Remote ischemic preconditioning prevents high-altitude cerebral edema by enhancing glucose metabolic reprogramming

AIMS

Incidence of acute mountain sickness (AMS) ranges from 40%-90%, with high-altitude cerebral edema (HACE) representing a life-threatening end stage of severe AMS. However, practical and convenient preventive strategies for HACE are lacking. Remote ischemic preconditioning (RIPC) has demonstrated preventive effects on ischemia- or hypoxia-induced cardiovascular and cerebrovascular diseases. This study aimed to investigate the potential molecular mechanism of HACE and the application of RIPC in preventing HACE onset.

METHODS

A hypobaric hypoxia chamber was used to simulate a high-altitude environment of 7000 meters. Metabolomics and metabolic flux analysis were employed to assay metabolite levels. Transcriptomics and quantitative real-time PCR (q-PCR) were used to investigate gene expression levels. Immunofluorescence staining was performed on neurons to label cellular proteins. The fluorescent probes Mito-Dendra2, iATPSnFR1.0, and CMTMRos were used to observe mitochondria, ATP, and membrane potential in cultured neurons, respectively. TUNEL staining was performed to detect and quantify apoptotic cell death. Hematoxylin and eosin (H&E) staining was utilized to analyze pathological changes, such as tissue swelling in cerebral cortex samples. The Rotarod test was performed to assess motor coordination and balance in rats. Oxygen-glucose deprivation (OGD) of cultured cells was employed as an in vitro model to simulate the hypoxia and hypoglycemia induced by RIPC in animal experiments.

RESULTS

We revealed a causative perturbation of glucose metabolism in the brain preceding cerebral edema. Ischemic preconditioning treatment significantly reprograms glucose metabolism, ameliorating cell apoptosis and hypoxia-induced energy deprivation. Notably, ischemic preconditioning improves mitochondrial membrane potential and ATP production through enhanced glucose-coupled mitochondrial metabolism. In vivo studies confirm that RIPC alleviates cerebral edema, reduces cell apoptosis induced by high-altitude hypoxia, and improves motor dysfunction resulting from cerebral edema.

CONCLUSIONS

Our study elucidates the metabolic basis of HACE pathogenesis. This study provides a new strategy for preventing HACE that RIPC reduces brain edema through reprogramming metabolism, highlighting the potential of targeting metabolic reprogramming for neuroprotective interventions in neurological diseases caused by ischemia or hypoxia.

Pediatric high-altitude pulmonary edema and acute mountain sickness: Clinical features and risk determinants

OBJECTIVE

This investigation aimed to delineate the clinical manifestations associated with high-altitude pulmonary edema (HAPE) and acute mountain sickness (AMS) in pediatric populations and find the risk factors of HAPE.

METHODS

We conducted a retrospective analysis of clinical data from children under 18 years diagnosed with HAPE and AMS at an average altitude of 3000 m. The clinical data between these two groups were compared.

RESULTS

The study encompassed 74 pediatric patients, 27 with AMS and 47 with HAPE. HAPE presentations included classic HAPE (55.3%), reentry HAPE (27.7%), and high-altitude resident pulmonary edema (HARPE, 17.0%). Notably, 87.2% of HAPE cases were male, and 68.1% had a high body mass index (BMI). HARPE instances followed viral infections, prominently SARS-CoV-2. HAPE cases exhibited higher BMI, respiratory tract infections within 1 week preceding symptom onset, an increase in white blood cell counts (WBCs), lower peripheral arterial oxygen saturation (SpO2), and higher heart rate compared to the AMS group. Multivariate logistic regression pinpointed high BMI as an independent HAPE risk factor (odds ratio = 19.389, 95% confidence interval: 1.069-351.759, p = .045).

CONCLUSION

HAPE occurs predominantly in males, with high BMI identified as a critical independent risk factor. The study underscores the need for heightened awareness and preventive strategies against HAPE in children at high altitudes.

A high altitude respiration and SpO2 dataset for assessing the human response to hypoxia

This report presents the Harespod dataset, an open dataset for high altitude hypoxia research, which includes respiration and SpO2 data. The dataset was collected from 15 college students aged 23-31 in a hypobaric oxygen chamber, during simulated altitude changes and induced hypoxia. Real-time physiological data, such as oxygen saturation waveforms, oxygen saturation, respiratory waveforms, heart rate, and pulse rate, were obtained at 100 Hz. Approximately 12 hours of valid data were collected from all participants. Researchers can easily identify the altitude corresponding to physiological signals based on their inherent patterns. Time markers were also recorded during altitude changes to facilitate realistic annotation of physiological signals and analysis of time-difference-of-arrival between various physiological signals for the same altitude change event. In high altitude scenarios, this dataset can be used to enhance the detection of human hypoxia states, predict respiratory waveforms, and develop related hardware devices. It will serve as a valuable and standardized resource for researchers in the field of high altitude hypoxia research, enabling comprehensive analysis and comparison.

Rehabilitation after Hypoxic and Metabolic Brain Injury in a Mountain Climber

A patient in her 50s presented with altered mental status and shortness of breath at 4600 m elevation. After descent to the base of the mountain, the patient became comatose. She was found to have bilateral pulmonary infiltrates and a serum sodium of 102 mEq/L. She was rapidly corrected to 131 mEq/L in 1 day. Initial MRI showed intensities in bilateral hippocampi, temporal cortex and insula. A repeat MRI 17 days post injury showed worsened intensities in the bilateral occipital lobes. On admission to acute rehabilitation, the patient presented with blindness, agitation, hallucinations and an inability to follow commands. Midway through her rehabilitation course, antioxidant supplementations were started with significant improvement in function. Rapid correction of hyponatraemia may cause central pontine myelinolysis or extrapontine myelinolysis (EPM). In some cases of hypoxic brain injury, delayed post-hypoxic leucoencephalopathy (DPHL) may occur. Treatment options for both disorders are generally supportive. This report represents the only documented interdisciplinary approach to treatment of a patient with DPHL and EPM. Antioxidant supplementation may be beneficial as a treatment option for both EPM and DPHL.

A Randomized Phase 2 Study to Evaluate Efficacy and Safety of AR36 for Prevention of Acute Mountain Sickness

INTRODUCTION

AR36 is a pharmaceutical-grade plant extract used to support cardiovascular health in traditional Chinese medicine. Studies suggest that AR36 may prevent acute mountain sickness (AMS) during gradual ascent to high altitude. This randomized, placebo-controlled Phase 2 trial aimed to evaluate dosing regimens and assess efficacy and safety of AR36 for AMS prevention during rapid ascent.

METHODS

Participants received placebo, low-dose AR36 (225 mg twice daily for 14 d prior and 5 d at altitude), or high-dose AR36 (12 d placebo, 300 mg twice daily for 2 d prior and 5 d at altitude). The primary efficacy outcome was 1993 Lake Louise Scoring System (LLSS) score on the morning after ascent. Safety was assessed through the proportion of treatment-emergent adverse events (TEAEs).

RESULTS

One hundred thirty-two participants were randomized. Mean±SD age was 31.4±8.6 (range, 19-54) y. Baseline characteristics did not differ across groups. Lake Louise Scoring System scores on Day 16 in the placebo, low-dose, and high-dose groups were 4.03 (2.88), 4.42 (3.17), and 3.5 (2.31), respectively (placebo versus low-dose, P=0.462; placebo versus high-dose, P=0.574; n=110). The incidence of AMS on Day 16 was 66.7% in the placebo, 61.1% in the low-dose, and 55.3% in the high-dose group (P=0.66). The proportion of TEAEs in the placebo, low-dose, and high-dose groups was 38.4% (81), 28.4% (60), and 33.2% (70), respectively (P=0.205; n=127). There was no statistical difference between groups in LLSS, incidence of AMS, or TEAEs.

CONCLUSIONS

AR36 did not improve LLSS or AMS incidence using the current regimens. AR36 was well tolerated.

High-altitude resident pulmonary edema induced by SARS-CoV-2 infection in children - A case series

From December 2022 to January 2023, seven children aged ≤14 years and residing in an area at 2999 m without altitude change in the past month developed severe cough, dyspnea, cyanosis, and severe pulmonary lesions within 2-3 days after SARS-CoV-2 infection. They were diagnosed to have high-altitude resident pulmonary edema. They completely recovered following 4-7 days of treatment with oxygen inhalation, vasodilation, diuretics, and glucocorticoids.

Insights into the pharmacodynamics and pharmacokinetics of meldonium after exposure to acute high altitude

Objective: Meldonium, a well-known cardioprotective drug, has been reported to be protective against pulmonary injury at high altitudes; however, the pharmacodynamics of meldonium in other vital organs under acute high-altitude injury are less investigated and the related pharmacokinetics have not been fully elucidated. Methods and Results: The present study examined the basic pharmacodynamics and pharmacokinetics (PK) in rat exposure to acute high-altitude hypoxia after intragastrical and intravenous pre-administration of meldonium. The results indicate that meldonium can improve acute hypoxia-induced pathological damage in brain and lung tissues, and restore blood biochemistry and routine blood index of heart, liver and kidney tissues under a simulated acute high-altitude environment. Furthermore, compared to the normoxia group, rats exposed to simulated high-altitude hypoxia and premedicated with intragastrical meldonium showed linear kinetics in the dose range of 25-100 mg/kg, with a significantly increase in the area under curve (AUC) and reduced clearance rate. No significant differences in these meldonium of PK parameters were observed with intravenous administration. Additionally, meldonium was involved in the regulation of succinic acid and 3-hydroxypropionic acid. Conclusion: These results will contribute to our understanding of the preclinical PK properties of meldonium and its acute high-altitude protective effects.

