Physiology of high-altitude acclimatization

Closed-Loop Respiratory Intervention Enhances Sleep Ventilation and Oxygen Saturation in Healthy Participants With Rapid High-Altitude Exposure

Individuals who rapidly exposed to high-altitude environments are at risk of developing acute mountain sickness, which can inhibit the respiratory center or cause upper airway obstruction, leading to sleep apnea (SA). SA reduces oxygen saturation (SPO2) during sleep, which not only impairs sleep quality but affects cognitive and memory function. Positive airway pressure ventilation helps alleviate SA, but existing devices are prone to failure at high altitudes and are unable to realize real-time intervention based on user's physiological parameters. In this paper, we propose a respiratory ventilation system which addresses the issue of equipment failure at high altitudes through the implementation of an atmospheric pressure compensation algorithm. Additionally, we have developed a closed-loop algorithm that adjusts the inhalation and exhalation pressure based on the user's SPO2 during sleep. Experimental evaluations were conducted at an altitude of 3650 m, where participants were randomly assigned to receive closed-loop respiratory intervention, bi-level positive airway pressure (Bi-PAP) ventilation, and sham stimulation on three days. Heart rate (HR), SPO2, tidal volume (VT), respiratory rate (Rf) and sleep papameters were collected, and sleep quality was assessed. Experimental results showed that participants experienced an 26.3% elevate in ventilation (p=0.004, 0.002, 0.003, respectively), an 8% increase in SPO2 (p $< $ 0.001 on three days), reduction in apnea events and an enhancement in deep sleep duration and sleep stability. These findings demonstrate that the incorporation of the closed-loop algorithm has significantly enhanced the system's effectiveness, offering a novel solution for addressing sleep apnea in high-altitude environments.

Acute mountain sickness predicts the emotional state of amateur mountaineers

Research on amateur mountaineers is scarce, and this study aims to delve into the emotional experiences of ten amateur mountaineers during their ascent using the "Befindlichkeitsskala" (BFS) and Lake Louise Acute Mountain Sickness scoring system (LLS). These subjects were exposed to altitudes of 3140 m, 4300 m, and 5276 m, respectively. We found that LLS scores were negatively correlated with positive emotions (β = -27.54, p < 0.05) and positively correlated with negative emotions (β = 21.97, p < 0.05). At an altitude of 4300 m, individuals with AMS exhibited significant differences in depression, anger, excitement, and inactivity compared to climbers without AMS. Upon returning to 3140 m after completing the climb, significant differences were observed in emotions such as happiness, calmness, anger, excitement, and depression. Throughout the three-day climb, noteworthy differences emerged in activity, happiness, calmness, inactivity, positive emotions (p < 0.01), negative emotions, and overall emotional scores (p < 0.05). Our study suggests a decline in the emotional well-being of amateur climbers with increasing altitude, highlighting AMS as a pivotal predictive factor for emotional experiences while climbing.

Mean corpuscular haemoglobin concentration (MCHC): a new biomarker for high-altitude pulmonary edema in the Ecuadorian Andes

Ascent to high altitude (> 3000 m height above sea level or m.a.s.l) exposes people to hypobaric atmospheric pressure and hypoxemia, which provokes mountain sickness and whose symptoms vary from the mild acute mountain sickness to the life-threatening, high-altitude pulmonary edema (HAPE). This study analysed the risk factors underlying HAPE in dwellers and travellers of the Ecuadorian Andes after sojourning over 3000 m height. A group of HAPE patients (N = 58) was compared to a NO HAPE group (N = 713), through demographic (ethnicity, sex, and age), red blood cell parameters (erythrocytes counts, hematocrit, median corpuscular volume, median corpuscular haemoglobin, and median corpuscular haemoglobin concentration (MCHC)), altitude (threshold: 3000 m.a.s.l.), and health status (vital signs) variables. Analysis of Deviance for Generalised Linear Model Fits (logit regression) revealed patterns of significant associations. High-altitude dwellers, particularly children and elder people, were HAPE-prone, while women were more tolerant of HAPE than men. Interestingly, HAPE prevalence was strongly related to an increment of MCH. The residence at middle altitude was inversely related to the odds of suffering HAPE. Ethnicity did not have a significant influence in HAPE susceptibility. Elevated MCHC emerges like a blood adaptation of Andean highlanders to high altitude and biomarker of HAPE risk.

