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.

Prevalence of trace gas-oxidizing soil bacteria increases with radial distance from Polloquere hot spring within a high-elevation Andean cold desert.

High-elevation arid regions harbor microbial communities reliant on metabolic niches and flexibility to survive under biologically stressful conditions, including nutrient limitation that necessitates the utilization of atmospheric trace gases as electron donors. Geothermal springs present "oases" of microbial activity, diversity, and abundance by delivering water and substrates, including reduced gases. However, it is unknown whether these springs exhibit a gradient of effects, increasing their impact on trace gas-oxidizers in the surrounding soils. We assessed whether proximity to Polloquere, a high-altitude geothermal spring in an Andean salt flat, alters the diversity and metabolic structure of nearby soil bacterial populations compared to the surrounding cold desert. Recovered DNA and metagenomic analyses indicate that the spring represents an oasis for microbes in this challenging environment, supporting greater biomass with more diverse metabolic functions in proximal soils that declines sharply with radial distance from the spring. Despite the sharp decrease in biomass, potential rates of atmospheric hydrogen (H2) and carbon monoxide (CO) uptake increase away from the spring. Kinetic estimates suggest this activity is due to high-affinity trace gas consumption, likely as a survival strategy for energy/carbon acquisition. These results demonstrate that Polloquere regulates a gradient of diverse microbial communities and metabolisms, culminating in increased activity of trace gas-oxidizers as the influence of the spring yields to that of the regional salt flat environment. This suggests the spring holds local importance within the context of the broader salt flat and potentially represents a model ecosystem for other geothermal systems in high-altitude desert environments.

Silicone Oil Tamponade for Therapy of Primary Retinal Detachment in Patients Who Live at High Altitudes.

BACKGROUND: Uncomplicated rhegmatogenous retinal detachment (RRD) is mainly treated with vitrectomy and gas tamponade or, alternatively, scleral buckling surgery. However, gas tamponade inflates at high altitudes, causing significant complications. Silicone oil (SO) tamponade volume is unaffected by atmospheric pressure and may be used in patients who live or must undertake travel at high altitudes. PURPOSE: To determine the anatomical and functional outcomes after pars plana vitrectomy (PPV) with SO tamponade in primary uncomplicated RRD. METHODS: Twenty-eight consecutive cases of patients operated between January 2017 and December 2022 in Jules-Gonin University Eye Hospital in Lausanne were included in this retrospective study. All patients had a follow-up of at least 3 months after SO removal. RESULTS: Primary reattachment was achieved in all 28 eyes. Mean follow-up was 17.2 months (range: 3 - 51 months) after SO removal. Mean age at the time of intervention was 60 years (range: 21 - 80 years). Vision was stabilized or improved in 27 eyes (96%). One patient demonstrated a slight visual acuity decrease due to cataract formation at the last follow-up. In all patients, SO was removed 2 to 5 months after primary repair. In 14 of the 21 phakic patients, concomitant cataract surgery was performed. No surgical complications were encountered. Postoperatively, 5 (18%) patients had ocular hypertension, presumably steroid related, that was successfully controlled with topical treatment. CONCLUSION: PPV with SO injection seems to be a safe and efficient surgical approach in the treatment of primary uncomplicated RRD in patients living at high altitudes and was associated with good anatomical and functional outcome in our series. However, the need for a follow-up surgery to remove SO should be weighed in these cases.

Correlation between serum inflammatory factors and cognitive function in patients with high-altitude polycythemia: A case-control study.

