High altitude medicine & biology最新文献

Background: Controversy remains in the association between smoking and the risk of acute mountain sickness (AMS). Therefore, a systematic review of the existing literature may help clarify this association. Methods: We conducted a systematic search of PubMed, Embase, and Cochrane Library from database inception up to October 19, 2021. Both unadjusted and adjusted relative risks (RRs) and 95% confidence intervals (CIs) were calculated to compare the risk of AMS in the smoking and nonsmoking groups. Meta-regression was conducted to explore the factors causing heterogeneity of the studies, and subsequent stratified analysis was performed to present the pooled RR in different subgroups. Publication bias was assessed using funnel plots. Results: A total of 28 eligible articles (31 studies) were included. The pooled unadjusted and adjusted RRs were 0.88 (95% CI: 0.78-1.01) and 0.87 (95% CI: 0.77-0.99), respectively, using random-effect models. Publication bias was observed owing to restrictions on the sample size. The ascending altitude and sex composition of the study population were likely sources of heterogeneity according to meta-regression. Studies on participants with an ascending altitude of over 3,500 m or composed of both males and females reported a slight but not significant protective effect of smoking on the risk of AMS, with high heterogeneity. Conclusions: Smoking had no significant effect on AMS risk in this meta-analysis. Current studies showed high heterogeneity and included little information on quantitative exposure to smoking (i.e., dose and frequency); thus, the results require careful explanation.

Wang, Bowen, Mengjia Peng,, Liheng Jiang,, Fei Fang,, Juan Wang,, Yan Li,, Ruichen Zhao,, and Yuliang Wang,. A Rare Case of High-Altitude Polycythemia Complicated by Spontaneous Splenic Rupture. High Alt Med Biol. 25:247-250, 2024.-High-altitude polycythemia, a condition characterized by an increase in red blood cellRBC mass, can occur after prolonged exposure to high altitudes. While several studies have explored the complications associated with high-altitude polycythemia, there is currently no literature available on spontaneous spleen rupture caused by high-altitude polycythemia. Here, we reported a case of acute abdominal pain and hemodynamic instability in a 36-year-old male who had been residing at high altitude for 6 years, without any recent history of trauma. Computed tomography imaging revealed significant fluid accumulation in the abdomen, and a tear of the splenic capsule was identified during the following laparotomy. Subsequent evaluations confirmed the presence of polycythemia secondary to prolonged high-altitude exposure as the underlying etiology. This case served as an important reminder that high-altitude polycythemia could lead to serious complications, such as spontaneous spleen rupture. Clinicians should be aware of this potential complication and consider it in the differential diagnosis of patients presenting with abdominal pain and hemodynamic instability in this population.

Introduction: Individuals living or working at high altitudes typically experience altered taste perceptions and reduced appetite. These changes can lead to nutritional deficiencies, affecting the energy balance and body composition. Methods: We conducted a nonsystematic review of PubMed to explore these phenomena and expound on their findings to offer additional insights. Results: Changes in taste and perception are common and typically lead to loss of mass. There are limited practical solutions to mitigate these challenges. Discussion: Gradual acclimatization and tailored nutritional strategies are required to enhance health and performance in high-altitude environments. This review provides critical insights into the intersection of altitude, nutrition, and health.

Rana, Vipin, Pradeep Kumar, Sandeepan Bandopadhyay, Vijay K. Sharma, Meenu Dangi, Dattakiran Joshi, Sanjay Kumar Mishra, Satyabrat Srikumar, and V.A. Arun. Central retinal artery occlusion in young adults at high altitude: thin air, high stakes. High Alt Med Biol. 00:000-000, 2024.-We present five cases of young security personnel who were posted at high altitude (HA) for a duration of at least 6 months and presented with a sudden decrease of vision in one eye. The diagnosis of central retinal artery occlusion (CRAO) was made in all patients. Fundus fluorescein angiography and optical coherence tomography of the macula supported the diagnosis. None of these cases had any preexisting comorbidities. Erythrocytosis was noticed in all patients, and two of them had hyperhomocysteinemia. Four out of five patients showed either middle cerebral artery or internal carotid artery (ICA) thrombosis on computed tomography angiography. The patients were managed by a team of ophthalmologist, hematologist, vascular surgeon, and neurologist. In cases of incomplete ICA occlusion, patients were managed surgically. However, in the case of complete ICA occlusion, management was conservative with antiplatelet drugs. This case series highlights HA-associated erythrocytosis and hyperhomocysteinemia as important risk factors for CRAO in young individuals stationed at HA.