Implementation of Knowledge Management in Higher Education: A Comparative Study of Private and Government Universities in India and Abroad

All academic institution contributes to the corpus of knowledge in some way. To keep expanding, the resulting information and data must be collected in a single area and shared throughout society. Knowledge developed in academic institutions is not adequately preserved or gathered, according to research. It has also been observed that the majority of the content or knowledge developed in academic institutes is unknown to the general public and is categorized as a literature review, which may be useful if proper coding is kept in the organization. The purposeful integration of humans, processes, and technology dedicated to developing, capturing, and executing an organization's creative infrastructure is known as a Knowledge Management (KM) method. Knowledge Management supports educational institutes in refining their capability to acquire and share information and knowledge, applying it to problem resolution and promoting research and continuous development. This paper advocates a holistic strategy for finding, analyzing, recording, retrieving, and distributing the whole of an administration's data properties. Databases, records, procedures, regulations and hitherto un-captured knowledge and talent in ordinary employees are samples of these properties. Higher education institutions can use KM as a tried and true approach to dealing with their problems. KM aids in the motivation of research as well as the promotion of partnerships and innovations in the future.

Unique mutations in mitochondrial DNA and associated pathways involved in high altitude pulmonary edema susceptibility in Indian lowlanders

High altitude pulmonary edema (HAPE) is a life threatening non-cardiogenic pulmonary edema that occurs in an otherwise healthy individuals travelling to altitude above 2500 m. Earlier studies have reported association of mutations in nuclear (nDNA) and mitochondrial DNA (mtDNA) with HAPE susceptibility. However, the molecular mechanisms involved in the pathobiology of HAPE have not been fully understood. The present study investigates the genetic predisposition to HAPE by analyzing the mtDNA mutations in HAPE susceptibles (n = 23) and acclimatized controls (n = 23) using next generation sequencing. Structural analysis of mutations was done using SWISS Model server and stability was determined using ΔΔG values. Meta-analysis of GSE52209 dataset was done to identify differentially expressed genes (DEGs) in HAPE susceptibles and acclimatized controls. Fourteen non-synonymous, conserved and pathogenic mutations were predicted using SIFT and PolyPhen scoring in protein coding genes, whereas six mutations in mt-tRNA genes showed association with HAPE (p ≤ 0.05). The structural analysis of these mutations revealed conformational changes in critical regions in Complexes I-V which are involved in subunit assembly and proton pumping activity. The protein-protein interaction network analysis of DEGs showed that HIF1α, EGLN2, EGLN3, PDK1, TFAM, PPARGC1α and NRF1 genes form highly interconnected cluster. Further, pathway enrichment analysis using DAVID revealed that "HIF-1 signaling", "oxidative phosphorylation" and "Metabolic pathways" had strong association with HAPE. Based on the findings it appears that the identified mtDNA mutations may be a potential risk factor in development of HAPE with the associated pathways providing mechanistic insight into the understanding of pathobiology of HAPE and sites for development of therapeutic targets.Communicated by Ramaswamy H. Sarma.

Effect of a Plateau Environment on the Oxidation State of the Heart and Liver through AMPK/p38 MAPK/Nrf2-ARE Signaling Pathways in Tibetan and DLY Pigs

This study evaluated the effect of a plateau environment on the heart and liver oxidation state of Tibetan pigs (TPs) and DLY pigs through analyzing AMPK, p38 MAPK, and Nrf2 signaling pathways. Twelve 120-day-old TPs and twelve 120-day-old DLY pigs were randomly divided into two groups in a plateau environment for three weeks. Exposed to a plateau environment, TPs exhibited a lower (p < 0.05) malondialdehyde level but higher (p < 0.05) glutathione, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and total antioxidant capacity (T-AOC) activities in the liver and heart than those observed in DLY pigs. TPs also showed higher (p < 0.05) mRNA levels of SOD and GSH-Px in the liver and heart compared with those of DLY pigs. The TPs showed higher (p < 0.05) mRNA and protein levels of AMPK and Nrf2 in the liver and heart compared with those of DLY pigs. Furthermore, TPs showed higher (p < 0.05) mRNA and protein levels of p38 MAPK in the heart and higher mRNA levels of p38 MAPK in the liver compared with those of DLY pigs under a plateau environment. In summary, TPs possess a stronger antioxidant capacity in the heart and liver than that of DLY pigs in a plateau environment through AMPK/p38 MAPK/Nrf2-ARE signaling pathways.