The purpose of this study is to investigate the serum inflammatory factors in patients with high-altitude polycythemia (HAPC) and their correlation with cognitive function. The subjects were recruited and placed into a HAPC group and control group. Serum samples were collected, and inflammatory factors (interleukin-1beta [IL-1ß], monocyte chemoattractant protein-1 [MCP-1], and tumor necrosis factor-alpha [TNF-α]) were measured using ELISA kits. The mini-mental State Examination (MMSE) was used to assess cognitive function. According to the MMSE scores, HAPC group was further divided into normal cognitive function group (HNCF) and cognitive dysfunction group (HCDF). In comparison with the control group, the MMSE scores in the HAPC group were significantly low (P < .05), whereas the serum levels of IL-1ß, MCP-1, and TNF-α were significantly high (P < .01). Among the HAPC group (n = 60), 21 belonged to the HCDF and 39 belonged to the HNCF. Compared with the HNCF, the IL-1ß, MCP-1, and TNF-α in the HCDF were significantly increased (P < .01). The Pearson correlation analysis showed that inflammatory factors were positively correlated with hemoglobin, and negatively correlated with MMSE. Serum inflammatory cytokines IL-1, MCP-1, and TNF-α were increased in HAPC, and HAPC exhibited cognitive dysfunction. Considering chronic hypoxia environment influences the change of the red blood cell metabolic and inflammatory factor, red blood cells and inflammatory factor in plateau is likely to be affected by patients with vascular lesions, increase cognitive impairment.

Relationship between leaf vein traits of three dominant Quercus species and ecological factors in the Qinling Mountains, China.

We investigated the inter- and intra-species differences of leaf vein traits of three dominant Quercus species, Q. wutaishanica, Q. aliena var. acutiserrata, and Q. variabilis of Niubeiling (subtropical humid climate) and Taohuagou (warm temperate semi-humid climate), located in the eastern and western Qinling Mountains. The nine examined leaf vein traits included primary leaf vein width, secondary leaf vein width, mean fine vein width, primary vein density, fine vein density, vein areole diameter, areole density, 3D fine vein surface area, and fine vein volume. We further elucidated the influencing mechanisms and regulatory pathways of biotic and abiotic factors on leaf vein traits. The results showed that species identity had significant effects on eight out of nine leaf vein traits except 3D fine vein surface area, while habitat had significant effects on primary leaf vein width, secondary leaf vein width, vein areole diameter, fine vein density, and areole density. Altitude had significant effects on primary vein density, mean fine vein width, vein areole diameter, fine vein density and areole density. Habitat, tree species identity, and altitude had significantly interactive effects on primary leaf vein density, 3D fine vein surface area, and fine vein volume. There were significant differences in primary leaf vein width, mean fine vein width, areole density, 3D fine vein surface area, fine vein volume, primary vein density of Q. wutaishanica between the two studied habitats, but the differences were only found in secondary leaf vein width and areole density of Q. aliena var. acutiserrata and Q. variabilis. The examined leaf vein traits were influenced both by biotic and abiotic factors, with varying effect sizes. Among the biotic factors, petiole length, leaf length and width ratio had strong effect on leaf vein traits. Among the abiotic factors, climatic and soil factors had high effect size on vein traits, with the former being higher than the latter. Leaf vein traits were affected directly by biotic factors, but indirectly by abiotic factors (soil and climatic factors) via regulating biotic factors (leaf stoichiometry and leaf phenotypic traits).

Left ventricular strain changes at high altitude in rats: a cardiac magnetic resonance tissue tracking imaging study.