High-Altitude Pulmonary Edema in Colorado Children: A Cross-Sectional Survey and Retrospective Review

Kelly, Timothy D., Maxene Meier, Jason P. Weinman, Dunbar Ivy, John T. Brinton, and Deborah R. Liptzin. High-altitude pulmonary edema in Colorado children: a cross-sectional survey and retrospective review. High Alt Med Biol. 23:119-124, 2022. Introduction: Few studies of high-altitude pulmonary edema (HAPE) are specific to the pediatric population. The purpose of this investigation was to further characterize the radiographic patterns of pediatric HAPE, and to better understand ongoing risk following an initial pediatric HAPE episode. Methods: This study uses both a retrospective chart review and cross-sectional survey. Pediatric patients with HAPE at a single quaternary referral center in the Rocky Mountain Region were identified between the years 2013 and 2020. Patients were eligible if they presented with a clinical diagnosis of HAPE and had a viewable chest radiograph (CXR). Surveys were sent to eligible patients/families to gather additional information relating to family history, puberty, and HAPE recurrence. Results: Forty-two individuals met criteria for clinical diagnosis of HAPE with a viewable CXR. A majority of CXRs (24/42, 57.1%) demonstrated predominant right-sided involvement. Similarly, 24 CXRs (24/42, 57.1%) demonstrated predominant upper lobe involvement. Twenty-one (21/42, 50%) surveys were completed. A minority of individuals went on to experience at least one other HAPE episode (8/19, 42.1%). Conclusion: The most common radiographic pattern seen in pediatric HAPE is pulmonary edema that favors the right lung and upper lobes. After an initial HAPE presentation, some children will experience additional HAPE episodes.

Prevention and Treatment of Life-Threatening COVID-19 May Be Possible with Oxygen Treatment

Most SARS CoV-2 infections probably occur unnoticed or cause only cause a mild common cold that does not require medical intervention. A significant proportion of more severe cases is characterized by early neurological symptoms such as headache, fatigue, and impaired consciousness, including respiratory distress. These symptoms suggest hypoxia, specifically affecting the brain. The condition is best explained by primary replication of the virus in the nasal respiratory and/or the olfactory epithelia, followed by an invasion of the virus into the central nervous system, including the respiratory centers, either along a transneural route, through disruption of the blood-brain barrier, or both. In patients, presenting with early dyspnea, the primary goal of therapy should be the reversal of brain hypoxia as efficiently as possible. The first approach should be intermittent treatment with 100% oxygen using a tight oronasal mask or a hood. If this does not help within a few hours, an enclosure is needed to increase the ambient pressure. This management approach is well established in the hypoxia-related diseases in diving and aerospace medicine and preserves the patient's spontaneous breathing. Preliminary research evidence indicates that even a small elevation of the ambient pressure might be lifesaving. Other neurological symptoms, presenting particularly in long COVID-19, suggest imbalance of the autonomous nervous system, i.e., dysautonomia. These patients could benefit from vagal nerve stimulation.

Effect of high altitude on human postprandial 13 C-octanoate metabolism, intermediary metabolites, gastrointestinal peptides, and visceral perception

OBJECTIVE

At high altitude (HA), acute mountain sickness (AMS) is accompanied by neurologic and upper gastrointestinal symptoms (UGS). The primary aim of this study was to test the hypothesis that delayed gastric emptying (GE), assessed by ¹³ C-octanoate breath testing (OBT), causes UGS in AMS. The secondary aim was to assess post-gastric mechanisms of OBT, which could confound results under these conditions, by determination of intermediary metabolites, gastrointestinal peptides, and basal metabolic rate.

METHODS

A prospective trial was performed in 25 healthy participants (15 male) at 4559 m (HA) and at 490 m (Zurich). GE was assessed by OBT (428 kcal solid meal) and UGS by visual analogue scales (VAS). Blood sampling of metabolites (glucose, free fatty acids (FFA), triglycerides (TG), beta-hydroxyl butyrate (BHB), L-lactate) and gastrointestinal peptides (insulin, amylin, PYY, etc.) was performed as well as blood gas analysis and spirometry.

STATISTICAL ANALYSIS

variance analyses, bivariate correlation, and multilinear regression analysis.

RESULTS

After 24 h under hypoxic conditions at HA, participants developed AMS (p < 0.001). ¹³ CO₂ exhalation kinetics increased (p < 0.05) resulting in reduced estimates of gastric half-emptying times (p < 0.01). However, median resting respiratory quotients and plasma profiles of TG indicated that augmented beta-oxidation was the main predictor of accelerated ¹³ CO₂ -generation under these conditions.

CONCLUSION

Quantification of ¹³ C-octanoate oxidation by a breath test is sensitive to variation in metabolic (liver) function under hypoxic conditions. ¹³ C-breath testing using short-chain fatty acids is not reliable for measurement of gastric function at HA and should be considered critically in other severe hypoxic conditions, like sepsis or chronic lung disease.

Hypobaric hypoxia triggers pyroptosis in the retina via NLRP3 inflammasome activation

Hypobaric hypoxia initiates multiple impairment to the retina and is the major cause contributing to retinal function deficits such as high altitude retinopathy. However, the underlying molecular mechanism has not been clearly defined so far and remains to be clarified. In the present study, we have undertaken an approach to mimic 5000 m altitude with a low-pressure oxygen cabin and evaluated if pyroptosis is involved in the mechanisms by which hypobaric hypoxia triggers retinal impairment. We also used Radix Astragali seu Hedysari Compound (RAHC) to determine whether RAHC is capable of exerting protective effects on the hypobaric hypoxia-induced retinal dysfunction. We found that hypobaric hypoxia stress activated inflammasome complex through increasing NOD-like receptor family pyrin domain-containing 3 (NLRP3), caspase-1, and apoptosis-associated speck-like protein containing a caspase activation and recruitment domain (ASC) protein levels. The protein expression of gasdermin-D, a master executor of pyroptosis, and NADPH oxidase 4, which is regarded as a main generator of reactive oxygen species (ROS), also elevated upon hypobaric hypoxia exposure. In addition, hypobaric hypoxia induced a significant increase in pro-inflammatory cytokines expression including interleukin-1β and interleukin-18 in the rat retina. Our results indicate that hypobaric hypoxia initiates pyroptosis in the rat retina. RAHC attenuates hypobaric hypoxia-triggered retinal pyroptosis via inhibiting NLRP3 inflammasome activation and release of pro-inflammatory cytokines. The involvement of pyroptosis pathway in the retina in response to hypobaric hypoxia supports a novel insight to clarify the pathogenesis of hypobaric hypoxia-induced retinal impairment and provides a feasibility of inflammasome modulation for preserving retinal function.

Sleep, short-term memory, and mood states of volunteers with increasing altitude

PURPOSE

This study sought to identify the changes and potential association between sleep characteristics and short-term memory, and mood states among volunteers at different altitudes and times.

METHOD

A total of 26 healthy volunteers were recruited from the PLA General Hospital, and we conducted a longitudinal prospective survey for over 1 year from November 2019 to April 2021. First, we collected demographic data, sleep parameters by overnight polysomnography (PSG), short-term memory by digit span test, and mood states by completing a questionnaire with a brief profile of mood states among participants in the plain (53 m). Then, we continuously followed them up to collect data in the 3rd month at an altitude of 1,650 m (on the 3rd month of the 1-year survey period), the 3rd month at an altitude of 4,000 m (on the 6th month of the 1-year survey period), and the 9th month at an altitude of 4,000 m (on the 12th month of the 1-year survey period). Multiple linear regression analysis was used to construct models between sleep parameters and short-term memory, and mood states.

RESULTS

The prevalence of sleep apnea syndrome (SAS) significantly increased with rising elevation (P < 0.01). The apnea-hypopnea index (AHI), the mean apnea time (MAT), the longest apnea time (LAT), and the duration of time with SaO₂ < 90% (TSA90) were increased (P < 0.05), and the mean pulse oxygen saturation (MSpO₂), the lowest pulse oxygen saturation (LSpO₂), and heart rate were significantly decreased with increasing altitude (P < 0.05). Digit span scores were decreased with increasing altitude (P < 0.001). A negative mood was more severe and a positive mood increasingly faded with rising elevation (P < 0.001). Additionally, linear correlation analysis showed that higher AHI, LAT, and MAT were strongly associated with a greater decline in short-term memory (in the 3rd and 9th month at an altitude of 4,000 m, respectively: r _s = -0.897, -0.901; r _s = -0.691, -0.749; r _s = -0.732, -0.794, P < 0.001), and also were strongly associated with more severe negative mood (in the 3rd month at altitudes of 1,650 m and 4,000 m, respectively: r _s = 0.655, 0.715, 0.724; r _s = 0.771, 0.638, 0.737, P < 0.000625). Multiple linear regression pointed out that AHI was a significant predictor of negative mood among people at different altitudes (in the 3rd month at an altitude of 1,650 m: TMD = 33.161 + 6.495*AHI; in the 3rd month at an altitude of 4,000 m: TMD = 74.247 + 1.589*AHI, P < 0.05).

