Does This Patient Have Acute Mountain Sickness?: The Rational Clinical Examination Systematic Review

Altitude illnesses

Millions of people visit high-altitude regions annually and more than 80 million live permanently above 2,500 m. Acute high-altitude exposure can trigger high-altitude illnesses (HAIs), including acute mountain sickness (AMS), high-altitude cerebral oedema (HACE) and high-altitude pulmonary oedema (HAPE). Chronic mountain sickness (CMS) can affect high-altitude resident populations worldwide. The prevalence of acute HAIs varies according to acclimatization status, rate of ascent and individual susceptibility. AMS, characterized by headache, nausea, dizziness and fatigue, is usually benign and self-limiting, and has been linked to hypoxia-induced cerebral blood volume increases, inflammation and related trigeminovascular system activation. Disruption of the blood-brain barrier leads to HACE, characterized by altered mental status and ataxia, and increased pulmonary capillary pressure, and related stress failure induces HAPE, characterized by dyspnoea, cough and exercise intolerance. Both conditions are progressive and life-threatening, requiring immediate medical intervention. Treatment includes supplemental oxygen and descent with appropriate pharmacological therapy. Preventive measures include slow ascent, pre-acclimatization and, in some instances, medications. CMS is characterized by excessive erythrocytosis and related clinical symptoms. In severe CMS, temporary or permanent relocation to low altitude is recommended. Future research should focus on more objective diagnostic tools to enable prompt treatment, improved identification of individual susceptibilities and effective acclimatization and prevention options.

Investigating Sea-Level Brain Predictors for Acute Mountain Sickness: A Multimodal MRI Study before and after High-Altitude Exposure

BACKGROUND AND PURPOSE

Acute mountain sickness is a series of brain-centered symptoms that occur when rapidly ascending to high altitude. Predicting acute mountain sickness before high-altitude exposure is crucial for protecting susceptible individuals. The present study aimed to evaluate the feasibility of predicting acute mountain sickness after high-altitude exposure by using multimodal brain MR imaging features measured at sea level.

MATERIALS AND METHODS

We recruited 45 healthy sea-level residents who flew to the Qinghai-Tibet Plateau (3650 m). We conducted T1-weighted structural MR imaging, resting-state fMRI, and arterial spin-labeling perfusion MR imaging both at sea level and high altitude. Acute mountain sickness was diagnosed for 5 days using Lake Louise Scoring. Logistic regression with Least Absolute Shrinkage and Selection Operator logistic regression was performed for predicting acute mountain sickness using sea-level MR imaging features. We also validated the predictors by using MR images obtained at high altitude.

RESULTS

The incidence rate of acute mountain sickness was 80.0%. The model achieved an area under the receiver operating characteristic curve of 86.4% (sensitivity = 77.8%, specificity = 100.0%, and P < .001) in predicting acute mountain sickness At sea level, valid predictors included fractional amplitude of low-frequency fluctuations (fALFF) and degree centrality from resting-state fMRI, mainly distributed in the somatomotor network. We further learned that the acute mountain sickness group had lower levels of fALFF in the somatomotor network at high altitude, associated with smaller changes in CSF volume and higher Lake Louise Scoring, specifically relating to fatigue and clinical function.

CONCLUSIONS

Our study found that the somatomotor network function detected by sea-level resting-state fMRI was a crucial predictor for acute mountain sickness and further validated its pathophysiologic impact at high altitude. These findings show promise for pre-exposure prediction, particularly for individuals in need of rapid ascent, and they offer insight into the potential mechanism of acute mountain sickness.

Notoginsenoside R1 treatment facilitated Nrf2 nuclear translocation to suppress ferroptosis via Keap1/Nrf2 signaling pathway to alleviated high-altitude myocardial injury

High-altitude myocardial injury (HAMI) represents a critical form of altitude illness for which effective drug therapies are generally lacking. Notoginsenoside R1, a prominent constituent derived from Panax notoginseng, has demonstrated various cardioprotective properties in models of myocardial ischemia/reperfusion injury, sepsis-induced cardiomyopathy, cardiac fibrosis, and myocardial injury. The potential utility of notoginsenoside R1 in the management of HAMI warrants prompt investigation. Following the successful construction of a HAMI model, a series of experimental analyses were conducted to assess the effects of notoginsenoside R1 at dosages of 50 mg/Kg and 100 mg/Kg. The results indicated that notoginsenoside R1 exhibited protective effects against hypoxic injury by reducing levels of CK, CK-MB, LDH, and BNP, leading to improved cardiac function and decreased incidence of arrhythmias. Furthermore, notoginsenoside R1 was found to enhance Nrf2 nuclear translocation, subsequently regulating the SLC7A11/GPX4/HO-1 pathway and iron metabolism to mitigate ferroptosis, thereby mitigating cardiac inflammation and oxidative stress induced by high-altitude conditions. In addition, the application of ML385 has confirmed the involvement of Nrf2 nuclear translocation in the therapeutic approach to HAMI. Collectively, the advantageous impacts of notoginsenoside R1 on HAMI have been linked to the suppression of ferroptosis via Nrf2 nuclear translocation signaling.

Gastrointestinal syndrome encountered during a train voyage to high altitudes: A 14-day survey of 69 passengers in China

BACKGROUND

The diagnosis and evaluation of the severity of acute mountain sickness (AMS) continue to be problematic due to a lack of consensus on the inclusion of symptoms in a scoring system. Recent investigations highlight the significance of gastrointestinal symptoms in identifying this condition. However, the specific gastrointestinal symptoms associated with AMS have not been thoroughly elucidated in previous studies, and the underlying risk factors remain inadequately comprehended.

METHODS

This study aimed to investigate the characteristics, trends, and risk factors related to gastrointestinal symptoms encountered during train travel to high altitude. A total of 69 passengers, specifically all with medical backgrounds, were surveyed 6 times over a period of 14 days.

RESULTS

The daily incidence of abdominal discomfort was higher than non-gastrointestinal symptoms within 14 days. Gastrointestinal symptoms demonstrated a greater prevalence, longer duration, and increased risk compared to non-gastrointestinal symptoms, such as headaches. The symptoms of abdominal distension and bowel sound hyperaction were found to be prevalent and persistent among patients diagnosed with AMS, exhibiting a high incidence rate. Gender, age, body mass index (BMI), smoking habits, and alcohol consumption were identified as risk factors associated with the occurrence and duration of gastrointestinal symptoms.

CONCLUSION

This study suggests that gastrointestinal symptoms are more common and persistent when traveling to the plateau by train. These symptoms should be taken into consideration in the further diagnosis and prevention of AMS. Therefore, this study provides a significant theoretical foundation for the prevention and treatment of AMS.

Aldehyde dehydrogenase 2 serves as a key cardiometabolic adaptation regulator in response to plateau hypoxia in mice

High-altitude heart disease (HAHD) is a complex pathophysiological condition related to systemic hypobaric hypoxia in response to transitioning to high altitude. Hypoxia can cause myocardial metabolic dysregulation, leading to an increased risk of heart failure and sudden cardiac death. Aldehyde dehydrogenase 2 (ALDH2) could regulate myocardial energy metabolism and plays a protective role in various cardiovascular diseases. This study aims to determine the effects of plateau hypoxia (PH) on cardiac metabolism and function, investigate the associated role of ALDH2, and explore potential therapeutic targets. We discovered that PH significantly reduced survival rate and cardiac function. These effects were exacerbated by ALDH2 deficiency. PH also caused a shift in the myocardial fuel source from fatty acids to glucose; ALDH2 deficiency impaired this adaptive metabolic shift. Untargeted/targeted metabolomics and transmission electron microscopy revealed that ALDH2 deficiency promoted myocardial fatty-acid deposition, leading to enhanced fatty-acid transport, lipotoxicity and mitochondrial dysfunction. Furthermore, results showed that ALDH2 attenuated PH-induced impairment of adaptive metabolic programs through 4-HNE/CPT1 signaling, and the CPT1 inhibitor etomoxir significantly ameliorated ALDH2 deficiency-induced cardiac impairment and improved survival in PH mice. Together, our data reveal ALDH2 acts as a key cardiometabolic adaptation regulator in response to PH. CPT1 inhibitor, etomoxir, may attenuate ALDH2 deficiency-induced effects and improved cardiac function in response to PH.

