Predicting Acute Mountain Sickness Using Regional Sea-Level Cerebral Blood Flow

Objective To investigate the role of sea-level cerebral blood flow(CBF)in predicting acute mountain sickness(AMS)using three-dimensional pseudo-continuous arterial spin labeling(3D-pCASL).Methods Forty-eight healthy volunteers reached an altitude of 3,650 m by air after undergoing a head magnetic resonance imaging(MRI)including 3D-pCASL at sea level.The CBF values of the bilateral anterior cerebral artery(ACA),middle cerebral artery(MCA),posterior cerebral artery(PCA),and posterior inferior cerebellar artery(PICA)territories and the laterality index(LI)of CBF were compared between the AMS and non-AMS groups.Statistical analyses were performed to determine the relationship between CBF and AMS,and the predictive performance was assessed using receiver operating characteristic(ROC)curves.Results The mean cortical CBF in women(81.65±2.69 mL/100 g/min)was higher than that in men(74.35±2.12 mL/100 g/min)(P<0.05).In men,the cortical CBF values in the bilateral ACA,PCA,PICA,and right MCA were higher in patients with AMS than in those without.Cortical CBF in the right PCA best predicted AMS(AUC=0.818).In women,the LI of CBF in the ACA was different between the AMS and non-AMS groups and predicted AMS with an AUC of 0.753.Conclusion Although the mechanism and prediction of AMS are quite complicated,higher cortical CBF at sea level,especially the CBF of the posterior circulatory system,may be used for prediction in male volunteers using non-invasive 3D-pCASL.

Traditional Chinese medicine for acute mountain sickness prevention: A systematic review and meta-analysis of randomized controlled trials

Objective: To evaluate the efficacy of traditional Chinese medicine(TCM) for preventing acute mountain sickness(AMS).Methods: We included randomized controlled trials(RCTs) which evalueded the effect of TCM for preventing AMS, compared with a placebo, no treatment or acetazolamide. The literature was searched in 6major databases. RevMan 5.4 software was used for the meta-analysis. The relative risk for discrete variables and the mean difference for continuous variables with 95% confidence intervals(CIs) were applied to express the effect size. The risk of bias in the included studies was evaluated using the Cochrane risk assessment tool 2.0(RoB 2.0), and the evidence certainty was assessed using the Grading of Recommendations Assessment and the Development and Evaluation(GRADE) approach.Results: Twenty RCTs involving 3015 participants and 16 TCM patent drugs were included. The overall risk of bias in the majority of studies(15/20) was of some concerns. In terms of the AMS incidence,Rhodiola rosea(R. rosea, Hong Jing Tian) and Ginkgo biloba(G. biloba, Yin Xing Ye) were equivalent to the placebo/no treatment [RR(95% CI): 0.66(0.43-1.01), 0.82(0.63-1.06), respectively]. The AMS incidence in the G. biloba group was higher than that in the acetazolamide group [RR(95% CI): 2.92(1.69-5.06)]. In terms of improving the AMS symptom score on days 1 and 3 in the plateau, R. rosea and G. biloba were superior to the placebo or no treatment [MD(95% CI):-0.98(-1.71,-0.25),-2.05(-3.14,-0.95), respectively]. The other 14 Chinese patent medicines were evaluated in a single trial, and the majority of the results were negative. The subgroup analysis showed that the effect of R. rosea was related to the intervention time, way of ascending, and altitude.Conclusion: R. rosea and G. biloba were effective in improving AMS symptoms but had no effect in reducing the AMS incidence. There was insufficient evidence to support the use of other TCM patent drugs to prevent AMS. More randomized double-blind placebo-controlled trials are warranted to evaluate and screen effective Chinese patent medicines for AMS prevention.

A specific objective supplemental factor in evaluating acute mountain sickness: ΔHR in combination with SaO_2

