Development Of Acute Mountain Sickness Research Articles

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.

A study of autonomic cardiovascular regulation in subjects with acute mountain sickness

Background: Increased sympathetic activity is a part of the integrated physiological response to a hypoxic stimulus but it is not clear if it plays a role in the genesis of acute mountain sickness (AMS). Aims and Objectives: This study was conducted to evaluate the role of the autonomic nervous system in AMS during the initial phase of acute high-altitude exposure. Materials and Methods: The study was conducted on 42 lowlanders ascended at an altitude of 3500 m by airplane. Autonomic function tests of 20 subjects who suffered from AMS were studied, and the results were compared with 22 healthy individuals. AMS was diagnosed using the Lake Louise score, and autonomic cardiovascular functions were evaluated using non-invasive cardiovascular reflex tests. Results: At high-altitude, the diastolic blood pressure (DBP) rise in response to sustained handgrip was higher in AMS subjects than the control group. The rise in DBP in cold pressor test was higher in AMS subjects than controls. The valsalva ratio was also significantly higher in AMS patients than controls. Conclusion: Sympathetic hyperactivity on induction to high altitude is positively associated with the development of AMS.

Relationship between Smoking and Acute Mountain Sickness: A Meta-Analysis of Observational Studies.

Aims Previous epidemiological investigations of the relationship between smoking and acute mountain sickness (AMS) risk yielded inconsistent findings. Therefore, a meta-analysis of observational studies was performed to determine whether smoking is related to the development of AMS. Methods Searches were performed on PubMed, Scopus, Embase, and Web of Science for relevant studies that were published before November 2016 reporting smoking prevalence and AMS. Two evaluators independently selected studies, extracted data, and assessed study quality. The pooled relative risks (RRs) and 95% confidence intervals (CIs) were obtained using random-effects models. Subgroup analyses were performed according to the type of participant, altitude, and study design. Results A total of 11 observational studies involving 7,106 participants, 2,408 of which had AMS, were eligible for inclusion in this meta-analysis. The summary RR for AMS comparing smokers to nonsmokers was 1.02 (95% CI: 0.83 to 1.26). Specific analyses for altitude, type of participant, and study design yielded similar results. There was significant heterogeneity for all studies (Q = 37.43; P < 0.001; I2 = 73%, 95% CI: 51% to 85%). No publication bias was observed (Egger's test: P = 0.548, Begg's test: P = 0.418). Conclusions The meta-analysis indicates that no difference was found in AMS risk with regard to smoking status.

Association between smoking and the risk of acute mountain sickness: a meta-analysis of observational studies.

BackgroundPeople rapidly ascending to high altitudes (>2500 m) may suffer from acute mountain sickness (AMS). The association between smoking and AMS risk remains unclear. Therefore, we performed a meta-analysis to evaluate the association between smoking and AMS risk.MethodsThe association between smoking and AMS risk was determined according to predefined criteria established by our team. Meta-analysis was conducted according to the PRISMA guidelines. We included all relevant studies listed in the PubMed and Embase databases as of September 2015 in this meta-analysis and performed systemic searches using the terms “smoking”, “acute mountain sickness” and “risk factor”. The included studies were required to provide clear explanations regarding their definitions of smoking, the final altitudes reached by their participants and the diagnostic criteria used to diagnose AMS. Odds ratios (ORs) were used to evaluate the association between smoking and AMS risk across the studies, and the Q statistic was used to test OR heterogeneity, which was considered significant when P < 0.05. We also computed 95% confidence intervals (CIs). Data extracted from the articles were analyzed with Review Manager 5.3 (Cochrane Collaboration, Oxford, UK).ResultsWe used seven case-control studies including 694 smoking patients and 1986 non-smoking controls to analyze the association between smoking and AMS risk. We observed a significant association between AMS and smoking (OR = 0.71, 95% CI 0.52–0.96, P = 0.03).ConclusionsWe determined that smoking may protect against AMS development. However, we do not advise smoking to prevent AMS. More studies are necessary to confirm the role of smoking in AMS risk.