Assessment of Acute Mountain Sickness: Comparing the Chinese AMS Score to the Lake Louise Score

Wu, Yu, Wenqi Zhao, Bao Liu, Jianyang Zhang, Zhifeng Zhong, Simin Zhou, Jiaxin Xie, Yuqi Gao, Peng Li, and Jian Chen. Assessment of Acute Mountain Sickness: Comparing the Chinese Ams Score to the Lake Louise Score. High Alt Med Biol 00:000-000, 2024. Objective: To compare the ability of the Chinese AMS Score (CAS) to detect acute mountain sickness (AMS) using the 2018 version of the Lake Louise Score (LLS) as reference. Methods: After flying from Chengdu (altitude: 500 m) to Lhasa (3,658 m), 2,486 young men completed a questionnaire. The questionnaire contained LLS and CAS items. An LLS ≥3 and/or a CAS ≥cutoff were used as the criteria for AMS. Hierarchical cluster analysis and two-step cluster analysis were used to investigate relationships between the symptoms. Results: AMS incidence rates were 33.8% (n = 840) with the LLS and 59.3% (n = 1,473) with the CAS (χ2 = 872.5, p < 0.001). The LLS and CAS had a linear relationship (orthogonal regression, Pearson r = 0.91, p < 0.001). With the LLS as the standard, the CAS had high diagnostic accuracy (area under the curve = 0.95, 95% confidence interval: 0.94-0.96). However, with the CAS, 25.5% (n = 633) more participants were labeled as having AMS than with the LLS (false positives). Two clusters were identified: one with headache only (419 participants, 66.2%) and one without headache but with other symptoms (214 participants, 33.8%). Reducing the weight of headache in the CAS allowed to align CAS and LLS. Conclusion: In comparison to the LLS, the CAS has a sensitivity close to 100% but lacks specificity given the high rate of false positives. The different weight of headaches may be the main reason for the discrepancy.

Wilderness Medical Society Clinical Practice Guidelines for the Prevention, Diagnosis, and Treatment of Acute Altitude Illness: 2024 Update

To provide guidance to clinicians about best practices, the Wilderness Medical Society (WMS) convened an expert panel to develop evidence-based guidelines for prevention, diagnosis, and treatment of acute mountain sickness, high altitude cerebral edema, and high altitude pulmonary edema. Recommendations are graded based on the quality of supporting evidence and the balance between the benefits and risks/burdens according to criteria put forth by the American College of Chest Physicians. The guidelines also provide suggested approaches for managing each form of acute altitude illness that incorporate these recommendations as well as recommendations on how to approach high altitude travel following COVID-19 infection. This is an updated version of the original WMS Consensus Guidelines for the Prevention and Treatment of Acute Altitude Illness published in Wilderness & Environmental Medicine in 2010 and the subsequently updated WMS Practice Guidelines for the Prevention and Treatment of Acute Altitude Illness published in 2014 and 2019.

Evaluation of cardiac index and right ventricular hypertrophy index in rats under a chronic hypoxic environment at high altitude

High-altitude areas are characterized by low pressure and hypoxia, which have a significant impact on various body systems. This study aimed to investigate the alterations in cardiac index and right ventricular hypertrophy index(RVHI) in rats at different altitudes.Twenty-one male Sprague-Dawley (SD) rats aged 4 weeks were randomly divided into three groups based on altitude. The rats were raised for 28 weeks and then transferred to Qinghai University Plateau Medicine Laboratory. Body weight was measured, heart organs were isolated and weighed, and cardiac index and right ventricular hypertrophy index were determined. Statistical analysis was performed on the data from the three groups. Compared with the plain group, the body weight of the middle-altitude group was significantly decreased (P < 0.05), and cardiac index, RVHI-1, RVHI-2 increased significantly ((P < 0.05). The body weight, whole heart mass, right ventricular mass were significantly decreased in high-altitude group (P < 0.05), RVHI-1 and RVHI-2 were significantly increased (P < 0.05). Compared with the middle-altitude group, the body weight, whole heart mass and right ventricular mass of the high-altitude group were significantly decreased (P < 0.05), and RVHI-1 and RVHI-2 were significantly increased (P < 0.05). Increasing altitude led to a decrease in body weight, whole heart mass, and right ventricular mass in rats, indicating structural changes in the right heart. Additionally, the proportion of right heart to body weight and whole heart increased with altitude.

Acute mountain sickness on Jade Mountain: Results from the real-world practice (2018-2019)

Acute mountain sickness (AMS) is initiated in response to a hypoxic and hypobaric environment at a high altitude. The precise prevalence of AMS in Jade Mountain climbers remained largely unknown, particularly data obtained from real medical consultations. An overnight stay at the Pai-Yun Lodge (3402 m) is usually required before an ascent of the Jade Mountain. Since 2004, a Pai-Yun Clinic has been established in the Pai-Yun Lodge. The Pai-Yun Clinic provided regular and emergency medical service every weekend. We conducted a retrospective study by using medical records from the Pai-Yun Clinic between 2018 and 2019. A total of 1021 patients were enrolled, with 56.2 % males. Different age groups were 3.2 %, 54.5 %, 37.9 %, and 4.4 % in <20, 20-39, 40-59, and ≥60 years, respectively. There were 582 (57.0 %) patients diagnosed to have AMS (230 [39.5 %] were mild type and 352 [60.5 %] were severe type). The factors associated with AMS development included young age, absence of climbing history (>3000 m) within the last 3 months, first climbing (>3000 m) experience, taking preventive medication, low oxygen saturation, and a high Lake Louise AMS score (LLAMSS). The factors associated with AMS severity included absence of taking preventive medication, low oxygen saturation, and a high LLAMSS. Approximately 15 % of Jade Mountain climbers needed medical service, of which 60 % had AMS. 60 % of patients with AMS must require oxygen supply or medication prescription. Oxygen saturation measure and LLAMSS evaluation are reasonable tools to predict the occurrence and severity of AMS on Jade Mountain.

Injuries and medical emergencies among international travellers

BACKGROUND

Tropical infectious diseases and vaccine-preventable emergencies are the mainstay of pre-travel consultations. However, non-communicable diseases, injuries and accidents that occur during travel are not emphasized enough in these settings.

METHODS

We performed a narrative review based on a literature search of PubMed, Google Scholar, UpToDate, DynaMed and LiSSa and on reference textbooks and medical journals dedicated to travel, emergency and wilderness medicine. Relevant secondary references were extracted. We also aimed to discuss newer or neglected issues, such as medical tourism, Coronavirus Disease 2019, exacerbations of co-morbidities associated with international travel, insurance coverage, health care seeking abroad, medical evacuation or repatriation and tips for different types of travellers' emergency medical kits (personal, group, physician handled).

RESULTS

All sources reviewed led to the selection of >170 references. Among epidemiological data on morbidity and deaths while abroad, only retrospective data are available. Deaths are estimated to occur in 1 in 100 000 travellers, with 40% caused by trauma and 60% by diseases, and <3% linked to infectious diseases. Trauma and other injuries acquired during travel, such as traffic accidents and drowning, can be reduced by up to 85% with simple preventive recommendations such as avoiding simultaneous alcohol intake. In-flight emergencies occur on 1 in 604 flights on average. Thrombosis risk is two to three times greater for travellers than for non-travellers. Fever during or after travel can occur in 2-4% of travellers, but in up to 25-30% in tertiary centres. Traveller's diarrhoea, although rarely severe, is the most common disease associated with travel. Autochthonous emergencies (acute appendicitis, ectopic pregnancy, dental abscess) can also occur.

CONCLUSIONS

Pre-travel medicine encounters must include the topic of injuries and medical emergencies, such as the risk-taking behaviours and foster better planning in a comprehensive approach along with vaccines and infectious diseases advices.

Effects of acetazolamide combined with remote ischemic preconditioning on risk of acute mountain sickness: a randomized clinical trial

BACKGROUND

We aimed to determine whether and how the combination of acetazolamide and remote ischemic preconditioning (RIPC) reduced the incidence and severity of acute mountain sickness (AMS).

METHODS

This is a prospective, randomized, open-label, blinded endpoint (PROBE) study involving 250 healthy volunteers. Participants were randomized (1:1:1:1:1) to following five groups: Ripc (RIPC twice daily, 6 days), Rapid-Ripc (RIPC four times daily, 3 days), Acetazolamide (twice daily, 2 days), Combined (Acetazolamide plus Rapid-Ripc), and Control group. After interventions, participants entered a normobaric hypoxic chamber (equivalent to 4000 m) and stayed for 6 h. The primary outcomes included the incidence and severity of AMS, and SpO2 after hypoxic exposure. Secondary outcomes included systolic and diastolic blood pressure, and heart rate after hypoxic exposure. The mechanisms of the combined regime were investigated through exploratory outcomes, including analysis of venous blood gas, complete blood count, human cytokine antibody array, ELISA validation for PDGF-AB, and detection of PDGF gene polymorphisms.

RESULTS

The combination of acetazolamide and RIPC exhibited powerful efficacy in preventing AMS, reducing the incidence of AMS from 26.0 to 6.0% (Combined vs Control: RR 0.23, 95% CI 0.07-0.70, P = 0.006), without significantly increasing the incidence of adverse reactions. Combined group also showed the lowest AMS score (0.92 ± 1.10). Mechanistically, acetazolamide induced a mild metabolic acidosis (pH 7.30 ~ 7.31; HCO3- 18.1 ~ 20.8 mmol/L) and improved SpO2 (89 ~ 91%) following hypoxic exposure. Additionally, thirty differentially expressed proteins (DEPs) related to immune-inflammatory process were identified after hypoxia, among which PDGF-AB was involved. Further validation of PDGF-AB in all individuals showed that both acetazolamide and RIPC downregulated PDGF-AB before hypoxic exposure, suggesting a possible protective mechanism. Furthermore, genetic analyses demonstrated that individuals carrying the PDGFA rs2070958 C allele, rs9690350 G allele, or rs1800814 G allele did not display a decrease in PDGF-AB levels after interventions, and were associated with a higher risk of AMS.

