High-altitude pulmonary edema: diagnosis, prevention, and treatment

Identification of potential biomarkers and pathways involved in high-altitude pulmonary edema using GC-MS and LC-MS metabolomic methods

High-altitude pulmonary edema (HAPE) is a life-threatening altitude sickness afflicting certain individuals after rapid ascent to high altitude above 2500 m. In the setting of HAPE, an early diagnosis is critical and currently based on clinical evaluation. The aim of this study was to utilize the metabolomics to identify the altered metabolic patterns and potential biomarkers for HAPE. Serum samples from HAPE patients (n = 24) and healthy controls (n = 21) were analyzed by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS) to profile differential metabolites and explore dysregulated metabolic pathways. The correlation analysis and receiver operating characteristic (ROC) curve analysis were further performed to screen biomarkers for HAPE. A total of 119 differential metabolites between the control and HAPE groups were identified. Top dysregulated pathways included pyrimidine metabolism, citrate cycle, sulfur metabolism, phenylalanine metabolism and purine metabolism. After correlation analysis with clinical indices, 39 differential metabolites were obtained as potential biomarkers related to HAPE. Finally, 7 biomarkers, specifically S-nitroso-N-acetylcysteine, aminocaproic acid, emodin, threo-hydroxyaspartic acid, 6-hydroxynicotinic acid, 3-acetylphenol sulfate and cis-aconitic acid, were screened out through ROC analysis, which displayed high diagnostic accuracy for HAPE. Taken together, the altered serum metabolic profile is associated with the occurrence of HAPE. Diagnostic tests based on the biomarkers from metabolomics may hold promise as a strategy for early detection of HAPE.

Decoding the Immune Response and Its Biomarker B2M for High Altitude Pulmonary Edema in Rat: Implications for Diagnosis and Prognosis

Purpose

We aimed to investigate whether peripheral blood biomarkers B2M related to immune response can serve as indicators of HAPE pathophysiological characteristics or disease progression.

Patients and Methods

Bioinformatics technology was used to explore the peripheral blood pathophysiological mechanisms and immune hub genes related to the occurrence of HAPE. The hub gene was verified through animal experiments, and its function and correlation between its expression level and the diagnosis, treatment effect and prognosis of HAPE were explored.

Results

The GSVA results showed that the occurrence of HAPE was related to the down-regulation of immune response pathways by RUNX3 and STING. WGCNA results showed that the peripheral blood immune gene module related to the development of HAPE was related to the decrease of immune function and the increase of immune checkpoint molecule PD-L1 gene expression, and the expression of immune checkpoint genes LILRB2 and SIGLEC15 increased. Cytoscape software, RT-qPCR and WB confirmed that the hub gene B2M is a specific peripheral blood biomarker of HAPE. ROC, DCA, RT-qPCR, HE and Masson results showed that the expression of peripheral blood B2M has the ability to indicate the diagnosis, treatment effect and prognosis of HAPE. The decreased expression of B2M protein in peripheral blood leukocytes may be a marker of HAPE. Single-gene GSEA confirmed that the reduced expression of B2M in peripheral blood may be involved in the down-regulation of the antigen presentation pathway mediated by MHC class I molecules, was positively correlated with the down-regulation of the TNF signaling pathway, and was negatively correlated with the expression of LILRB2 and SIGLEC15.

Conclusion

The occurrence of HAPE may be related to decreased immune function and immune tolerance. Peripheral blood B2M may be involved in the related pathways, its expression level can prompt the diagnosis, treatment and prognosis of HAPE.

Unilateral Left-Sided High-Altitude Pulmonary Edema Following Rapid Ascent to a City in the Himalayas

High-altitude pulmonary edema (HAPE) is a medical emergency commonly observed in people ascending to altitudes above 9000 ft. The condition predominantly presents with bilateral clinical and radiological findings. In rare cases, where unilateral lung involvement is seen, a right lung predilection is usually noted. We present a case of HAPE with unilateral left lung involvement in a young man upon reintroduction to a high-altitude area. He presented with dyspnea at rest and was found to have severe hypoxemia and tachycardia. Clinical and radiological evidence showed unilateral left lung findings. After excluding other plausible causes, it was concluded to be a case of HAPE. Following treatment, his symptoms resolved, and he was discharged on the fifth day after admission. This case highlights the necessity of awareness related to the uncommon presentations of HAPE since this condition can be completely reversed with a good patient outcome if suspected and treated early.