Background: So far, there have been no measurements confirmed useful in diagnosing acute mountain sickness(AMS). The aim of this study was to determine the role of heart rate(HR) difference(ΔHR) and oxygen saturation(Sa O2) as objective risk factors in aiding the diagnosis of AMS.Methods: A total of 1,019 participants were assigned to either the acute exposure group(AEG): from 500 m to 3,700 m by flight within 2.5 hours(n=752); or the pre-acclimatization group(PAG): ascended to 4,400 m from 3,650 m within three hours by car after adapting 33 days at 3,650m(n=267). The questionnaires or measurements of resting Sa O2 and HR were completed between 18 and 24 hours before departure and after arrival.Results: Incidence of AMS was 61.3%(461) in AEG, with 46.1%(347) mild cases and 15.2%(114) severe cases. In PAG, the incidence was 38.9%(104), with 30.7%(82) mild cases and 8.2%(22) severe cases. The AMS subjects showed a significant increase in HR and a decrease in Sa O2 levels compared with the non-AMS subjects in both groups. ΔHR and post-exposure Sa O2 were significantly correlated with the Lake Louise Score(LLS) in both groups. Stepwise logistic regression analysis revealed the ΔHR >25 and Sa O2 <88% in AEG as well as ΔHR >15 and Sa O2 <86% in PAG to be independent risk factors of AMS. Combining these two measurements could specifically indicate participants with AMS, which showed a positive predictive value of 89% and specificity of 97% in AEG as well as 85% and 98% in PAG.Conclusion:ΔHR or Sa O2, as objective measurements, correlate with AMS. Combination of these two measurements may be useful as an additional specific and objective factor to further confirm the diagnosis of AMS.

Relationship between autonomic nervous system function and acute mountain sickness

Objective: To elucidate the role of the autonomic nervous system (ANS) in acute mountain sickness (AMS) during the initial phase at acute high-altitude exposure. Methods: Ninety-nine healthy sea-level residents rapidly ascended to Tibet plateau (3 675 m altitude) by airplane from Chengdu plain (560 m altitude). ANS function was tested in plain and day 2–4 in Tibet by heart rate variability (HRV), cold pressor test (CPT). AMS was evaluated by clinic symptomatic scores. All subjects were divided into non-AMS group (57, scores≤4) and AMS group (42, scores>4). Results: Compared with non-AMS group, AMS group had higher standard deviation of normal to normal intervals (SDNN), root mean square of delta RR (rMSSD), low-frequency (LF) power, and normalized low-frequency (LFnu) power in plain (P<0.05). After arrival at 3 675 m altitude, AMS group had greater reduction in percentage of delta RR>50 ms(PNN50), rMSSD (P<0.01) and SDNN, LF, total power (TP) (P<0.05). Although no significant differences in the increase of SP and DP during CPT were found between 2 groups in plain, the SP increase during CPT of AMS group was less than non-AMS group (P<0.05) at 3 675 m altitude. AMS symptomatic scores was not only positively correlated with SDNN, rMSSD, LF/HF in plain (P<0.05), but also negatively correlated with HFnu in plain (P<0.05). Conclusion: During the initial high altitude exposure, ANS modulation is generally blunted, but the relatively predominant sympathetic control is enhanced, and this characteristic change of ANS function is positively correlated with the development of AMS.

Relationship between excessive erythrocytosis and acute mountain sickness: A field study

Background: Alterations in hematology, especially erythroid changes, may be involved in acute mountain sickness(AMS) at high altitude. This study aimed to identify the relationship between excessive erythrocytosis and AMS following different durations of high-altitude exposure.Methods: A total of 692 healthy young Chinese men were recruited for the study in June and July of 2012 and were divided into the following five groups: I) the 24-h group(24 hours after arrival at Lhasa, 3,700 m, n=261); II) the 7-d group(exposed at Lhasa, 3,700 m for seven days, n=99); III) the re-exposure group(re-exposed at Yang Bajing, 4,400 m for seven days after 】1 year of acclimation at 3,700 m, n=94); IV) the acclimated group(】1 year of acclimation at 3,700 m, Lhasa, n=42); and V) the sea-level control(control group, Chengdu, n=196). Case report forms were used to record the subjects’ demographic information and AMS-related symptoms. All of the subjects underwent routine blood tests.Results: The red blood cell(RBC) count fell slightly but was not significant upon acute exposure to high altitude, whereas the hemoglobin concentration([Hb]) increased significantly. After high-altitude re-exposure, both of the [Hb] and RBC count showed significant increases. The incidence of AMS was 65.1%, 26.3% and 51.1%, respectively in the 24-h, 7-d and re-exposure groups. The [Hb](P=0.024) and hematocrit(P=0.017) were greater in the AMS+ individuals than in the AMS– individuals in 7-d group. A correlation analysis revealed that the [Hb] and hematocrit were closely related with AMS score in 7-d and re-exposure groups, while the RBC showed a correlation with AMS score only in the re-exposure group. The AMS incidence was lowest when the [Hb] was between 140 and 160 g/L in the 24-h and 7-d groups.Conclusions: AMS is associated with both [Hb] and excessive erythrocytosis. Additionally, our findings indicate the existence of an optimal [Hb] for preventing AMS.