CONCLUSIONS

The combination of acetazolamide and RIPC exerts a powerful anti-hypoxic effect and represents an innovative and promising strategy for rapid ascent to high altitudes. Acetazolamide improves oxygen saturation. RIPC further aids acetazolamide, which synergistically regulates PDGF-AB, potentially involved in the pathogenesis of AMS.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05023941.

Evaluation of blood cellular and biochemical parameters in rats under a chronic hypoxic environment at high altitude

BACKGROUND

The purpose of this study was to explore the changes in blood cellular and biochemical parameters of rats in a natural environment of low pressure and low oxygen on the plateau.

METHODS

Male Sprague-Dawley rats in two groups were raised in different environments from 4 weeks of age for a period of 24 weeks. They were raised to 28 weeks of age and then transported to the plateau medical laboratory of Qinghai University. Blood cellular and biochemical parameters were measured and the data of the two groups were statistically analyzed.

RESULTS

1. RBC in the HA group was higher than that in the Control group, but there was no significant difference between the two groups (p > 0.05), Compared with the Control group, HGB, MCV, MCH, MCHC and RDW in the HA group were significantly higher (p < 0.05). 2. Compared with the Control group, WBC, LYMP, EO, LYMP% and EO% in the HA group decreased significantly (p < 0.05), and ANC% increased significantly (p < 0.05). 3. In the platelet index, compared with the Control group, PLT in the HA group was significantly reduced (p < 0.05), PDW, MRV, P-LCR were significantly increased (p < 0.05). 4. In blood biochemical indicators, compared with the Control group, AST, TBIL, IBIL, LDH in the HA group decreased significantly (p < 0.05), CK in the HA group increased significantly (p < 0.05).

CONCLUSIONS

1. The indexes related to red blood cells, white blood cells, platelets and some biochemical indexes in the blood of rats at high altitude have changed. 2. Under the high altitude environment, the oxygen carrying capacity of SD rats is improved, the resistance to disease may be reduced, the coagulation and hemostasis functions may be affected, and there is a risk of bleeding. The liver function, renal function, heart function and skeletal muscle energy metabolism may be affected. 3. This study can provide an experimental basis for the research on the pathogenesis of high-altitude diseases from the perspective of blood.KEY MESSAGESIn this study, red blood cells, white blood cells, platelets and blood biochemical indicators were included in the real plateau environment to comprehensively analyze the changes of blood cellular and biochemical parameters in rats under the chronic plateau hypobaric hypoxia environment.From the perspective of blood, this study can provide an experimental basis for research on the pathogenesis of high-altitude diseases.Explore the data support of oxygen-carrying capacity, disease resistance and energy metabolism of the body in the natural environment at high altitude.

Anxiety as a Risk Factor for Acute Mountain Sickness Among Young Chinese Men After Exposure at 3800 M: A cross‒sectional Study

Purpose

We aimed to explore whether anxiety is a risk factor for acute mountain sickness [AMS] in a young Chinese male population.

Patients and Methods

A total of 143 young Chinese men with a median age of 23 years (IQR, 21-25) were employed in the present study, and they were divided into the AMS+ and AMS- groups according to the Lake Louise AMS score [AMS-S] after exposure at 3800 m for two days. Participants' pulse oximeter saturation [SpO2] and heart rate [HR] were measured. AMS was evaluated using the AMS-S. The anxiety and sleep quality of the subjects were assessed using the Zung Self-Rating Anxiety Scale [SAS] and the Athens Insomnia Scale [AIS], respectively. Outcomes were analysed using Spearman's partial correlation and logistic regression analysis.

Results

After two days of exposure at 3800 m, the overall prevalence of AMS was 54% in the whole group. The HR was significantly higher in the AMS+ group than in the AMS- group, as well as the SAS score and AIS score. A converse pattern was observed for SpO2. A significant difference was observed for the change in SAS and AIS score between the AMS+ and AMS- groups. Correlation analysis showed that AMS-S was positively correlated with SAS score, AIS score, HR, ΔSAS score, ΔAIS score, and ΔHR but negatively correlated with SpO2. AIS score was positively correlated with SAS score. After logistic regression analysis was adjusted for HR, SpO2, ΔAIS and ΔHR, SAS score (OR=1.446, 95% CI 1.200-1.744, p<0.001), AIS score (OR=1.216, 95% CI 1.033-1.432) and ΔSAS score (OR=1.158, 95% CI 1.012-1.327) were identified as independent risk factors for AMS.

Conclusion

The present study suggests that anxiety is a risk factor for AMS among young Chinese men, and poor sleep quality may partially mediate the association.

Oxygen enrichment protects against intestinal damage and gut microbiota disturbance in rats exposed to acute high-altitude hypoxia

Acute high-altitude hypoxia can lead to intestinal damage and changes in gut microbiota. Sustained and reliable oxygen enrichment can resist hypoxic damage at high altitude to a certain extent. However, it remains unclear whether oxygen enrichment can protect against gut damage and changes in intestinal flora caused by acute altitude hypoxia. For this study, eighteen male Sprague-Dawley rats were divided into three groups, control (NN), hypobaric hypoxic (HH), and oxygen-enriched (HO). The NN group was raised under normobaric normoxia, whereas the HH group was placed in a hypobaric hypoxic chamber simulating 7,000 m for 3 days. The HO group was exposed to oxygen-enriched air in the same hypobaric hypoxic chamber as the HH group for 12 h daily. Our findings indicate that an acute HH environment caused a fracture of the crypt structure, loss of epithelial cells, and reduction in goblet cells. Additionally, the structure and diversity of bacteria decreased in richness and evenness. The species composition at Phylum and Genus level was characterized by a higher ratio of Firmicutes and Bacteroides and an increased abundance of Lactobacillus with the abundance of Prevotellaceae_NK3B31_group decreased in the HH group. Interestingly, after oxygen enrichment intervention, the intestinal injury was significantly restrained. This was confirmed by an increase in the crypt depth, intact epithelial cell morphology, increased relative density of goblet cells, and higher evenness and richness of the gut microbiota, Bacteroidetes and Prevotellaceae as the main microbiota in the HO group. Finally, functional analysis showed significant differences between the different groups with respect to different metabolic pathways, including Amino acid metabolism, energy metabolism, and metabolism. In conclusion, this study verifies, for the first time, the positive effects of oxygen enrichment on gut structure and microbiota in animals experiencing acute hypobaric hypoxia.

Pretreatment with Notoginsenoside R1 attenuates high-altitude hypoxia-induced cardiac injury via activation of the ERK1/2-P90RSK-Bad signaling pathway in rats

High-altitude cardiac injury (HACI) is one of the common tissue injuries caused by high-altitude hypoxia that may be life threatening. Notoginsenoside R1 (NG-R1), a major saponin of Panax notoginseng, exerts anti-oxidative, anti-inflammatory, and anti-apoptosis effects, protecting the myocardium from hypoxic injury. This study aimed to investigate the protective effect and molecular mechanism of NG-R1 against HACI. We simulated a 6000 m environment for 48 h in a hypobaric chamber to create a HACI rat model. Rats were pretreated with NG-R1 (50, 100 mg/kg) or dexamethasone (4 mg/kg) for 3 days and then placed in the chamber for 48 h. The effect of NG-R1 was evaluated by changes in Electrocardiogram parameters, histopathology, cardiac biomarkers, oxidative stress and inflammatory indicators, key protein expression, and immunofluorescence. U0126 was used to verify whether the anti-apoptotic effect of NG-R1 was related to the activation of ERK pathway. Pretreatment with NG-R1 can improve abnormal cardiac electrical conduction and alleviate high-altitude-induced tachycardia. Similar to dexamethasone, NG-R1 can improve pathological damage, reduce the levels of cardiac injury biomarkers, oxidative stress, and inflammatory indicators, and down-regulate the expression of hypoxia-related proteins HIF-1α and VEGF. In addition, NG-R1 reduced cardiomyocyte apoptosis by down-regulating the expression of apoptotic proteins Bax, cleaved caspase 3, cleaved caspase 9, and cleaved PARP1 and up-regulating the expression of anti-apoptotic protein Bcl-2 through activating the ERK1/2-P90RSK-Bad pathway. In conclusion, NG-R1 prevented HACI and suppressed apoptosis via activation of the ERK1/2-P90RSK-Bad pathway, indicating that NG-R1 has therapeutic potential to treat HACI.

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

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

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

Background

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.

Methods

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.

Results

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.

Conclusion

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.

Prevalence and knowledge about acute mountain sickness in the Western Alps

OBJECTIVE

To assess the prevalence of acute mountain sickness (AMS) in 1370 mountaineers at four different altitudes in the Western Alps. We also examined the influence of potential risk factors and the knowledge about AMS on its prevalence.

METHODS

In this observational cross-sectional study AMS was assessed on the day of ascent by the Lake Louise score (LLS, cut-off ≥3, version 2018) and the AMS-Cerebral (AMS-C) score of the environmental symptom questionnaire (cut-off ≥0,70). The latter was also obtained in the next morning. Knowledge regarding AMS and high-altitude cerebral edema (HACE) and the potential risk factors for AMS were evaluated by questionnaires.