CONCLUSION

SAS developed easily in high altitudes, most often in CSA (central sleep apnea, CSA). The sleep, short-term memory, and negative mood were significantly more damaged with elevation in volunteers. Sleep parameters were closely associated with short-term memory and mood states in volunteers at high altitudes; the higher the sleep parameters (AHI, LAT, and MAT) scores, the more significant the mood disorders and the more obvious impairment of short-term memory. AHI was a critical predictor of the negative mood of volunteers at different altitudes. This study provides evidence that could help with the prevention and control of sleep disorder, cognitive disorder, and negative mood among populations with high altitudes.

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.

Fasting promotes acute hypoxic adaptation by suppressing mTOR-mediated pathways

Rapid adaptation to a hypoxic environment is an unanswered question that we are committed to exploring. At present, there is no suitable strategy to achieve rapid hypoxic adaptation. Here, we demonstrate that fasting preconditioning for 72 h reduces tissue injuries and maintains cardiac function, consequently significantly improving the survival rates of rats under extreme hypoxia, and this strategy can be used for rapid hypoxic adaptation. Mechanistically, fasting reduces blood glucose and further suppresses tissue mTOR activity. On the one hand, fasting-induced mTOR inhibition reduces unnecessary ATP consumption and increases ATP reserves under acute hypoxia as a result of decreased protein synthesis and lipogenesis; on the other hand, fasting-induced mTOR inhibition improves mitochondrial oxygen utilization efficiency to ensure ATP production under acute hypoxia, which is due to the significant decrease in ROS generation induced by enhanced mitophagy. Our findings highlight the important role of mTOR in acute hypoxic adaptation, and targeted regulation of mTOR could be a new strategy to improve acute hypoxic tolerance in the body.

High-altitude illnesses: Old stories and new insights into the pathophysiology, treatment and prevention

Areas at high-altitude, annually attract millions of tourists, skiers, trekkers, and climbers. If not adequately prepared and not considering certain ascent rules, a considerable proportion of those people will suffer from acute mountain sickness (AMS) or even from life-threatening high-altitude cerebral (HACE) or/and pulmonary edema (HAPE). Reduced inspired oxygen partial pressure with gain in altitude and consequently reduced oxygen availability is primarily responsible for getting sick in this setting. Appropriate acclimatization by slowly raising the hypoxic stimulus (e.g., slow ascent to high altitude) and/or repeated exposures to altitude or artificial, normobaric hypoxia will largely prevent those illnesses. Understanding physiological mechanisms of acclimatization and pathophysiological mechanisms of high-altitude diseases, knowledge of symptoms and signs, treatment and prevention strategies will largely contribute to the risk reduction and increased safety, success and enjoyment at high altitude. Thus, this review is intended to provide a sound basis for both physicians counseling high-altitude visitors and high-altitude visitors themselves.

Extravascular lung water and cardiac function assessed by echocardiography in healthy lowlanders during repeated very high-altitude exposure

BACKGROUND

High-altitude pulmonary edema is associated with elevated systolic pulmonary artery pressure (sPAP) and increased extravascular lung water (EVLW). We investigated sPAP and EVLW during repeated exposures to high altitude (HA).

METHODS

Healthy lowlanders underwent two identical 7-day HA-cycles, where subjects slept at 2900 m and spent 4-8 h daily at 5050 m, separated by a weeklong break at low altitude (LA). Echocardiography and EVLW by B-lines were measured at 520 m (baseline, LA₁), on day one, two and six at 5050 m (HA_1-3) and after descent (LA₂).

RESULTS

We included 21 subjects (median 25 years, body mass index 22 kg/m², SpO₂ 98%). SPAP rose from 21 mmHg at LA₁ to 38 mmHg at HA₁, decreased to 30 mmHg at HA₃ (both p < 0.05 vs LA₁) and normalized at 20 mmHg at LA₂ (p = ns vs LA₁). B-lines increased from 0 at LA₁ to 6 at HA₂ and 7 at HA₃ (both p < 0.05 vs LA₁) and receded to 1 at LA₂ (p = ns vs LA₁). Overall, in cycle two, sPAP did not differ (mean difference (95% confidence interval) -0.2(-2.3 to 1.9) mmHg, p = 0.864) but B-lines were more prevalent (+2.3 (1.4-3.1), p < 0.001) compared to cycle 1. Right ventricular systolic function decreased significantly but minimally at 5050 m.

CONCLUSIONS

Exposure to 5050 m induced a rapid increase in sPAP. B-lines rose during prolonged exposures to 5050 m, despite gradual decrease in sPAP, indicating excessive hydrostatic pressure might not be solely responsible for EVLW-development. Repeated HA-exposure had no acclimatization effect on EVLW. This may affect workers needing repetitive ascents to altitude and could indicate greater B-line development upon repeated exposure.

Hesperidin ameliorates hypobaric hypoxia-induced retinal impairment through activation of Nrf2/HO-1 pathway and inhibition of apoptosis

High-altitude retinopathy is initiated by hypobaric hypoxia and characterized by retinal functional changes, but the precise cellular and molecular mechanisms that mediate this dysfunction remain unclear. The aim of our investigation is to determine the protective efficacy of hesperidin (HSD) on the hypobaric hypoxia-induced damage to the retina. Experiment rats were randomly grouped as the control, hypobaric hypoxia group and HSD intervention group. The hypobaric hypoxia and the HSD intervention groups were maintained in a low-pressure oxygen cabin. We found that hypobaric hypoxia dramatically reduced nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1(HO-1) levels, induced an elevation in immunostaining of TUNEL-positive cells. Hypobaric hypoxia exposure resulted in the increase of Bcl-2, decrease of caspase3 and caspase9 expression as well as Bax level. HSD protected the retina from hypobaric hypoxia-caused impairment by enhancing Nrf2 and HO-1 activation, attenuating apoptotic caspases levels, and reducing Bax and preserving Bcl-2 expression. Additionally, oxidative stress increased poly (ADP-ribose) polymerase 1 (PARP1) and suppressed ciliary neurotrophic factor (CNTF) level, HSD treatment reverted this effect by down-regulation of PARP1 and up-regulation of CNTF expression. Taken together, our findings implicate that HSD exerts a protective role in response to hypobaric hypoxia stress by activating Nrf2/HO-1 pathway and inhibiting apoptosis.

Association between CYP2C19 gene polymorphisms and susceptibility to high-altitude pulmonary edema

INTRODUCTION

High-altitude pulmonary edema (HAPE) is caused by the interaction of both genetic and environmental risk factors.

OBJECTIVES

In this study, we aimed to explore whether three single nucleotide polymorphisms (SNPs) in CYP2C19 gene influenced the HAPE susceptibility in the Chinese Han population.

METHODS

We recruited 238 cases and 230 controls between January 2018 and October 2018 from the Affiliated Hospital of Xizang Minzu University. The relationship between CYP2C19 gene polymorphisms and HAPE was studied by association analysis. Genotyping was performed using the Agena MassARRAY platform and the statistical analysis was performed using Chi-squared test, independent sample t test, genetic model analysis and haplotype analysis.

RESULTS

The main finding of our study showed that rs4494250 in CYP2C19 gene was associated with an increased risk of HAPE at age >32 years in the log-additive model (OR = 1.80, 95% CI = 1.05-3.09, P = 0.033). Also, it was observed to be associated with a reduced risk of HAPE at age ≤2 years in the dominant model (A/G-A/A vs G/G, OR = 0.55, 95% CI = 0.31-0.97, P = 0.038) and in the log-additive model (OR = 0.58, 95% CI = 0.35-0.96, P = 0.033).

CONCLUSION

Our findings demonstrated that CYP2C19 genetic variants were associated with risk of developing HAPE in Han Chinese population.

Compound Danshen Dripping Pill Promotes Adaptation to Acute High-Altitude Exposure

Li, Zongbin, Jun Guo, Chunwei Liu, Yajun Shi, Yang Li, Jinli Wang, Dandan Li, Jing Wang, and Yundai Chen. Compound Danshen Dripping Pill promotes adaptation to acute high-altitude exposure. High Alt Med Biol. 21:258-264, 2020. Background: In this study, we aimed to investigate whether the traditional Chinese medicine, Compound Danshen Dripping Pill (CDDP), can prevent acute mountain sickness (AMS). We allocated CDDP and matching placebos to 160 volunteers before they ascended to a high altitude. Treadmill exercise tests, echocardiography, blood routine examinations, biochemical analysis, and blood gas analysis were performed upon arrival at high altitude. The primary outcome included incidence of AMS, exercise times, and metabolic equivalents (METs) of treadmill exercise tests. Second endpoints included the heart rates and rate-pressure product (RPP) before and after treadmill exercise tests. Results: After high-altitude exposure, the incidence of AMS in the CDDP group was lower than that in the placebo group (48.6% vs. 67.6%, p = 0.022). The exercise time of the treadmill exercise test was significantly longer (507 ± 77.9 seconds vs. 457 ± 90.8 seconds, p = 0.004), the heart rate was lower (pre-exercise: 91.8 ± 11.7 beats/min vs. 97.2 ± 12.7 beats/min, p = 0.016; postexercise: 114 ± 22.2 beats/min vs. 121 ± 22.6 beats/min, p = 0.019), the pre-exercise and postexercise RPP were lower (pre-exercise: 1.13 × 10⁴ ± 1.68 × 10³ mmHg·beats/min vs. 1.23 × 10⁴ ± 1.84 × 10³ mmHg·beats/min, p = 0.027; postexercise: 1.19 × 10⁴ ± 1.75 × 10³ mmHg·beats/min vs. 1.31 × 10⁴ ± 2.00 × 10³ mmHg·beats/min, p = 0.002), and the MET value of the treadmill exercise test was significantly higher (9.93 ± 1.18 METs vs. 9.31 ± 1.52 METs, p = 0.037) in the CDDP group. Discussion: CDDP decreases the incidence of AMS and enhances exercise tolerance greater than placebo after high-altitude exposure. CDDP decreases the heart rate and myocardial oxygen consumption, increases the levels of hemoglobin, hematocrit, and antioxidant factors, and decreases the levels of inflammatory factors, which may explain the roles of CDDP in improving the adaptation to high-altitude exposure.