Association between physiological responses after exercise at low altitude and acute mountain sickness upon ascent is sex-dependent

Background:Acute mountain sickness(AMS)is the mildest form of acute altitude illnesses,and consists of nonspecific symptoms when unacclimatized persons ascend to elevation of≥2500 m.Risk factors of AMS include:the altitude,individual susceptibility,ascending rate and degree of pre-acclimatization.In the current study,we examined whether physiological response at low altitude could predict the development of AMS.Methods:A total of 111 healthy adult healthy volunteers participated in this trial;and 99(67 men and 32 women)completed the entire study protocol.Subjects were asked to complete a 9-min exercise program using a mechanically braked bicycle ergometer at low altitude(500 m).Heart rate,blood pressure(BP)and pulse oxygen saturation(SpO2)were recorded prior to and during the last minute of exercise.The ascent from 500 m to 4100 m was completed in 2 days.AMS was defined as≥3 points in a 4-item Lake Louise Score,with at least one point from headache wat 6–8 h after the ascent.Results:Among the 99 assessable subjects,47(23 men and 24 women)developed AMS at 4100 m.In comparison to the subjects without AMS,those who developed AMS had lower proportion of men(48.9%vs.84.6%,P<0.001),height(168.4±5.9 cm vs.171.3±6.1 cm,P=0.019),weight(62.0±10.0 kg vs.66.7±8.6 kg,P=0.014)and proportion of smokers(23.4%vs.51.9%,P=0.004).Multivariate regression analysis revealed the following independent risks for AMS:female sex(odds ratio(OR)=6.32,P<0.001),SpO2 change upon exercise at low altitude(OR=0.63,P=0.002)and systolic BP change after the ascent(OR=0.96,P=0.029).Women had larger reduction in SpO2 after the ascent,higher AMS percentage and absolute AMS score.Larger reduction of SpO2 after exercise was associated with both AMS incidence(P=0.001)and AMS score(P<0.001)in men but not in women.Conclusions:Larger SpO2 reduction after exercise at low altitude was an independent risk for AMS upon ascent.Such an association was more robust in men than in women.Trial registration:Chinese Clinical Trial Registration,ChiCTR1900025728.Registered 6 September 2019.

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

Background: People rapidly ascending to high altitudes(>2500m) 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.Methods: The 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 Pub Med 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).Results: We 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).Conclusion: We 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.

EPAS1 and VEGFA gene variants are related to the symptoms of acute mountain sickness in Chinese Han population: a cross-sectional study

Background: More people ascend to high altitude(HA) for various activities, and some individuals are susceptible to HA illness after rapidly ascending from plains. Acute mountain sickness(AMS) is a general complaint that affects activities of daily living at HA. Although genomic association analyses suggest that single nucleotide polymorphisms(SNPs) are involved in the genesis of AMS, no major gene variants associated with AMS-related symptoms have been identified.Methods: In this cross-sectional study, 604 young, healthy Chinese Han men were recruited in June and July of 2012 in Chengdu, and rapidly taken to above 3700 m by plane. Basic demographic parameters were collected at sea level, and heart rate, pulse oxygen saturation(Sp O2), systolic and diastolic blood pressure and AMS-related symptoms were determined within 18–24 h after arriving in Lhasa. AMS patients were identified according to the latest Lake Louise scoring system(LLSS). Potential associations between variant genotypes and AMS/AMS-related symptoms were identified by logistic regression after adjusting for potential confounders(age, body mass index and smoking status).Results: In total, 320 subjects(53.0%) were diagnosed with AMS, with no cases of high-altitude pulmonary edema or high-altitude cerebral edema. Sp O2 was significantly lower in the AMS group than that in the non-AMS group(P=0.003). Four SNPs in hypoxia-inducible factor-related genes were found to be associated with AMS before multiple hypothesis testing correction. The rs6756667(EPAS1) was associated with mild gastrointestinal symptoms(P=0.013), while rs3025039(VEGFA) was related to mild headache(P=0.0007). The combination of rs6756667 GG and rs3025039 CT/TT further increased the risk of developing AMS(OR=2.70, P<0.001).Conclusions: Under the latest LLSS, we find that EPAS1 and VEGFA gene variants are related to AMS susceptibility through different AMS-related symptoms in the Chinese Han population;this tool might be useful for screening susceptible populations and predicting clinical symptoms leading to AMS before an individual reaches HA.Trial registration: Chinese Clinical Trial Registration, Chi CTR-RCS-12002232. Registered 31 May 2012.

