Understanding Acute Respiratory Distress Syndrome in High-Altitude Environments: A Comprehensive Review of Diagnosis and Treatment.

Approximately 2% of the global population lives above 1500 m, where low atmospheric pressure, decreased oxygen levels, harsh cold and dry conditions, strong radiation, and the effects of climate change present significant health challenges. Residents of these high-altitude areas display physiological adaptions, including smaller body size, enlarged ribs, improved oxygen delivery in hypoxic conditions, and adjustments in oxygen utilization and metabolism. Both acute and chronic hypoxia prevalent in such regions can trigger various diseases by stimulating hypoxia-inducible factors, boosting inflammatory responses, and impairing mitochondrial function.Acute Respiratory Distress Syndrome (ARDS) - a critical respiratory condition associated with high morbidity and mortality - occurs more frequently among the health risks in these environments. Hypoxia is a critical predisposing and aggravating factor for high-altitude ARDS. Despite similarities with its low-altitude counterpart, ARDS in high-altitude areas displays unique pathophysiology and clinical manifestations due to the specific environmental conditions.This review aims to shed light on how high-altitude environments influence the diagnosis and treatment of ARDS, providing a comprehensive understanding of the distinct challenges inherent to these regions.

[Microcirculation characteristics and humoral factors of healthy people from different populations at high altitude (4 100 m)].

The present study was aimed to observe the characteristics of sublingual microcirculation and the changes of humoral factors in healthy people of three different high altitude populations. Three groups of healthy subjects in Guoluo area of Qinghai province (4 100 m) were included: Tibetan group: 30 Tibetans, (45.62 ± 10.15) years old; Han group: 22 two-generation of Han immigrants, (46.23 ± 8.59) years old; migrant group: 23 migrants living at high altitude for 2-5 years, (43.45 ± 8.31) years old. Blood routine test was performed to determine white blood cell (WBC) count, red blood cell (RBC) count, hemoglobin (HGB), hematocrit (HCT), platelet (PLT) count, and neutrophil (NEUT) count. The changes of serum humoral factors including endothelin-1 (ET-1), CD31, CD34, CD105, vascular endothelial growth factor (VEGF), nitric oxide (NO) and noradrenaline (NE) were detected by ELISA. Continuous noninvasive hemodynamics monitor was used to continuously measure the changes of systemic circulation indexes: cardiac output (CO), cardiac index (CI), heart rate (HR), stroke volume (SV), pulse pressure variation (PPV), systemic vascular resistance index (SVRI), and mean arterial pressure (MAP). Blood oxygen was measured by pulse oximeter. Sublingual microcirculation indexes including total vascular density (TVD), perfused vessel density (PVD), proportion of perfused vessels (PPV), and microvascular flow index (MFI) were determined by sidestream dark field imaging. The results showed that there were no difference in systemic circulation among the 3 groups. Compared with Tibetan group, TVD and PVD of microcirculation in Han group and migrant group were significantly increased (P < 0.05). Compared with Tibetan group and Han group, WBC, RBC, HGB and HCT of migrant group were significantly increased (P < 0.05). Compared with Han group and Migrant group, PLT of Tibetan group was significantly increased (P < 0.05). Compared with the Tibetan group, the levels of serum humoral factors CD105 and VEGF were significantly higher in the migrant group (P < 0.05), while compared with Han and migration groups, NO in Tibetan group was significantly increased (P < 0.05). It is suggested that there were significant differences in microcirculation (TVD, PVD), blood routine (WBC, RBC, HGB, HCT) and humoral factors (CD105, VEGF) among different populations in high altitude area. Importantly, the increased microcirculation, erythrocytosis and increased pro-angiogenic factors due to hypoxic environment were observed in long-term residents and migrants, except for permanent residents. These physiological changes have clinical significance in the treatment of septic shock and chronic altitude sickness for different plateau populations.

Dynamic changes in peripheral blood-targeted miRNA expression profiles in patients with severe traumatic brain injury at high altitude.