Pulmonary Hypertension by the Method of Paul Wood

A physiological approach to the analysis of hemodynamic data in pulmonary hypertension (PH) has the advantage of reducing the large number (well over 100) of potential causal illnesses into four simple mechanisms. A fifth condition is composed of mixtures of the four basic mechanisms. This approach was beautifully described by Paul Wood, the great cardiologist whose name is given to the units of pulmonary vascular resistance (PVR), Wood units. This approach uses well understood physiological contributions to pulmonary vascular pressure. It is powerful, the major uncertainty being in determination of the magnitude of each mechanism in patients that have mixed PH of several causes. It also makes sense of the occasionally awkward clustering of conditions in the clinical classification of the World Symposium, which omits pulmonary vasoconstriction, hyperkinetic states, and the highly prevalent condition of "mixed" PH. This method of analysis is described and demonstrated, much as Wood did in his writings. The method is useful in the office, the ICU, and in consultation. A basic message from this approach is that correct assessment requires measurement of each of the three major inputs, pulmonary arterial pressure (Ppa), pulmonary artery wedge pressure (Pwedge) and cardiac output (CO). Some cases also need left ventricular end diastolic pressure (LVEDP). Other data contributing to analysis will be discussed in each condition. A key to avoiding mistakes is to always remember that PH is simply an elevation in pressure and is not inherently diagnostic of cause.

Acute Hypobaric Hypoxia-Mediated Biochemical/Metabolic Shuffling and Differential Modulation of S1PR-SphK in Cardiac and Skeletal Muscles

AIM

High altitude exposure alters biochemical, metabolic, and physiological features of heart and skeletal muscles, and hence has pathological consequences in these tissues. Central to these hypoxia-associated biochemical/metabolic shuffling are energy deficit accumulation of free radicals and ensuing oxidative damage in the tissue. Recent preclinical/clinical studies indicate sphingosine-1-phosphate (S1P) axis, comprising S1P G protein coupled receptors (S1PR_1-5) and its synthesizing enzyme-sphingosine kinase (SphK) to have key regulatory roles in homeostatic cardiac and skeletal muscle biology. In view of this, the aim of the present study was to chart the initiation and progression of biochemical/metabolic shuffling and assess the coincident differential modulation of S1PR_(1-5) expression and total SphK activity in cardiac and skeletal muscles from rats exposed to progressive hypobaric hypoxia (HH; 21,000 feet for 12, 24, and 48 hours).

RESULTS

HH-associated responses were evident as raised damage markers in plasma, oxidative stress, decreased total tissue protein, imbalance of intermediate metabolites, and aerobic/anaerobic enzyme activities in cardiac and skeletal muscles (gastrocnemius and soleus) culminating as energy deficit.

CONCLUSION

Cardiac and gastrocnemius muscles were more susceptible to hypoxic environment than soleus muscle. These differential responses were directly and indirectly coincident with temporal expression of S1PR_(1-5) and SphK activity.

Netrin-1 Dampens Hypobaric Hypoxia-Induced Lung Injury in Mice

Background: This study aimed to explore the effects of netrin-1 on hypobaric hypoxia-induced lung injury in mice. Methods: We exposed 6-8-week-old C57BL/6 mice to hypobaric stress at 340 mmHg for 30 minutes followed by 260 mmHg for different periods (6, 12, 18, and 24 hours) to observe the severity of lung injury (O₂ concentration, 21%; 54.6 mmHg). The wet/dry weight ratio and protein leakage from the mouse lung were used to determine the suitable exposure time. Netrin-1 was injected into the tail vein of mice before 18-hour decompression. Inflammatory cytokines, lung injury scores, and activity of nuclear factor κB were evaluated. The expression of apoptosis-related proteins was also examined. Results: Protein concentration in the bronchoalveolar lavage fluid was significantly higher in the 18-hour group (p < 0.05). Pulmonary pathology revealed neutrophil infiltration, alveolar septum thickening, and tissue edema. Injury score and macrophage inflammatory protein 2 levels were also increased. Intrinsic apoptosis pathway was activated. Hypoxia decreased the expression of Bcl2 protein, the number of active caspase-3-stained cells, and UNC5HB receptors. Pretreatment with netrin-1 reduced protein leakage, inhibited neutrophil migration, lowered the injury score, attenuated apoptosis, and increased UNC5HB receptor expression. Conclusion: Netrin-1 dampens hypobaric hypoxia-induced lung injury by inhibiting neutrophil migration and attenuating apoptosis.

Interventions for preventing high altitude illness: Part 3. Miscellaneous and non-pharmacological interventions

BACKGROUND

High altitude illness (HAI) is a term used to describe a group of mainly cerebral and pulmonary syndromes that can occur during travel to elevations above 2500 metres (˜ 8200 feet). Acute mountain sickness (AMS), high altitude cerebral oedema (HACE), and high altitude pulmonary oedema (HAPE) are reported as potential medical problems associated with high altitude ascent. In this, the third of a series of three reviews about preventive strategies for HAI, we assessed the effectiveness of miscellaneous and non-pharmacological interventions.

OBJECTIVES

To assess the clinical effectiveness and adverse events of miscellaneous and non-pharmacological interventions for preventing acute HAI in people who are at risk of developing high altitude illness in any setting.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, LILACS and the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP) in January 2019. We adapted the MEDLINE strategy for searching the other databases. We used a combination of thesaurus-based and free-text search terms. We scanned the reference lists and citations of included trials and any relevant systematic reviews that we identified for further references to additional trials.

SELECTION CRITERIA

We included randomized controlled trials conducted in any setting where non-pharmacological and miscellaneous interventions were employed to prevent acute HAI, including preacclimatization measures and the administration of non-pharmacological supplements. We included trials involving participants who are at risk of developing high altitude illness (AMS or HACE, or HAPE, or both). We included participants with, and without, a history of high altitude illness. We applied no age or gender restrictions. We included trials where the relevant intervention was administered before the beginning of ascent.

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures employed by Cochrane.

MAIN RESULTS

We included 20 studies (1406 participants, 21 references) in this review. Thirty studies (14 ongoing, and 16 pending classification (awaiting)) will be considered in future versions of this suite of three reviews as appropriate. We report the results for the primary outcome of this review (risk of AMS) by each group of assessed interventions.Group 1. Preacclimatization and other measures based on pressureUse of simulated altitude or remote ischaemic preconditioning (RIPC) might not improve the risk of AMS on subsequent exposure to altitude, but this effect is uncertain (simulated altitude: risk ratio (RR) 1.18, 95% confidence interval (CI) 0.82 to 1.71; I² = 0%; 3 trials, 140 participants; low-quality evidence. RIPC: RR 3.0, 95% CI 0.69 to 13.12; 1 trial, 40 participants; low-quality evidence). We found evidence of improvement of this risk using positive end-expiratory pressure (PEEP), but this information was derived from a cross-over trial with a limited number of participants (OR 3.67, 95% CI 1.38 to 9.76; 1 trial, 8 participants; low-quality evidence). We found scarcity of evidence about the risk of adverse events for these interventions.Group 2. Supplements and vitaminsSupplementation of antioxidants, medroxyprogesterone, iron or Rhodiola crenulata might not improve the risk of AMS on exposure to high altitude, but this effect is uncertain (antioxidants: RR 0.58, 95% CI 0.32 to 1.03; 1 trial, 18 participants; low-quality evidence. Medroxyprogesterone: RR 0.71, 95% CI 0.48 to 1.05; I² = 0%; 2 trials, 32 participants; low-quality evidence. Iron: RR 0.65, 95% CI 0.38 to 1.11; I² = 0%; 2 trials, 65 participants; low-quality evidence. R crenulata: RR 1.00, 95% CI 0.78 to 1.29; 1 trial, 125 participants; low-quality evidence). We found evidence of improvement of this risk with the administration of erythropoietin, but this information was extracted from a trial with issues related to risk of bias and imprecision (RR 0.41, 95% CI 0.20 to 0.84; 1 trial, 39 participants; very low-quality evidence). Regarding administration of ginkgo biloba, we did not perform a pooled estimation of RR for AMS due to considerable heterogeneity between the included studies (I² = 65%). RR estimates from the individual studies were conflicting (from 0.05 to 1.03; low-quality evidence). We found scarcity of evidence about the risk of adverse events for these interventions.Group 3. Other comparisonsWe found heterogeneous evidence regarding the risk of AMS when ginkgo biloba was compared with acetazolamide (I² = 63%). RR estimates from the individual studies were conflicting (estimations from 0.11 (95% CI 0.01 to 1.86) to 2.97 (95% CI 1.70 to 5.21); low-quality evidence). We found evidence of improvement when ginkgo biloba was administered along with acetazolamide, but this information was derived from a single trial with issues associated to risk of bias (compared to ginkgo biloba alone: RR 0.43, 95% CI 0.26 to 0.71; 1 trial, 311 participants; low-quality evidence). Administration of medroxyprogesterone plus acetazolamide did not improve the risk of AMS when compared to administration of medroxyprogesterone or acetazolamide alone (RR 1.33, 95% CI 0.50 to 3.55; 1 trial, 12 participants; low-quality evidence). We found scarcity of evidence about the risk of adverse events for these interventions.