BACKGROUND: Long-term exposure to a high altitude environment with low pressure and low oxygen could cause abnormalities in the structure and function of the heart. Myocardial strain is a sensitive indicator for assessing myocardial dysfunction, monitoring myocardial strain is of great significance for the early diagnosis and treatment of high altitude heart-related diseases. This study applies cardiac magnetic resonance tissue tracking technology (CMR-TT) to evaluate the changes in left ventricular myocardial function and structure in rats in high altitude environment. METHODS: 6-week-old male rats were randomized into plateau hypoxia rats (plateau group, n = 21) as the experimental group and plain rats (plain group, n = 10) as the control group. plateau group rats were transported from Chengdu (altitude: 360 m), a city in a plateau located in southwestern China, to the Qinghai-Tibet Plateau (altitude: 3850 m), Yushu, China, and then fed for 12 weeks there, while plain group rats were fed in Chengdu(altitude: 360 m), China. Using 7.0 T cardiac magnetic resonance (CMR) to evaluate the left ventricular ejection fraction (EF), end-diastolic volume (EDV), end-systolic volume (ESV) and stroke volume (SV), as well as myocardial strain parameters including the peak global longitudinal (GLS), radial (GRS), and circumferential strain (GCS). The rats were euthanized and a myocardial biopsy was obtained after the magnetic resonance imaging scan. RESULTS: The plateau rats showed more lower left ventricular GLS and GRS (P < 0.05) than the plain rats. However, there was no statistically significant difference in left ventricular EDV, ESV, SV, EF and GCS compared to the plain rats (P > 0.05). CONCLUSIONS: After 12 weeks of exposure to high altitude low-pressure hypoxia environment, the left ventricular global strain was partially decreased and myocardium is damaged, while the whole heart ejection fraction was still preserved, the myocardial strain was more sensitive than the ejection fraction in monitoring cardiac function.

Knowledge, attitude, and practice of atrial fibrillation in high altitude areas.

Background: To investigate the knowledge, attitude, and practice (KAP) of atrial fibrillation (AF) among the general population in high-altitude areas. Methodology: A web-based cross-sectional study was conducted among the general population in high-altitude areas. Results: A total of 786 valid questionnaires were enrolled, with a mean age of 34.75 ± 14.16 years. The mean score of knowledge, attitude and practice were 8.22 ± 6.50 (possible range: 0-10), 28.90 ± 5.63 (possible range: 8-40), 34.34 ± 6.44 (possible range: 9-45), respectively. The multivariate analysis showed that knowledge scores (OR = 1.108, 95% CI = 1.075-1.142, p < 0.001), attitude scores (OR = 1.118, 95% CI = 1.081-1.156, p < 0.001), and never smoking (OR = 2.438, 95% CI = 1.426-4.167, p = 0.001) were independently associated with proactive practice. The structural equation modeling (SEM) showed direct effect of knowledge on practice (p = 0.014), and attitude on practice (p = 0.004), while no effect of knowledge on attitude (p = 0.190). Conclusion: The general population in high-altitude regions had adequate knowledge, positive attitude, and proactive practice towards AF. The SEM was suitable for explaining general population' KAP regarding AF, revealing that knowledge directly and positively affected attitude and practice.

Peso al nacer en el noroeste argentino. Comparación con una referencia nacional y un estándar internacional / Birth weight in the Northwest region of Argentina. Comparison with a national reference and an international standard

Introducción. El tamaño al nacer se encuentra sujeto a influencias genéticas y ambientales; la altura geográfica es muy influyente. El peso al nacer (PN) es el indicador más utilizado para evaluarlo; existen diferentes estándares y referencias. Debido a la variabilidad de la distribución del PN en relación con la altura en la provincia de Jujuy (Argentina), este trabajo analiza la distribución percentilar del PN para tierras altas (TA) y tierras bajas (TB) jujeñas según edad gestacional (EG) y sexo, y su comparación con una referencia nacional y el estándar internacional INTERGROWTH-21st (IG-21). Población y métodos. Se analizaron los registros de 78 524 nacidos vivos en Jujuy en el período 20092014. Utilizando el método LMS, se estimaron los percentiles 3, 10, 50, 90 y 97 de PN/EG por sexo, para TA (≥2000 msnm), TB (<2000 msnm) y el total provincial, y se compararon gráficamente con la referencia poblacional argentina de Urquía y el estándar IG-21. La significación estadística se determinó mediante la prueba de Wilcoxon. Resultados. El PN en Jujuy presentó distribución heterogénea, con diferencias estadísticamente significativas (p <0,05) entre TB y TA. Al comparar con la referencia nacional y el estándar IG-21, se observaron diferencias por altitud, principalmente en los percentiles 90 y 97 para ambas regiones, y en los percentiles 3 y 10 en TA comparados con el estándar. Conclusiones. Se observó variabilidad de la distribución del PN asociada a la altura geográfica, por lo que, para evaluar el crecimiento intrauterino, resulta fundamental incluir la EG y el contexto donde transcurre la gestación.