Plasma cytokine profiling to predict susceptibility to acute mountain sickness.

Extensive studies have been performed on acute mountain sickness (AMS), but biomarkers predicting AMS are lacking. Presently, the mainstay methods to identify AMS biomarkers include proteomic and genetic methods at high altitudes or in hypoxic simulated chambers. In the present study, we compared plasma cytokine profiles between AMS-susceptible individuals and AMS-resistant individuals at low altitude by cytokine array analysis. In total, 75 differentially expressed cytokines were identified between AMS-susceptible individuals and AMS-resistant individuals, most involved in inflammation. A quantifiable human custom cytokine antibody array was then used to further test results of cytokine array analysis. Compared to AMS-resistant individuals, the level of insulin-like growth factor binding protein 6 (IGFBP-6) was significantly lower in AMS-susceptible individuals (37,318.99 ± 23,493.11 pg/mL and 25,665.38 ± 25,691.29 pg/mL, respectively; P = 0.04). Conversely, the levels of serum amyloid A1 (SAA1), dickkopf WNT signaling pathway inhibitor 4 (Dkk4), and interleukin 17 receptor A (IL-17RA) were significantly higher in AMS-susceptible individuals than in AMS-resistant individuals (SAA1: 4,069.69 ± 2,502.93 pg/mL vs. 2,994.98 ± 2,295.91 pg/mL, P = 0.05; Dkk4: 2,090.00 ± 2,094.89 pg/mL vs. 1,049.88 ± 1,690.93 pg/mL, P = 0.07; IL-17RA: 11.52 ± 8.33 pg/mL vs. 8.67 ± 6.22 pg/mL, P = 0.08). Although further in-depth research is required to examine the possible role of these cytokines in the development of AMS, these four cytokines may be of use in predicting AMS-susceptibility in a low-altitude environment.

Seven Passive 1-h Hypoxia Exposures Do Not Prevent AMS in Susceptible Individuals.

The present study evaluated the effects of a preacclimatization program comprising seven passive 1-h exposures to 4500-m normobaric hypoxia on the prevalence and severity of acute mountain sickness (AMS) during a subsequent exposure to real high altitude in persons susceptible to AMS. The project was designed as a randomized controlled trial including 32 healthy female and male participants with known susceptibility to AMS symptoms. After baseline measurements, participants were randomly assigned to the hypoxia or the control group to receive the preacclimatization program (seven passive 1-h exposures within 7 d to normobaric hypoxia or sham hypoxia). After completing preacclimatization, participants were transported (bus, cog railway) to real high altitude (3650 m, Mönchsjoch Hut, Switzerland) and stayed there for 45 h (two nights). Symptoms of AMS and physiological responses were determined repeatedly. AMS incidence and severity did not significantly differ between groups during the high-altitude exposure. In total, 59% of the hypoxia and 67% of the control group suffered from AMS at one or more time points during the high-altitude exposure. Hypoxic and hypercapnic ventilatory responses were not affected by the preacclimatization program. Resting ventilation at high altitude tended to be higher (P = 0.06) in the hypoxia group compared with the control group. No significant between-group differences were detected for heart rate variability, arterial oxygen saturation, and hematological and ventilatory parameters during the high-altitude exposure. Preacclimatization using seven passive 1-h exposures to normobaric hypoxia corresponding to 4500 m did not prevent AMS development during a subsequent high-altitude exposure in AMS-susceptible persons.