NGCN: Drug-target interaction prediction by integrating information and feature learning from heterogeneous network

Drug-target interaction (DTI) prediction is essential for new drug design and development. Constructing heterogeneous network based on diverse information about drugs, proteins and diseases provides new opportunities for DTI prediction. However, the inherent complexity, high dimensionality and noise of such a network prevent us from taking full advantage of these network characteristics. This article proposes a novel method, NGCN, to predict drug-target interactions from an integrated heterogeneous network, from which to extract relevant biological properties and association information while maintaining the topology information. It focuses on learning the topology representation of drugs and targets to improve the performance of DTI prediction. Unlike traditional methods, it focuses on learning the low-dimensional topology representation of drugs and targets via graph-based convolutional neural network. NGCN achieves substantial performance improvements over other state-of-the-art methods, such as a nearly 1.0% increase in AUPR value. Moreover, we verify the robustness of NGCN through benchmark tests, and the experimental results demonstrate it is an extensible framework capable of combining heterogeneous information for DTI prediction.

Clinical characteristics of venous thromboembolism onset from severe high altitude pulmonary edema in plateau regions

BACKGROUND

To investigate venous thromboembolism (VTE) in hospitalized patients with severe high altitude pulmonary edema (HAPE), we performed a single center retrospective study to evaluate its clinical characteristics, prognosis, and potential thromboprophylaxis strategies in a large referral and treatment center in plateau regions.

METHODS

We studied a total of 18 patients with severe HAPE from January 1, 2012 to December 31, 2021. Demographic and clinical data, laboratory data, including ultrasound scans of the lower extremities and cardiac ultrasound, and computed tomographic pulmonary angiography (CTPA) variables were obtained, and comparisons were made between groups with and without VTE.

RESULTS

Of the 18 patients hospitalized with severe HAPE (age 43 (range, 34-54) years, 14 [77.8%] men), 7 patients developed VTE (38.9%), including 5 with deep vein thrombosis (DVT) and pulmonary embolism (PE), 2 of whom had DVT only. Eighteen patients are all firstly rapid ascent to high altitudes which the mean altitude was 3700 m (3656-4050 m). Compared with patients who did not have VTE, patients with VTE had a longer time in hospital (13 [11, 19] versus 9 [7, 12]; P = 0.027), respiratory failure (6 [85.7%] versus 2 [18.2%]; P = 0.013), the shortened APTT (21.50 [19.00, 27.50] versus 26.30 [24.80, 30.10]; P = 0.044) and the higher level of D-dimer (7.81 [4.62, 9.60] versus 2.90 [1.75, 3.37]; P = 0.003). The proportion of thromboprophylaxis is too low in our cohort which 2 of 18 (11.1%) patients were given VTE prophylaxis. There was no statistically significant difference between the VTE and non-VTE groups (0 [0.0%] versus 2 [18.2%]; P = 0.497).

CONCLUSIONS

The prevalence of VTE is high in hospitalized patients with severe high altitude pulmonary edema (HAPE). Prophylaxis for venous thromboembolism may be protective in severe HAPE patients after admission. Our data seem to suggest that VTE is probably an additional prognostic factors in patients with severe HAPE.

Suggestive evidence of CYP4F2 gene polymorphisms with HAPE susceptibility in the Chinese Han population

High altitude pulmonary edema (HAPE) is a common respiratory disease in the high altitude area, which is rapid and harmful. We firstly conducted a case-control study to assess the potential association of CYP4F2 gene polymorphisms with HAPE susceptibility in the Chinese Han population. The study recruited 238 patients with HAPE and 230 healthy controls in Northwest China. Genomic DNA was extracted from blood samples, and gene polymorphisms were detected using the Agena MassARRAY platform. Odds ratios (ORs), 95% confidence intervals (95% CIs), and P-value were used to evaluate the relationship between HAPE risk and CYP4F2 gene polymorphisms. Multi-factor dimension reduction (MDR) was used to assess the optimal interaction of CYP4F2 gene polymorphisms on HAPE risk. We found rs3093193 was shown to reduce the risk of HAPE (OR = 0.70, 95% CI = 0.52-0.93, P = 0.014), while rs12459936 was increased the susceptibility to HAPE (OR = 2.08, 95% CI = 1.33-3.26, P = 0.001). Age stratified analysis revealed that rs3093193 and rs12459936 were correlated with HAPE risk in people at age > 32 years old, and rs3093193 and rs3093110 were correlated with the HAPE risk in people at age ≤ 32 years old. Gender stratification analysis was found that rs3093193, rs12459936, and rs3093110 were all related to HAPE risk in males. A combination of rs12459936 and rs3093110 was the best multi-loci model with the highest testing accuracy. Our study is the first to provide the association between CYP4F2 gene polymorphisms and HAPE risk in the Chinese Han population.