Introduction. Size at birth is subject to genetic and environmental influences; altitude is highly influential. Birth weight (BW) is the most widely used indicator to assess size at birth; different standards and references are available. Due to the variability in BW distribution in relation to altitude in the province of Jujuy (Argentina), the purpose of this study is to analyze the percentile distribution of BW in the highlands (HL) and the lowlands (LL) of Jujuy based on gestational age (GA) and sex and compare it with a national reference and the INTERGROWTH-21 st (IG-21) international standard. Population and methods. The records of 78 524 live births in Jujuy in the 2009­2014 period were analyzed. Using the LMS method, the 3 rd, 10 th, 50 th, 90 th, and 97 th percentiles of BW/GA by sex were estimated for the HL (≥ 2000 MASL), the LL (< 2000 MASL), and the total for Jujuy, and compared with the Argentine population reference by Urquía and the IG-21 standard using growth charts. The statistical significance was established using the Wilcoxon test. Results. BW in Jujuy showed a heterogeneous distribution, with statistically significant differences (p < 0.05) between the LL and the HL. When compared with the national reference and the IG-21 standard, differences in terms of altitude were observed, mainly in the 90 th and 97 th percentiles for both regions and the 3 rd and 10 th percentiles in the HL compared with the international standard. Conclusions. BW distribution varied in association with altitude; therefore, to assess intrauterine growth, it is critical to include GA and the environment in which the pregnancy takes place.

Treeline displacement may affect lake dissolved organic matter processing at high latitudes and altitudes.

Climate change induced shifts in treeline position, both towards higher altitudes and latitudes induce changes in soil organic matter. Eventually, soil organic matter is transported to alpine and subarctic lakes with yet unknown consequences for dissolved organic matter (DOM) diversity and processing. Here, we experimentally investigate the consequences of treeline shifts by amending subarctic and temperate alpine lake water with soil-derived DOM from above and below the treeline. We use ultra-high resolution mass spectrometry (FT-ICR MS) to track molecular DOM diversity (i.e., chemodiversity), estimate DOM decay and measure bacterial growth efficiency. In both lakes, soil-derived DOM from below the treeline increases lake DOM chemodiversity mainly through the enrichment with polyphenolic and highly unsaturated compounds. These compositional changes are associated with reductions in bulk and compound-level DOM reactivity and reduced bacterial growth efficiency. Our results suggest that treeline advancement has the potential to enrich a large number of lake ecosystems with less biodegradable DOM, affecting bacterial community function and potentially altering the biogeochemical cycling of carbon in lakes at high latitudes and altitudes.

Exposure to Non-Steady-State Oxygen Is Reflected in Changes to Arterial Blood Gas Values, Prefrontal Cortical Activity, and Systemic Cytokine Levels.

Onboard oxygen-generating systems (OBOGSs) provide increased inspired oxygen (FiO2) to mitigate the risk of neurologic injury in high altitude aviators. OBOGSs can deliver highly variable oxygen concentrations oscillating around a predetermined FiO2 set point, even when the aircraft cabin altitude is relatively stable. Steady-state exposure to 100% FiO2 evokes neurovascular vasoconstriction, diminished cerebral perfusion, and altered electroencephalographic activity. Whether non-steady-state FiO2 exposure leads to similar outcomes is unknown. This study characterized the physiologic responses to steady-state and non-steady-state FiO2 during normobaric and hypobaric environmental pressures emulating cockpit pressures within tactical aircraft. The participants received an indwelling radial arterial catheter while exposed to steady-state or non-steady-state FiO2 levels oscillating ± 15% of prescribed set points in a hypobaric chamber. Steady-state exposure to 21% FiO2 during normobaria produced arterial blood gas values within the anticipated ranges. Exposure to non-steady-state FiO2 led to PaO2 levels higher upon cessation of non-steady-state FiO2 than when measured during steady-state exposure. This pattern was consistent across all FiO2 ranges, at each barometric condition. Prefrontal cortical activation during cognitive testing was lower following exposure to non-steady-state FiO2 >50% and <100% during both normobaria and hypobaria of 494 mmHg. The serum analyte levels (IL-6, IP-10, MCP-1, MDC, IL-15, and VEGF-D) increased 48 h following the exposures. We found non-steady-state FiO2 levels >50% reduced prefrontal cortical brain activation during the cognitive challenge, consistent with an evoked pattern of neurovascular constriction and dilation.