Changes in oxygen saturation can not help diagnose acute mountain sickness (AMS): ascending to Lhasa on the Qinghai-Tibet train

Acute mountain sickness (AMS) is a common condition in individuals who ascend to altitudes over 2 500 m. There is no measurements that can reliably predict or diagnose this condition. We therefore determined whether pulse oximetry data are associated with the development of AMS and can help diagnose AMS. We studied 58 young male undergraduates who traveled from Chongqing (300 m) to Lhasa (3 658 m) by train. We collected data on the ascent profiles and AMS symptoms based on the Lake Louise Score (LLS). The resting arterial oxygen saturation (R-SpO2) and pulse rate were then measured using finger pulse oximetry. In Golmud(2 800 m) and Tanggula(5 200 m), R-SpO2 was significantly lower in the AMS group than in the group without AMS (P<0.05). However, upon arrival in Lhasa (3 658 m), the R-SpO2 was higher in the AMS group than in the non-AMS group (P<0.05). In Tanggula, the change in the SpO2 (CR-SpO2) in the AMS group was higher than that in the non-AMS group (P<0.05). But in Lhasa, the CR-SpO2 in the AMS group was lower than that in the non-AMS group (P<0.05). We also monitored heart rate (HR) throughout the study. In Xining(2 200 m) and Golmud, the HRs in the AMS group were higher than those in the non-AMS group. However, the HRs in the AMS group were lower than those in the non-AMS group in Tanggula and Lhasa. Based on the results of this study, the R-SpO2 graph was not consistent. We can thus conclude that the utility of SpO2 remains limited in the diagnosis of AMS. The results suggest that using pulse oximetry to diagnose AMS is not valuable in people ascending to Lhasa on the Qinghai-Tibet train.

Lessons from altitude: cerebral perfusion insights and their potential translational clinical significance

What is the topic of this review? The long-held assumption that transcranial Doppler middle cerebral artery velocity is a surrogate for cerebral blood flow has been questioned in certain circumstances, particularly where tissue oxygenation changes. What advances does it highlight? Cerebral venous outflow restriction appears to be implicated in the development of high-altitude cerebral oedema. Rapid ascent to high altitude commonly results in acute mountain sickness and, on occasion, potentially fatal high-altitude cerebral oedema. The exact pathophysiological mechanisms behind these syndromes remain to be determined. One of the main theories to explain the development of acute mountain sickness is an increase in intracranial pressure. Vasogenic (extracellular water accumulation attributable to increased permeability of the blood-brain barrier) and cytotoxic (intracellular) oedema have also been postulated as potential mechanisms that underlie high-altitude cerebral oedema. Recently published findings derived from a very challenging field study (obtained at altitudes of up to 7950m), substantiated by sea-level hypoxic magnetic resonance angiography studies, have given new insights into the maintenance of cerebral blood flow at altitude. This report provides new perspectives and potential mechanisms to account for the maintenance of cerebral oxygen delivery at high and extreme altitude. In particular, the long-held assumption that transcranial Doppler middle cerebral artery velocity is a surrogate for cerebral blood flow has been shown to be incorrect in certain circumstances. The emerging evidence for a potential third mechanism, namely the restrictive venous outflow hypothesis, in the development of high-altitude cerebral oedema, over and above the accepted vasogenic and cytotoxic hypotheses, is also appraised.

Relation of Activity Patterns and Biochemical Factors to Acute Mountain Sickness in the South Pole

Acute Mountain Sickness (AMS) can develop during rapid altitude exposure. It is a subjective diagnosis that commonly consists of symptoms related to headaches, fatigue, sleeplessness and dizziness, while more severe AMS can deteriorate to conditions that can be life threatening. The role of physical activity in the development of AMS remains controversial. Individuals working at the South Pole are required to make a rapid transition to altitude and be moderately active. PURPOSE: To compare activity patterns and biochemical factors in individuals with and without AMS or its symptoms. METHODS: Venous blood samples were taken from 43 healthy individuals at sea level and 2 days after high altitude exposure. Physical activity was monitored using BodyMedia activity monitors. AMS symptoms were examined using modified Louise Questionnaires. Comparisons were made using paired T-test with repeated measures and Pearson’s correlation. RESULTS: 29% of subjects displayed AMS between SP days 1–2 (D1-2). Total increase in energy expenditure on day 2 for AMS individuals was 16.8%±4.1% and 10.1%±4.9% for individuals without AMS. In addition, for patients with a total symptom score greater than 5, the time spent performing moderate and vigorous activity during D1-2 was greater by a factor of 1.77±0.24 to that of the baseline, and compared to patients with a symptom score less than 5 had a lower increase of 1.34± 0.23. Blood samples presented an increase in VEGF (82.7%), increase in EPO (27.4%), decrease in Cystatin C (−5.1%), and decrease in NE (−1.68%) for AMS individuals. A correlation of total symptom score and time of moderate and vigorous activity expenditure of individuals resulted in at R squared value of 0.66. Comparisons were statistically significant with a p value of p<0.05. CONCLUSION: Increases in activity and evaluation of blood chemistry compared to the baseline after 48 hours of ascent are associated to the risk of AMS.