Sex-based differences in the prevalence of acute mountain sickness: a meta-analysis

Background:When lowlanders rapidly ascend to altitudes>2500 m,they may develop acute mountain sickness(AMS).The individual susceptibility,ascending velocity,time spent at altitude,activity levels and altitude reached are considered risk factors for AMS.However,it is not clear whether sex is a risk factor.The results have been inconclusive.We conducted a meta-analysis to test whether there were sex-based differences in the prevalence of AMS using Lake Louise Scoring System.Methods:Systematic searches were performed in August 2019 in EMBASE,PubMed,and Web of Science for prospective studies with AMS data for men and women.The titles and abstracts were independently checked in the primary screening step,and the selected full-text articles were independently assessed in the secondary screening step by the two authors(YPH and JLW)based on pre-defined inclusion criteria.The meta-analysis was performed using by the STATA 14.1 software program.A random-effects model was employed.Results:Eighteen eligible prospective studies were included.A total of 7669 participants(2639[34.4%]women)were tested.The results showed that there was a statistically significant higher prevalence rate of AMS in women than in men(RR=1.24,95%CI 1.09–1.41),regardless of age or race.However,the heterogeneity was significant in the analysis(Tau2=0.0403,Chi2=50.15,df=17;I2=66.1%,P=0.000),it was main caused by different numbers of subjects among the studies(coefficient=–2.17,P=0.049).Besides,the results showed that there was no evidence of significant publication bias in the combined studies on the basis of Egger’s test(bias coefficient=1.48,P=0.052)and Begg’s test(P=0.130).Conclusions:According to this study,the statistically significant finding emerging from this study was that women have a higher prevalence of AMS.However,the authors could not exclude studies where patients were on acetazolamide.Our analysis provided a direction for future studies of the relationship of sex and the risk of AMS,such as the pathological mechanism and prevention research.

Ataxia,acute mountain sickness,and high altitude cerebral edema

Previous investigations suggest that ataxia is common and often one of the most reliable warning signs of high altitude cerebral edema(HACE). The aim of this study was to investigate the diagnostic role of ataxia in acute mountain sickness(AMS)and HACE among mountain rescuers on the quake areas,and in approaching the relation between AMS and HACE. After the earthquake on April 14,2010,approximately 24 080 lowland rescuers were rapidly transported from sea level or lowlands to the mountainous rescue sites at 3 750 ~ 4 568 m,and extremely hardly worked for an emergency treatment after arrival. Assessments of acute altitude illness on the quake areas were using the Lake Louise Scoring System. 73 % of the rescuers were found to be developed AMS. The incidence of high altitude pulmonary edema(HAPE)and HACE was 0.73 % and 0.26 %,respectively,on the second to third day at altitude. Ataxia sign was measured by simple tests of coordination including a modified Romberg test. The clinical features of 62 patients with HACE were analyzed. It was found that the most frequent,serious neurological symptoms and signs were altered mental status(50/62,80.6 %)and truncal ataxia(47/62,75.8 %). Mental status change was rated slightly higher than ataxia,but ataxia occurred earlier than mental status change and other symptoms. The earliest sign of ataxia was a vague unsteadiness of gait,which may be present alone in association with or without AMS. Advanced ataxia was correlated with the AMS scores,but mild ataxia did not correlate with AMS scores at altitudes of 3 750~4 568 m. Of them,14 patients were further examined by computerized tomographic scanning of the brain and cerebral magnetic resonance imagines were examined in another 15 cases. These imaging studies indicated that the presence of the cerebral edema was in 97 % of cases who were clinically diagnosed as HACE(28/29). Ataxia seems to be a reliable sign of advanced AMS or HACE,so does altered mental status.