Elucidating the combined effect of intermittent hypoxia training and acetazolamide on hypoxia induced hematological and physiological changes

As the number of people travelling to altitude increases, the risk of life threatening medical emergencies also increases. It is important that we have effective strategies to minimize the risk of altitude illness. In this study, an attempt was made to investigate the combined effect of non-pharmacological (Intermittent hypoxia training; IHT) and pharmacological (acetazolamide; ACZ) intervention as a prophylactic strategy in order to minimize the risk of high altitude hypoxic related problems using rats as an animal model. Male Sprague Dawley rats were subjected to IHT for 4 h consecutively for 5 days at 12% FiO₂ under normobaric conditions with and without oral ACZ administration at 25 mg/kg body weight. Validation of the intervention was performed by exposing the rats to extreme hypoxia (EH) at 8% FiO₂ to further assess the effect of IHT and ACZ on hypoxic acclimatization. The principal findings of this study is that the combined effect of IHT and ACZ improves the arterial oxygenation by alterations in hemodynamics and in blood gasometry, thereby resulting into an increase in the oxygen carrying capacity of the blood with increase in SpO₂ (peripheral oxygen saturation). The present study showed that the combined effect of IHT with ACZ could be refined as a prophylactic measure for better outcomes during altitude ascent and rapid altitude acclimatization rather than IHT or ACZ alone.

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Combination of IHT with ACZ attenuates the inhibitory effect of respiratory alkalosis.

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It also minimizes pathological changes in hematology and blood gas.

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The strategy improved the oxygen carrying capacity of the blood by increasing SpO₂.

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Thus, it leads to ventilatory Acclimatization.

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The combined treatment could be refined as a prophylactic measure for altitude maladies.

Hypoxic Exercise Exacerbates Hypoxemia and Acute Mountain Sickness in Obesity: A Case Analysis

Acute mountain sickness (AMS) is a common syndrome characterized by headache, dizziness, loss of appetite, weakness, and nausea. As a major public health issue, obesity has increased in high altitude urban residents and intermittent commuters to high altitudes. The present study investigated acute hypoxic exposure and hypoxic exercise on hypoxemia severity and AMS symptoms in a physically active obese man. In this case analysis, peripheral oxygen saturation (SpO₂) was used to evaluate hypoxemia, heart rate (HR) and blood pressure (BP) were used to reflect the function of autonomic nervous system (ANS), and Lake Louise scoring (LLS) was used to assess AMS. The results showed that acute hypoxic exposure led to severe hypoxemia (SpO₂ = 72%) and tachycardia (HRrest = 97 bpm), and acute hypoxic exercise exacerbated severe hypoxemia (SpO₂ = 59%) and ANS dysfunction (HRpeak = 167 bpm, SBP/DBP = 210/97 mmHg). At the end of the 6-h acute hypoxic exposure, the case developed severe AMS (LLS = 10) symptoms of headache, gastrointestinal distress, cyanosis, vomiting, poor appetite, and fatigue. The findings of the case study suggest that high physical activity level appears did not show a reliable protective effect against severe hypoxemia, ANS dysfunction, and severe AMS symptoms in acute hypoxia exposure and hypoxia exercise.

Evaluation of Pulmonary Function Tests Among Pregnant Women of Different Trimesters in Debre Berhan Referral Hospital, Shoa, Ethiopia

Introduction

Pregnancy is characterized by a sequence of dynamic physiological changes that impact multiple organ system functions and is associated with various changes in pulmonary anatomy and physiology. Precise knowledge of the pulmonary function test parameters helps to understand and manage the course and outcome of pregnancy leading to safe delivery. It also helps to avoid misdiagnosis and unnecessary interventions. The aim of this study was to evaluate the effect of normal pregnancy on pulmonary function tests among pregnant women in Debre Berhan Referral Hospital, Ethiopia.