RESULTS

On the day of ascent, the prevalence of AMS assessed by the LLS and AMS-C score was 5.8 and 3.9% at 2850 m, 2.1 and 3.1% at 3050 m, 14.8 and 10.1% at 3650 m, and 21.9 and 15% at 4559 m, respectively. The AMS prevalence increased overnight from 10.1 to 14.5% and from 15 to 25.2% at 3650 m and 4559 m, respectively, and was unchanged at 2850 m and 3050 m. A history of AMS, higher altitude, lower degree of pre-acclimatization, and younger age were identified as risk factors for developing AMS. Slow ascent was weakly associated with AMS prevalence, and sex and knowledge about AMS and HACE were indistinct.

CONCLUSION

AMS is common at altitudes ≥ 3650 m and better knowledge about AMS and HACE was not associated with less AMS in mountaineers with on average little knowledge.

Promising Natural Medicines for the Treatment of High-Altitude Illness

Li Li, Lin Lin, Bo Wen, Peng-cheng Zhao, Da-sheng Liu, Guo-ming Pang, Zi-rong Wang, Yong Tan, and Cheng Lu. Promising natural medicines for the treatment of high-altitude illness. High Alt Med Biol. 24:175-185, 2023.-High-altitude illness (HAI) is a dangerous disease characterized by oxidative stress, inflammatory damage and hemodynamic changes in the body that can lead to severe damage to the lungs, heart, and brain. Natural medicines are widely known for their multiple active ingredients and pharmacological effects, which may be important in the treatment of HAI. In this review, we outline the specific types of HAI and the underlying pathological mechanisms and summarize the currently documented natural medicines applied in the treatment of acute mountain sickness and high-altitude cerebral edema, high-altitude pulmonary edema, chronic mountain sickness, and high-altitude pulmonary hypertension. Their sources, types, and medicinal sites are summarized, and their active ingredients, pharmacological effects, related mechanisms, and potential toxicity are discussed. In conclusion, natural medicines, as an acceptable complementary and alternative strategy with fewer side effects and more long-term application, can provide a reference for developing more natural antialtitude sickness medicines in the future and have good application prospects in HAI treatment.

Smartwatch-Based Maximum Oxygen Consumption Measurement for Predicting Acute Mountain Sickness: Diagnostic Accuracy Evaluation Study

BACKGROUND

Cardiorespiratory fitness plays an important role in coping with hypoxic stress at high altitudes. However, the association of cardiorespiratory fitness with the development of acute mountain sickness (AMS) has not yet been evaluated. Wearable technology devices provide a feasible assessment of cardiorespiratory fitness, which is quantifiable as maximum oxygen consumption (VO2max) and may contribute to AMS prediction.

OBJECTIVE

We aimed to determine the validity of VO2max estimated by the smartwatch test (SWT), which can be self-administered, in order to overcome the limitations of clinical VO2max measurements. We also aimed to evaluate the performance of a VO2max-SWT-based model in predicting susceptibility to AMS.

METHODS

Both SWT and cardiopulmonary exercise test (CPET) were performed for VO2max measurements in 46 healthy participants at low altitude (300 m) and in 41 of them at high altitude (3900 m). The characteristics of the red blood cells and hemoglobin levels in all the participants were analyzed by routine blood examination before the exercise tests. The Bland-Altman method was used for bias and precision assessment. Multivariate logistic regression was performed to analyze the correlation between AMS and the candidate variables. A receiver operating characteristic curve was used to evaluate the efficacy of VO2max in predicting AMS.

RESULTS

VO2max decreased after acute high altitude exposure, as measured by CPET (25.20 [SD 6.46] vs 30.17 [SD 5.01] at low altitude; P<.001) and SWT (26.17 [SD 6.71] vs 31.28 [SD 5.17] at low altitude; P<.001). Both at low and high altitudes, VO2max was slightly overestimated by SWT but had considerable accuracy as the mean absolute percentage error (<7%) and mean absolute error (<2 mL·kg-1·min-1), with a relatively small bias compared with VO2max-CPET. Twenty of the 46 participants developed AMS at 3900 m, and their VO2max was significantly lower than that of those without AMS (CPET: 27.80 [SD 4.55] vs 32.00 [SD 4.64], respectively; P=.004; SWT: 28.00 [IQR 25.25-32.00] vs 32.00 [IQR 30.00-37.00], respectively; P=.001). VO2max-CPET, VO2max-SWT, and red blood cell distribution width-coefficient of variation (RDW-CV) were found to be independent predictors of AMS. To increase the prediction accuracy, we used combination models. The combination of VO2max-SWT and RDW-CV showed the largest area under the curve for all parameters and models, which increased the area under the curve from 0.785 for VO2max-SWT alone to 0.839.

CONCLUSIONS

Our study demonstrates that the smartwatch device can be a feasible approach for estimating VO2max. In both low and high altitudes, VO2max-SWT showed a systematic bias toward a calibration point, slightly overestimating the proper VO2max when investigated in healthy participants. The SWT-based VO2max at low altitude is an effective indicator of AMS and helps to better identify susceptible individuals following acute high-altitude exposure, particularly by combining the RDW-CV at low altitude.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR2200059900; https://www.chictr.org.cn/showproj.html?proj=170253.

Remote ischemic preconditioning improves spatial memory and sleep of young males during acute high-altitude exposure

OBJECTIVE

The high-altitude hypoxia environment will cause poor acclimatization in a portion of the population. Remote ischemic preconditioning（RIPC）has been demonstrated to prevent cardiovascular and cerebrovascular diseases under ischemic or hypoxic conditions. However, its role in improving acclimatization and preventing acute mountain sickness (AMS) at high altitude has been undetermined. This study aims to estimate the effect of RIPC on acclimatization of individuals exposed to high altitude.

METHODS

The project was designed as a randomized controlled trial with 82 healthy young males, who received RIPC training once a day for 7 consecutive days. Then they were transported by aircraft to a high altitude (3680 m) and examined for 6 days. Lake Louise Score(LLS) of AMS, physiological index, self-reported sleep pattern, and Pittsburgh Sleep Quality Index（PSQI）score were applied to assess the acclimatization to the high altitude. Five neurobehavioral tests were conducted to assess cognitive function.

RESULTS

The result showed that the RIPC group had a significantly lower AMSscore than the control group (2.43 ± 1.58 vs 3.29 ± 2.03, respectively; adjusted mean difference-0.84, 95% confidence interval-1.61 to -0.06, P = 0.036). and there was no significant difference in AMS incidence between the two groups (25.0% vs 28.57%, P = 0.555). The RIPC group performed better than the control group in spatial memory span score (11[9-12] vs 10[7.5-11], P=0.025) and the passing digit (7[6-7.5] vs 6[5-7], P= 0.001). Spatial memory was significantly higher in the high-altitude RIPC group than in the low-altitude RIPC group (P＜0.01). And the RIPC group obtained significantly lower self-reported sleep quality score (P = 0.024) and PSQI score (P = 0.031).

CONCLUSIONS

The RIPC treatment improved spatial memory and sleep quality in subjects exposed to acute hypoxic exposure and this may lead to improved performance at high altitude.

Synthesis of Schiff Bases Containing Phenol Rings and Investigation of Their Antioxidant Capacity, Anticholinesterase, Butyrylcholinesterase, and Carbonic Anhydrase Inhibition Properties

The widespread usage of Schiff bases in chemistry, industry, medicine, and pharmacy has increased interest in these compounds. Schiff bases and derivative compounds have important bioactive properties. Heterocyclic compounds containing phenol derivative groups in their structure have the potential to capture free radicals that can cause diseases. In this study, we designed and synthesized eight Schiff bases (10–15) and hydrazineylidene derivatives (16–17), which contain phenol moieties and have the potential to be used as synthetic antioxidants, for the first time using microwave energy. Additionally, the antioxidant effects of Schiff bases (10–15) and hydrazineylidene derivatives (16–17) were studied using by the bioanalytical methods of 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) cation radical (ABTS•+) and 1,1-diphenyl-2-picrylhydrazyl (DPPH•) scavenging activities, and Fe3+, Cu2+, and Fe3+-TPTZ complex reducing capacities. In the context of studies on antioxidants, Schiff bases (10–15) and hydrazineylidene derivatives (16–17) were found to be as powerful DPPH (IC50: 12.15–99.01 μg/mL) and ABTS•+ (IC50: 4.30–34.65 μg/mL). Additionally, the inhibition abilities of Schiff bases (10–15) and hydrazineylidene derivatives (16–17) were determined towards some metabolic enzymes including acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and human carbonic anhydrase I and II (hCAs I and II), enzymes that are linked to some global disorders including Alzheimer’s disease (AD), epilepsy, and glaucoma. In the context of studies on enzyme inhibition, it was observed that the synthesized Schiff bases (10–15) and hydrazineylidene derivatives (16–17) inhibited AChE, BChE, hCAs I, and hCA II enzymes with IC50 values in ranges of 16.11–57.75 nM, 19.80–53.31 nM, 26.08 ± 8.53 nM, and 85.79 ± 24.80 nM, respectively. In addition, in light of the results obtained, we hope that this study will be useful and guiding for the evaluation of biological activities in the fields of the food, medical, and pharmaceutical industries in the future.