Rong Shuan Jiao Nang in the treatment of acute mountain sickness and high altitude myocardial ischemic syndrome in Yushu

To evaluate the therapeutic effects of Rong Shuan Jiao Nang （RSJN） on treatment of acute mountain sickness （AMS） and high altitude myocardial ischemic syndrome in workers in Yushu, three groups were studied： group A （60 patients with AMS, given RSJN）, group B （15 patients with altitude myocardial ischemic syndrome, given RSJN）, and group C （control, without drugs）. All studied subjects were lowland workers who were first time entry to Yushu for work at an altitude of 4 250 m. During the course of treatment, a routing physical examina- tion was performed, AMS Lake Louise Scores were estimated, arterial oxygen saturation （SaO2）, electrocardiography and hemoglobin concentration were measured before and after using RSJN for 10 days. In group A, the effective rate was 68 %, symptomatic improvement in 54 cases （90 %） within 5 days. In group B, the effective rate was 93 %, episodes of angina pectoris stopped in 12 patients within 3 - 7 days, one lasted 8 days. After treatment, the level of SaO2 increased 15.5 %, 21.8 % and 5.6 % in group A, group B and group C, respectively. RSJN tak- en at the start of the arrival at Yushu can decrease AMS scores and facilitate cure. If taken after the illness has begun, RSJN may help lessen symptoms, especially effectively improved angina pectoris of the high altitude myocardial ischemic syndrome. Symptoms usually subside after 3 - 8 days. RSJN should be continually used lbr at least 7 days after ascent.

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 AMSpositive group had the largest increases in RPC flow density in the nasal sector(AMS-positive,?3.21±2.37;AMS-negative,?0.01±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.

Who are more at risk for acute mountain sickness： a prospective study in Qinghai-Tibet railroad construction workers on Mt. Tanggula

Background It is important to determine the incidence of acute mountain sickness （AMS） among workers at altitudes between 3500 m and 5000 m on Mt. Tanggula during the construction of the Qinghai-Tibet railroad. This study explored the risk factors predisposing workers to developing AMS and attempted to develop more effective ways of preventing and treating AMS. Methods A total of 11 182 workers were surveyed by completing twice daily a Lake Louise questionnaire, and a score 〉3 indicated AMS. The contributing risk factors were assessed for at least 2 months for the duration of the study in the years from 2001 to 2003. A risk model was developed by multiple Logistic regression. Standard statistica~ methods were used to analyze data. Results AMS occurred in 56% of workers working at high altitudes on Mt. Tanggula. The incidence of AMS increased with increasing altitude. Rapid ascent to an altitude above 3500 m, sea-level or lowland newcomers, young people under 25 years of age, heavy physical exertion, obese person, and arterial oxygen saturation （SaO2） below 80% were independent AMS risk factors. No significant association was found between AMS and sex or taking Rhodiola. Medical education contributed to an early diagnosis of AMS. Conclusions This study used the Lake Louise scoring system suggesting that it is a well-validated standard for field evaluation of AMS and for making an early diagnosis. These studies have described many variables regarding risk factors for the development of AMS. Risk factors which can be modified should be attended to, and the physicians should carry out check-ups and tests to identify subjects who are more at risk. Prevention consists in continuous gradual ascent, medical education, and prompt descent to avoid progression in patients with serious AMS. It is most important to effectively control the risk factors of AMS.

Intermittent Oxygen Inhalation with Proper Frequency Improves Overall Health Conditions and Alleviates Symptoms in a Population at High Risk of Chronic Mountain Sickness with Severe Symptoms