Respiratory responses to hypoxia during rest and exercise in individuals born pre-term: a state-of-the-art review

The pre-term birth survival rate has increased considerably in recent decades, and research investigating the long-term effects of premature birth is growing. Moreover, altitude sojourns are increasing in popularity and are often accompanied by various levels of physical activity. Individuals born pre-term appear to exhibit altered acute ventilatory responses to hypoxia, potentially predisposing them to high-altitude illness. These impairments are likely due to the use of perinatal hyperoxia stunting the maturation of carotid body chemoreceptors, but may also be attributed to limited lung diffusion capacity and/or gas exchange inefficiency. Aerobic exercise capacity also appears to be reduced in this population. This may relate to the aforementioned respiratory impairments, or could be due to physiological limitations in pulmonary blood flow or at the exercising muscle (e.g. mitochondrial efficiency). However, surprisingly, the debilitative effects of exercise when performed at altitude do not seem to be exacerbated by premature birth. In fact, it is reasonable to speculate that pre-term birth could protect against the consequences of exercise combined with hypoxia. The mechanisms that underlie this assertion might relate to differences in oxidative stress responses or in cardiopulmonary morphology in pre-term individuals, compared to their full-term counterparts. Further research is required to elucidate the independent effects of neonatal treatment, sex differences and chronic lung disease, and to establish causality in some of the proposed mechanisms that could underlie the differences discussed throughout this review. A more in-depth understanding of the acclimatisation responses to chronic altitude exposures would also help to inform appropriate interventions in this clinical population.

Radiographical Spectrum of High-altitude Pulmonary Edema: A Pictorial Essay

Background

High-altitude pulmonary edema (HAPE) is a common cause of hospitalization in high altitude areas with significant morbidity. The clinical presentation of HAPE can overlap with a broad spectrum of cardiopulmonary diseases. Also, it is associated with varied radiological manifestations mimicking other conditions and often leading to unnecessary and inappropriate treatment.

Patients and methods

The primary aim of the study was to study the various radiological manifestations of HAPE through real-world chest radiographs. We present six different chest X-ray patterns of HAPE as a pictorial assay, at initial presentation, and after the resolution of symptoms with supplemental oxygen therapy and bed rest alone.

Results

HAPE can present as bilateral symmetrical perihilar opacities, bilateral symmetrical diffuse opacities, unilateral diffuse opacities, bilateral asymmetrical focal opacities, and even lobar consolidation with lower zone or less commonly upper zonal predilection. These presentations can mimic many common conditions like heart failure, acute respiratory distress syndrome, pulmonary embolism, aspiration pneumonitis, pneumonia, malignancy, and tuberculosis.

Conclusion

A holistic clinical–radiological correlation coupled with analysis of the temporal course can help high-altitude physicians in differentiating true HAPE from its mimics.

How to cite this article

Yanamandra U, Vardhan V, Saxena P, Singh P, Gupta A, Mulajkar D, et al. Radiographical Spectrum of High-altitude Pulmonary Edema: A Pictorial Essay. Indian J Crit Care Med 2021;25(6):668–674.

The Complexity of Diagnosing High-Altitude Pulmonary Edema: A Case Report and Review of the Differential Diagnosis of Greater Than Expected Hypoxemia at Altitude

High-altitude pulmonary edema (HAPE) is a common presumptive diagnosis for a patient who experiences significant dyspnea and cyanosis at altitude. In this study, we present a case of a 58-year-old woman who was initially diagnosed with HAPE, although further evaluation revealed the presence of two underlying contributors to her significant hypoxemia at altitude. We discuss the medical workup for causes of greater than expected hypoxemia at altitude and the role some relevant medical comorbidities may play.