AUTHORS' CONCLUSIONS

This Cochrane Review is the final in a series of three providing relevant information to clinicians, and other interested parties, on how to prevent high altitude illness. The assessment of non-pharmacological and miscellaneous interventions suggests that there is heterogeneous and even contradictory evidence related to the effectiveness of these prophylactic strategies. Safety of these interventions remains as an unclear issue due to lack of assessment. Overall, the evidence is limited due to its quality (low to very low), the relative paucity of that evidence and the number of studies pending classification for the three reviews belonging to this series (30 studies either awaiting classification or ongoing). Additional studies, especially those comparing with pharmacological alternatives (such as acetazolamide) are required, in order to establish or refute the strategies evaluated in this review.

Integrative plasma proteomic and microRNA analysis of Jersey cattle in response to high-altitude hypoxia

Blood has been widely collected and analyzed for diagnosing and monitoring diseases in humans and animals; a range of plasma proteins and peptide can be used as biomarkers to describe pathological or physiological status. Changes in the environment such as high-altitude hypoxia (HAH) can lead to adaptive changes in the blood system of mammals. However, the adaptation mechanism induced by HAH remains unclear. In this study, we used 12 multiparous Jersey cattle (400 ± 35 kg, average 3 yr old, dry period). We applied an iTRAQ (isobaric tags for relative and absolute quantitation) proteomics approach and microRNA (miRNA) microarray to explore differences in the plasma proteomic and miRNA profiles of Jersey cattle exposed to HAH conditions in Nyingchi, Tibet (altitude 3,000 m) and HAH-free conditions in Shenyang, China (altitude 50 m). Such quantitative proteomic strategies are suitable for accurate and comprehensive prediction of miRNA targets. In total, 264 differentially expressed proteins (127 upregulated, fold-change >1.2; 137 downregulated, fold-change <0.8) and 47 differential miRNAs (25 upregulated, fold-change >2; 22 downregulated, fold-change <0.5) were observed in the HAH-stressed group compared with the HAH-free group. Integrative analysis of proteomic and miRNA profiles demonstrated that the biological processes associated with differentially expressed proteins were immune response, complement system, and conjugation system. Integrative analysis of canonical pathways showed that most were associated with acute phase response signaling (z-score = -0.125), liver X receptor/retinoid X receptor (LXR/RXR) activation pathway (z-score = 1.134), coagulation system (z-score = -0.943), and complement system (z-score = -0.632). The current results indicated that Jersey cattle exposed to HAH could adapt to that condition through regulation of inflammatory homeostasis by inhibiting the acute phase response, coagulation system, and complement system and promoting LXR/RXR activation.

Transthoracic sonographic assessment of B-line scores during ascent to altitude among healthy trekkers

Sonographic B-lines can indicate pulmonary interstitial edema. We sought to determine the incidence of subclinical pulmonary edema measured by sonographic B-lines among lowland trekkers ascending to high altitude in the Nepal Himalaya. Twenty healthy trekkers underwent portable sonographic examinations and arterial blood draws during ascent to 5160 m over ten days. B-lines were identified in twelve participants and more frequent at 4240 m and 5160 m compared to lower altitudes (P < 0.03). There was a strong negative correlation between arterial oxygen saturation and the number of B-lines at 5160 m (ρ = -0.75, P = 0.008). Our study contributes to the growing body of literature demonstrating the development of asymptomatic pulmonary edema during ascent to high altitude. Portable lung sonography may have utility in fieldwork contexts such as trekking at altitude, but further research is needed in order to clarify its potential clinical applicability.

The Effect of an Expiratory Resistance Mask with Dead Space on Sleep, Acute Mountain Sickness, Cognition, and Ventilatory Acclimatization in Normobaric Hypoxia

We examined the hypothesis that an expiratory resistance mask containing a small amount of dead space (ER/DS) would reduce the apnea-hypopnea index (AHI) during sleep, attenuate the severity of acute mountain sickness (AMS), and offset decrements in cognitive function compared with a sham mask. In a double-blinded, randomized, sham-controlled, crossover design, 19 volunteers were exposed to two nights of normobaric hypoxia (F_IO_{2 =} 0.125), using a ER/DS mask (3.5 mm restrictive expiratory orifice; 125 mL DS volume) and sham mask (zero-flow resistance; 50 mL DS volume). Cognitive function, AMS, and ventilatory acclimatization were assessed before and after the 12-hour normobaric hypoxia exposure. Polysomnography was conducted during sleep. AHI was reduced using the ER/DS sleep mask compared with the sham (30.1 ± 23.9 events·hr^-1 vs. 58.9 ± 34.4 events·hr^-1, respectively; p = 0.01). Likewise, oxygen desaturation index and headache severity were reduced (both p < 0.05). There were also benefits on limiting the hypoxia-induced reductions in select measures of reaction speed and attention (p < 0.05). Our study indicates that a simple noninvasive and portable ER/DS mask resulted in reductions (49%) in AHI, and reduced headache severity and aspects of cognitive decline. The field applications of this ER/DS mask should be investigated before recommendations can be made to support its benefit for travel to high altitude.

Lung Ultrasound Is Accurate for the Diagnosis of High-Altitude Pulmonary Edema: A Prospective Study

Objective

The aim of this study was to assess the diagnostic accuracy of lung ultrasonography (LUS) for high-altitude pulmonary edema (HAPE).

Background

LUS has proven to be a reliable tool for the diagnosis of pulmonary diseases, including pneumonia, acute respiratory distress syndrome (ARDS), and pneumothorax. LUS also has potential for the diagnosis of HAPE. However, the actual diagnostic value of LUS for HAPE is still unknown. Our objective was to determine the feasibility of using LUS for the diagnosis of HAPE.

Materials and Methods

A prospective clinical research study of adult HAPE patients was conducted. LUS and chest X-ray (CXR) were performed in patients with suspected HAPE before and after treatment, and pulmonary moist rales were recorded concurrently. The diagnostic value of LUS, CXR, and moist rales for HAPE (i.e., their sensitivity, specificity, and positive and negative predictive values) were assessed, and the results were compared. The gold standard was the final diagnosis.

Results

In total, 148 patients were enrolled in the study, 126 of which were diagnosed with HAPE (85.14%). Before treatment, the diagnostic accuracy of LUS for HAPE was as follows: sensitivity, 98.41% (95% confidence interval (CI) 100.60-96.23%); specificity, 90.91% (95% CI 102.92-78.90%). LUS had higher sensitivity (0.98 vs. 0.81, P < 0.01 using the McNemar test) than moist rales for the diagnosis of HAPE. LUS also had higher sensitivity than CXR (0.98 vs. 0.93, P < 0.05 using the McNemar test). After treatment, LUS was consistent with CXR in 96.55% of HAPE patients, and the concordance between LUS and CXR was high (k statistic = 0.483 P ≤ 0.001; 95% CI -0.021 to -0.853).

Conclusion

The results indicate that LUS is a reliable method for the diagnosis and surveillance of HAPE. This trial is registered with Chinese Clinical Trial Registry (No. ChiCTR-DDD-16009841).

Hypobaric birth room may prevent intraventricular hemorrhage in extremely low birth weights infants

In the early postnatal period, intraventricular hemorrhage may develop in infants with extremely low birth weights due to hemodynamic instability. One of the most significant factors in intraventricular hemorrhage development is fluctuations in the cerebral blood flow due to left-to-right shunting as a result of patent ductus arteriosus, and such cases most frequently develop intraventricular hemorrhage within the first 72 h. The frequency of intraventricular hemorrhage may be reduced through the prevention of fluctuations in the cerebral blood flow in this time frame. Based on our hypothesis, we recommend that extremely low birth weight infants should be delivered and monitored in hypobaric rooms for the first three days after birth, as this may reduce left-to-right shunting as a result of patent ductus arteriosus by preventing the rapid drops seen in pulmonary pressure after birth. A more stable hemodynamic status may be achieved by increasing the cerebral blood flow during an acute term in a hypobaric environment. Gradual transition to the normobaric status at the end of the third day may prevent the long-term negative effects of hypobaric conditions.

Ginkgo biloba extract for prevention of acute mountain sickness: a systematic review and meta-analysis of randomised controlled trials

OBJECTIVE

Trials of ginkgo biloba extract (GBE) for the prevention of acute mountain sickness (AMS) have been published since 1996. Because of their conflicting results, the efficacy of GBE remains unclear. We performed a systematic review and meta-analysis to assess whether GBE prevents AMS.

METHODS

The Cochrane Library, EMBASE, Google Scholar and PubMed databases were searched for articles published up to 20 May 2017. Only randomised controlled trials were included. AMS was defined as an Environmental Symptom Questionnaire Acute Mountain Sickness-Cerebral score ≥0.7 or Lake Louise Score ≥3 with headache. The main outcome measure was the relative risk (RR) of AMS in participants receiving GBE for prophylaxis. Meta-analyses were conducted using random-effects models. Sensitivity analyses, subgroup analyses and tests for publication bias were conducted.

RESULTS

Seven study groups in six published articles met all eligibility criteria, including the article published by Leadbetter et al, where two randomised controlled trials were conducted. Overall, 451 participants were enrolled. In the primary meta-analysis of all seven study groups, GBE showed trend of AMS prophylaxis, but it is not statistically significant (RR=0.68; 95% CI 0.45 to 1.04; p=0.08). The I² statistic was 58.7% (p=0.02), indicating substantial heterogeneity. The pooled risk difference (RD) revealed a significant risk reduction in participants who use GBE (RD=-25%; 95% CI, from a reduction of 45% to 6%; p=0.011) The results of subgroup analyses of studies with low risk of bias, low starting altitude (<2500 m), number of treatment days before ascending and dosage of GBE are not statistically significant.