Background： Oxygen inhalation therapy is essential for the treatment of patients with chronic mountain sickness （CMS）, but the efficacy of oxygen inhalation for populations at high risk of CMS remains unknown. This research investigated whether oxygen inhalation therapy benefits populations at high risk of CMS. Methods： A total of 296 local residents living at an altitude of 3658 m were included; of which these were 25 diagnosed cases of CMS, 8 cases dropped out of the study, and 263 cases were included in the analysis. The subjects were divided into high-risk （180 ≤ hemoglobin （Hb） 〈210 g/L, n = 161） and low-risk （Hb 〈180 g/L, n = 102） groups, and the cases in each group were divided into severe symptom （CMS score ≥6） and mild symptom （CMS score 0-5） subgroups. Severe symptomatic population of either high- or low-risk CMS was randomly assigned to no oxygen intake group （A group） or oxygen intake 7 times/week group （D group）; mild symptomatic population of either high- or low-risk CMS was randomly assigned to no oxygen intake group （A group）, oxygen intake 2 times/week group （B group）, and 4 times/week group （C group）. The courses for oxygen intake were all 30 days. The CMS symptoms, sleep quality, physiological biomarkers, biochemical markers, etc., were recorded on the day before oxygen intake, on the 15th and 30th days of oxygen intake, and on the 15th day after terminating oxygen intake therapy. Results： A total of 263 residents were finally included in the analysis. Among these high-altitude residents, CMS symptom scores decreased for oxygen inhalation methods B, C, and D at 15 and 30 days after oxygen intake and 15 days after termination, including dyspnea, palpitation, and headache index, compared to those before oxygen intake （B group： Z = 5.604, 5.092, 5.741; C group： Z = 4.155, 4.068, 4.809; D group： Z = 6.021, 6.196, 5.331, at the 3 time points respectively; all P 〈 0.05/3 vs. before intake）. However, dyspnea/palpitation （A group： Z = 5.003, 5.428, 5.493, both P 〈 0.05/3 vs. before intake） and headache （A group： Z = 4.263, 3.890, 4.040, both P 〈 0.05/3 vs. before intake） index decreased significantly also for oxygen inhalation method A at all the 3 time points. Cyanosis index decreased significantly 30 days after oxygen intake only in the group of participants administered the D method （Z= 2.701, P = 0.007）. Tinnitus index decreased significantly in group A and D at 15 days （A group： Z = 3.377, P = 0.001, D group： Z = 3.150, P - 0.002）, 30 days after oxygen intake （A group： Z = 2.836, P = 0.005, D group： Z = 5.963, P 〈 0.0001） and 15 days after termination （A group： Z- 2.734, P = 0.006, D group： Z - 4.049, P = 0.0001）, and decreased significantly in the group B and C at 15 days after termination （B group： Z = 2.611, P = 0.009; C group： Z = 3.302, P = 0.001）. In the population at high risk of CMS with severe symptoms, oxygen intake 7 times/weeksignificantly improved total symptom scores of severe symptoms at 15 days （4 [2, 5] vs. 5.5 [4, 7], Z = 2.890, P = 0.005） and 30 days （3 [1, 5] vs. 5.5 [2, 7], Z= 3.270, P = 0.001） after oxygen intake compared to no oxygen intake. In the population at high risk of CMS with mild symptoms, compared to no oxygen intake, oxygen intake 2 or 4 times/week did not improve the total symptom scores at 15 days （2 [1, 3], 3 [1, 4] vs. 3 [1.5, 5]; 2＂2 = 2.490, P= 0.288）, and at 30 days （2 [0, 4], 2 [1, 4.5] vs. 3 [2, 5];2＂2- 3.730, P = 0.155） after oxygen intake. In the population at low risk ofCMS, oxygen intake did not significantly change the white cell count and red cell count compared to no oxygen intake, neither in the severe symptomatic population nor in the mild symptomatic population. Conclusions： Intermittent oxygen inhalation with proper frequency might alleviate symptoms in residents at high altitude by improving their overall health conditions. Administration of oxygen inhalation therapy 2-4 times/week might not benefit populations at high risk of CMS with mild CMS symptoms while administration of therapy 7 times/week might benefit those with severe symptoms. Oxygen inhalation therapy is not recommended for low-risk CMS populations.

Serum testosterone levels and excessive erythrocytosis during the process of adaptation to high altitudes

Populations living at high altitudes （HAs）, particularly in the Peruvian Andes, are characterized by a mixture of subjects with erythrocytosis （16 g dl-1〈haemoglobin （Hb）≤21 gdl-1） and others with excessive erythrocytosis （EE） （Hb〉21 g dl-1）. Elevated haemoglobin values （EE） are associated with chronic mountain sickness, a condition reflecting the lack of adaptation to HA. According to current data, native men from regions of HA are not adequately adapted to live at such altitudes if they have elevated serum testosterone levels. This seems to be due to an increased conversion of dehydroepiandrosterone sulphate （DH EAS） to testosterone. Men with erythrocytosis at HAs show higher serum androstenedione levels and a lower testosterone/androstenedione ratio than men with EE, suggesting reduced 17beta-hydroxysteroid dehydrogenase （17beta-HSD） activity. Lower 17beta-HSD activity via A4-steroid production in men with erythrocytosis at HA may protect against elevated serum testosterone levels, thus preventing EE. The higher conversion of DHEAS to testosterone in subjects with EE indicates increased 17beta-HSD activity via the A5-pathway. Currently, there are various situations in which people live （human biodiversity） with low or high haemoglobin levels at HA. Antiquity could be an important adaptation component for life at HA, and testosterone seems to participate in this process.