The effect of breathing hypoxic gas (15% FIO2 ) on physiological and behavioral outcomes during simulated driving in healthy subjects.

Hypoxia is mainly caused by cardiopulmonary disease or high-altitude exposure. We used a driving simulator to investigate whether breathing hypoxic gas influences driving behaviors in healthy subjects. Fifty-two healthy subjects were recruited in this study, approved by the Science and Engineering Ethical Committee. During simulated driving experiments, driving behaviors, breathing frequency, oxygen saturation (SpO2 ), and heart rate variability (HRV) were analyzed. Each subject had four driving sessions; a 10-min practice and three 20-min randomized interventions: normoxic room air (21% FIO2 ) and medical air (21% FIO2 ) and hypoxic air (equal to 15% FIO2 ), analyzed by repeated measures ANOVA. Driving behaviors and HRV frequency domains showed no significant change. Heart rate (HR; p < 0.0001), standard deviation of the RR interval (SDRR; p = 0.03), short-term HRV (SD1; p < 0.0001), breathing rate (p = 0.01), and SpO2 (p < 0.0001) were all significantly different over the three gas interventions. Pairwise comparisons showed HR increased during hypoxic gas exposure compared to both normoxic interventions, while SDRR, SD1, breathing rate, and SpO2 were lower. Breathing hypoxic gas (15% FiO2 , equivalent to 2710 m altitude) may not have a significant impact on driving behavior in healthy subjects. Furthermore, HRV was negatively affected by hypoxic gas exposure while driving suggesting further research to investigate the impact of breathing hypoxic gas on driving performance for patients with autonomic dysfunction.

Demographic Characteristics and Low Iron Status Markers Are Associated with Hemoglobin Levels and Anemia among Children Living at High Elevation in Cusco, Peru.

Anemia is a complex condition associated with diet, chronic infections, and blood loss. Children living at high altitudes have higher absolute hemoglobin levels due to hypoxemia. However, they are exposed to repeated infections and dietary limitations. We conducted a cross-sectional study to identify factors affecting the hemoglobin concentration in children living in high-altitude rural communities in the Anta province of Peru. All children 3-16 years of age attending public schools were invited to participate. We enrolled children 3-16 years old in schools and visited their homes to collect demographic, socioeconomic, medical history, and anthropometric data. Children provided blood and stool samples for complete blood counts, iron status markers, and helminth infection testing. Among the 2,000 children enrolled, the mean age was 9.9 (±3.4) years, 1,004 (50.2%) were female, and the median residence altitude was 3,398 (interquartile range 3,35-3,497) meters. The mean hemoglobin level was 15 (±1.15) mg/dL; 320 (16%) had anemia as defined by WHO. Children with anemia were more likely to have lower serum iron levels (odds ratio [OR] 2.8 [95% CI 2.2-3.6], P <0.001) and serum transferrin saturation (OR 2.8 [95% CI 2-3.9], P <0.001). Younger age (OR 0.85 [95% CI 0.82-0.89], P <0.001), stunting (OR 0.68 [95% CI 0.59-0.79], P <0.001), education of the mother (OR 0.94 [95% CI 0.91-0.98], P <0.005), and low eosinophils (OR 0.49 [95% CI 0.26-0.9], P = 0.022) were associated with anemia. Helminth infections were not associated with anemia. Anemia among children at high altitude is multifactorial, but iron deficiency is a contributing factor. Further studies are needed to evaluate iron status and anemia in children living at high altitudes.