Risk Determinants of Acute Mountain Sickness and Summit Success on a 6-Day Ascent of Mount Kilimanjaro (5895 m)

The aims of this study were to assess incidence of acute mountain sickness (AMS) and summit success on a 6-day ascent profile of Mt. Kilimanjaro and evaluate potential risk factors for these outcomes. All trekkers through a single Australian tour company between August 2012 and July 2014 were included. Participants ascended via the Rongai route and attempted the summit on day 6. Daily assessments were made using the self-reported Lake Louise score (LLS) questionnaire. Two different AMS diagnostic criteria (LLS ≥ 3 and LLS ≥ 5) were used for data analysis. Risk factors for development of AMS and summit success were analyzed. Over the 24-month period a total of 175 participants undertook the trek. Incidence of AMS was 52.6% (LLS ≥ 3) and 22.9% (LLS ≥ 5). Summit success was 88%. Age, sex, body mass index, and acetazolamide use were not associated with risk of AMS development. Age ≥ 40 years (P = .0002) and female sex (P = .0004) were both significantly associated with reduced summit success rate. Our cohort found a lower incidence of AMS and better summit success on a 6-day ascent of Mt Kilimanjaro than previously described in other groups on 4- and 5-day ascents. Female sex and age ≥ 40 years both predicted failure to summit, but did not increase risk of developing AMS. AMS is a common cause of morbidity on Mt. Kilimanjaro, and although the risk can be mitigated by a slower ascent, there is an ongoing need for education of individual trekkers, tour companies, and local authorities.

Evidence for cerebral edema, cerebral perfusion, and intracranial pressure elevations in acute mountain sickness.

IntroductionWe hypothesized that cerebral alterations in edema, perfusion, and/or intracranial pressure (ICP) are related to the development of acute mountain sickness (AMS).MethodsTo vary AMS, we manipulated ambient oxygen, barometric pressure, and exercise duration. Thirty‐six subjects were tested before, during and after 8 h exposures in (1) normobaric normoxia (NN; 300 m elevation equivalent); (2) normobaric hypoxia (NH; 4400 m equivalent); and (3) hypobaric hypoxia (HH; 4400 m equivalent). After a passive 15 min ascent, each subject participated in either 10 or 60 min of cycling exercise at 50% of heart rate reserve. We measured tissue absorption and scattering via radio‐frequency near‐infrared spectroscopy (NIRS), optic nerve sheath diameter (ONSD) via ultrasound, and AMS symptoms before, during, and after environmental exposures.ResultsWe observed significant increases in NIRS tissue scattering of 0.35 ± 0.11 cm−1 (P = 0.001) in subjects with AMS (i.e., AMS+), consistent with mildly increased cerebral edema. We also noted a small, but significant increase in total hemoglobin concentrations with AMS+, 3.2 ± 0.8 μmolL−1 (P < 0.0005), consistent with increased cerebral perfusion. No effect of exercise duration was found, nor did we detect differences between NH and HH. ONSD assays documented a small but significant increase in ONSD (0.11 ± 0.02 mm; P < 0.0005) with AMS+, suggesting mildly elevated ICP, as well as further increased ONSD with longer exercise duration (P = 0.005).ConclusionIn AMS+, we found evidence of cerebral edema, elevated cerebral perfusion, and elevated ICP. The observed changes were small but consistent with the reversible nature of AMS.