CONCLUSION

The currently available data suggest that although GBE may tend towards AMS prophylaxis, there are not enough data to show the statistically significant effect of GBE on preventing AMS. Further large randomised controlled studies are warranted.

Heart mechanics at high altitude: 6 days on the top of Europe

Aims

The aim of this study was to analyse the underlying mechanisms of left and right ventricular (LV and RV) functional alterations during several days in high-altitude hypoxia.

Methods and results

Resting evaluations of LV and RV function and mechanics were assessed by Speckle Tracking Echocardiography on 11 subjects at sea level (SLPRE), 3 ± 2 h after helicopter transport to high altitude (D0), at day 2 (D2), day 4 (D4) and day 6 (D6) at 4350 m and 5 ± 2 h after return to sea level (SLPOST). Subjects experienced acute mountain sickness (AMS) during the first days at 4350 m. LV systolic function, RV systolic and diastolic function, LV and RV strains and LV synchrony were unchanged at high altitude. Peak twist was increased at D0, continued to increase until D6 (SLPRE: 9.0 ± 5.1deg; D6: 13.0 ± 4.0deg, P < 0.05), but was normalized at SLPOST. Early filling decreased at high altitude with a nadir at D2 (SLPRE: 78 ± 13 cm s-1; D2: 66 ± 11 cm s-1, P < 0.05). LV filling pressures index was decreased at high altitude with the minimum value obtained at D2 and remained reduced at SLPOST. Untwisting, an important factor of LV filling, was not decreased but was delayed at 4350 m.

Conclusions

High-altitude exposure impaired LV diastolic function with the greatest effect observed at D2, concomitantly with the occurrence of AMS. The LV early filling impairments resulted from an increased RV afterload, a decrease in LV filling pressure and a delayed LV untwist. However, the increased LV twist probably acted as a compensatory mechanism to maintain cardiac performance during high-altitude hypoxia.

Interventions for treating acute high altitude illness

BACKGROUND

Acute high altitude illness is defined as a group of cerebral and pulmonary syndromes that can occur during travel to high altitudes. It is more common above 2500 metres, but can be seen at lower elevations, especially in susceptible people. Acute high altitude illness includes a wide spectrum of syndromes defined under the terms 'acute mountain sickness' (AMS), 'high altitude cerebral oedema' and 'high altitude pulmonary oedema'. There are several interventions available to treat this condition, both pharmacological and non-pharmacological; however, there is a great uncertainty regarding their benefits and harms.

OBJECTIVES

To assess the clinical effectiveness, and safety of interventions (non-pharmacological and pharmacological), as monotherapy or in any combination, for treating acute high altitude illness.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, LILACS, ISI Web of Science, CINAHL, Wanfang database and the World Health Organization International Clinical Trials Registry Platform for ongoing studies on 10 August 2017. We did not apply any language restriction.

SELECTION CRITERIA

We included randomized controlled trials evaluating the effects of pharmacological and non-pharmacological interventions for individuals suffering from acute high altitude illness: acute mountain sickness, high altitude pulmonary oedema or high altitude cerebral oedema.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the eligibility of study reports, the risk of bias for each and performed the data extraction. We resolved disagreements through discussion with a third author. We assessed the quality of evidence with GRADE.

MAIN RESULTS

We included 13 studies enrolling a total of 468 participants. We identified two ongoing studies. All studies included adults, and two studies included both teenagers and adults. The 13 studies took place in high altitude areas, mostly in the European Alps. Twelve studies included participants with acute mountain sickness, and one study included participants with high altitude pulmonary oedema. Follow-up was usually less than one day. We downgraded the quality of the evidence in most cases due to risk of bias and imprecision. We report results for the main comparisons as follows.Non-pharmacological interventions (3 studies, 124 participants)All-cause mortality and complete relief of AMS symptoms were not reported in the three included trials. One study in 64 participants found that a simulated descent of 193 millibars versus 20 millibars may reduce the average of symptoms to 2.5 vs 3.1 units after 12 hours of treatment (clinical score ranged from 0 to 11 ‒ worse; reduction of 0.6 points on average with the intervention; low quality of evidence). In addition, no complications were found with use of hyperbaric chambers versus supplementary oxygen (one study; 29 participants; low-quality evidence).Pharmacological interventions (11 trials, 375 participants)All-cause mortality was not reported in the 11 included trials. One trial found a greater proportion of participants with complete relief of AMS symptoms after 12 and 16 hours when dexamethasone was administered in comparison with placebo (47.1% versus 0%, respectively; one study; 35 participants; low quality of evidence). Likewise, when acetazolamide was compared with placebo, the effects on symptom severity was uncertain (standardized mean difference (SMD) -1.15, 95% CI -2.56 to 0.27; 2 studies, 25 participants; low-quality evidence). One trial of dexamethasone in comparison with placebo in 35 participants found a reduction in symptom severity (difference on change in the AMS score: 3.7 units reported by authors; moderate quality of evidence). The effects from two additional trials comparing gabapentin with placebo and magnesium with placebo on symptom severity at the end of treatment were uncertain. For gabapentin versus placebo: mean visual analogue scale (VAS) score of 2.92 versus 4.75, respectively; 24 participants; low quality of evidence. For magnesium versus placebo: mean scores of 9 and 10.3 units, respectively; 25 participants; low quality of evidence). The trials did not find adverse events from either treatment (low quality of evidence). One trial comparing magnesium sulphate versus placebo found that flushing was a frequent event in the magnesium sulphate arm (percentage of flushing: 75% versus 7.7%, respectively; one study; 25 participants; low quality of evidence).

AUTHORS' CONCLUSIONS

There is limited available evidence to determine the effects of non-pharmacological and pharmacological interventions in treating acute high altitude illness. Low-quality evidence suggests that dexamethasone and acetazolamide might reduce AMS score compared to placebo. However, the clinical benefits and harms related to these potential interventions remain unclear. Overall, the evidence is of limited practical significance in the clinical field. High-quality research in this field is needed, since most trials were poorly conducted and reported.

Interventions for preventing high altitude illness: Part 2. Less commonly-used drugs

BACKGROUND

High altitude illness (HAI) is a term used to describe a group of mainly cerebral and pulmonary syndromes that can occur during travel to elevations above 2500 metres (˜ 8200 feet). Acute mountain sickness (AMS), high altitude cerebral oedema (HACE) and high altitude pulmonary oedema (HAPE) are reported as potential medical problems associated with high altitude ascent. In this second review, in a series of three about preventive strategies for HAI, we assessed the effectiveness of five of the less commonly used classes of pharmacological interventions.

OBJECTIVES

To assess the clinical effectiveness and adverse events of five of the less commonly used pharmacological interventions for preventing acute HAI in participants who are at risk of developing high altitude illness in any setting.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, LILACS and the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP) in May 2017. We adapted the MEDLINE strategy for searching the other databases. We used a combination of thesaurus-based and free-text search terms. We scanned the reference lists and citations of included trials and any relevant systematic reviews that we identified for further references to additional trials.

SELECTION CRITERIA

We included randomized controlled trials conducted in any setting where one of five classes of drugs was employed to prevent acute HAI: selective 5-hydroxytryptamine(1) receptor agonists; N-methyl-D-aspartate (NMDA) antagonist; endothelin-1 antagonist; anticonvulsant drugs; and spironolactone. We included trials involving participants who are at risk of developing high altitude illness (AMS or HACE, or HAPE, or both). We included participants with and without a history of high altitude illness. We applied no age or gender restrictions. We included trials where the relevant medication was administered before the beginning of ascent. We excluded trials using these drugs during ascent or after ascent.

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures employed by Cochrane.

MAIN RESULTS

We included eight studies (334 participants, 9 references) in this review. Twelve studies are ongoing and will be considered in future versions of this review as appropriate. We have been unable to obtain full-text versions of a further 12 studies and have designated them as 'awaiting classification'. Four studies were at a low risk of bias for randomization; two at a low risk of bias for allocation concealment. Four studies were at a low risk of bias for blinding of participants and personnel. We considered three studies at a low risk of bias for blinding of outcome assessors. We considered most studies at a high risk of selective reporting bias.We report results for the following four main comparisons.Sumatriptan versus placebo (1 parallel study; 102 participants)Data on sumatriptan showed a reduction of the risk of AMS when compared with a placebo (risk ratio (RR) = 0.43, CI 95% 0.21 to 0.84; 1 study, 102 participants; low quality of evidence). The one included study did not report events of HAPE, HACE or adverse events related to administrations of sumatriptan.Magnesium citrate versus placebo (1 parallel study; 70 participants)The estimated RR for AMS, comparing magnesium citrate tablets versus placebo, was 1.09 (95% CI 0.55 to 2.13; 1 study; 70 participants; low quality of evidence). In addition, the estimated RR for loose stools was 3.25 (95% CI 1.17 to 8.99; 1 study; 70 participants; low quality of evidence). The one included study did not report events of HAPE or HACE.Spironolactone versus placebo (2 parallel studies; 205 participants)Pooled estimation of RR for AMS was not performed due to considerable heterogeneity between the included studies (I² = 72%). RR from individual studies was 0.40 (95% CI 0.12 to 1.31) and 1.44 (95% CI 0.79 to 2.01; very low quality of evidence). No events of HAPE or HACE were reported. Adverse events were not evaluated.Acetazolamide versus spironolactone (1 parallel study; 232 participants)Data on acetazolamide compared with spironolactone showed a reduction of the risk of AMS with the administration of acetazolamide (RR = 0.36, 95% CI 0.18 to 0.70; 232 participants; low quality of evidence). No events of HAPE or HACE were reported. Adverse events were not evaluated.