Microplastic pollution in high-altitude Nainital lake, Uttarakhand, India.

Microplastics (MPs) contamination has been reported in all environmental compartments, but very limited information is available at higher-altitude lakes. Nainital Lake, located at a high altitude in the Indian Himalayas, has various ecosystem services and is the major source of water for Nainital town, but the MP abundance is still unknown. This study presents the first evidence of the abundance and distribution of MP in Nainital Lake. Surface water and sediment samples were analysed from 16 different sites in and around the catchment area of Nainital Lake. The MP were observed in all the samples, and their abundance in surface water was 8.6-56.0 particles L-1 in the lake and 2.4-88.0 particles L-1 in hotspot sites. In the surface sediment, MP abundance ranged from 0.4-10.6 particles g-1, while in the hotspot sediment, the mean abundance was 0.6 ± 0.5 particles g-1. Fibers were the dominant MP, while 0.02-1 mm were the predominant size of MP particles. The results of chemical characterization showed the presence of six polymers, among which high-density polyethylene was the most abundant. The Polymer Hazard Index assessment classified the identified polymers as low-to high-risk categories, with a higher abundance of low- (polypropylene) and medium- (polyethylene)-risk polymers. Tourist activities and run-off catchments can be considered the major sources of MP, which can affect the ecosystem. Minimal concentrations of MP were observed in the tube well and drinking water, which depicts the direct risks to humans and, thus, the need for remedial measures to prevent MP contamination in drinking water. This study improves the knowledge of MP contamination in the higher-altitude freshwater lake, which can be the major pathway for the transport of MP to the rivers, and also emphasizes the need for waste management in Nainital town.

Energy Metabolism in Residents in the Low- and Moderate Altitude Regions of Central Asia with MAFLD and Type 2 Diabetes Mellitus.

The knowledge about the features of energy metabolism in MAFLD in the population living at different climatic and geographic heights is lacking. The goal of this study is to explore the biochemical parameters of blood and erythrocyte energy consumption in patients with MAFLD with and without DM2 living in the low- and moderate-altitude regions of Central Asia. Our study was carried out on patients living in low-altitude mountains: Bishkek, altitude=750-800 m; n=67 (MAFLD with DM 2: n=24; MAFLD without DM2: n=25; control: n=18), and At-Bashy District, Naryn Region, altitude=2046-2300 m; n=58 (MAFLD with DM2: n=28; MAFLD without DM2: n=18; control: n=12). Non-alcoholic fatty liver disease was diagnosed according to history, laboratory tests, liver ultrasound, and exclusion of other liver diseases. The level of liver fibrosis was determined using the FIB-4 score. Blood adenosine 5'-triphosphate (ATP) was determined using the CellTiter-Glo method. Healthy residents living in moderate altitudes have significantly higher levels of cytosolic ATP in their blood (p+≤+0.05) than residents living in low mountains. MAFLD is characterized by an increase in the level of ATP concentration in their blood. ATP concentration decreased significantly in patients with MAFLD with DM2 living in moderate-altitude in comparison to those living in low-altitude mountains. The results suggest that chronic altitude hypoxia leads to a breakdown in adaptive mechanisms of energy metabolism of ATP in patients with MAFLD with type 2 DM.

Arterial blood gas measurements are different for brachycephalic and nonbrachycephalic dogs acclimatized to an altitude of 1,535 meters.