Diagnosis and prophylaxis for high-altitude acclimatization: Adherence to molecular rationale to evade high-altitude illnesses

Lack of zero side-effect, prescription-less prophylactics and diagnostic markers of acclimatization status lead to many suffering from high altitude illnesses. Although not fully translated to the clinical setting, many strategies and interventions are being developed that are aimed at providing an objective and tangible answer regarding the acclimatization status of an individual as well as zero side-effect prophylaxis that is cost-effective and does not require medical supervision. This short review brings together the twin problems associated with high-altitude acclimatization, i.e. acclimatization status and zero side-effect, easy-to-use prophylaxis, for the reader to comprehend as cogs of the same phenomenon. We describe current research aimed at preventing all the high-altitude illnesses by considering them an assault on redox and energy homeostasis at the molecular level. This review also entails some proteins capable of diagnosing either acclimatization or high-altitude illnesses. The future strategies based on bioinformatics and systems biology is also discussed.

Telomere length-related gene ACYP2 polymorphism is associated with the risk of HAPE in Chinese Han population

BACKGROUND

High altitude pulmonary edema (HAPE) is a type of pneumonedema that mostly occurs under conditions such as high altitude, rapid ascent and hypoxia, amongst others. The ACYP2 polymorphism is suggested to be associated with mean telomere length, and telomere length is significantly longer at a moderate attitude than at sea-level or at simulated high attitude. The present study aimed to determine whethher there is any association between ACYP2 polymorphism and the risk of HAPE.

METHODS

A total of 265 patients and 303 healthy controls were enrolled in our case-control study. Six SNPs were selected and genotyped using the Sequenom MassARRAY method. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated by unconditional logistic regression with adjustment for gender and age.

RESULTS

Using chi-squared tests, we found that the minor allele G of rs11896604 is significantly associated with a decreased risk of HAPE [odds ratio (OR) = 0.87, 95% confidence interval (CI) = 0.65-1.16, p = 0.048]. We also found that the 'A/A' genotype of rs12615793 is associated with a decreased risk of HAPE based on the recessive model (OR =0.28; 95% CI = 0.09-0.88; p = 0.017). Additionally, the 'G/G' genotype of rs11896604 was found to be associated with a decreased risk of HAPE based on the codominant model (OR =0.26; 95% CI = 0.08-0.79; p = 0.025) and recessive model (OR =0.25; 95% CI = 0.08-0.77; p = 0.007). However, only rs11896604 remained significant after Bonferroni correction (p < 0.0083).

CONCLUSIONS

The present study found that the ACYP2 gene polymorphism significantly decreased the risk of HAPE. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

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.

Hematological Risk Factors for High-Altitude Headache in Chinese Men Following Acute Exposure at 3,700 m

Background: High-altitude headache (HAH) is a notably common disorder affecting the daily life of travelers ascending to high altitude. Hematological parameters are important clinical examinations for various diseases. Today, hematological characteristics of HAH remain unrevealed. Above all, we aimed to ascertain hematological characteristics and independent risk factors/predictors associated with HAH before and after exposure at 3,700 m.

Methods: Forty five healthy men were enrolled in present study. Demographic and clinical data, physiological and hematological parameters were collected 3 days before the ascent and after acute exposure at 3,700 m.

Results: HAH patients featured significantly lower white blood cell count (WBC), neutrophil count (NEU#) and percentage (NEU%), and higher percentage of lymphocyte (LYM%) at 3,700 m and significantly lower NEU#, reticulocyte count (RET#) and percentage (RET%) at sea level (all P < 0.05). HAH severity was significantly and negatively associated with WBC, NEU#, and NEU% at 3,700 m and RET# at sea level, whereas was positively associated with LYM% at 3,700 m (all P < 0.05). Moreover, we have found that RET# at sea level and NEU% at 3,700 m was an independent predictor and risk factor for HAH, respectively.

Conclusion: The present study is the first to examine the hematological characteristics of HAH. Furthermore, lower RET# at sea level and lower NEU% at 3,700 m is a novel independent predictor and risk factor for HAH, respectively.

Association between regulator of telomere elongation helicase1 (RTEL1) gene and HAPE risk: A case-control study

