spin labeling

Changes in cerebral blood flow (CBF) may occur with acute exposure to high altitude; however, the CBF of the brain parenchyma has not been studied to date. In this study, identical magnetic resonance scans using arterial spin labeling (ASL) were performed to study the haemodynamic changes at both sea level and high altitude. We found that with acute exposure to high altitude, the CBF in acute mountain sickness (AMS) subjects was higher (P < 0.05), while the CBF of non-AMS subjects was lower (P > 0.05) compared with those at sea level. Moreover, magnetic resonance angiography in both AMS and non-AMS subjects showed a significant increase in the cross-sectional areas of the internal carotid, basilar, and middle cerebral arteries on the first day at high altitude. These findings support that AMS may be related to increased CBF rather than vasodilation; these results contradict most previous studies that reported no relationship between CBF changes and the occurrence of AMS. This discrepancy may be attributed to the use of ASL for CBF measurement at both sea level and high altitude in this study, which has substantial advantages over transcranial Doppler for the assessment of CBF.

Is acute mountain sickness related to trait anxiety? A normobaric chamber study

IntroductionSome mountaineers are more prone to the occurrence of acute mountain sickness (AMS) than others. State anxiety during altitude exposure might be associated with AMS development. We hypothesized that trait anxiety might be higher in AMS cases compared to non-AMS cases. The aim of the present study was to study the relationship between AMS development and trait anxiety. MethodsIn an observational study design, AMS incidence during a 12-hour exposure to normobaric hypoxia (FiO2=12.6%, equivalent to 4500m) was determined by the Lake Louise Scoring System. Trait anxiety (State Trait Anxiety Inventory) and confounding variables were assessed in a follow-up questionnaire (37months after hypoxic exposure). ResultsTwenty nine participants returned the follow-up questionnaire. AMS incidence was 38%. Both unadjusted and adjusted logistic regression analyses did not reveal trait anxiety as a significant variable in relation to AMS. DiscussionBased on the findings of this preliminary study, there is no evidence that AMS development under normobaric conditions is related to trait anxiety. Differences to previous studies might be explained by the type of hypoxia, by different sample characteristics and by considering sleep disturbances in the calculation of the AMS score. However, future studies with larger sample sizes may help to clear the relationship between AMS development and the personality factor anxiety.

Retinal vessel regulation at high altitudes1.

To measure static and dynamic changes of retinal vessels in response to normobaric hypoxia (NH, study A) and hypobaric hypoxia (HH, study B). Study A included 10 healthy individuals exposed to a simulated altitude of 5500 meters in a NH chamber; study B included 17 individuals studied after ascent to 3000-meter altitude. Retinal vessel diameter, response to flicker light, retinal oxygen saturation and retinal venous pressure were measured at baseline, under the corresponding hypoxia condition. The effects of macitentan, an endothelin receptor antagonist, were examined in study B. The mean age of participants was 34.6±9.3 years in study A and 36.7±10.8 years in study B. Retinal arterial and venous diameter increased, arterial and venous response to flicker light decreased, while retinal oxygen saturation remained stable under both experimental conditions. Retinal venous pressure increased in six individuals after ascent to 3000 meters and normalized after macitentan treatment. The occurrence of acute mountain sickness (AMS) correlated only with the decrease of arterial constriction after ascent to 3000 meters. Retinal arterial and venous vessels react to NH and HH with a diameter increase and an impaired response to flicker light. Macitentan was capable to normalize the increased retinal venous pressure observed at high altitudes.