Ramchandani, Rashi, Ioana Tereza Florica, Zier Zhou, Aziz Alemi, and Adrian Baranchuk. Review of athletic guidelines for high-altitude training and acclimatization. High Alt Med Biol. 00:000-000, 2024. Introduction: Exposure to high altitude results in hypobaric hypoxia with physiological acclimatization changes that are thought to influence athletic performance. This review summarizes existing literature regarding implications of high-altitude training and altitude-related guidelines from major governing bodies of sports. Methods: A nonsystematic review was performed using PubMed and OVID Medline to identify articles regarding altitude training and guidelines from international governing bodies of various sports. Sports inherently involving training or competing at high altitude were excluded. Results: Important physiological compensatory mechanisms to high-altitude environments include elevations in blood pressure, heart rate, red blood cell mass, tidal volume, and respiratory rate. These responses can have varying effects on athletic performance. Governing sport bodies have limited and differing regulations for training and competition at high altitudes with recommended acclimatization periods ranging from 3 days to 3 weeks. Discussion: Physiological changes in response to high terrestrial altitude exposure can have substantial impacts on athletic performance. Major sport governing bodies have limited regulations and recommendations regarding altitude training and competition. Existing guidelines are variable and lack substantial evidence to support recommendations. Additional studies are needed to clarify the implications of high-altitude exposure on athletic ability to optimize training and competition.

Gardner, Laurel, Linda E. Keyes, Caleb Phillips, Elan Small, Tejaswi Adhikari, Nathan Barott, Ken Zafren, Rony Maharjan, and James Marvel. Women at altitude: Menstrual-cycle phase, menopause, and exogenous progesterone are not associated with acute mountain sickness. High Alt Med Biol. 00:000-000, 2024. Background: Elevated progesterone levels in women may protect against acute mountain sickness (AMS). The impact of hormonal contraception (HC) on AMS is unknown. We examined the effect of natural and exogenous progesterone on the occurrence of AMS. Methods: We conducted a prospective observational convenience study of female trekkers in Lobuche (4,940 m) and Manang (3,519 m). We collected data on last menstrual period, use of exogenous hormones, and development of AMS. Results: There were 1,161 trekkers who met inclusion criteria, of whom 307 (26%) had AMS. There was no significant difference in occurrence of AMS between women in the follicular (28%) and the luteal (25%) phases of menstruation (p = 0.48). The proportion of premenopausal (25%) versus postmenopausal women (30%) with AMS did not differ (p = 0.33). The use of HC did not influence the occurrence of AMS (HC 23% vs. no HC 26%, p = 0.47), nor did hormonal replacement therapy (HRT) (HRT 11% vs. no HRT 31%, p = 0.13). Conclusion: We found no relationship between menstrual-cycle phase, menopausal status, or use of exogenous progesterone and the occurrence of AMS in trekkers and conclude that hormonal status is not a risk factor for AMS. Furthermore, women should not be excluded from future AMS studies based on hormonal status.