BACKGROUND: The aim of this work is to detect and compare the peripheral blood miRNA expression profiles in patients with severe traumatic brain injury (sTBI) 2, 12, 24, 48, and 72 h after injury at high altitude and to predict the target genes of differential expressed miRNAs. METHODS: Twenty sTBI patients from high-altitude areas were randomly selected according to the inclusion and exclusion criteria and were divided into five groups: the 2-h group, 12-h group, 24-h group, 48-h group, and 72-h group. Peripheral blood miRNA expression profiles were detected using real-time quantitative PCR (qRT-PCR). RESULTS: The expression levels of miR-18a, miR-203, miR-146a, miR-149, miR-23b, and miR-let-7b in peripheral blood showed significant differences between the 2-h group and the 12-h group. The expression levels of miR-203, miR-146a, miR-149, miR-23b, and miR-let-7f in peripheral blood were up-regulated in the 24-h group. In the 48-h group, the expression levels of miR-181d, miR-29a, and miR-18b were upregulated. In the 72-h group, the expression levels of miR-203, miR-146a, miR-149, miR-23b, and miR-let-7f changed. The main target genes of the differentiation expressed miRNAs were genes that regulate inflammatory responses, apoptosis, and DNA damage/repair. CONCLUSIONS: miRNAs may be involved in the pathogenesis of sTBI by dynamically regulating the target genes that regulate inflammatory responses, apoptosis, and DNA damage/repair pathways.

[Effects of early mechanical ventilation on oxygenation and hemodynamics in acute high altitude pulmonary edema patients complicated by acute respiratory distress syndrome].

OBJECTIVE: To investigate the effect of early mechanical ventilation on oxygenation and hemodynamic of acute high altitude pulmonary edema (HAPE) patients complicated by acute respiratory distress syndrome (ARDS). METHODS: From May 2001 to December 2006, 8 HAPE patients with secondary ARDS admitted to Germud City People's Hospital were enrolled in the study. All the patients received early invasive mechanical ventilation within 24 hours of HAPE. Hemodynamics, cardiac output, arterial and mixed venous blood gas and oxygen dynamics parameters were determined before and after 96 hours of mechanical ventilation. RESULTS: Before treatment the right atrial pressure (RAP), mean pulmonary artery pressure (mPAP), pulmonary vascular resistance index (PVRI) and shunt (Qs/Qt) were above normal values. Oxygen delivery (DO2), oxygen extraction rate (O2ER), and oxygenation index (PaO2/FiO2) were lower than normal values. After treatment with mechanical ventilation, arterial partial pressure of oxygen (PaO2), PaO2/FiO2, arterial oxygen saturation (SaO2), partial pressure of oxygen of mixed venous blood (PVO2) and mixed venous oxygen saturation (SVO2) were increased significantly compared with those before treatment [PaO2: 70.3±2.9 mm Hg (1 mm Hg=0.133 kPa) vs. 49.9±3.5 mm Hg, t=15.292, P=0.001; PaO2/FiO2: 201.6 ± 4.8 mm Hg vs. 134.5±5.2 mm Hg, t=19.618, P=0.004; SaO2: 0.929±0.021 vs. 0.780±0.073, t=6.226, P=0.002; PVO2: 54.8±2.9 mm Hg vs. 44.9±2.6 mm Hg, t=6.767, P=0.002; SVO2: 0.726±0.017 vs. 0.663±0.053, t=3.262, P=0.008]. Heart rate (HR), RAP, mPAP, pulmonary wedge pressure (PAWP), PVRI, right ventricular stroke work index (RVSWI) and Qs/Qt were decreased significantly compared with those before mechanical ventilation [HR: 73±2 bpm vs. 102±13 bpm, t=6.228, P=0.000; RAP: 6.9±1.0 mm Hg vs. 13.9±1.5 mm Hg, t=3.609, P=0.008; mPAP: 18.5±2.9 mm Hg vs. 41.6±3.0 mm Hg, t=4.773, P=0.000; PAWP: 6.9±2.2 mm Hg vs. 14.0±4.2 mm Hg, t=2.747, P=0.030; PVRI: 26.3±1.7 kPa×s×L(-1) vs. 49.6±10.0 kPa×s×L(-1), t=9.861, P=0.000; RVSWI: 11.0±1.9 g×cm(-1)×min×m(2) vs. 22.0±1.5 g×cm(-1)×min×m(2), t=12.704, P=0.000; Qs/Qt: (26±18)% vs. (35±15)%, t=7.603, P=0.000], and cardiac index (CI), DO2, oxygen consumption (VO2) and O2ER were also increased [CI: 71.68±6.67 mL×s(-1)×m(-2) vs. 70.01±6.67 mL×s(-1)×m(-2), t=2.832, P=0.036; DO2 (L×min(-1)×m(-2)): 460.9±14.0 vs. 410.0±3.1, t=9.268, P=0.000; VO2 (L×min(-1)×m(-2)): 158.5±9.2 vs. 129.9±5.3, t=2.818, P=0.004; O2ER: (20±1)% vs. (18±1)%, t=7.652, P=0.000]. All of the 8 patients survived. CONCLUSIONS: Pulmonary circulation hemodynamic and oxygen dynamic disorders were found in HAPE patients with secondary ARDS. Treatment with early mechanical ventilation not only improved oxygenation but also reduced pulmonary hypertension and increased cardiac output and DO2.