0120 : Left ventricular mechanics at high altitude: 6 days on the top of Europe

To get insight into the underlying mechanisms of changes in left ventricular (LV) systolic and diastolic functions during several days in high-altitude hypoxia. Resting evaluations of LV function and mechanics by 2D-strain echocardiography were performed on eleven subjects at sea level (SL PRE ), 3h±2h after helicopter transport to altitude (D0), at day 2 (D2), day 4 (D4) and day 6 (D6) at 4350 m and 5h±2h after return to sea level (SL POST ). Subjects experienced acute mountain sickness (AMS) during the first days and systolic pulmonary arterial hypertension during the six days at high altitude. LV global systolic function, LV strains and LV synchrony were unchanged at high altitude. Peak twist was increased at 4350 m (p<0.05) and was normalized at SL POST . Early filling decreased at high altitude with a nadir at D2 (SLPRE: 78±13cm.s-1; D2: 66±11cm.s-1, p<0.05) and was normalized at SL POST . LV filling pressures index was decreased at high altitude with the minimum value obtained at D2 (SL PRE : 4.7±1.2; D2: 3.4±0.6, p<0.05) and remained reduced at SL POST . Untwisting was delayed at high altitude (Percentage of untwist during isovolumic relaxation time at SL PRE vs D2: 39±31 vs 18±17%, respectively, p=0.08) and was normalized at SL POST . High-altitude exposure impaired diastolic function with the greatest effect observed at D2, concomitantly with the occurrence of AMS. The early filling impairments resulted from a decrease in LV filling pressure and a delayed LV untwisting, without changes in LV relaxation. During systole, a progressive increase in LV twist was observed from D0 to D6, probably acting as a compensatory mechanism to maintain ejection fraction and global cardiac performance during high-altitude hypoxia. The author hereby declares no conflict of interest

Impact of Study Design on Reported Incidences of Acute Mountain Sickness: A Systematic Review.

Published incidences of acute mountain sickness (AMS) vary widely. Reasons for this variation, and predictive factors of AMS, are not well understood. We aimed to identify predictive factors that are associated with the occurrence of AMS, and to test the hypothesis that study design is an independent predictive factor of AMS incidence. We did a systematic search (Medline, bibliographies) for relevant articles in English or French, up to April 28, 2013. Studies of any design reporting on AMS incidence in humans without prophylaxis were selected. Data on incidence and potential predictive factors were extracted by two reviewers and crosschecked by four reviewers. Associations between predictive factors and AMS incidence were sought through bivariate and multivariate analyses for different study designs separately. Association between AMS incidence and study design was assessed using multiple linear regression. We extracted data from 53,603 subjects from 34 randomized controlled trials, 44 cohort studies, and 33 cross-sectional studies. In randomized trials, the median of AMS incidences without prophylaxis was 60% (range, 16%-100%); mode of ascent and population were significantly associated with AMS incidence. In cohort studies, the median of AMS incidences was 51% (0%-100%); geographical location was significantly associated with AMS incidence. In cross-sectional studies, the median of AMS incidences was 32% (0%-68%); mode of ascent and maximum altitude were significantly associated with AMS incidence. In a multivariate analysis, study design (p=0.012), mode of ascent (p=0.003), maximum altitude (p<0.001), population (p=0.002), and geographical location (p<0.001) were significantly associated with AMS incidence. Age, sex, speed of ascent, duration of exposure, or history of AMS were inconsistently reported and therefore not further analyzed. Reported incidences and identifiable predictive factors of AMS depend on study design.

Diagnosis and prediction of the occurrence of acute mountain sickness measuring oxygen saturation--independent of absolute altitude?

Commercialization of trekking tourism enables untrained persons to participate in trekking tours. Because hypoxia is one of the main purported triggers for acute mountain sickness (AMS), pulse oximetry, which measures arterial oxygen saturation (SPO2), is discussed to be a possible and useful tool for the diagnosis of AMS. The purpose of this study was to evaluate possible associations between SPO2 values and the occurrence of AMS. In 204 trekkers, SPO2 values (pulse oximetry) were measured and the Lake Louise Self-assessment Score (LLS) was administered over the first 7 days of their trekking tours. During treks at altitudes of 2500-5500 m in Nepal, India, Africa, and South America, 100 participants suffered from mild AMS, 3 participants suffered from severe AMS, and 9 participants reported both mild and severe AMS. The lowest mean SPO2 was 85.5 (95 % confidence interval (CI), 83.9-86.1 %) on day 5. SPO2 and LLS exhibited a weak to moderate negative correlation for all days of the study (ρ ranging from -0.142 to -0.370). Calculation of time-shifted associations of 24 and 48 h resulted in the disappearance of most associations. Susceptibility to headaches (odds ratio (OR) 2.9-7.2) and a history of AMS (OR 2.2-3.1) were determined to be potential risk factors for the development of AMS. Since there is no strong altitude-independent association between AMS and SPO2 during the first week of high-altitude adaptation, the implementation of pulse oximetry during trekking in order to detect and predict AMS remains questionable.