OBJECTIVE: To define reference intervals (RIs) for arterial blood gas (aBG) measurements in healthy, nonsedated, dolichocephalic, and mesocephalic (nonbrachycephalic) dogs at approximately 1,535 m above sea level and compare these findings with healthy, nonsedated, brachycephalic dogs living at the same altitude. ANIMALS: 120 adult nonbrachycephalic dogs and 20 adult brachycephalic dogs. METHODS: Cases were prospectively enrolled from October 2021 to June 2022. Dogs were enrolled from the community or after presentation for wellness examinations or minor injuries including lacerations, nail injuries, and lameness. Physical examinations and systolic blood pressure (sBP) measurements were obtained before blood sample collection. Arterial blood was collected from the dorsal pedal artery or femoral artery. After data collection, brachycephalic dogs underwent pre- and postexercise tolerance assessments. RESULTS: The mean and RI values for arterial pH (7.442; 7.375 to 7.515), partial pressure of oxygen in arterial blood (Pao2; 78.3; 59.2 to 92.7 mm Hg), partial pressure of carbon dioxide in arterial blood (Paco2; 28.0; 21.5 to 34.4 mm Hg), saturation of arterial oxygen (Sao2; 98.4; 84.3% to 101.4%), HCO3 (18.9; 14.9 to 22.4 mmol/L), concentration of total hemoglobin (ctHb; 17.5; 13.4 to 21.1 g/dL), and sBP (133; 94 to 180 mm Hg) were established for healthy nonbrachycephalic dogs at 1,535-m altitude. All aBG measurements were statistically and clinically different from those previously reported for dogs at sea level. Brachycephalic dogs had significantly lower Pao2 and Sao2 (P = .0150 and P = .0237, respectively) and significantly higher ctHb (P = .0396) compared to nonbrachycephalic dogs acclimatized to the same altitude; the nonbrachycephalic RIs were not transferable to the brachycephalic dogs for Pao2. CLINICAL RELEVANCE: This study represents the first collation of aBG measurements for healthy nonbrachycephalic dogs acclimatized to an altitude of 1,535 m. Additionally, this study identified differences in arterial oxygenation measurements between brachycephalic and nonbrachycephalic dogs. RIs in brachycephalic dogs need to be established.

Role of neutrophil myeloperoxidase in the development and progression of high-altitude pulmonary edema.

BACKGROUND: Neutrophil infiltration and hypoxic pulmonary vasoconstriction induced by hypobaric hypoxic stress are vital in high-altitude pulmonary edema (HAPE). Myeloperoxidase (MPO), an important enzyme in neutrophils, is associated with inflammation and oxidative stress and is also involved in the regulation of nitric oxide synthase (NOS), an enzyme that catalyzes the production of the vasodilatory factor nitric oxide (NO). However, the role of neutrophil MPO in HAPE's progression is still uncertain. Therefore, we hypothesize that MPO is involved in the development of HAPE via NOS. METHODS: In Xining, China (altitude: 2260 m), C57BL/6 N wild-type and mpo-/- mice served as normoxic controls, while a hypobaric chamber simulated 7000 m altitude for hypoxia. L-NAME, a nitric oxide synthase (NOS) inhibitor to inhibit NO production, was the experimental drug, and D-NAME, without NOS inhibitory effects, was the control. After measuring pulmonary artery pressure (PAP), samples were collected and analyzed for blood neutrophils, oxidative stress, inflammation, vasoactive substances, pulmonary alveolar-capillary barrier permeability, and lung tissue morphology. RESULTS: Wild-type mice's lung injury scores, permeability, and neutrophil counts rose at 24 and 48 h of hypoxia exposure. Under hypoxia, PAP increased from 12.89 ± 1.51 mmHg under normoxia to 20.62 ± 3.33 mmHg significantly in wild-type mice and from 13.24 ± 0.79 mmHg to 16.50 ± 2.07 mmHg in mpo-/- mice. Consistent with PAP, inducible NOS activity, lung permeability, lung injury scores, oxidative stress response, and inflammation showed more significant increases in wild-type mice than in mpo-/- mice. Additionally, endothelial NOS activity and NO levels decreased more pronouncedly in wild-type mice than in mpo-/- mice. NOS inhibition during hypoxia led to more significant increases in PAP, permeability, and lung injury scores compared to the drug control group, especially in wild-type mice. CONCLUSION: MPO knockout reduces oxidative stress and inflammation to preserve alveolar-capillary barrier permeability and limits the decline in endothelial NOS activity to reduce PAP elevation during hypoxia. MPO inhibition emerges as a prospective therapeutic strategy for HAPE, offering avenues for precise interventions.