AUTHORS' CONCLUSIONS

This Cochrane Review is the second in a series of three providing relevant information to clinicians and other interested parties on how to prevent high altitude illness. The assessment of five of the less commonly used classes of drugs suggests that there is a scarcity of evidence related to these interventions. Clinical benefits and harms related to potential interventions such as sumatriptan are still unclear. Overall, the evidence is limited due to the low number of studies identified (for most of the comparison only one study was identified); limitations in the quality of the evidence (moderate to low); and the number of studies pending classification (24 studies awaiting classification or ongoing). We lack the large and methodologically sound studies required to establish or refute the efficacy and safety of most of the pharmacological agents evaluated in this review.

An Approach to Children with Pulmonary Edema at High Altitude

Liptzin, Deborah R., Steven H. Abman, Ann Giesenhagen, and D. Dunbar Ivy. An approach to children with pulmonary edema at high altitude. High Alt Med Biol. 19:91-98, 2018.

INTRODUCTION

Diagnosis of high-altitude illness can be more challenging in children, especially those who are preverbal. Families often travel to high elevations for family vacations, either for skiing, hiking, and/or camping. They may present to their primary care providers looking for anticipatory guidance before travel or may follow-up after developing high-altitude illness. High-altitude pulmonary edema (HAPE) can be fatal.

OBSERVATIONS

There is no indication for HAPE prophylaxis in altitude naive children. Children may develop HAPE either when traveling from low altitude to high altitude for vacation (classic HAPE), when returning to high-altitude homes after travel to low altitude (reentry HAPE), or even with a respiratory illness at high altitude without any change in elevation (high-altitude resident pulmonary edema or HARPE). Children may be more susceptible to HAPE because of increased vascular reactivity, immature control of breathing, and increased frequency of respiratory illnesses. Children with HAPE warrant evaluation for underlying cardiopulmonary abnormalities, including structural heart disease and pulmonary hypertension. Treatment of HAPE includes supplemental oxygen and descent, but underlying cardiopulmonary disease may also help guide treatment and prevention.

CONCLUSIONS AND RELEVANCE

Evaluation for structural heart disease and pulmonary hypertension should be considered in children with HAPE. Future studies should be done to elucidate the optimal strategies for prevention and treatment of HAPE and to better understand the development of HAPE in children.

STAT3-RXR-Nrf2 activates systemic redox and energy homeostasis upon steep decline in pO2 gradient

Hypobaric hypoxia elicits several patho-physiological manifestations, some of which are known to be lethal. Among various molecular mechanisms proposed so far, perturbation in redox state due to imbalance between radical generation and antioxidant defence is promising. These molecular events are also related to hypoxic status of cancer cells and therefore its understanding has extended clinical advantage beyond high altitude hypoxia. In present study, however, the focus was to understand and propose a model for rapid acclimatization of high altitude visitors to enhance their performance based on molecular changes. We considered using simulated hypobaric hypoxia at some established thresholds of high altitude stratification based on known physiological effects. Previous studies have focused on the temporal aspect while overlooking the effects of varying pO₂ levels during exposure to hypobaric hypoxia. The pO₂ levels, indicative of altitude, are crucial to redox homeostasis and can be the limiting factor during acclimatization to hypobaric hypoxia. In this study we present the effects of acute (24h) exposure to high (3049m; pO₂: 71kPa), very high (4573m; pO₂: 59kPa) and extreme altitude (7620m; pO₂: 40kPa) zones on lung and plasma using semi-quantitative redox specific transcripts and quantitative proteo-bioinformatics workflow in conjunction with redox stress assays. It was observed that direct exposure to extreme altitude caused 100% mortality, which turned into high survival rate after pre-exposure to 59kPa, for which molecular explanation were also found. The pO₂ of 59kPa (very high altitude zone) elicits systemic energy and redox homeostatic processes by modulating the STAT3-RXR-Nrf2 trio. Finally we posit the various processes downstream of STAT3-RXR-Nrf2 and the plasma proteins that can be used to ascertain the redox status of an individual.

SNPs, linkage disequilibrium, and chronic mountain sickness in Tibetan Chinese

Chronic mountain sickness (CMS) is estimated at 1.2% in Tibetans living at the Qinghai-Tibetan Plateau. Eighteen single-nucleotide polymorphisms (SNPs) from nine nuclear genes that have an association with CMS in Tibetans have been analyzed by using pairwise linkage disequilibrium (LD). The SNPs included are the angiotensin-converting enzyme (rs4340), the angiotensinogen (rs699), and the angiotensin II type 1 receptor (AGTR1) (rs5186) from the renin-angiotensin system. A low-density lipoprotein apolipoprotein B (rs693) SNP was also included. From the hypoxia-inducible factor oxygen signaling pathway, the endothetal Per-Arnt-Sim domain protein 1 (EPAS1) and the egl nine homolog 1 (ENGL1) (rs480902) SNPs were included in the study. SNPs from the vascular endothelial growth factor (VEGF) signaling pathway included are the v-akt murine thymoma viral oncogene homolog 3 (rs4590656 and rs2291409), the endothelial cell nitric oxide synthase 3 (rs1007311 and rs1799983), and the (VEGFA) (rs699947, rs34357231, rs79469752, rs13207351, rs28357093, rs1570360, rs2010963, and rs3025039). An increase in LD occurred in 40 pairwise comparisons, whereas a decrease in LD was found in 55 pairwise comparisons between the controls and CMS patients. These changes were found to occur within and between signaling pathways, which suggests that there is an interaction between SNP alleles from different areas of the genome that affect CMS.

Interventions for preventing high altitude illness: Part 1. Commonly-used classes of drugs

BACKGROUND

High altitude illness (HAI) is a term used to describe a group of cerebral and pulmonary syndromes that can occur during travel to elevations above 2500 metres (8202 feet). Acute hypoxia, acute mountain sickness (AMS), high altitude cerebral oedema (HACE) and high altitude pulmonary oedema (HAPE) are reported as potential medical problems associated with high altitude. In this review, the first in a series of three about preventive strategies for HAI, we assess the effectiveness of six of the most recommended classes of pharmacological interventions.

OBJECTIVES

To assess the clinical effectiveness and adverse events of commonly-used pharmacological interventions for preventing acute HAI.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (OVID), Embase (OVID), LILACS and trial registries in January 2017. We adapted the MEDLINE strategy for searching the other databases. We used a combination of thesaurus-based and free-text terms to search.

SELECTION CRITERIA

We included randomized-controlled and cross-over trials conducted in any setting where commonly-used classes of drugs were used to prevent acute HAI.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures as expected by Cochrane.

MAIN RESULTS

We included 64 studies (78 references) and 4547 participants in this review, and classified 12 additional studies as ongoing. A further 12 studies await classification, as we were unable to obtain the full texts. Most of the studies were conducted in high altitude mountain areas, while the rest used low pressure (hypobaric) chambers to simulate altitude exposure. Twenty-four trials provided the intervention between three and five days prior to the ascent, and 23 trials, between one and two days beforehand. Most of the included studies reached a final altitude of between 4001 and 5000 metres above sea level. Risks of bias were unclear for several domains, and a considerable number of studies did not report adverse events of the evaluated interventions. We found 26 comparisons, 15 of them comparing commonly-used drugs versus placebo. We report results for the three most important comparisons: Acetazolamide versus placebo (28 parallel studies; 2345 participants)The risk of AMS was reduced with acetazolamide (risk ratio (RR) 0.47, 95% confidence interval (CI) 0.39 to 0.56; I2 = 0%; 16 studies; 2301 participants; moderate quality of evidence). No events of HAPE were reported and only one event of HACE (RR 0.32, 95% CI 0.01 to 7.48; 6 parallel studies; 1126 participants; moderate quality of evidence). Few studies reported side effects for this comparison, and they showed an increase in the risk of paraesthesia with the intake of acetazolamide (RR 5.53, 95% CI 2.81 to 10.88, I2 = 60%; 5 studies, 789 participants; low quality of evidence). Budenoside versus placebo (2 parallel studies; 132 participants)Data on budenoside showed a reduction in the incidence of AMS compared with placebo (RR 0.37, 95% CI 0.23 to 0.61; I2 = 0%; 2 studies, 132 participants; low quality of evidence). Studies included did not report events of HAPE or HACE, and they did not find side effects (low quality of evidence). Dexamethasone versus placebo (7 parallel studies; 205 participants)For dexamethasone, the data did not show benefits at any dosage (RR 0.60, 95% CI 0.36 to 1.00; I2 = 39%; 4 trials, 176 participants; low quality of evidence). Included studies did not report events of HAPE or HACE, and we rated the evidence about adverse events as of very low quality.

AUTHORS' CONCLUSIONS

Our assessment of the most commonly-used pharmacological interventions suggests that acetazolamide is an effective pharmacological agent to prevent acute HAI in dosages of 250 to 750 mg/day. This information is based on evidence of moderate quality. Acetazolamide is associated with an increased risk of paraesthesia, although there are few reports about other adverse events from the available evidence. The clinical benefits and harms of other pharmacological interventions such as ibuprofen, budenoside and dexamethasone are unclear. Large multicentre studies are needed for most of the pharmacological agents evaluated in this review, to evaluate their effectiveness and safety.