Norberto, Matheus S., João Victor G. Torini, Matheus S. Firmino, and Marcelo Papoti. Validation of air storage system for hypoxia exposure during exercise. High Alt Med Biol. 00:000-000, 2024.-Considering the importance of optimizing normobaric hypoxia exposure (i.e., higher delivery capacity), the current study aims to validate a hypoxic air storage system. The study has a cross-over, one-blind randomized design. The air storage is composed of a piping system that directs hypoxic air from a hypoxia generator into nylon bags. Sixteen men (age, 25.4 ± 4.8 years; height, 174.9 ± 9.4 cm; weight, 77.1 ± 17.2 kg) performed three incremental treadmill tests until exhaustion on different days. For test-retest, the subjects repeated two tests in similar hypoxia conditions (H1 and H2; fraction of inspired O₂ [F_IO₂] = ∼0.13; reliability analysis), and one time in normoxia (F_IO₂ = ∼0.20; condition comparison). Subjects' performance, blood lactate concentration ([La^-]), arterial oxygen saturation (SpO₂), oxygen consumption (VO₂), heart rate (HR), and several respiratory-derived variables were evaluated. A comparison was made between the rest, moderate intensity, and exhaustion stages. All variables were compared using the Friedman test with Durbin-Conover post hoc (p < 0.05). The hypoxia test-retest showed no statistical differences for any variable. Time analysis showed similar behavior for SpO₂, HR, and cardiorespiratory variables (p < 0.01) for both conditions. The mean F_IO₂ at rest and during the incremental treadmill test was higher for normoxia (20.6 ± 0.2%) than for H1 (13.8 ± 0.8%) and H2 (13.7 ± 0.3%) (p < 0.001). The VO₂ response was higher in normoxia than during hypoxia exposure at moderate intensity (Normoxia = 43.1 ± 8.1; H1 = 38.7 ± 5.7; H2 = 35.8 ± 8.8 ml.kg^-1.min^-1) and at the exhaustion stage (Normoxia = 52.7 ± 12.5; H1 = 41.9 ± 8.8; H2 = 40.5 ± 8.9 ml.kg^-1.min^-1) (p < 0.01). SpO₂ and HR showed excellent intraclass correlation coefficient (ICC) during all moments, whereas VO₂, SpO₂, ratio between ventilation and CO₂ production (V_E/V_CO2), ratio between oxygen consumption and ventilation (V_E/V_O2), and HR showed moderate or good ICC and coefficient of variation <9% during hypoxia test-retest exercises. Thus, the air storage system showed validity for its application and reliability in the measurements associated.

Lin, Tian, Huaping Jia, Yunming Li, Yongxing Xu, Bei Zhao, Dong Zheng, Hongfeng Yan, Meihui Zhao, Yanlei Li, Liping Xia, Fengxia Zhou, Cuiping Liu, Ke Ma, Ma Mi, and Jianwen Gu. Epidemiological survey of congenital heart disease among children aged from 2 to 18 in Suo County, Nagqu, Tibet. High Alt Med Biol. 00:000-000, 2024. Background: Studies have reported the prevalence of congenital heart disease (CHD) in parts of Tibet, but relative epidemiological surveys are rare. We aimed to explore the prevalence of CHD in children and its relationship with family history in Suo County, Nagqu, Tibet, an altitude of 3,980 meters. Methods: We recruited 4,002 children aged 2-18 years. Subjects underwent a family history investigation, cardiac auscultation, and clinical manifestation examination and then received echocardiographic screening. Results: The prevalence of CHD among children in Suo County was 0.97% (39 cases), much higher than the prevalence at sea level. The most common subtype was atrial septal defect, accounting for 53.9% of CHD, followed by patent ductus arteriosus (33.3%) and ventricular septal defect (12.8%). We also found that children whose mothers had previously borne children with CHD had a higher risk of CHD than those without (p = 0.002); other factors related to CHD during pregnancy, such as smoking, drinking, drug use, and viral infection, showed no statistical differences between children with and without CHD. Conclusions: The prevalence of CHD in children in Suo County is much higher than at low altitude, consisting mostly of simple forms with left-to-right shunt, with rare complex CHD. These results support implementing diagnostic and treatment plans to prevent CHD in Suo County.