Correlation between blood pressure changes and AMS, sleeping quality and exercise upon high-altitude exposure in young Chinese men

Background: Excessive elevation of arterial blood pressure(BP) at high altitude can be detrimental to our health due to acute mountain sickness(AMS) or some AMS symptoms. This prospective and observational study aimed to elucidate blood pressure changes induced by exposure to high-altitude hypoxia and the relationships of these changes with AMS prevalence, AMS severity, sleep quality and exercise condition in healthy young men.Methods: A prospective observational study was performed in 931 male young adults exposed to high altitude at 3,700 m(Lhasa) from low altitude(LA, 500 m). Blood pressure measurement and AMS symptom questionnaires were performed at LA and on day 1, 3, 5, and 7 of exposure to high altitude. Lake Louise criteria were used to diagnose AMS. Likewise, the Athens Insomnia Scale(AIS) and the Epworth Sleepiness Scale(ESS) were filled out at LA and on day 1, 3, and 7 of exposure to high altitude.Results: After acute exposure to 3,700 m, diastolic blood pressure(DBP) and mean arterial blood pressure(MABP) rose gradually and continually(P【0.05). Analysis showed a relationship with AMS for only MABP(P【0.05) but not for SBP and DBP(P】0.05). Poor sleeping quality was generally associated with higher SBP or DBP at high altitude, although inconsistent results were obtained at different time(P【0.05). SBP and Pulse BP increased noticeably after high-altitude exercise(P【0.05).Conclusions: Our data demonstrate notable blood pressure changes under exposure to different high-altitude conditions: 1) BP increased over time. 2) Higher BP generally accompanied poor sleeping quality and higher incidence of AMS. 3) SBP and Pulse BP were higher after high-altitude exercise. Therefore, we should put more effort into monitoring BP after exposure to high altitude in order to guard against excessive increases in BP.

High altitude medicine in China in the 21st century Opportunities and challenges

China has the largest plateau, Qinghai-Tibet Plateau, where inhabited the most high altitude populations. Moreover, millions of people from plain areas come to the plateau for travel and work purposes and the number of the newcomers has been increasing every year. The hypoxic environment of plateau raised a series of related health issues in the new immigrants, so have created a special medical discipline- High Altitude Medicine. Over the past decades, researches on high altitude medicine have never being ceased in China, and lots of research findings have been reported. Application and practice of these achievements have greatly decreased the mobility and mortality of highaltitude diseases, however, there remained lots of questions to be elucidated. In view of this, the authors were granted a special project from the National Health and Family Planning Commission of China, and conducted a multi-center, prospective, on-scene high altitude medicine study for the acute mountain sickness. Some innovative findings were achieved, and the parameters for diagnosis and application conditions were proposed. Furthermore, the different diagnoses and treatment effects were compared, and a more standardized, reasonable scheme was drawn up. Regarding the unbalanced medical resources in the vast high altitude area, an application system for the public and the army has been established. In the 21 st century, innovations in China and novel research approaches have provided great opportunities for the development of high altitude medicine. It is believed that the researchers in China are able to catch the opportunities and address the challenges.

High altitude headache occurs frequently among construction workers in Yushu

The aim was to measure the incidence of high altitude headache （HAH） and to determine clinical features, as well as the relation between acute mountain sickness （AMS） and HAH through a prospective study. We conducted a questionnaire-based study among construction workers in Yushu after a serious earthquake ; they were under reconstruction using a structured questionnaire incorporating International Headache Society （IHS） and AMS Lake Louise Scoring System. A total of 608 workers were enrolled after their first ascent to altitudes of 3 750-4 528 m. The results showed that 96 % reported at least 1 HAil（median 3.8, range from 1 to 10） in workers at a mean altitude of 4 250 m. The magnitude of headache was divided as mild（38 %）, moderate （44 % ） and severe （18 %）. This study indicates that HAH is the most common symptom of acute altitude exposure and closely corre- lated with altitude （r=0.165, p〈0.001）. However, 52 % of headache was one of the main symptoms of AMS, while the other 48 % was the sole symptom of HAH. On the contrary we found that 2 % of AMS without headache, thus the ＂painless AMS＂ actually existed. The clinical features of HAH are presented, and the relationship between AMS and HAH is discussed.