Thin Air Resulting in High Pressure: Mountain Sickness and Hypoxia-Induced Pulmonary Hypertension

With rising altitude the partial pressure of oxygen falls. This phenomenon leads to hypobaric hypoxia at high altitude. Since more than 140 million people permanently live at heights above 2500 m and more than 35 million travel to these heights each year, understanding the mechanisms resulting in acute or chronic maladaptation of the human body to these circumstances is crucial. This review summarizes current knowledge of the body's acute response to these circumstances, possible complications and their treatment, and health care issues resulting from long-term exposure to high altitude. It furthermore describes the characteristic mechanisms of adaptation to life in hypobaric hypoxia expressed by the three major ethnic groups permanently dwelling at high altitude. We additionally summarize current knowledge regarding possible treatment options for hypoxia-induced pulmonary hypertension by reviewing in vitro, rodent, and human studies in this area of research.

Effects of Hypobaric Hypoxia on Rat Retina and Protective Response of Resveratrol to the Stress

High-altitude retinopathy represents retinal functional changes associated with environmental challenges imposed by hypobaric hypoxia, but the detailed cellular and molecular mechanism underlying this process remains unclear. Our current investigation was to explore the effect of hypobaric hypoxia on the rat retina and determine whether resveratrol has a protective efficacy on the hypoxic damage to the retina. Experiment rats were randomly grouped as the control group, hypoxia group and resveratrol intervention group. The hypoxia group and the resveratrol intervention group were maintained in a low-pressure oxygen cabin, and the resveratrol intervention group was given daily intraperitoneal injections with resveratrol. We found that hypobaric hypoxia increased thioredoxin 1 (Trx1) and thioredoxin 2 (Trx2) expression in retinas, and resveratrol treatment significantly reversed these changes (P < 0.05, P < 0.05 respectively). In comparison with controls, hypoxia upregulated the mRNA expression levels of caspase3 (P < 0.001), caspase9 (P < 0.01), heat shock protein 70 (Hsp70) (P < 0.05), heat shock protein 90 (Hsp90) (P < 0.001) and hypoxia-inducible factor-1 (HIF-1) (P < 0.05). Resveratrol administration caused a significant decrease in the gene expression of caspase3 (P< 0.001), HSP90 (P < 0.05) and HIF-1 mRNA (P < 0.01) as well as an increase in HSP70 mRNA when compared with the hypoxia group. These findings indicated that resveratrol exerted an anti-oxidative role by modulating hypoxia stress- associated genes and an anti-apoptosis role by regulating apoptosis-related cytokines. In conclusion, hypobaric hypoxia may have a pathological impact on rat retinas. The intervention of resveratrol reverses the effect induced by hypobaric hypoxia and elicits a protective response to the stress.

Diffuse alveolar hemorrhage from systemic lupus erythematosus misdiagnosed as high altitude pulmonary edema

A 26-year-old woman presented with dyspnea and dry cough soon after arriving on the Qinghai-Tibet Plateau (3650 m). Chest radiograph showed diffuse patchy infiltrates. The initial diagnosis was high altitude pulmonary edema (HAPE). However, the patient had no sputum or moist rales, and supplemental oxygen and intravenous aminophylline produced no improvement. Chest HRCT revealed symmetric and diffuse ground glass opacities. Further examination found anemia, leukopenia, urine abnormalities, and increased erythrocyte sedimentation rate. Antibodies for ds-DNA and ANA were positive. Hemoptysis and arthralgia developed after a few days. Finally the patient was diagnosed with diffuse alveolar hemorrhage secondary to systemic lupus erythemetosus.

CONCLUSION

When considering a diagnosis of HAPE, careful attention to physical signs, and a clinical course that is atypical for HAPE should prompt evaluation for other disease processes; HRCT can be useful in this setting.

Is Smoking a Predictor for Acute Mountain Sickness? Findings From a Meta-Analysis

AIM

Studies of the potential association between cigarette smoking and acute mountain sickness (AMS) have reached contradictory conclusions. Our aim was to perform a meta-analysis of studies across a range of populations to ascertain better the true relationship between cigarette smoking and AMS.

MATERIALS AND METHODS

We used the PRISMA protocol to identify and screen eligible studies of smoking and AMS. Databases including Pubmed and Google Scholar were searched, using the terms "smoking" and "acute mountain sickness." We conducted a meta-analysis of the selected studies in order to evaluate causal inference, evaluate potential biases, and investigate possible sources of heterogeneity across studies.

RESULTS

We identified 3907 publications, of which 29 were eligible for inclusion by reporting smoking status and AMS. Of these, eight publications were excluded because they were duplicative or were lacking quantitative data. The 21 studies analyzed included 16 566 subjects. These fell into two groups: occupational/military (n = 8) or volunteers/trekkers/mixed (n = 13). Study heterogeneity was high (X (2) = 55.5, P < .001). Smoking was not statistically associated with increased risk of AMS: pooled OR = 0.88 (95% CI = 0.74-1.05). Stratification yielded similar risk estimates among the occupational/military studies versus all others and studies at relatively higher and lower altitudes.

CONCLUSIONS

Overall, smoking was not statistically significantly associated with AMS: there is no consistent effect of cigarette smoking acting as either a protective factor against or a risk factor for AMS.

IMPLICATIONS

This is the first quantitative assessment of published studies on smoking and AMS, which shows smoking to be neither a risk, nor protective. Studies specifically focusing on smoking as a risk factor, should guide further research on this issue. Although all smokers should be strongly advised to quit, studies on risk factors for AMS focusing on other exposures could shed light on the full range of risks for AMS.

Wilderness Medical Society practice guidelines for the prevention and treatment of acute altitude illness: 2014 update

To provide guidance to clinicians about best practices, the Wilderness Medical Society convened an expert panel to develop evidence-based guidelines for prevention and treatment of acute mountain sickness, high altitude cerebral edema, and high altitude pulmonary edema. These guidelines present the main prophylactic and therapeutic modalities for each disorder and provide recommendations about their role in disease management. Recommendations are graded based on the quality of supporting evidence and 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 to prevention and management of each disorder that incorporate these recommendations. 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 2010;21(2):146-155.

Secundum atrial septal defect in adults: a practical review and recent developments

Secundum atrial septal defect (ASDII) is a common congenital heart defect that causes shunting of blood between the systemic and pulmonary circulations. Patients with an isolated ASDII often remain asymptomatic during childhood and adolescence. If the defect remains untreated, however, the rates of exercise intolerance, supraventricular arrhythmias, right ventricular dysfunction and pulmonary arterial hypertension (PAH) increase with patient age, and life expectancy is reduced. Transcatheter and surgical techniques both provide valid options for ASDII closure, the former being the preferred method. With the exception of those with severe and irreversible PAH, closure is beneficial to, and thus indicated in all patients with significant shunts, regardless of age and symptoms. The symptomatic and survival benefits conferred by defect closure are inversely related to patient age and the presence of PAH, supporting timely closure after diagnosis. In this paper we review the management of adult patients with an isolated ASDII, with a focus on aspects of importance to the decision regarding defect closure and medical follow-up.

Changes in mitochondrial enzymatic activities of monocytes during prolonged hypobaric hypoxia and influence of antioxidants: A randomized controlled study

OBJECTIVES

Exposure to high altitudes is associated with oxidative cellular damage due to the increased level of reactive oxygen and nitrogen species and altered activity of antioxidant systems. Subjects were submitted to prolonged hypoxia, to evaluate changes in mitochondrial enzyme activities of monocytes and their attenuation by supplementation with antioxidants.

METHODS

Twelve subjects were randomly assigned to receive antioxidant supplements or placebo prior to and during an expedition to Pik Lenin (7145 m). Monocytes were isolated from blood samples to determine the activity of mitochondrial enzymes cytochrome c oxidase and citrate synthase at 490 m (baseline) and at the altitudes of 3550 m, 4590 m, and 5530 m.

RESULTS

An increase in citrate synthase activity at all altitudes levels was observed. Hypoxia induced an increase in the activity of cytochrome c oxidase only at 4590 m. Neither citrate synthase activity nor cytochrome c oxidase activity differed between the subjects receiving antioxidant supplements and those receiving placebo.

CONCLUSIONS

Hypoxia leads to an increase in citrate synthase activity of monocyte mitochondria as a marker of mitochondrial mass, which is not modified by antioxidant supplementation. The increase in mitochondrial mass may represent a compensatory mechanism to preserve oxidative phosphorylation of monocytes at high altitudes.

Five-year lung function observations and associations with a smoking ban among healthy miners at high altitude (4000 m)

OBJECTIVE

To assess the annual lung function decline associated with the reduction of secondhand smoke exposure in a high-altitude industrial workforce.

METHODS

We performed pulmonary function tests annually among 109 high-altitude gold-mine workers over 5 years of follow-up. The first 3 years included greater likelihood of exposure to secondhand smoke exposure before the initiation of extensive smoking restrictions that came into force in the last 2 years of observation.

RESULTS

In repeated measures modeling, taking into account the time elapsed in relation to the smoking ban, there was a 115 ± 9 (standard error) mL per annum decline in lung function before the ban, but a 178 ± 20 (standard error) mL per annum increase afterward (P < 0.001, both slopes).

CONCLUSION

Institution of a workplace smoking ban at high altitude may be beneficial in terms of lung function decline.