Retinal microvasculature is a potential biomarker for acute mountain sickness

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

Acute Mountain Sickness and the Risk of Subsequent Psychiatric Disorders-A Nationwide Cohort Study in Taiwan

We aim to explore if there is a relationship between acute mountain sickness (AMS) and the risk of psychiatric disorders in Taiwan by using the National Health Insurance Research Database for to the rare studies on this topic. We enrolled 127 patients with AMS, and 1270 controls matched for sex, age, monthly insured premiums, comorbidities, seasons for medical help, residences, urbanization level, levels of care, and index dates were chosen from 1 January 2000 to 31 December 2015. There were 49 patients with AMS and 140 controls developed psychiatric disorders within the 16-year follow-up. The Fine-Gray model analyzed that the patients with AMS were prone to have a greater risk for the development of psychiatric disorders with an adjusted sub-distribution hazard ratio (sHRs) of 10.384 (95% confidence interval [CI]: 7.267-14.838, p < 0.001) for psychiatric disorders. The AMS group was associated with anxiety disorders, depressive disorders, bipolar disorder, sleep disorders, posttraumatic stress disorder/acute stress disorder, psychotic disorder, and substance-related disorder (SRD). The relationship between anxiety, depression, sleep disorders, SRD, and AMS still persisted even after we excluded the psychiatric disorders within the first five years after AMS. There was an association between AMS and the rising risk of psychiatric disorders in the 16 years of long-term follow-up research.

Effect of Acetazolamide on Postural Control in Patients with COPD Travelling to 3100 m Randomized Trial

Patients with chronic obstructive pulmonary disease (COPD) may be susceptible to impairments in postural control (PC) when exposed to hypoxia at high altitude. This randomized, placebo-controlled, double-blind, parallel-design trial evaluated the effect of preventive acetazolamide treatment on PC in lowlanders with COPD traveling to 3100 m. 127 lowlanders (85 men, 42 women) with moderate to severe COPD, aged 57 ± 8 y, living below 800 m, were randomized to treatment with acetazolamide 375 mg/d starting 24 h before ascent from 760 m to 3100 m and during a 2-day sojourn in a clinic at 3100 m. PC was evaluated at both altitudes with a balance platform on which patients were standing during five tests of 30 s each. The primary outcome was the center of pressure path length (COPL). In the placebo group, COPL significantly increased from (mean ± SD) 28.8 ± 9.7 cm at 760 m to 30.0 ± 10.0 cm at 3100 m (p = 0.002). In the acetazolamide group, COPL at 760 m and 3100 m were similar with 27.6 ± 9.6 cm and 28.4 ± 9.7 cm (p = 0.069). The mean between-groups difference (acetazolamide-placebo) in altitude-induced change of COPL was -0.54 cm (95%CI -1.66 to 0.58, p = 0.289). Multivariable regression analysis confirmed an increase in COPL of 0.98 cm (0.39 to 1.58, p = 0.001) with ascent from 760 to 3100 m, but no significant effect of acetazolamide (0.66 cm, 95%CI -0.25 to 1.57, p = 0.156) when adjusting for several confounders. In lowlanders with moderate to severe COPD, an ascent to high altitude was associated with impaired postural control and this was not prevented by acetazolamide.

Hyperbaric oxygen preconditioning for prevention of acute high-altitude diseases: Fact or fiction?

Acute high-altitude diseases, including acute mountain sickness (AMS), high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE), have been recognized as potentially lethal diseases for altitude climbers. Various preconditioning stimuli, including hyperbaric oxygen (HBO), have been proposed to prevent acute high-altitude diseases. Herein, we reviewed whether and how HBO preconditioning could affect high-altitude diseases and summarized the results of current trials. Evidence suggests that HBO preconditioning may be a safe and effective preventive method for acute high-altitude diseases. The proposed mechanisms of HBO preconditioning in preventing high-altitude diseases may involve: 1) protection of the blood-brain barrier and prevention of brain edema, 2) inhibition of the inflammatory responses, 3) induction of the hypoxia-inducible factor and its target genes, and 4) increase in antioxidant activity. However, the optimal protocol of HBO preconditioning needs further exploration. Translating the beneficial effects of HBO preconditioning into current practice requires the "conditioning strategies" approach. More large-scale and high-quality randomized controlled studies are needed in the future.

Evaluation of Myocardial Microcirculation in Rats under a High-Altitude Hypoxic Environment by Computed Tomography Myocardial Perfusion Imaging

This study aims to examine the changes in myocardial microcirculation in rats in a high-altitude hypoxic environment via computed tomography (CT) myocardial perfusion imaging technology. Rats in two groups were raised in different environments from 4 weeks of age for a period of 24 weeks. At 28 weeks of age, both groups underwent CT myocardial perfusion scanning, and the following myocardial perfusion parameters were measured: time to peak (TTP), mean transit time (MTT), blood flow (BF), and blood volume (BV). Following the scan, the rats were sacrificed, the cardiac index and right ventricular hypertrophy index were obtained, and hematoxylin-eosin (HE) staining was utilized to observe the pathological changes in the myocardium. In the group of rats that are subject to a high-altitude hypoxic environment for 24 weeks (the high-altitude group), the TTP and MTT values were increased (P < 0.05), the BF and BV values were lower (P < 0.05), the right heart mass was higher (P < 0.05) than that in the low-altitude group. As shown by the pathological results of HE staining, the gap between cardiomyocytes in the high-altitude group was widened, the arrangement of cardiomyocytes was irregular, and the cells were filled with a few fat vacuoles. The myocardial microcirculation is altered in a high-altitude hypoxic environment. In particular, the myocardium is in a state of inadequate perfusion, the BF in the myocardium slows down, and the right heart displays compensatory hypertrophy.

Clinical and biochemical indices of people with high-altitude experience linked to acute mountain sickness

BACKGROUND

Acute mountain sickness (AMS) is a major health issue for people travelling to high altitudes. This study was designed to comprehensively evaluate the changes in clinical characteristics and biochemical indices of high-altitude travelers and determine whether these changes were associated with AMS.

METHODS

A total of 14 clinical indices and 52 biochemical indices were determined in 22 subjects before and during acute high-altitude exposure. Six hours after passive ascent to 3648 m (Lhasa, China), the Lake Louise Scoring (LLS) system 2018 was used to assess AMS, which was defined as headache with a total LLS ≥3.

RESULTS

Before travelling to high altitudes, uric acid (UA), platelet distribution width (PDW), mitral peak E velocity (MVE), and ejection fraction (EF) were significantly higher in AMS-resistant individuals than in AMS-susceptible ones (all p < 0.05). A good predictive value of UA (0.817, 95% CI: 0.607-1.000) and PDW (0.844, 95% CI: 0.646-1.000) for AMS-susceptible subjects was found. With high-altitude experience, 14 subjects were diagnosed as having AMS. Compared with non-AMS, the changes in UA and number of neutrophils in AMS presented a significant difference (all p < 0.05). The high-altitude-induced changes in UA, area under the curve, specificity, and sensitivity for identifying AMS were 0.883 (95% CI: 0.738-1.000), 83.30%, and 90.00%, respectively.

CONCLUSION

Human presents a compensatory physiological and biochemical response to high-altitude travel at early phase. The UA concentration before travel and its trend with high-altitude experience exhibited good performance for identifying AMS.

Ibuprofen Increases Markers of Intestinal Barrier Injury But Suppresses Inflammation at Rest and After Exercise in Hypoxia

PURPOSE

The purpose of this study was to evaluate the effects of acute ibuprofen consumption (2 × 600-mg doses) on markers of enterocyte injury, intestinal barrier dysfunction, inflammation, and symptoms of gastrointestinal (GI) distress at rest and after exercise in hypobaric hypoxia.

METHODS

Using a randomized double-blind placebo-controlled crossover design, nine men (age, 28 ± 3 yr; weight, 75.4 ± 10.5 kg; height, 175 ± 7 cm; body fat, 12.9% ± 5%; V̇O 2 peak at 440 torr, 3.11 ± 0.65 L·min -1 ) completed a total of three visits including baseline testing and two experimental trials (placebo and ibuprofen) in a hypobaric chamber simulating an altitude of 4300 m. Preexercise and postexercise blood samples were assayed for intestinal fatty acid binding protein (I-FABP), ileal bile acid binding protein, soluble cluster of differentiation 14, lipopolysaccharide binding protein, monocyte chemoattractant protein-1, tumor necrosis factor α (TNF-α), interleukin-1β, and interleukin-10. Intestinal permeability was assessed using a dual sugar absorption test (urine lactulose-to-rhamnose ratio).