Incidence and risk factors associated with acute mountain sickness in children trekking on Jade Mountain, Taiwan.

Acute mountain sickness (AMS) is a pathophysiological symptom complex that occurs in high-altitude areas. The incidence of AMS on Jade Mountain, the highest peak in Taiwan (3952 m), has been reported to be ∼36%. There is a lack of data in children trekking at altitude in Taiwan. The purpose of this study was to determine the incidence, risk factors and symptoms of AMS in children trekking on Jade Mountain, Taiwan. This prospective cohort study included a total of 96 healthy non-acclimatized children aged 11-12 years who trekked from an elevation of 2600-3952 m in 3 days. The Lake Louise AMS score was used to record symptoms associated with AMS. AMS were reported in 59% of children trekking on Jade Mountain over a 3 day period. AMS incidence increased significantly with increasing altitude. The most common AMS symptom was headache, followed by fatigue or weakness, difficulty sleeping, dizziness or lightheadedness and gastrointestinal symptoms. Children who had experienced upper respiratory infection (URI) within the 7 days before their trek tended to have a greater risk for development of AMS. AMS incidence did not significantly differ according to gender, recent acute gastroenteritis, menstruation and body mass index. The incidence of AMS in children trekking on Jade Mountain is greater than that observed in adults, and was associated with altitude and recent URI.

Preparing patients for travel to high altitude: advice on travel health and chemoprophylaxis.

Travel to altitudes above 2500 m is a popular recreational activity that presents a potential risk of high-altitude illness. Acute mountain sickness (AMS), for example, affects up to three-quarters of trekkers attempting to climb Mount Kilimanjaro in Tanzania, East Africa (5895 m). GPs should be able to provide practical advice on prevention of high-altitude illness.1 Travellers, especially those travelling in organised groups, may not allow adequate time for acclimatisation owing to pressurised itineraries, and administering chemoprophylaxis to accelerate this physiological response to hypobaric hypoxia may be indicated in some cases. This article summarises current recommendations in relation to high-altitude illness, its prevention, and the specific precautions that should be followed by patients with pre-existing chronic illnesses. ### Classification and diagnosis The single most important risk factor for the development of high-altitude illness is rate of ascent. There is significant heterogeneity with respect to the rate at which individuals can ascend without developing altitude illness. There is no reliable means to predict at sea level which travellers are more likely to be affected, and measuring capillary oxygen saturation with a pulse oximeter during ascent does not predict the development of AMS.2 All travellers to high-altitude environments should be able to recognise the symptoms of high-altitude illness. According to the Lake Louise consensus definition,3 AMS is characterised by the presence of a non-specific headache and at least one of the following symptoms: lack of appetite, nausea, vomiting, fatigue, disturbed sleep, or …

Principal Component Analysis and Risk Factors for Acute Mountain Sickness upon Acute Exposure at 3700 m.

ObjectiveWe aimed to describe the heterogeneity in the clinical presentation of acute mountain sickness (AMS) and to identify its primary risk factors.MethodsThe participants (n = 163) received case report form questionnaires, and their heart rate (HR), oxygen saturation (SpO2), echocardiographic and transcranial Doppler variables, ability to perform mental and physical work, mood and psychological factors were assessed within 18 to 22 hours after arriving at 3700 m from sea level (500 m) by plane. First, we examined the differences in all variables between the AMS-positive and the AMS-negative groups. Second, an adjusted regression analysis was performed after correlation and principal component analyses.ResultsThe AMS patients had a higher diastolic vertebral artery velocity (Vd; p = 0.018), a higher HR (p = 0.006) and a lower SpO2. The AMS subjects also experienced poorer sleep quality, as quantified using the Athens Insomnia Scale (AIS). Moreover, the AMS population exhibited more negative mood states, including anxiety, depression, hostility, fatigue and confusion. Five principal components focused on diverse aspects were also found to be significant. Additionally, more advanced age (p = 0.007), a higher HR (p = 0.034), a higher Vd (p = 0.014), a higher AIS score (p = 0.030), a decreased pursuit aiming capacity (p = 0.035) and decreased vigor (p = 0.015) were risk factors for AMS.ConclusionsMood states play critical roles in the development of AMS. Furthermore, an elevated HR and Vd, advanced age, elevated AIS sores, insufficient vigor and decreased mental work capacity are independent risk factors for AMS.