Exploring the Link between Altitude of Residence and Smoking Patterns in the United States.

INTRODUCTION: Smoking-related diseases affect 16 million Americans, causing approximately 480,000 deaths annually. The prevalence of cigarette smoking varies regionally across the United States, and previous research indicates that regional rates of smoking-related diseases demonstrate a negative association with altitude. The purpose of this study was to determine the relationship between altitude and the prevalence of cigarette smoking by county (N = 3106) in the United States. We hypothesized that smoking prevalence among adults would be negatively associated with mean county altitude. METHODS: A multivariate linear regression was performed to examine the relationship between county-level mean altitude and county smoking rate. Covariates were individually correlated with 2020 smoking data, and significant associations were included in the final model. RESULTS: The multivariate linear regression indicated that the county-level smoking rates are significantly reduced at high altitudes (p < 0.001). The model accounted for 89.5% of the variance in smoking prevalence, and for each 1000-foot increase in altitude above sea level, smoking rates decreased by 0.143%. Based on multivariate linear regression, the following variables remained independently and significantly associated: race, sex, educational attainment, socioeconomic status, unemployment, physical inactivity, drinking behavior, mental distress, and tobacco taxation. CONCLUSIONS: Our results indicate that smoking rates are negatively associated with altitude, which may suggest that altitude affects the pharmacokinetics, pharmacodynamics, and mechanistic pathways involved in cigarette use. Further research is needed to explore the relationship between altitude and smoking and how altitude may serve as a protective factor in the acquisition and maintenance of tobacco use disorders.

Differential splenic responses to hyperoxic breathing at high altitude in Sherpa and lowlanders.

The human spleen contracts in response to stress-induced catecholamine secretion, resulting in a temporary rise in haemoglobin concentration ([Hb]). Recent findings highlighted enhanced splenic response to exercise at high altitude in Sherpa, possibly due to a blunted splenic response to hypoxia. To explore the potential blunted splenic contraction in Sherpas at high altitude, we examined changes in spleen volume during hyperoxic breathing, comparing acclimatized Sherpa with acclimatized individuals of lowland ancestry. Our study included 14 non-Sherpa (7 female) residing at altitude for a mean continuous duration of 3 months and 46 Sherpa (24 female) with an average of 4 years altitude exposure. Participants underwent a hyperoxic breathing test at altitude (4300 m; barrometric pressure = âˆ¼430 torr; P O 2 ${P_{{{\mathrm{O}}_{\mathrm{2}}}}}$  = âˆ¼90 torr). Throughout the test, we measured spleen volume using ultrasonography and monitored oxygen saturation ( S p O 2 ${S_{{\mathrm{p}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ). During rest, Sherpa exhibited larger spleens (226 ± 70 mL) compared to non-Sherpa (165 ± 34 mL; P < 0.001; effect size (ES) = 0.95, 95% CI: 0.3-1.6). In response to hyperoxia, non-Sherpa demonstrated 22 ± 12% increase in spleen size (35 ± 17 mL, 95% CI: 20.7-48.9; P < 0.001; ES = 1.8, 95% CI: 0.93-2.66), while spleen size remained unchanged in Sherpa (-2 ± 13 mL, 95% CI: -2.4 to 7.3; P = 0.640; ES = 0.18, 95% CI: -0.10 to 0.47). Our findings suggest that Sherpa and non-Sherpas of lowland ancestry exhibit distinct variations in spleen volume during hyperoxia at high altitude, potentially indicating two distinct splenic functions. In Sherpa, this phenomenon may signify a diminished splenic response to altitude-related hypoxia at rest, potentially contributing to enhanced splenic contractions during physical stress. Conversely, non-Sherpa experienced a transient increase in spleen size during hyperoxia, indicating an active tonic contraction, which may influence early altitude acclimatization in lowlanders by raising [Hb].