High altitude pulmonary edema (HAPE) is a paradigm of pulmonary edema. Mutations in regulator of telomere elongation helicase1 (RTEL1) represent an important contributor to risk for pulmonary fibrosis. However, little information is found about the association between RTEL1 and HAPE risk. The present study was undertaken to tentatively explore the potential relation between single-nucleotide polymorphisms (SNPs) in RTEL1 and HAPE risk in Chinese Han population. A total of 265 HAPE patients and 303 healthy controls were included in our case-control study. Four SNPs in RTEL1 were selected and genotyped using the Sequenom MassARRAY method. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated by unconditional logistic regression with adjustment for gender and age. All P values were Bonferroni corrected, and statistical significance was set at P < .0025 (.05/20). In allelic model analysis, we found that the allele "G" of rs6089953 and rs6010621 and the allele "A" of rs2297441 were associated with decreased risk of HAPE. In the genetic model analysis, we found that rs6010621, rs6089953, and rs2297441 were relevant to decreased HAPE risk under dominant model (rs6010621: OR = 0.55; 95% CI = 0.39-0.78; P = .001; rs6089953: OR = 0.68; 95% CI = 0.48-0.96; P = .027; rs2297441: OR = 0.63; 95% CI = 0.45-0.89; P = .008, respectively) and additive model (rs6010621: OR = 0.51; 95% CI = 0.46-0.81; P < .001; rs6089953: OR = 0.72; 95% CI = 0.55-0.95; P = .022; rs2297441: OR = 0.73; 95% CI = 0.57-0.95; P = .019, respectively). SNPs rs6010621 remained significant after Bonferroni correction (P < .0025). In addition, haplotype "GG, GT, AT" of rs6089953-rs6010621 were detected significantly associated with HAPE risk (P < .05), haplotype "GG" remained significant after Bonferroni correction (P < .0025). Our findings provide new evidence for the association between SNPs in RTEL1 and a decreased risk HAPE in the Chinese population. The results need further confirmation.

A Signature of Circulating microRNAs Predicts the Susceptibility of Acute Mountain Sickness

Background: Acute mountain sickness (AMS) is a common disabling condition in individuals experiencing high altitudes, which may progress to life-threatening high altitude cerebral edema. Today, no established biomarkers are available for prediction the susceptibility of AMS. MicroRNAs emerge as promising sensitive and specific biomarkers for a variety of diseases. Thus, we sought to identify circulating microRNAs suitable for prediction the susceptible of AMS before exposure to high altitude.

Methods: We enrolled 109 healthy man adults and collected blood samples before their exposure to high altitude. Then we took them to an elevation of 3648 m for 5 days. Circulating microRNAs expression was measured by microarray and quantitative reverse-transcription polymerase chain reaction (qRT-PCR). AMS was defined as Lake Louise score ≥3 and headache using Lake Louise Acute Mountain Sickness Scoring System.

Results: A total of 31 microRNAs were differentially expressed between AMS and Non-AMS groups, 15 up-regulated and 16 down-regulated. Up-regulation of miR-369-3p, miR-449b-3p, miR-136-3p, and miR-4791 in patients with AMS compared with Non-AMS individuals were quantitatively confirmed using qRT-PCR (all, P < 0.001). With multiple logistic regression analysis, a unique signature encompassing miR-369-3p, miR-449b-3p, and miR-136-3p discriminate AMS from Non-AMS (area under the curve 0.986, 95%CI 0.970–1.000, P < 0.001, LR+: 14.21, LR–: 0.08). This signature yielded a 92.68% sensitivity and a 93.48% specificity for AMS vs. Non-AMS.

Conclusion: The study here, for the first time, describes a signature of three circulating microRNAs as a robust biomarker to predict the susceptibility of AMS before exposure to high altitude.

Three plasma metabolite signatures for diagnosing high altitude pulmonary edema

High-altitude pulmonary edema (HAPE) is a potentially fatal condition, occurring at altitudes greater than 3,000 m and affecting rapidly ascending, non-acclimatized healthy individuals. However, the lack of biomarkers for this disease still constitutes a bottleneck in the clinical diagnosis. Here, ultra-high performance liquid chromatography coupled with Q-TOF mass spectrometry was applied to study plasma metabolite profiling from 57 HAPE and 57 control subjects. 14 differential plasma metabolites responsible for the discrimination between the two groups from discovery set (35 HAPE subjects and 35 healthy controls) were identified. Furthermore, 3 of the 14 metabolites (C8-ceramide, sphingosine and glutamine) were selected as candidate diagnostic biomarkers for HAPE using metabolic pathway impact analysis. The feasibility of using the combination of these three biomarkers for HAPE was evaluated, where the area under the receiver operating characteristic curve (AUC) was 0.981 and 0.942 in the discovery set and the validation set (22 HAPE subjects and 22 healthy controls), respectively. Taken together, these results suggested that this composite plasma metabolite signature may be used in HAPE diagnosis, especially after further investigation and verification with larger samples.