Identifying risk factors that contribute to acute mountain sickness

Background. Acute mountain sickness (AMS) is an ever-increasing burden on the health sector. With reported incidences of greater than 50%, coupled with the fact that recreational activities at high altitude are gaining increasing popularity, more persons are developing AMS. Physicians are therefore increasingly faced with the task of managing and preventing AMS.Objectives. The pathophysiology of AMS is poorly understood, with little understanding of risk factors for the development of AMS. This research aimed to identify epidemiological and physiological risk factors for development of AMS.Methods. This study is a questionnaire-based study conducted in London and at Everest Base Camp, in which 116 lowlanders were invited to participate and fill in a questionnaire to identify potential risk factors in their history that may have contributed to development of or protection against AMS.Results. A total of 89 lowlanders enrolled in the study. Thirty-seven of the participants had AMS at Everest Base Camp, giving a prevalence of 42%. Of the demographic variables, only weight and body mass index (BMI) were statistically significantly associated with AMS, with those who weighed less or had a lower BMI more likely to get AMS. Previous high-altitude experience was also associated with AMS, with those who had such experience less likely to get AMS.Conclusion. Predicting AMS and furthering our understanding of the pathophysiology of AMS will be of tremendous benefit. Further research is needed in this regard.

Genetic variants of endothelial PAS domain protein 1 are associated with susceptibility to acute mountain sickness in individuals unaccustomed to high altitude: A nested case-control study.

The endothelial PAS domain protein 1 (EPAS1) gene functions to sense the blood oxygen level by regulating the hypoxia-inducible transcription factor pathway, and single nucleotide polymorphisms (SNPs) of EPAS1 have been found to have a strong and positive selection in the adaptation of the native Tibetan highland population to high-altitude hypoxia. The aim of the present study was to investigate the effect of EPAS1 SNPs on the risk of acute mountain sickness (AMS) and the physiological responses to acute high-altitude hypoxia in lowland humans. Three tag SNPs (rs6756667, rs13419896 and rs4953354; minor allele frequency, ≥5%) were selected and genotyped in 603 unrelated Han Chinese men, who had traveled to Lhasa (a high-altitude hypoxia environment) by plane, using a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry method. The data showed that the EPAS1 rs6756667 wild-type GG homozygous genotype was associated with elevated AMS risk compared with the AA and AG genotypes (odds ratio, 1.815; 95% confidence interval, 1.233-2.666; P=0.0023) using the dominant-model analysis. EPAS1 rs6756667 GG genotypes were also associated with higher levels of hemoglobin, red blood cells and hematocrit than those carrying the AG heterozygote during AMS development. These findings indicate that EPAS1 SNPs play a role in the physiological effects of AMS, and these effects could be further evaluated as a therapeutic strategy to control acute hypoxia-related human diseases.

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.

The impact of physical fitness and body mass index in children on the development of acute mountain sickness: A prospective observational study.