Methods

A total of 176 study participants (first, second, and third trimester; and control) were involved under a comparative cross-sectional study design and convenience sampling technique. Anthropometric data, oxygen saturation of arterial blood, and pulmonary function tests were measured. Data were tabulated and statistically analyzed using SPSS version 20.0 statistical software. Means of all parameters were compared using one-way ANOVA followed by Tukey’s post hoc multiple comparison test. Statistical significance was preset at a p-value of less than 0.05.

Results

Mean of FVC for the controls, first, second, and third trimesters was 2.59 ± 0.26, 2.13 ± 0.15, 1.93 ± 0.27, and 1.90 ± 0.11 liters, respectively. Except for FEV_1%, the mean values of FVC, FEV₁, PEFR, and FEF _25–75% in the pregnant group (all the three trimesters) were significantly decreased from the controls (P<0.05). Strong negative correlation was seen between SaO₂ and RR (r= −0.865; P <0.01). As the pregnancy progressed from first to the third trimester, dynamic pulmonary function tests (FVC, FEV₁, FEF_25-75%, and PEFR) were dropped and the respiratory rate increased.

Conclusion

The results had shown the tendency of obstructive pattern while pregnancy becoming advanced. We have observed also a remarkable decline of SaO₂ in pregnant women that might be counterbalanced by raised respiratory rate.

Might a high hemoglobin mass be involved in non-cardiogenic pulmonary edema? The case of the chronic maladaptation to high-altitude in the Andes

Exposure to hypoxic environments when ascending at high altitudes may cause life-threatening pulmonary edema (HAPE) due to a rapid accumulation of extracellular fluid flooding in the pulmonary alveoli. In Andeans, high-altitude adaptation occurs at the expense of being more prone to chronic mountain sickness: relative hypoventilation, excess pulmonary hypertension, and secondary polycythemia. Because HAPE prevalence is high in the Andes, we posit the hypothesis that a high hemoglobine mass may increase HAPE risk. In support of it, high intrapulmonary hypertension along with hyperviscosity produced by polycytemia may enhance sear forces and intravascular hemolysis, thus leading to increased acellular hemoglobin and the subsequent damage of the alveolar and endothelial barrier. It is proposed to investigate the relationship between the vaso-endothelial homeostasis and erythropoiesis in the maladaptation to high altitude and HAPE. This research is especially important when reentry HAPE, since rheologic properties of blood changes with rapid ascent to high altitudes.

Coping with hypoxemia: Could erythropoietin (EPO) be an adjuvant treatment of COVID-19?

A very recent epidemiological study provides preliminary evidence that living in habitats located at 2500 m above sea level (masl) might protect from the development of severe respiratory symptoms following infection with the novel SARS-CoV-2 virus. This epidemiological finding raises the question of whether physiological mechanisms underlying the acclimatization to high altitude identifies therapeutic targets for the effective treatment of severe acute respiratory syndrome pivotal to the reduction of global mortality during the COVID-19 pandemic. This article compares the symptoms of acute mountain sickness (AMS) with those of SARS-CoV-2 infection and explores overlapping patho-physiological mechanisms of the respiratory system including impaired oxygen transport, pulmonary gas exchange and brainstem circuits controlling respiration. In this context, we also discuss the potential impact of SARS-CoV-2 infection on oxygen sensing in the carotid body. Finally, since erythropoietin (EPO) is an effective prophylactic treatment for AMS, this article reviews the potential benefits of implementing FDA-approved erythropoietin-based (EPO) drug therapies to counteract a variety of acute respiratory and non-respiratory (e.g. excessive inflammation of vascular beds) symptoms of SARS-CoV-2 infection.

Efficiency of selected food ingredients on protein efficiency ratio, glycemic index and in vitro digestive properties