RESULTS

Resting I-FABP (906 ± 395 vs 1168 ± 581 pg·mL -1 ; P = 0.008) and soluble cluster of differentiation 14 (1512 ± 297 vs 1642 ± 313 ng·mL -1 ; P = 0.014) were elevated in the ibuprofen trial. Likewise, the urine lactulose-to-rhamnose ratio (0.217 vs 0.295; P = 0.047) and the preexercise to postexercise change in I-FABP (277 ± 308 vs 498 ± 479 pg·mL -1 ; P = 0.021) were greater in the ibuprofen trial. Participants also reported greater upper GI symptoms in the ibuprofen trial ( P = 0.031). However, monocyte chemoattractant protein-1 ( P = 0.007) and TNF-α ( P = 0.047) were lower throughout the ibuprofen trial compared with placebo (main effect of condition).

CONCLUSIONS

These data demonstrate that acute ibuprofen ingestion aggravates markers of enterocyte injury and intestinal barrier dysfunction at rest and after exercise in hypoxia. However, ibuprofen seems to suppress circulating markers of inflammation.

Transcriptome of pituitary function changes in rat model of high altitude cerebral edema

High altitude cerebral edema (HACE) is a serious subtype of acute mountain sickness (AMS). Studies have suggested that increased expression of corticotropin releasing hormone receptor 1 (CRFR1) in pituitary is related to the development of HACE, but no study has revealed the molecular landscape of pituitary function changes in this process. Rat model of HACE was established by simulating the high-altitude hypobaric hypoxia environment. Then RNA-sequencing was performed of rat pituitary gland (PG) in HACE and non-HACE groups. The function annotations, enrichment analysis, protein-protein interaction (PPI) network, chromosome location and drug repositioning of differentially expressed genes (DEGs) were explored based on the transcriptomic data. And we found pituitary secretion function was disordered in HACE, which was partly due to activated inflammation and oxidative stress. In addition, we identified potential biomarkers for early recognition of pituitary dysfunction and potential protective drugs for pituitary function in HACE.

Risk factors for acute mountain sickness in travellers to Cusco, Peru: coca leaves, obesity and sex

BACKGROUND

Acute mountain sickness (AMS) may occur after rapid ascents to altitudes >2500 m. Cusco (3350 m) in Peru is a popular destination for altitude inexperienced travellers. This study aimed at evaluating the incidence and risk factors for AMS among a cohort of foreign Spanish language students in Cusco.

METHODS

We performed a cohort study among young healthy foreign Spanish language students arriving to Cusco between 2012 and 2016. Consenting students answered an enrollment questionnaire on demographics, travel history and intended AMS preventive behaviour within 48 h of arrival. At 4-5 days after enrollment participants answered a second questionnaire about actual preventive behaviour before symptoms and the development of symptoms compatible with AMS during their first 48 h in Cusco. We used the 2018 Lake Louise Scoring System for AMS diagnosis. Participants with headache and a score ≥ 3 were considered to have AMS.

RESULTS

We enrolled 142 language students, the median age was 21 years (interquartile range 20-25) and 57% were female. Participants decreased physical activity (38%), increased fluid intake (34%), drank coca leaf tea (34%), took acetazolamide (16%) and acclimatized at a lower altitude (6%) to prevent AMS. Thirty-nine percent had AMS. In the multivariate analysis, obesity [odds ratio (OR) 14.45 (2.33-89.6)] and female sex [OR 4.32 (1.81-10.28)] were associated with increased risk of AMS. Taking acetazolamide [OR 0.13 (0.03-0.56)] was associated with decreased AMS risk. Consumption of coca leaf tea was not associated with decreased risk of AMS.

CONCLUSIONS

In our cohort, AMS affected two out of five travellers. Obesity and female sex were associated with increased risk. Drinking coca leaf tea for prevention did not decrease the risk of AMS. Acetazolamide prophylaxis was associated with decreased risk of AMS.

Phospholipid metabolites of the gut microbiota promote hypoxia-induced intestinal injury via CD1d-dependent γδ T cells

Gastrointestinal dysfunction is a common symptom of acute mountain sickness (AMS). The gut microbiota and γδ T cells play critical roles in intestinal disease. However, the mechanistic link between the microbiota and γδ T cells in hypoxia-induced intestinal injury remains unclear. Here, we show that hypoxia-induced intestinal damage was significantly alleviated after microbiota depletion with antibiotics. Hypoxia modulated gut microbiota composition by promoting antimicrobial peptides angiogenin-4 secretions. The abundance of Clostridium in the gut of mice after hypoxia significantly decreased, while the abundance of Desulfovibrio significantly increased. Furthermore, Desulfovibrio-derived phosphatidylethanolamine and phosphatidylcholine promoted γδ T cell activation. In CD1d-deficient mice, the levels of intraepithelial IL-17A and γδ T cells and intestinal damage were significantly decreased compared with those in wild-type mice under hypoxia. Mechanistically, phospholipid metabolites from Desulfovibrio are presented by intestinal epithelial CD1d to induce the proliferation of IL-17A-producing γδ T cells, which aggravates intestinal injury. Gut microbiota-derived metabolites promote hypoxia-induced intestinal injury via CD1d-dependent γδ T cells, suggesting that phospholipid metabolites and γδ T cells can be targets for AMS therapy.

Proteomic and clinical biomarkers for acute mountain sickness in a longitudinal cohort

Ascending to high-altitude by non-high-altitude natives is a well-suited model for studying acclimatization to extreme environments. Acute mountain sickness (AMS) is frequently experienced by visitors. The diagnosis of AMS mainly depends on a self-questionnaire, revealing the need for reliable biomarkers for AMS. Here, we profiled 22 AMS symptom phenotypes, 65 clinical indexes, and plasma proteomic profiles of AMS via a combination of proximity extension assay and multiple reaction monitoring of a longitudinal cohort of 53 individuals. We quantified 1069 proteins and validated 102 proteins. Via differential analysis, machine learning, and functional association analyses. We found and validated that RET played an important role in the pathogenesis of AMS. With high-accuracies (AUCs > 0.9) of XGBoost-based models, we prioritized ADAM15, PHGDH, and TRAF2 as protective, predictive, and diagnostic biomarkers, respectively. Our findings shed light on the precision medicine for AMS and the understanding of acclimatization to high-altitude environments.

Potential acute mountain sickness diagnostic, predictive, protective biomarkers are established using plasma proteomic, clinical and symptom phenotype data with machine learning approaches in a longitudinal cohort of 53 individuals.

Poor Knowledge of Acute Mountain Sickness in Latin American Medical Students

INTRODUCTION

Acute altitude exposure is a common event in Latin America that can result in mild to severe altitude illness. Medical students from some Latin American countries receive little information on this topic. Our aim was to determine the knowledge and incidence of acute mountain sickness (AMS), as well as the methods used to prevent AMS among medical students attending the Pan-American Student Meeting in Cusco, Peru, a city at high altitude (3400 m).

METHODS

We conducted a cross-sectional study on medical students attending a conference. Participants completed a questionnaire on the day of registration that collected demographic data and investigated students' knowledge of AMS, its prophylaxis, and their personal experience of symptoms.

RESULTS

A total of 840 students attended the meeting. Two hundred eighty-eight returned surveys, 51 from high altitude locations. Respondent age was 23±3 y (mean±SD), and 72% were female. Thirty-two percent had basic knowledge about symptoms of AMS. Headache was recognized as a symptom by 79%. Knowledge of AMS prophylaxis was reported by 70%. Coca leaf products and dimenhydrinate were mentioned by 30 and 16%, respectively, whereas acetazolamide was recognized by only 10% of participants. AMS incidence was 42%. Prophylactic measures were adopted by 47% of the participants in our study. Thirty-six percent used dimenhydrinate and 27% used coca tea. Less than 1% used acetazolamide as recommended.

CONCLUSIONS

We found poor knowledge of AMS and effective prophylaxis among medical students from several South American countries traveling to 3400 m.

Sex-Specific Difference in the Effect of Altitude on Sleep and Nocturnal Breathing in Young Healthy Volunteers

Importance: To date, there is no established evidence of sex-specific differences in altitude-induced sleep-disordered breathing (SDB) during polysomnography-confirmed sleep. Objective: The aim of this study was to investigate whether differences in sex play a pivotal role in incidences of SDB and acute mountain sickness (AMS) when staying overnight at high altitude. Design: This was a prospective cohort study. Setting: Participants underwent overnight polysomnography (PSG) and clinical assessment in a sleep laboratory at 500 m and two consecutive days at 3270 m. Participants: The participants comprised 28 (18 women) healthy, young, low-altitude residents with a median (interquartile range) age of 26.0 (25.0, 28.0) years. Exposures: Altitude exposure. Main outcomes and Measures: The primary outcome was altitude-induced change in the PSG-confirmed apnea−hypopnea index (AHI) at 3270 m compared to 500 m between men and women. Secondary outcomes included sex differences in other parameters related to SDB, sleep structure, AMS, psychomotor vigilance test reaction time and parameters from arterial and venous blood analyses. Results: The median (interquartile range) AHIs at 500 m and 3270 m on night 1 and on night 2 were 6.5/h (3.6, 9.1), 23.7/h (16.2, 42.5) and 15.2/h (11.8, 20.9) in men, respectively, and 2.2/h (1.0, 5.5), 8.0/h (5.3, 17.0) and 7.1/h (4.9, 11.5) in women, respectively (p < 0.05 nights 1 and 2 at 3270 m vs. 500 m in men and women). The median difference (95% CI) of altitude-induced change in AHI (3270 m night 1 compared to 500 m) between men and women was 11.2/h (1.9 to 19.6) (p < 0.05). Over the time course of 2 days at 3270 m, 9 out of 18 (50%) women and 1 out of 10 (10%) men developed AMS (p < 0.05 women versus men). Conclusions and Relevance: This prospective cohort study showed that men were more susceptible to altitude-induced SDB but that they had a lower AMS incidence when staying for 2 days at 3270 m than women. These findings indicate that sex-related prevention and intervention strategies against SDB and AMS are highly warranted. Trial Registration: This trial was registered at the Chinese Clinical Trial Registry; No. ChiCTR1800020155.