BackgroundAcute mountain sickness (AMS) is commonly found among people traveling above 2500 m. We investigated whether the occurrence of AMS is related to differences in individual physical fitness and BMI in subjects 11–13 years of age.MethodsThis study was conducted at Xue Mountain, Taiwan (elevation of 3886 m) between June 13, 2011 and June 17, 2011. Subjects were asked to ascend from Taipei City (25 m) to the summit (3886 m) over 3 days and 2 nights. Gender, age, weight, height, and fitness index (determined using a 3-minute step test) were recorded at sea level before ascent. The Lake Louise AMS score was used to record symptoms and diagnose AMS.ResultsA total of 179 subjects (mean age: 11.8 years; 102 males, 77 females) were included in the analysis. A total of 44.7% of subjects were diagnosed with AMS. Male gender (p = 0.004) and elevated body mass index (BMI) (p < 0.001) were each associated with the development of AMS. However the physical fitness index was comparable in subjects with and without AMS (67.8 ± 10.1 vs. 68.0 ± 9.3, p = 0.9).ConclusionsThis study shows that both BMI and male gender were associated with the development of AMS in 11–13 year old children. Physical fitness was not associated with the occurrence of AMS.Electronic supplementary materialThe online version of this article (doi:10.1186/s12887-015-0373-0) contains supplementary material, which is available to authorized users.

Rate of ascent and acute mountain sickness at high altitude.

To examine the effect of ascent rate on the induction of acute mountain sickness (AMS) in young adults during a climb to Jiaming Lake (3350 m) in Taiwan. Prospective, nonrandomized. Climb from 2370 to 3350 m. Young adults (aged 18 to 26 years) (N = 91) chose to participate in either the fast ascent (3 days; n = 43) or slow ascent (4 days; n = 48) group (1 and 2). Two criteria were used to define AMS. A Lake Louise score ≥3 and Lake Louise criteria [in the setting of a recent gain in altitude, the presence of headache and at least 1 of gastrointestinal discomfort (anorexia, nausea, or vomiting), fatigue or weakness, dizziness or lightheadedness, or difficulty sleeping]. Heart rate, blood oxygen saturation (SaO2), and symptoms of AMS were monitored each morning and evening. Baseline characteristics were similar between groups, except for significant differences in history of alcohol consumption (P = 0.009) and climbing experience above 3000 m (P < 0.001). The incidence of AMS was not associated with the rate of ascent. Acute mountain sickness was most prevalent in group 1 on day 2 in the evening and in group 2 on day 3 in the evening. In both groups, AMS correlated with the initial reduction in SaO2. Body mass index (BMI) >24 kg/m was identified as a significant risk factor for AMS. The development of AMS was closely associated with an initial reduction in SaO2. A BMI >24 kg/m also contributed to the occurrence of AMS. These findings indicate that factors other than ascent rate should be considered when trying to ameliorate the risk of AMS.

Statin use and the development of acute mountain sickness.

Our prior publication suggested that elevated serum concentrations of low-density lipoprotein (LDL) was protective against the development of acute mountain sickness (AMS) while an inflammatory response was contributory to its development. The use of 3-hydroxy-3-methylglutaryl-coenzyme-A-reductase inhibitors ("statins") may be of interest to those traveling to altitude-these medications will lower serum LDL concentrations, but are also reported to have anti-inflammatory properties. Prior to flying from sea level to the South Pole (∼10,498.7 ft or 3200 m) during the austral summer months of 2005-2006 and 2006-2007, the 248 subjects provided informed consent. Questionnaires related to AMS symptoms, acetazolamide use, personal history, and anthropometrics were paired with results from blood samples. Statin use was reported by six subjects who were matched for age, sex, altitude of residence, and acetazolamide use with seven subjects not using a statin. No significant differences were identified in any of the matched variables between the groups. No statin users reported symptoms of AMS while 57% of participants not using a statin did report AMS symptoms (P = 0.03). No significant difference was noted between LDL levels in the statin group (108.3 ± 61.0) as compared to the group not taking statins (104.6 ± 22.1) (P = 0.88). Our previous results suggested that elevated LDL was protective while an inflammatory response was contributory with respect to AMS development. The present results suggest that statin use may provide protection against AMS symptoms, possibly through an anti-inflammatory property, despite its lipid-lowering capacity. Harrison MF, Johnson BD. Statin use and the development of acute mountain sickness.