The human body on exposure to high-altitude, undergoes many physiological challenges. The cardiopulmonary reserves are favoured against the digestive system. Hence, the efficiency of digestion is compromised to a great extent, which leads to anorexia, hypophagia, epigastralgia, dyspepsia, nausea, and peptic ulcers. The present study was focused on in vitro digestive influence of selected food ingredients viz. cardamom, carom, cumin, coriander, fennel, fenugreek, ginger, pepper, star anise, turmeric, papaya, orange, pineapple, liquorice, valerian, and tarragon on the activities of digestive enzymes of rat pancreas, duodenum, and small intestine. In-vitro antioxidant activities of the above food ingredients were also carried out with respect to their radical scavenging activity against DPPH^·, NO^·, and ferrous reducing antioxidant power. All the studied food ingredients showed a comparative range of free radical scavenging activity. Further, pineapple has shown enhanced enzymatic activity of pancreatic amylase, trypsin and chymotrypsin among the tested samples with 432, 252, and 86%, respectively. However, all food ingredients showed inhibitory effect towards maltase activity, while the sucrose activity was enhanced in tarragon compared to control. Almost all the selected food ingredients have been observed to have low glycemic index and low protein efficiency ratio except pineapple. The results suggested that ample merit in the use of pineapple extract can be carried forward for the formulation of highly digestible foods for extreme environmental conditions.

S1P prophylaxis mitigates acute hypobaric hypoxia-induced molecular, biochemical, and metabolic disturbances: A preclinical report

Sphingosine-1-phosphate (S1P) is emerging to have hypoxic preconditioning potential in various preclinical studies. The study aims to evaluate the preclinical preconditioning efficacy of exogenously administered S1P against acute hypobaric hypoxia (HH)-induced pathological disturbances. Male Sprague Dawley rats (200 ± 20 g) were preconditioned with 1, 10, and 100 μg/kg body weight (b.w.) S1P (i.v.) for three consecutive days. On the third day, S1P preconditioned animals, along with hypoxia control animals, were exposed to HH equivalent to 7,620 m (280 mm Hg) for 6 h. Postexposure status of cardiac energy production, circulatory vasoactive mediators, pulmonary and cerebral oxidative damage, and inflammation were assessed. HH exposure led to cardiac energy deficit indicated by low ATP levels and pronounced AMPK activation levels, raised circulatory levels of brain natriuretic peptide and endothelin-1 with respect to total nitrate (NOx), redox imbalance, inflammation, and alterations in NOx levels in the pulmonary and cerebral tissues. These pathological precursors have been routinely reported to be coincident with high-altitude diseases. Preconditioning with S1P, especially 1 µg/kg b.w. dose, was seen to reverse the manifestation of these pathological disturbances. The protective efficacy could be attributed, at least in part, to enhanced activity of cardioprotective protein kinase C and activation of small GTPase Rac1, which led to further induction of hypoxia-adaptive molecular mediators: hypoxia-inducible factor (HIF)-1α and Hsp70. This is a first such report, to the best of our knowledge, elucidating the mechanism of exogenous S1P-mediated HIF-1α/Hsp70 induction. Conclusively, systemic preconditioning with 1 μg/kg b.w. S1P in rats protects against acute HH-induced pathological disturbances. © 2016 IUBMB Life 68(5):365-375, 2016.

Effect of acute exposure to moderate altitude on muscle power: hypobaric hypoxia vs. normobaric hypoxia

When ascending to a higher altitude, changes in air density and oxygen levels affect the way in which explosive actions are executed. This study was designed to compare the effects of acute exposure to real or simulated moderate hypoxia on the dynamics of the force-velocity relationship observed in bench press exercise. Twenty-eight combat sports athletes were assigned to two groups and assessed on two separate occasions: G1 (n = 17) in conditions of normoxia (N1) and hypobaric hypoxia (HH) and G2 (n = 11) in conditions of normoxia (N2) and normobaric hypoxia (NH). Individual and complete force-velocity relationships in bench press were determined on each assessment day. For each exercise repetition, we obtained the mean and peak velocity and power shown by the athletes. Maximum power (Pmax) was recorded as the highest P(mean) obtained across the complete force-velocity curve. Our findings indicate a significantly higher absolute load linked to P(max) (∼ 3%) and maximal strength (1 RM) (∼ 6%) in G1 attributable to the climb to altitude (P<0.05). We also observed a stimulating effect of natural hypoxia on P(mean) and P(peak) in the middle-high part of the curve (≥ 60 kg; P<0.01) and a 7.8% mean increase in barbell displacement velocity (P<0.001). No changes in any of the variables examined were observed in G2. According to these data, we can state that acute exposure to natural moderate altitude as opposed to simulated normobaric hypoxia leads to gains in 1 RM, movement velocity and power during the execution of a force-velocity curve in bench press.