Contribution of Hypoxic Exercise Testing to Predict High-Altitude Pathology: A Systematic Review

Altitude travelers are exposed to high-altitude pathologies, which can be potentially serious. Individual susceptibility varies widely and this makes it difficult to predict who will develop these complications. The assessment of physiological adaptations to exercise performed in hypoxia has been proposed to help predict altitude sickness. The purpose of this review is to evaluate the contribution of hypoxic exercise testing, achieved in normobaric conditions, in the prediction of severe high-altitude pathology. We performed a systematic review using the databases PubMed, Science Direct and Embase in October 2021 to collect studies reporting physiological adaptations under hypoxic exercise testing and its interest in predicting high-altitude pathology. Eight studies were eligible, concerning 3558 patients with a mean age of 46.9 years old, and a simulated mean altitude reaching of 5092 m. 597 patients presented an acute mountain sickness during their altitude travels. Three different protocols of hypoxic exercise testing were used. Acute mountain sickness was defined using Hackett’s score or the Lake Louise score. Ventilatory and cardiac responses to hypoxia, desaturation in hypoxia, cerebral oxygenation, core temperature, variation in body mass index and some perceived sensations were the highlighted variables associated with acute mountain sickness. A decision algorithm based on hypoxic exercise tests was proposed by one team. Hypoxic exercise testing provides promising information to help predict altitude complications. Its interest should be confirmed by different teams.

Acetazolamide to Prevent Adverse Altitude Effects in COPD and Healthy Adults

BACKGROUND: We evaluated the efficacy of acetazolamide in preventing adverse altitude effects in patients with moderate to severe chronic obstructive pulmonary disease (COPD) and in healthy lowlanders 40 years of age or older. METHODS: Trial 1 was a randomized, double-blind, parallel-design trial in which 176 patients with COPD were treated with acetazolamide capsules (375 mg/day) or placebo, starting 24 hours before staying for 2 days at 3100 m. The mean (±SD) age of participants was 57±9 years, and 34% were women. At 760 m, COPD patients had oxygen saturation measured by pulse oximetry of 92% or greater, arterial partial pressure of carbon dioxide less than 45 mm Hg, and mean forced expiratory volume in 1 second of 63±11% of predicted. The primary outcome in trial 1 was the incidence of the composite end point of altitude-related adverse health effects (ARAHE) at 3100 m. Criteria for ARAHE included acute mountain sickness (AMS) and symptoms or findings relevant to well-being and safety, such as severe hypoxemia, requiring intervention. Trial 2 comprised 345 healthy lowlanders. Their mean age was 53±7 years, and 69% were women. The participants in trial 2 underwent the same protocol as did the patients with COPD in trial 1. The primary outcome in trial 2 was the incidence of AMS assessed at 3100 m by the Lake Louise questionnaire score (the scale of self-assessed symptoms ranges from 0 to 15 points, indicating absent to severe, with 3 or more points including headache, indicating AMS). RESULTS: In trial 1 of patients with COPD, 68 of 90 (76%) receiving placebo and 42 of 86 (49%) receiving acetazolamide experienced ARAHE (hazard ratio, 0.54; 95% confidence interval [CI], 0.37 to 0.79; P<0.001). The number needed to treat (NNT) to prevent one case of ARAHE was 4 (95% CI, 3 to 8). In trial 2 of healthy individuals, 54 of 170 (32%) receiving placebo and 38 of 175 (22%) receiving acetazolamide experienced AMS (hazard ratio, 0.48; 95% CI, 0.29 to 0.80; chi-square statistic P=0.035). The NNT to prevent one case of AMS was 10 (95% CI, 5 to 141). No serious adverse events occurred in these trials. CONCLUSIONS: Preventive treatment with acetazolamide reduced the incidence of adverse altitude effects requiring an intervention in patients with COPD and the incidence of AMS in healthy lowlanders 40 years of age or older during a high-altitude sojourn. (Funded by the Swiss National Science Foundation [Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung], Lunge Zürich, and the Swiss Lung Foundation; ClinicalTrials.gov numbers, NCT03156231 and NCT03561675.)

Application of 7.0 T ultra-high-field MRI in evaluating the structure and function of the right ventricle of the heart in rats under a chronic hypoxic environment at high altitude

Background

Long-term exposure to a high-altitude environment with low pressure and low oxygen can cause abnormalities in the structure and function of the heart, in particular the right ventricle. Monitoring the structure and function of the right ventricle is therefore essential for early diagnosis and prognosis of high-altitude heart-related diseases. In this study, 7.0 T MRI is used to detect cardiac structure and function indicators of rats in natural plateau and plain environments.

Methods

Rats in two groups were raised in different environments from 6 weeks of age for a period of 12 weeks. At 18 weeks of age both groups underwent 7.0 T cardiac magnetic resonance (CMR) scanning. Professional cardiac post-processing software was used to analyze right ventricular end-diastolic volume (RVEDV), right ventricular end-systolic volume (RVESV), right ventricular stroke volume (RVSV), right ventricular ejection fraction (RVEF), Right ventricular end-diastolic myocardial mass (RV Myo mass, diast), Right ventricular end-systolic myocardial mass (RV Myo mass, syst), tricuspid valve end-diastolic caliber (TVD), tricuspid valve end-systolic caliber (TVS), right ventricular end-systolic long-axis (RVESL) and right ventricular end-diastolic long-axis (RVEDL). Prior to the CMR scan, blood was collected from the two groups of rats for evaluation of blood indicators. After the scan, the rats were sacrificed and the myocardial tissue morphology observed under a light microscope.

Results

In the group of rats subject to chronic hypoxia at high altitude for 12 weeks (the plateau group), red blood cell (RBC) count, hemoglobin (HGB) and hematocrit (HCT) increased (P<0.05); RVEDV, RVESV, RVSV, RV Myo mass (diast), RV Myo mass (syst), TVS, RVESL, and RVEDL also increased (P<0.05). Observation of the right ventricle of rats in the plateau group using a light microscope mainly showed a slightly widened myocardial space, myocardial cell turbidity, vacuolar degeneration, myocardial interstitial edema, vascular congestion and a small amount of inflammatory cell infiltration.

Conclusions

The importance of ultra-high-field MRI for monitoring the early stages of rat heart injury has been demonstrated by studying the changes in the structure and function of the right ventricle of rats subject to chronic hypoxia at high altitude over a period of 12 weeks.

[Physiological and pathological responses to altitude]

Hypobaric hypoxia, the hallmark of a high altitude environment, has important physiological effects on both the cardiovascular and respiratory systems in order to maintain a balance between oxygen demand and supply. This dynamic of acclimatization is influenced both by the level of altitude and the speed of progression, but is also very individual with a wide spectrum of responses and sensitivities. This wide range of responses is associated with nonspecific symptoms characterising acute mountain sickness and high-altitude cerebral or pulmonary oedema. This article reviews the current knowledge about both the acclimatization processes and specific diseases of high-altitude.

Health Effects of Chronic Intermittent Hypoxia at a High Altitude among Chilean Miners: Rationale, Design, and Baseline Results of a Longitudinal Study

OBJECTIVES

This study aims to assess the health effects on mining workers of exposure to chronic intermittent hypoxia (CIH) at high- and very high-altitude mining compared with similar work at lower altitudes in Chile, and it also aims to constitute the baseline of a 5-year follow-up study.

METHODS

We designed a cross-sectional study to assess health conditions in 483 miners working at 2 levels of altitude exposure: 336 working at a very high or high altitude (HA; 247 above 3900-4400 m, and 89 at 3000-3900 m), and 147 below 2400 m. Subjects were randomly selected in two stages. First, a selection of mines from a census of mines in each altitude stratum was made. Secondly, workers with less than 2 years of employment at each of the selected mines were recruited. The main outcomes measured at the baseline were mountain sickness, sleep alterations, hypertension, body mass index, and neurocognitive functions.

RESULTS

Prevalence of acute mountain sickness (AMS) was 28.4% in the very high-altitude stratum (P = 0.0001 compared with the low stratum), and 71.7% experienced sleep disturbance (P = 0.02). The adjusted odds ratio for AMS was 9.2 (95% confidence interval: 5.2-16.3) when compared with the very high- and low-altitude groups. Motor processing speed and spatial working memory score were lower for the high-altitude group. Hypertension was lower in the highest-altitude subjects, which may be attributed to preoccupational screening even though this was not statistically significant.

CONCLUSIONS

Despite longer periods of acclimatization to CIH, subjects continue to present AMS and sleep disturbance. Compromise of executive functions was detected, including working memory at HA. Further rigorous research is warranted to understand long-term health impacts of high-altitude mining, and to provide evidence-based policy recommendations.

Acute, subacute and chronic mountain sickness

More than 100 million people ascend to high mountainous areas worldwide every year. At nonextreme altitudes (<5500m), 10-85% of these individuals are affected by acute mountain sickness, the most common disease induced by mild-moderate hypobaric hypoxia. Approximately 140 million individuals live permanently at heights of 2500-5500m, and up to 10% of them are affected by the subacute form of mountain sickness (high-altitude pulmonary hypertension) or the chronic form (Monge's disease), the latter of which is especially common in Andean ethnicities. This review presents the most relevant general concepts of these 3 clinical variants, which can be incapacitating and can result in complications and become life-threatening. Proper prevention, diagnosis, treatment and management of these conditions in a hostile environment such as high mountains are therefore essential.

HLA-G 3'UTR haplotype frequencies in highland and lowland South Native American populations

Human Leukocyte Antigen (HLA)-G participates in several biological processes, including reproduction, vascular remodeling, immune tolerance, and hypoxia response. HLA-G is a potential candidate gene for high altitude adaptation since its expression is modulated in both micro and macro environment under hypoxia and constant cellular stress. Besides the promoter region, the HLA-G 3'untranslated region (UTR) influences HLA-G expression patterns through several post-transcriptional mechanisms. Currently, the 3'UTR genetic diversity in terms of altitude adaptation of Native American populations is still unexplored, particularly at high altitude ecoregions. Here, we evaluated 288 Native Americans from 9 communities located in the Andes [highland (HL); ≥2,500 m (range = 2,838-4,433 m)] and 8 populations located in lowland (LL) regions [<2,500 m (range = 80-431 m); Amazonian tropical forest, Brazilian central plateau, and Chaco] of South America. In total, nine polymorphic sites and ten haplotypes were observed. The most frequent haplotypes (UTR-1, UTR-2, and UTR-3) accounted for ∼ 77% of haplotypes found in LL, while in the HL, the same haplotypes reach ∼ 93%. Also, a remarkable high frequency of putative ancestral UTR-5 haplotype was observed in LL (21.5%), while in HL UTR-2 reaches up to 47%. Further, UTR-2 frequency positively correlates with altitude-related variables, while a negative correlation for UTR-5 was observed. From an evolutionary perspective, we observed a tendency towards balancing selection in HL and LL populations thus suggesting that haplotypes of ancient and more derived alleles may have been co-opted for relatively recent adaptations such as those experienced by modern humans in the highland and lowland of South America. We also discuss how long-term balancing selection can be a reservoir of genetic variants that can be positively selected. Finally, our study provides some pieces of evidence that HLA-G 3'UTR haplotypes may have contributed to high altitude adaptation in the Andes.

Optic nerve sheath diameter changes at high altitude and in acute mountain sickness: meta-regression analyses

BACKGROUND/AIMS

To assess changes in optic nerve sheath diameter (ONSD) at high altitude and in acute mountain sickness (AMS).

METHODS

Cochrane Library, EMBASE, Google Scholar and PubMed were searched for articles published from their inception to 31st of July 2020. Outcome measures were mean changes of ONSD at high altitude and difference in ONSD change between subjects with and without AMS. Meta-regressions were conducted to investigate the relation of ONSD change to altitude and time spent at that altitude.

RESULTS

Eight studies with 248 participants comparing ONSD from sea level to high altitude, and five studies with 454 participants comparing subjects with or without AMS, were included. ONSD increased by 0.14 mm per 1000 m after adjustment for time (95% CI: 0.10 to 0.18; p<0.01). Restricted cubic spline regression revealed an almost linear relation between ONSD change and time within 2 days. ONSD was greater in subjects with AMS (mean difference=0.47; 95% CI: 0.14 to 0.80; p=0.01; I²=89.4%).

CONCLUSION

Our analysis shows that ONSD changes correlate with altitude and tend to increase in subjects with AMS. Small study number and high heterogeneity are the limitations of our study. Further large prospective studies are required to verify our findings.

No renal dysfunction or salt and water retention in acute mountain sickness at 4,559 m among young resting males after passive ascent

This study examined the role and function of the kidney at high altitude in relation to fluid balance and the development of acute mountain sickness (AMS), avoiding confounders that have contributed to conflicting results in previous studies. We examined 18 healthy male resting volunteers (18-40 yr) not acclimatized to high altitude while on a controlled diet for 24 h at Lausanne (altitude: 560 m) followed by a period of 44 h after reaching the Regina Margherita hut (4,559 m) by helicopter. AMS scores peaked after 20 h at 4,559 m. AMS was defined as functional Lake Louise score ≥ 2. There were no significant differences between 10 subjects with and 8 subjects without AMS for urinary flow, fluid balance, and weight change. Sodium excretion rate was lower in those with AMS after 24 h at altitude. Microalbuminuria increased at altitude but was not different between the groups. Creatinine clearance was not affected by altitude or AMS, whereas clearances of sinistrin and p-aminohippuric acid decreased slightly, somewhat more in those without AMS. Plasma concentrations of epinephrine, norepinephrine, atrial natriuretic factor, and vasopressin increased whereas renin activity, angiotensin, and aldosterone decreased at altitude. Circulating hormone concentrations did not differ between those with and without AMS. Summarizing, in healthy resting young men flown by helicopter to 4,559 m, renal function was not affected by hypoxia except for minor microalbuminuria, high altitude diuresis did not occur, and AMS was not associated with salt and water retention or renal dysfunction.NEW & NOTEWORTHY Kidney function remained essentially unaffected and acute mountain sickness (AMS) was not associated with salt and water retention in healthy young men flown to and resting at the Margherita hut (4,559 m) under strictly controlled conditions maintaining water, salt, and food intake at pre-exposure levels. Thus, renal dysfunction and fluid retention are not essential factors contributing to the pathophysiology of AMS.

Low Stroke Volume Index in Healthy Young Men Is Associated with the Incidence of Acute Mountain Sickness after an Ascent by Airplane: A Case-Control Study

Background

The aims of this study were to explore the characteristics of left ventricular (LV) functional changes in subjects with or without acute mountain sickness (AMS) and their associations with AMS incidence.

Methods

A total of 589 healthy men were enrolled and took a trip from Chengdu (500 m, above sea level (asl)) to Lhasa (3700 m, asl) by airplane. Basic characteristics, physiological data, and echocardiographic parameters were collected both at Chengdu and Lhasa, respectively. AMS was identified by the Lake Louise Questionnaire Score.

Results

The oxygen saturation (SpO₂), end-systolic volume index, end-diastolic volume index (EDVi), stroke volume index (SVi), E-wave velocity, and E/A ratio were decreased, whereas the heart rate (HR), ejection fraction, cardiac index (CI), and A-wave velocity were increased at the third day after arrival, as evaluated by an oximeter and echocardiography. However, AMS patients showed higher HR and lower EDVi, SVi, CI, E-wave velocity, and E/A ratio than AMS-free subjects. Among them, SVi, which is mainly correlated with the changes of EDVi and altered LV filling pattern, was the most valuable factor associated with AMS incidence following receiver-operator characteristic curves and linear and Poisson regression. Compared with subjects in the highest SVi tertile, subjects in the middle SVi tertile showed higher multivariable Incidence Rate Ratios (IRR) for AMS with higher incidences of mild headache and gastrointestinal symptoms, whereas subjects in the lowest SVi tertile showed even higher multivariable IRR with higher incidences of all the symptoms.

Conclusions

This relatively large-scale case-control study revealed that the reduction of SVi correlated with the altered LV filling pattern was associated with the incidence and clinical severity of 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 non-specific 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 vs. 171.3 ± 6.1 cm, P = 0.019), weight (62.0 ± 10.0 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.

Does age have an impact on acute mountain sickness? A systematic review

Acute mountain sickness (AMS) is the most common form of illness at high altitude; however, it is still unclear whether age is a protective factor or a risk factor for the development of AMS in travellers. In recent decades, the number of travellers aged 60 years or older is increasing. Thus, the care of older travellers is a long-standing issue in travel medicine. This study aims to systematically review the current state of knowledge related to the effect of old age on the risk of AMS. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used, and the following databases were consulted: PubMed/Medline, Embase, Europe PubMed Central (EuropePMC), World Health Organization Library Database (WHOLIS) and Literatura Latino-Americana e do Caribe em Ciências da Saúde (LILACS). The search yielded a total of 532 articles, of which 25 met the inclusion criteria, corresponding to 26 reports. Although the approaches, methods and quality were heterogeneous among the included studies, 12 reported a negative correlation between AMS prevalence and age, 11 detected no relationship and three papers indicated that the age of AMS subjects was significantly higher than controls. Despite these differences, old age does not seem to be a contraindication for travelling at high altitude. Thus, the presented synthesis will be useful for health professionals in travel medicine to better tailor their appropriate care for older adults who travel to destinations at high altitude.